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  1. #1
    Forum Regular Swerd's Avatar
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    AR.com drivers in an MTM design?

    It has been about 5 months since I built my first DIY speakers, a pair of AR.coms. I keep them in my bedroom as my 2nd system, but in fact they have become my preferred system for listening to 2-channel music. I know, it may be due to the new toy phenomenom, or differences in the receivers I use, or the room itself, but currently, they are my favorites.

    I was wondering what to build next in my newly acquired hobby of DIY speaker building. The AR.com components were bought as a kit from Madisound along with their preassembled crossovers. The enclosure was bought from Speaker City. So I am still pretty inexperienced. Iíve now begun to absorb Vance Dickasonís book, and with a new router and other tools have begun to build boxes out of scrap wood and otherwise make a lot of sawdust.

    Has anyone tried to use the same Peerless drivers (850122 woofer and 812687 tweeter) in an MTM design? Iíve found other MTM designs on the internet using several different drivers, from Vifa, Dayton, or Seas, but nothing for Peerless. In my innocence, I think that box volume and port size for such a speaker should be pretty straight forward. But what about the crossover? Iíve read enough to understand that crossover design is a critical step, and requires considerable trial and error before it is really good. I donít have any test equipment, and would prefer to use a tested crossover design, like I did in the AR.coms.

    Is there any reason why these Peerless drivers should not be used in an MTM design?

    Can I directly modify the Ed Frias designed crossover for the 2-way into an MTM crossover, or is it better to start from scratch?

  2. #2
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    MTM design really needs a new Crossover

    Swerd,
    The problem is, the single Peerless midwoofer is 8ohms and the crossover was design for it alone. If you use two in parallel, the impedance will drop to half (4ohms) and the crossover will not be matched, using two in series will increase the impedance to 16ohms, not good either!

    Now that said, Michael Hartwig (MCH) a fellow DIY builder built a MTM center channel DIY using two shielded Peerless drivers (in parallel) that were supposed to be the equivalent to the original unshielded drivers used in the kit, and using the same crossover said the speaker sounded very good. You might post a request asking Michael for the driver numbers and more details.

    My first recommendation would be to find a pre-designed MTM kit and do it right. Whether they would match your DIY's is another question . Success!

    Ed Frias
    EFE TECHNOLOGY Speakers

  3. #3
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    I may be way off base here, but...

    Why not use another Peerless 8 ohm woofer, wired in parallel, halve the values of the inductors in the woofer circuit, and double the value of the parallel capacitor? Because you'd now have an additional 6dB gain from the parallel woofers, remove the resistor in the tweeter circuit. It might be necessary to use, say a .8mH and .15mH inductor in the woofer circuit to cut baffle step compensation just a tad.

  4. #4
    Forum Regular karl k's Avatar
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    I just got started on mine.

    Quote Originally Posted by Swerd
    It has been about 5 months since I built my first DIY speakers, a pair of AR.coms. I keep them in my bedroom as my 2nd system, but in fact they have become my preferred system for listening to 2-channel music. I know, it may be due to the new toy phenomenom, or differences in the receivers I use, or the room itself, but currently, they are my favorites.

    I was wondering what to build next in my newly acquired hobby of DIY speaker building. The AR.com components were bought as a kit from Madisound along with their preassembled crossovers. The enclosure was bought from Speaker City. So I am still pretty inexperienced. Iíve now begun to absorb Vance Dickasonís book, and with a new router and other tools have begun to build boxes out of scrap wood and otherwise make a lot of sawdust.

    Has anyone tried to use the same Peerless drivers (850122 woofer and 812687 tweeter) in an MTM design? Iíve found other MTM designs on the internet using several different drivers, from Vifa, Dayton, or Seas, but nothing for Peerless. In my innocence, I think that box volume and port size for such a speaker should be pretty straight forward. But what about the crossover? Iíve read enough to understand that crossover design is a critical step, and requires considerable trial and error before it is really good. I donít have any test equipment, and would prefer to use a tested crossover design, like I did in the AR.coms.

