I'm finally getting around to my first build. After much thinking and for complicated reasons, I've decided to build four 2X12" ported boxes. Front-mounted, possibly push-pull.
(I'll build smallish horns afterwards, probably a 15" Keystone, and will then compare them.)
I'm trying to pick the optimal driver, and am still a little shaky on certain T/S parameters, especially as they relate to box size and to a ported design vs a horn..
I'd REALLY appreciate some opinions:
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I’d like to get the Fb as low as possible. My truck dimensions will allow me to have a Vb of around 4.5 ft/3 to 5 ft/3. Maybe even a bit more. I assume that will get me fairly low, and also increase volume output. I’m thinking a large Vas, plus a low-ish Qts for good control in the large-ish box. Is that correct?
I will be crossing over at around 100 - 120 Hz.
I’ll be using 1 lb of fiberfill per ft/3 of box volume, unless someone has a different recommendation.
The driver must have an alnico magnet, for light weight.
High power handling is not so important, but efficiency is, since most of my gigs often only provide me with one 15a outlet (20a is a luxury.) Therefore, I think a 500w rating per driver is probably enough. However, if you think a higher rated / less efficient driver will sound better, then of course make that your recommendation.
Just looking at B&C for now, I’m leaning towards their 12NW76, due to its low resonant frequency & its high efficiency. It has a high Vas at 2.7 ft/3, so (I think) a 5 ft/3 box should work great with two of them. Yes? Unfortunately, the Qts is somewhat high at 0.41. Is that a problem with a 5 ft/3 Vb?
Would you recommend something different?
For instance, the B&C 12NBX100 is a bit less efficient, and "only" has a Vas of 1.8 ft/3. but it has a Qts of .22.
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Related Questions:
#1:
#2: If I go with a driver like the B&C 12NBX100, which has a Vas of 1.8 ft/3 or less, can I still build boxes with ~ 5 ft/3 Vb so as to get a low tuning and good efficiency?
- Or are the trade-offs not worth it?
I've read that it's "safe" to have the Vb as much as 2X the Vas, but I don't know how accurate that is or (again) what the trade-offs are.
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I need to make these boxes an unusual shape, if that is workable. This is because I need to fit four of them into a small pickup truck, and I want to maximize the Vb while still fitting them easily.
My ideal external dimension is 13” deep x 42.5” x anything at or larger than 21.5” This will result in only about 5” from the inside-back of the cabinet to the driver’s magnet. (or to the speaker surround, in a reverse P-P mounting.) Even less if I put damping material there.
I don’t see why this should be a problem, as internal volume is internal volume, but I’d love to have an “official” OK on this before proceeding.
- For instance, could this possibly cause a problem due to limited port depth?
(I'll build smallish horns afterwards, probably a 15" Keystone, and will then compare them.)
I'm trying to pick the optimal driver, and am still a little shaky on certain T/S parameters, especially as they relate to box size and to a ported design vs a horn..
I'd REALLY appreciate some opinions:
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I’d like to get the Fb as low as possible. My truck dimensions will allow me to have a Vb of around 4.5 ft/3 to 5 ft/3. Maybe even a bit more. I assume that will get me fairly low, and also increase volume output. I’m thinking a large Vas, plus a low-ish Qts for good control in the large-ish box. Is that correct?
I will be crossing over at around 100 - 120 Hz.
I’ll be using 1 lb of fiberfill per ft/3 of box volume, unless someone has a different recommendation.
The driver must have an alnico magnet, for light weight.
High power handling is not so important, but efficiency is, since most of my gigs often only provide me with one 15a outlet (20a is a luxury.) Therefore, I think a 500w rating per driver is probably enough. However, if you think a higher rated / less efficient driver will sound better, then of course make that your recommendation.
Just looking at B&C for now, I’m leaning towards their 12NW76, due to its low resonant frequency & its high efficiency. It has a high Vas at 2.7 ft/3, so (I think) a 5 ft/3 box should work great with two of them. Yes? Unfortunately, the Qts is somewhat high at 0.41. Is that a problem with a 5 ft/3 Vb?
