Axiom Home Page Forums General Discussion Technical Questions Video from Ian setting up multiple subwoofers.

http://youtube.com/watch?v=ayOXz26qm3I

I was interested to hear that he is not a fan of EQ in addition to multiple subs. Maybe I jumped the gun on my SMS-1?

Cool, thanks for the link. I would have liked his opinion on mixing and matching different subwoofers.

I'm glad I don't have that problem. All my viewers are seated along the 600 driver's normal. With big theatres come big expenses. Now you need at least three 600s and a 1400 .

I wouldn't think it would be a good idea to mix DSP-based subs with non-DSP-based subs. Or even DSP-based subs that utilize FIR vs. IIR filters due to different time delays between them.

Alright, you'll have to explain what FIR and IIR are.

I think his point was more specific to the idea that an equalizer can only setup the room response for a limited area "the sweet spot".
So along those lines, unless you are single male who watches alot of lone videos in a room with a single chair, then what's the point?
Optimize one spot, possibly worsen others around it.

People can add all sorts of doo dads to their rooms, treatments and such, but ultimately, you will never make every room seat experience the same response. It is a fight one cannot win.
I keep seeing people try though.
Spending tons of bucks to do it.
Spend the cash on some real wood veneer units instead and for once, try to enjoy the system.
I swear some people take more time to tweak than to actually listen to the damn thing.

That's my Newcastle Brown rant for the afternoon.

Good video Ian.
8 minutes of quality thoughts. Next time you should be waving your arms around more when you talk like a crazy Frenchman (yes i am part French and yes i have many French friends who do this all the time).
I love animations.

Finite Impulse Response vs. Infinite Impulse Response. IIR filters utilize feedback while FIR filters don't. If you put a string of 1s followed by 0s into an IIR filter, the output will keep on ringing (hence infinite). A FIR filter on the other hand eventually decays to 0 (hence finite). In practice, both decay to zero but FIRs decay faster than IIRs.

IIR filters are typically preferred in cost-sensitive applications because they usually require less memory to implement. But FIRs offer calculation advantages. FIRs can also be designed with steeper slopes than IIRs. Next generation electricity revenue meters for example will incorporate simple DSPs for computing various power and energy parameters but the meter business is extremely cost-sensitive. Engineers will most likely choose IIR filters to lower memory usage but they'll be pulling their hair out to do what they could with FIRs very easily.

Now you're going to ask me which is better for audio and I'd have to tell you that FIR theoretically offers higher performance but whether the FIR/IIR difference is audible or not is beyond my area of expertise. Also, it depends on the design. A junior can botch a FIR filter and a senior can work magic with an IIR filter. If anyone knows, chime in.

There's a subliminal message in there "Buy more subwoofers! Buy more subwoofers!"

So...who's going to shell out the dough for 4 EP600's?

Hey, I'll get there eventually. If there's one thing I'm good at, it's spending my money.

Very good video though I would add three points of clarification.

1. when adding multiple subwoofer maximum gain is as follows, with 2 subs 6db, with 3 subs 9db and with 4 subs 12 db. In practice because of room issues the maximum gain is never reached unless the subs are co-located.

2, getting phase between the multiple subs and the speakers is trickier said than done. The best way to get it right is if you have the benefit of a visual display of frequency response, something which you get with REW or and SMS-1. Only then can you see the immediate impact of switching phase among the subs.

3. Equalization is a last resort after palcement and room treatments. However I suggest it is much more beneficial in a multiple sub setup than in a single sub setup which only optimizes the sweet spot. Some room nodes can only be cured with modest equalization. Problems occur from ringing when too much equalization is added or from reducing the efficiency of the amp by adding boosts.

I have the SMS-1 with the EP500 and I'm happy with the results. Granted tho, I live alone and don't have as many different seating positions as in your theatre room, and I haven't tried the SMS-1 mike in different positions other than the middle of my couch. Have you tried different mike positions to see if the FR curve is significantly different, and considered whether subsequently purchasing 1 to 3 more Axiom DSP subs would worth the money?

If ya got the cash, I'd say do it! We all love this hobby and if you're looking to further your sonic experience... I'm with you! Having followed your posts over these many months, however, I dare say you're at (or...past?) the point of diminishing returns for your $$$.. If you find that you hear a significant difference in various seating positions after the use of the SMS-1, then ignore my post and dive in! Just offering a friendly suggestion..

Randy get another sub.

I think it is moe of a love/hate relationship. I love all the toys and wonderfull sound, but hate what it does to my bank account!

Yep... seems as though we're all "addicted" to some degree. I admit I've thought of adding a second sub myself.... I just need...one....more....fix.... AHHH!

Thanks John for the support.