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Old 15th September 2012, 10:06 AM   #321
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Quote:
Originally Posted by Audionutz View Post
Im using an Australian made amp, an ME-75. Extremely stable. I have used a variety of this brand over the years. This particular unit drove my Scintillas effortlessly to high levels. Re-capped with Nichicons and biased up to about 15w class A.

My speakers are the Model 6 I believe ? 4 x MK-121 Pwr Supplies, 3 panels across and two high.


Regards

Scott
So this is what you have, sorry for the model 6 i tought you had a pair of Spectra 11 your in a different ball park my friend as a Plinius SA-250MK1V with is Spectra6600 doesn't have your problems.

Click the image to open in full size.

[IMG]file:///C:/Documents%20and%20Settings/Andre/Mes%20documents/Mes%20images/ME-75%20Amplifier%20Back.jpg[/IMG]

[IMG]file:///C:/Documents%20and%20Settings/Andre/Mes%20documents/Mes%20images/Acoustat%20Spectra%206600%20&%20MrAcoustat.jpg[/IMG]
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Old 15th September 2012, 10:13 AM   #322
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Quote:
Originally Posted by MrAcoustat View Post
So this is what you have, sorry for the model 6 i tought you had a pair of Spectra 11 your in a different ball park my friend as a Plinius SA-250MK1V with is Spectra6600 doesn't have your problems.

Click the image to open in full size.

[IMG]file:///C:/Documents%20and%20Settings/Andre/Mes%20documents/Mes%20images/ME-75%20Amplifier%20Back.jpg[/IMG]

[IMG]file:///C:/Documents%20and%20Settings/Andre/Mes%20documents/Mes%20images/Acoustat%20Spectra%206600%20&%20MrAcoustat.jpg[/IMG]
I have compared the ME-75 against the Plinius in years gone by. With 40 amps (continous) 300w at 1ohm and stable into a dead short, the ME was a better performer, in my experience at least. Also, the bass on the ME was superior to the Plinius, maybe due to the Bi-Polar vs Mosfet outputs ?

Regards

Scott
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Old 23rd September 2012, 08:15 PM   #323
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Originally Posted by AcoustatAnswerMan View Post
One can certainly bypass the input capacitor with straight wire, but doing so can lead to saturation of the transformer, since it is not designed for low frequency operation. This will also lower the low-frequency impedance considerably, making the load more difficult for the amplifier.

A better choice, if one is interested in experimenting with this idea, is to parallel the input capacitor with a 1-ohm, 50-watt resistor. This will largely remove the high-pass filter, while reducing the likelihood of transformer saturation. If going this route, one can also remove the parallel resistor (10-ohm?) in the input network, whose only function is to form the highpass filter along with the capacitor. With the capacitor bypassed with a resistor, the parallel resistor will act as a voltage divider, wasting amplifier voltage swing.
Thanks for the hint. I'll high pass filter the signal at about 100 Hz, so transformer saturation would be less of a problem I think.

I'm thinking about placing two panels side by side and connecting all four half panels to the full range signal from the transformer (before the 330k resistors). This would reduce the horizontal dispersion of the high frequencies, but since it's twice the width I don't think this would be a big problem. Do you agree? Are there other disadvantages to this setup?
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Old 24th September 2012, 07:01 PM   #324
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Quote:
Originally Posted by phazer99 View Post
Thanks for the hint. I'll high pass filter the signal at about 100 Hz, so transformer saturation would be less of a problem I think.

I'm thinking about placing two panels side by side and connecting all four half panels to the full range signal from the transformer (before the 330k resistors). This would reduce the horizontal dispersion of the high frequencies, but since it's twice the width I don't think this would be a big problem. Do you agree? Are there other disadvantages to this setup?
I think you would be disappointed with the results of driving two panels with only the full range output of the transformer. The Spectra interface is designed to drive only a small area for high frequencies, and therefore the frequency response is compensated so the overall response comes out correctly. Simply put, you would have WAY too much high frequencies with all that additional panel area.