Would you recommend something different?
For instance, the B&C 12NBX100 is a bit less efficient, and "only" has a Vas of 1.8 ft/3. but it has a Qts of .22.
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Related Questions:
#1:
#2: If I go with a driver like the B&C 12NBX100, which has a Vas of 1.8 ft/3 or less, can I still build boxes with ~ 5 ft/3 Vb so as to get a low tuning and good efficiency?
- Or are the trade-offs not worth it?
I've read that it's "safe" to have the Vb as much as 2X the Vas, but I don't know how accurate that is or (again) what the trade-offs are.
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I need to make these boxes an unusual shape, if that is workable. This is because I need to fit four of them into a small pickup truck, and I want to maximize the Vb while still fitting them easily.
My ideal external dimension is 13” deep x 42.5” x anything at or larger than 21.5” This will result in only about 5” from the inside-back of the cabinet to the driver’s magnet. (or to the speaker surround, in a reverse P-P mounting.) Even less if I put damping material there.
I don’t see why this should be a problem, as internal volume is internal volume, but I’d love to have an “official” OK on this before proceeding.
- For instance, could this possibly cause a problem due to limited port depth?
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FWIW, Here are the three most likely candidates from B&C: (I will of course use a different brand if recommended, but B&C is a safe / known brand for me.)
B&C 12 NW76
sensitivity: 98.5 dB
RMS: 500w
frequency range: 40 Hz - 2.0 KHz
fs: 40 Hz
total Q (Qts) .41 - This is high, so I think good for larger boxes.
Vas: 2.70 cubic ft
BL Factor: 25.5 T-M
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B&C 12NBX100
sensitivity: 96 dB
RMS: 1,000w
frequency range: 40 Hz - 1.5 KHz
fs: 41 Hz
total Q (Qts) .22
Vas: 1.80 cubic ft
BL Factor: 25.6 T-M
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B&C 12BG100
sensitivity: 93 dB
RMS: 1,000w
frequency range: 40 Hz - 1.0 KHz
fs: 39 Hz
total Q (Qts) .33
Vas: 1.45 cubic ft
BL Factor: 23.0 T-M
B&C 12 NW76
sensitivity: 98.5 dB
RMS: 500w
frequency range: 40 Hz - 2.0 KHz
fs: 40 Hz
total Q (Qts) .41 - This is high, so I think good for larger boxes.
Vas: 2.70 cubic ft
BL Factor: 25.5 T-M
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B&C 12NBX100
sensitivity: 96 dB
RMS: 1,000w
frequency range: 40 Hz - 1.5 KHz
fs: 41 Hz
total Q (Qts) .22
Vas: 1.80 cubic ft
BL Factor: 25.6 T-M
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B&C 12BG100
sensitivity: 93 dB
RMS: 1,000w
frequency range: 40 Hz - 1.0 KHz
fs: 39 Hz
total Q (Qts) .33
Vas: 1.45 cubic ft
BL Factor: 23.0 T-M
The Qts on the B&C 12 NW76 is very low (not 0.41).
From these drivers I would probably pick the B&C 12BG100. However, these are all low to medium Vas drivers with fairly low Qts and are more horn/ (6th order and above) BP oriented than reflex. Also their Fs is on the high side if you want to them to drop low.
I would look at drivers like the Eminence Lab12, which will drop low in a reflex cabinet of your intended size.
Johan
From these drivers I would probably pick the B&C 12BG100. However, these are all low to medium Vas drivers with fairly low Qts and are more horn/ (6th order and above) BP oriented than reflex. Also their Fs is on the high side if you want to them to drop low.
I would look at drivers like the Eminence Lab12, which will drop low in a reflex cabinet of your intended size.
Johan
Question: how low does it need to go?
I ask because flat-to-40Hz is good enough to make a lot of small/medium-format PA systems sound wimpy in comparison.
