Using 2 12" with a horn/compression driver

[ecl86]

I picked up a huge pair of beautiful cabinets from a neighboor who left them on the curb side for garbage man to pickup. They are 4 feet tall 2 feet wide and 16" deep. They have slots for 2 twelve and a horn. I am thinking about putting a couple 8 ohm 12" low frequency drivers from Parts Express: http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-320 and perhaps this horn here: http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=270-304 plus using JBL 2416 or BMS 4540ND compression driver.

Since the 12" will be wired in parallel, the impedance would drop to 4ohm. Is there anything wrong if I wire a 4ohm load with an 8ohm load on the horn using simple 1st order crossover design.

Does anyone have similar setup using 2 12" and a horn with good result. Please post plan and crossovers design if possible. Thanks in advance.

The cabinets would be sealed by the way.

[ChopsMX5]

"Does anyone have similar setup using 2 12" and a horn with good result."...

I'll be running two 15" drivers with a horn per channel pretty soon! So there's no problems running a pair of 12's with a horn.

One thing though, you may want to reconsider the 12" drivers you have chosen. I'm not sure if those particular drivers will be good running up high enough to cross over to the horn driver. I think that maybe a pair of pro audio drivers might be a better choice. They'll definately be a lot more efficient which will match up better to the horn, but at the cost of less bass output.

But don't take my word for it. Let a few others here have a chance to answer your questions as well and see what they have to say. ;)

[ecl86]

I believe the 12"s that I am referring are 92db efficient. By wiring them parallel efficiency will be 95db and I would add an Lpad and adjust volume to match the horn. The existing holes are pretty close together so I dont think putting in 15"s is possible.

[pos]

You can even expect 98db of efficiency with mutual coupling up to maybe 200hz, if the holes are close together (and if your amp delivers into 4 ohms twice the power it does into 8 ohms)

[ChopsMX5]

I believe the 12"s that I am referring are 92db efficient. By wiring them parallel efficiency will be 95db and I would add an Lpad and adjust volume to match the horn. The existing holes are pretty close together so I dont think putting in 15"s is possible.

Well efficiency isn't my main concern. I wasn't even suggesting using 15's. I was just saying that I will be using 15's and that you can get good results using 12's or 15's.

The main thing I'm concerned about is the quality of sound those Daytons you chose will be like up around the xover frequency. I know they're rated up to 2.5kHz, but that doesn't tell you how they'll sound up that high. See, pro audio drivers are meant to play that high, and sometimes even higher near 4kHz, so they can be used in dedicated 2-way systems and provide pretty decent midrange with a good transition over to the horn. The Dayton woofers you want are mainly for the bass section of a 3-way system, and probably crossed somewhere between 200-600Hz, only reproducing lower mid-bass at the most and for a good transition over to a midrange driver. That's all I'm saying. ;)

[Zilch]

Two 12s playing mids are going to generate phase interference, no?

Consider using one as a "helper" in the low frequency only.

See 4435, 4612, others.

You're not building guitar speakers, I presume....

[pos]

4612 does that? So this really is a mini 4435, sorta !
Everst II also use this technic, so this must be THE way to go :thmbsup:

It seems like Genelec run its double woofers (12", 15" and 18") togheter, and up to 400hz in its big monitors.
The JBL 4350 crosses at 250hz, and the 4355 at 290hz (same slope).
The highest crossover point I have found in studio monitors for such dual woofer configs are in the Westlake TM-3, with 800hz:
http://www.westlakeaudio.com/Speakers/Professional_Series/tm-3.html
They use 350hz for most of their other monitors. Why don't they use the helper woofer technic by the way?

[grumpy]

Why don't they use the helper woofer technic by the way?

100 ways to skin a cat (sorry Heather)... :D

[ecl86]

ChopsMX5, I understand you now, it's my bad. The reason I picked the mentioned 12" because they are inexpensive.

Zilch, I am building speakers for home hifi. Will do some searching for the 4435, 4612 unless you've some DIY that is good and simple. Thanks.

[Robh3606]

JBL has done MTM's with drivers as large as 14"s and there is a current 12" MTM available in Japan now.

http://www.harman-japan.co.jp/product/jblhome/s5800.html

Specs here:

http://audioheritage.org/vbulletin/showthread.php?t=10638

I have been messing with 8" drivers using 2118J's and it sounds good. You have to watch your crossover points and slopes and the directivity of the drivers at crossover. I know when I was trying to measure the 2118's without an upper crossover in place it was a mess. Holes and peaks galore which is the destructive phase cancelation Zilch was talking about. Once the crossover was in it looked much better.

