ScanSpeak WMTMW Center Channel

[jkleinau]

Need a second opinion on this project I've been contemplating. The drivers I have selected are 2 scanspeak 22W/4534G00 woofers, 2 scanspeak 12W/4524G woofers, and 1 scanspeak D2606-9220 tweeter. The 12W woofers and the tweeter would be in a vertical MTM arrangment. Woofers will be wired in series. I have attached a screenshot of the PCD session. Any suggestions/thoughts would be helpful. Thanks!

[cjd]

How did you acquire the data?

What you have there isn't really usable to tell much - can't even tell the scale used on the various graphs.

I suspect the small shelf (breakup?) in the mid will be audible especially isolated by a small dip on either side - the dip is probably caused by you having to work around ithe breakup resulting in overall lower output NOT counting the breakup through the mid-tweeter region.

The mid impedance makes me want to look deeper.

Can't really say a whole lot more based on the attachment. It may have been significantly reduced in size/usefulness by the forum software, not sure.

[Face]

I wouldn't use a vertical MTM in a center. Use a single mid and place it under the tweeter, you'll have better off axis response.

[cjd]

I wouldn't use a vertical MTM in a center. Use a single mid and place it under the tweeter, you'll have better off axis response.

I totally overlooked this, but agree 100%.

[jkleinau]

Thanks for the input. I obtained the data using SPL Copy on the SPL/impedance graphs on the Madisound website... not ideal, but until I purchase the drivers and can obtain my own measurements, it's all I have to work with (was unable to find FRD/ZMA files for these particular drivers). I hadn't thought about the off-axis response with a vertical MTM, but now that you mentioned it, it makes sense. Will try remodeling this with a single 12W/8524G woofer as the mid in a WMTW arrangment. Trying to keep impedance close to 8 ohms nominal, even though my amp is capable of driving 4 ohms no problem (Outlaw Model 770).

[Juhazi]

Anyway, it will be a HUGE center speaker! How big is your room? What kind of main speakers do you have?

This configuration is perhaps the best for a horizontal 3-way (WT/MW) Statement Center Channel

[jkleinau]

room is roughly 15 x 25 with 8 foot ceilings, this will be going under an 80" sharp lcd tv

[Juhazi]

Obviously You don't have enough height for a vertical WMTMW (which is overkill anyway)
If you are not a very experienced designer, you should consider these proven center designs

http://www.htguide.com/forum/showthread.php?31523-Frodaddy-s-custom-Statement-center-WMM-TW

http://www.htguide.com/forum/showthread.php?27552-Statements-Mini-Statements-Center-Channel-Build-Thread

http://www.htguide.com/forum/showthread.php?11475-Modula-MTM-Center-Channel

http://www.zaphaudio.com/ZA5/

[fbov]

+1 on proven designs, as long as you're still exercising paper, haven't bought drivers, and have access to a wide range of driver options. Geographic location can limit your options...

+1 on Modula MTM CC, from personal experience. A worthwhile CC if space only accomodates a 2-way.

+1000 on graphics large enough to read!

If you are wedded to being the designer, let me point out one very important thing you won't notice unless you look for it - driver sensitivity.
- When designing MTMs, dual drivers add +3dB, but 4 ohm drivers will be wired in series, -3dB for double impedence, so it's a wash. but it's still a 92.4dB driver!
- The mid's rated at 88.8dB, and it's a 4 ohm driver, too, so you'd need 2 for an 8 ohm load, but again, dual drivers in series are a wash, so you're still stuck with a 3.6dB hotter woofer.

One can use baffle step compensation to knock down the woofer, but only as long as the speaker will not be placed close to boundaries, walls, floor, and for a CC, the TV screen. That's unlikely, IMHO, leaving you with a nasty problem of a too hot woofer.

PCD would catch this is you were using data you'd captured. FR curves taken with the same driving voltage will be a different levels based on sensitivity. Do you have an impedence rig and mic system?

HAve fun,
Frank