18" woofers - which have high Qts (+low Fs)

[elac310]

Originally Posted by jim ski

Check out the BMS 18N862 very serious driver. You can most likely get away with using one driver for the build instead of four..

Overview

Nice model indeed. Fs 25hz, xmax 19mm but Qts 0,34. I think I would prefer a bit of a higher value as regards the latter; I'd like to get away without Eq', if possible, although I confess I have no clue how the woofers would behave in my intended project.

Chris.

[elac310]

This other Goldwood (also available from Parts Express) looks in fact even better to me:

Goldwood GW-18090 18" Select Series PA Woofer
Specifications: • Power handling: 500 watts RMS/1,000 watts max • VCdia: 4" • Le: 2.8 mH • Impedance: 8 ohms • Re: 7.2 ohms • Frequency range: 20-1,500 Hz • Fs: 29.2 Hz • SPL: 95.2 dB 2.83V/1m • Vas: 13.66 cu. ft. • Xmax: 5.4 mm • Qms: 13.86 • Qes: 0.49 • Qts: 0.48 • Dimensions: Overall diameter: 18-1/4", Cutout diameter: 16-3/4", Depth: 7-1/2".

Would have been a serious contender with a bit more Xmax.

Chris.

[bjorno]

Hi,

FYI, A couple of simulations you might be interested to study.

b

[KSTR]

With the monster amp that you are using, I wouldn't even care about "too high" Fs and "too low" Qts, just simply EQ the driver. The SR1 has plenty of voltage headroom (current as well), which is the only thing required to use low Qts drivers.

It's not an 18", but I would think that the Ciare NDH15-4S (if you can get it, since it is in the OEM product category) will be a most excellent OB driver, and exactly for it's extremely strong motor (Qts=0.25, BL²/Re=100), moderate moving mass and moderate stiff suspension (thus rather low Fs), Xmax also quite good, and a very low distortion design. Also it looks well ventilated which might cause only little air noise, an important aspect (I haven't checked the driver in person yet but hope to do soon).

Aside from that Ciare woofer (where you'd need several of) that BMS ultra long excursion model is tempting, but here again the air noise issue will have to be checked with special care. The designers for sure did not have dipole operation in mind when engineering the forced-air cooling system.
In doubt I'd rather go with more drivers (of modern construction but not overpowered, though) and less excursion for each to be safe here.

Generally, the lower the Qes the more control has the motor over the driver, especially over the suspension nonlinearities. It will need EQ but against common belief this will NOT result in an efficiency penalty (that is, there is a slight one in for the amplifier if it is not Class-D).

[elac310]

Thanks for all your good advice.

I have now launched an order for the size above 18" (i.e 21") from Pyle Audio.

The manufacturer parameters suggested a low Fs and a Qts hich is not what I wanted originally (see datasheet at PylePro - PDW21250 - 21'' Performance Optimized High Power Subwoofer).

Parts Express staff have, however, measured a Qts at 0,66; see one of the last posts on Pyle Pro PDW21250 21" High Power Subwoofer Customer Questions and Answers ; their own measurements seem to confirm an Fs below 30 Hz (so I anticipate an ever lower value after proper break in).

It is true that since I will use active crossover, probably including Eq possibilities (see for intance www.reckhorn.com - Active x Over) I'd have some flexibility even if the woofer parameters are not as expected. + I have a couple of extra Crown SR 1 left, which I had aquired just in case I would go some day for a sub or two.

Besides, this Pyle is given for an xmax of 9mm.

and I got a good price from a UK-dealer on the Bay.

Chris.

[ashok]

I have just bought a pair of Eminence Kilomax Pro18A's. You will find that the specs differ between the 2006 catalog and the 2012 catalog .
The 2006 catalog gives Fs = 33Hz and Qts= 0.56
The new catalog says Fs= 32Hz and Qts = 0.47

My new units have a Fs of about 39 Hz in free air and Qts = 0.67
On an OB panel about 20 x 24 inches the Fs is about 37 Hz and Qts = 0.85 !
Both will probably drop after use but I'm not sure by how much. I guess by about 5 to 10 % ?

[OMNIFEX]

Originally Posted by ashok

I have just bought a pair of Eminence Kilomax Pro18A's. You will find that the specs differ between the 2006 catalog and the 2012 catalog .
The 2006 catalog gives Fs = 33Hz and Qts= 0.56
The new catalog says Fs= 32Hz and Qts = 0.47

It is a pity Eminence did not call the new version series B. One could imagine what would occur if buying large quantities of this driver and assumming all the drivers will have the same TS Parameters.

[ashok]

Yes I think so too. They should have changed the model number to reflect the change in specs . Or was there a typo ? You will also see that Xmax was wrongly shown as 1mm in the 2012 catalog ! It is 10 mm .

I was wondering if the Qts of a new driver could be as high as 0.67 when specd at 0.56 ( or 0.47 !) ? It is good for me in any case as I'm using it in an open baffle ! I need less EQ. Unlike the Alpha 15A the magnet is large and should have much better control over the cone/coil .

Has anyone used the Kilomax Pro18A in an OB ?

[OMNIFEX]

It may be best to contact Eminence on your 0.67 findings. The few times I’ve contacted them, they were very prompt in their reply.

[OMNIFEX]

ashok

Did you ever get a confirmation on Eminence on your findings?

I am thinking about buying 8 Killomax 18s but want to make sure I am not stuck with 18-inch drivers with an fs of 39 Hz.