The UI-core setup with primary on each leg does take a bit of thought, but in the end:
If the dots were supposed to be indicative of winding polarity, then the schematic is wrong.
If the dots were used in an unconventional manner to indicate start or end of a winding, then it is correct as shown.
Anyone got some input regarding my questions about SPL?
Are these the questions you are referring to?
Yes, adding/increasing baffle width does increase the low end SPL of ESL panels very similar to dynamic driver OB arrangments.I'm not sure if adding baffle width around the panel would increase the low end SPL (for a dynamic driver it would). Any expert that can answer this?
But, chasing low end SPL by adding too much baffle width and dips/ripples will show up in the midrange.
The Spectra 11 panel had D/S of about 2.2mm. At 250Hz the limitation to max SPL is not the diaphragm hitting the stator, but rather break-down or conduction of the air in the gap. Based on the physical dimensions of the panels, the max SPL at 250Hz for one Spectra 11 panel at a listening distance of 2m would be about 103dB. The max SPL of the mini panels would be about 9dB - 12dB less than that.
Since the mini-panels D/S spacing is half that of the Acoustat, only half the step-up ratio is required to reach max SPL.
For similar winding geometry, this would allow halving the core size.
Acoustat medallian and C transformer Question
I have Acoustat 2 + 2's with medallian and C upgrades driven by Moscode 600.
I've been toying with the idea of separating the inputs to the bass and treble transformers and biamping the speaker, possibly with a small tube amp on mid/treble transformer/panel.
I actually have been toying with the idea of remaking the panels with kynar wire and more wires per inch. Possibly a center treble section driven by the treble transformer (and possibly tube amp).
Can some one tell me the frequency range of the treble transformer.
Looking at the total Capacitance (230 uF) should yield a crossover of ~170 Hz (with 4 ohm impedance).
Is it this simple, I know their is no zobel network, and the impedance of the speaker rises above and below this crossover point.
Does the transformer have its own roll off that changes this crossover point?
Question 2. If I made a separate mid treble section with narrower d/s spacing,using the same bias tap approximately 4 inches wide, any ideas on the crossover point I should shoot for.
Speaking from ignorance, I was thinking of changing the cap values to have the treble transformer/ treble panel cut in at about 1kHz?
Thanks,
Paul
I have Acoustat 2 + 2's with medallian and C upgrades driven by Moscode 600.
I've been toying with the idea of separating the inputs to the bass and treble transformers and biamping the speaker, possibly with a small tube amp on mid/treble transformer/panel.
I actually have been toying with the idea of remaking the panels with kynar wire and more wires per inch. Possibly a center treble section driven by the treble transformer (and possibly tube amp).
Can some one tell me the frequency range of the treble transformer.
Looking at the total Capacitance (230 uF) should yield a crossover of ~170 Hz (with 4 ohm impedance).
Is it this simple, I know their is no zobel network, and the impedance of the speaker rises above and below this crossover point.
Does the transformer have its own roll off that changes this crossover point?
Question 2. If I made a separate mid treble section with narrower d/s spacing,using the same bias tap approximately 4 inches wide, any ideas on the crossover point I should shoot for.
Speaking from ignorance, I was thinking of changing the cap values to have the treble transformer/ treble panel cut in at about 1kHz?
Thanks,
Paul
I asked back in post #147 if anybody had used the plexiglass half cylinder to allow the speakers to be placed closer to the wall, but got no reply about anyone actually trying. My 2+2's are 3' from the rear wall, but it would be nice, from the WAF aspect, to place them closer to the walls if I can get roughly the same sound/imaging. There post I asked about is this one..
Spectra 22 check-up?
I've had Spectra 22's for a little over a year now but have had them sidelined for much of that time as it seemed they were not delivering the performance I was given the impression (from owner testimonials) they are capable of. I listened to them for a few months starting out first with a restored/refurbished Soundcraftsmen MA5002 then a Aragon 8008. The Aragon gave their sonic character a little more meat but I still found they couldn't reach SPL's beyond 85-90 db without developing what sounded like "panel slap" with LF content. I've never had the socks off and have done nothing in terms of cleaning the panels or measuring the transformers to see if bias is in spec or whatever else one might measure to ensure proper performance. It's been suggested to me to go over the panels with a blow dryer but I'd like to hear the opinions of a few others before I attempt this. Could someone please offer me a "checklist" of sorts so I can inspect and restore to best possible performance?
Oh, and I also have a pair of Threshold S/300's with one of them being the optical bias model. These have been recapped with main cap values increased to a little more than 2x the stock values as well as the rectifier upgrade and higher quality caps throughout. Not sure if the Threshold would offer much, if any, more performance than the Aragon. I can't remember if I tried the Threshold with the 22's....it's been almost a year now....but seems I did and the panel slap was still there. Having the pair of Thresholds sure makes me wish the Spectra 22's biamp capable. Can it be done?