    Is there any reason why these Peerless drivers should not be used in an MTM design?

    Can I directly modify the Ed Frias designed crossover for the 2-way into an MTM crossover, or is it better to start from scratch?
    I, like you, wanted to match an MTM with the AR.com's so I did some number crunchin' and threw together a working model. I don't think I'm too far off, but got some tweakin' to do before I post results and circuits. I'll try to get something goin' this weekend for ya.

    As Ed stated, maybe Michael can shine some light for you.
    Karl K.

    The shortest distance between two points is a straight line... in the opposite direction.

  5. #5
    Forum Regular karl k's Avatar
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    I don't think you're too far off base, Mr Hertz.

    Quote Originally Posted by Dick Hertz
    Why not use another Peerless 8 ohm woofer, wired in parallel, halve the values of the inductors in the woofer circuit, and double the value of the parallel capacitor? Because you'd now have an additional 6dB gain from the parallel woofers, remove the resistor in the tweeter circuit. It might be necessary to use, say a .8mH and .15mH inductor in the woofer circuit to cut baffle step compensation just a tad.
    That's the model I have now only I haven't got the tweeter resistance quite right yet. I'll have to throw the setup on Speaker Workshop and measure what's goin' on with the tweeter. I believe it's do-able and I am close, but not sure about the effects of impedence change from the extra woofer on the tweeter x-over. By changing the overall "system" impedence, would that effect the tweeter x-over? That will be the question I look to answer.

    It's good to hear you! You must have a mountain of saw dust in that shop of yours!
    Karl K.

    The shortest distance between two points is a straight line... in the opposite direction.

  6. #6
    Forum Regular Swerd's Avatar
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    Ed, Dr. Hertz, and karl

    Thanks for all your responses. I appreciate your knowledge and experience.

    Karl, I'm looking forward to your results when they're ready, but don't hurry on my part. Do it when you can. In the mean time, there is lots I need to learn. I have yet to tackle putting on veneer or any other kind of serious finish. I'm beginning to understand how easy it is to let your plans get way ahead of your skills in this hobby, but hey, it wouldn't be any fun if I just built more of the same old thing!

  7. #7
    MCH
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    When I used the Peerless shielded speakers in my MTM I used 2 of Ed's crossovers. One was a complete crossover for the tweeter and 1 woofer. The other woofer I used a crossover with only the woofer section. My speaker wire from the reciever is doubled to allow me to hookup both crossovers. My reciever has no problem with this load. When I do a test tone, the MTM is a little deeper in tone from the other four regular ARdiy speakers. I suspect because of the 2 woofers. I also did a center channel for my nephew using the Peerless shielded speakers (tweeter and woofer) using Ed's original design and I couldn't tell a difference in sound. My nephew is very pleased with his 5 ARdiy's (I call them E&M speakers) and a Tempest Octagon sub (140L) that I built for him.
    This fall (after my annual summer of golfing, fishing, hiking...) I may build another pair of Ed's speakers with another new cabinet design I have on my drawing board.

  8. #8
    Forum Regular Swerd's Avatar
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    The only shielded 6.5 inch Peerless driver I can find on Parts Express is the 830378 http://www.partsexpress.com/pe/pshow...=297-602&DID=7 Did you use that? It doesn't seem similar to the 850122.

  9. #9
    MCH
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    I get my stuff from Solen's Canada (http://www.solen.ca/). The woofer is 831975 (Peerless number) and the tweeter is 811978.
    Hope this helps.

  10. #10
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    Boy, you got that right!

    I am just buried. One project about 2/3 finished and five more I haven't even started yet. It's going to be a busy next couple of months!

  11. #11
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    Peerless has a 4 ohm version

    Solen.ca has a 4 ohm version of the 850122; it's the 850123. Here on this page: http://www.solen.ca/pee.htm
    Could a person use two of these in series for mtm?
    Peerless website doesn't show it but there it is at Solen.ca...

    Dean

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