Yet another Zaph BAMTM -- some questions

Consul · 27th March 2007, 03:39 PM

I'm very interested in Zaph's first variation of his BAMTM design, making a sealed floorstander of two cubic feet in volume. According to my handy Loudspeaker Design Cookbook, this would lower the overall Qtc of the system, which is a desirable trait for me.

One "sanity check" question I have is, does a lower speaker Qtc increase transient response? That seems to be what I'm getting from the LDC.

Also, the LDC gives tables for figuring out Qtc from various volumes and driver Qts numbers, but how does that change when one is using two mid-bass drivers in one volume of space? I'm just trying to figure out what my final Qtc might be.

I'm also thinking the lack of any notching or other EQ in the crossover might make this system ripe for bi-amping with an active crossover. That might wait for a later experiment, though.

Otherwise, this looks like a very good "bang for the buck" system. Thank you all for your help.

Dave Bullet · 29th March 2007, 11:50 PM

I'll try a response.... (at least if I'm wrong you'll get more attention to your post :-)

A sealed Qtc deisgn of 0.5 is supposed to be the best "transient perfect" alignment. This means the cone movement is neither under nor overdamped. My laymans interpretation is that for a given driver in a box giving a Qtc=0.5, the box will neither restrict cone excursion (box too small), nor let it go "floppy" (box too big). The cost is a 1. slightly higher F3 over a Qtc=0.7 design and 2. a bigger box and 3. less power handling

When you double woofers (in a standard dual woofer configuration like the BAMTM) - it's like doubling the Vas. Thererfore you should double the box volume you calculate for a single driver to achieve the same Qtc.

Cheers,
David.

Consul · 30th March 2007, 01:57 AM

Thanks! So as I suspected, the Qtc of this system will basically be the same as one driver in half the volume.

Thomas Barefoot of Barefoot Sound designed his MicroMain 27s with an overall Qtc of .707. It's an amazing design just looking at it, though I haven't had occasion to listen to one. I also couldn't hope to afford them at $6400 a pair.

27th March 2007, 03:39 PM	#1
Consul diyAudio Member Join Date: Nov 2003 Location: Port Huron, Michigan, USA	Yet another Zaph BAMTM -- some questions I'm very interested in Zaph's first variation of his BAMTM design, making a sealed floorstander of two cubic feet in volume. According to my handy Loudspeaker Design Cookbook, this would lower the overall Qtc of the system, which is a desirable trait for me. One "sanity check" question I have is, does a lower speaker Qtc increase transient response? That seems to be what I'm getting from the LDC. Also, the LDC gives tables for figuring out Qtc from various volumes and driver Qts numbers, but how does that change when one is using two mid-bass drivers in one volume of space? I'm just trying to figure out what my final Qtc might be. I'm also thinking the lack of any notching or other EQ in the crossover might make this system ripe for bi-amping with an active crossover. That might wait for a later experiment, though. Otherwise, this looks like a very good "bang for the buck" system. Thank you all for your help.

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29th March 2007, 11:50 PM	#2
Dave Bullet diyAudio Member Join Date: Jan 2002 Location: Wellington, New Zealand	I'll try a response.... (at least if I'm wrong you'll get more attention to your post :-) A sealed Qtc deisgn of 0.5 is supposed to be the best "transient perfect" alignment. This means the cone movement is neither under nor overdamped. My laymans interpretation is that for a given driver in a box giving a Qtc=0.5, the box will neither restrict cone excursion (box too small), nor let it go "floppy" (box too big). The cost is a 1. slightly higher F3 over a Qtc=0.7 design and 2. a bigger box and 3. less power handling When you double woofers (in a standard dual woofer configuration like the BAMTM) - it's like doubling the Vas. Thererfore you should double the box volume you calculate for a single driver to achieve the same Qtc. Cheers, David.

30th March 2007, 01:57 AM	#3
Consul diyAudio Member Join Date: Nov 2003 Location: Port Huron, Michigan, USA	Thanks! So as I suspected, the Qtc of this system will basically be the same as one driver in half the volume. Thomas Barefoot of Barefoot Sound designed his MicroMain 27s with an overall Qtc of .707. It's an amazing design just looking at it, though I haven't had occasion to listen to one. I also couldn't hope to afford them at $6400 a pair.

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