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  1. #1
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    Pictures of my Tri-amped Open Baffles

    The main driver ( Beta 12LTA ) is powered by 2a3 SET mono-blocks. The Alpha 15 inch H-frame woofers are powered by solid state Dayton APA150 mono-blocks. The super tweeters are powered by a Dayton DTA100 tripath amp. That's a total of 5 amps driving 6 speakers. Pictures of amps to follow and I'll explain how I do it.


  2. #2
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    Here on the top rack are the 2a3 SET mono-blocks that drive the mains ( Beta 12LTA ). On the floor are the Dayton mono-blocks that power the two H-frame bass woofers.


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    The Dayton T-amp ( glaring blue light ) drives the super tweeter with only a 1uf cap on the positive terminal. There are no sound robbing XOer's in the entire system. It's not rocket science that the preamp has two outputs, one which feeds the 2a3 amp and the other feeds the solid state mono-blocks on the floor. But how do I get a signal to the T-amp which drives the tweeters? The Dayton mono-blocks which are daisy chained together each have one input and one output. So I took the second Dayton amp output and pass it to the T-amp. It really works nicely and it's great to be able to control the super tweeter with it's own amp. Best of all my SET now sees an 8 ohm load rather than 4 ohms. The only downside is the maze of wiring to pull this off.


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    Shostakovich fan Feanor's Avatar
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    Quote Originally Posted by Poultrygeist View Post
    The Dayton T-amp ( glaring blue light ) drives the super tweeter with only a 1uf cap on the positive terminal. There are no sound robbing XOer's in the entire system. It's not rocket science that the preamp has two outputs, one which feeds the 2a3 amp and the other feeds the solid state mono-blocks on the floor. But how do I get a signal to the T-amp which drives the tweeters? The Dayton mono-blocks which are daisy chained together each have one input and one output. So I took the second Dayton amp output and pass it to the T-amp. It really works nicely and it's great to be able to control the super tweeter with it's own amp. Best of all my SET now sees an 8 ohm load rather than 4 ohms. The only downside is the maze of wiring to pull this off.

    Well done, PG. I'm glad it's working to your satisfaction.

    Come come you're using a T-amp for the super tweeters instead of more tubes?

  5. #5
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    The T-amp works well, makes no heat and takes up so little space.

    If I couldn't have triodes I'd have T-amps.

  6. #6
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Mash View Post
    Wasn't the Dahlquist DQ10 somewhat similar to this approach?
    Not really. It was a five way monopole rather than a hybrid dipole. The upper drivers were mounted on small baffles independent of the acoustic suspension (Advent) woofer, but were sealed.

    Some pics

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    Wasn't the Dahlquist DQ10 somewhat similar to this approach?

    The Dahlquist died & went away but I forget why.

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    I received an email today from Doc the owner of Bottlehead. He's selling his fully shunt regulated 45 amp mono-blocks. This dream SET with great iron makes 1.75 watts and was only used to drive a pair of tweeters.

    Imagine driving a pair of tweeters with a amp that he's selling cheap for two grand. I think it would put my tweeter driving t-amp to shame.

  9. #9
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    Could a person go from the signal source to a DAC to
    AV splitter to ampsdirect to speakers and eliminate the crossover?
    Just trying to understand how you eliminated the crossover.

  10. #10
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    You can use a pair of one-into-two RCA Y cables and split the analog output signal from a DAC, CD player or other source and feed it to two different amps. There is no loss of signal strength using Y cables. There is no crossover needed at this point as it's still up stream of the amp and speakers. The speakers in this case would have built-in passive crossovers unless they were full rangers.

    With my 3 way set up there is no XO on the main drivers as they are full range. They run directly off the tube amp. The bass woofers which need to be low passed ( receive just the lower frequencies ) are powered by Dayton amp(s) with a built in XO control ( active ) as you would find on a powered sub. The tweeters use a single cap which filters out unwanted frequencies and are driven straight from the T-amp.

    The link below gives information on an electronic/active crossover which in this case is accomplished at the preamp level.

    electronic crossover, PLLXO, passive crossover, active crossover, custom amplifier

  11. #11
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    With the current price of Tang Band W8-1808 would you make that purchase again? You seemed to be very taken by them. I wonder if I shouldn't grab a pair in case the price continues to rise. I am thinking I could incorporate them into the Betsy's and build/experiment around them.

    Interesting I was looking at a pair of no baffle speakers you built. Decades ago when I was in high school one of my buddies worked in an auto salvage yard. He took a set of speakers and suspended them in a frame with springs from each corner and powered them with a salvaged car stereo. He used these in his house for a few years and they sounded great. We always commented on the sound. Perhaps he was ahead of his time.

  12. #12
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    I think the current price for the TB's is $200 each which I consider steep. If you could get a pair for $300 I'd say go for it as that's what I paid a few years ago. The Betas are a better buy at $79 each and you'll need tweeters but they cost very little. The TBs are fantastic drivers in OB but I can say the same for the Betas. The TB's don't really need a super tweeter and they would work great as the main driver in flat baffle like my Betsy's.

    The reason those car speakers sounded good is because they are full rangers and don't need much of a baffle. Lots of homebrew OB's use car speakers.

  13. #13
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    I have been reading ferociously. For simplicity of build, cost, and my live room it seems the road keeps coming back to something similar to, if not your system. I have looked at the more complicated horn builds but I am not sold on that idea as the OB with full rangers seem to be a better match for the hard surfaces of my listening room and lower volume listening. I also like the simplicity of your crossover or lack of crossover network. I can tell you did your homework.

