I thought this would be a more direct test to demonstrate what these damping materials do inside a speaker box. It shows the effect the stuffing has on the sound waves coming from the speaker before they hit the bowl and make that vibrate, and it also shows how effective it is at shortening the "ring time" of the bowl itself. And of course the sound can and will go around the stuffing on its way to the bowl, but I thought this would give a relatively good approximation of the damping power of the sound waves by the damping material only. Some will say that a bowl isn't a speaker box, but they are not at all dissimilar. The box will "ring" in the same way, just at a different frequency and amplitude depending upon the stiffness and self-damping properties of the wood used to construct the box. The bowl just gives a more dramatic demonstration. It's worth pointing out that these tests that I'm doing are not to give this problem more weight than it it deserves. In most regards, box vibration and the sound that comes from it isn't a problem at all, since it will be so far below the speaker output that you won't be able to detect it. It's only when (in my opinion and experience) the panels get to be very large and unbraced and undamped that they can put out enough sound energy to be heard. When building speakers there's ALWAYS a tradeoff. And in my opinion the best approach is to concentrate on the factors that will make the most difference first, and not get bogged down fretting over box material or stuffing / damping. These factors are very low in the overall design as far as ultimate sound quality is concerned. Knowing this will better equip you to make the important tradeoffs to get the results you are looking for.
Hopefully your guidance will resonate with listeners/viewers and they will learn enough to get on with their project, get it done and enjoy it. A finished project sounds better than a work-in-progress! Great, simple demo to illustrate what the effects are.
Great demonstration to really hammer home what using damping can do for a speaker. Really interested in trying out the rockwool/fiberglass combo (especially seeing as I have a bunch of trimmings kicking around from having rebuilt an exterior wall and roof). I just built a pair of 2 ways with a passive radiator design to go out on my patio in the summer, going to get them outside to take some measurements soon as I don't have a decent indoor listening space. Loving the repurposing of this channel, and as always the content on the main channel! Thanks for all the work you put in John!
For international customers, to keep shipping costs down, we sometimes recommend a combination of heavy vinyl floor tiles or a butyl dampener and fiberglass/rockwool insulation instead of Norez. It's a lot more readily available and usually saves 40-50% on international shipping costs, and has the exact same effect.
I agree with these results, because I've done these same kinds of tests myself, but not with as much "tech" as you have there. I really WISH I had the programs, computer, mics, etc. that you used to show these graphs... in less than a second for each one, which is amazing, plus the ability to instantly then A/B compare the graphs on the computer screen, now THAT is an awesome program and setup there! I love it! The ONLY pieces of equipment I have is an old fashioned analog/manual knob frequency generator that I obtained for free many years ago, an old Radio Shack analog SPL meter that someone gave me, and my multimeter that I've had since high scool days, along with my very good ears of course, which I have taken very good care of over the years, because I love sound, speaker building, and music so much, so when I came up with these same results it was from my many HOURS of meticulous measuring and careful listening to different frequencies and materials, but so I could do SO MUCH MORE, and MUCH faster and easier, if I was able to afford to buy all of this high tech equipment you have! Wow! I also would love to have an oscilloscope, but I don't have one because I can't afford one, not even a used one... Anyway, getting off topic slightly there, but I agree that the "Polyfil" stuffing is all but worthless in speakers as damping material, especially with the pitiful, "wispy" amounts of it that most speaker manufacturers put inside their speakers from the factory, (if they even bother with damping material at all), so when I see a speaker company's rather lame and useless attempt at damping like that I just laugh. And the ones that actually DO use it, definitely DON'T use enough of it to even have any positive effect! I always just take that tiny piece of polyfil stuff out and line the box with something better... almost anything else works better than that stuff does, lol!... One thing that I will say about fiberglass though is that it's of course a pain to work with because it gets all over in the air and makes you cough and itch, which I really HATE, so then I tried the Rockwool stuff too, and the main problem I've found with that, in addition to the same problems fiberglass has with being extremely messy and irritating to work with, is that Rockwool is also damaging to any drivers that have a vented voice coil, because the sharp and considerably abrasive and heavy particles of it, kind of like an extremely fine sand, will eventually get inside the driver voicecoil and former itself and then start to cause rubbing and scratching of the enamel on the relatively tiny voicecoil wire, which of course is very bad for the driver itself, basically rendering it useless!... With all of that being said however, and if you don't mind the mess and skin and lung irritation, both fiberglass and rockwool ARE effective and acceptable to use with sealed back drivers, (i.e. NON-vented voicecoil ones), especially since both of those materials are also reasonably easy to obtain and cheap, like at your local home center, hardware store, etc... However, I have finally found in recent years an even better, seemingly even more effective, definitely much easier to work with, totally non-damaging, and, most importantly, usually totally FREE material to use for very effectively damping speaker boxes with... You can usually find it in recycle dumpsters inside shipping boxes for various lightweight and/or delicate products... It is the batting that is made out of recycled clothing and textiles, (i.e. the ground up "blue jean" type insulation batts), and I have found that this type of insulation is quite readily available in your public neighborhood recycling facility dumpsters because it is used for padding and shipping so many things nowadays because it's "environmentally friendly". When/if you look for that stuff, it is sometimes wrapped with an outer plastic bag type layer for protection and integrity in shipping stuff, but you should just take that plastic bag layer off completely to reveal the actual recycled clothing insulation material inside, which you can then take and use for speakers of ALL types. Every time I take my recycleable items down to my neighborhood recycling place I look for and usually find some of this stuff, so I have a decent, workable pile of it now in my speaker workroom. So, anytime you happen to find any of that stuff you should really save it and try it out, because it works at least as good at damping as fiberglass or rockwool does, (or maybe even slightly better), but it is MUCH nicer to work with, and usually totally free, which is an added bonus of course!... I actually wish I knew of a place I could regularly buy those ground up, recycled clothing type of insulation batts, but I've never found any place that sells it. It seems to only be an "industrial" shipping thing, not necessarily intended for "consumer" use or "retail" sale, which is unfortunate, but "it is what it is" I guess, just use it whenever you can find it... So good luck finding some to try, you won't be disappointed if you do!
