Zaph's Latest!

[sdclc126]

Here it is:

http://www.zaphaudio.com/BAMTM.html

THIS is the one I'm going to build - I've been hoping for a design with this driver combination for some time and now it's been done, and by the man himself. Even has options for integrated subs, my favorite.

Kudos John! Will he ever stop? I sure hope not.

[Zaph]

Hello,

Thanks for the comments. I've been busy with work a lot lately, so it's probably a good thing I got this project posted when I did. I don't have much extra time available for projects these days. I'll participate in this thread for a little while if anyone would like to discuss this project.

I just fleshed out the options a bit more. I've got a cad drawing showing the version with integrated 10" Dayton RS subs which I hope to post sooner or later with some usage details.

[sdclc126]

Hi John,

I do have a few questions:

1) How was the crossover point selected? Was it to completely
avoid the break-up areas of the Dayton? Or...?

2) Would there be any special considerations if using one woofer as opposed to two? My listening room is currently my 12x10 bedroom and I was planning on a single woof, similar to the SEAS L18 design (sealed), with small stereo subs (see #4).

3) Would the Dayton RS150/180 be a workable woofer in this design, i.e., would the crossover require much modification?

4) Since I have a small-ish listening room, and will even when I move to an apartment (where the system will be in the living room but I will of course have neighbors to consider), I really can't see having sub drivers over 8 inches, so I'm wondering what might integrate well with the design - Peerless SLS? Or perhaps the Dayton SD215-88?

Thanks much.

[Zaph]

Originally posted by sdclc126

1) How was the crossover point selected? Was it to completely
avoid the break-up areas of the Dayton? Or...?

2) Would there be any special considerations if using one woofer as opposed to two? My listening room is currently my 12x10 bedroom and I was planning on a single woof, similar to the SEAS L18 design (sealed), with small stereo subs (see #4).

3) Would the Dayton RS150/180 be a workable woofer in this design, i.e., would the crossover require much modification?

4) Since I have a small-ish listening room, and will even when I move to an apartment (where the system will be in the living room but I will of course have neighbors to consider), I really can't see having sub drivers over 8 inches, so I'm wondering what might integrate well with the design - Peerless SLS? Or perhaps the Dayton SD215-88?

1) The primary goal was to clear the peak in the 3rd order harmonic distortion which would mean a crossover just under 2kHz. But, thanks to the capabilities of the Seas tweeter, I crossed over just under the 5th order harmonic, enough to decrease it's audibility a bit. I really pushed the tweeter to find out how low I could go. I actually crossed over at 1Khz which didn't work well. Not only did it distort audibly at medium levels, but the filter Q had to be very sharp to bring up the rolled off response. 1450 had no issues at high levels. I hope I didn't sacrifice any of my hearing during that experiment.

2) The driver combination could work ok with one DA175 and one 27TBFCG, but the crossover would have to be redesigned. Not only because of the lower needed tweeter level and single woofer impedance, but also because the tweeter would have a different response at the top of an enclosure rather than in the middle of an MTM.

3) Yup, total redesign. The RS series have a very peaky breakup. The DA175 has only mild breakup peaking, and it gets away with only two components and no notch filter. I think there's other designs out there with the RS180 and a Seas. Jon Marsh's Modula maybe?

4) Anything that fits in the lower comparment is fair game. There are many 8's that work well in 1 cu ft. But if you can fit the 10's in the budget, this layout may work for you. I do recommend external amplification in this usage.

[sdclc126]

Thanks for all the info. I'll stick with the design as-is (love the simple crossover), and as I already have a pair of Mach 5 10" subs I might as well use them - I'll just have to keep the gain down low for the sake of the neighbors. One of these days I've GOT to move out to the country.

I do have one other question - it's only indirectly related to this design, but have you ever considered open baffle/dipole? I am intrigued by the concept and have wondered how to do a "budget" version of something like the Linkwitz Orion. The reason this is somewhat relevant to the BAMTM is that it occurred to me that its driver compliment might make a workable OB top end (with appropriate crossover and equalization), and coupled to a dipole bass unit.

As I said this question may be a little off topic, but if you have any thoughts I'd be very interested in hearing them. OB/dipoles are tricky and complex (read expensive), especially with active x-over & amplification, and I don't recall reading anywhere if you've ever delved into that area.

Thanks again for the BAMTM - it is exactly what I've been looking for.
Hopefully I'll have a build to show off here early next year.

[widman]

John,

I too am interested in building a BAMTM, specifically the vented floorstander. Your drawing shows damping material in the upper 36" of the enclosure. Is this supposed to be whispermat/sonic barrier as you've used in some of your other designs? Also, where you show extra damping at the bottom, do you mean insulation only on the base or stuffing the last 8"?

Thanks for sharing your designs.
pete

[dawaro]

Is there any chance of a modified version for use as a center channel?

[MuaDibb]

So......John, would you have a suggestion for the woofer/sub for the bottom? Something that would compliment the drivers up top?

[JasonB]

Originally posted by sdclc126
Thanks for all the info. I'll stick with the design as-is (love the simple crossover), and as I already have a pair of Mach 5 10" subs I might as well use them - I'll just have to keep the gain down low for the sake of the neighbors.

Curious to hear your impressions of the Mach 5 Audio 10's. I currently have one in a one cubic foot box tuned to 24hz paired up with another one of Zaph's designs (L18/27TBFCG), so far I am very pleased with it.

Jason

[sdclc126]

Dawaro - Post #7 - Not speaking for Zaph here, but IMO there would need to be no mods for a center channel, save for adding bucking magnets to the drivers if you have a CRT TV set. All you'd need to do is build three and tip one on its side for the center Unless it takes up too much space then maybe you could use the smaller 5.25" Dayton woofs, in which case a crossover mod might be necessary.

MuaDibb - Post #8 - Here's what Zaph says in his text for the BAMTM:

"Integrated sub- A floorstanding tower with the top 1 cu ft section sealed off can give you at least a cubic foot below to work with for other uses, primarily dual integrated subs. If the MTM+sub route is taken with 1 cu ft on the bottom, look no further than the Dayton RSS265HF in sealed or the RSS265HO vented and tuned to about 25-27Hz. Side mounted would work fine with 150Hz or lower active crossover. Needs a couple hundred watts each, not too expensive if you stick to prosound amps. I'd stick to external amps and avoid plate amps for this usage. These Dayton RS subs represent extremely high performance and great value. I use them myself and highly recommend them. For other options, simply look for something that will work in this enclosure size."

JasonB - Post #9 - Though I have no measuring equipment I can only say the Mach 5s seem to be very strong and capable subs, delivering deep yet clear low end on a par with the Peerless XLSs, drivers they were apparently designed to directly compete with. They are certainly competitively priced, except for the shipping cost from Canada (I purchased mine second hand here in the states). I suspect the Peerless have better motors and thus lower measured distortion, but audible? Don't know - personally for sealed subs without room correction my experience is there are more similarities than differences, but that's just me.