MTM Design

This Section Last Updated: 5-6-2005

For the MTM i am not going too go into as much measurment detail as i did for the two way. The measurements were very similar. The only real difference is the MTM is much more effecient then the two way.

The MTM design uses the Silver Flute 5.5" 4 Ohm non sheilded drivers wired in series to achive a 8ohm load. It also uses the Vifa D27TG-15-06. I did not use sheilded drivers becuase these will be uses around a large rear projection TV.

Box Dimensions

I used Acusta Stuff available from Parts Express and i used what i would call a medium stuff. It is not heavy like i would a sealed box. It is not light and minimal. I would say it is about 3" thick layer of teased stuffing glued into place along the back wall.

The port is a 2" ID PVC pipe that is 4.69" long. It is cented right in the middle of the rear of the box.

After building the box, inserting the stuffing, glueing in the port and mounting the drivers i measured the box alignment. Note the Fs (F3) is a nice low 33Hz and Qt is a nice punchy .8

The off axis response of the MTM was very similar to the two way. For this design i also targeted a 3500 Hz crossover point using 4th order LR networks.

Final XO for 8ohm system

After loading the woofer and tweeter responses into a SE project. I came up with this crossover. It ended up being very similar too the two way crossover, but with much less padding on the tweeter.

Note the impedance at 8k did dip into the 6.5ohm region. I dont feel this will be a problem.

Final XO for 4ohm system

You asked for it and you got it. This is a crossover for an MTM that uses the 8ohm drivers wired in parallel. So create the MTM box and toss in the 8ohm drivers wired to this crossover. I have to give special thanks to Bob Grayton for the help with this crossover. This crossover i went for a lower crossover point of 2600.

Below is also a parts list with the exact parts and part numbers that i used in the crossover. You can get these parts from Parts Express.

Note that with the inductors i included their resistance.

Woofer Network
L0 255-252 1.1mH 0.57ohm
C2 027-568 10uF
R3 044-2.7 2.7ohm
L4 255-204 0.13mH 0.16ohm

Tweeter Network
L7 255-206 0.15mH 0.16ohm
L9 255-202 0.1mH 0.13ohm
C12 027-560 6.8uF
R13 004-2.7 2.7ohm

Project Sections:
Silver Flute Home Theater System
1. Box Building
2. Near Field Measurments of Two Way
3. Near and Far Measurements of Two Way
4. Crossover Notes on Two Way
5. MTM Design
6. Final Listening Notes

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