Hi John, I enjoy your videos and the information you have shared. I was wondering about alternate materials like old terry cloth towels rolled up and stuffed into areas of the speaker to do the damping, also using a bunch of old cut up tee-shirts and denim pants could also give more or less of a damping effect. These kinds of material are just sitting around in everybody's house, so why not try it eh? One material I haven't seen mentioned anywhere is a tight celled sponge. I just opened up my set of NLA Advents to do a re-cap, and encountered five large yellow sheets of sponge (12" X 12" X 3") in each box. Upon closing the boxes up with new sealing tape and adding a whole bunch of extra poly fill the advents sound better than new. I bought a ten pound box of poly-fil at Wal-Mart for $30, I might have been able to re-cycle old clothes and towels and saved the $30 for more capacitors for my next project.
Have you considered self adhesive automotive sound dampening material? You cut it to size and stick it on. It comes in two main flavors, closed cell foam and Mass Loaded Vinyl (MLV). The MLV weighs a lot more, but works better for low frequencies. I like your experimenting with stuffing material. I always thought it is used to cut down on internal reflections. You are using it to dampen resonances in the speaker walls themselves. I think to a limited extent it can be used to increase the virtual volume of the enclosure. What are your thoughts on this. I am an old sound guy from back in the day when all sound companies built their own speakers from professional drivers.
NoRes and bitumen sheets work on a totally different mechanical aspect of sound compared to fiber materials like rockwool and so on... Mass and inertia losses (bitumen, NoRes) is used to stop the pressure part of the soundwave (the peaks) from inducing vibration in solids like speaker cabinet walls. Transmissive losses (acoustafill, rockwool) work on the velocity part of the wave where airspeed is at maximum, which lowers the transmitted sound pressure linearly to the distance of material the sound has to pass through. Which is why you want fibrous materials in the middle of the box, where airspeeds are the highest. In a long/tall speakerbox you can see up to 3-4 times better damping of the long mode when placing the fill in the middle compared to placing the same weight of material packed into one end of the box. Cool to see you experimenting with dipole bass BTW! :) I have no doubt you will see bigger impact on your
Damping is damping. Same mechanism - vibration reduction. It's as simple as that. Some are more effective for certain things than others, but damping is still damping.
@@IBuildIt As you say, we're doing this to learn and to have fun.... :) I started doing this 25 years ago, so I recognize many of your mistakes - I did quite a few of them myself, very enthusiastically - 20 years ago. I still find audio engineering, acoustics and speaker building a fun hobby, but now I also have a solid formal education in engineering and quite a lot of experience - among other things 10 years in industrial work environment noise control. So no, damping is not damping here, since solids (walls, boxes) aren't the same as low density fluids (gasses) - they interact with things very differently... So say you have a 400Hz side panel resonance in a 1m tall speaker. To get rid of that you either apply some high-weight, high-loss material like bitumen to a portion in the center of the wall, or brace it better. This does NOTHING to dampen the 170Hz standing wave you get in the enclosed volume of air in a 1m tall box. To dampen the 170Hz standing wave, you use rockwool (or something similar) inside the box, preferrably close to the center where airspeed of the soundwave is at maximum. This in turn does absolutely NOTHING to dampen the 400Hz panel resonance. The only case where they're interacting is if you have a cavity resonance and a panel resonance at the same/close frequency - but this is actually quite rare.
@@AJBtheSuede Bracing isn't damping - that IS a separate mechanism, but a bitumen layer is damping. Not dampening, damping. Vibration reduction, by definition, is damping, and a panel resonance is vibration. The panel is moving - vibrating - and the damping reduces it. Damping the airspace is also damping. Damping is damping in any form it takes. So I don't know where you got your formal education, but you might want to ask for your money back. Every kind of fiber stuffing is a damping material. It damps panel vibrations and airborne resonances. It does both at the same time because it's in contact with the panels and it occupies the airspace.
