Acoustat Answer Man is here

[AcoustatAnswerMan]

Originally Posted by phazer99

I've gotten hold of a second pair of Spectra 11's (even cheaper than the first pair ) and did some measurements today. I bypassed the high pass filter, disconnected the Spectra woofer and set the crossover for the subs at 100 Hz. The panel drops quite steeply below 250 Hz so there was a quite big "valley" in the frequency response before the subs took over. However, the sound was very crisp and clear with better highs, but I also heard some pops/cracks (panel discharges?), which made me a bit worried.

Connecting a second panel in parallell to the same interface made the frequency valley a bit less deep, but it would require some kind of digital EQ compensation to run the panels flat down to 100 Hz. Maybe the easiest option is to get hold of a pair of Spectra 22/2200 interfaces or transformers (if anyone has some for sale I'm interested ). Meanwhile I think I'll just replace the high pass caps with better ones.

I am not at all surprised by your results. Neither the 11/1100 transformer or a single panel will have much response below 200 Hz. Adding more panel area will help some, but you are still limited by the LF response of the transformer. LF performance is what makes a transformer expensive, and it's no wonder that the full range Spectra's have about eight times more 'iron' in the transformers.

I am also not surprised at the increase in crackling of the panel. You are probably running into some saturation of the transformer, plus a single panel can act that way when you are trying to run it full range. However, it is highly unlikely you have caused any damage to the panel. This is why all of Acoustat's single-panel models are hybrids.

I guess the moral of the story is that you can't make a silk purse out of a sow's ear (not that I would suggest that the Spectra 11 is a sow's ear).

[phazer99]

Originally Posted by AcoustatAnswerMan

I am not at all surprised by your results. Neither the 11/1100 transformer or a single panel will have much response below 200 Hz. Adding more panel area will help some, but you are still limited by the LF response of the transformer. LF performance is what makes a transformer expensive, and it's no wonder that the full range Spectra's have about eight times more 'iron' in the transformers.

Do you know the specs/model of the Spectra 2200/3300 transformers? Is it something you can buy off the shelf?

[MrAcoustat]

Originally Posted by phazer99

Do you know the specs/model of the Spectra 2200/3300 transformers? Is it something you can buy off the shelf?

Andy Szabo2007-10-07 23:24

The MK-2123 interface was common to Acoustat Models Spectra 22/2200, and 33/3300. An internal wiring difference changed the bass equalization for either the two-panel 22/2200, or the three-panel 33/3300. There should be a rubber-stamped number on the interface label indicating whether the interface is set-up for a 22/2200 or 33/3300. If for some reason that stamp is not visible, the speaker can be identified by its width: the cloth-covered portion of the 22/2200 frame will measure 21.5" wide, and the 33/3300 will measure 31.75" wide. The only difference between the 22/33 and the later 2200/3300 is the cosmetic wood and brass strips along the sides of the panel. The panels and interface electronics are identical.



You can find most of your answers here this is the Acoustat bible.


Acoustat

[AcoustatAnswerMan]

Originally Posted by phazer99

Do you know the specs/model of the Spectra 2200/3300 transformers? Is it something you can buy off the shelf?

All Acoustat transformers were custom-made, so are not available 'off the shelf'. However, there may be some NOS or used parts that you may be able to find. Keep in mind that each full-range Spectra uses two identical audio transformers, one for each phase. So you need four for a stereo pair. Also keep in mind that the full-range Spectras use a more complicated high-voltage combining and sector-dividing network, so that must be created as well if you intend to build a full-range (or at least down to 100-Hz) speaker. There are also complete, used speakers available, so that might be an easier route.

[Atom666]

Hi Andy
Here is my attempt at a Monitor 4/ Spectra 44. There are 4 x 9" panels at a 6 degree angle. 2 panels are 3 wire and 2 panels are 5 wire .I am going to drive them with a MK121C interface initally. I also have a Spectra MK2123 interface .My question is can I drive the 4 panels with the Spectra 33 tap ,or will there be too much bass?
Thanks
Andrew

[MrAcoustat]

Originally Posted by Atom666

Hi Andy
Here is my attempt at a Monitor 4/ Spectra 44. There are 4 x 9" panels at a 6 degree angle. 2 panels are 3 wire and 2 panels are 5 wire .I am going to drive them with a MK121C interface initally. I also have a Spectra MK2123 interface .My question is can I drive the 4 panels with the Spectra 33 tap ,or will there be too much bass?
Thanks
Andrew

Sorry Andrew very nice model 4s but NOT 44s or 4400s because those need to be 22 inches wide by 94 inches high like these next to a pair of model 3s models -2 - 3 - 4 - are all about 66 inches high. André

[Atom666]

Sorry Andre
You obviously don't get it, see post #38
See here Acoustat Answer Man is here

Andrew

[MrAcoustat]

Originally Posted by Atom666

Sorry Andre
You obviously don't get it, see post #38
See here Acoustat Answer Man is here

Andrew

Ok Andrew did not notice that particular post but one thing i can tell you is that i had a friend like you that could not fit his Acoustat's 2+2s in his basement for the same reason ( height ) he did what you did 4 panels side by side they realy sounded good BUT did not sound like normal 2+2s BUT better than any boxed speaker at the same price

PS: They do look very nice ENJOY

[MrAcoustat]

Originally Posted by david yost

I agree with you, MrAcoustat, the 1+1s are a wonderful speaker. My next project will be to "Spectra" mine -- to improve horizontal dispersion a little -- and add either a single plane bass array or a double bass array; then I am done! I promise!

QUOTE: Then I am done, I and my wife have heard that statement before

[hella356]

Nice job, Andy. You're going to end up with a totally unique Acoustat. I'm very curious to hear about how combining the standard and Spectra interfaces turns out. Hopefully after zeroing in on the interface config you WILL be done, but no one here will hold you to your promise.