Hi All.
I have been going back and forth on my plan for turning a large 8 cubic foot wooden box I use as a coffee table into a subwoofer. I have a pair of Cerwin Vega 122W2 woofers (used in the D7 speaker) that I measured TS parameters for, and have come up with two possibilities. I would like your opinions on which way I should go, and why. These are the two possibilities....
1. Sealed, with two drivers sharing the same internal volume.
2. Vented, with two drivers in an isobaric configuration, sharing the same internal volume, and tuned to 29 HZ,
I measured both woofers, and they are very close with respect to specs. I have a .wdr file, but I don't think I can attach it here.
I can't find any Xmax data on these drivers, so I guesstimated and put in what i think is a conservative value based upon a few articles I have read online (7mm or.28 inches). Please let me know if you know what the Xmax actually is, or if you think that my estimate is way off.
I have attached two winISD screenshots for your consideration, and am happy to provide more screenshots and info.
Thanks in advance for your replies!
I have been going back and forth on my plan for turning a large 8 cubic foot wooden box I use as a coffee table into a subwoofer. I have a pair of Cerwin Vega 122W2 woofers (used in the D7 speaker) that I measured TS parameters for, and have come up with two possibilities. I would like your opinions on which way I should go, and why. These are the two possibilities....
1. Sealed, with two drivers sharing the same internal volume.
2. Vented, with two drivers in an isobaric configuration, sharing the same internal volume, and tuned to 29 HZ,
I measured both woofers, and they are very close with respect to specs. I have a .wdr file, but I don't think I can attach it here.
I can't find any Xmax data on these drivers, so I guesstimated and put in what i think is a conservative value based upon a few articles I have read online (7mm or.28 inches). Please let me know if you know what the Xmax actually is, or if you think that my estimate is way off.
I have attached two winISD screenshots for your consideration, and am happy to provide more screenshots and info.
Thanks in advance for your replies!
Attachments
8ft3 is big.
All I can find is those are cerwin d7 woofers ?
I'm not a fan of isobarik, but I'll take more spl over box size.
I do like push pull.
Sealed may be a bit too lean if you like rumble.
You can run them in a smaller than ideal ported box.
I've ran 27-30hz tuning (4.3mm and 18's, also 8mm 15's).
The 15's shared a 6-7ft3 box when ideal 4th ported wanted 8ft3 each and 30hz tuning.
Worked very well.
All I can find is those are cerwin d7 woofers ?
I'm not a fan of isobarik, but I'll take more spl over box size.
I do like push pull.
Sealed may be a bit too lean if you like rumble.
You can run them in a smaller than ideal ported box.
I've ran 27-30hz tuning (4.3mm and 18's, also 8mm 15's).
The 15's shared a 6-7ft3 box when ideal 4th ported wanted 8ft3 each and 30hz tuning.
Worked very well.
Last edited:
Thanks for your reply. The outside box size is fixed, but I suppose I could reduce it by inserting the driver baffle into the box. It’s a strange coffee table that is already in my family room.
There is pretty much zero information on the Cerwin Vega drivers that were used in their now vintage speaker boxes. I measured my pair of 122W2 drivers for their use in winISD.
The response on the ported isobaric is flat, while the sealed has more spl at its higher frequencies of operation. I am always looking for flat response as in the ported sim, but the sealed has way more output higher up in frequency. I will be using this sub for HT 80% and music 20%.
Xmas limits on the 122W2 are also a concern of mine as I don’t have that parameter, and it is hard to estimate.
Np, should be fine.
Xmax usually below the tuning (bottoming out the driver), that kills subs.
If you had subsonic protection at tuning, you'd have nothing to worry about.
Xmax usually below the tuning (bottoming out the driver), that kills subs.
If you had subsonic protection at tuning, you'd have nothing to worry about.
There is a highpass filter added to the above sims in order to keep the drivers from exceeding XMAX. In the vented enclosure sim, the tuning (29HZ) is below FS, which is around 35HZ for the 122W2. So, which is best, sealed or vented, for 80% HT and 20% music listening? It seems sealed (higher SPL) would be best for HT and vented (linear frequency response) would be for music?
I would go push-pull vented myself. That graceful response curve of the sealed is pointless as you are going to be cutting off 1/2 of the top part (60-80 hz?) of the curve anyways. What is your EBP?, of course fifty & higher, porting is best...The wild card is the cone to cone asymmetry cancellation effect of push-pull...making for a positive gain in accuracy. With the best designing you come up with...I'd think this the best approach.
---------------------------------------------------------------------Rick........