Why airspeeds are the highest in the middle of the box? Doesn't sound travel at the same speed in the air? Is there any static point along the wavelength where air pressure is the highest? I mean, the soundwave vibrates all along the cabinet at the same intensity, doesn't it? It is not like a string, where amplitude points are fixed.
Interesting test to run, at least to me, would be how much of one material it would take to equal the damping capabilities of another by weight. Then a cost comparison could be made, as well as volume size. Great video!
I don't know if you are familiar with Jack White of the band White Stripes. But in his practice space he uses old tires , just piles them up, for his acoustic treatment, and bass blockers. Naturally, this assumes you have the extra space for tires. But what about cutting the tires and flattening them out, and then attaching them to the walls? You should be able to get old tires in a recycle bin at tire stores at little or no cost. Inside cabinets as well?
Hi John, I like your experiments a lot. My question wrt these different materials is, at what point is the density so high, that it should no longer be considered a dampening material but a solid. In this case, putting a plate plate in between speaker and bowl would be even more efficient in reducing the transmission of vibrations to the bowl. My personal diy speaker consideration, where I had to put dampening material in between the drivers and the port, I chose polyfill, since I didn't trust that other materials would let the pressure waves pass sufficiently and thereby making it more a closed box.
@Douglas Blake the walls directly behind and besides the drivers are covered with that eggbox looking material. It is a floorstander with port on the bottom. I was advised to stop standing waves with dampening material halfway the box between drivers and ports.
Hey John! Love your Videos! I am looking into getting an accelerometer and would like to know what kind of equiptment you use. I appreciate any suggestions. Keep up the great work! Jan
All of that info is right here on this channel in videos I made over the past few months. Just click my name and it'll take you to my channel where you can find all of those videos.
I heard fiberglass increases scratching frequencies because of all the itching , ha. But I did get told fiberglass is very detrimental if it gets into the cones ? It seems very possible anytime they are moved about? Is it all the little air pockets in these materials that dampen sound similar to ceiling batts ?
I like polyfill...especially the crinkled stuff I got from mahogany sound decades ago. Fiberglass???? Yeah works well...but strongly suggest it be covered with cheesecloth to mitigate the quantity of qlass knives getting caught in the spider
Bit of a joke noress! What it is is a sticky back vinyl and half an inch of poly foam, the vinyl actually is beneficial but better than that is linoleum stick it to the side walls with linoleum works the best, and with filling for balance. don't forget the front baffle on the inside.
I like to use cheap foam pads or panels to line my cabinets. I will add 2 or 3 layers together to increase density replicating the denser "acoustic foam" at a much cheaper price. If there is one product that completely stumps me as to why it is so very expensive, it is "acoustic foam" pads or sheets. I mean regardless of the "density", are foam pads still not primarily made up of "air"? I think foam sheets used in manufacturing sofa's could also work, and probably have more density than "acoustic panels". But are likely more expensive as well. I haven't tried it, but rubber pads may also work, as I'm pretty sure rubber is much denser than foam. And adding a thin, tightly woven and dense towel like a "dish towel" over the foam or rubber sheet would probably work even better if you wanted to go through the extra work, having it be the material facing inside the box.
Would those high density yoga mats be a potential option? Just curious as there is a 6mm thick high density PVC yoga mat at Walmart for $30. I don’t know much about dampening but I was looking for Mass Loaded vinyl (difficult to find locally) and was curious if anyone knows of this material has dampening properties?
Why couldn't you have just measured the frequency response of the speaker using the different materials? That is what would convince me of the best fill material.
The materials being used are not damping the panels or bowl directly. They reduce ringing because the sound bounces between the internal sides. The middle of each object is where air velocity is highest, therefore porous absorption works best. This is an important distinction, you are reducing internal standing waves, not panel resonance. That would be the domain of methods like constrained layer damping or extremely dense bracing. Not to say that your video isn't useful, just that absorption and damping need to be used together for a truly high tier design.
@@IBuildIt I suppose you're already aware, but standing waves also form between the sides of a speaker's cone as they radiate outwards towards the listener, even though the sides of a speaker cone are not parallel to one another, because sound doesn't ONLY travel in a straight line, it bounces all over the place at just about every angle, (which is also why you preferably only want to use any specific size of driver cone up to a specific frequency, based on the wavelength of that frequency, but that is another topic entirely), but this guy's point here is valid, where an ultimate *combination* of using BOTH something like "No-Res" (which stands for Non-Resonant or No Resonance, I'm sure), or the more commonly known "Dynamat" type of *panel* damping material, together along with an effective "standing wave" insulation like fiberglass, rockwool, or those ground up clothing type of insulation batts, will work "best of the best" overall, because BOTH panel damping AND standing wave reduction at the same time, will result in the most effective internal sound reduction in a speaker box, therefore more resulting sound can be heard "only" coming from the speaker driver(s) themselves, which in *most* cases is what you want for best clarity and detail, especially in the upper bass/midbass, midrange, and highs. (That depends on the speaker design of course, because some extremely high-end "boutique" speakers I've seen and heard over the years, actually design their speaker cabinets like a tuned instument, like a violin, guitar, etc, to actually *utilize* their specific cabinet resonances to *enhance* and balance out their specific speaker's overall sound and "presentation", but that's another method of building speakers entirely, which is MUCH more elaborate and complicated, beyond the scope of most "normal" speaker building where the cabinet should be damped as much as possible.) Also don't forget about damping of the baffle itself that the drivers are mounted to, in order to reduce *refraction* losses... Although that specific topic will have to be another comment entirely, because the best materials to use for that are different than internal box damping materials...