Thanks,
Michael
I've had Spectra 22's for a little over a year now but have had them sidelined for much of that time as it seemed they were not delivering the performance I was given the impression (from owner testimonials) they are capable of. I listened to them for a few months starting out first with a restored/refurbished Soundcraftsmen MA5002 then a Aragon 8008. The Aragon gave their sonic character a little more meat but I still found they couldn't reach SPL's beyond 85-90 db without developing what sounded like "panel slap" with LF content. I've never had the socks off and have done nothing in terms of cleaning the panels or measuring the transformers to see if bias is in spec or whatever else one might measure to ensure proper performance. It's been suggested to me to go over the panels with a blow dryer but I'd like to hear the opinions of a few others before I attempt this. Could someone please offer me a "checklist" of sorts so I can inspect and restore to best possible performance?
Oh, and I also have a pair of Threshold S/300's with one of them being the optical bias model. These have been recapped with main cap values increased to a little more than 2x the stock values as well as the rectifier upgrade and higher quality caps throughout. Not sure if the Threshold would offer much, if any, more performance than the Aragon. I can't remember if I tried the Threshold with the 22's....it's been almost a year now....but seems I did and the panel slap was still there. Having the pair of Thresholds sure makes me wish the Spectra 22's biamp capable. Can it be done?
Thanks,
Michael
Sorry, not a perfect reply, as I haven't used these plexiglass panels.
I have priced plexiglass/lexan at Home depot. I think you'd be about 100 dollars per speaker for a nearly 8 ft tall piece thats 2 feet wide.
I built my own tube traps. with chicken wire that I used needle and thread to form cylinders, made a round cap for the top, and put a piece of sheet metal on the inside for about 1/3 of the diameter. Filled it with blow in insulation.
Covered it with a nice wool fabric from JoAnne Fabrics.
Works quite well. Face the tube trap with the reflective surface facing the speaker. Mount it right behind the speaker, or make a stand to mount it on top of the transformer box.
Total cost for both was less than 50 bucks, and about 2-4 hrs.
I still don't like the sound of the speakers to close to the front wall.
I've had mine more than 10 ft from the front wall, and in a different configuration about 4 ft from the front wall. They (2 + 2's) sound significantly better 10 ft from the front wall.
My opinion is that if you can't set up the speakers the way they sound best,
you should opt for something the wife will be pleased with that will sound it's best set up near the front wall, and therefore less obtrusive.
Paul
Being of limited panel area, the Spectra 22/2200 does have its limits, especially in the reproduction of low frequencies. However, you may have some issues that are preventing the speaker from reaching its true potential.
The 'panel slap' may be caused by a loss of tension in the diaphragm. This can be remedied by the careful application of a hair dryer or industrial heat gun. After removing the grille socks, the panel should be vacuumed on both sides, or with care, blown out with low pressure compressed air. The re-shrinking of the mylar can be done from the front side only, by slowly and continuously moving the hot air over the entire surface of the panel. This process may take several tries before it's effective, but it's better to approach this process slowly rather than appying too much heat at once.
Measuring the bias voltage is not easy, but see my comments in another post made today. However, it's not likely to be the cause of panel-slap, nor is it likely that both speakers are suffering from low bias to the same degree. So unless one speaker is playing louder than the other, bias voltage is probably not an issue for you.
Your choice of amplifier will make a difference in the final performance of the speaker, but is not likely to be responsible for your panel slap.
The good news is that the panel-slap will not cause any damage to the Acoustat speakers (that's not necessarily true for other ESL brands) but it can be very annoying. It may be that you are merely reaching the dynamic limit of the speaker, especially if your music had a lot of bass content. And if you are listening to movie soundtracks, which often have enormous amounts of LF content, the problem will only be worse.
If, after re-shrinking the mylar, you still experience the same problem, it may be time to invest in a companion subwoofer, which will relieve the speakers of reproducing low frequencies. This will increase the dynamic capacity of the system by a large margin.
One movie soundtrack that will let you know if there is a problem is THIS ONE.
A friend of mine gave me an old set of 2+2's becuase he had blown up the transformers and he did not want to spend the money to try to fix them.
Because the original frames and covers were in poor condition and that they were too tall to fit into my house I decided to build my own frames and incorporate a subwoofer.
I rebuilt the interface units by having new transformers wound, capacitors, resistors and diodes replaced and incorporated a crossover to send the low bass to the subs.
Bass? yeah...I got that! ;-)
A couple of my minions attaching the panels
Sliding on the socks
Side view in my old home theater
My old home theater featuring a 53" HDTV and Plasma Ball
Because the original frames and covers were in poor condition and that they were too tall to fit into my house I decided to build my own frames and incorporate a subwoofer.
I rebuilt the interface units by having new transformers wound, capacitors, resistors and diodes replaced and incorporated a crossover to send the low bass to the subs.
Bass? yeah...I got that! ;-)
A couple of my minions attaching the panels
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Sliding on the socks
An externally hosted image should be here but it was not working when we last tested it.
