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/showd...number=295-320 and perhaps this horn here: http://www.partsexpress.com/pe/showd...number=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

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/Speaker...ries/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)...

[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/produc...ome/s5800.html

Specs here:

http://audioheritage.org/vbulletin/s...ad.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

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