@@IBuildIt Haha, never EVER give up, my man! (I know you're joking, but...) Speaker building is a total ARTform, one which is learned and most importantly, REFINED over MANY decades throughout your life! (If you are one like me who is serious and dedicated to your craft, which I get the feeling that you are!)
@@IBuildIt BTW, I love your videos, I get something useful from most every one of them, even if it's nothing more than a further confirmation of what I already figured I knew myself.
Why don't you just go buy a good set of speakers......wait maybe someone likes doing it themselves and experimenting to see what works. All snide remarks aside. I enjoy your videos, can't say I understand everything but I enjoy seeing what you come up with.
Have you considered the health risk of using it in a bass-reflex enclosure? All that glass pumped in the air you breathe? I know the workers that handle this stuff wear masks... It can also damage the drivers in a closed enclosure, by getting in the motor and rubbing against the voice coil.
Because testing by weight is the only constant I can accurately control. Here, let me tell you what testing by volume will give: rockwool first, fiberglass second and polyfil last. I know that because these tests show that of the three, rockwool is the best, fiberglass is a close second and polyfil is the least effective.
@@IBuildIt its that order because you did it by weight that order could very well change if you dod it by volume and you could easily control for volume fill a speaker until it seams full with each. Thats what people would do when building a speaker. Take Balsa wood if you did a test by weight it would be stronger than steel but if you did a test by volume it would lose miserably. So if you had some thing that was constrained by volume but not wait like a speaker box need to consider the volume as the constrained
So go ahead and do it, then. Conduct your own tests - you have a camera and a RUclips channel, same as me, so go for it! This is RUclips, remember, not Science TV. No one is paying me for this, I'm doing it because I think it's interesting and I figure there's at least a few people out there that are smart enough to get something from it.
@@IBuildIt i would but i have a full time job and two kids under 6. And youtube pays me 20 bucks a month. I was just commenting on the video you made. Your a full time youtuber you have the setup you could get it done quick and easy.
@@AllMyHobbies Anyone with half a brain can see that what John did and says in his reply is consistent with the test. Volume won't change the results magically and make one better than it was in the weight test. I'm a simple man but I can see this as plain as day.
I sense some Acoustic Fields influence with the use of the term "building insulation". I said at the end of the video why - they are easy to get and inexpensive. And they get the job done as well or better than the boutique materials.
@@jacktough it's also virtually useless as a damping material inside a box, and for most everything else. And because it's useless, I don't have any. What it is good for is decorating a room to "look" like it's treated and also for shipping eggs.
@@IBuildIt Also, have you ever spoken on how to determine best crossover frequencies in 2/3-way speaker setups without benefit of electronic measuring equipment, as well as how to avoid "beaming"? Thanks 👍
I thought this would be a more direct test to demonstrate what these damping materials do inside a speaker box. It shows the effect the stuffing has on the sound waves coming from the speaker before they hit the bowl and make that vibrate, and it also shows how effective it is at shortening the "ring time" of the bowl itself.
And of course the sound can and will go around the stuffing on its way to the bowl, but I thought this would give a relatively good approximation of the damping power of the sound waves by the damping material only.
Some will say that a bowl isn't a speaker box, but they are not at all dissimilar. The box will "ring" in the same way, just at a different frequency and amplitude depending upon the stiffness and self-damping properties of the wood used to construct the box. The bowl just gives a more dramatic demonstration.
It's worth pointing out that these tests that I'm doing are not to give this problem more weight than it it deserves. In most regards, box vibration and the sound that comes from it isn't a problem at all, since it will be so far below the speaker output that you won't be able to detect it. It's only when (in my opinion and experience) the panels get to be very large and unbraced and undamped that they can put out enough sound energy to be heard.
When building speakers there's ALWAYS a tradeoff. And in my opinion the best approach is to concentrate on the factors that will make the most difference first, and not get bogged down fretting over box material or stuffing / damping. These factors are very low in the overall design as far as ultimate sound quality is concerned. Knowing this will better equip you to make the important tradeoffs to get the results you are looking for.
