Design suggestions using 6.5” Peerless NPT-11-078-1

[grimberg]

During BAF 2008 Jack Hidley generously handed out some 6.5” Peerless NPT-11-078-1 drivers, the subwoofer used in the NHT Super Two and Super Sub loudspeakers. I brought some home with me and would like to use them in a project. I am asking for design ideas and am sure other people will be interested as several attendees took home the same driver.
On Jack Hidley’s personal page at http://home.comcast.net/~jhidley/ there is a link to an Excel spreadsheet containing T/S parameters and related information for this and other drivers. Here is what it says about the NPT-11-078-1.

Part # : npt-11-078-1
Used in NHT models : Super Sub Super 2
Brand : Peerless
Size : 6.5"
Shielded : No
Basket : Steel
Cone material : Laminated poly
Re (Ohms) : 4.84
Fs (Hz) : 51.7
Qms : 2.738
Qes: 0.584
Qts: 0.481
Vas (l): 16.10
Cms (m/N): 0.000543
Mms (g): 17.4
Diameter (mm): 136
BL (N/A): 6.85
SPL (2.83V): 87.64
Zmax (Ohms): 27.6
Sd (m^2): 0.01453
Xmax (mm): 4.9
Hg (mm): 6.0
Hvc (mm): 15.7
Former material : Aluminum
# of coil layers : 2
Coil diameter (mm) : 32

 

[grimberg]

One idea could be a design similar to what Jack demonstrated at the event, using six Peerless woofers, a midrange and a tweeter in a sealed cabinet built out of concrete form.
You can see them in the last picture posted by Wavebourn at:

http://www.diyaudio.com/forums/showthread.php?postid=1636814#post1636814

 

[willick]

Grimberg,

You didn't happen to grab enough of these drivers that you could spare a pair did you? I need 2 to repair my actual SuperTwos. Do you have a friend that might have?

Thanks in advance...
-John

see the thread I pathetically started here: http://www.diyaudio.com/forums/showthread.php?s=&threadid=132942

 

[PeteMcK]

they look good down to the low 40s in 30L tuned to 43Hz, down to low 30s -3dB EBS in 40L tuned to 33Hz, double volumes for 2 drivers...

 

[grimberg]

Could you tell me what modeling software you use?

 

[GM]

If you want to wow your friends with big SPL down well below Fs from a little driver, a tapped horn will do it if you don't mind a big cab.

GM

 

[grimberg]

If you want to wow your friends with big SPL down well below Fs from a little driver, a tapped horn will do it if you don't mind a big cab.

GM

I would like to try it. Where can I find more information?

 

[GM]

This long thread has the vast majority of TH knowledge along with many designs and simming programs info and I recommend you browse it all if you're truly interested in designing your own and DLing Hornresp if you have a Windoze machine to work through permutations of existing designs using your driver's specs to find what you consider the best trade-off between gain BW and size.

GM

 

[Andersonix]

Can anyone point us toward a frequency response curve for these NPT-11-078-1 Peerless drivers (Peerless model 850397)? I'd like to know what low-passing at about 4200Hz would look like.

 

[Andersonix]

Grimberg, did you find a good use for these woofers?
I want to use 4 per side in an 8-Ohm TMMMM type arrangement. 88.5 EBP indicates ported, not sealed. I wouldn't mind a TL...

 

[GM]

I'd like to know what low-passing at about 4200Hz would look like.

Since it was used in a sub limited to a 180 Hz XO, odds are not too good.

GM

 

[grimberg]

Grimberg, did you find a good use for these woofers?

I did not. Other projects came up and I decided to build them first, including a pair of BassZillas which became my main speakers.

http://www.diyaudio.com/forums/multi-way/235768-building-basszilla-platinum-edition-fall-2012-a.html

The Peerless speakers are still properly stored in case I find some interesting use for them, or somebody needs them.

 

[Andersonix]

Since it was used in a sub limited to a 180 Hz XO, odds are not too good.

GM

Maybe we get lucky? This combo in the pic didn't sound too bad, so I'd like a second opinion.
Can anyone point toward or post a FR curve?

 

[GM]

Not me, but just from the size of its VC and dust cap [DC] I'm surprised it doesn't sound too bad considering it's got a ~1.26" dia. Vc, so it's done by ~13560"/pi = ~4316 Hz and with a somewhat larger DC that 'clamps' [limits] the diaphragm to a lower frequency I'm guessing it's going to be somewhere in the 1100-1300 Hz range or maybe twice this if you use 4th order.

Guess you're going to have to measure them.

GM

 

[Andersonix]

I hadn't seen a driver's top end roll off determined like that, GM! What are those formulas?
Yeah, I need to measure them.
1100-1300Hz I can live with, as I'm thinking of making isobaric bass units to go along with some Monsoon planars as a desktop speaker (so I want the cabinet small).

One of these needs a pretty large volume (~30L ideally) as well as porting to get any real bass out.
Attached is a composite showing 3 curves from an online box sim using one driver:
Left-most curve is 29L (ideal ported box) F3=~40Hz
Middle curve is 15L ported box, F3=~55Hz
Right-most curve is sealed 15L, F3=~80Hz.

So it looks like a ported box is the only way to make any bass with this woofer?

 

[Andersonix]

Anyone have suggestions on uses for these woofers?

I was playing around a bit for a desktop, but didn't go further...

 

[diyiggy]

Synergy... Baslow's monitors ?

 

[Andersonix]

Diyiggy: Your words mean nothing to google...

 

[diyiggy]

Sorry my bad englidsh und spelling !


I meant synergy design for the cabinet a la bwaslo - look at the avatar : Smalsyns speaker- the guy behind Xsom, synergyCalc. If your drivers are suitable for a synergy design you could make a central way or two little Synergy speaker, who knows ?


Btw what's google ? An ancestor of Nicolas Vasilievitch ?