I just got my hands on a pair of SB Acoustic 12'' woofers. The FS is 19Hz and the QES is .42. My choices are to build 4.0 cubic ft of volume ported cabinets or 2.6 cubic ft of volume sealed cabinets. The woofers will be working with midranges and tweeters. What direction should I take. Thanks.
In Martin Colloms book "High Performance Loudspeakers" he makes the general comment that subjectively the sealed (2nd order) appears to have more bass than a 4th order reflex despite the theoretical advantages of the latter......all things being equal (Which they seldom are!). He tentatively puts this down to less phase change in the former. But sensitivity to phase seems to vary a lot........
Are you in a position to try both before making a final pair?
More work but could be an interesting exercise.
Cheers, Jonathan
Are you in a position to try both before making a final pair?
More work but could be an interesting exercise.
Cheers, Jonathan
Hi Ccdave !
For example:
SB 34 NRX75-6
Fs=19 Hz
Re=4,2 ohms
Qts=0,4
Vas=260 liter
Passive box, flat response, low F3 =ported box, Vb= 250 liters, F3=20 Hz
Passive box, flat response, high F3 = sealed box, Vb=55 liters, F3= 50 Hz
Calculated values of Vb and F3 might not be totaly accurate, more like a guideline.
For example:
SB 34 NRX75-6
Fs=19 Hz
Re=4,2 ohms
Qts=0,4
Vas=260 liter
Passive box, flat response, low F3 =ported box, Vb= 250 liters, F3=20 Hz
Passive box, flat response, high F3 = sealed box, Vb=55 liters, F3= 50 Hz
Calculated values of Vb and F3 might not be totaly accurate, more like a guideline.
Btw Wayne Queensland, where I live, is in Australia the home of Neville Theile and where Richard Small did his work so we're really BIG on vented encloses down here.....at least in theory..ha, ha.
It is interesting that Theile's work became known through the JAES in the early '70's but had been published locally some ten years before and just wasn't recognised for the break through that it was.
It is interesting that Theile's work became known through the JAES in the early '70's but had been published locally some ten years before and just wasn't recognised for the break through that it was.
Forced to make a choice here......
FWIW I do sit firmly in either camp, I have heard both bad and good outcomes with either application.
Assuming the OP meant "A Qts of .42 (?) " and an Fs of 19; furthermore giving the hint that this will be part of a 3way system, I'd opt for the PROPER vented alignment. I'm thinking that a 3way system will be set up away from room corners/ boundries whereas sometimes a devoted SEALED woofer/subwoofer is placed in or near a room corner and gets the associated room lift along with the shallow slope makes for a better overall compromise. just my 2 cents and not worth much these days
FWIW I do sit firmly in either camp, I have heard both bad and good outcomes with either application.
Assuming the OP meant "A Qts of .42 (?) " and an Fs of 19; furthermore giving the hint that this will be part of a 3way system, I'd opt for the PROPER vented alignment. I'm thinking that a 3way system will be set up away from room corners/ boundries whereas sometimes a devoted SEALED woofer/subwoofer is placed in or near a room corner and gets the associated room lift along with the shallow slope makes for a better overall compromise. just my 2 cents and not worth much these days
The Qts is more suitable for vented. I don't believe in small enclosure for woofer like this. It seems that the woofer has been designed for vented in mind?? Just be aware that you may require bigger room.
I like (the transient of) a closed cabinet, and I hate it when certain woofer is more preferable for vented design.
I like (the transient of) a closed cabinet, and I hate it when certain woofer is more preferable for vented design.
I think their the same woofers used in the zaph audio sb12.3 design.
He documents all his designs well and goes into detail. Ud be able to get some data i think he used a sealed box and mentioned room gain and stuff and if you happy with that performance make a varience of if u want to go lower then u have to go ported.
Me I have a sealed 12 inch plays -6db @20hz without room gain very clean but not very sensitive for HT.
Then again my preferance is sealed always if the woofer can play low enough if not then id port it. However im not hard and fast either way port or sealed I have also heard good and bad of both.
Just seald can be a bit fussy with damping material
Actually to be honest I was recently looking at 2x sb acoustic 10 inches in one ported 75litre enclosure and about 600WRMS for high power/sensitivity HT sub and push my current 12 inch to my hi fi system...but...im gonna use that money for scan speak revelator/air circ mains.
He documents all his designs well and goes into detail. Ud be able to get some data i think he used a sealed box and mentioned room gain and stuff and if you happy with that performance make a varience of if u want to go lower then u have to go ported.
Me I have a sealed 12 inch plays -6db @20hz without room gain very clean but not very sensitive for HT.
Then again my preferance is sealed always if the woofer can play low enough if not then id port it. However im not hard and fast either way port or sealed I have also heard good and bad of both.
Just seald can be a bit fussy with damping material
Actually to be honest I was recently looking at 2x sb acoustic 10 inches in one ported 75litre enclosure and about 600WRMS for high power/sensitivity HT sub and push my current 12 inch to my hi fi system...but...im gonna use that money for scan speak revelator/air circ mains.
If this is for primarily a music speaker, I'd go sealed. I like the Fs to be in the upper teens to lower 20s for good bass response in a sealed cab. Keep Qtc to around .7 for a nice roll off that can be equalized if desired.
As a fan of ported cabs, I tried a couple sealed designs and must say, I'm quite impressed with the sound. Transient response is the best with seal cabs, so perhaps that is the reason.