Hopefully your guidance will resonate with listeners/viewers and they will learn enough to get on with their project, get it done and enjoy it. A finished project sounds better than a work-in-progress! Great, simple demo to illustrate what the effects are.
I see what you did there Jeff. :-)
Very interesting indeed. I've dabbled with speaker builds in the past but never gone in-depth in the subject or done measurements on it
These tests were awesome John! It fed my curiousity as a 'what if this, what if that' kind of (over)thinker.
Nice John. Much appreciated. These tests are really great for those interested in speaker building. I like the common sense thought process also.
Great demonstration to really hammer home what using damping can do for a speaker. Really interested in trying out the rockwool/fiberglass combo (especially seeing as I have a bunch of trimmings kicking around from having rebuilt an exterior wall and roof). I just built a pair of 2 ways with a passive radiator design to go out on my patio in the summer, going to get them outside to take some measurements soon as I don't have a decent indoor listening space. Loving the repurposing of this channel, and as always the content on the main channel! Thanks for all the work you put in John!
For international customers, to keep shipping costs down, we sometimes recommend a combination of heavy vinyl floor tiles or a butyl dampener and fiberglass/rockwool insulation instead of Norez. It's a lot more readily available and usually saves 40-50% on international shipping costs, and has the exact same effect.
heavy vinyl floor tiles . I've been recommending this for car audio people who are broke and it works really great!
I agree with these results, because I've done these same kinds of tests myself, but not with as much "tech" as you have there. I really WISH I had the programs, computer, mics, etc. that you used to show these graphs... in less than a second for each one, which is amazing, plus the ability to instantly then A/B compare the graphs on the computer screen, now THAT is an awesome program and setup there! I love it! The ONLY pieces of equipment I have is an old fashioned analog/manual knob frequency generator that I obtained for free many years ago, an old Radio Shack analog SPL meter that someone gave me, and my multimeter that I've had since high scool days, along with my very good ears of course, which I have taken very good care of over the years, because I love sound, speaker building, and music so much, so when I came up with these same results it was from my many HOURS of meticulous measuring and careful listening to different frequencies and materials, but so I could do SO MUCH MORE, and MUCH faster and easier, if I was able to afford to buy all of this high tech equipment you have! Wow! I also would love to have an oscilloscope, but I don't have one because I can't afford one, not even a used one...
Anyway, getting off topic slightly there, but I agree that the "Polyfil" stuffing is all but worthless in speakers as damping material, especially with the pitiful, "wispy" amounts of it that most speaker manufacturers put inside their speakers from the factory, (if they even bother with damping material at all), so when I see a speaker company's rather lame and useless attempt at damping like that I just laugh. And the ones that actually DO use it, definitely DON'T use enough of it to even have any positive effect! I always just take that tiny piece of polyfil stuff out and line the box with something better... almost anything else works better than that stuff does, lol!...
One thing that I will say about fiberglass though is that it's of course a pain to work with because it gets all over in the air and makes you cough and itch, which I really HATE, so then I tried the Rockwool stuff too, and the main problem I've found with that, in addition to the same problems fiberglass has with being extremely messy and irritating to work with, is that Rockwool is also damaging to any drivers that have a vented voice coil, because the sharp and considerably abrasive and heavy particles of it, kind of like an extremely fine sand, will eventually get inside the driver voicecoil and former itself and then start to cause rubbing and scratching of the enamel on the relatively tiny voicecoil wire, which of course is very bad for the driver itself, basically rendering it useless!...
With all of that being said however, and if you don't mind the mess and skin and lung irritation, both fiberglass and rockwool ARE effective and acceptable to use with sealed back drivers, (i.e. NON-vented voicecoil ones), especially since both of those materials are also reasonably easy to obtain and cheap, like at your local home center, hardware store, etc... However, I have finally found in recent years an even better, seemingly even more effective, definitely much easier to work with, totally non-damaging, and, most importantly, usually totally FREE material to use for very effectively damping speaker boxes with... You can usually find it in recycle dumpsters inside shipping boxes for various lightweight and/or delicate products... It is the batting that is made out of recycled clothing and textiles, (i.e. the ground up "blue jean" type insulation batts), and I have found that this type of insulation is quite readily available in your public neighborhood recycling facility dumpsters because it is used for padding and shipping so many things nowadays because it's "environmentally friendly". When/if you look for that stuff, it is sometimes wrapped with an outer plastic bag type layer for protection and integrity in shipping stuff, but you should just take that plastic bag layer off completely to reveal the actual recycled clothing insulation material inside, which you can then take and use for speakers of ALL types. Every time I take my recycleable items down to my neighborhood recycling place I look for and usually find some of this stuff, so I have a decent, workable pile of it now in my speaker workroom.
So, anytime you happen to find any of that stuff you should really save it and try it out, because it works at least as good at damping as fiberglass or rockwool does, (or maybe even slightly better), but it is MUCH nicer to work with, and usually totally free, which is an added bonus of course!... I actually wish I knew of a place I could regularly buy those ground up, recycled clothing type of insulation batts, but I've never found any place that sells it. It seems to only be an "industrial" shipping thing, not necessarily intended for "consumer" use or "retail" sale, which is unfortunate, but "it is what it is" I guess, just use it whenever you can find it... So good luck finding some to try, you won't be disappointed if you do!
