Behringer vs. QSC

[bkolfo4]

I am finally moving over to the world of IB after years of large ported and sealed home subs.

At this point, as soon as I sell my last Avalanche 15's, I am thinking about doing (8) Fi IB3 18's on the front wall of my new HT.

I currently own a QSC PLX3402, but was thinking of selling it to try a pair of EP2500s. . .good idea, or bad idea?

It seems as though the EP2500 will not make rated power, but I have read mixed reports of the actual output of the PLX3402.

Brian

[ThomasW]

I'd try the QSC....then make the decision.

[bkolfo4]

That was my plan at first, guess I will go back to it.

Do you still surf any other forums? I remember seeing your name everywhere a few years ago, but do not see it as much now.

I forgot about this forum until Scott reminded me. . .

My plan is to do two columns of (4) 18's or 22's on each side of my screen in the new HT. The speakers in this HT are not going to be stealth - I want to see everything!!!!

[jimcant]

So do I ;D

I hope that wall of yours is strong
It is going to need to be.

Cheers
Jim.

[chrisbee]

8 x 18" drivers arranged in vertical arrays?

I wouldn't worry. The house will do all the moving while the drivers sit still.

This is a job for Readymixman! ;D

[bkolfo4]

I am thinking a 2x6 wall with multiple layers of MDF and 2x4 bracing between drivers?

I am no stranger to making strong walls. . .

[chrisbee]

Sorry, I had no idea you were a bricklayer or master mason.

I'm thinking a solid 9" wall in engineering bricks with heavy, push pull-struts bolted back to a good strong basement wall behind the false wall.

Too fussy? What about a foot thick, free standing, cast concrete wall with minimal sized, flanged cut-outs for fitting heavy sub baffles for individual drivers?

Something lighter? 12" x 2" vertical and horizontal studs using halving joints at suitable spacing to allow an 18" driver to fit on a small baffle? Covered both sides with 3/4" Baltic plywood for a stressed skin, box framed core, sandwich construction.

Two words: Reaction forces.

Be very afraid! ;D

[jimcant]

Is that array of subs fitted in a vehicle/van of some description?
It looks very impressive.

No problem with satisfactory SPL's, I should imagine

[bkolfo4]

Yes. . .1992 Astro Van

(6) Ascendant Audio Mayhems with 24,000 watts RMS. 24 ft^3 tuned to 34 Hz.

159.7 dB at 42 Hz is my best so far. . .Not bad for 42 Hz, most SPL vans peak at 62-66 Hz. This one is setup to play music. (12) Ascendant Audio 7" mids and (8) Morel MDT-12 Tweeters on another 2000 watts. All active crossovers.

[jimcant]

Holy crap

24,000 watts.
That is like 10 EP 2500's worth

You're home theater, even with 2X4 driver arrays is going to sound a bit tame compared with that, although I expect that the sound quality may be somewhat better.
After all, that is why we all here have gone/or are going IB, in order to get very low distortion low frequency reproduction.

Listen to Chris though.
You are going to need a seriously strong wall for this, but I imagine you already know that.

Good luck and welcome, from another bass addict, although maybe not quite as extreme as you

Cheers,
Jim.

[chrisbee]

My post was only a little tongue in cheek. ;D

I wonder whether there isn't some value in covering both sides of the baffle wall with strong plywood fixed really well. Building something like an egg crate cored, stressed skin panel might allow arrays to perform well without building a seriously heavy masonry wall.

I'm afraid that just adding extra layers of board on only one side has relatively little practical effect on stiffness. Not compared with seriously increasing the thickness of the wall you should have built in the first place. Then adding well bonded stressed skin to both sides. If it's good enough for spacecraft ad aeroplanes it might just be good enough for an IB array baffle. Though I doubt it.

Do not confuse car audio with domestic IB subwoofers. The cabin gain adds a lot of what you are measuring. (as you already know)

My humble 4 x 15" IB can do well over 130dB(C) at 40Hz with very little room gain and with huge amounts of damping in my AV room. The needle goes right off the RS SPL meter's highest scale on sinewaves over quite a wide power band.

Domestic IBs are working down to the infrasonics and move huge amounts of air while doing so. Film LFE provides serious dynamic transients peak signals across a wide powerband simultaneously. Bang!!

Every square inch of your 8 x 18" drivers will meet air resistance trying to stop the cone from instantaneously moving its several inches of excursion to meet the requirements of your very nasty input signal. That results in a vicious push in the opposite direction for all 8 x 18" baskets on a relatively flimsy wall. Not so much a bang as a fart.

Bricks and concrete provide the mass and stiffness to resist the violent push. Wood and plasterboard will just laugh off your efforts and flex an inch or two each way. Thereby robbing you of half a dozen dBs in output. Perhaps you enjoy rounding off your transient peaks and taking their tops off like a knife through butter? I'd rather be frightened by film explosions and gunshots. No, make that terrified.

Instead of a massive explosion you will ask yourself if something just rumbled as the wall shook an inch each way. This might impress beginners but I'm sure you'd rather have the terrifying SPLs you have paid for so dearly in time, effort and money.

In fact a smaller IB array which did not put such serious loads into your flimsy wall might produce higher SPLs on dynamic peaks and offer faster rise times and much higher overall output on gunshots and explosions. Oh, and bass guitar and drums will also sound louder and crisper with far more detail, depth and realism.

You may think I'm exaggerating the problems with floppy walls. I have seen my own walls and doors moving over an inch despite adding extra 4 x 2s to my wall studs using lots of very long screws. Then I added 3 x 2s on top of the 4 x 2s. It made no visible difference to the stiffness of my wall when the IB was playing. It was a total waste of time and materials. I gained 8 whole dBs when I gave up trying with the array and finally built a manifold.

Jim used masses of concrete and steel bars to stiffen his array. Vertical arrays do not easily lend themselves to this treatment in a domestic situation. So another builder (robertr) used a very serious, triangulated, sand filled, steel structure to combat wall flexure. Others have used massive timber beams and struts.

Adding deep and heavy ribs at right angles to a free standing, timber framed wall might increase stiffness enough to make the exercise worthwhile.

A manifold removes all of the above problems at a stroke.

[afwjam]

Extreme forces call for concrete and steel. But maybe some triangles would help, heard their a really useful shape.

[bkolfo4]

I know what you mean on the wall movement. At one time I had a pair of Blueprint 1803's in very large low tuned ported boxes in a small room. Drivers were not even mounted in the wall and the walls moved. . .

If the HT is upstairs, I am worried about too much weight, so would I be better off putting the subs in a pair of manifolds?

If I stay with wall mounted, is it better to have two vertical columns of 4 drivers on each side of the screen, or would it be ok to run all 8 in a horitzonal array accross the floor under the screen? I am sure the room size has a big effect, but I see them built both ways, so I am curious about the draw backs of each. I worry about the room nulls, as my last setup was 4 avalanche 15's (two in each front corner), and I had a terrible null right where I sat. . .

Thanks for the help!

[ThomasW]

How about posting a picture/pictures of the room and a dimensioned copy of the floorplan?

Having that info makes answering these questions so much easier....

[bkolfo4]

That is one of the reasons I am gathering information right now. . .room has not been designed yet.

Picture a 2 story house. . .the only thing upstairs is the hometheater room. . .

I am thinking around 15-16 ft wide, 18-20 ft deep.

[bkolfo4]

Finally starting this build. House is 5-6 days from sheetrock.

Plan is for the front wall to look like this:




2x6 wall, MDF, heavily braced.

Ordered (8) IB3 18's yesterday.