Hi Duke, an old thread, but I am about to try this tweak disadvantage by zero technical knowledge, but I do at least have a soldering iron!
I have stacked Quads, in parallel, connected to the one amp.
I have found a suitable, 8ohm one inch tweeter, and assume that the fact that it is rated at 91DB will probably make it about equivalent to the 88DB efficiency you had in mind for an average tweeter, given I have two pairs.
What I am wondering is what the different impedance of the tweeter circuit does to the way that the amplifier drives the different speakers, given that all speakers are connected in parallel, and driven by the same amp.
IE, why doesn't the power just go to whichever circuit (be that tweeter, or the two Quads) is easier to drive for the amp, at the particular point in time of the music?
I know this question betrays a fundamental lack of understanding of things electrical. I hope, however, that it is comprehensible as a question!
Happy to hear an answer from anyone who has one. |
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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 |
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. |
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! |
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, |
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 Detlof, I guess Duke is just a tease. |
Hi Duke, Hi Kubla,
Yea, so am I ((: |
Duke, I'm interested. What's the tweak? |
I've owned several pairs of 57's, and a pair of 63's with the dedicated Gradient subs.
In my opinion, a good pair of 57s sounds a bit better in the vocal region than a good pair of 63s. The 63s will definitely play louder. So there is no clear-cut winner, but my personal preference would be for the 57s.
Let me know if you might be interested in a minor, easily reversible tweak for the 57's (it's not something I sell).
Duke
dealer/manufacturer |
Depends how loudly you want to listen. You get better SPL with the 63s and the sweet sport is a tad larger compared to the 57s. But for absolute purity of sound in the midrange the 57 is hard to beat and the highs are wonderfully sweet. Not that the 63 is a slouch there either! I love them both, but needed higher SPLs, so I switched. you could of course also get 2 pairs of 57s and stack them. What amp to you intend to drive your speakers with? |
