Excellent video, Matt, very interesting. As a lifelong hi-fi enthusiast and physicist with acoustics speciality, I'm delighted that my understanding concurs with your experience! 🙂 I'm looking forward to part 2! The crossover components used look nice quality but I'm surprised by the tiny inductors. All the best, Rob in Switzerland
Afternoon Matt👍👍it’s a clone of the scm40 though the original is an infinite baffle design. Best eat your porridge before you lift that bass driver, it’s got quite the motor unit! ATC made the crossover points at 380hz and 3.5k using their own tweeter.
I do not believe that has anything in common with the SCM 40, SCM40 is a far smaller driver and cabinet. It looks like the classic SCMK50 a SCM50 floorstanding copy based loosely on the SCM 50. ATC gave the go ahead for these and if I remember correctly you could even add ATC amp packs to these. SOS magazine built the SCMK100 in 1994. They compared favorably to the originals if built well. The ATC SCM 50 wasn't renowned for very low bass either with a -6db point at around 40hz, coupled with a dry accurate bass, low bass is one point many feel lacking in the SCM 50, noticeable when you move on to PMC or KERR. It's been a long time since I read on these things, but if I remember general concensus was the cabinet was average build quality and materials, and the crossover let it down, with a handfull of alternatives having been designed by forum users around 15 years ago.
The ring radiator tweeter with “silver” trim is the big giveaway it is a clone.. This would be an interesting rebuild with mods.. BTW, I’m green with envy to those local peeps who could easily purchase your line of BBC inspired speakers..
Nice driver curves. I've got a pair of old ATC SCM20 speakers. Massive motor structures. I can never get them to sound quite how I like. Always a bit harsh in lower treble, but not very open and airy up top. I do like the midrange in general though. Looks like impedance correction or Zobel on the bass/mid and a resistor pad to the tweeter. Also I had to replace the the ferrofluid in the tweeters (modified Vifa D26TG) as it had dried up to a thick gunk. Didn't improve the top end though. I can't fit the new ATC tweeters as the face plate is a different size and ATC are reluctant to sell me them anyway. If I were closer to you, I'd bring them in for a tweak. I know who makes those ATC kit clones, but I think the drivers ATC supply for DIY are not quite the same as the production ones, for some reason.
If you haven't figured out a way to avoid the laws of physics, then you have (lots of) reflections from the microphone stand🙂- This is particularly noticeable in the higher registers. Take a look at Troels Gravesen's website. He explains it all in a good way.
@@asterixx6878 The measurement microphone has to be on some form of stand. It cannot float in the air. Any reflection compared to the fundamental will be way down in SPL. Smoothing pretty much dials it out. Not something I've ever been concerned about. How do you set up your microphone?
@@haycrossaudio5474 It was just a well-intentioned piece of advice. You follow it if you want, if you don't.....that's ok by me. I have the microphone as Troels Gravesen describes it on his website (youtube removes my post if I link to the page). The rule is that the microphone should be at (at least) half the distance from the microphone stand, compared to what is from the speaker's baffle. Do a search for "troels gravesen microphone setup", and you will find Troels' page. I take this opportunity to thank you for your nice videos. It's always nice to follow others who have the same hobby as you.🙂
@@haycrossaudio5474 It was just a well-intentioned piece of advice. You follow it if you want, if you don't.....that's ok by me. I have the microphone as Troels Gravesen describes it on his website (youtube removes my post if I link to the page). The rule is that the microphone should be at (at least) half the distance from the microphone stand, compared to what is from the speaker's baffle. Do a search for "troels gravesen microphone setup", and you will find Troels' page. Anyway, really nice videos. It's always nice to follow others who have the same hobby as you.
wow that tweeter was way too hot...you could see it ringing on the decay measurements! I guess you need to find out just how high the woofer can play up to before it breaks up? That might be why they are keeping it low?
These look like my own scm40s. Bass is -6db 48hz and infinite baffle rather than bass reflex. Where did the bass reflex idea come from, they designed their woofer for their own designs.
@@haycrossaudio5474 Yes it could be a 50 not a 40 clone, they have a floor standing version of the standard 50scm, but it has the same 50 litre internal volume. Not really happy with the deviations from a known good design, a bit of a lash-up.
@@johnshaw359 I didn't build them remember. I'm just here to sort them out. What they are or what they are copies of doesn't really bother me 🤣. Cabinets are good. Very solid and well built. It just all went wrong with there crossover design. It's a shame. I wonder how many more of these are out there 🤔
That crossover just looks so wrong. So they have used some totally over the top capacitors but the coils are way too small. Whoever designed this should be....... I have heard the original ATC's and they actually sound very nice. Looks like someone has built a nice speaker the messed up the most important part.
