RS/VIFA/TB MTtTMW build

[Digisan]

Here is a system I built in my apartment. I don't have access to a woodshop right now so I decided to put together a system using PE cabinets. I reinfored the walls of the cabinet with extra braces made of square 1/2"X1/2" hardwood strips, a lot of them!!! I usually flush mount all drivers but I just couldn't run a router in my living room. Driver compliment is as follows: RS225-RS100(2x)-Vifa D26NC55(2x)-Tang Band 13-1761S. I modifed the D26NC55 by gluing the dome housing to the heatsink/magnet structure, then I removed the faceplate. The TB 13-1761S is also modified by removing the phase plug and trimming the lip that holds the phase plug in place flush with the dome surround. The off axis dipersion is much better without the phase plug, however this creates a peak that must be corrected in the frequecy response. It is a 4 way active system using a pair of Echo Audiofire 8 sound cards, ART Teknika Console, Thuneau Frequency Allocator, Voxengo Delay, and Voxengo Pristine (room correction). All XO slopes are 4th order acoustic filters at 350, 1700, and 7K. The XO was developed using LinearX LMS and ARTA. Here are some pics and an FR graph. Unfortunately I don't have the off axis graphs for these speakers (I screwed up and deleted them), which are outstanding. The front wall is empty because I have a video projector, a screen is going up soon...







Rob

[HareBrained]

Wow. That's a complicated design.

Why the dual D26+TB tweeter combo? Most people consider the D26 a great driver to 20kHz and wouldn't think of not using it all the way to the top.

[Jonasz]

Cool system!

I'm also intrigued by the MTM-tweeter configuration. Can you describe the sound they're making?

[Digisan]

Wow. That's a complicated design.

Why the dual D26+TB tweeter combo? Most people consider the D26 a great driver to 20kHz and wouldn't think of not using it all the way to the top.

I used the TB 1/2" tweeter for the top end to even out the power response at the top end. 1" dome tweeters off axis dispersion typically falls apart around 10K, adding 1/2" dome will extend that to around 20KHz. It may seem subtle at first but there is no doubt in my mind that having even power response out to 15K is essential to high SQ. Testing without the TB 1/2" confirms that these speakers have great sound and are very flat out to past 20KHz. My friend, who owns a pair of Orions, was quite baffled at how good they sound. Granted this is NOT and optimal way of building this configuration. The top cabinet should have a taller baffle. The compactness of this configuration, I believe, is essential to SQ.

[Digisan]

Cool system!

I'm also intrigued by the MTM-tweeter configuration. Can you describe the sound they're making?

I used mostly what I had on hand to build them. Mind you I am biased, but I think they sound fantastic. I thought they would sound very good, I was surprised that they sound excellent, bordering on ridiculous. Imaging is pinpoint and rock solid. Everything sounds superb besides the low end, two 12" woofers would have been better to match up with the rest of the MTtTM. The low end still sounds good, but at higher volumes you can hear some compression in the 8" woofer, as was to be expected from a small driver. My advice for anyone who wants to build something similar is to find a small surface area tweeter that has excellent off axis dispersion. Most super tweeters do not fit this criteria. Frequency extension is usually the selling point of super tweeters, not excellent dispersion. There are only a few tweeters that I know of that can provide the proper dispersion needed.

Rob