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Old 7th December 2011, 05:52 PM   #191
1lDel is offline 1lDel  United States
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Crazy, I've been maintaining business computer networks for years, and yet, this is my first forum attempt. I've read thousands of "how to do it's" and can't remember anyone ever explaining how to be in a forum before.

Just so you know, my Acoustat pair are unmodified, undamaged, perfect black power houses of pure sound. Used them once in a huge church to playback a recording of their PIPE ORGAN after installing new amps for them, and the congregation didn't know it was a recording, as the windows rattled just like normal on the pedel notes.
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Old 7th December 2011, 06:21 PM   #192
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Quote:
Originally Posted by david yost View Post
Hello, all

I am planning a system using a Cogent Research SPI that requires 4 identical loudspeakers arrayed in front of the listener at 30 degrees separation. I have 2 Acoustat Model 4 donor speakers, and because of ceiling height reasons, can't construct 4 1+1s from them. So my questions to the group are these: should I just build a set of 4 Model 1 full-range clones, or go for a double wide Model 2 lay out? Also, the only interfaces I have are a set of 4 from a pair Model 6s, a pair from the 4s (non-Medallion) and a pair from some 1+1s (blue Medallion) -- which interfaces do you recommend? I will be using stereo subs below 80-100 Hz or so and have 7 channels of 100W amplification.

My primary goal is precise imaging. My room is 17' x 22' with (unfortunately) 94" ceilings and the speakers will be arrayed in such a way that they face one of the longer walls.

Thanks for any and all suggestions.

BTW, I listen mostly to 50s-60s jazz, some classical symphony and chamber group.
You have a lot of options here. In the interest of using four matched interfaces, I would suggest the use of the four interfaces from the Model 6's. Although they have less bass boost than the regular MK-121, your use of subwoofers makes that largely a moot point. You'll want to experiment with the bass tap, more than likely you will end up using the green tap, which has the most bass boost.

If you mix-n'-match the Medallion (from the Model 1+1's) and non-Medallion (from the Model 4's) interfaces, there will be some subtle (some would say not-so-subtle) differences between the speakers. Of course, you can always experiment and see what combination suits you best. But for the best consistency among the four speakers, I would go for the Model 6 interfaces.

Since you have eight panels available, making four Model 2's would seem to make the most sense in terms of efficiency and bass performance. But a single panel per speaker, ala the Model One, would give you superior imaging. Since you are using subwoofers, and mentioned that precise imaging is your goal, perhaps the Model One configuration is the way to go.

Too bad your ceiling height is limited, because a 1+1 configuration would give you excellent imaging AND good bass and efficiency!

Sounds like a fun project - good luck!
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Old 7th December 2011, 07:07 PM   #193
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I have to concur with Andy about single panels and imaging. I have had more fun in screwing around with something in audio than ever before by just hooking two stock Mk121 transformer units to two bare single panels with some hard fibre 3" cardboard side wings. The sound is stupid good. Bass suffers but what is there is down into the mid 30's and is tight and deep. There must be something going on with one panel in the treble vs. multiple panels. The miss and highs are more "there" and correct tone and the highs are not rolled off like in a 2+2 setup or 3 wide like model 3. I do not like the overall signature of the 8" wide Acoustat panel. The 9" sound much nicer. Something too note is that with one panel per side tilted back about 5 degrees and toed in slightly and about 10" off the floor on a base of some sort and about 3 to 4 feet from the wall about 6 - 7 feet apart I get great results in a small living room. Standing back 15 feet from this type of set-up the result is very little image distortion with head movement. Very much unlike sitting dead center sweetspot with a pair of Model3 or Monitor3 where if you even tweak your head left or right there is a weird and pronounced imaging "jump" or change. Very "phasey" if you will. I believe the single panel is good if you can limit the bass excursion on dynamic material that will overdrive the panel. What I found is that when you start doing that it is not the panel that ultimately gets the abuse but it is the high current saturating or heating up the bass transformer. I believe also that Medallion bass transformers are not as robust in handling extreme voltages as well as the original Mk121. This is just opinion on my part though so don't count on what I'm saying. Just my observation after playing around with Interfaces and single Acoustat panels on and off for about 2 years now. Also IMO single panel is a tough load on an amp with higher volume levels and dynamics. Easier to drive 3 panels. But one per side is just tonally superior IMO and the tradeoffs are definitely there.
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Old 7th December 2011, 07:22 PM   #194
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Quote:
Originally Posted by AcoustatAnswerMan View Post
You have a lot of options here. In the interest of using four matched interfaces, I would suggest the use of the four interfaces from the Model 6's. Although they have less bass boost than the regular MK-121, your use of subwoofers makes that largely a moot point. You'll want to experiment with the bass tap, more than likely you will end up using the green tap, which has the most bass boost.

If you mix-n'-match the Medallion (from the Model 1+1's) and non-Medallion (from the Model 4's) interfaces, there will be some subtle (some would say not-so-subtle) differences between the speakers. Of course, you can always experiment and see what combination suits you best. But for the best consistency among the four speakers, I would go for the Model 6 interfaces.