Trying to go lower will mean increased cone displacement and power inputs, for something that might be rarely (if ever) used.
FWIW, take a look at the Powersoft T-series amps. I really like them, and one of the important features is you can directly limit their mains current draw.
Chris
I ask because flat-to-40Hz is good enough to make a lot of small/medium-format PA systems sound wimpy in comparison.
Trying to go lower will mean increased cone displacement and power inputs, for something that might be rarely (if ever) used.
FWIW, take a look at the Powersoft T-series amps. I really like them, and one of the important features is you can directly limit their mains current draw.
Chris
Wow, how did I get that wrong? (thanks, Johan.) I must have copied from a retailer that made a mistake. Indeed, it's .16
But isn't a really low Qts a GOOD thing for this application?
You write, "From these drivers I would probably pick the B&C 12BG100. However, these are all low to medium Vas drivers with fairly low Qts and are more horn/ (6th order and above) BP oriented than reflex. "
OK, but WHY would you pick that driver?
And everything I'm reading says low Qts tends to work for ported, while HIGH Qts works for horns. Are you sure about your statement here? (I have no idea, other than whatI've already read elsewhere.)
The Lab12 is a known product (I'd probably use the newer "C" version,) but it's too heavy. An alnico version of that might be good, but it doesn't exist.
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I spoke with a tech at B&C today, and he strongly recommended their 12BG76, but to me the numbers look all wrong. It resonance is only 44 Hz, it's Qts is .41, and its Vas is only 1.13 ft/3.
- Yet he was adamant that this would be best. Something about total excursion being more important than other factors. I'm REALLY confused now.
He also started explaining things like how sensitivity and efficiency are not the same. - But I still don't understand how a driver with 92 dB sensitivity is a good idea when I only have maybe 7-8 total for the subs amps.
Well, I'm starting to think that T/S parameters are only good for figuring box size and port tuning. They don't seem to help in determining the sound of your end-product.
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Hey, Chris.
I have no idea. I need to build the things, then play around with the port depth while listening to the results. But as a professional audio engineer, I know that I just LOVE good LF extension. No idea if that will translate to rock music in a bar.
My basic idea is to make the largest Vb I can, while fitting four boxes into my available truck space. That gives me a starting point with as much low tuning potential, and as much efficiency, as possible. I will tune them from there.
I guess. 🙁
So any suggestions, other than the Lab12?
I need to order something in the next day or two, and am really stuck here.
I need to order something in the next day or two, and am really stuck here.
For ported best is a QTS of 0.30 to 0.45 and an EBP of +50. The B&C 12BG100 is a good one, just like the BMS 12N630 or the Emminence Lab12 (but the sensivity is relative low for a p.a. speaker). And the Ciare 12.00SW could also be a good candidate i think.
Thanks, Waxx.
That BMS was looking very good, until I saw the Vas. I think it would be excellent in a smaller box than I plan on building, and in fact they recommend a max of 1.5 ft/3 per driver.
STILL, i also realize that Vas, by itself, doesn't necessarily mean too much. Ughh..
Well, I'm liking that B&C 12BG100 as you guys do. Not super-sensitive, but a lot better than the Lab12. Vas is still a bit low, though. Well, it's higher than the one the B&C twch recommended. It also has a 14mm Xvar, which the B&C tech thought was of critical importance. (I don't understand why, since I don't need to slam these, but ok...
- But why that one, rather than the 12NBX100/ the 12NBX100 has better sensitivity, a LARGER Vas, almost as low a Qts, (.33 vs .22 ) and still an acceptable 10mm Xvar. Why do you see the 12BX100 as a better choice? Is the Qts that important?
That BMS was looking very good, until I saw the Vas. I think it would be excellent in a smaller box than I plan on building, and in fact they recommend a max of 1.5 ft/3 per driver.
STILL, i also realize that Vas, by itself, doesn't necessarily mean too much. Ughh..
