Kit 261

jkarhan1 · « **on:** 1 Jun 2006, 02:10 pm »

Could the Kit 261 be set up as an MTM ? Do you have an MTM design?
BTW what are the frequency charisteristics of the 261.
Thanks, Joe

Kevin Haskins · « **Reply #1 on:** 1 Jun 2006, 04:42 pm »

No... the 261 is a MMT design. I've done an MTM design with the Extremis & the Usher but it isn't published as a kit.

MTMs have limited dispersion on the axis of the drivers. The larger the drivers used and the longer the center-to-center distance the more response issues you have off-axis. The design I did with the Extremis was aimed at being used as a center channel. I crossed the Usher as low as I could reasonably use it and managed to get a good +- 15-degree window without response problems but after that you get some fairly strong comb filtering. It's an issue with any MTM layout of this physical dimension. The only thing you can do is push the drivers as close together as possible & cross to the tweeter as low as possible (with steep crossovers). In my design the Extremis is 11" center-center, which leaves just enough room to drop the Usher in between them. Baffle dimensions 22" x 9" (same size as PE 1.0 ft^3).

Here are the crossovers your free to use them.

Woofers in parallel.

Tweeter: There is one mistake on this drawing. The 0.39mH inductor should be a 0.35mH inductor.

Here is the simulated frequency response. I've measured the final design also (don't have the files on this computer) and the on-axis measurement is almost identical to this. The simuation shows the raw unsmoothed FR from the raw driver measurements so it would look smoother if I used my standard 1/6 octave smoothing for FR graphs.

jkarhan1 · « **Reply #2 on:** 5 Jun 2006, 09:20 am »

I actually need a center channel. Do you have actual plans for this speaker? willing to work something up?
Joe

kfr01 · « **Reply #3 on:** 5 Jun 2006, 03:01 pm »

And the LCR is too large, expensive, or otherwise not right???

Kevin Haskins · « **Reply #4 on:** 5 Jun 2006, 03:35 pm »

You can use the PE cabinet. Part Number: 302-750, 302-752 or 302-754.

The crossover components are all things I have in stock so just give me a call. Parts cost on the Crossover is about $40, woofers are $198 and the Usher is $67.15. Add a binding post, some polyfill, wire, gasket material & some woodscrews and there is another $15 so total would be $320 without the enclosure. PE sells the enclosure for $81.82.

I'd run it sealed. You give up a little extension but it has plenty of bass extension for a center channel running if you run it sealed.

jkarhan1 · « **Reply #5 on:** 7 Jun 2006, 09:53 am »

My limiting factor is it has to be less than 18 inches wide. So I would have to have the cabinets made. If 18 inches for the front baffel is OK?

Kevin Haskins · « **Reply #6 on:** 7 Jun 2006, 03:16 pm »

You need about 18.5" to fit the drivers. You may see a slight response variation but nothing earth shattering.

kfr01 · « **Reply #7 on:** 7 Jun 2006, 08:42 pm »

jkarhan:

If you're looking for a center to match some 261 fronts, what about trying a 61? Center channels don't need to be MTM design... The Extremis has more than enough throw to serve as the only midrange driver for a center channel in a normal sized room.