Bi Amping the Silvers

Need some advice on bi-amping my Silver Amazings, two pairs, different versions. Main reason isn't for more power, though that would be a desirable by-product; it's to match the voicing of the different pairs by eliminating their different crossovers. I'm running the two pairs in a trinaural setup (one pair sharing the center position), and they sound a lot alike, but not really quite the same, being variations of the 3, or 4 or however many types of Silvers it's possible to own.

I could try to get (or wind) the right coils, etc. and match the crossovers (hard to do), but thought I'd try a different route, since I have the necessary amps just sitting around doing nothing. And besides, passive crossovers waste power, right?

Right now, I'm running all three channels with an A-753x, and it's pretty powerful (three channels, rated 440W into 4 ohms, and 770 into 2). But with Amazings there can never too much power, even with the extra drivers. So the 753 could just run the 12 woofers (6 in center ch, 3 each l and r). It's a high damping-factor (>150) type amp, so its well suited for this; in fact the improvement in low bass over the 1.0's is quite obvious: I was surprised by it. Then the four ribbons would each be driven by a channel from the matched pair of M-1.0ts that I have sitting here doing nothing. (I say "matched" because they are both the same variant of the M-1.0t; the earlier, "inverting" type, which has a different input sensitivity, for one thing).

Sounds simple enough, but wait. First, electronic crossovers are needed. There is a local company here in Rochester (Marchand - Google it) that will sell kit-form two-way units, any frequency you want, for $25 a channel, BYO power supply. 24 dB/octave; high-grade parts. I'd need three of those, and some advice on the selection of the best cutoff frequency; then balance it up.

OK, but what about the ribbon peak (is it 6 kHz in the Silvers? or 7k?)? Need to add the right notch filter there, or get Marchand to do it. What about the Gundry dip that was built into most of Bob's crossovers? How to phase the woofers; straight up with the ribbons, or inverted, the way the factory did it early on? How to wire the woofers? I think by themselves they measure about one Ohm or less on a DC meter. Three in parallel, the way they are now, with no passive-crossover components in series - what impedance is that amp looking at? And the center channel has six! Even now, I run the two center Silvers in series.

So you see, I have more questions as answers. No doubt somewhere, somebody has already gone through this. Any advice they could give would be welcome, even if it's "forget it".

Robert R

Damn, I've got a headache.




















































Seriously Robert, I think it would be easier to match the crossovers than all that other stuff and as an added bonus, you'll probably get to keep your sanity.

Robert, I plan to publish Bob's answer to me on the ribbon peak fix but I've been to busy lately....I'll try to get it up here by the weekend.

Here's the simplified version below, shown with the AL-III shaping surround. Bob said to use leading/trailing edge balsa wing pieces from a model airplane shop for parts, and shape to fit. He said the point in the middle doesn't need to be as sharp as I showed it (i.e., you could round it off).

The red areas show where you need to supplement the waveform guide on the ribbons to tame the resonance peak that's @ 7,000 hz. If you look at the new Sunfire Cinema Ribbons, you'll see much the same shaping of the waveform guide. According to Bob, that is the best way to correct the resonance.

I begin to agree with F1nut that it might be easier to just wind some coils and match the crossovers. But I'm reluctant to agree with his rash assumption that I have any sanity.

As to the notch filters, I never imagined a non-electronic approach. That mechanical stuff looks too tricky for me to do (wood and computers hate me), and this is not an ALIII, so it might even have to be re-engineered. Still, it's a possibility to keep in mind. But surely the correct little LCR network in series in the crossover would do the job, just as it does in the stock crossovers, but I can't engineer it myself - don't know enough there, either. You have to first know the exact frequency to go for, and the degree and sharpness of attenuation (the shape of the curve); then how to calculate the values of maybe three parts to achieve that. Once there, there's nothing to it.

Just hope that somebody has already been down the same road and filled some of the potholes for those that follow. Just as long as they didn't fill the potholes with horses#!t.

RobertR

As to the notch filters, I never imagined a non-electronic approach. That mechanical stuff looks too tricky for me to do (wood and computers hate me), and this is not an ALIII, so it might even have to be re-engineered.

RobertR

ALL ribbons have the resonance.

My understanding was that the peak (or some peak) was an effect of the cabinet, due to the notch the ribbon resides in. But I could be wrong on that one, or maybe the review or whatever I saw it in was BS. Or maybe there are two peaks; certainly the ribbon must have a resonance. I never paid attention these things before, when I had one pair. There was no need - I just played 'em. Then got into trinaural, and it got crazy. Now I have three pairs, all different crossover models, and I have to learn all I can.

RobertR

Sorry to ressurect this one, but does anybody have any information regarding how the ribbon and woofer sections operate independently? Will they still both be operating at 8 ohms?

Also, can anybody attest to biamping the Amazing Silvers? I fully understand the benefits of active biamping and am a proponent of doing so, but there are "exceptions" i,e. speakers that just don't want to be actively biamped becuase the passive crossover was solving other issues involving impedance matching or what have you. My AR9's are a perfect example of this.

Are there any such issues with the Amazing Silvers, beyond the 7Khz resonance?

There are lots of issues here. You can separate the crossovers and run the woofers with one amp and the ribbon with another, and let the crossovers "do their thing". Bi-amping, but not getting the most out of your amps. You can add and active crossover in front of the two amps and do better (that's what I do with my AL-IIIs. You can rip out the crossover (or part of it) and go directly to the speakers. I plan on bypassing the woofer part of the crossover when I replace woofers in my AL-IIIs, and changing the crossover point on the active crossover up to 200 Hz). But with the ribbon, there is still the notch that needs treatment. One solution is to get a parametric equalizer, which allows you to dial in the frequency, depth and width of the cut/boost you want (ideal, and a fixed version was done for this with the early Clearviews). But the easiest is just to separate the crossovers and run with them in (with an active crossover). This is what Clearview did for their later models.