Since you have eight panels available, making four Model 2's would seem to make the most sense in terms of efficiency and bass performance. But a single panel per speaker, ala the Model One, would give you superior imaging. Since you are using subwoofers, and mentioned that precise imaging is your goal, perhaps the Model One configuration is the way to go.

Too bad your ceiling height is limited, because a 1+1 configuration would give you excellent imaging AND good bass and efficiency!

Sounds like a fun project - good luck!
An additonal thought suggested by speedracer5:
Do your Model 4's have two 9-inch panels and two 8-inch panels? I know the original 4-panel speakers were built that way, but later ones might have had four 9-inchers. If you have the two different sizes, you can still use them, with the different sizes in corresponding symmetric positions in the array.

Here's a fun thought...
In re-reading your original post, I see that your ceilings are 94". If I recall correctly, the stock 1+1 is 94" tall, so with a little creative carpentry (thinner frames top & bottom, and thinner base) you could probably make a frame an inch or so shorter to fit in your room. NOW you can have the best of both worlds, with double-stacked panels, ala 1+1. A little more creative carpentry will allow the use of different sized panels, probably 9" on the bottom, and 8" on the top. Or you could make two frame widths, one for 8" and one for 9" panels, and arrange them symmetrically in the array.

Like I said earlier - you have lots of options here!
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Old 7th December 2011, 07:55 PM   #195
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Quote:
Originally Posted by AcoustatAnswerMan View Post
In re-reading your original post, I see that your ceilings are 94". If I recall correctly, the stock 1+1 is 94" tall, so with a little creative carpentry (thinner frames top & bottom, and thinner base) you could probably make a frame an inch or so shorter to fit in your room. NOW you can have the best of both worlds, with double-stacked panels, ala 1+1.
I was thinking the exact same thing.
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Old 7th December 2011, 08:05 PM   #196
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Thanks for all of the ideas, guys, I much appreciate it. BTW, after I made my original post the idea of hanging a 1+1 line from the ceiling with hooks and eyes occurred to me -- I could just use two strips of 1"x2" hardwood on either side of the panels and this would eliminate the need for bases and top and bottom framework, so they should fit in the room. Re-positioning (should it be necessary) would be a pain, but the SPI set-up instructions insist on very rigid and precise placement, anyway.

My best listening experience with Acoustats and preferred set-up is 1+1, but do you think they will suffer much with the Model 6 interfaces? How much difference in bass boost is there between interfaces and between taps? And, do you recall the frequency range where the boost occurs?

Thanks again,
David
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Old 7th December 2011, 08:17 PM   #197
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Would the panels hang in space or would they be secured at the floor?
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Old 7th December 2011, 08:27 PM   #198
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I was thinking that they would just hang from the side hardwood strips, although they could be braced or weighted at the bottom. It seems to me that a 1 gram diaphragm would have a hard time moving a 10kg panel assembly.

I know that many have used lead filled steel frames to really hold the panels in place -- do you think my idea is a recipe for lost resolution?
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Old 7th December 2011, 08:32 PM   #199
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I do know that the panels have sufficient force to crack the frames of a 2+2. Mine are cracked, and Moray James has noted that he's seen this several times. I think it could effect your results, but I guess there's only one way to find out. I'd just suggest you consider testing some form of bottom bracing.
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Old 7th December 2011, 08:41 PM   #200
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Hanging single panels would by my best guess really reduce bass due to no acoustic isolation from front to back of the panel at the bottom of the panel and also that the speaker would not get the boundary reinforcement from the floor. Any open baffle dipole speaker will obtain benefits in bass response by increasing the hard surface surrounding the driver. That includes the floor. If you build the 1+1 frame "just so" it should squeeze in to your 94" floor to ceiling height. It's awfully close. The panels measure 45.5" tall or there about. so that in itself is 91" and you need a little so as not to crush the wires exiting the panel and a top and bottom frame. So you have about 1" to spare if the top an bottom are 1" thick. No foot plate I guess or maybe 1/4" steel plate to keep a low profile. I personally don't like the tall speakers in anything but a huge room. I'll reserve final judgement on that though when I have more time to play with the 2+2's. Single 9" panels tilled back on the floor with a single interface and the bass tap wire at Model 3 (orange wire I think) setting is just really sweet sounding.

Would the bass excursion/drive be cumulative across the 4 driver units on the SPI setup David? Electrically if the set up used all four panels for bass energy that should at least load the room with enough bass to equal a 4 panel version Acoustat Like Model4 or 2+2. it is astounding how much bass a pair of well driven Model3 can make. I just can't stand the imaging anomalies that come with it. I'm not much help here but sharing what I've fiddled with might lead to some insight. Good luck with the project.

BTW how can I upload pics to post to this thread from my computer without having to use a separate site to post to first? Or is that not possible?
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