[warrensomebody]

Wayne A. Pflughaupt wrote:

Hi Warren

Welcome to the Forum! I’ll chime in on some of this.

Hi Wayne,

I really appreciate all the prompt replies from you guys. This forum is great.

Not sure I follow. Anyone with a subwoofer technically has a bi-amped system. Or did you mean your Pipedreams are bi-amped?

I guess what I meant was that the Pipedreams system uses an active crossover, so in order to do room correction on both the bottom end and top end, I was thinking I would need 2 parametric EQ units. But now I realize that (a) I could probably just put a single EQ upstream from the crossover, or (b) I could do what I already said I had been experimenting with -- removing the active crossover in favor of just having the Lexicon perform the crossover duties.

Something is really fishy here. I can’t imagine a pair of 18” subs that can barely get below 30 Hz. If they aren’t in drastically undersized boxes, it looks like some placement experimentation is in order. If they are not co-located, that could be dragging down extension, too. Wait a minute, that doesn't sound right! I mean it's costing you extension.

Yes, I see that something really is fishy now. That last graph I put together was a real eye opener (the one with the yellow line). I hadn't really looked at or thought about that nearfield response very carefully, but now I see that my bass response begins falling off at frequencies below ~63hz with almost the same slope as above 63hz. I can't imagine what might be doing that, but I'll play around with different equipment (or see if there's some filter setting in the preamp that's accidently in effect) once I get back.

brucek mentioned the situation using a cheapie EQ with a system like yours, but since your pre-amp is digital, the DEQ2496 might work for you, since it had S/PDIF ins and outs. If your pre-amp has the right connections to accommodate the DEQ, you might be able to use it without the extra DA/AD conversions.

Cool idea. I believe it has S/PDIF in and out, so I'll investigate this solution. It would be great to avoid the extra DA/AD conversions.

BTW, what do people think about this Behringer gear's digital performance, e.g. DAC linearity, jitter, etc. I know I probably should expect much given the price range, but on the other hand, all this digital equipment has gotten amazingly good over the past few years. Just curious -- I'm pretty convinced from what I've seen here that its benefits far outweight these concerns.

Personally I would use 1-octave smoothing for evaluating the mains. Otherwise response just looks too scary and needlessly freaks people out. (For equalizing purposes, I actually prefer my old-fashioned 1/3-octave real time analyzer!)

Does the Lexicon have any provisions for manually tweaking its equalization? If so, that’s all you need, not any outboard equalizer. With 1-octave smoothing, you can easily identify any general irregularities you might have. You don’t want to be chasing every little jagged irregularity – you can’t hear those anyway, but broad ones, you can.

The Lexicon doesn't provide much for manual tweaking beyond tone control and a tilt compensation across the frequency spectrum.

In your top-post graph, for instance, a couple of 1/6-octave filters might make some audible improvements for the peaks at 300 and 450 Hz. (If there is no audible improvement [often best noted with pink noise], then don’t use the filters there!)

I'll need to get my hands on one of the Behringer units and see what things sound like with tweaks in that region. I'm not sure what flat pink noise vs pink noise with frequency humps will sound like, but hopefully it will be obvious which one sounds right.

And especially the broad section between 2-15 kHz. Yes, I know, the upper frequencies are sagging because of the Radio Shack meter. But let’s pretend that was your actual, true response, for the sake of this discussion. Flattening that broad area by a few dB with a wide filter would bring a noticeable improvement.

Or, let’s say that your true response doesn’t sag at the top, but is flat from 7 kHz out to 20 kHz. In that case, your upper end would be a bit hot, so a basic shelving filter to reduce that area would make an improvement.

Makes sense.

The thing to keep in mind with EQing the mains is that it’s totally different from EQing the subs. With the subs you want to eliminate as many peaks and valleys as you can, and we often apply numerous finely-tuned filters below 100 Hz to accomplish it. By contrast, with the mains it’s more of a “general” thing than surgical precision. You don’t want to chase every little irregularity – it’ll sound like when you’re finished.

I see. Is that because people have better ability to distinguish resolution at the lower frequencies, or some other reason?

Probably not the best tact. Look at your first graph, for instance. Disallowing 20 Hz, your lowest points are hitting about 60 dB. Your highest peaks are hitting about 78 dB. That would be an 18 dB gain reduction in your signal. You might end up with the signal so low that it won’t drive your sub amp to its maximum output. For instance, if your sub amp has output meters, and they only hit half-way up with the amp’s gain all the way up, your amp isn’t delivering its maximum power output.

I guess that makes sense. I get a little confused between the effects of diminished headroom (SNR?) and the ability to compensate with available output power of the amps driving the subs. I mean if I have a 400wpc amp driving the subs, do I have twice as much headroom to play with as a 200wpc amp?

For home theater, we generally recommend running the main speakers set for “small.” If they’re set to “large,” and you have speakers with a lot of bass output, that’s not good. For one thing, if you intend to EQ the subs, you have a problem: The mains will have the same bass peaks and valleys the sub does. But the bass the mains are putting out will not be equalized, so it will negate any equalizing you’ve done to the sub.

I assume that "small" and "large" relates to the high-pass frequency of the mains crossover. With the Lexicon, you get to set this as a frequency, so I have mine set to 80hz since the sub's low-pass freq is 80hz. Is that "small" enough, or are you suggesting picking an even higher frequency?

I know folks who have highly-capable main speakers feel they’re “not using their speaker’s full potential” when they roll the lows out of them, the price for utilizing that capability is very often inferior bass performance.


Well, my insight would be that the Lexicon can’t equalize subs as well as the BFD 1124 can. Better keep it to the mains, if that’s possible.

Well, I can see that it can't! If only I had discovered this forum a few months ago, before my last upgrade. :-)

Regards,
Wayne

Thanks Wayne. I really appreciate your help.

Warren