Any reason not to consider this?

[BHTX]

This design would be used for both music and home theater..

Radian 5208C 8" coaxial unit with factory crossovers (1.8 KHz, not sure what type), with 2 Dayton ST385-8 15" Series II woofers per cabinet in an MTM configuration. The Radian coax would be in a sealed 0.39 cubic ft (11 liters) chamber, in between the two 15" Series II's. Each Dayton Series II woofer would also be in its own separate 5 cubic foot chamber, tuned to about 22.5 Hz, -3 dB at about 24 Hz. A professional electronic LR4 crossover would be used at roughly 250Hz or so. The woofer pairs would be wired in parallel for a 4 ohm load.

A center channel for movies would be built to the same specifications, except it'd be sealed with about 3 cubic feet (85 liters) of internal volume per Dayton 15" with an F3 of around 40 Hz. This center channel would be placed so that the drivers for all channels would be at identical height.

I have 3 new Mackie FR series professional amplifiers to power all of this with (except the woofers for the center channel, but I could easily get another one). I'd probably use the FR-2500 (750w per channel @ 4 ohms) for the woofers, and the FR-1400 for the Radians (310w per channel @ 8 ohms). A Rane PEQ 55 parametric EQ, or something similar, could be used to flatten any anomalies in the response curve afterwards. The specific unit mentioned above also has a highpass filter that can be set as low as 15Hz, for the vented 15's. This would only move the -3 dB point up to about 26 Hz.

As far as size is concerned, these massive towers wouldn't really be much larger than my current Eminent Technology LFT-8A planar hybrids. In fact, with the LFT8's Sound Anchor stands, they'd be roughly the same size, except a few inches wider. And with the way this room is set up (9ft ceilings with two 7 foot tall artificial trees in both front corners of the room behind the speakers), larger speakers actually look good in here. In other words, size isn't much of a concern, especially height, as the speakers I have in here now that I'm selling stand over 63" tall.

I attempted modeling this setup in WinISD, and it looked pretty good, I think. On another note... any opinions on going this kind of route versus using a smaller cabinet with different mid-bass drivers + separate subwoofers? I currently have 4 15" Ascendant Avalanche subwoofers laying around, but I might just go ahead and sell them all. Building something like the above would definitely be cheaper! And I like the simplicity of it. On top of all that, I think I prefer the sound of a tower with a large woofer that extends low, versus separate subwoofers. It just sounds better to me. Perhaps it's the phase problems that tend to exist between subwoofers and the main channels? Or maybe the longer distance that usually exists between the subwoofer and speakers? I don't know. But I've realized there's something about subwoofers that I just don't care for anymore.

Any help would be greatly appreciated!..

Thanks in advance,
~ Brandin

Radian 5208C and passive xover:
http://www.usspeaker.com/radian%20in...ial%20Speakers
http://www.usspeaker.com/radian%20508-2b-1.htm
(The in-ceiling 508/2B has the same specs and T/S as the 5208C, except a cheaper cast frame, and perhaps a few other minor details.)
http://www.usspeaker.com/radian%20in...htm#Crossovers
(Radian 322/08B-2 crossover)

Dayton ST385-8 15" Series II:
http://www.partsexpress.com/pe/showd...number=295-130
http://www.partsexpress.com/pdf/295-130s.pdf

The Mackie amplifiers that I already have:
http://www.mackie.com/products/frseries/

Rane PEQ 55:
http://www.rane.com/peq55.html

[nunayafb]

Sounds interesting, definitely not a typical arrangement. My only suggestion would be to dump the center subwoofer, the center channel does not have any low frequency info really, as movies with 5/7.1 encoding send the bass to the ".1" if the coax can play down to 50-60hz that should be sufficient for center sounds(Your receiver most likely splits the ".1" at 80-100hz anyway). In addition, music is stereo and you wont need the center at all, and with good imaging from the mains many would agree that you dont need a center channel for movies at all, your decision.
I may be wrong about how the LFE is distributed but im pretty sure the above is true.

good luck

[BHTX]

Originally posted by nunayafb
if the coax can play down to 50-60hz that should be sufficient for center sounds

In a sealed enclosure, it can't. Not anywhere close. By itself in a sealed box, -3dB @ 137Hz. And with a small xmax, it doesn't really need anything going to it around 100Hz. And the Dayton Series II's aren't really subwoofers...they're large mid-woofers that can extend down to the areas that subwoofers do. As for putting the Radian in a vented enclosure, the same thing applies, and I think I'm MUCH better off just going with a larger woofer to augment it that can also easily extend a bit higher than your average subwoofer, and keeping the coax in a sealed box. I'd also considered the CSS SDX15, but I still don't think it'd extend high enough without some serious FR issues right after the upper roll off freq. Same thing goes with the Dayton DVC 15...as I guess that'd also be an option, but I think it'd require an even larger enclosure. A bit more expensive, too. Plus they're dual 8 ohm, and I'd really want to run 1 channel per woofer in that situation, as I don't really want to drop it any lower than 4 ohns, regardless of whether or not the amp can take it (it can).

However, for rear channels (if I ever add that to the list), I'd run some more 8" Radian coaxes in small vented enclosures. But, rear channels aren't a major concern at this point. Half the time, I find them more annoying than anything, especially in an average living room.

[Pano]

Cool idea, but why MTM? Why not WWCoax?

2 5 foot cabs per side? You must have a big room!

[roger_lew]

Cool idea, but why MTM? Why not WWCoax?

My thoughts exactly.

Perhaps something like the TAD Reference one

[CeramicMan]

If you consider room gain - do some microphone measurements, make estimates based on your room dimensions, play around with echoes on sound software, or whatever... then you might find that the room acts like an integrator up to somewhere around 50Hz.

