Not enough bass from Audio Nirvana 10" Classic Driver

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tortugaranger

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #20 on: 9 Apr 2016, 12:59 pm »
My modeler (MacSpeakerz by Jon Murphy) says an 8" long vent. Produces a kinda ugly curve.

I can't see where  the vents for the 2.8 ft^3 cabinet are but the cabinet that a local used for his stamped basic 12s specified a 6" vent x the material thickness (¾"). We installed a MUCH longer vent for a significant improvement.

tortugaranger, can you give us the detail of your cabinet?

dave

My default starting point for this project was to use AN's plain vanilla cabinet design specs for their 2.8 cubic feet (~79 liter) box with a 6 inch port and no port tube, just the ~0.75 wall thickness. It was never my intent to actually use this as the final cabinet, only to use it to guide next steps. The final cabinet design will be a stacked "boat hull" shape using layers of milled baltic birch. Thus the entire cabinet except for the tops and bottoms will be sanded and clear finished baltic birch edge grain. The walls will be ~1.5 inch thick laminate with periodic cross bracing. Stiff, stiffer, stiffest. You won't be hearing this cabinet, just the driver.  :thumb:

I've run several cabinet design calcs which more or less conclude that the ideal cabinet for this driver would be ~ 12 cubic feet with an F3 well under 30 Hz. A monster size box that is too big to be practical for what I'm looking for. Hence the 2.8 cubic feet box which when you see it standing there in front of you still looks plenty big. 40" tall by 12" wide by 13.5" deep.

With a 6 inch port the design calcs call for a port tube length in the 8-12" range. I currently have no port tube other than the 0.73" baffle itself. This morning I experimented with an 8" quick and dirty port tube made of stiff thick walled paper rolled into a tube reinforced with duct tape. Ugly as sin but fairly solid. Did some with and without listening and my conclusion was the port tube was not noticeably effective. Quite possibly a proper tube would lead to a different conclusion. By my hunch is that while a longer tube may provide incremental benefit it would be rather modest at best.

After further playing around with the miniDSP together the Room Eq Wizard ("REW") software (http://www.roomeqwizard.com/), I've arrived at the following adjustments and thoughts.

1) Being a full range driver, the 10" Audio Nirvana Classic benefits greatly from the application of baffle step compensation. Using the DSP, a high shelf PEQ starting at 400 Hz with -6 dB gain really did the trick.

2) Whether it's the driver, the room, or combination of both, there was a noticeable boominess in the mid-bass. After running REW and loading the adjustment filters into the DSP, the boominess was completely gone. The filter was a fairly big notch. Huge plus and a snap to implement with REW and the miniDSP.

3) Overall bass satisfaction benefits from a low shelf PEQ boost starting at 100 Hz with a +2 to +3 dB gain. Adjust to suit. Cranking it up further really pours on the bass.

4) Using REW to try to flatten the upper frequency range (>1k and above) of the 10" AN Classic was not at all satisfying. It seemed to just kill the character of this driver. As soon as I turned off this filtering the sound came alive again. My conclusion is that once you take care of the baffle step compensation mentioned in 1) above, no further tweaking is warranted with this driver. As full range drivers go it's pretty smooth. 4) EDITed  After further work with the DSP, RTA etc. it's quite clear that de-emphasizing the 2.5-5k range by ~2 dB resulted in enormous improvement by smoothing out a somewhat overly bright presentation in this audible range. This wasn't obvious based on the RTA but was most clearly evident while listening to live tracks and switching this filter in/out of the mix.

Edit:  I should add that the room these speakers are in is arguably on the large size. Vaulted ceiling central great room with integral kitchen area. Plus the speakers are at least 3-4 foot out from the wall. In a smaller room with speakers closer to the walls, the need for baffle step compensation might well be far less. However, with full range drivers, a bit of high shelf lowering will likely always be of benefit.

Regards,
Morten
« Last Edit: 11 Apr 2016, 03:08 pm by tortugaranger »

planet10

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #21 on: 9 Apr 2016, 04:44 pm »
Morten,

By the sims (using the factory numbers) 2.8 ft^3 with 18.5mm long vent is real ugly. It is the one with the 4 dB bump. The other curve is with the 8" vent. I cannot imagine using these in a 12ft^3 box. As i posted earlier i figure 35 L for an optimum size box.



dave

PS: The Cast Super 8 is one of the AN drivers on my list to try (and the 3 & the 15), but it has little or no bass capability (by factory spec) so that complicates things by requiring a FAST.

planet10

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #22 on: 9 Apr 2016, 04:52 pm »
The final cabinet design will be a stacked "boat hull" shape using layers of milled baltic birch. Thus the entire cabinet except for the tops and bottoms will be sanded and clear finished baltic birch edge grain. The walls will be ~1.5 inch thick laminate with periodic cross bracing.

