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[Martin Boutte]

Internet searches have failed to find this driver and I wonder if anyone knows where it can be found beyond the Data-Bass website, where it was examined.

I like the xmax rating compared to my RCF LF21N451. This driver would make a nice sealed critical Q sub and go straight into my current 3.5 cu. ft enclosure. About +3 dB @ 20Hz would be a nice bonus as well.

I would also welcome suggestions for other 21" drivers with >15mm xmax. I have already checked out Beyma, 18sounds, B&C and RCF itself. Low qts is desired, preferably .25 and below. The higher the Fs, the better, since it will be operated below the Fb by design (60 Hz crossover). I have been beating the bushes but maybe the pro sound community knows some stones I've left unturned.

[Ivan Beaver]

You MUST use your full real name on these forums or the thread will be locked.

[John Halliburton]

The higher the Fs, the better, since it will be operated below the Fb by design (60 Hz crossover).

You need to clarify this, it makes no sense.

John

[Martin Boutte]

You need to clarify this, it makes no sense.

John

I bit of hyperbole. I only meant that an Fs that pushes the Fb above the crossover point (60Hz) is preferred, ala Bag End ELF type systems. An Fb above the XO means a more predictable response below it. A Qtc. of .5 means the Fs will double and produce a 9 - 10 dB/octave roll off in the process. I only really care about the displacement-limited region and the area from 45 - 60Hz.

The best 21" drivers have enough Sd*Xmax to produce good low frequency extension in smaller rooms such as mine (1200 cu.ft.). The RCF delivers 105 dB @ 10Hz. A 2x21" dual-opposed with low Qts drivers can keep the footprint small (5-5.5 cu.ft.) while returning a substantial amount of output, even though the most efficient part of the high Fs- high BL bandwidth will of course be truncated. That region is not what I'm after however. That said, 15 mm of Xmax is not something to shout about but pro sound 21" offers the option I prefer right now. The ZOD 621D has 21mm but it is rare. If a HT driver comes along with the right metrics, I will be all over it.

I know all about the wide-swinging HT drivers like the UXL-18, FTW-21, LMS 5400 and HS-24, but there are reasons I don't prefer any of them. Even the Pro 5100 has some drawbacks and I prefer to stay with the Sd of 21" drivers anyway.

[John Halliburton]

I bit of hyperbole. I only meant that an Fs that pushes the Fb above the crossover point (60Hz) is preferred, ala Bag End ELF type systems. An Fb above the XO means a more predictable response below it. A Qtc. of .5 means the Fs will double and produce a 9 - 10 dB/octave roll off in the process. I only really care about the displacement-limited region and the area from 45 - 60Hz.

The best 21" drivers have enough Sd*Xmax to produce good low frequency extension in smaller rooms such as mine (1200 cu.ft.). The RCF delivers 105 dB @ 10Hz. A 2x21" dual-opposed with low Qts drivers can keep the footprint small (5-5.5 cu.ft.) while returning a substantial amount of output, even though the most efficient part of the high Fs- high BL bandwidth will of course be truncated. That region is not what I'm after however. That said, 15 mm of Xmax is not something to shout about but pro sound 21" offers the option I prefer right now. The ZOD 621D has 21mm but it is rare. If a HT driver comes along with the right metrics, I will be all over it.

I know all about the wide-swinging HT drivers like the UXL-18, FTW-21, LMS 5400 and HS-24, but there are reasons I don't prefer any of them. Even the Pro 5100 has some drawbacks and I prefer to stay with the Sd of 21" drivers anyway.

Part of the issue looking at pro sound 21" drivers is that we typically don't design them into undersized sealed cabinets and operate them in rooms small enough where cabin/room gain is a realistic part of the final equation, quite the opposite actually.

I know of no 21" drivers in the pro audio category with Xmax above 12-13mm.

Best regards,

John

[Lee Buckalew]

Part of the issue looking at pro sound 21" drivers is that we typically don't design them into undersized sealed cabinets and operate them in rooms small enough where cabin/room gain is a realistic part of the final equation, quite the opposite actually.

I know of no 21" drivers in the pro audio category with Xmax above 12-13mm.

Best regards,

John

B&C 21IPAL, 22mm xmax.  Unfortunately, OEM only.

Lee

[Art Welter]

I know of no 21" drivers in the pro audio category with Xmax above 12-13mm.

John,

The B&C21SW152 has an Xmax of 15mm, Xvar of 16mm.
The B&C21SW115 has an Xmax of 14mm, Xvar of 16mm.

I have found the Xvar rating to be very usable for B&C drivers.

[John Halliburton]

John,

The B&C21SW152 has an Xmax of 15mm, Xvar of 16mm.
The B&C21SW115 has an Xmax of 14mm, Xvar of 16mm.

I have found the Xvar rating to be very usable for B&C drivers.

Sorry, forgot about these.  Still, the OP is hoping to find uber 21" drivers with upwards of 20mm Xmax, similar to some of the 18" super drivers. 

Best regards,

John

[Martin Boutte]

Sorry, forgot about these.  Still, the OP is hoping to find uber 21" drivers with upwards of 20mm Xmax, similar to some of the 18" super drivers. 

Best regards,

John

In all fairness John, the uber 18" drivers have upwards of 34-38mm xmax. 20 mm would elicit yawns in the DIY home theater community. Everything is about Xmax and not much else. Not really looking for something so high, unless it has an LMS type motor on it. Hard to keep linearities in check with such swing. Inductance, power compression as well (with smaller coils). However, about 20-22 mm would be a nice compromise for a high BL hybrid 21" that could be used for pro sound and home theater applications. That is a niche that continues to go unfilled, not that many will champion such an approach. I guess that is why the niche goes unfilled eh?

The FTW-21 from Mach 5 would be a rather rambunctious choice with 34mm, but it just requires too large a box for my taste and Le is strangely absent from the T/S parameters, among other things I dislike about it.

[Martin Boutte]

John,

The B&C21SW152 has an Xmax of 15mm, Xvar of 16mm.
The B&C21SW115 has an Xmax of 14mm, Xvar of 16mm.

I have found the Xvar rating to be very usable for B&C drivers.

Funny thing about the 21SW is that the 152 has less geometric xmax than the 115 but the Xmax is lower and the Xvar is the same for the latter? Would that be noted as an improvement? This is rhetorical of course. Just find it strange and unnerving as well.

Xvar is 50% loss in BL or suspension compliance from small signal, so how well it should be regarded is questionable. I do think that B&C has a stupendous driver in the 152 but of course I want a little more swing to that thing! It showed well in testing according to the Data-Bass files, especially in a dual sealed configuration, which really changed my opinion on the strengths of 21" drivers. There is hardly a day when multiple pages of that website are not open on my desktop. Good stuff!

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