Excellent video, Matt, very interesting. As a lifelong hi-fi enthusiast and physicist with acoustics speciality, I'm delighted that my understanding concurs with your experience! 🙂 I'm looking forward to part 2! The crossover components used look nice quality but I'm surprised by the tiny inductors. All the best, Rob in Switzerland
Afternoon Matt👍👍it’s a clone of the scm40 though the original is an infinite baffle design. Best eat your porridge before you lift that bass driver, it’s got quite the motor unit! ATC made the crossover points at 380hz and 3.5k using their own tweeter.
@@kjbunnyboiler I've sort of ended up with similar crossover points 😍
I do not believe that has anything in common with the SCM 40, SCM40 is a far smaller driver and cabinet. It looks like the classic SCMK50 a SCM50 floorstanding copy based loosely on the SCM 50.
ATC gave the go ahead for these and if I remember correctly you could even add ATC amp packs to these. SOS magazine built the SCMK100 in 1994. They compared favorably to the originals if built well.
The ATC SCM 50 wasn't renowned for very low bass either with a -6db point at around 40hz, coupled with a dry accurate bass, low bass is one point many feel lacking in the SCM 50, noticeable when you move on to PMC or KERR.
It's been a long time since I read on these things, but if I remember general concensus was the cabinet was average build quality and materials, and the crossover let it down, with a handfull of alternatives having been designed by forum users around 15 years ago.
The ring radiator tweeter with “silver” trim is the big giveaway it is a clone.. This would be an interesting rebuild with mods..
BTW, I’m green with envy to those local peeps who could easily purchase your line of BBC inspired speakers..
Cheers mate
Thanks for explaining baffle step loss
Nice driver curves. I've got a pair of old ATC SCM20 speakers. Massive motor structures. I can never get them to sound quite how I like. Always a bit harsh in lower treble, but not very open and airy up top. I do like the midrange in general though. Looks like impedance correction or Zobel on the bass/mid and a resistor pad to the tweeter. Also I had to replace the the ferrofluid in the tweeters (modified Vifa D26TG) as it had dried up to a thick gunk. Didn't improve the top end though. I can't fit the new ATC tweeters as the face plate is a different size and ATC are reluctant to sell me them anyway. If I were closer to you, I'd bring them in for a tweak. I know who makes those ATC kit clones, but I think the drivers ATC supply for DIY are not quite the same as the production ones, for some reason.
With that mic setup you get a huge amount of reflections from the mic stand itself. It will inevitably compromise your measurements.
@@asterixx6878 Not at all.
If you haven't figured out a way to avoid the laws of physics, then you have (lots of) reflections from the microphone stand🙂-
This is particularly noticeable in the higher registers.
Take a look at Troels Gravesen's website. He explains it all in a good way.
@@asterixx6878 The measurement microphone has to be on some form of stand. It cannot float in the air. Any reflection compared to the fundamental will be way down in SPL. Smoothing pretty much dials it out. Not something I've ever been concerned about. How do you set up your microphone?
@@haycrossaudio5474 It was just a well-intentioned piece of advice. You follow it if you want, if you don't.....that's ok by me.
I have the microphone as Troels Gravesen describes it on his website (youtube removes my post if I link to the page). The rule is that the microphone should be at (at least) half the distance from the microphone stand, compared to what is from the speaker's baffle.
Do a search for "troels gravesen microphone setup", and you will find Troels' page.
I take this opportunity to thank you for your nice videos. It's always nice to follow others who have the same hobby as you.🙂
@@haycrossaudio5474 It was just a well-intentioned piece of advice. You follow it if you want, if you don't.....that's ok by me.
I have the microphone as Troels Gravesen describes it on his website (youtube removes my post if I link to the page). The rule is that the microphone should be at (at least) half the distance from the microphone stand, compared to what is from the speaker's baffle.
Do a search for "troels gravesen microphone setup", and you will find Troels' page.
Anyway, really nice videos. It's always nice to follow others who have the same hobby as you.
wow that tweeter was way too hot...you could see it ringing on the decay measurements! I guess you need to find out just how high the woofer can play up to before it breaks up? That might be why they are keeping it low?
@@gavinralph2910 See part 2 😊
These look like my own scm40s. Bass is -6db 48hz and infinite baffle rather than bass reflex. Where did the bass reflex idea come from, they designed their woofer for their own designs.
@@johnshaw359 no idea. These apparently are a clone of an ATC model. The SCM50 apparently. I've seen this woofer in a ported enclosure.
@@haycrossaudio5474 Yes it could be a 50 not a 40 clone, they have a floor standing version of the standard 50scm, but it has the same 50 litre internal volume. Not really happy with the deviations from a known good design, a bit of a lash-up.
@@johnshaw359 I didn't build them remember. I'm just here to sort them out. What they are or what they are copies of doesn't really bother me 🤣. Cabinets are good. Very solid and well built. It just all went wrong with there crossover design. It's a shame. I wonder how many more of these are out there 🤔
That crossover just looks so wrong. So they have used some totally over the top capacitors but the coils are way too small. Whoever designed this should be.......
I have heard the original ATC's and they actually sound very nice. Looks like someone has built a nice speaker the messed up the most important part.