Quad 57 or 63 with Gradients

Hmmm. I posted a response, and I think I even went back and saw it up here, but is no here now.

So, lemme try again.

The '57 beams pretty seriously in the treble region, and the tweeter panel has an absorbent pad behind it so the radiation is monopole instead of dipole. The result is a relative lack of reverberant field energy in the treble region. So there may be a little bit of room for improvement there.

The tweak is this: Use a cheap 1" soft dome tweeter to fill in some of the missing treble energy in the reverberant field. We want its output to arrive after the first-arrival sound, which I define as the interval before the precedence effect or Haas effect kicks in. This corresponds to a path length difference of about 9 inches, so to be safe we want the tweeter about a foot or so behind the panel, sitting on the floor, facing up.

The tweeter is wired in parallel with the electrostat, and a capacitor is wired in series with the tweeter to act as a low pass filter. I suggest about a 2 microfarad cap as a good starting point for a typical 88 dB ballpark 8-ohm tweeter. Probably a good idea to avoid a 4-ohm tweeter in this application, as even with a series capacitor that might make the load a bit nasty for some amps.

I don't think it's necessary, and maybe not even desirable, to spend a lot of money on the reverb-field tweeter.

edit: Seems to be up there this time. Maybe I just previewed it and never really posted it before, only thought I had.

Duke
dealer/manufacturer

Hey Duke,
Great. You know I did that in the olden days, exactly as you have said now and I thought I was the only one who had thought that one up..... Just goes to show......
Cheers,

Duke,
Thanks for the tip and I will try this with my 57s. Just one question: Would you need a resistor in series with that capacitor and, if so, what value would you recommend? I'm thinking that the Quads are more than 8 ohms over some of their range. Thanks!

Cleo, I used a potentiometer in series until I had the sound just right, measured the resistance and then soldered in a resistor of the same value, if I remember right.

Detlof, very cool! It sounds like you probably came up with it before I did. I first tried the Quad tweeter tweek around 2000 or so, I think; it was after I got my first SoundLabs. I think Martin Logan later used a rear-firing tweeter on some of their smaller electrostats, like the Clarity.

Cleopatra52, you might need a resistor with some tweeters and not with others. I'd suggest getting a small assortment like maybe two each of 2, 4, and maybe 6 ohms. Sand-cast resistors are pretty cheap so that wouldn't push the price up by much.

Note that as you increase the impedance of the load that the capacitor sees by adding series resistance, the crossover point will move downward. So you might want to get an assortment of several smaller capacitors (which can be paralleled to give a larger value if called for). These won't be very expensive either as long as you go with something reasonable like Solens or Daytons.

Duke