You would also be throwing away all that is magic about the Spectra series, that is, a speaker that decreases in width as frequency increases. Set-up as intended, Spectra yields a speaker with pin-point imaging while avoiding a very narrow listening window.

If you want to try a side-by-side arrangement, try wiring it this way (for the left speaker, counting from the left side): segment #1 and #2, mids only; segment #3, full range, and segment #4, mids only. The right speaker would be a mirror-image of the left one. This would be similar to the arrangement in the Spectra 22/2200, but obviously without much bass response. You'd probably also need to change the value of the 330K sector resistors to about 100K to keep the crossover frequency the same.
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Old 25th September 2012, 04:17 PM   #325
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I have a 25+year old set of Acoustat +1 (I believe thats correct?). They have an attached woofer enclosure and since I didn't buy them new I'm not sure of the model#.
Years ago i installed the medallion upgrade and reconed the woofers and have enjoyed them thoroughly especially since I added on an audio/visual room (19' x 24'-with a stepped ceiling) and bought both a Lexicon MC-12 and two Lexicon/Bryston mono amps to drive them. #1-I need some advice if there is any any upgrades the Acoustat answer man can offer? and #2 if the existing wire terminals/posts can be replaced as I have a terrible time making a tight mechanical connection to the speaker cables with the banana clips I'm using.
Thanks for any help you can offer.
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Old 26th September 2012, 10:26 AM   #326
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Yes Scott your speakers are the model 6s included is a photo of your amp and Jocelyn's model 6 speaker before he made them into Spectra 6600s. André

Click the image to open in full size.
Click the image to open in full size.

Click the image to open in full size.
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Old 27th September 2012, 07:18 PM   #327
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Quote:
Originally Posted by mikeygoodguy View Post
I have a 25+year old set of Acoustat +1 (I believe thats correct?). They have an attached woofer enclosure and since I didn't buy them new I'm not sure of the model#.
Years ago i installed the medallion upgrade and reconed the woofers and have enjoyed them thoroughly especially since I added on an audio/visual room (19' x 24'-with a stepped ceiling) and bought both a Lexicon MC-12 and two Lexicon/Bryston mono amps to drive them. #1-I need some advice if there is any any upgrades the Acoustat answer man can offer? and #2 if the existing wire terminals/posts can be replaced as I have a terrible time making a tight mechanical connection to the speaker cables with the banana clips I'm using.
Thanks for any help you can offer.
Replacing the binding posts is both possible and a good idea. The originals were not all that great. The only caution might be that some alternate binding posts may require a larger hole in the chassis, which would require some careful drilling or filing (make sure no bits of metal remain in the chassis!).

Since you already did the Medallion modification, and reconed the woofer, there's not much else to do. There is an electrolytic capacitor in the audio path (220-uF?) that could be replaced with a polypropylene or other premium type, but that large a value can be quite large (and expensive).
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Old 29th September 2012, 04:23 AM   #328
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Quote:
Originally Posted by MrAcoustat View Post
Yes Scott your speakers are the model 6s included is a photo of your amp and Jocelyn's model 6 speaker before he made them into Spectra 6600s. André

Click the image to open in full size.
Click the image to open in full size.

Click the image to open in full size.

Thats the amp ! The woodwork on the the Spectras is very nice. Are the frames wooden, or is there a steel frame underneath ?

Regards

Scott
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Old 29th September 2012, 08:33 PM   #329
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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.
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Old 30th September 2012, 12:03 AM   #330
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Originally Posted by Audionutz View Post
Thats the amp ! The woodwork on the the Spectras is very nice. Are the frames wooden, or is there a steel frame underneath ?

Regards

Scott
Hi Scott, the frame is 2x4 steel covered with mahogany wood each speakers weigh around 600 pounds each
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