Dual MCM FLH

[Doc777]

the consumer JBL stuff has above average sensitivity, but not the strongest motors coupled with middle of the road Q's to work in sealed/ported/BP boxes. A compromise by design.

So with the SD of a 10" and a set of T/S not anywhere near optimized for horn loading. I'm not sure they'll be as awesome at 8:1 as the el-cheapo mcm drivers.

Can you give me a range of recommended parameters for a TH?
I thought Qts .3-.5 was good.

 

[GM]

Thanks for all the info!

My understanding of TH is that they typically shoot for lower cone loading (1/4 wave resonator stuff) and typically demand high xmax drivers to achieve their spl's.

Just go's to show, when the right parts are assembled sometimes the rules can be bent/broken.

Now if extrapolated for dual drivers & 2x pwr, your box would do 116dB @ 30Hz 2pi per cab?

Was that with an 8" - can that be correct, seems like that should be breaking thermodynamics laws! I have dual-18 ported cabs that would smoke the the vc's before measuring that!

You're welcome!

True, though normally wanting much higher average SPL one normally expects from a small driver and not 'rules' per se, just rules-of-thumb. Also, 'haste makes waste', i.e. I forgot to note that I shellac'd the diaphragm on both sides to further stiffen it, slightly lowering Fs, raising Qts.

I wanted to do some true compression driver 10:1 testing, but the owner ignored me re using a power limiter, so wasted no time blowing it to smithereens 'cranking' it wired to a 400 W car amp, claiming it wasn't loud enough.

In theory, but reality may require a bit > 2x power, so for long term high power apps best to assume only a 3-4 dB gain unless it's a very robustly built driver, at least that was the case decades ago, so short of testing to destruction or others chiming in with long term experience, your guess is as good as mine.

Yes, MCM 55-2421. In general, as the VC/diaphragm diameter ratio increases, CR decreases and I imagine one reason why compression horn drivers have the VC out at the surround junction.

GM

 

[GM]

Can you give me a range of recommended parameters for a TH?
I thought Qts .3-.5 was good.

The lower the effective Qts [Qts'] = Qts + any added series resistance [wire, etc.] and due to thermal power compression losses, the wider its gain BW, so depends on the app.

Since most DIY designs don't account for much, if any, losses I assume they use EQ to 'shape' its high continuous power response as required.

For HIFI/HT where a ~ two octave BW in a short pathlength/'fat' cab is normally satisfactory, you can use a higher Qts. Ditto where acoustic efficiency is paramount and/or size isn't an issue.

For an overall good performer limit Qts to ~0.4 at most since thermal power compression will increase it with increasing power and of course for 'squeezing' the most performance out of a given driver, then best to only use those rated for prosound high power horn or similar [competition] mobile audio 'sub' duty.

GM

 

[Doc777]

The lower the effective Qts [Qts'] = Qts + any added series resistance [wire, etc.] and due to thermal power compression losses, the wider its gain BW, so depends on the app.

Since most DIY designs don't account for much, if any, losses I assume they use EQ to 'shape' its high continuous power response as required......

For an overall good performer limit Qts to ~0.4 at most since thermal power compression will increase it with increasing power and of course for 'squeezing' the most performance out of a given driver, then best to only use those rated for prosound high power horn or similar [competition] mobile audio 'sub' duty.

GM

Thanks GM. My TC-9 is Qts .34, Fs 23, Vas 117, BL25. There is a slight chance that it might be an older version with a Qts of.18! Yikes! Making a home theater sub x-over at 70 hz, 12 cf, TH length of 18', iNuke6000DSL. If it is an ultra low Qts, I am hoping I can EQ it to flatten the response but I am very curious to know if it will be dull or lifeless? Crossing my fingers that it will be a newer version but a little apprehensive at this point in time. When you said a good performer limit was Qts.40, is that a maximum or minimum?

 

[GM]

You're welcome!

Max.

Which TC-9 and are these measured specs? They don't match [very close] to any 12-15" TC-9 I've found specs for.

GM

 

[Doc777]

I found some specs from a TC-9 Orion HCCA, and a LMSR which is a major upgrade. What I posted came from the TC sounds archive. There was no date so I don't know how outdated they are. What has been your experience with the TC9? My seller just wrote me saying it was a QTS of .2 -.3. At this point maybe I should use something more compatible, Dayton RSS or eminence.?

 

[Doc777]

Found this old TC9 spec but with so many different models I would have to question if they remained the same.?

http://web.archive.org/web/20040830205905/http://tcsounds.com/Images/15tc9_2570.pdf

NE1 know?

 

[GM]

No experience beyond doing designs for others and the fact that the motors were used on a variety of 'customs', but too often just listed as TC-whatever and as you posted, the 'stock' specs are off enough to impact cab design. Ditto other brands/models <sub>woofers since '75 other than Altec/GPA, some JBL and a few various singles here n' there like the MCM recently. Mostly messed with little 'full-range' drivers, inexpensive DJ/PA rigs.

Anyway, all these TH oriented posts are far removed from this thread's FLH subject, so please start a new one with all pertinent details.

GM</sub>

 

[Doc777]

Hijacking a thread will get you 8-10. Sorry all and thanks for your help.

 

[Sublimacon]

Doc777,
The Forum's server just tossed my lengthy reply (that I typed on my cell). Something about "your token has expired" - WTF pain in the a$$ ever.

I'm sorry, I just don't have the patience to re-chicken peck all of that again :-(

Looks like GM gave some good info on driver compatibility.

Chris

 

[djlivex]

Any updates on this thread JBell? Just curious if others have built the double 55-2421 in the original drawings would like to build a couple for DJ work one on each side of the dance floor flat to 40Hz would be great for my operation. Thanks

 

[maxolini]

i now this is an old thread
but i wish to now if somebody made the final plans for the double 8"

 

[arcgotic]

Hello,
Just saw this build, very nice!
I ordered a pair of Mivoc AWM104 (55euro/piece)mivoc AWM 104 - 10" Woofer
I will post later the schematic (i have to do some math )
But using the same Hornresp input data (just 1 Mivoc instead), the output looks promising. Corner loading.

 

[Brian Steele]

using the same Hornresp input data (just 1 Mivoc instead), the output looks promising. Corner loading.

I suspect that it might be more accurate to use "Par" instead of "Con" segments in that simulation, based on how that horn is folded in that box.

 

[arcgotic]

Thanks Brian! I am thinking at another way to fold.. also I want to have the horn on the corner (like a triangle seen from above).