efficient MTMs

[castlesteve]

I`m still looking for a new project to replace my Fostex single drivers and am looking at building some efficient MTMs. I have found Wayne Js Eros project which looks very nice but i`m wondering if there are any other plans out there to try? I`m going to be using a 300B amp giving me about 20 watts so i`d like something tube friendly also. Any ideas?
Steve.

[Jim Griffin]

Steve,

I recently completed a high sensitivity MTM which uses the PHL Audio 1240 midbass and Aurum Cantus G2 ribbon tweeter. It is 96 dB 1w/1m SPL and has a nominal 8 ohms impedance (the 1240's are 16 ohms impedance). The pair that I build is in a 1 cubic foot enclosure so the bass goes down to a 50 Hz F3 point (I'm using a subwoofer to go lower). A larger 1.5 cu. ft. floor model should have get down to 45 Hz. Very nice uncolored sound with much detail. Should be perfect with your amp.

Jim

[castlesteve]

Jim, Thanks for the reply. Those sound exactly like the sort of thing i`m looking for. Did you design the crossover yourself? Are you the Jim Griffin of linestage fame?
96db would be wonderful to attain and i`ll be building floorstanders so it looks like they may well go deep enough not to warrant a sub. Would you be willing to share crossover details so i can attempt a pair myself?

Many thanks, Steve.

[GM]

The last MTM I did was a ML-TL using dual Altec 416-8Bs and 500Hz 511 horn EQ shaped to 105dB/2.83V/m down to 40Hz. These were the L-C-R of a very high end HT. 20W goes along way with this system.

GM

[Jhovis]

I'd like to hear more about Jim's PHL MTM myself. I'm also looking for some tube friendly speakers.

[Jim Griffin]

For those who asked, the MTM design that I built started life as a design by Andre of www.e-speakers.com. His original was for a 1.6 cu. ft. floor standing enclosure. For the design that I built, I changed the tuning to a 1 cu. ft. stand mounting enclosure (see the finished Parts Express MTM box). Andre's crossover should work for either the floor stander or stand mount design.

The down side of this MTM is that the driver cost alone will run in the $860 -$950 range (check prices for the PHL Audio 1240s at both E-speakers and Zalytron) so it is not cheap. The 1240 driver has ears on it so flush mounting necessitates a more difficult job. But the sound is worth the effort.

[Greg B]

For something cheaper, instead of the PHL, try an MTM with a couple of the discontinued focal 'access' midwoofers zalytron has on sale. Don't let the low price fool you, I like them better than my PHLs. Take the money you saved and get the ESG3 instead.

The 'cheap' focals mesh with ESG3 ribbon much better, perfectly in fact. Many of the models are 12 ohm, if that will help.

Here's a controversial thought: my ribbons really needed to be padded down a few db to sound good. I don't know if there is ringing between the crossover and the step up transformers or what. Padded down and used in 'normal' mid efficiency speakers they sound as wonderful as the raves you often hear.

I've had better luck with horns for 100db+ high SPL systems.


Greg B

[Bricolo]

Originally posted by Greg B
For something cheaper, instead of the PHL, try an MTM with a couple of the discontinued focal 'access' midwoofers zalytron has on sale. Don't let the low price fool you, I like them better than my PHLs. Take the money you saved and get the ESG3 instead.

are those car speakers? Can you tell us the reference?

[Greg B]

No, not car drivers. I don't think they were sold in the French market. These were 'plain' coated paper cone drivers that Orca (USA Focal distributor) marketed 8 or 9 years ago. The were billed as beginner's drivers because most had very smooth frequency response and were relatively inexpensive. They also tended to be relatively high efficiency and high impedance.

Many had nearly perfect impulse response, which might explain why they blend seamlessly with ribbon tweeters. Shame the discontinued them. I guess they didn't have the sex appeal that exotic cone materials had.

Anyway, available here: Zalytron

The 7C looks like a good candidate for a high efficiency MTM, or the 6A. The "A" series are straight coned and the C series curvilinear.

GB

[castlesteve]

Greg.
That`s an interesting idea . I`ve not looked at the Access drivers before but i do like Focal drivers. Where are the esg3s available from? What size box would you reckon i`d need for a pair of the 7Cs. I was thinking i could get away with a pair of 2cu ft floorstanders. Thanks for the idea.
Steve..