My old Fostex FF225WK Mets in their new home.
A friend bought them off me.
His cat approves
why did you sell them?
Hmm, seems low, I was expecting in the ~ 2.4 - 4 ohm range.
Anyway, the greater the total output impedance [Qts'], the lower the driver Qts and tuning to actual Fs is generally desirable to maximize bass output.
Ignoring the room's acoustics, speaker placement, etc., a max flat alignment [lowest corner frequency] is considered a good starting point, so this equates to a box net volume [Vb] = driver compliance [Vas] and box tuning [Fb] = driver resonance [Fs] with a ~0.403 Qts'.
Qts' = Qts + any added series resistance: mh-audio.nl - Home
Find what driver Qts comes closest to a ~0.403 Qts' and err on the high side to make the cab larger just in case. Frankly, with the various TLs I plan for around a 0.5 Qts' to allow some in-room tuning flexibility with internal and/or vent damping.
GM
Anyway, the greater the total output impedance [Qts'], the lower the driver Qts and tuning to actual Fs is generally desirable to maximize bass output.
Ignoring the room's acoustics, speaker placement, etc., a max flat alignment [lowest corner frequency] is considered a good starting point, so this equates to a box net volume [Vb] = driver compliance [Vas] and box tuning [Fb] = driver resonance [Fs] with a ~0.403 Qts'.
Qts' = Qts + any added series resistance: mh-audio.nl - Home
Find what driver Qts comes closest to a ~0.403 Qts' and err on the high side to make the cab larger just in case. Frankly, with the various TLs I plan for around a 0.5 Qts' to allow some in-room tuning flexibility with internal and/or vent damping.
GM
You sure yours meet published specs? Their track record is a bit spotty, with much higher Qts, though don't remember which model
GM
You're welcome!
Yeah, you lose some efficiency, but room/boundary gain can offset this some/all, so I do fine tuning with a cheap 25 ohm pot, then replace it with a fixed resistor grid of small, low tolerance mil spec resistors of the appropriate ohmage, current carrying capacity.
Good luck with the healing, I can't heal enough these days before I tweak, etc., something else.
GM
How do I test my speakers specs? I like the idea of an adjustable pot. Does this go on the positive side off the terminal or in between + & -. And on the healing side I'm with you. If I wait to heal completely nothing will ever get done. I'm slowly getting caught up in the full range rabbit hole. My first OB build is an eye opener compared to my box speakers and I just threw these together.
Attachments
I read this thread some time ago, and been following since. I cannot recall of there is a calculator for this metronome quadratic quarter wave deal, or if it was done with the no longer available Math Cad sheets...
I would like to sim some other drivers, some with the thought of building, others just for giggles.... by this I mean drivers not already on the Metronome table that Dave has thoughtfully maintained...
What's a girl to do?
John
If someone wanted to do all the work, I can provide a list of drivers I'm interested in....
I would be happy to do the skull sweating, and share the results as well.
I would like to sim some other drivers, some with the thought of building, others just for giggles.... by this I mean drivers not already on the Metronome table that Dave has thoughtfully maintained...
What's a girl to do?
John
If someone wanted to do all the work, I can provide a list of drivers I'm interested in....
I would be happy to do the skull sweating, and share the results as well.