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    Are you talking about the 12 inch Betas?
    I was also looking at the Dayton Audio DCS450-4 18" for H frame woofers.

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    Yes, the Beta 12LTA ( 12 inch ) are my favorite for the time being. With OB, room acoustics are much less important that with conventional speakers.

    The Dayton 18 inch sub would not be a good choice for OB as it's Qts rating of .47 is more suitable for a conventional enclosure. A stiff cone woofer ( low Qts ) is not loose enough to move much air in open space. I would recommend the full range Eminence Alpha 15 which seems to be the favorite bass woofer for H-frames. It's Qts is well above 1.00.

  16. #16
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    Two thoughts on your OB's, Pg....

    1. A curved & shaped structure to move the cone forward of the baffle plane so as to discourage early reflections.

    2. Work up a feedback control system to clean up the sound from the cones. [Tweeters usually do not need this since their moving mass is small w/r/t the "motor's" power.] Visit Mackie.com and look up the diagram for the HR824Mk2, which has an elegantly simple feedback control system. The resistor in the cone's ground circuit only has to be large enough to generate a preamp-level voltage.

  17. #17
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    I take no credit for this MJ King design. I only build what others have had success with. I don't have the software or knowledge base yet to simulate what baffles/enclosures work best with a given driver. The link below has been a great resource for me. MJK has done some amazing work with a host of different designs.



    http://www.quarter-wave.com/Project08/Jordan.pdf

  18. #18
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    Quote Originally Posted by Poultrygeist View Post
    The main driver ( Beta 12LTA ) is powered by 2a3 SET mono-blocks. The Alpha 15 inch H-frame woofers are powered by solid state Dayton APA150 mono-blocks. The super tweeters are powered by a Dayton DTA100 tripath amp. That's a total of 5 amps driving 6 speakers. Pictures of amps to follow and I'll explain how I do it.

    Beautiful work!
    I have never had the opportunity to listen to any open baffle speakers but the concept is intriquing.
    NAD D3020
    Denon 2910
    Denon DMD 1000
    MSB Link DAC III
    Von Schweikert VR2
    NAD 7240PE
    NAD 5240
    Hughes AK 100
    Tascam 122
    Technics SL 1700
    Rogers BBC Monitors LS3/6

  19. #19
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    Thanks kid,

    These have been real game changers for me. If you like the openness of Magnepans you'd love OB.

  20. #20
    I put the Gee in Gear.... thekid's Avatar
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    Quote Originally Posted by Poultrygeist View Post
    Thanks kid,

    These have been real game changers for me. If you like the openness of Magnepans you'd love OB.
    Yes. I see the similarity in the concepts.
    A local gentlemen I sold some gear to is very big on OB's and has apparently built a few himself.
    I suppose I have enough "spare" drivers laying around that I could give it a shot at some point but my guess is that drivers designed for a traditional cabinet speaker is what you need/use for OB's.
    NAD D3020
    Denon 2910
    Denon DMD 1000
    MSB Link DAC III
    Von Schweikert VR2
    NAD 7240PE
    NAD 5240
    Hughes AK 100
    Tascam 122
    Technics SL 1700
    Rogers BBC Monitors LS3/6

  21. #21
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    Full range drivers are a must for OB. Conventional drivers just don't work well.

    As you well know dipole bass can be weak so in order to get good bass an efficient woofer with a high Qts ( like the Eminence Alpha 15 ) is necessary for OB.

    A stiff cone woofer ( low Qts ) works great in a sealed enclosure but won't move enough air in open space. Hence a looser cone ( high Qts above 1.0 ) is needed. The 15 inch Alpha is a high efficiency ( 97 db ) full range bass woofer with a Qts of 1.26.

    Folks on this forum think nothing of spending $300 on high end cables while for the same money they could build these puppies which more than likely would put their own system to shame.

  22. #22
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    Quote Originally Posted by Poultrygeist View Post
    Yes, the Beta 12LTA ( 12 inch ) are my favorite for the time being. With OB, room acoustics are much less important that with conventional speakers.

    The Dayton 18 inch sub would not be a good choice for OB as it's Qts rating of .47 is more suitable for a conventional enclosure. A stiff cone woofer ( low Qts ) is not loose enough to move much air in open space. I would recommend the full range Eminence Alpha 15 which seems to be the favorite bass woofer for H-frames. It's Qts is well above 1.00.
    Thanks, that helps.
    I think I will start heading this way. It may take a while so I can spread the bill out a bit.

  23. #23
    Shostakovich fan Feanor's Avatar
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    Quote Originally Posted by Poultrygeist View Post
    Full range drivers are a must for OB. Conventional drivers just don't work well. ...
    Fanciers of the Linkwitz Orion would beg to disagee with the full range part; (HERE) ...



    ... Or those of the Legacy Whisper, (HERE) ...


  24. #24
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Feanor View Post
    Fanciers of the Linkwitz Orion would beg to disagee with the full range part.
    As would Carl Marchisotto of Dahlquist and Nola.

    After many an hour of listening to his Grand Reference using equally commensurate gear, I would too.

  25. #25
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    Linkwitz "must" use complex crossovers which is thankfully avoided with multi-amped full range drivers in OB. With no crossover you get to hear all of what's normally burned off as heat.

    E-Stat, those monoliths of excess, the Grand Reference, I'm sure sound fantastic with your gorilla amps but I see nothing relative to crossover-less full range drivers in OB. Apples and cumquats?

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