Oops! After a year of having my driver lying around I finally put the Thiele-Smalls from the manufacturer through a Qtc calculator. If I trust the manufacturers figures I get a Qtc of over 1.6 for the sealed enclosure they recommend (by building a 150 cu ft box I can approach a Qtc of 1)! Is there anything I can do except throw the driver away and start again?
If I remember right (I don't have speaker design manual available at the moment), adding mass to cone will decrease size of ideal box (Qtc 0,7).
There is available some matematic formulas which help to decide how much mass you have to add.
Of course mass adding will also decrease sensitivy and resonance frequency.
I can check these statement later tonight when I am at home.
Do you have drivers model number available?
Please correct if I am wrong.
There is available some matematic formulas which help to decide how much mass you have to add.
Of course mass adding will also decrease sensitivy and resonance frequency.
I can check these statement later tonight when I am at home.
Do you have drivers model number available?
Please correct if I am wrong.
Kenwood KFC-W3085. I'm a little confused as the speaker will only be used under Fc. If I increase the box size a little from what the manufacturer recommends I can get an Fc which lies just a little over where I want to cross over ( see project ESP 48 )
I don't know how important Q will be in this case?
For the record here are the relevant mfg's figures (I'm increasingly feeling I'll have to double check these with my own measurements):
Qts = 1.0 !!!
Qes= 1.11 !!!
Qms= 10.88
Vas = 71.1 l (2.508 Ft.3)
Fs = 37 Hz
Another limiting factor: Xmax = 9 mm
I'm not looking to lift the sitting room into orbit here, but sensitivity is a factor as the driver is rated at 175 W nom (700 W peak) The amplifier should have ample power (a modded Quad 405-2 with doubled output transistors in bridged mode - should be good for about 800W into 4 Ohms).
I don't know how important Q will be in this case?
For the record here are the relevant mfg's figures (I'm increasingly feeling I'll have to double check these with my own measurements):
Qts = 1.0 !!!
Qes= 1.11 !!!
Qms= 10.88
Vas = 71.1 l (2.508 Ft.3)
Fs = 37 Hz
Another limiting factor: Xmax = 9 mm
I'm not looking to lift the sitting room into orbit here, but sensitivity is a factor as the driver is rated at 175 W nom (700 W peak) The amplifier should have ample power (a modded Quad 405-2 with doubled output transistors in bridged mode - should be good for about 800W into 4 Ohms).
Low frequency extension techniques are usually used with smallish Qts, huge X-max and RMS rating drivers in a relatively small box and when you have lots of amplifier power to burn.
Seems like that your woofer with its x-max and RMS power limit is not the best candidate for this application even if you have enough silicon power. If box size is not a limiting factor I would suggest digging more info on TL boxes or even horn designs.
Seems like that your woofer with its x-max and RMS power limit is not the best candidate for this application even if you have enough silicon power. If box size is not a limiting factor I would suggest digging more info on TL boxes or even horn designs.
box size
Unfortunately SAF (or WAF) is a big factor here. Having a sub in the room at-all is stretching this. I'm stuck with a limit of around 60 litres.
EDIT: I know Xmax won't improve, but won't increasing cone mass improve my SPL at low frequencies?
Unfortunately SAF (or WAF) is a big factor here. Having a sub in the room at-all is stretching this. I'm stuck with a limit of around 60 litres.
EDIT: I know Xmax won't improve, but won't increasing cone mass improve my SPL at low frequencies?
You can get some bass extension at 60L (don't expect high volme output at 20Hz!), but you can't with that driver. The high Qts means you have a weak motor- don't even think about adding mass, that will increase an already too high Qts, drop efficiency, and reduce power handling ability. Low Xmax (that 9mm is probably peak to peak) means you can't salvage it for open-baffle use, either.
The bad news is you'll need another driver to do what you want. The good news is that there are lots of good drivers out there at reasonable cost. At your volume restriction, aim for a 35-40Hz cutoff (that's lower-sounding than it looks on paper), use the room corners to get the output up, and start combing through the Madisound offerings for 10" drivers with suitable T-S specs.
The bad news is you'll need another driver to do what you want. The good news is that there are lots of good drivers out there at reasonable cost. At your volume restriction, aim for a 35-40Hz cutoff (that's lower-sounding than it looks on paper), use the room corners to get the output up, and start combing through the Madisound offerings for 10" drivers with suitable T-S specs.
But adding mass won't help Qts, you'll still need a large box. More important that high of a Qts may indicate a simply poor driver. Take SY's advise, toss that driver.
That driver isn't meant for closed boxes. You want something with a Qts in the 0.4-0.5 range, with a suitably low Fs and Vas. You might even consider an assisted alignment. In any case, a few minutes perusing the tables in Dickason's LDC will prove useful.
One SEAS driver that will work well is this:
http://www.seas.no/seas_line/woofers/H512.PDF
when mounted in one of my Tuba 18 or AutoTuba sub enclosures.
From what I understand it's reasonably priced in your area. Very low Qts drivers will give good bass but have to be horn loaded to do so.
http://www.seas.no/seas_line/woofers/H512.PDF
when mounted in one of my Tuba 18 or AutoTuba sub enclosures.
From what I understand it's reasonably priced in your area. Very low Qts drivers will give good bass but have to be horn loaded to do so.
Seas is relatively resonably priced, yes. Looking at the data sheet for the P21 RFX I'm still getting very low Qtc calculations.
However. It has got me thinking about the possibility of using two 8" units. instead of one 10 or 12.
Will keep looking.
However. It has got me thinking about the possibility of using two 8" units. instead of one 10 or 12.
Will keep looking.
what about this?
seas L22 RNX/P. qtc around 0.7 with a 34 litre cabinet. I could get two of them in one of my old front pair boxes and still have enough room for an amp in its own sealed container.
seas L22 RNX/P. qtc around 0.7 with a 34 litre cabinet. I could get two of them in one of my old front pair boxes and still have enough room for an amp in its own sealed container.
even better!
Peerless SLS 263 : Qts = 0.52 , Vas 87.7 l (3.09 ft3) Fs 27.8
or
Peerless SLS 213 :
Qts 0.51 , VAS 37.9 l (1.34ft3), Fs 34.4 Hz
Can't see from this what Xmax and power handling are like.
Peerless SLS 263 : Qts = 0.52 , Vas 87.7 l (3.09 ft3) Fs 27.8
or
Peerless SLS 213 :
Qts 0.51 , VAS 37.9 l (1.34ft3), Fs 34.4 Hz
Can't see from this what Xmax and power handling are like.
Sorry people
I'd like to thank you all for your time and patience. Having looked at available drivers and done the calcs I find that anything that will work in a box as small as I need for SAF is just going to cost way too much (we're talking small here, and if it doesn't go down to around 20 then it's just not worth the effort as my mains are deep enough for most music).
I'll keep looking and will probably wile away the time by building the electronics, but the sub itself will have to wait.
Cheers!
I'd like to thank you all for your time and patience. Having looked at available drivers and done the calcs I find that anything that will work in a box as small as I need for SAF is just going to cost way too much (we're talking small here, and if it doesn't go down to around 20 then it's just not worth the effort as my mains are deep enough for most music).
I'll keep looking and will probably wile away the time by building the electronics, but the sub itself will have to wait.
Cheers!
A few automotive products only. I have been wondering about 4 Ohm units, partly in case I can ever affort 2 in series, and partly because the Inductance at low frequencies is usually much higher than nom. impedance. With the dollar as it is I might consider direct import 🙂
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