Well, I'm liking that B&C 12BG100 as you guys do. Not super-sensitive, but a lot better than the Lab12. Vas is still a bit low, though. Well, it's higher than the one the B&C twch recommended. It also has a 14mm Xvar, which the B&C tech thought was of critical importance. (I don't understand why, since I don't need to slam these, but ok...
- But why that one, rather than the 12NBX100/ the 12NBX100 has better sensitivity, a LARGER Vas, almost as low a Qts, (.33 vs .22 ) and still an acceptable 10mm Xvar. Why do you see the 12BX100 as a better choice? Is the Qts that important?
Okay, what's your reference system?
When I was getting started, I was lucky enough to play with a big pile of Nexo Alpha, which is flat to 40Hz. As a result, all of my PA subwoofers are also flat-to-40Hz - I find it very obvious when something drops off at 50Hz.
IMO, going much below 40Hz is too much of a compromise in terms of maximum SPL and logistics. ie, if you want to try to get to 20Hz, you're going to need 4x the cabinets (and amplifiers) to match in SPL, and then you're going to have to carry the things. Since low-E on a bass guitar is 41Hz, there's not much reason to go lower, unless designing for a particular genre of music that requires it.
I'd strongly recommend that you download WinISD Pro/Alpha and make some graphs - you'll learn a lot about how drivers and cabinets interact.
A lot of the drivers you're looking at are going to give very peaky responses when put in a big box tuned low. They'll also use their excursion quickly in the (IMO) useful LF range, because the box isn't helping much there.
Apologies if this is all quite negative, but I'm trying to save you from wasting a load of money.
Chris
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Thanks, Chris. Yeah, I don't intend to go with a lower tuning than maybe 38 Hz. - And I only pick that number because it's the aprox -3dB point of several excellent commercial 2X12" boxes with similar Vb. (JTR Captivator, Yorkville Paraline, etc.)
My studio systems are ridiculously high end, and I have three different ones... The big guns use sealed subs, (eight 10" drivers total) so flat to about 8 Hz. My beloved KRK E8 mid-fields (With the original yellow focal tweeters) have a bit of a roll-off, even though no compression, and you can really tell when 40 Hz is a bit low.
I have a feeling that the B&C tech recommended the driver he did only because it's what they recommend for their 12" BP design, and that of course has lousy LF extension, so a resonant frequency of 44 Hz is fine. I'm starting to think that this guy doesn't know as much as he thinks. I could not pull the trigger today and pop $1300 (to do the first pair of subs) on something that just doesn't seem right.
I'm also now out of time. My old subs & amp blew at my last gig, and I need something for a 300 person gig in 7 days. I have some empty 2X12" cabs that I can get by with temporarily (they even have crappy plate amps) so if I can just order some drivers, I'll get through next week, but I'm STUCK.
This is not good.....
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Asa for running the numbers: I have Winsd, and a few others. The problem is, as I see it this will only tell me the optimal port size for a given Vb and driver, plus the point at which to set the HPF. It doesn't help at all with determining sound quality. That's why I need you guys.
Some interesting thoughts:
The Lab12 is, again, a well-known choice for this kind of box. And the newer 12C looks even better.
- But it's heavy, and the sensitivity is very low. Plus, I doubt the quality can match some high-end B&C or BMS driver. (It might not matter in a sub, but why not try for the best?)
Some of the most well-respected 2X12" designs, including the famous DIY Lab12 box, all use drivers with ceramic magnets. Maybe because there IS no suitable alnico driver available? - And some of these boxes are awfully heavy. The Paraline, for instance is 120 lbs! I simply can't get that up a flight of stairs by myself, with the foldable hand truck I carry. (I have no room for a stair-climber hand truck.)
The JTR is only 69 lbs (And still around 4.5 ft/3 as far as I can calculate. He MUST be using an alnico driver, but the website says he has them custom-made. I can't go with his design, since I can't buy those drivers. (And I can't use his subs because the dimensions don't work with my truck.)
Ughh....