I just bought the minidsp umik-1 which is whats being used in this video. 99 bucks and free software.
I used an accelerometer in this test. It measures mechanical vibration, not sound.
Just love what you do both in construction and test.
Hi John, I enjoy your videos and the information you have shared. I was wondering about alternate materials like old terry cloth towels rolled up and stuffed into areas of the speaker to do the damping, also using a bunch of old cut up tee-shirts and denim pants could also give more or less of a damping effect. These kinds of material are just sitting around in everybody's house, so why not try it eh? One material I haven't seen mentioned anywhere is a tight celled sponge. I just opened up my set of NLA Advents to do a re-cap, and encountered five large yellow sheets of sponge (12" X 12" X 3") in each box. Upon closing the boxes up with new sealing tape and adding a whole bunch of extra poly fill the advents sound better than new. I bought a ten pound box of poly-fil at Wal-Mart for $30, I might have been able to re-cycle old clothes and towels and saved the $30 for more capacitors for my next project.
Cool and inciteful test. Can't wait to optimize my damping materials based on frequency.
Have you considered self adhesive automotive sound dampening material? You cut it to size and stick it on. It comes in two main flavors, closed cell foam and Mass Loaded Vinyl (MLV). The MLV weighs a lot more, but works better for low frequencies.
I like your experimenting with stuffing material. I always thought it is used to cut down on internal reflections. You are using it to dampen resonances in the speaker walls themselves. I think to a limited extent it can be used to increase the virtual volume of the enclosure. What are your thoughts on this.
I am an old sound guy from back in the day when all sound companies built their own speakers from professional drivers.
You know what? You're a pretty smart guy!
Project Farm has entered the chat
NoRes and bitumen sheets work on a totally different mechanical aspect of sound compared to fiber materials like rockwool and so on... Mass and inertia losses (bitumen, NoRes) is used to stop the pressure part of the soundwave (the peaks) from inducing vibration in solids like speaker cabinet walls. Transmissive losses (acoustafill, rockwool) work on the velocity part of the wave where airspeed is at maximum, which lowers the transmitted sound pressure linearly to the distance of material the sound has to pass through. Which is why you want fibrous materials in the middle of the box, where airspeeds are the highest. In a long/tall speakerbox you can see up to 3-4 times better damping of the long mode when placing the fill in the middle compared to placing the same weight of material packed into one end of the box.
Cool to see you experimenting with dipole bass BTW! :) I have no doubt you will see bigger impact on your
Damping is damping. Same mechanism - vibration reduction. It's as simple as that.
Some are more effective for certain things than others, but damping is still damping.
@@IBuildIt As you say, we're doing this to learn and to have fun.... :) I started doing this 25 years ago, so I recognize many of your mistakes - I did quite a few of them myself, very enthusiastically - 20 years ago.
I still find audio engineering, acoustics and speaker building a fun hobby, but now I also have a solid formal education in engineering and quite a lot of experience - among other things 10 years in industrial work environment noise control.
So no, damping is not damping here, since solids (walls, boxes) aren't the same as low
density fluids (gasses) - they interact with things very differently...
So say you have a 400Hz side panel resonance in a 1m tall speaker. To get rid of that you either apply some high-weight, high-loss material like bitumen to a portion in the center of the wall, or brace it better. This does NOTHING to dampen the 170Hz standing wave you get in the enclosed volume of air in a 1m tall box.
To dampen the 170Hz standing wave, you use rockwool (or something similar) inside the box, preferrably close to the center where airspeed of the soundwave is at maximum. This in turn does absolutely NOTHING to dampen the 400Hz panel resonance.
The only case where they're interacting is if you have a cavity resonance and a panel resonance at the same/close frequency - but this is actually quite rare.
@@AJBtheSuede Bracing isn't damping - that IS a separate mechanism, but a bitumen layer is damping. Not dampening, damping.
Vibration reduction, by definition, is damping, and a panel resonance is vibration. The panel is moving - vibrating - and the damping reduces it.
Damping the airspace is also damping. Damping is damping in any form it takes.
So I don't know where you got your formal education, but you might want to ask for your money back.
Every kind of fiber stuffing is a damping material. It damps panel vibrations and airborne resonances. It does both at the same time because it's in contact with the panels and it occupies the airspace.
Why airspeeds are the highest in the middle of the box? Doesn't sound travel at the same speed in the air? Is there any static point along the wavelength where air pressure is the highest? I mean, the soundwave vibrates all along the cabinet at the same intensity, doesn't it? It is not like a string, where amplitude points are fixed.
Interesting test to run, at least to me, would be how much of one material it would take to equal the damping capabilities of another by weight. Then a cost comparison could be made, as well as volume size.