If the use is home theater or you're shy on amp power, certainly consider ported.
As a fan of ported cabs, I tried a couple sealed designs and must say, I'm quite impressed with the sound. Transient response is the best with seal cabs, so perhaps that is the reason.
If the use is home theater or you're shy on amp power, certainly consider ported.
I'd suggest reading up on Zaph's project using the SB 12" woofer for some insight, too. His sealed Vb is 3.78 compared to madisounds "recommended 2.6" .... ported looks to me like you'd need a 5.6 cu.ft. box for a similar plot in (WinISD at least)*. *This comparison/ratio is based on Zaphs choice of Vb for sealed and trying to hold the same response for ported (5.6 Vb .. 18hz Fb).
Sealed goes plenty low ... no? (modeled 20hz F10 w/3.78 Vb)
Sealed goes plenty low ... no? (modeled 20hz F10 w/3.78 Vb)
You'll get a lot of opinions so here's one more. Very few drivers are suited to unequalized sealed designs. When they are, the result is usually favored by a large number of people. Think old AR. Most drivers don't do well in a sealed box with the traditional Q of 0.707, in fact they sound thin and tinny. A Q of about 0.9 works better, but certainly isn't going to be flat. If you have to equalize, the power required goes up significantly, but it's still a good option. Vented enclosures have fallen out of favor with many, but I still like 'em if designed correctly. That means breaking in the driver for a good long while and then making your own measurements for the parameters. Finally, skeptic though I am, "infinite" baffle can have really good musicality.
There have been some pretty good stuffed vent designs, Dynaco A25 and similar, and some excellent transmission lines, but I've no good deterministic way to design those.
There have been some pretty good stuffed vent designs, Dynaco A25 and similar, and some excellent transmission lines, but I've no good deterministic way to design those.
I've flip-flopped like a politician
Having gone back thru and actually looked at the specs of the driver in question, I now must side with the "sealed" crowd. I'd make it a 4 cubic footer, though. The EPB is beggin for a sealed enclosure.
*** Just for comparison, a "proper" (by proper, I mean the way I would do it, not some similation software) a vented enclosure would require 10.5 cubic feet, and that's just too big for a single 12. A single 12" per side can't move enough air at/or near the tuning frequency anyway.***
And yes, I agree with the others- read Zaph. Have a nice day.
Having gone back thru and actually looked at the specs of the driver in question, I now must side with the "sealed" crowd. I'd make it a 4 cubic footer, though. The EPB is beggin for a sealed enclosure.
*** Just for comparison, a "proper" (by proper, I mean the way I would do it, not some similation software) a vented enclosure would require 10.5 cubic feet, and that's just too big for a single 12. A single 12" per side can't move enough air at/or near the tuning frequency anyway.***
And yes, I agree with the others- read Zaph. Have a nice day.
Not in dem err woods .....
opposite around here !!!! Yep !!!!
Actually , I find the specs better for sealed enclosure, it's actually borderline, most manufacturers list lower QTS numbers than you actually measure, i would not be surprised to hear it's closer to .5 when measured .
May be. Suitability depends on many things. For example, it depends on the midrange and tweeter to be used. But I wont put enclosure size in the list, because we clearly know that if we want a vented box for such woofer then we will have a bigger box. The company has had a long history producing lower end drivers for PA used. They (not this particular woofer) are not suitable for small room because for one thing they require big enclosure. For "borderline" woofers I found that horn works very well. And that means even bigger enclosure.
The fact that they have experience with PA drivers, may get me into thinking that the woofer may have a bit of PA woofer characteristics. One good characteristic is the higher efficiency, which is really needed when choosing a sealed design, which with non-PA drivers usually will give a thin sound.
The OP mentioned about choosing between 4 cuft vented and 2.6 cuft sealed. For better sound I still lean towards the vented option. And why would you choose such a woofer if you wanted a limited bass extension and a smaller room and speaker enclosure???
Hi,
Fs = 19Hz, low, Qts =0.4, moderate, Vas =240L, very big.
Its needs a big sealed box, 115L, 4 cuft for sealed.
Probably 100L well stuffed would do the job.
Zaph used 107L.
Vented even bigger, about 6 cuft, 170L tuned to 18Hz.
"Optimum" venting with just over 8cuft at 19Hz is not
a good idea IMO compared to the above choices.
rgds, sreten.
Fs = 19Hz, low, Qts =0.4, moderate, Vas =240L, very big.
Its needs a big sealed box, 115L, 4 cuft for sealed.
Probably 100L well stuffed would do the job.
Zaph used 107L.
Vented even bigger, about 6 cuft, 170L tuned to 18Hz.
"Optimum" venting with just over 8cuft at 19Hz is not
a good idea IMO compared to the above choices.
rgds, sreten.
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As far as the OP's question is concerned, my take would be that a lot will depend on the room the speakers are going to be used in. Generally speaking a rigid, reinforced concrete frame and brick or stone walls would favor a sealed alignment, whereas a drywall on steel beams construction is better suited to a vented one.
I noticed the OP hasn't stated what type of music he will be listening to with these speakers, or if he is worried about efficiency. For example, if he's mostly into rock and pop, wouldn't a system that makes it flat to @35Hz be suitable? That way he could avoid the huge 4cu/ft enclosure though efficiency would be reduced....but then again, his amp wouldn't be dealing with pipe organ music with bass down to 20Hz so this may be a non-issue.
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