$300 8'' Classic MTM That Rocks

[1Michael]

This is a fun little (in my world) $300 8 inch MTM project I stumbled upon that uses the Dayton classic drivers, 8" Woofer 295-310 and the 1-1/8" Silk Dome tweeter 275-070. It can be ported or sealed.
The internal dimensions are 49” x 16.5” x 9.5” although I did modify this so that the longest piece of plywood would be 48’’ which happens to be the width of plywood in my neck of the woods. The port is 4’’dia x 4.5’’
The baffle of course is 2 layers, inside being mdf and outside is plywood, stained with walnut (to cover all my woodworking imperfections of which there are usually many) and then water based Poly to seal things up. I used 5 braces inside, with 2 ea. 3” holes to breath.

What would really be cool is if someone could redo this Xover to be more of an HTGuide forum quality Xover.

Here are some pictures of the finished product but don’t look too close cause you will see all the mistakes.

Images not available

So how do these sound? Well I have been listening to JCD’s RS 3ways for awhile now, and these of course are not as accurate, nor does this sound as good. Also I would not consider these as ‘Audiophile’ quality.(Yes Thomas I know) this would be comparing apples to oranges since the RS 3way’s are…3ways and use the reference series drivers, and more care was put into the 3way’s Xover. I just wanted to give a little comparison with something others might know. But at $300 these do pound the house nicely and I really liked the sound. I found that the silky tweeter is very seductive to listen to, in that the sound stage presented is very smooth, and when I move my head side to side the sound does not change as much as the rs tweet seems to. If your budget is tight and you need something that goes louder than usual while still putting out quality sound, I can absolutely recommend this project :T

Here is the archive for this project. http://www.angelfire.com/music5/audio0/

Below you will find my suggested list of parts for the DJ8MTM all from Parts Express...



Part Number Description Qty. Price Ext. Price
004-20 DAYTON 20 OHM 10W NON-INDUCTIVE.. 2
027-344 15uF-100V NON-POLARIZED CAPACIT.. 2
027-354 50uF-100V NON-POLARIZED CAPACIT.. 2
027-430 DAYTON 12uF-250V POLYPROPYLENE .. 2
266-313 .27mH 14 GA. PERFECT LAYER INDU.. 2
266-320 .40mH 14 GA. PERFECT LAYER INDU.. 2
266-812 .33mH 18 GA PERFECT LAYER INDUC.. 2
275-070 DAYTON 1-1/8" SILK DOME TWEETER.. 2
295-310 DAYTON 8" WOOFER .. 4
027-429 DAYTON 7.5uF-250V POLYPROPYLENE.. 2
004-2.4 DAYTON 2.4 OHM 10W NON-INDUCTIV.. 2
004-4.7 DAYTON 4.7 OHM 10W NON-INDUCTIV.. 2
027-348 Dayton 22uF 100V Non-Polarized Capacitor 2
Notes

Parallel the 50uf and the 22uF to make the 72uF cap
Use the 15uF for the 16uF
Use the 7.5uF for the 7.2uF
Use the 12uF for the 11.5uF
Use the 2.4 Ohm for the 2.5 Ohm
Use the 4.7 Ohm for the 4.5 Ohm
Use the .4mH for the .45mH
Use the .33mH for the .35mH

[Undefinition]

But at $300 these do pound the house nicely and I really liked the sound.

Yeah, dual 8" woofers will do that! :B

BTW, in regards to a "refined" crossover, where do you live?

[1Michael]

I'm in Chesapeake Virginia.

[M.Roberts8]

I built them quite awhile ago I made some ghetto boxes that were 56L then did the larger ones and if I were to build them again I would go with the smaller 56L ones you don't gain enough to justify the bigger enclosures IMO. My nephew has them now and he really likes them. I believe they need a better xo too.

What would really be cool is if someone could redo this Xover to be more of an HTGuide forum quality Xover.

The pic is small so you don't see all my screw ups ops: And there is allot of them.

[dynamowhum]

I would really like to see a comparsion between these and the tri trix speakers. They are very close in price.

[1Michael]

I would go with Curt's design...like I said the Xover could use some help :T

[CupCak3]

do you happen to have any response plots?

[Undefinition]

do you happen to have any response plots?

This design, the Dayton 8, was a computer-optimized design done in CALSOD by Wayne Jaeschke. It was pure simulation. I've always wanted to hear the design, then have a crack at it with actual measurements and my own ears. But Virginia is too far from me.

[bluewizard]

I'm curious if you can expand more on the crossovers. I confess precise crossover design has always been a bit of a mystery to me.

But using standard design calculators, it appears that the bass crossover is a 6db/oct with a notch filter to eliminate the peak at 2.2khz in the bass response. Again using standard calculators, the crossover seems to be 1400hz.

Now on the high side, we have a 18db/oct crossover, but the values mystify me. The best I can determine is that they are at about 2400hz. That seems to leave a small gap in the midrange. Well, not really a gap, but reduced output.

I realize you didn't design this crossover, but it would be nice to hear others, more knowledgeable than myself, comment on it.

I would think, depending on the center frequency of the notch filter, the low crossover could be moved higher, but again, I don't really know what I'm talking about.

Just interested in the comments of others.

Steve/bluewizard

[1Michael]

I have no testing capabilities at this time, but that will change in the near future. These speakers I built for my sister who is out of my state so I would not be able to test them even if I had the equipment.
I would guess that this Xover is probably a theoretical design in that it is not based on the normal testing, trial, error, more testing etc. that people here would use to create a good result. Having said that, I still very much liked the sound and I would really like to see someone take these drivers and create a more quality Xover.

[bluewizard]

I want to make sure you understand that I wasn't criticizing the crossovers or the design. I probably couldn't have done better. I'm just trying to understand them.

I find the Dayton Classic CD200 8" speaker to be very appealing, but have never been able to come up with a workable 2-way design. To stay away from the break up at about 2.2khz, and to stay in the most favorable working range, you need to crossover at 1khz or less. The only tweeter that will work that low is a large horn, which doesn't seem realistic for a 8" woofer or even two.

Using a normal tweeter, I've speculated that the highest I could crossover is about 1.6k to 1.8khz and still somewhat avoid the break up at 2.2khz. I'm even willing to over look the unevenness between 1k and 2k, since it is not that radical.

So, again, since you have a working design, that looks great by the way, this is a chance to see how this speaker can be effectively applied.

One problem I'm having, since I only have the most basic understanding of crossovers, is how the standard crossover and the notch filter will interact, if I move the crossover higher.

Again, all the crossovers I speculated, were just that speculation. The only real way to know what is going on is to test, and I confess I can't afford test equipment, although at some point in the future that may change (like when I win the lottery).

I hope if and when you get a change to test the speakers, you will post back with your results, as I'm very interested to see what you've achieve, and hopefully we can speculate on how to improve it, if that can be done.

Again, I'm interested in the design. But anyone can put speakers in a box, the real art and science comes in in the crossovers, which again, I admit is a mystery to me.

Steve/bluewizard