'sabout time for a China Syndrome Center Channel

[Paul Carmody]

Between being swamped at work, taking a night class, and the Chicago climate, it's been a real challenge to get this thing going. But I'm a man of my word, and I promised several individuals that it was, indeed in the works. On "thawing-out days," I snuck in the time to build the cabinet and cut the baffle. (The cabinet dimensions, by the way, are exactly the same as the Dayton .75 cu ft cabinet. The woofers are pretty much placed as close as I could get them to avoid off-axis nulls)

As you can see from the photo, I used the "Pete Schumaker method" for secure, airtight baffle attachment.

Working on the "Alpha" version of the crossover, which was actually one of the easiest XO's I've ever done--probably due to the lack of a need for BSC. Maybe I ought to do more designs with woofers in parallel!

Really not a whole lot to tweak here. However, every time I work with this Vifa Logic tweeter, I forget that it's got a lot of 10 KHz bite to it, and needs a bit of "mellowing" EQ so that it doesn't bring attention to itself. So I'll fix that for the "Beta" version, listen for a few days, and should have it rolled out by early next week.

Thanks for yer patience.

[mike1234]

Hey Paul... What will that configuration do to the lobe pattern?

[Hal H]

Good news Paul! I'm anxiously awaiting. Sounds like there'll be 2 Silver Flutes and one Vifa in the box to complement the LRs.

Hal H

[Paul Carmody]

Hey Paul... What will that configuration do to the lobe pattern?

Well, the idea was that the C-C distance of the woofers was close enough so that the design wouldn't suffer large nulls when listened to off-axis.

But I was a dummy last night. I used very similar shallow slopes on it like I did the original Orient Express and China Syndrome, and I really liked the way it sounded. Even with the toughest vocal material I use to voice speakers, I couldn't find any problems with its performance. It was spot-on. But then I realized that the whole shallow slope thing was not going to work with the sideways MTM. It was measuring a 2.5 KHz null after moving about 30 degrees off-axis--not that I needed to measure it, it was clearly audible. (But vertical off-axis performance was quite excellent. Only a dip of a few dB at 5 Khz.)
I forgot that I NEED to cross as low as possible (and with steep slopes to keep the tweeter happy), so I had to scrap that XO. Oh well. Take 2 later tonight.

[Paul Carmody]

I suppose it shouldn't be a surprise. The China Syndrome took a lot of toil to get right, so it only makes sense that the matching Center Channel would pose the same sorts of challenges.

But it works, and it sounds pretty! (put that adjective in an audiophile rag) This tweeter is quick to sound abrasive, so it took a lot of care (and willingness to scrap several otherwise good designs) to get the XO right so that the tweeter didn't "make its presence known." I am very satisfied with the final result; I've been working with a lot of metal cones lately and I forgot how "comfortable" paper cones sounded.

The crossover is actually somewhat close to a "textbook" 3rd order Butterworth filter. The drivers sum in phase quadrature and there is a slight bump at the XO frequency, which means that the driver responses sum flat when you move slightly off-axis. The FR remains mostly flat (-3dB) to about 40 degrees, where you start getting a dip around the XO point. I have some measurements, so I'll put those up on my webpage or something later on. For now, all I have is this XO diagram and the box drawing. If someone needs me to write up a BOM or something, just ask.

<dusts off hands, breathes a sigh of relief>

[brianpowers27]

The drivers sum in phase quadrature and there is a slight bump at the XO frequency, which means that the driver responses sum flat when you move slightly off-axis. The FR remains mostly flat (-3dB) to about 40 degrees, where you start getting a dip around the XO point. I have some measurements, so I'll put those up on my webpage or something later on. For now, all I have is this XO diagram and the box drawing. If someone needs me to write up a BOM or something, just ask.

<dusts off hands, breathes a sigh of relief>

Nice looking CC. Did you use real wood or mdf/veneer? Does the 40degree off axis dip come from phase or power response? Are the posted measurements simulated or actual?

[Paul Carmody]

Nice looking CC. Did you use real wood or mdf/veneer? Does the 40degree off axis dip come from phase or power response? Are the posted measurements simulated or actual?

The cabinet is just plain MDF (I've decided to start building "reusable cabinets" so I can try different baffles and driver combos). The baffle is made from some scrap furniture plywood--hence the pretty "blonde" veneer on top. The driver measurements are taken from 1 meter, with the tweeter as the listening axis.