---------------------------------------------------------------------Rick........
with the sale to Gibson, nothing was transferred as far as legacy data. I think its been transferred at least once or twice since then so all the data is loooooooong gone. cerwin-vega fan forum has some great legacy data posted, but if you measured your own parameters, those are good for use.
the dx7 was a really good speaker, bit more refined than their traditional dorm thumpers. once upon a time I retrofitted a console system with dx7 guts. I like your tuning for ported, right around 30hz, but I would shrink box size to around 3 cu ft to avoid excursion problems. the drivers are likely capable of 8 or 9mm xmax, but remember, they were the low end on a 3 way cab. so practical use xmax is likely 5 or 6mm with solid power.
can you post your measured parameters as a txt file or use a little copy/paste so others might play along?
the dx7 was a really good speaker, bit more refined than their traditional dorm thumpers. once upon a time I retrofitted a console system with dx7 guts. I like your tuning for ported, right around 30hz, but I would shrink box size to around 3 cu ft to avoid excursion problems. the drivers are likely capable of 8 or 9mm xmax, but remember, they were the low end on a 3 way cab. so practical use xmax is likely 5 or 6mm with solid power.
can you post your measured parameters as a txt file or use a little copy/paste so others might play along?
I will post the results from my measurements when I get back to my PC. The drivers I took measurements for are 122W2 that had damaged cones that were repaired and coated with some sort of a hardening material. I think that my measurements will not correspond to an unmolested 122W2. In my sims, there are highpass filters in place to limit cone excursion below tubing. I will post those filters as well.
Please do let me know if you would like more information. The excursion jpeg is for an 8 cubic foot cabinet, with the drivers operating in an isobaric configuration.
Last edited:
I had a look at the push pull configuration. Given the large box size, a push pull slot loaded configuration is doable while also reducing box size due to the slot. PPSL is definitely better with respect to SPL, but models a response that isn't nearly as flat as the isobaric configuration. It will be used mostly for home theatre though, so it may not matter so much.
Attached is a jpeg of the sim comparing the SPL
Attachments
Eek, that's like 9db difference.
That is a huge amount.
What are your measured specs ?
That is the d9 15" woofer, not the dx9 driver if my searching is correct.
Qts
Vas
Fs
Thinking aloud, Vega woofers (for 3 ways) are a bit floppy (say .5 qts), so in an ideal 4th order yuou would have a box bigger than vas (ouch, that gets big) but f3 and tune below speakers fs. I remember testing their dx (3 ways) back in 93, the 10" went lowest, 12 not so much, 15 even less, but 15 had way more output and handled a bit of boost.
We may be able to squish the ideal ported to 1/4 recommended size and still tune to 30hz, not a true ported with a big enough port, but some excursion lessening. That may cause a nice hump under 50hz too.
That is a huge amount.
What are your measured specs ?
That is the d9 15" woofer, not the dx9 driver if my searching is correct.
Qts
Vas
Fs
Thinking aloud, Vega woofers (for 3 ways) are a bit floppy (say .5 qts), so in an ideal 4th order yuou would have a box bigger than vas (ouch, that gets big) but f3 and tune below speakers fs. I remember testing their dx (3 ways) back in 93, the 10" went lowest, 12 not so much, 15 even less, but 15 had way more output and handled a bit of boost.
We may be able to squish the ideal ported to 1/4 recommended size and still tune to 30hz, not a true ported with a big enough port, but some excursion lessening. That may cause a nice hump under 50hz too.
Last edited:
The driver is the one used in the D7, but they came from an earlier model, the R12, that used the same driver. It is a 12 inch driver. The sims are as shown above, and are for a 8 cubic foot box. It is possible to reduce interior volume size by putting the motor board further into the box, which is an odd coffee table that is already built and in place in the family room.
Ah, fs=35.25, qts=.44, vas = 6.7ft3
I see ideal 4th ported wants 9.5ft3.
Have you modeled 2 in an 8ft3 ported to 30hz ?
I see ideal 4th ported wants 9.5ft3.
Have you modeled 2 in an 8ft3 ported to 30hz ?
Yes. All my sims on this thread use two 122W2, in an 8 cubic foot box, with varying driver configuration and port tuning at 29 HZ.
.
Ah, ok, me slow.
I'd use a 10 band eq in the signal chain and yank the 60hz slider down to -9db.
That would give a lot of headroom there.
Weird.
Can you (or anyone please) model 1 driver in an 8ft3 tuned to 30hz vs 2 drivers in an 8ft3 (4ft3 each basically) tuned to 30hz ?
I'd use a 10 band eq in the signal chain and yank the 60hz slider down to -9db.
That would give a lot of headroom there.
Weird.
Can you (or anyone please) model 1 driver in an 8ft3 tuned to 30hz vs 2 drivers in an 8ft3 (4ft3 each basically) tuned to 30hz ?
Last edited:
- Status
- Not open for further replies.