Loudspeaker Designs and Articles for the DIY Enthusiast
This time I built the enclosures out of ¾” MDF. Birch plywood could also be used, but MDF was what I had on hand. Bracing is provided by the center panel
that runs near the length of the enclosure. This is a mass loaded transmission line with the port loaded in the center of the line. This provides the maximum
port output at this location. The line is fully stuffed except near the port mouth. I recommend you start with 36 oz. of acousta-stuf, polyfill, or similar and add
or subtract to taste.
One of the things I did differently this time was to put a single 0.5 woofer above the MTM. This helped to balance the vertical off axis response, and also
kept the tweeter at near seated ear level.
All these woofers required a substantial port. The 4" flared port consists of the PSP 4" inner and outer flares and a coupling ring. No tube is necessary, and
the finished length is about 6" If you want to substitute a straight wall port, a 4" PVC pipe 5" long will suffice although it may make some extraneous sounds
at higher SPL's.
Tips and Tricks:
One of the most requested variations of the Stentorians -which I unfortunately could not provide, was a matching center channel. the vertical lobing effects
of that design simply did not lend itself well to center channel use. However, the crossover topology in this design is better in this regard. Should one want to
flank the MTM with a pair of the woofers, and lay it on its side, you have my blessing. As a ‘sound bar’ it’s a bit on the large side, but I dare say its other
attributes should silence the naysayers. –Or maybe you just won’t be able to hear them…
Alejandro flush mounted the woofers in his enclosure design, and placed them on a separate baffle, doubling up the front baffle thickness. I did not flush
mount the prototypes, as flush mounting all those pincushion frame woofers wasn't going to fit into my time frame. -Yes, and I was being lazy as well. If you
do flush mount, I'm certain it would tend to smooth out the response a bit, but if you don't, I certainly don't think the lack of flush mounting caused
irreparable harm. -All posted measurements were done with non-flush mounted drivers.
-Now if a jig for flush mounting was only available....
|A high sensitivity
high SPL design
All pictures courtesy of Alejandro Fernández Valdespino