Combined with the sharp cut-off of a ported design, I'm guessing that the subs will produce an unnatural "delayed rumble" every time a short, low frequency "thud" is intended. Lots of speakers do this because of ringing and because they're tuned for a flat anechoic response.

[BHTX]

Originally posted by panomaniac
Cool idea, but why MTM? Why not WWCoax?

Why not an MTM? I didn't think lobing would be an issue with a 4th order at 250Hz. And I guess I just thought it'd help keep the sound more focused with the coax. But mainly, with the size of the enclosures for those 2 15's, having both woofers on the bottom would require that the coax be mounted at the center of the baffle, if not lower, with the enclosure extending up 2-3 feet...which I thought would look silly. What's the advantage of doing a WWCoax? Because the top woofer is closer to the floor? With 4 15's, I don't think that's a necessary concern, is it?

Originally posted by panomaniac
2 5 foot cabs per side? You must have a big room!

Not really. About 14 x 16 feet.

Originally posted by roger_lew
My thoughts exactly.

Perhaps something like the TAD Reference one

Those are nice. I was also thinking of going with a slot port...one on top, and one on bottom (if I did the MTM type thing in separate chambers).

Originally posted by CeramicMan
If you consider room gain - do some microphone measurements, make estimates based on your room dimensions, play around with echoes on sound software, or whatever... then you might find that the room acts like an integrator up to somewhere around 50Hz.

Yeah, this is something I've always been interested in doing, but haven't really had the chance. I guess I need to look for some good real-time analyzer software and an omnidirectional mic.

Originally posted by CeramicMan
Combined with the sharp cut-off of a ported design, I'm guessing that the subs will produce an unnatural "delayed rumble" every time a short, low frequency "thud" is intended. Lots of speakers do this because of ringing and because they're tuned for a flat anechoic response.

True. I've observed this with many ported systems, and even some sealed systems in tiny rooms. How do you overcome it? Keep in mind, I don't have a problem with using some equalization on any part of the system if needed, and am actually planning on doing so. I was very interested in building some large low tuned enclosures with these Avalanche 15's a while back, but I've decided not to. After giving it a lot of thought over a period of months, and doing a lot of modeling, I don't think I'd like the results. I don't want to be forced to worry about subwoofer cones flying out of their enclosures (even with 27mm xmax), from infrasonics sneaking up on me when I least expect it. But mainly, the enclosures are just too big for what they'd give, IMO. With what I'm considering doing now, I know that sounds pretty ironic, eh?

So if a flat anechoic response isn't ideal, then what is? I suppose I'd have to do a lot of measuring and modeling of this room first? What if I move? Will I feel obligated to rebuild the enclosures again if dimensions are vastly different from this room? That'd be ridiculous, and not an option for me (no woodworking skills or equipment).

However, I did recently find someone that is planning to help me out with all the woodwork for whatever design I decide on. So hopefully that'll work out. He showed me his garage and some of the work he'd done, and I was pretty impressed. I think he mainly does cabinet and furniture work though. Regardless, I can't see why he couldn't easily do something like this. I think it'd be very easy for him, compared to all the other stuff he does.

Oh and... any recommendations for woofers besides the Daytons?

Thanks for the replies. Keep 'em comin'.

[BHTX]

Actually, the CSS SD12 might be an option? Two per side, that is. Could do the WWCoax thing that way, too.
Looks like these extend a bit higher than I originally thought. Maybe high enough that it wouldn't be too problematic if crossed 4th order at 250ish Hz (xover really needs to be at least this high for the dual concentrics).

But yeah, looks like these SD12's can extend roughly the same as the 15" Dayton Series II, although obviously less sensitive, but they can do it in a much smaller enclosure. I'd be looking at about half the enclosure size for 2 SD12's than with 2 of the 15" Series II's. Max SPL would obviously be a bit lower, but oh well. I think cutting the enclosure size in half might be worth the trade-off.

Other than that, my only concern is that...well...it just sounds weird. A CSS woofer with a Radian dual concentric?? That's just strange. I mean, look at the CSS woofers. They're all nice and pretty, you know. The Radian, well...it's pretty much a pro driver. A high quality one, though.

[BHTX]

Not exactly positive that I'm doing all of this correctly with the modeling in WinISD, and I know modeling only means so much anyway, but if there's ANY accuracy at all, the 5208 or 502/2B dual concentrics match great with woofers like those listed above. Any of Radian's other coaxials appear to have huge differences in phase when paired with other woofers set up like this. I'm sure the majority of it has to do with the xover freq used. About 300-350Hz actually looks better on paper, but with woofers like the SD12, top-end extension becomes an issue. As previously stated, it might already be a problem at 250 Hz. I still don't know.

As I discovered late lastnight, a pair of CSS SD12's looks like it might work VERY well with the 5208C. I've been modeling similar configurations with other drivers ever since, and overall, the SD12 keeps coming out on top. My only real concern of importance is how high these SD12 "subwoofers" can actually extend. ANYONE have these drivers that would like to comment??

Also, my question earlier regarding the disadvantages of using an MTM type configuration with large drivers like this crossed at 250 Hz was never answered. The other very few members willing to post in this thread acted as though it was something horrible to do, and regardless of whether or not I do it (as I probably wouldn't if I used a pair of SD12's per side), I'm still curious as to why this would be such a bad configuration when crossed at lower frequencies.

[BHTX]

http://www.acoustic-visions.com/~aco...2datasheet.pdf

..Once again, does 250Hz LR4 look like it'd be a problem?

Oh yeah, I also realized lastnight.. that TAD Reference One that roger_lew posted supposedly has the same 25Hz - 250Hz extension and crossover point that I'm interested in using. Just thought that was kind of a neat coincidence.