Modifying a Compression Driver
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- Опубликовано: 25 июл 2024
- I modify the Fane CD.131 Compression Driver. My goal in this video is to compare the measured performance of various modifications. I then attempt to lower the resonance of the diaphragm to get bandwidth extension down to 600Hz. The goal is to understand and learn the performance aspects and the influence changes make to the overall performance balance.
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I appreciate that you did that risky work of modifying surround just in the name of science. Great video, insightful. thank you.
Here we are 4 years later... revisiting this video. For many
years one of the mods I make on compression drivers is to add a huge rear chamber, usually 3 to 4 inches in length, and then fill the cavity with absorptive materials. In essence, we are taking your addition of a foam piece, and adding orders of magnitude to the loss in the chamber. I have done this JBL and TAD drivers, both 1" and 2" exit.
Instead of layering the dome, just get some Aquaplas and thin it down to a viscosity that can be airbrushed. This will de-ring the dome structure without adding so much mass it becomes an acceleration/deceleration issue.
I always throw away JBL diaphragm's, and replace them with Radian.. the surround is vastly superior, more lossy and less stiff. TAD dias we keep.
Application of Aquaplas, 4" domes, apply between 1 and 1.5 grams.. weigh after it dries. Match them as close as possible. More added material kills acceleration, less is insufficient to damp effectively.
For 1" exit drivers with 1.75" dome, apply 0.20 to 0.28 grams.
Hi. First of all I want to congratulate you for your work. I recently discovered your channel and I am following you.
I have a question to ask you. How accurate is near field measurement for high frequencies? I ask you because I took a course on acoustic measurements a while ago, and the instructor told us that near-field measurements were only useful up to 500Hz.
On that occasion we were measuring the frequency response of a cabinet with 2 speakers (woofer and tweeter), and for the woofer he used the near field method, but to measure the response of the tweeter, he placed the microphone 1 meter away, at 1.20 meters high from the floor, and the cabinet was also at a distance that I don't remember from the back wall.
Thank you very much for sharing. Hug.
Amazing..... Sock in the hole..... I heard of that trick back in the 80's....... The sock ads clarity
Definitely with foam great knowledge video all around thank you
Now, what does modifying the diaphragm compliance do to the power handling? I would guess overexcursion at higher levels would be likely with a possibility of the diaphragm bottoming out on the phase plug in extreme conditions.
With the goal being adaptation for hifi use as opposed to pro sound that doesn't mean it's a bad thing. It only means a bit of experimentation to determine operable limits.
Alternately, adding a shim between the diaphragm and the driver body can allow added excursion, but changes to voice coil location in the gap...
3 tricks to improove eff. of tweeter.
1. Remove the front metal shield.
2. Use thick short cable.
3. Scratch with emery paper the inside of the coil former until you see it's thin enough, but without touching the diaphragm.
You will get 6 db improove
Cool experiment.
Absolutely fantastic job, thank you!;
instablaster...
Really cool dude 😎 💪🏼
A little more space and air around the decay of the brushes on the snare.
I'm a keen audio guy and wood turner, can you tell me where I might get the profile to turn myself some horns? I have a pair of DE250 waiting for something like this. Thanks
How would you find the wattage in RMS of a compression driver that only has a stamp on it of 16ohm? It came out of a LEM T6A DSP 3 way p.a speaker which is discontinued. Neither the 15" 8" and the 1" driver have RMS markings. It says in the scamatics that 500 watt RMS is going to the 15" and 150 watt RMS going to both the 8" mid and 1" horn.
I didn't get... A compression driver is a "compression" one exactly because it works on a horn resistance at one side and a small insulated chamber at another side. It needs a compression. Which hole are you talking about? Are you sure you used a proper horn with a proper acoustic resistance, so you must see a difference with and without a hole.
Not many go so far w details heheh I noticed not all high end drivers will produce all frequencies that’s why I always do pink noise with my equipment to fix all those frequencies and you won’t believe now many more better it sounds but then I end up not liking what my ears her so I go almost back to all flat heheh sometimes getting all those frequencies flat becomes harsh on the ears at the end of the day it’s what sound good to the ear and doesn’t fatigue .
I really thought you were destroying those speakers but it does sound better
WoW you can really hear the difference that your mods have made !!!!! , great job!!! - I thought I would let you know that the BMS 4592nd - Midrange can easily go down to 350 - Hz - the Volti Audio Vittora sounds really GREAT at that xover point!!!!! , I think that the DCM50 can get down there too, but I haven't heard it . I know there are also several other BMS drivers that can get down there too. THANK you great video I learned a lot.
@Dean Halleck reading that driver (the Fane Joseph modded here) specs it doesnt appear it's a mid... usable freq response is told 2-18kHz.
Hi where did you get the wood horn? Thanks with compliments for the experiment
They are made to order on my site.
josephcrowe.com/products/horn-no-1689-1khz-es-circular-horn
with foam the freq haas is down
no phase plug is good
cut the surround you down the freq respon but high is disapear.
Phase plug is needed.
O.M.A have a speaker called the De Ville with what looks almost identical to your compression driver design and they use a special bullet metal trilateral device put into the wooden passage of the compression driver....that is what you need to improve your speakers...check out O.M.A s videos concerning this
I thought it sounded significantly worse without the phase plug.
Hi Joseph, how did you remove the phase plug?
It did t take much effort to pop out. It was just glued in.
With the foam her voice was more upfront and not lost
Nice
have a good sound if isn't with horn?
Jean Fernandes it needs the horn. It sounds awful without it.
That’s called flashing when the plastic mould doesn’t seal tight.
Joseph, would you be interested in a pair of altec 290s?
Thank you, I may take you up on the offer but I first want to test out a recent pair of Altec's that I've purchased.
Your a horn god!! I hope to meet you some day. (Ampdjeep1 on IG)
It’s a compression driver I hole in it it’s like a boat with all that weight won’t work at all
Listen, the only frequency that all driver producer try to sound best is from 8000 hz to 12000 hz. You can`t do much because that is the best frequency for the ear but it`s the most dificult to imrove.
Sow, you can`t do much. It`s fisics.
For my opinion, a good line array wave guide can make them sound better and louder., or just buy a high qualitty 3 way cabinet
I have DE250, DE45, RCF N350 and 18Sound HD125 compression driver.
Wich sound best?
Smaller the diaphragm, cleaner the sound is.
Bigger the diaphragm, lower it goes but it looses clearness because from 10 000hz and below, it goes down.
Sow, it`s a matter of choise and what you use them for.
Thanks for the comments. There are many ways to improve the sound. The context of my video is for audiophile listening not live sound reinforcement. I’m not aware of any line array technology that would be suitable for audiophile listening. Although some do sound amazing, they require a very large venue, not a living room.
Try with a bigger horn.
You might be better off making a phase plug out of felt keeping the same shape
Interesting.
And I should have said maybe trying instead and as well with the original phase plug using alpaca wool very fine dense fibres packing the chamber behind the phase plug right tight to the phase plug. Having a gasket of 2 mm or so of sorbothane between the driver cone and the magnet body. Thing is you have to machine out the metal body of the magnet so you not extending overhanging the vocal coil. You could try some 3M surgical tape to start off with see what readings you get
It just so happens that I’m using alpaca wool now. Interesting on the foam spacer. I’ll look at doing that as well.
@@JosephCrowesDIYSpeakerBuilding what was the results you gotten from the alpaca wool.? it is good as a dampener for a chamber as well if you're inserting a tweeter or mid-range driver or sheep's wool
I never directly compared the alpaca wool to the open cell foam. But it would be interesting. Maybe I’ll do a quick test.