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Old 1st March 2011, 02:21 AM   #61
Steve M is offline Steve M  Australia
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Quote:
Originally Posted by JonasKarud View Post
I do not know what Steve does to prevent "lobing" but i know that Dynaudio puts a small inductor in series with the upper treble driver, restricting it to 8 kHz.


Dynaudio Confidence C4 loudspeaker | Stereophile.com
I'm not exactly sure what you guys mean by 'lobing' and how it manifests itself in terms of what you can hear? But if you mean, does the ESL-3 speaker 'beam' a lot and have a very narrow sweet spot? The answer is yes it does (like all stats). I haven't done anything to resolve this issue, nor think that it is necessarily solveable - I just sit still and don't move my head too much when listening seriously to stats whether it be Quads-ML-Acoustat-ER Audio.

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Steve M.
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Old 1st March 2011, 10:13 AM   #62
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one case of "lobing" means that identical sound waves from the identical treble drivers is canceling out each other, causing irregularities in frequency response.
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Old 1st March 2011, 05:41 PM   #63
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The array is curved, the three panels are set at an angle a few degrees rotation for each WRT the next...


Speedskater, plug them in, charge up, play.

If the bias supply does not come up or up full, you need to replace the caps and diodes - easy.

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Old 1st March 2011, 05:53 PM   #64
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Andy, do you know the distance between stator wires and membrane, wire to wire distance and the thickness of the wires?
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Old 3rd March 2011, 08:03 AM   #65
gnnett is offline gnnett  New Zealand
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Hi Andy

Good to see you here. I posted the following question on Audiocircuit but if you don't mind will repeat it here.

This is in regards to the wiring of the transformers for the Spectra 44.

I am wondering if the pair of transformer primaries can be wired in series, rather than parallel to achieve an easier load for an OTL amplifier.

I have sucessfully used an autoformer (the zero) with my 1+1 and an aquaintence had great sucess with Model 6's, by wiring the two MK121 interfaces in series, with a similar OTL to mine.

I am guessing that if it is possible there might need to be a change to the resistor and capacitor network on the primary side of the transformers.

I realise that the results will be unknown until I try it, but checking to make sure there is no obvious fatal flaw with the idea.

Kind Regards

Grantn
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Old 4th March 2011, 09:41 PM   #66
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Hi, Grant

Not Andy, but I certainly don't see a problem with running the transformers in series as long as polarity is observed -- I think it would be very easy to do (and undo if necessary).
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Old 5th March 2011, 04:33 AM   #67
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Default Capacitor Upgrade Finally

Having worked at a store that sold Acoustats in the 70's, and reading the rave IAR review of the 1+1's in the 80's, I long wanted these, finally found someone able to ship to me in 2008 (many are offered for sale, but few sellers offer shipping for some reason...btw it shipped UPS in 4 boxes...I bribed the seller $300 for shipping and don't actually know how much he paid). I was lucky enough to score 1+1 Red Medallions with C circuit from factory (didn't even know about such nuances when I bought them). Had to replace one interface in 2009 after a loud rock session with a buddy, managed to get a third NOS Red Medallion C interface, cost nearly as much as I paid for the speakers. Soon I want to get that refurbed by Russel Knots so I have a replacement on hand, ready to swap back in.

I've had a good time, but I'm finally working up the motivation to replace the 47uF electrolytics with 600V solens. I actually bought the Solens in 2008, but they just sat in my infinite project procrastination basket.

Now I'm noticing what I'd describe as grundginess. I think I've been aware of a certain amount of that all along, but I can take it no longer. I'm hoping the cap upgrade will fix it, or at least greatly improve it. I've become a bit worried that maybe the panels themselves are wearing down (as I read on rather argumentative thread over at Audio Asylum last year). I had previously thought that to be impossible, these would last 50 years or more. With 85Hz crossover (LR48) or higher there is no bottoming.

I'm also now much more aware of the polar response. Both my panels must have stock HF balance setting, since one is a NOS unit that was never used until 2009, and they sound the same. I find that straight on axis, the response is a bit peaky 8-14khz, to get best sound you have to be a bit off axis (at the listening position), just back off a bit from the point where the highs suddenly disappear. (A friend of mine with ESL-63's says that most electrostats are like that, the best response is just before the fall off, including his, and that it's technically obvious to him that even the 63's were not intended to be listened to on axis.)