Side view in my old home theater
An externally hosted image should be here but it was not working when we last tested it.
My old home theater featuring a 53" HDTV and Plasma Ball
An externally hosted image should be here but it was not working when we last tested it.
Nice rebuild job! Proof once again that old Acoustats never die, even if they need a little help, as in your case.
I agree. I watched that movie on my system and recall that it had very prominent LF content. Even my Spectra 4400's complained a little bit, despite being crossed-over to a subwoofer below 80 Hz. I like movies with lots of LF content, but I think some of them overdo it, leaving only a few very fine systems capable of properly reproducing it. Of course, the average sound system probably doesn't even try, so lots of folks never realize what they're missing.
Is there any frequency issues with the panels on tone bursts or impulse response at certain frequencys within safe SPL limits?
I ask because I am considering a set of acoustats to try out in the future but don,t want uncontrolled ringing that points to "signature" sound at any level of uncontrolled output.
I rarely listen beyond 90 db (C weighting) but realize that spurious resonances are what they are at any level.
My understanding the acoustats required serious amplifier power and this leads me to believe they are large signal design transducers instead of small signal designs that translate to higher levels of output to produce their " magic " window of what they are
This is not to be confused with serious phase angles a low impedences at high frequency,s and current demands of amps BTW.
Were the Acoustats designed for a certain SPL window and if so what was that level?
Regards
David
I ask because I am considering a set of acoustats to try out in the future but don,t want uncontrolled ringing that points to "signature" sound at any level of uncontrolled output.
I rarely listen beyond 90 db (C weighting) but realize that spurious resonances are what they are at any level.
My understanding the acoustats required serious amplifier power and this leads me to believe they are large signal design transducers instead of small signal designs that translate to higher levels of output to produce their " magic " window of what they are
This is not to be confused with serious phase angles a low impedences at high frequency,s and current demands of amps BTW.
Were the Acoustats designed for a certain SPL window and if so what was that level?
Regards
David
I'm not sure I even understand some of your questions, so I won't attempt to address all of them.
But to answer the last one, regarding whether Acoustats were designed for a specific 'SPL window'. In a word, no. Acoustats can play at very low levels, while still delivering all the detail and delicacy that are the hallmark of ESL's. And they can play quite loudly (more so than many ESL's) and still deliver all the same qualities. In fact, in my opinion, they exhibit little or no change in sonic character with a large change in overall volume. And, I find them equally competent with all types of music, be it rock, classical, jazz or whatever.
Yes, the speakers do require robust amplification, but that is due to their low impedance and low efficiency. In other words, more power is required to make them play at a given volume compared to more efficient speakers. The large amount of power required should not be taken to mean that they only play loud.
My recommendation is to LISTEN to a pair and see if they deliver the sound that you want. Given proper amplification and room placement, I'm betting you won't be disappointed.
Ringing? I associate that with the inability of a transducer to stop motion after a signal has ceased to to be sent to it. This is partially a function of mass. Seeing how an esl speaker has incredibly low mass, this is a non issue, one of the reasons why the music sounds so startling realistic.
I have heard no issue in freq response at any volume. It is possible you can hear some but that can be due to improper setup.
I played around with the MCAAC calibration on my pio receiver when I first got my 2+2's and with room treatment and perfect angling, at every calibration point, there was not a deviation of more than 2 db. Anything under 3 db is deemed too small for the ear to perceive so you can say that these speakers can have a flat response, very impressive.I listened with my pio receiver serving as a preamp, now use a Carver C-1.
My receiver had a boost at the 50hz calibration point, so I will assume that output under that kept dropping. However, the bass that I get is just so clean and tight that I'd never want to wire in a sub (and I have an Infinity ssw 212 that I could use).Yeah, mids and highs are great, but I was shocked at how good the quality of bass was.
You really need a good amp for these. The first consideration in picking out an amp is not sound quality or specs but if it can handle low impedance loads without going poof. My Hafler XL 280 fits that bill, my just recapped NAD 208 sounds much better.
One example of the importance of handling a low load can be found earlier in this thread. Someone got some 300w per channel Emotiva mono blocks and the sound was thin, with the amps shutting down from overload. My Hafler XL280 (with just 145w per channel) can work them all night at high volumes with no complaints.
In this thread, people mention amps that they use and they all can laugh at low impedences. Amps like Hafler/Transnova are common as are other less well known makes.
The other factor is that these speakers beam and you need to sit in the sweet spot.
That can be a (in my case) a reclining chair with a spot for my microbrewed beer.
In summary, you need:
1) Acoustat speakers
2) An amp that can work these speakers
3) proper setup and room treatment
4) designated sweet spot.
I won't go into the importance of good analog sources as I do listen to CD's every now and then and they sound good.
Get all of these in place and you'll have sonic nirvana. If you can do all four of these, grab yourself some cone and dome speakers and don't listen to a properly setup acoustat system- you'll kick yourself for not going the ESL route.