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In Reply to: RE: EQ and subs - preliminary results posted by bartc on January 02, 2009 at 07:30:57
I use a similar solution for the modest HT system. In that space where I have little ability to experiment with placement, I had 12 db peaks at 63 and 120 hz with smaller dips at 80 and 100 hz. Since it is a ported design, a tad of boost near its low end cut off of 30 hz helped as well. Measured and audible results are far better. I did, however, have to run the EQ off a cheater plug because it introduced a ground loop.
Because the upper peak is beyond the *usual* range where subs are added (say 60-80hz), I got the best results by moving the high pass for the mains and the low pass on the subs upward to 120 hz so that they can be part of the equalized solution.
rw
Follow Ups:
Did you turn your sub's x-over to 120 Hz? I never tried experimenting in the opposite direction by going up, rather than down, the spectrun. All advice I'd seen suggested to keep the x-over as low as possible, which is where I ended up.
My cheap KLH sub does facilitate better integration by permitting output viat the sub's x-over to the main speakers. Thus, cutting off the bottom of the mains at the x-over point and the top of the subs, with some overlapping range. But that would mean pumping the mains through the cheap sub plate amp with all its distortion, and that made no sense to me under the circumstances. If the sub had a really good amp, then maybe I would have done that, but that's not the case at all.
FYI, I am dedicated to 2 channel music only and not at all interested in nor seeking future HT setup. Not snobbish, just not my cup of tea, and at the current market prices make that hemlock tea! LOL
Where the subs still have some response above that cutoff. After MUCH experimentation, I found that approach ended up with the flattest overall measured response. I too, began with a far lower setting and could never get the third octave smooth. Which also has the benefit of balancing the power burden more towards the 120 watt subs vs. the 100 watt mains. The mains still clip first.
...that would mean pumping the mains through the cheap sub plate amp with all its distortion...
I hear you. In my case, the NAD T755 receiver has its own variable high pass filter for the mains. I run the subs directly from the LFE outs. Which meant I had four sets of variables: mains high pass frequency, subs low pass frequency, subs level and LFE level. I balanced the results with the LFE level set very low for the flattest response so that I could always crank it with the remote if needed.
I'm now convinced that having at least a bi-amplified arrangement using equalized subs is a great way to go. At least when one does not have great placement latitude and a forest of bass traps as I do in the music system. :)
rw
My NAD C740 receiver does not have any X-over built in. It's strictly classic 2 channel music. In fact, it doesn't have a sub out line level either, so I use silver Ys between pre and amp to do that duty.
Not sure your approach would work at all in my situation, unfortunately.
The NAD does a fine job with the VR1s; the KLH plate amp even publishes its specs as having 10% THD at 120 W and only about 1% THD at best down at 100W, so I'm not impressed with the idea of using its circuitry on the mains.
Also - and here's where my theoretical approach may be way off base -- I figure that the sub is the weak link in my speakers, being an el cheapo. By comparison, the VR1s are very well made and voiced and reach accurately (at least to my ear) down into the 40Hz range without stress. So I wouldn't want to swap the upper bass and mids of the great VR1s for the probably crappy ones of the KLH. That makes your solution improbable for me.
Given the factors you mentioned, it seems the subs are used to extend the bottom octave. The value to me for running an equalizer is to address room modes. Such usually requires correction out to 120 hz or so.
rw
What we're all fighting with EQ is both the characteristics of the speakers AND the room nodes. Just depends on which is your main emphasis.
Obviously some of my original and remaining problems aren't simply the repro characteristics on the freq spectrum of the sub or mains. Some of them must be room issues in the bass quadrant, and Richard's general postulation of about 3-4 characteristic freq problems for most folks in the sub range is really the room issue generalized.
That suckout at 110 Hz in my room is undoubtedly a room issue remaining, though I haven't tested to see if it improves outside of my chosen seating position.
In some ways I've been fortunate with my room, which isn't technically even a classic rectangle (due to open hall system it feeds into on one side, 2 levels of height, half wall, etc.). It appears from some room calculators that my seating position, my reverse placement (I have my speakers on the short axis across from me), room dimensions overall, actually aren't too bad compared to many standard rectangular situations. And in practice, I'd say it's workable so far using acoustical tricks and working within limited placement. So I'm not concentrating in the direction you are at this point.
I just want to hear the initial pluck of a bass mated to the follow on twang of the strings, the resonance of the wooden box, and the decay as realisticaly as possible. Same for percussion, with which I'm highly familiar. A drum doesn't simply THUMP. And it doesn't hurt to hear the human voice with its depth correctly protrayed either!
Ah well, the drive to perfection will drive you nuts, and in my impoverished case, nuts all the way to the poorhouse... LOL
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