ZBAMTM sealed but w/SEAS 27TDFC instead of the metal tweeter

[Sakura]

[IMG]ARTA measurement of one at .75 meter in my garage[/IMG]

Will post more pics later...

[Sakura]

Here's a pic of one of the speakers

There's some fuzz on it from some wool I sound absorbing sheet I tried gluing around the tweeter, and the bottom woofer is dusty...

And a 2nd pic w/the crossovers and showing the inside before I glued the front on.

[jkrutke]

[IMG]ARTA measurement of one at .75 meter in my garage[/IMG]

Will post more pics later...

Looks good. Did you use the same tweeter filter and resistor level? Your 27TDFC doesn't exhibit quite as much top end rise as some I've tested. (about 8 of them)

[Undefinition]

<shrug>
The rise in the top end looks pretty familiar to me :W

[Sakura]

Looks good. Did you use the same tweeter filter and resistor level? Your 27TDFC doesn't exhibit quite as much top end rise as some I've tested. (about 8 of them)

EDIT: Unfortunately, my mic is not calibrated, I have an ECM-8000, but what I used for those measurements was a DIY Panasonic capsule mic, basically just some wires going from the capsule to my sound card, with the capsule mounted in a the end of a thin brass tube. I don't know yet, but, I suspect that the mic starts rolling off above 15 Khz? I will have to see if someone at my local university can calibrate my mic for me.

Filter is exactly the same, I used a meter to measure the components to make sure it wasn't significantly off.

It seemed to me, that, in the audible range, that the TDFC and the TBFC/G used in your original BAMTM design are similar enough that it shouldn't sound significantly different?

I want to also try the MCM waveguides with the SEAS tweeters and I couldn't afford to buy both the TBFC/G and TDFCs presently, so I settled on a pair of the TDFCs...

After hearing this speaker, I think the 3/4" MTM isn't quite thick/well damped enough to make a good speaker enclosure. HOWEVER, I did not use Whispermat or Black Hole damping material, and that might be enough of an improvement? I did use some roof repair tape, which is quite effective at damping in some applications.

During most of my listening, the sound coming from the enclosure did not have too detrimental of an affect though, it may have contributed to a slight "boxy" sound?

I will say that they sound better than most typical $1,000 - $5,000 commercial speakers.

Other than some issues with dispersion patterns and time alignment, the crossover seems excellent. The frequency response is remarkably flat, and I love the simplicity of the crossover design.

I will try building a larger ported cabinet. This time I will try to build a superior enclosure, perhaps with a multi-layer construction. I have some "roofing felt" - (tarred paper?) which this gentleman: http://www.silcom.com/~aludwig/contents.htm got excellent results with for enclosure damping.

I may have to further his experiment by building two identical cabinets, but, with one I will glue the walls/felt layers together with contact cement, and the other I will not. If I do so that experiment, it will be with small simple one-way driver boxes.

The blue stuff you see next to the cabinets is Dow "Safe Touch" Acoustic and Thermal insulation, which I have used as cabinet stuffing.

One last question, the hump at the low end seems a bit high, does that seem typical for your suggested sealed version of the BAMTM? For the most part, I don't mind the sound. Perhaps I should try a slightly larger cabinet as a third option, in addition to the 2x as large vented cabinet.

I'm not SURE I will build the vented version, I might just build some "bass bins" with these MONSTER 8" woofers I was given recently:

[jkrutke]

[I]One last question, the hump at the low end seems a bit high, does that seem typical for your suggested sealed version of the BAMTM? For the most part, I don't mind the sound. Perhaps I should try a slightly larger cabinet as a third option, in addition to the 2x as large vented cabinet.

That lump is just your average room effect. I bet at 2 meters it moves to a completely different frequency. Likewise, different positioning will change it also. It won't be there for a near field measurement, though the response would show a midbass rolloff from baffle step compensation, along with artifacts from the out of phase signal combining from the other woofer and the tweeter.