how would you build this center speaker?

[BARRACUDA1968]

I've been searching for a center channel for a while now and because I use 4 amt 1 towers with heil air motion mid range tweeters I figured matching up a center channel would be hard to do. Plus I want something that size wise kinda matches my TV and current set up. I decided to build my own center speaker. I called ESS and ordered two heil air motion tweeters and crossovers today. Here are the specs of the tweeter midrange. It looks like to me they cross them at 800hz? take a look!

Power Capacity 400 Watts 400 Watts
Frequency Response 30-23+3db 35-23+3dB
Crossover Frequency 800 Hz 800 Hz
Efficiency: SPL @1w/1m 93dB 91dB
Midrange Control 800Hz to 5KHz(+3dB to-6dB) 800Hz to 5KHz(+3dB to-6dB)
Brilliance Control 5KHz to 23 kHz (+5dB) 5KHz to 23 kHz (+5dB)
Low frequency 12'' Polypropylene 12'' Polypropylene
Bass Radiator 12'' EPS Styrene Foam / laminated 12'' EPS Styrene Foam / laminated
Heil Air-Motion Total Radiating Area 21 1/2 sq.in. Total Radiating Area 21 1/2 sq.in.

I want to use some drivers in the speaker to smooth out the ESS tweeter's. I will set the center channel to small and cross the bottom at 90hz. So basically I need to cover from 90hz to 800hz. My thinking is probably a couple 8" drivers?? I'm going to build the speaker in a stereo set up ( 2 ess tweeters in the center and drivers on each side with independent crossovers per side ) so I don't have trouble with ohm's and then power it with a proton D1200 split off the pre amp center RCA.

Please give me your feedback on what I am trying to do here and any suggestions on an appropriate driver to use or multiple drivers? what ohm driver do I want? I want this speaker lighting fast with tight base.

Thanks Brett

 

[jaxvon]

Do they also give T/S parameters, frequency response plots, and impedance + phase plots? Those would be most useful. As for a midbass driver, you should be looking at high-quality 6.5ish drivers. What you get is dependent on what you want to spend. Seas makes a killer 7" midbass driver, but it has a resonance aroun 5kHz which needs to be accounted for. There are many other great offerings from Vifa, Scan-Speak, Peerless, and even Dayton.

 

[j_garcia]

6 1/2" drivers would probably be good, but you could also get away with a good 5 1/4 if size will be an issue.

Check out the midrange drivers offered by Adire (see sig).

I don't know about the overall design theory though. Are you thnking M-T-T-M or T-M-M-T? Because there are a lot of design considerations for a design like this, and without the equipment to measure the response on and off axis, the results may not be as desired. The positioning of the drivers on the front baffle and the size of the baffle are going to be criticial to the design.

 

[BARRACUDA1968]

I will call ESS tommorrow and get that info on the specs. My thinking is to set it up like this W T T W or maybe W T W T W ?? if I used multiple woofers how do I stay out of trouble with going to low on the ohms? what ohm rating should I start with on the woofers? 4-6-8 ?

One other thing, what type of wood should I use? I would like to use a hard wood if possible. I will sand smooth and paint black and then shoot a clear coat on it.

 

[j_garcia]

With each side being separate and running off an individual channel as you said above, you shouldn't have to worry about impedance too much, but you will need to know what the impedance of their portion will be to start with, then determine what impedance midrange driver you will want to use. The M(id)-T-M-T-M would be a bad idea, or at least very difficult to get to sound right. I've only seen two speakers designed: T-MMM-T; one is the Axiom VP-150 center. If anything, I'd probably shoot for something like that, and then you would need to tailor the x-over and the impedance of the drivers to achive the impedance you want. That would also mean you would no longer have a 50/50 split for the amp, but you could make it so one channel powers the mids and the other the highs.

The problem with a design like this is that the common drivers will tend to cause "combing", where the drivers playing the same sounds will actually cancel each other out at certain points within the listening area. That is why I say the location and spacing will be important.

 

[BARRACUDA1968]

ok, that sounds a little to involved for me LOL so then should I just do a W T T W set up? and forget the center woofer? thats fine with me. The ESS speakers are 6 ohm, does that mean I want a 6 ohm woofer? I looked at the link in your sig and that woofer looks pretty tempting. Because these ESS tweeters have syuch a broad range am I going to have trouble matching them with a smaller woofer? hence causing the cancelation that you mentioned?

 

[j_garcia]

The crossover will take care of issues between the ESS and whatever midbass driver you select. The cancellation comes from two of the same drivers being on the face of the speaker, playing the same sound. Think of it like dropping two pebles in water a foot apart at the same time - in the areas where the waves intersect, you will get some cancellation. It's more complicated than that, but does that make sense?

One thing I'd do also consider, is making a few front baffles so you can try M-T-T-M and T-M-M-T to see what ends up sounding better.

GR Research, the designer of my speakers, also sells a very nice 5 1/4 midrange for a very reasonable price.

 

[rmcdo]

I've been searching for a center channel for a while now and because I use 4 amt 1 towers with heil air motion mid range tweeters I figured matching up a center channel would be hard to do.

How did this project turn out? I too have four ESS Amt-1s as my main speakers and would like to get a center channel speaker that matches them.