I have heard this many times, but now i need it, i just can't remember. Now how is it?
Low Qe driver is suitable for a closed cavity
0,7 Qe is suitable for bass reflex and
Higher Qe is suitable for open baffle.
Right ???
Low Qe driver is suitable for a closed cavity
0,7 Qe is suitable for bass reflex and
Higher Qe is suitable for open baffle.
Right ???
Hi Lars,
Dickason said of driver selection in the Loudspeaker Cookbook:
"In terms of driver Qts, closed-box loudspeakers generally require woofers with a fairly high Qts of greater than 0.3..."
(of vented system) "...only Qts between 0.2-0.5 generally provide satisfactory responses."
Not sure if that helps, but there you go.
Dickason said of driver selection in the Loudspeaker Cookbook:
"In terms of driver Qts, closed-box loudspeakers generally require woofers with a fairly high Qts of greater than 0.3..."
(of vented system) "...only Qts between 0.2-0.5 generally provide satisfactory responses."
Not sure if that helps, but there you go.
Qts<0.3 hornloading
0.3<Qts<0.4 basreflex
0.4<Qts<0.55 closed box
Qts>0.55 infinite baffle/dipole
It isn't stricktly like that. Things overlap and depend on other T/S-parameters as well (like Fs). Fs/Qts gives Efficiency Bandwith Product (EBP) which is also used as a rule of thumb.
Qts combined with Xmax gives an good idea what kind of quality (sub)speaker you're dealing with, high Qts , low Xmax being the worse.
Simulating will sometimes show supprising facts, so don't go totally out on rules-of-thumb anyway.
Mvg Johan
0.3<Qts<0.4 basreflex
0.4<Qts<0.55 closed box
Qts>0.55 infinite baffle/dipole
It isn't stricktly like that. Things overlap and depend on other T/S-parameters as well (like Fs). Fs/Qts gives Efficiency Bandwith Product (EBP) which is also used as a rule of thumb.
Qts combined with Xmax gives an good idea what kind of quality (sub)speaker you're dealing with, high Qts , low Xmax being the worse.
Simulating will sometimes show supprising facts, so don't go totally out on rules-of-thumb anyway.
Mvg Johan
Thanks Guys! I did some simulations and it seems if i take a Qts 0.7 and put in a too small closed box, it will peak severely at 100-200 Hz. But if i take a low Qts (0.4) it will only peak 1-2 dB. But the low Qts unit will also give a slightly higher spl than the high Qts unit. Is this in compliance with reality?
The project in question is a flat panel subwoofer with 64 drivers 6 inch each. Each in closed boxes of 4 liters. The size is 2 x 2 meters but only 6 inches in depth. (A wall of bass!!)
The simulator program (Waldo) shows 105,6 dB / 1 Watt (100 Hz up) and -18 dB at 35 Hz. I think the large baffle will give some help on the -18 dB. (???)
So i'm going to compensate the -18 dB (or whatever) with a gainer stage, and some power. The total loadability of the 64 units is 6 kW so with the right amplifier it can be made linear to the 35 Hz, and with 40W per driver a spl of 139 dB should be possible. (Total 2.5 kW). (log(2500) x 10 + 105.6) = 139 dB
The project in question is a flat panel subwoofer with 64 drivers 6 inch each. Each in closed boxes of 4 liters. The size is 2 x 2 meters but only 6 inches in depth. (A wall of bass!!)
The simulator program (Waldo) shows 105,6 dB / 1 Watt (100 Hz up) and -18 dB at 35 Hz. I think the large baffle will give some help on the -18 dB. (???)
So i'm going to compensate the -18 dB (or whatever) with a gainer stage, and some power. The total loadability of the 64 units is 6 kW so with the right amplifier it can be made linear to the 35 Hz, and with 40W per driver a spl of 139 dB should be possible. (Total 2.5 kW). (log(2500) x 10 + 105.6) = 139 dB
Forget about the 139 dB at 35 Hz, your drivers will run out of excursion. But you can get 139 dB at higher frequencies for sure...
Yes, a lower Qts indicates a more efficient speaker. But also the lower the Qts becomes, the less it's suited for low-frequency reproduction.
I don't know what on earth you would need a SPL of 139 dB for, except bassheavy parties starting at 200 people outside or so. So what is the intended use?
Mvg Johan
The purpose is 'discrete' club sound. Since the speaker is only going to be 6 inch thick, it can fit over the dancefloor, and not take up any space in the club.
Lars: You will want to use a subwoofer modeling program in order to see the full picture.
'bassbox6'
'winisd pro'
'subsim'
Cheers!
'bassbox6'
'winisd pro'
'subsim'
Cheers!
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