You could go the 2 1/2 was as well but that is really dependant on the woofers low end response. You could easilly try both just have to change the crossovers. Which ever one you like better is the keeper. Either way you could end up with a good sounding system you just have to work at it.

Rob:)

[ecl86]

Thanks Rob for the link. They sure look cool. After doing some research, I found out that the cabinets that I picked up are Bozak Symphony B-4000. I think I can use a jigsaw to cut out the front panels and put in a new piece of plywood for front baffle and make holes for whatever size I want since these are huge cabinets.

Now, question is what should I make them to be. I have a budget of $300~$400 to spend on drivers/parts.... Also have a pair of woofers from Jubal that need to be refoamed, also have a pair of LE5 midrange and a couple 2402/075 laying around....

[Zilch]

JBL has done MTM's with drivers as large as 14"s and there is a current 12" MTM available in Japan now.From the description of the boxes, I don't think ecl86 is talking MTM, which is why I jumped to 4435 configuration....


I found out that the cabinets that I picked up are Bozak Symphony B-4000.Provide the dimensions, please. Some pics would be helpful, as well, particularly of the front baffle....

[Robh3606]

From the description of the boxes, I don't think ecl86 is talking MTM, which is why I jumped to 4435 configuration....

4 feet tall x 2 ft wide with a horn? Well I am in MTM mode so anything remotely possible will push me over the edge. That's funny because it easilly could be either way:blink:

Pictures would be nice.

Rob:)

[ecl86]

I've searched long & hard and the closest that I could find is here: http://www.abrown.com/museum.htm . The cabinets that I have is plain jane, they dont have the divider in the middle or curvy top; and yes, they are that big gentlemen.

[ChopsMX5]

They are 4 feet tall 2 feet wide and 16" deep. They have slots for 2 twelve and a horn.


I found out that the cabinets that I picked up are Bozak Symphony B-4000

The only thing that bothers me about this is that Bozak never used horns in any of their designs, so I'm not sure what those cabinets of yours really are. They might be DIY jobs that someone made to "look" like the B-4000.

Check out the link below for the various Bozak designs.

http://www.hifilit.com/hifilit/Bozak/Bozak.htm

[Zilch]

It was an 8" midrange, not a horn apparently, with a vertical array of tweeters down one side.

Are the cabinets mirror-imaged, i.e., the woofer stack on the left in one and on the right on the other?

They're 8+ cuft closed boxes, looks like. Any subdivision of the volume inside?

[ChopsMX5]

It was an 8" midrange, not a horn apparently, with a vertical array of tweeters down one side.



Actually, the midrange was a 5.25".

This was taken from a review of the Bozak Concert Grand in Stereophile Mag...

http://stereophile.com/historical/1005bozak/

"The heart of every Bozak speaker is the 5¼" midrange driver, whose magnet structure is the same size and diameter as that of the 12" woofer. Bozak stated that, "based on the laws of physics, [this unit] is so sized that the diameter of the speaker cone does not exceed the wavelengths of the sounds they are designed to reproduce." The cone itself is made of uniform-density aluminum coated with a thin film of latex rubber on each surface. The aluminum is perforated to help bond the rubber coatings and damp the cone. Legend has it that Rudy Bozak worked on the voicing of this drive-unit to minimize the annoyance of LP tracing distortions."

[Zilch]

http://www.roger-russell.com/columns/columns.htm

[ChopsMX5]

http://www.roger-russell.com/columns/columns.htm

Yes, you're correct. Sorry, I was looking at the wrong driver specs on this page... :o:

http://www.hifilit.com/hifilit/Bozak/1968-4.jpg

[ecl86]

Yes, as i mentioned previously, I think I can use a jigsaw to cut out the front panels and put in a new piece of plywood for front baffle and make holes for whatever size I want so existing holes really do not matter.......

or i could buy bozak parts and make them bozak; though i am a very horny guy and want to stay that i way.......:)

[Zilch]

http://audioheritage.org/vbulletin/showpost.php?p=183906&postcount=16

[ecl86]

Zilch, they are mirror image. 12" woofers to the right vertically -1 in the middle and the other at bottom, midrange on middle's top and tweeter arrays to the inside. No subdivision inside cabinets.

