Help, need good LF 12'' (300mm) driver - diyAudio
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Old 18th July 2006, 09:43 AM   #1
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Default Help, need good LF 12'' (300mm) driver

As the heading says, I have a pair of Martin Logan Monoliths, the bass driver is a so so Eminence built for ML for this speaker, I would love to get something better, this is what is has to do.
Attached is the specs for the Eminence, if they are correct.

Box size sealed 85liters
Crossover is 125hz 2nd order 12db per octave

The goal is to be -3@30hz but to have clean out put to 400hz

I've looked at
Peerless XXLS 830847
Focal 12V726
Focal 12v726S
I'm sure there are many others


Thanks George
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Old 18th July 2006, 11:22 AM   #2
tinitus is offline tinitus  Europe
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It might not be that simple, because of "high" crossover point - 125hz/12db - its part of the speaker

Consider a seperate aktive sub with low crossover and EQ
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Old 18th July 2006, 02:56 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

The most important parameter is to match the 92dB sensitivity.
I think most of the high excursion 12"s are lower than this.

Also finding a 12" driver suited to 85L sealed box loading is
not going to be easy, by the time you do its likely to be very
similar to the Eminence in its capabilities (due to the 92db/W).

Possibly you need to factor in a plate amplifier with a 2nd
order L/R roll-off and remove the passive croosover, would
then let you use a very serious 12" unit which has much
lower sensitivity than 92dB/2.83V/1m.

/sreten.
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Old 19th July 2006, 12:12 AM   #4
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Ok i've found two drivers that may be ok, what do you guys think, I ran them through a program for the 85liter (3cuft) sealed box, remember it's crossing over to ELS pannels at 125hz at 12db per octave and this is what i got.

Focal 12V726:
-7db at 30hz
QTC of .69
mms of the Focal is 55 gram so it should be ok up high 200-400hz

The ACI SV12:
_4db at 30hz
QTC .78
mms of the ACI is 100 grams, could be too heavy for 200-400hz.

Which way guys? I'm not very experienced with this driver parameters voodoo, I'm more into the electronics side of things.

Cheers George
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Old 19th July 2006, 04:33 AM   #5
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The Dayton RSS315-HF is -5.7dB at 30Hz but should (from what I've read) play cleanly up to 500Hz.

Qtc is 0.630.
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Old 19th July 2006, 06:00 AM   #6
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Yes thanks 454Casull, that Dayton RSS315HF4 looks good also, I can't find any mms figure on these anywhere which will give me an idea about the mass of the cone for the higher frequencies.

Cheers George
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Old 19th July 2006, 01:44 PM   #7
rabbitz is offline rabbitz  Australia
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Your box modelling software should be able to auto calc the mms from the other parameters.
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Old 19th July 2006, 02:28 PM   #8
mazurek is offline mazurek  United States
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You need to have a provision to handle the breakup mode in the dayton if it is played high up. I cross at 160Hz LR4, with 12dB slope the mode is still measurable. A notch filter would probably be needed for any metal woofer.
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Old 19th July 2006, 06:25 PM   #9
Notax is offline Notax  Montenegro
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If you need 12" with efficient od 92-93 dB, passive x-over, go for Monacor SPH-315. Bass-reflex 72-80 L netto, Fb=36-37 Hz.

Monacor SPH-315
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Old 19th July 2006, 06:50 PM   #10
sreten is offline sreten  United Kingdom
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Hi,

seems I have to state the obvious :

You must have DCR near 2.5 R and Le around 1mH.
(Because the crossover has to work correctly)
Then you must have near 92dB/2.83V/1m.
(Otherwise the bass level will be too low)

Then you can consider a driver, none so far are suitable.

/sreten.
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