Axiom Home Page Forums General Discussion Advice from Axiom Owners multiple subs

Just finished building my dedicated theater. Dimensions are 17L X 12W x 7.5H. Current configuration is:

Denon 3806
Paradigm bipolars for front
CSW center
Axiom QS4 surrounds x 4
Paradigm PS1000 sub (here's the rub)

After finishing, and placing sub in several different locations in the room, I feel like the sub is very localized. To me it seems like I can pick out where the sub is no matter the placement. It's probably just me because maybe I'm looking for sub placement? Not sure.

I was thinking about moving to multiple subs to try and offset this. I would like opinions as to whether I should go with two smaller subs or stay the same size I have now? The PS1000 is 10" driver with I believe a 250W amp.

Thanks

What's your crossover? You may also be running the sub too hot. Have you calibrated?

Have the crossover set at 80HZ. With the Denon I'm running the subwoofer as LFE+ main, with the fronts set to large.

I have not calibrated as I don't know where to begin to calibrate. What equipment is needed etc.

It's not that the sub doesn't sound good for movies, just seems to me to be localized.

You'd need an SPL meter to test the sub's gain against the speakers.

Here's an example of one:

link

That's a start, but what would I be looking for? Is the SPL for each speaker supposed to be the same? Sub higher than surrounds. Sorry for the newb questions, but a guy has to learn somewhere.

After reading a couple of other threads, it seems I should be setting my fronts to small, and change the LFE+main to just LFE. Is this correct?

As far as the multiple subs go, ideally you'd want the same subs. If not, it's not a giant problem. I run three subs--one 12" ported, and two 10" sealed. Probably not the greatest mix, but it's what I have. Having three really evens out the response in my room as well as making the low frequencies less localizable.

If HT is your thing, I wouldn't go smaller than 10". The smaller you go, the less extension you'll have.

Yes, each speaker should be calibrated evenly. Personal preference may dictate bumping up a channel to what you prefer. It's all highly tweakable--which is good and bad. Good because you can set things up exactly how you want, and bad, especially for the newcomer, because there are too many variables.

To start out, keep things simple. Set all speakers to small and let the sub handle the low frequencies. Play test tones through each speaker while holding the SPL meter and make sure each channel measures the same.

Patience is the key. Dialing in a sub can be tedious. Just set some time aside and methodically go through different options until you find the one that works for you.

thanks everyone, I'm off to Radio Shack.

Try changing your fronts to small and change the denon to LFE instead of LFE+main

Just did that and seems better.

When trying to calibrate a sub by ear a person will most times have the sub about +10db to hot. As far as the sub is concerned this is your problem, you will need to calibrate the sub to get it right..

Then after spending several hours, days or sometimes weeks of getting it calibrated and dialed in to a 'T' with the spiffy SPL meter ... we'll invariably reach back there and crank it up just a notch or two the first time a movie comes along with what we believe are not enough LFEs to suit our needs. Problem solved.

A lot of folks do set their subs a bit hot, normally around +3db for movies.

Wid, glad you brought back your VU meter, I was getting worried man, that is classic and all Wid.

Lately I calibrated all of my subs/speakers to 78dB's. When all subs are turned on, I get an average of 83dB's or 5dB's higher than the other speakers, seems to work well for me.

I use a +6db hard-knee house curve on my subs and that works for me too.

Gotta have the meter

Went out last night and bought an SPL meter. Came home and set everything up at 70dB. Not sure if I did this correctly or not so I want to throw it out.

Set the SPL for 70 (radio shack digital). Set all speakers as close to 70 as I could (a couple of speakers were fluctuating b/w 70 and 71. With Denon 3806 could set speaker level individually. Everything sounded good but the sub. Seemed way too loud and boomy. Scaled that back to about 64 and seemed to blend in much better. Also didn't seem so localized.

So.....did I perform this test correctly? Never used an SPL before.

You seem to have deep placement issues causing some frequencies to be much louder and some much lower. The pink noise being the sum of many frequencies, it is just a guide. Try the tones from the following link (with your SPL meeter).

http://www.realtraps.com/test-cd.htm

That might give you a more accurate picture of what is really happening with low-frequencies in your appt/house and also a more precise tools to see exactly how moving subs and furniture around (and also playing with x-over) will influence/improve things.

But you made the best first move: get an SPL meeter! Now the fun begins!

You certainly did the channels right, but Eric's probably on point here--you need to move your sub.

Thanks for the link. I have moved my sub down to a side wall just behind the main seating area and lowered the volume a bit. The bass has leveled out and is matching much better as a whole. There doesn't seem to be as much localization as before. I am still thinking of a second sub to help smooth out peaks and nulls more.

Thanks to all that have helped. Hope to someday return the favor.

gja, glad you got things figured out. While corner placement is generally preferred, I moved my primary sub a third of the way down a side wall. By itself, I got better measurements vs. the corner. Subsequently I added two more subs to get an even better in room response. Plus, I've always felt one sub to be somewhat localizable.

There are so many variable in sub placement it can drive a person mad!

Sorry to bring this topic back to life, but I have more questions.

I have a relativley small theater room (11.5w X 17l x 7.5h). Would I benefit from a second sub, or just get a "better" single sub? What I mean is I have a Paradigm PS1000 (10" older model), Would I benefit more from another 10" or go with a single larger sub 12-15" ?

Why not both?

I suspect (although I have one sub and only expect to have one sub for the foreseeable future), you still would benefit from the smoothing inherent in using two subs. I'm not certain whether you should have similar subs to do that or not.

From what I have researched so far, "they say" one should have similar subs, easier to calibrate etc. I was just wondering if I would benefit with such a small theater and two subs.

Is that room closed in or is it open to more space? If it is open to more space, then you could see a pretty good improvement going to a bigger driver. Although a dual system does give you a 3db increase in SPL to go along with a smoothing of the bass through out the room, which would be noticeable .

My room isn't much bigger, 14x20x8.5 and I do feel the room benefited quite a bit from 2 subs. My primary sub is the EP-600 and the secondary is also a 12" sub, but it is in a box easily 1/4 as small as the 600. The FR of the second sub also isn't nearly as low as the 600, nor does it play as loud, however, I feel it has helped to smooth response in the room.

This is more noticeable when sitting in spots other than the primary listening position, so it is _not_ something I notice in most situations. The 600 sounds just fine to be by itself when I'm sitting in my main listening position (as I positioned the 600 to sound best there). So in my case the added volume wasn't the main reason for putting the 2nd sub in, it was more for smoothed response. If I hadn't already owned the smaller sub I probably would not have gone out and purchased a second sub for my room, but given that I had it already, I felt it was better to include it in the setup than not.

Completely closed off from the rest of the house. I may try to find a used 10" for short change to try it out. If it works out well, I'll then start with the upgrades to better subs.