I found some pictures on the bay: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120153150900

[Zilch]

Go ahead with your plan, but put an 18 mH SuperQ inductor in series with each of the bottom woofers, PE #266-958.

Block off the opening(s) where the tweeters were.

Those are rather wimpy woofers you've chosen, but they'll play at moderate levels down to ~29 Hz (-10 dB)....

[grumpy]

This endeavor will require some work and iteration, regardless...

good news is you've got options. a single 4" port that's a few inches long will bring up the
low end in ultimate loudness and efficiency (with tradeoffs, of course)....

could also tune lower and try emulating the 4435 dual-woofer design (may require a
larger inductor than what Zilch has kindly suggested as might work with a closed box).

Might also want to consider dropping a multi-watt 32-64-ish ohm resistor across the low-passed
woofer (bringing down the impedance peaks and crossovers will act more as expected).

...your boxes... have fun :)
-grumpy

[Thom]

Two 12s playing mids are going to generate phase interference, no?

Consider using one as a "helper" in the low frequency only.

See 4435, 4612, others.

You're not building guitar speakers, I presume....

From many of your posts I gather you don't favor dual drivers. (I actually gather that your feelings are stronger than that) Is this from a study, several studies, personal experience? I'm neither agreeing or disagreeing with you, I'd just like to know where it came from. Thank you.

I'm sure that all this means is that I don't get around much but every bozac I ever saw had two tweeters mounted to the woofer.

[Zilch]

It's axiomatic - two sources playing the same program material will interfere with each other.

The Bozak tweeters were splayed.

If they're arrayed, it must be engineered to make the interference work toward a specific design objective:

http://www.jblpro.com/pub/technote/fat_wht.pdf

[Thom]

It's axiomatic - two sources playing the same program material will interfere with each other.

The Bozak tweeters were splayed.

If they're arrayed, it must be engineered to make the interference work toward a specific design objective:

http://www.jblpro.com/pub/technote/fat_wht.pdf

You always here of multiple woofers coupling if placed close enough together.
I don't have the technical understanding to make that my statement, or to rebuke it.

[Zilch]

Subwoofers, yes, mutual coupling below a specific frequency, Thom.

It's in the Eargle pro sound system design manual here:

http://www.jblpro.com/pages/tech_lib.htm

Even those interfere with each other, but it's pretty hard getting much differential distance to the listener in comparison to low frequency wavelengths when they're both mounted in the same box.

They can be "steered" with delay or placement offsets in separate boxes, tho.... :yes:

[ecl86]

Zilch, how about this:

I would cut out the front panel and put in a new baffle. Make a 15" hole for a subwoofer - using a plate amp driving it, a 12" for 2213H running fullrange (I believe 2213H is designed to run fullrange in 4312C), and a horns/drivers using one of those $10 wave guide from JBL - and a BMS 4550 driver (or some other driver that you think may be good for what i need) crossing at 1500hz with just a simple capacitor.

Not sure which 15" woofer to use for this seal box though. Please let me know if this plan sound OK and please give me some suggestion for a good 15 incher that would work well for my need. Thanks.

[Zilch]

I'm trying to avoid chopping out the front baffles.

You'd need a subenclosure behind the 2213H

With two identical 12s, you should be O.K., if one is being used as a "helper," i.e., just augmenting the low frequencies, as I suggested above.

Depending upon the size of the cutout for the 8", the round OASR "Dr. Seuss" horn may be a better choice than the $10 PT waveguide, which is 6.5" high external, and may not cover and seal the hole.

In any case, just a capacitor is not likely to approach comprising an optimum highpass filter. The BMS will play HF better than most other compression drivers under those conditions, though....

[Thom]

Subwoofers, yes, mutual coupling below a specific frequency, Thom.

It's in the Eargle pro sound system design manual here:

http://www.jblpro.com/pages/tech_lib.htm

Even those interfere with each other, but it's pretty hard getting much differential distance to the listener in comparison to low frequency wavelengths when they're both mounted in the same box.

They can be "steered" with delay or placement offsets in separate boxes, tho.... :yes:

I'm reading. You must be retired.