3 way with 18" woofer


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2006-12-06 6:18 am
I am planning to design 3 way cabinet with 18" woofer, 12" midrange & 2" compression driver.
I will test the drivers for thielsmall, impedance graph & frequency response.
I wish to use 18" upto 250 hz, then 250hz ~ 2500 hz will be midrange.

I need to use 3 way passive crossover due to some requirement.
Now where to set test microphone for woofer to test frequency response?
In the center of the box or in the center of woofer?

For midrange & cd horn i will put at the center of midrange & horn.
Then i will take the frequency response,

for combined frequency response of the all drivers, what will be the mic setting requirement.

waiting for guidance from fellow members.


  • 3 way WITH 18 Cabinet.jpg
    3 way WITH 18 Cabinet.jpg
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Standard is 1 meter.

This isn't the situation in listening position with a MLS measurement you can do it also on 3 or 5 meter to see how the wave front mixed on distance. In fact I think this is the more practice than on short distance.

I have a 2" horn for sale like you did draw there interested? almost new with original packaging.

2" driver can be crossed 800-1000Hz.
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Hi, 12" is far too big for a "midrange". rgds, sreten.

My impression is also that a 12 or 15 - or even an 18 can be excellent in the midrange, perhaps with a little help from a well-placed crossover notch.
The Bastanis, the Emerald Physics and the Gradient 1.3
The Gradient 1.3 Revisited
all did well with 12s, and Dr Geddes does well with a 15 covering to 1000 Hz.
I think what is important that is gained is headroom in the range of 200 - 500 Hz and the ability to place the crossover down around 200 - 300 Hz and not in the more dangerous 600 Hz zone.
Hi, 12" is far too big for a "midrange". rgds, sreten.

In terms of the extent to which a 12" driver is beaming at (the cross-over frequency of ) 2500 Hz, conventional wisdom says that 12" is too big. But this can be OK if the one listener is on axis with the pair of speaker systems. My current pair of stereo speakers are two-way with a 12" woofer, and I really like them. However the vast majority of time, I am the only one listening to them, and I have the pair toed-in to my in-the-middle listening position.

For more than one listener listening to stereo speakers simultaneously, a 12" mid-range driver radiates too narrowly over much of its pass-band to give good reproduction to any listener off-axis.

My understanding is that a 12" woofer typically has a 6 db down at 90 degrees at about 1200 Hz. This is the optimum crossover point for a 12" midrange.
Also, my understanding is that a 2" compression driver with a 3" diaphragm starts to break up at about 8 kHz. For a 1200 Hz crossover point, a 1" exit driver is more approprate if you do not want a super-tweeter/ 4 way.


10 inch better at 2.5KHz crossover

IMO You will get better results using a 10 inch rather than 12 inch if you need / want to crossover as high as 2,500 Hz.
I would only go up to 1KHz or so crossover with a 12 inch.
Also a shallow horn to control directivity will be a gig help in either case.
DDS pro horns are a good start.

I can recomend a Precision Devices PD1850 ( the old model, not tried the new ones), with A 10 inch Volt, Volt Loudspeakers - About Us
BM 2500.5 Volt Loudspeakers - About Us
They are pro versions of the famous Volt studio 2500.4 .
If you have the ££ PHL 10 and 12 inch drivers are sweet.

Good luck
PS The Beyma TPL is way better in domestic use than a typical Comp Driver...
Try the custom Gamma horn( I think?) by Jagazara or whatever(!) check out his group buys page and website, he makes great DIY and speakers...Way better than Dr Geddes obverpriced stuff.
From just a directivity standpoint ..Pano had posted a .pdf (altec technical letter 237) which illustrates cone driver directivity characteristics. I think this is useful, perhaps as a starting point, in blending the response of what the OP has proposed here as well. A 12" (10" piston diameter) will have 100* @ around 1.5kHz .. a 10" (8" cone diameter) around 1.9kHz

At 2.5kHz both are at or below 60* directivity.
Overkill.. getting too old for this!

Hi Helmuth,

Yes I think I am begining to mellow with age, down to just a 10 inch for midrange...!!:D

Many years ago ( 15 ish) I bought a really nice two way speaker kit from Wilmslow Audio in the UK, it was called the " Vortex" and used the great Volt 10 inch driver - BM 2500.4 studio, crossed over at 2.2 KHz to a soft dome Morel tweeter.
It was really good, esp when I ditched the passive crossover and used a pro active crossover ( DBX I think, or something similar) and used two power amps, Quantum or DPA, again I cant remember for sure.
The point is, that despite some beaming of the 10 inch starting around 1400Hz it sounded fab, the ease of the big 10 inch more than compensated for the poor off axis performance.
About 3 years ago I perched a Beyma TPL with the Beyma horn on top of an open baffle ( VPL) with the 10 inch Volts covering 200Hz to 1,800 Hz, and Beyma 15 inch open baffle bass, all controlled by a DEQX...So so sweet yet full of detail and great dynamics.
I always prefer large / larger Sd and ultra low cone movement with poorer off axis performance, Vs technically correct stressed little " pure midrange" 4, or 5 inch midrange drivers thrashing around ( mass on a spring working hard) pumping away right up to and beyond XMax with all the thermal, mechanical and time domain distortion that goes with that set up.

OT - but worth pointing out, my audio journey has now lead me to what I believe is the Holy Grail...
Line array of 16 per channel 4.5 inch BMR's (more Sd than a 15 inch driver) covering 80Hz to 20KHz, subs below 80Hz, and all DSP / Eq in Lap Top JRiver and JPlay...

Tinitus, you are right, there are quite a few sweet 12 inch drivers that you can use as midrange, In my limited experience, only the Volt and PHL 10 inch are exceptions, they really are gems and worth seeking out if you are looking for a compact but high performance 3 way design.

As always enjoy the DIY journey and dont worry about the destination too much!