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Old 3rd October 2012, 02:18 PM   #1
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Default Cabinet Calculations help please

I am building a woofer section and am using the new Seas 10" driver (L26RO4Y-D0004) as a woofer not a subwoofer. It says it need a .6cf sealed cabinet but doesn't specify the total Q. I like a Q of .5 with an F3 of about 50hz. I'll be using this in a system that has a subwoofer that goes up to 50hz. I have included a link for all the specs in the driver number above.

Does someone have software, or know of a place I can go online, to model this? I'm just looking for a simple sealed cabinet.

Thanks,
Paul
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Old 3rd October 2012, 02:25 PM   #2
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Loudspeaker Design Software

If you don't have Excel, search for WinISD.

Quote:
Originally Posted by Ultima GTR View Post
I am building a woofer section and am using the new Seas 10" driver (L26RO4Y-D0004) as a woofer not a subwoofer. It says it need a .6cf sealed cabinet but doesn't specify the total Q. I like a Q of .5 with an F3 of about 50hz. I'll be using this in a system that has a subwoofer that goes up to 50hz. I have included a link for all the specs in the driver number above.

Does someone have software, or know of a place I can go online, to model this? I'm just looking for a simple sealed cabinet.

Thanks,
Paul
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Old 3rd October 2012, 03:12 PM   #3
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Ultima GTR
If you download and use the "Woofer box model and circuit designer" software, which I do recommend for a simple sealed box, then also download the "Diffraction and Boundary simulator".
They are both free, and the Diffraction-Boundary sim allows you to add the room response into the final SPL and other output graphs.
.
Both programs are simple, easy to use and allow you to include crossover and equalizer response and then add room response to see how the final system will sound, in your room.
.
When I say simple, I mean compared to WinISD.
There is a learning curve but it is much shorter.

My .02

Dave
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Old 3rd October 2012, 09:40 PM   #4
DrNick is offline DrNick  United Kingdom
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Quote:
Originally Posted by Ultima GTR View Post
I am building a woofer section and am using the new Seas 10" driver (L26RO4Y-D0004) as a woofer not a subwoofer. It says it need a .6cf sealed cabinet but doesn't specify the total Q. I like a Q of .5 with an F3 of about 50hz. I'll be using this in a system that has a subwoofer that goes up to 50hz. I have included a link for all the specs in the driver number above.

Does someone have software, or know of a place I can go online, to model this? I'm just looking for a simple sealed cabinet.

Thanks,
Paul
I tried modelling this one, as I have been looking at all sorts of drivers, and it has a problem for use as a woofer, in that the voice coil inductance appears to be very high, at 3.85 mH, which should limit the output at higher frequencies. I found that I could not get the T/S parameters as SEAS has given them, if I input the mechanical parameters I get this

Click the image to open in full size.

Using these, WinISD predicts a very peaked response indeed. Here is a link to the WinISD file.

Click the image to open in full size.

This does not looks like it will work easily as a woofer instead of a subwoofer.

Not sure if this figure of 3.85 mH can be right, as the spec sheet also gives 20-1000 Hz as the recommended range, but I can not see how to reconcile the inductance with this range.

All the best,

Nick.

Last edited by DrNick; 3rd October 2012 at 09:44 PM.
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Old 3rd October 2012, 09:47 PM   #5
tvrgeek is offline tvrgeek  United States
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Nick, Welcome to the world of simulation. A driver designed as a sub will be fairly high mass, big VC and basically, not a great woofer. Might try the XXLS Peerless 12 '500 as they are fine up to about 200.
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Old 3rd October 2012, 11:38 PM   #6
DrNick is offline DrNick  United Kingdom
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Quote:
Originally Posted by tvrgeek View Post
Nick, Welcome to the world of simulation. A driver designed as a sub will be fairly high mass, big VC and basically, not a great woofer. Might try the XXLS Peerless 12 '500 as they are fine up to about 200.
Thanks TVRGeek, but just to be clear, this isn't my thread, I was replying to the OP, Ultima-GTR. I'm building a sub, which is why I had modelled the SEAS driver which he is wondering about using as a woofer. The lowest Voice Coil Inductance Sub driver I found when I was looking was the Tangband WQ-1858. The Vifa NE315W-08 is also quite low with a modelled f3 of 2 kHz. The Peerless 835017 XXLS comes out with f3 at 900 Hz.

The problem is that these models just tell you if the sound is likely to be coming out at the right volume, not how it will sound! The Tangband models with f3 at 9 kHz, but if you look at the info page here it looks like it breaks up at over 400 Hz. The Vifa looks like it might be fine up to 1 kHz, as does the Peerless.

The part I find tricky is that if you look at the frequency response curves shown on the vendor's page for the SEAS driver, it looks flat to 1 kHz, but then if you try to model it, the response ought to be dropping off from 100 Hz. What is the technical reason the plots looks nothing like each other?
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Old 3rd October 2012, 11:51 PM   #7
sreten is online now sreten  United Kingdom
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Hi,

Driver inductance modelling in most bass box sims is awful, you may as
well turn it off or set driver Le to zero. Driver response does not follow
a 1st order roll-off based on Re and Le and that is all that they indicate.

rgds, sreten.

Generally using a sub as a bassmid is a waste of time, use a bassmid.
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Old 4th October 2012, 12:07 AM   #8
DrNick is offline DrNick  United Kingdom
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Quote:
Originally Posted by sreten View Post
Hi,

Driver inductance modelling in most bass box sims is awful, you may as
well turn it off or set driver Le to zero. Driver response does not follow
a 1st order roll-off based on Re and Le and that is all that they indicate.

rgds, sreten.

Generally using a sub as a bassmid is a waste of time, use a bassmid.
Thanks, I've been playing with WinISD, but I'm not sure how much to reply on the predictions.

To go back to the original question, 0.66 cubic feet sealed gives a Qtc of 0.5 for this driver, but f3 is up at 80 Hz or so. It seems designed to be vented or to go with a passive radiator.
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Old 4th October 2012, 05:04 AM   #9
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Thanks everyone for your input. I've selected this driver for this because Mr Linkwitz selected it for the most recent version of the Orion. My thought was to use this within the same frequency range he does which is approximately 50hz to 120hz. I realize he uses it in a baffle and I'm suggesting a sealed box and I would rather use it (or rather 2 like he does) in a baffle too but I don't have the level of knowledge necessary to offset the cancelation loss at lower frequencies. If someone knows how to overcome that loss, please do share. Thanks again for your valuable comments.
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Old 4th October 2012, 09:12 PM   #10
GM is offline GM  United States
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Using Hornresp to 'iron out' T/S discrepancies yields a 0.54 Qtc in ~0.502634 ft^3 net with a calc'd ~78.5 Hz F3, 50.5 Hz Fb.

A much more realistic half space [2pi] sim done using MJK's MathCad software [zero stuffing density since it's an acoustically tiny, ~golden ratio cab]:

GM
Attached Images
File Type: gif Seas L26R04Y_D0004 0.5 Qtc sealed.gif (6.7 KB, 83 views)
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