After the first few months, I got a big subwoofer (SVS PB13), now I have a pair of subs, tried different crossovers and EQ's and room corrections, now using 85 Hz crossover with no EQ. Was using Krell FPB 300, worked fine, now I'm using Parasound HCA-1500A until I get Krell repaired (developed age-related thermal bias runaway problem). Both amps sounded fine, though I think the Parasound sounds a tad brighter, and I think I liked the Krell better.

Last edited by charlesp210; 5th March 2011 at 04:46 AM.
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Old 5th March 2011, 09:48 AM   #68
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Default How should I put this big capacitor in Acoustat interface?

The picture shows the inside of my Acoustat Red Medallion C interface with the new Solen 47uF capacitor in front. It looks like the new capacitor (bottom) will fit either in front of the circuit board on right side, or above big transformer in back. There's more space in back, but nothing convenient to support the capacitor with and a long lead would be required, and there's high voltage back there. I'm leaning toward front installation.

In front, the capacitor could rise straight from where the fuseholder is, or lie flat above the fuse and two speaker terminals. Either way space is very tight, and one concern is that the capacitor would be very close to the 50K power resistor. If the resistor gets hot it could damage the capacitor, and there is high voltage on that resistor too. I might be able to give it "just enough" space, it looks like I could give it about 5mm space. Opportunities for support are also limited, but it would be somewhat self-supporting from it's own lead, so doesn't need that much additional support. If it falls "down" in operation it simply hits the wood base of the speaker. where the interace is installed.

I could possibly bend the power resistor out of the way, bit by bit using one or two sets of longnose pliers. The danger is that I could break it off it's solder pads, or, even worse, crack the old circuit board.

Another thought crosses my mind too. I could connect the capacitor BEFORE the fuse, so the capacitor effectively bypasses the fuse for the high frequencies. The speaker would still be protected from DC and low frequencies, which is likely where any problem would be. The fuse doesn't really do a great job of protection anyway from sustained loud music, sustained loud music can burn the transformer without melting the fuse. The fuse mainly protects against amplifier failure, and also provides nuisance warnings that you are playing too loud.

I could also have the capacitor outside, either as an independent entity (with new input terminal) allowing easy changes, but clumsy and space consuming, or strapped to the case with twist tie (requires new holes in case, not easy) or glued (ugly).
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Old 5th March 2011, 02:51 PM   #69
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I have a set like that and the cap is mounted on the back with zip ties. The back panel must have holes drilled to get the wire through and the zip ties through.
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Old 5th March 2011, 06:52 PM   #70
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Default Back mounting big capacitor

That may be the best way. It occurs to me that unless I have the capacitor rigidly held down to the box, it's going to be vibrating within some intense magnetic fields, which is not good. Plus, if it's supported mainly by it's extended leads, the leads develop weakness over time. Any sort of internal hold-down is going to require very clever use of something like posts, which I don't have. Holes would need to be drilled in the back for screw-in posts too. If unsupported, the capacitor could also be hitting the bottom panel during vibration, creating a new spurious noise.

The other clean option is separate box. If I'm going to the trouble of making a second box, I might choose to migrate the second PP bypass there too, for flexibility in subsitutions. And it would require two holes in back for input and output. I'm now leaning away from capacitively bypassing fuse, that could create wierdness in the network if other things are not bypassing fuse. I think I'll get a solid copper fuse substitute for when I want to play unfused.

But the problem with second box is that these speakers live to be moved because they are so position sensitive, and I often have guests, and any kind of separate boxes will be constantly getting in the way of moving the speakers.

One alternative way of internal support would be if the 50K resistors are bypassed (as I think Moray James has recommended), which requires other circuit changes. Then the capacitor could simply be tied to the electrically disconnected resistor. But I'm not going there this time around.

The one problem I see with back panel mounting the capacitor is that the ordinary method of disconnecting the speaker involves pulling the box back and resting it on the back panel. With capacitor in place, the back panel can only be leaned, not rested, during that process.

Last edited by charlesp210; 5th March 2011 at 07:00 PM.
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