Great video!
Thanks John very informative series, Audio Mythbusters!
I don't know if you are familiar with Jack White of the band White Stripes. But in his practice space he uses old tires , just piles them up, for his acoustic treatment, and bass blockers. Naturally, this assumes you have the extra space for tires. But what about cutting the tires and flattening them out, and then attaching them to the walls? You should be able to get old tires in a recycle bin at tire stores at little or no cost. Inside cabinets as well?
What about Cotton as a material to use inside a speaker box?? I think you may need something to put it in like small pillow case, or cheesecloth?
Hi John, I like your experiments a lot. My question wrt these different materials is, at what point is the density so high, that it should no longer be considered a dampening material but a solid. In this case, putting a plate plate in between speaker and bowl would be even more efficient in reducing the transmission of vibrations to the bowl.
My personal diy speaker consideration, where I had to put dampening material in between the drivers and the port, I chose polyfill, since I didn't trust that other materials would let the pressure waves pass sufficiently and thereby making it more a closed box.
@Douglas Blake the walls directly behind and besides the drivers are covered with that eggbox looking material. It is a floorstander with port on the bottom. I was advised to stop standing waves with dampening material halfway the box between drivers and ports.
Hey John! Love your Videos!
I am looking into getting an accelerometer and would like to know what kind of equiptment you use. I appreciate any suggestions.
Keep up the great work!
Jan
All of that info is right here on this channel in videos I made over the past few months. Just click my name and it'll take you to my channel where you can find all of those videos.
I heard fiberglass increases scratching frequencies because of all the itching , ha. But I did get told fiberglass is very detrimental if it gets into the cones ? It seems very possible anytime they are moved about? Is it all the little air pockets in these materials that dampen sound similar to ceiling batts ?
I like polyfill...especially the crinkled stuff I got from mahogany sound decades ago.
Fiberglass???? Yeah works well...but strongly suggest it be covered with cheesecloth to mitigate the quantity of qlass knives getting caught in the spider
Will you try a CLD material like Noico? It's not that hard to find, any car audio shop has it.
Bit of a joke noress! What it is is a sticky back vinyl and half an inch of poly foam, the vinyl actually is beneficial but better than that is linoleum stick it to the side walls with linoleum works the best, and with filling for balance. don't forget the front baffle on the inside.
I guess there’s a reason JBL used fiberglass stapled to the inside walls of all their speaker since the 1950s... it works really well!
Do you sell the accelerometer like you use?
If I handled fiberglass with my bare hands I'd feel it poking the insides of my fingers for two days.
I like to use cheap foam pads or panels to line my cabinets. I will add 2 or 3 layers together to increase density replicating the denser "acoustic foam" at a much cheaper price. If there is one product that completely stumps me as to why it is so very expensive, it is "acoustic foam" pads or sheets. I mean regardless of the "density", are foam pads still not primarily made up of "air"? I think foam sheets used in manufacturing sofa's could also work, and probably have more density than "acoustic panels". But are likely more expensive as well. I haven't tried it, but rubber pads may also work, as I'm pretty sure rubber is much denser than foam. And adding a thin, tightly woven and dense towel like a "dish towel" over the foam or rubber sheet would probably work even better if you wanted to go through the extra work, having it be the material facing inside the box.
Can you tell me the model of accelerometer you used to meausure the resonance?How did you connect it to the soundcard?
Details in this video: ruclips.net/video/o1Fctgs8CcQ/видео.html
Would those high density yoga mats be a potential option?
Just curious as there is a 6mm thick high density PVC yoga mat at Walmart for $30.
I don’t know much about dampening but I was looking for Mass Loaded vinyl (difficult to find locally) and was curious if anyone knows of this material has dampening properties?
The way you handle fiberglass scares me.
Science!
Why couldn't you have just measured the frequency response of the speaker using the different materials? That is what would convince me of the best fill material.
I'm thinking you should abandon the fiberglass and go straight to meatloaf for better damping...
Barehand fiberglass no gloves... I'm already itchy.
The materials being used are not damping the panels or bowl directly. They reduce ringing because the sound bounces between the internal sides. The middle of each object is where air velocity is highest, therefore porous absorption works best.
This is an important distinction, you are reducing internal standing waves, not panel resonance. That would be the domain of methods like constrained layer damping or extremely dense bracing. Not to say that your video isn't useful, just that absorption and damping need to be used together for a truly high tier design.
Given the bowl's open shape without any parallel sides, how would standing waves form? Think about what you are saying.