I am not a big fan of translam construction but it is useful for making curved cabinets. Braces machined into the slices have questionable  performance. I would suggest separate braces where a brace touches all the layers as much more effective.

dave

planet10

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #23 on: 9 Apr 2016, 04:55 pm »
Quote
However, with full range drivers, a bit of high shelf lowering will likely always be of benefit.

We build mostly FR speakers and rarely do we find BSC useful.

dave

tortugaranger

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #24 on: 11 Apr 2016, 02:39 pm »
Braces machined into the slices have questionable  performance. I would suggest separate braces where a brace touches all the layers as much more effective.

dave

I'm curious if your expressed view is informed by specific structural analysis such as finite element analysis or some other method or is it emperical?  I've had some experience in my early days as an engineer working on complex mechanical structures and I'm hard pressed to understand, at least engineering-intuitively, why integral braces would have questionable efficacy. To be clear, I've not confirmed this one way or the other analytically.

I don't understand what you meant by "where a brace touches all the layers". A slice with integral bracing touches all the layers within that slice directly and indirectly to slices immediately above/below with efficacy dropping off with increasing distance from that slice. Are you suggesting a thicker brace perhaps that touches multiple slices? If so, would not 2 or perhaps 3 slices in a row with bracing accomplish this? Again, not sure what you meant by that phrase.

tortugaranger

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #25 on: 11 Apr 2016, 02:57 pm »
We build mostly FR speakers and rarely do we find BSC useful.

dave


Have done further tweaking with the DSP while switching back and forth between using full spectrum white noise generator and real time analyzer (RTA) and listening to actual tracks. Without a doubt, boosting the bottom end relative to the top end substantially helped improve the performance; whether that's BSC or not, eh, it works. What I discovered over the weekend that also helped immensely is deemphasizing the 2.5-5 kHz range by roughly ~2 dB which smoothed out the somewhat overly bright emphasis normally present here. The need for this was not evident via the RTA but was most definitely a big plus when switching this in/out of the circuit while listening to live tracks. At this point, these have become the best sounding speakers I've heard yet including most anything I've heard at shows. DSP & full range drivers - great fun and very satisfying.  :thumb:

planet10

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #26 on: 11 Apr 2016, 06:11 pm »
I'm curious if your expressed view is informed by specific structural analysis such as finite element analysis or some other method or is it emperical?

I don't understand what you meant by "where a brace touches all the layers".

More seat-of-the-pants based on lots of experience. Translams often seem to crack apart at the plys. A brace that is machined into a slice will only brace that piece with decreasing effect as you are more glue layers away.

Imagine that the shell of this box was a horizontal translam. Then the individually cut braces would contact each layer (the lower cross-braces do not reach full-height as no early reflection surface is wanted behind the driver.



dave

tortugaranger

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #27 on: 11 Apr 2016, 06:22 pm »
More seat-of-the-pants based on lots of experience. Translams often seem to crack apart at the plys. A brace that is machined into a slice will only brace that piece with decreasing effect as you are more glue layers away.

Imagine that the shell of this box was a horizontal translam. Then the individually cut braces would contact each layer (the lower cross-braces do not reach full-height as no early reflection surface is wanted behind the driver.

dave

Thank you Dave. Great answer and perfect illustration. Very useful. Although I've a hard time imagining properly glued/clamped etc. tranlams coming apart at the plys, but, as with most things, if not executed properly, bad things can eventually happen.

planet10

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #28 on: 11 Apr 2016, 06:25 pm »
I have been following translams since Andy invented the term over a decade & a half. Well executed seems to not be immune to cracking. It seems inherent in using the material in a different "direction" than it was designed for.

dave

KR500

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Re: Not enough bass from Audio Nirvana 10" Classic Driver
« Reply #29 on: 28 Apr 2016, 08:04 pm »
I really liked the sound of my Cast Frame  AN12's although they took quite a long time to loosen up .
I have a small house and a bad back or I'd put the AN 12's in a 5.6 cu. ft. set of cabs so they could shine.  I put them upstairs in some old EV cabinets as a spare listening area and subbed the Seas 8 inch full ranger in the exact same 2.8 cabinets and bass/balance is much better . I added a 3/4" baffle to the front and the bracing on the inside was added to the original plans when I originally built them . Acoustic tile on the upper 1/3 of the cabinet walls and top,  a ball of acousta-stuff resting in the bottom of the enclosure . I have a very small amount of BSC on the Seas 2.8 and they work well placed against the wall . I used to have them toed in, but like them more flush to the wall and imaging is still the same .
The Audio Nirvanas sound better with my SET amp than the AB Tube amp, which sounds better with the Seas full rangers.
 
« Last Edit: 28 Apr 2016, 09:49 pm by KR500 »