MTM TL Project

[bostonflyer]

Just finished my MTM TL, ala D'Appolito, project. I used different drivers, partly due to money considerations and partly to try something different. I used Dayton DC160-8 61/2" midbass and Vifa D25AG-35 tweeters. I used 2nd order Linkwitz-Riley filters to crossover at 1800 Hz. The midbass impedance was equalized at 6 Ohms to match the tweeters.

At first I thought the system was a little metalic sounding, but after a few weeks of break in I was very satisfied with what I was hearing. The highs were crisp and accurate; the mids were pretty good, considering the drivers; the bass was a little weak, but acceptable. The sound stage was a little forward, but also acceptable. My over-all impression was very good bang for the buck ($350 including MDF enclosures and Solen/Mills/Jantzen foil
crossover)

I drive the speakers with an LM3886 Chipamp directly from a Sony ES series CD. The Chipamp seems to drive the 6 Ohm system quite well. Next project will be a DAC and Preamp.

Bob

[wintermute]

Very nice

I know what you mean about metallic sounding, I have heard those D25's before and didn't like them for that reason, maybe I would get used to it not sure...... I'm very much in the soft dome camp

Tony.

[GM]

Greets!

Interesting! This is the only Vifa tweeter I've auditioned that I thought sounded anywhere near close to 'accurate'. Oh well, I guess it's due to decades of listening to alum. diaphragmed horn drivers which are much more highly damped than a point source tweeter. If you're in an experimental mood you can lightly coat them with Damar varnish to damp their >20 kHz break-up modes a bit. Give them a few days to dry before energizing them.

When you say 'TL', do you mean ML-TL? FWIW, the Qts is a bit low for a ML-TL and way too low for a TL to get good LF extension so either would require some BSC to be tonally balanced in-room unless you designed them as a 2.5 way.

Anyway, lookin' good!

GM

[Scottmoose]

Is it me, or do these look similar to the Thor?

Not bad at all -very impressive in fact. How did you calculate the dimensions / TL type? Oh -one suggestion; if you still find the sound a bit forward, try adding a little series resistance to the mid-bass drivers, or even overall, in the lead from the amp. Only problem with that is, it might push your chip amp into clipping. Still, worth a try.
Best
Scott

[bostonflyer]

Hi Scottmoose,

The enclosure is a copy of the Thor. Since I know just enough to be dangerous about speaker design, I searched for lower-cost divers that were close in specs to the original. My plan was to give it a try and if I didn't like it I could spend the $ later on the Seas.

Thanks for the suggestion concerning the forword sound stage; I will experiment with it. I'm still in the process of tuning the line and experimenting with different amount of stuffing.

Bob

[Scottmoose]

I thought as much. They look very good to me!

One or two suggestions to try out / refinements. Joe seems to have got the Thor enclosure a bit mucked up, and using drivers similar to the originals, it'll have a significantly rising response over 100Hz. He appears to have forgotten paralleling two drivers doubles Vas, so the twin driver[s] see a half-sized enclosure. This gives the forward presentation and light bass you mention. Something interesting for you to try as you're still experimenting: temporarily disconnect one of the two mid-bass drivers. My bet is you'll find a flatter response with better bass performance and a less forward presentation.

With twin drivers, I reckon increasing the stuffing desnsity in the rear part of the line to 1 lbs to the cubic foot will help a bit. Some series resistance (probably about 5ohms) in the hot lead to the mid-bass units should help too, or better, try parallelling the resistor with something like a 2.5mH inductor which should tame it completely. Better bass response, greater soundstage depth and a less forward presentation should be the result.

Regards
Scott