@@IBuildIt I suppose you're already aware, but standing waves also form between the sides of a speaker's cone as they radiate outwards towards the listener, even though the sides of a speaker cone are not parallel to one another, because sound doesn't ONLY travel in a straight line, it bounces all over the place at just about every angle, (which is also why you preferably only want to use any specific size of driver cone up to a specific frequency, based on the wavelength of that frequency, but that is another topic entirely), but this guy's point here is valid, where an ultimate *combination* of using BOTH something like "No-Res" (which stands for Non-Resonant or No Resonance, I'm sure), or the more commonly known "Dynamat" type of *panel* damping material, together along with an effective "standing wave" insulation like fiberglass, rockwool, or those ground up clothing type of insulation batts, will work "best of the best" overall, because BOTH panel damping AND standing wave reduction at the same time, will result in the most effective internal sound reduction in a speaker box, therefore more resulting sound can be heard "only" coming from the speaker driver(s) themselves, which in *most* cases is what you want for best clarity and detail, especially in the upper bass/midbass, midrange, and highs. (That depends on the speaker design of course, because some extremely high-end "boutique" speakers I've seen and heard over the years, actually design their speaker cabinets like a tuned instument, like a violin, guitar, etc, to actually *utilize* their specific cabinet resonances to *enhance* and balance out their specific speaker's overall sound and "presentation", but that's another method of building speakers entirely, which is MUCH more elaborate and complicated, beyond the scope of most "normal" speaker building where the cabinet should be damped as much as possible.)
Also don't forget about damping of the baffle itself that the drivers are mounted to, in order to reduce *refraction* losses... Although that specific topic will have to be another comment entirely, because the best materials to use for that are different than internal box damping materials...
Lol. I give up!
@@IBuildIt Haha, never EVER give up, my man! (I know you're joking, but...) Speaker building is a total ARTform, one which is learned and most importantly, REFINED over MANY decades throughout your life! (If you are one like me who is serious and dedicated to your craft, which I get the feeling that you are!)
@@IBuildIt
BTW, I love your videos, I get something useful from most every one of them, even if it's nothing more than a further confirmation of what I already figured I knew myself.
Did someone Triple dog dare ya!? 😀
Why don't you just go buy a good set of speakers......wait maybe someone likes doing it themselves and experimenting to see what works. All snide remarks aside. I enjoy your videos, can't say I understand everything but I enjoy seeing what you come up with.
Using more Rockwell will be the most effective
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Rock Wool!
Have you considered the health risk of using it in a bass-reflex enclosure? All that glass pumped in the air you breathe? I know the workers that handle this stuff wear masks... It can also damage the drivers in a closed enclosure, by getting in the motor and rubbing against the voice coil.
Totally harmless at these low quantities. But if you are concerned, put it inside a plastic bag.
Do equal volume. Why is it useless?
Try carpet
Ya but like, how do you use this stuff without giving customers lung cancer?
By encouraging them not to smoke it, of course.
But you didn't test mashed potatoes.
The testing of mashed potatoes happens after the video goes live and people watch it and comment.
Speaking of mashed potatoes, that is what I am giving out to trick or treaters this year.
Why not volume that is the constant a speaker has you only have so much volume. The speaker can be any weight you want it does not matter!!
Because testing by weight is the only constant I can accurately control.
Here, let me tell you what testing by volume will give:
rockwool first, fiberglass second and polyfil last.
I know that because these tests show that of the three, rockwool is the best, fiberglass is a close second and polyfil is the least effective.
@@IBuildIt its that order because you did it by weight that order could very well change if you dod it by volume and you could easily control for volume fill a speaker until it seams full with each. Thats what people would do when building a speaker. Take Balsa wood if you did a test by weight it would be stronger than steel but if you did a test by volume it would lose miserably. So if you had some thing that was constrained by volume but not wait like a speaker box need to consider the volume as the constrained
So go ahead and do it, then. Conduct your own tests - you have a camera and a RUclips channel, same as me, so go for it!
This is RUclips, remember, not Science TV.
No one is paying me for this, I'm doing it because I think it's interesting and I figure there's at least a few people out there that are smart enough to get something from it.
@@IBuildIt i would but i have a full time job and two kids under 6. And youtube pays me 20 bucks a month. I was just commenting on the video you made. Your a full time youtuber you have the setup you could get it done quick and easy.
@@AllMyHobbies Anyone with half a brain can see that what John did and says in his reply is consistent with the test. Volume won't change the results magically and make one better than it was in the weight test. I'm a simple man but I can see this as plain as day.
Why not use dampening materials that made for speakers instead of using building insulation. Long hair sheepwool, twaron angle hair etc.
I sense some Acoustic Fields influence with the use of the term "building insulation".
I said at the end of the video why - they are easy to get and inexpensive. And they get the job done as well or better than the boutique materials.
Egg crate foam is cheap and plentiful. Would you anticipate different results by lining the interior of the box thusly?
@@jacktough it's also virtually useless as a damping material inside a box, and for most everything else. And because it's useless, I don't have any.
What it is good for is decorating a room to "look" like it's treated and also for shipping eggs.
@@IBuildIt Thank you for your prompt and no-nonsense reply! Keep the great content coming! 👍
@@IBuildIt Also, have you ever spoken on how to determine best crossover frequencies in 2/3-way speaker setups without benefit of electronic measuring equipment, as well as how to avoid "beaming"? Thanks 👍