My studio systems are ridiculously high end, and I have three different ones... The big guns use sealed subs, (eight 10" drivers total) so flat to about 8 Hz. My beloved KRK E8 mid-fields (With the original yellow focal tweeters) have a bit of a roll-off, even though no compression, and you can really tell when 40 Hz is a bit low.
I have a feeling that the B&C tech recommended the driver he did only because it's what they recommend for their 12" BP design, and that of course has lousy LF extension, so a resonant frequency of 44 Hz is fine. I'm starting to think that this guy doesn't know as much as he thinks. I could not pull the trigger today and pop $1300 (to do the first pair of subs) on something that just doesn't seem right.
I'm also now out of time. My old subs & amp blew at my last gig, and I need something for a 300 person gig in 7 days. I have some empty 2X12" cabs that I can get by with temporarily (they even have crappy plate amps) so if I can just order some drivers, I'll get through next week, but I'm STUCK.
This is not good.....
------------------------
Asa for running the numbers: I have Winsd, and a few others. The problem is, as I see it this will only tell me the optimal port size for a given Vb and driver, plus the point at which to set the HPF. It doesn't help at all with determining sound quality. That's why I need you guys.
Some interesting thoughts:
The Lab12 is, again, a well-known choice for this kind of box. And the newer 12C looks even better.
- But it's heavy, and the sensitivity is very low. Plus, I doubt the quality can match some high-end B&C or BMS driver. (It might not matter in a sub, but why not try for the best?)
Some of the most well-respected 2X12" designs, including the famous DIY Lab12 box, all use drivers with ceramic magnets. Maybe because there IS no suitable alnico driver available? - And some of these boxes are awfully heavy. The Paraline, for instance is 120 lbs! I simply can't get that up a flight of stairs by myself, with the foldable hand truck I carry. (I have no room for a stair-climber hand truck.)
The JTR is only 69 lbs (And still around 4.5 ft/3 as far as I can calculate. He MUST be using an alnico driver, but the website says he has them custom-made. I can't go with his design, since I can't buy those drivers. (And I can't use his subs because the dimensions don't work with my truck.)
Ughh....
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Chris, I believe you. - but can you explain what parameters tell you this?
What I really need is to understand how the numbers translate to real-world boxes, and this info is very hard to find.
Thx.
- Also, while excursion control is obviously important, does a peaky response really matter much if I have excellent upstream EQ? (I use an EAW UX48) I know it's not ideal, but is it really so bad to just smooth it out electronically?
(Does that peaky response change with amplitude?)
I realize that EQ adds a little phase shift, but in the subwoofer range that can't be a huge deal, right?
Thx.
(Does that peaky response change with amplitude?)
I realize that EQ adds a little phase shift, but in the subwoofer range that can't be a huge deal, right?
Thx.
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Still hoping for some more details on driver choice.
In the meantime, I just realized that Eminence DOES have a sort-of alnico version of their Lab12C, The Kappalite 3012LF. They're only $210 each, so if I can't get any more info on how parameters affect sound, I may just buy four of these and give them a try in my current cabinets.
I doubt they're "the best," but at least Eminence has a track record of making decent drivers for this exact application.
In the meantime, I just realized that Eminence DOES have a sort-of alnico version of their Lab12C, The Kappalite 3012LF. They're only $210 each, so if I can't get any more info on how parameters affect sound, I may just buy four of these and give them a try in my current cabinets.
I doubt they're "the best," but at least Eminence has a track record of making decent drivers for this exact application.
You keep using the word alnico, but the standard material for light weight loudspeaker magnets is Neodymium (well, alloys based on that metal if we're being picky).
Alnico is rarely found in pro/PA type drivers and won't save you as much weight (compared to ferrite) as Nd.
The Kappalite you mention is definitely not alnico.
Alnico is rarely found in pro/PA type drivers and won't save you as much weight (compared to ferrite) as Nd.
The Kappalite you mention is definitely not alnico.
My bad! Yes, I meant Neo. (I guess I have guitar pickups on my brain. lol...)
