2X15 sealed TC-3000...problems :(

[kramskoi]

What are the problems associated with an opposite-side firing dual driver cabinet?

I don't know of any commercial designs using this orientation, except maybe the future offering from Mark Seaton.

This cabinet would be small for 2-15" drivers...27x21x21 (5.4 cu. ft. internal)...i'm concerned with internal pressures and unwanted resonances.

need some guru help...thanks! :T

[ThomasW]

What are the problems associated with an opposite-side firing dual driver cabinet?

I don't know of any commercial designs using this orientation, except maybe the future offering from Mark Seaton.

Not much other than having room placement so neither driver fires directly into a wall.

The $32,000 Krell MRS has this configuration.

[Mark Seaton]

As Thomas notes, the design is hardly something original to me. One of the best examples of it that I personally experienced was the bass towers for the Martin Logan Statement E2s that I twice had the pleasure/backache of setting up (fun to help others spend money). It used 4 stacked boxes... per channel. Each box had 2 12" drivers on opposing sides. the baffle was something silly like 3 x 3/4" thick and the rest of the box 1.5" thick. There were no vibrations. Many others have used the same configuration.

I'm not sure the TC-3000 would be my first choice for what you are after.

[kramskoi]

Not much other than having room placement so neither driver fires directly into a wall.

The $32,000 Krell MRS has this configuration.

Thanks again thomas...as always :T...there will probably be more posts about this driver...

[kramskoi]

As Thomas notes, the design is hardly something original to me. One of the best examples of it that I personally experienced was the bass towers for the Martin Logan Statement E2s that I twice had the pleasure/backache of setting up (fun to help others spend money). It used 4 stacked boxes... per channel. Each box had 2 12" drivers on opposing sides. the baffle was something silly like 3 x 3/4" thick and the rest of the box 1.5" thick. There were no vibrations. Many others have used the same configuration.

I'm not sure the TC-3000 would be my first choice for what you are after.

Hey...Thanks Mark...i was hoping you would chime in...been reading about your latest exploits...especially the 2X15...it was an inspiration for me...VERY exciting things to come...good luck to you.

I've searched high and low for a high (32mm+) xmax driver that does'nt cost 1,000.00. I already have a tumult 15d2 but i have issues with it so it's gone. Aurasound and JL Audio (13w7) were other choices but now that i've decided on this 2X15 it would'nt be cost effective for a pair.

The tc3000's ebp=69 the fb is high (42Hz/Q.560) but it comes in at 4.4 cu. ft. accounting for everything. The Vd is 5.64 liters swept and 89.2 dB sensitivity, as calculated by winisd pro. With 9dB/Q.7 boost at 20 Hz the response is down -6 db @ 19 Hz...this is sufficient for me...1400 watts brings it to full linear excursion (115 dB @ 20Hz 1/2space/1m).

The single tumult will do 120 dB/2m (uncorrected) in my theater room (1,800 cu. ft)...the 2X15 would only be at ~1/2 of xmax for the same level. It models to a 2.5 dB advantage over the tumult...and adds nearly 1 liter of displacement (based on Sd 830cm^2).

I know all this small-signal business is more academic than realistic but i like this driver in a bessel alignment and two for the price of one JL or Aurasound is a steal. There is a diminishing return on upper echelon drivers in regards to price vs. performance.

I also have only a 6 foot wide space in which to house a subwoofer and this would fit with room to spare.

I wish only that it did'nt require so much boost down low. However, given the output, and room gain, i can live with it.

Thanks again, Mark for commenting and i welcome any thoughts and input on this configuration and any problems i should address. :T

[Mark Seaton]

So long as you're willing to provide lots of power, what you have outlined looks promising. You probably don't really need a LT circuit for this one, just use a couple of cut parametrics for the inductive bump around 50-55Hz and broaden the cut enough to keep the response smooth. With 8-10dB of cut you should have an anechoic response that fits a 6dB window to about 20Hz, which should mate well in room. Basically just build it up, measure in room, and apply cut to the top end rather than boosting the low end.

I see at most 1dB of advantage going from 90-120L per driver, and that's a pretty big box. If you built a 180-200L enclosure and grabbed as big an amp as you can afford, you should have some very nice performance there, and still be hard pressed to find Xmax above 10-12Hz, which isn't a bad problem to have in terms of sound quality. The other consideration would be 4x 15" woofers in a little larger overall volume, probably 2 boxes. You wouldn't need as exotic a woofer, you distribute the power over 4 coils, and each driver is moving less than 1/2 that of the two. Costs won't be that much different. Of course the TC-3000 is one mean lookin piece of engineering.

[Jack Gilvey]

I know all this small-signal business is more academic than realistic

So? Sure as h*ll beats bickering over the "musicality" of one ported sub vs. another...

[Jack Gilvey]

Mark, even if you can deal with the FR hump caused by a high Le with eq and/or by crossong over low, what other effects might it have aside from FR?

[Mark Seaton]

Well, if you have a very high Le, that's a big coil moving around, with the magnetic or electrical parts around it changing as it moves. The specs mention a copper shorting ring. I would expect in this case it serves more to help keep the Le linear with excursion more than reduce it, as as reducing the Le at low frequencies and for that large a coil takes a LOT of copper.

The inductive hump will slightly amplify distortion harmonics that coincide with it, but this applies to all drivers. I would also expect to see distortion rise at and above that inductive hump. The question of course is how audible it is, and without a lot more measurement or and idea of what happens with the Le vs. position, we are guessing. What a big inductive hump should do is flag you to pay attention and check that unwanted things aren't going on. In many ways the consistency of the Le with position is more important than how low it is. The reason lower Le is often better is that if this comes from less VC wire to start with, you don't have as much moving around to try and linearize.

I don't pretend to have it all figured out, but there are plenty doing research into the matter (i.e. Klippel).

[kramskoi]

So? Sure as h*ll beats bickering over the "musicality" of one ported sub vs. another...

ah!...yes!...point taken. There tends to be quite the theatrics on some of the HT forums...a lot is taken out of context and posts degenerate from intellectual to instinctual...or egostistical, if you will...it becomes an "i'm right, you're wrong" type of bantering...not conducive for intelligent, humane conversation...i'm here to learn as much as i can without these "theatrics"...life's just too short.:T

[bossobass]

Mark,

Model, schmodel. Ya cram a couple o' them pigs in a strong sealed enclosure, drag it outside and electrocute 'em with 4KW while a mic records the execution attempt.

You use a variable-parameters L/T to dial in the desired anechoic response, record the settings and...whamo...ya got the thing nailed.

You either like the results and build a few more, or ya scrap the proto by sellin' it to someone who will think it's the end o' the World as he knows it.

What am I missing?

BTW, I'm gettin' 3 o' them to also try a 1X15" at the same time. I'll let ya know if they survived. :evil:

Bosso