Using the ART 351 EQ and the SVS 20-39CS sub ? (1 Viewer)

I've asked SVS tech support about using an EQ with my SVS sub but I also wanted to hear other people's opinions. I finally purchased the ART 351 EQ and could anyone offer some advice on how to effectively use my EQ to get better bass ? How do I find and eliminate 'spikes' and 'nulls' from my system ?
I've never used an EQ before but I've heard
some benefits could be attained if the EQ is used properly.
My system is mostly used for home theater. The sub is also calibrated at 5-6 db over the main channels. Currently, I have a 6 db boost at 31.5 hz which works great for movies despite the decreased headroom. I like watching movies with the volume at moderate levels which would probably explain why I haven't heard the sub clip or bottom out so it's working fine so far.

One way is to get a Radio Shack SPL meter(the analog one) and a Low Frequency sweep CD(for example Stereophile Test CD). Then play the sweeps and write down the dB value at all of the frequencies and adjust your EQ accordingly. Setting it by ear will not give you accurate results. Also remember that the SPL meter readings for low frequencies are not exactly spot on with the RS SPL meter. There is an adjustment(you have to add upto 6dB to the reading at certain low frequencies) that I am sure someone else will direct you to.

Here is a link for the " http://members.tripod.com/~terryctheater/shivaphotoalbum/page11.html
Sean
edit
'cause I can't spell...
[Edited last by Sean Parque on September 06, 2001 at 09:56 PM]

Samson-
Before you start tweaking the modes and nulls, set the high-pass filter cutoff. Play a 20hz tone so it reads something low like 70db on your RS meter. Then turn the knob until it slightly drops (-0.5db), then turn it back very carefully till the drop goes away. That sets the high-pass to filter just below 20hz without affecting above that frequency. The markings on the unit itself are utterly wrong. For me, it reads about 12hz where the right setting actually is for 20hz.
Why do all this? Ported subs have massive excursion below their tuning points. If you filter that out (under 20hz for 20-39) then you take away the signals which get you very little output but waste tons of the useable excursion.
Once mine was set for this cutoff, I never heard my sub bottom out again, even when listening to Toy Story 2 or the Haunting at reference levels.
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My Home Theater Page

Thanks for all the responses.

Where do you buy a disc that has the 20 hz tone ? Does the Avia disc have it ?

Go to http://www.stryke.com/testcd1.htm
I tried it and it's very informative.
Sean

Instead of starting a new thread, I'll tack my stuff on here:
I originally sent this to TV @ SVS, but I realized that I should have just asked here instead...
I finally got a sweep disc and wanted to see how I was with placement of my twin SVS 20-39's. Here are my readings....
Hz--RS SPLMeter-Correction for Inaccurate Meter-Actual
20--82----------+7.5----------------------------89.5
25--90----------+5------------------------------95
32--91.2--------+3------------------------------94.2
40--97----------+2.5----------------------------99.5
50--90----------+1.5----------------------------91.5
63--79.5--------+1.5----------------------------81
80--81.5--------+1.5----------------------------83
Meter corrections were taken from this page.
I put the meter on a tripod at the listening position and pointed almost straight to the ceiling. I played each test tone and recorded the readings and then adjusted for the low freq inaccuracies of the RS SPL meter.
As you can see, if I've done this correctly, I've got a dip at 63Hz to 81dB's all the way up to 99.5dB's at 40Hz. I'm hope that I did it wrong cause that's nasty!
My Onk 696's volume display doesn't have the standard -80 to 0dB display. Instead it shows 0 to 80. I doubt that the 80 mark is reference since that's max volume. With that in mind, I just put the volume at 30 for all tests (The whole system was calibrated before hand with VE). I would assume that I just pick the middle of the road, which in this case is about the 20Hz mark and adjust the EQ from there? I know that using the EQ in this way with the amount of problems I seem to have would rob me of tons of power. Moving the sub around would be a better way to go, but unfortunately I don't have that luxury.
Basically, I just wanted to make sure I'm going about this correctly because after I took my readings to the EQ and made the appropriate adjustments, I re-tested with the sweep disc and recorded the dB's of each tone. Again, correcting for the meter inaccuracies, I came up with a new EQ corrected SPL for each freq and the results were....um, bad. The response was still all over the place. I must have done something wrong
Please impart your wisdom....
Sean

Yes, the AVIA disc has a low freq sweeps down to 20 Hz. It actually has separate sweeps for each of the main channels (left, center, right, left surround, right surround) so you can check the low frequency response for each channel independently.
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Guy Kuo
Link Removed
Ovation Software, the Home of AVIA DVD

Sean,
You neglected to tell us what kind of equalizer you are using, what the cutoff frequency and slope of your crossover is, etc.
Since you are using 1/3 octave test tones, and you said that response after EQing was still all over the place, I’m going to assume you have a 1/3 octave equalizer. Too bad, because this would be easier with a parametric EQ.
First, you have to realize that the goal is not to achieve flat response. You want a gradual slope from the higher frequencies upward to the lowest.
The second thing you have to know that moving any slider affects not only that frequency, but to some extent adjacent frequencies as well.
Basically you have one seriously offending frequency, 40Hz, so cut it by about 4dB. This will probably also cause a measured loss of at least 1dB with the adjacent frequencies, 32 and 50Hz.
Let’s concentrate on 40Hz and below first. After cutting it by 4dB, your 40/32/25Hz readings should be 95/93/95dB. You should be able to boost 32Hz by 1dB and not affect the adjacent frequencies, so then your readings should be 95/94/95dB. This is acceptable response.
Now the frequencies 40Hz and above. After the 4dB cut at 40Hz, the readings for 80/63/50/40Hz should be something like 83/81/90/95dB. As you can see, the frequencies above 40Hz drop significantly, with the big problem being the 9dB drop between 63 and 50Hz. Try dialing in a 6 or 7dB boost at 63Hz. This should change the 80/63/50 Hz readings to something like 84/87/92.
Get the picture? You’re taking care of the 63Hz hole, and at the same time dragging up the frequencies on either side of it (without moving those sliders), to get them all closer to where the numbers below 40Hz are.
So, after these two adjustments, your reading should be something like 84/87/92/95/94/95/89.5. The 5dB “shelf” situation you have at this point between 50 and 40Hz, with relatively flat response on both sides of it, is a situation that is virtually impossible to fix with an equalizer. You might try boosting 63Hz another dB or two, but that will be risky. It may do more harm than good; let your ears be the judge.
In any event, you now have basically a smooth rise from 80 to 40Hz, where it levels off to 25Hz. (In my experience, continuing the rise upward from 40 to 25Hz results in a lot of unpleasant and annoying subsonic energy in both music and video programs.) You should find this curve to sound very good, a noticeable improvement over unequalized response.
Good Luck,
Wayne
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My Equipment List

Wayne,
Thanks mucho for the info. Now I understand a bit better how this works (I'm a bit out of my league with this stuff, but it's the only way I'll learn).
I'll try what you suggested and report back here.
Sorry I was not more specific on the EQ, it's the same one listed in the subject line; the ART351. The sub is crossed at 80 within the Onkyo 696. I checked Onk's web site as well as the manual, but I was unable to locate the slope
Sean