What About the New NIRVANAs SUPER-12CF and SUPER-15CF ?

FullRangeMan · « **on:** 25 Apr 2009, 02:51 pm »

Dear Full Range fans:
I have just know on this Forum the Mark Audio Alpair 10 Full Range ( really the best 6'' full range

by the Freq. chart they show on the site) and the Nirvanas Super12CF and Super15CF. The Alpair 10 are really impressive

in all senses, but anyone of you already listen the Super12 or Super15 as OB or BassReflex ?

Do you think the bigger Super15CF (VAS 618 Liters) are a good drive for a OB stereo system ?
Both Super12 and 15 have a hi dB level on the midrange and treble, do you think this is a problem for a OB system ?
Please, say your general opinion about the Nirvanas etc...?
Thankyou for your advices,
Full

Scottmoose · « **Reply #1 on:** 2 May 2009, 05:02 pm »

The ANs tend to come into their own with models that nobody else produces, i.e. the larger units. The smaller 6 1/2in - 8in units are reasonable enough for the price (in the North Americas at any rate -outside, once you factor in import fees, postage, VAT etc., there is little incentive to choose them over their rivals), but personally, I don't regard them as being of the same quality as the Fostex equivalents. Note that the Mark Audio Alpair 10 is a 5 1/4in driver, not a 6 1/2in, so comparisons are tenuous. It's one of the finest FR drivers available IMO however. Closest equivalent is the Jordan JX92S, but the Jordans, since Ted sold up, have had some severe consistancy / manufacturing problems, and they are voiced rather differently to the Alpair 10, and the MA driver is inherently a more advanced unit.

As for the 12in & 15in ANs... in principle, I like big cones. However, even the factory impedance plot is showing cone breakup rippling up through the response; they're large units, and they're not very expensive, ergo, something has to give, right? The official claimed parameters are also known to be 'optimistic', i.e. way off, so ideally, you'd need to measure your own units to see what you've got before designing an enclosure for them. As for the enclosures, they both really do need very large (in modern terms) boxes, even based on the factory data, and with 1mm Xmax, OB use is going to be limited to modest sized spaces & SPLs unless supported with a suitable woofer, if you want distortion to remain within acceptable levels. I suspect the 15in unit, in a trad. style BR box (not the CSA one), of about 17 1/2ft^3, would be entertaining, albeit hardly the last word in refinement or accuracy. ;^)

FullRangeMan · « **Reply #2 on:** 3 May 2009, 04:12 am »

Dear Scottmoose,
Thankyou for your detailed and expert advices, it was very useful and informative.

I was think of two Nirvana Super15CF in a OB I or U shape for no problems with design and making of boxes and a easy tube impedance of 16 ohms (serial connection) and if I do not like the sound I could made a BR box with one 15'' firing front and the second firing top.

I see a picture of the 13.6 box in the CSA site, that show 3 holes in the front baffle with no Tuned Ducts, the inside volume seems around 366 liters.
Do you see any problem with this 13.6 box as see in the CSA site ?
Do you know other fullrange maker with 15'' or 18'' models ?
Thanks hugely, Full

planet10 · « **Reply #3 on:** 3 May 2009, 05:00 am »

I don't know about that box, but a local built one suggested for the 10" which has a 6" hole cut out for a port. After measuring the driver, it took a 10" long 6" D port to get the box tuned more optimally.

dave

Scottmoose · « **Reply #4 on:** 3 May 2009, 10:26 am »

As Dave & I allude to, the CSA boxes are generally best avoided -exactly what (if anything) David Dicks is trying to do with them is a question that as yet, nobody of human kind has yet been able to answer. ;^)

The vents you refer to in the 13.6 will be tuned somewhere, at least from the POV that if you cut a hole in a box then physics dictates that it's going to resonante at a particular frequency, although again, whether this is by accident or design (let alone whether it's optimal) is another matter entirely. As I mentioned, the 12in & 15in drivers have high volume requirements, even using the factory specs. For e.g., the 15in is looking at the thick end of 41ft^3 apiece for a 4th order T/S aligned BR. Very simple, trad. BR math yeilds around 35ft^3 per driver for a 30Hz tuning, or about 17.5ft^3 for around 45Hz (it's not especially precise), assuming vent CSA = Sd. Note this is using the factory data, which is 99.99% sure to be well out, so you can probably add ~50% to the T/S derived Vb requirement.

Twin units forward firing is asking for it, OB or otherwise, unless you roll one off above it's mass corner, or you'll run into lobing problems, causing severe HF attenuation & deep nulls continuing down through the midrange. Not trying to put you off here, just introduce an element of practicality. If you wanted OB, I'd suggest a single unit with a dedicated woofer (in which case, a smaller main driver would probably be more practical), while in sheer size terms, unless you happen to own a chateau with an unused ballroom, a single 15 would be about the limit for a BR.