ATC SCM100 clone - tweeter choice and inside damping

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#42
I got some pretty interesting insights guys 😉

someone with a pair of original ATC SCM100 screwed them open, opened them up and voilá:
no egg crate at all on the walls! BUT its 100% filled with some kind of wool ..very likely synthetic wool he claims.

It has wool batting inside. Most likely synthetic. There's not much more to say about it.
The wool is to dampen internal resonances. It is 100% lightly filled -- not stuffed. The wool has a lot of "loft" (expandability)

The tube is clear in the sense that it isn't filled but there is wool all around it and in front of it's internal opening. Wool being around the tube when the tuning frequency is 30Hz (including one octave up to 60Hz) will have zero effect due to wavelengths. In essence, at those frequencies, the wool is invisible to the sound.
Click to expand...
 
#44
hugo stiglitz said:
I got some pretty interesting insights guys 😉

someone with a pair of original ATC SCM100 screwed them open, opened them up and voilá:
no egg crate at all on the walls! BUT its 100% filled with some kind of wool ..very likely synthetic wool he claims.
Click to expand...


Interesting indeed but not all that surprising.
ATC has been on record that their porting is not according to any textbook alignments. Probably somewhere between port loading and resistive vent loading like Dynaudio did or does.
 
#46
What I meant although the correct term eluded me at the time is aperiodic loading with one or more Variovents like this one.
 

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#51
Hello Hugo,

somewhat late for the party I am interested in sharing your experiences with your SCM100 clones.

I am running a pair of AOS Monitor 50TL for years. The speakers are built with seperated enclosure/units for treble, mid and bass.
Meanwhile the speakers are fully activated, using a custom-made stand-alone active crossover by Abacus and three YBA power amps.
Never fully satisfied with the bass response of the Scanspeak W26 alu bass driver working on the TL, I am thinking about a swap for a longer time.
Incidentally I stumbled about a pair of ATC SB75-314 SC which I will implement as a substitute for the Scanspeak W26.

I need some inspiration regarding the enclosure (e.g. net volume, bracing, damping, port size) and will appreciate any support.
As a funny coincidence I am living near Dusseldorf.
So please get in contact with me to have a conversation, at least referring the ATC topic.

Thanks in advance
 
#52
@hausmuller

I can only encourage you to go for a pair of SCM100 clones. I'm happy with them after all these years.
Regarding the enclosure, I used the ATC dimensions you'll find here: https://atc.audio/wp-content/uploads/2013/01/SCM-100-PRO.pdf
You want to aim for a volume of 100 liters. The SCM series always gives the volume in their name:
SCM100 = 100 L cabinet, SCM50 = 60 L cabinet...etc.

Original ATC cabinets are not braced at all. It's just a big box of wood.
I did a lot of bracing and even dampend the sides with bitumen.
You'll lose a bit of volume with all the bracing but you can compensate it with some Basotect absorption.
That's what I did.

Length of the bass-reflex tube was the biggest myth when I built mine.
But you want a tube length of ~30cm which will result in a resonance frequency of 28-30Hz for the port. Which is ideal and exactly what ATC does too.

If you have any further questions, feel free to ask.
Cheers
 
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