Stereo Subs and a plan

[AndrewM]

Everybody,

Looking for some thoughts on stereo subs, or maybe just 2 mono subs (placed with the mains).

I still haven't done to much with the Aria 7 TLR kit I picked up so long ago, but I'm getting close (have just one more project for the house).

Anyways, I was looking over the specs of the new Parts Express 12" Titanic MK2 and they are saying you get a nice mid-low Q design in 2cu/ft. When I model it in WinISD (don't have Unibox here at home yet) it models almost identical to my Tempest (but with a much smaller box). And since I'm quite happy with the performance of my Tempest that would do nicely.

So I'm thinking of dropping a pair of these into 4-5cu/ft on each side and then putting the Aria-7's on top of them and then get rid of my Tempest (or move it somewhere else). Power them with my 250W PE sub amp and have them wired for 4Ohm's (would be very effecient). But I'm curious about the effects of having a pair of subs like that.

Any ideas/experience with a setup like that?

Regards
Andrew

[ThomasW]

The new Titanic drivers look very promising. A word of caution though. I'd recommend checking with Paul @PE regarding the amp. Most of the new generation of high excursion drivers need cubic levels of horsepower to get them up and running.

Also stereo subs can create issues with placement. So be prepared to move them around if lots of standing waves occur.




theAudioWorx
Klone-Audio

[AndrewM]

Well, I modeled the whole thing in Unibox, and the wimpy little 250W amp is capable of pushing out a modest 117db (so says Unibox), when I model my Tempest with the same amp it says 113db max (and running into excursion limits anyways). But more power would probably be better (or I have some room to EQ the bottom up a little if I wanted to, get some more extension instead of SPL).

Is there any way possible to predict the room response of stereo subs? Placement would be kind of tricky if I try and build the whole thing as a set. My 281's Vented are good to the mid/low 30's and sound very good without a sub (just missing some extension) and sound very good where they are placed, the new speakers would be placed almost edentical to where the 281's are at. So am I assuming to much by thinking that the performance would be similiar but with a little more extension on the low end? Or does that last half octave create some trouble?

Andrew

[JonMarsh]

Thomas's caveat is well placed.

One other point to consider, is that optimum sub placement (for smoothest distributed frequency response over the largest area possible in the room) may require "unusual" placement- not aligned with the placement of the mains. SGHT had a good article about his investigating it with simulation and measurements, (in their HT architect series) and showed that optimum has one sub in the front, one to the side, and one in the rear. Even for two subs, one in front and one to the side was best.

Regards,

Jon




Earth First!
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We'll screw up the other planets later....

[Lex]

Well, you might save yourself some trouble, since LFE is basically non-directional by naturer. So in stereo, recognizing shifts from left to right on LFE material won't normally be obvious. Sure, you should get the occasional feeling of direction. I just don't think it will be that often.

Lex

[ThomasW]

I wouldn't trust the any of the computer sims to accurately model the output of the new generation of high excursion subs. What we've found is that even the efficiency from the T/S parameters isn't a good predictor of how efficient they'll be in a enclosure.

I know the Adire 281 go low, but I suggest using a 60Hx-80Hz XO point

RPG Acoustics makes a nice program for modeling speaker performance in room, if the room is a rectangle. If the room is asymetrical then use ETF 5.0. Either of these can be easily found with a google search




theAudioWorx
Klone-Audio

[Bruce]

Anybody tried out the CARA 2.0 room placement prediction software yet?

CARA

I have ETF5 measurement software with a calibrated mic and preamp, but since my room is quite irregular, the RPG prediction software is quite useless.

Bruce




Bruce
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[AndrewM]

Well power wise I'm not to concerned, there's lots of options on that front (and for reasonable prices). And I'm not concerned about hitting ear bleeding SPL levels (I usually watch movies in the - 15-20db range when I'm properly calibrated)

But I'm still a little confused about the placement thing. If somebody had a pair of full range speakers (say capable of giving fairly flat response into the mid 20Hz range in room), would they still run into these problems? I know a lot of audiophiles "poo-poo" the idea of subs and go for full range speakers...now they don't hit the lows like you do in a HT (unless you listen to organ music).

I was actually looking at the room acoustic software since my room is entirely to alive and was looking into doing some treatments as well.

Andrew

[Bruce]

Andrew,

My understanding and experince with the ETF5 measuring software (for mains + sub integration) has shown that when you get two drivers trying to produce some of the same frequencies from two different positions in the room you get wildly varying results (i.e. two full range speakers, or mains + subs) .

This situation produces standing waves that cause frequency cancellations (nulls) and peaks that are even more severe. This is one of the risks of stereo subs. Which means placement is everything and almost impossible without some kind of measurement software like ETF5.




Bruce
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