Well, I ordered for Kappalites, as I'm out of time, but I fear I made a big mistake. I thought they were a Neo version of the Lab12's, but they are not.
Their Fs is good, and the other specs are mostly excellent, but they only have 9.1 mm Xmax, vs 13mm for the Lab12C. They also have a low BL at only 16.71.
They have a frequency rateing of 46 Hz - 2K, though I doubt that matters.
What really bugs me is a thread I just read where someone said the cones were a bit thin for subwoofer use. (And again, things like distortion from cone flex are not going to show in Winsec.)
Well, the Lab12's are just too heavy, so I guess we'll see. If they suck, at least they weren't too expensive. - And I'll have them in time for my gig.
Well, I ordered for Kappalites, as I'm out of time, but I fear I made a big mistake. I thought they were a Neo version of the Lab12's, but they are not.
Their Fs is good, and the other specs are mostly excellent, but they only have 9.1 mm Xmax, vs 13mm for the Lab12C. They also have a low BL at only 16.71.
They have a frequency rateing of 46 Hz - 2K, though I doubt that matters.
What really bugs me is a thread I just read where someone said the cones were a bit thin for subwoofer use. (And again, things like distortion from cone flex are not going to show in Winsec.)
Well, the Lab12's are just too heavy, so I guess we'll see. If they suck, at least they weren't too expensive. - And I'll have them in time for my gig.
I suggested the Lab 12 because I thought you wanted to go really low (20 - 30 Hz) but for rock in a bar 40 Hz is all you need.
Next 300 people event you have I would rent 4 to 8 x 18" subs. Good luck!
Next 300 people event you have I would rent 4 to 8 x 18" subs. Good luck!
"I'm finally getting around to my first build. After much thinking and for complicated reasons, I've decided to build four 2X12" ported boxes. Front-mounted, possibly push-pull."
You might be interested in reading the Push-Push thread. There is good info there on Push-Pull vs Push-Push.
You might be interested in reading the Push-Push thread. There is good info there on Push-Pull vs Push-Push.
Cableaddict,
1)No. No. No.
2) The phase shift caused by corrective IIR filters is the inverse of the phase response of the cabinet prior to correction, the EQ flattens both frequency and phase response.
3)Doubling Xmax gives a potential 6 dB increase in level, you will be giving up about 3dB in the 1/3 octave region above Fb (box tuning), but gaining sensitivity over most of the sub woofer pass band compared to the LAB 12 and other high mms drivers.
BL of 16.7 is not particularly low for a bass reflex driver.
4)True.
5) The 3015LF cone is light for the high stress from a high compression ratio FLH or TH, but OK for bass reflex driven within Xmax and thermal limits. The lighter cone will make them far more sensitive in the upper range (60Hz up) so will be subject to less power compression overall than the LAB 12. Other than a narrow range, you'll have more bass output.
6)They won't suck. Using a 36-38Hz Fb, should have plenty of LF, and you won't miss any that is when load 115 pounds less weight.
Art
Thanks, Art. That's extremely helpful.
If you have an extra few minutes - do you think any of the B&C drivers would be a better choice than the Kappalite? Does that B&C tech's choice of the 12BG76 make any sense?
Here are the important specs:
frequency range: 45 Hz - 1.0 KHz
fs: 44 Hz
Qes: 0.44 - Getting a little bit high, but not horrible.
EBP: 100
total Q (Qts) .41 - good, but not optimal.
compliance (Vas) 1.13 cubic ft
BL Factor: 23.0 T-M
Xmax: 9.5mm
Xvar: 14mm
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BTW, I'm looking forward to finally building some Keystones, next. But I'll only be using them when I have bandmates to help move them up any stairs. These dual 12's are for my solo & DJ gigs
If you have an extra few minutes - do you think any of the B&C drivers would be a better choice than the Kappalite? Does that B&C tech's choice of the 12BG76 make any sense?
Here are the important specs:
frequency range: 45 Hz - 1.0 KHz
fs: 44 Hz
Qes: 0.44 - Getting a little bit high, but not horrible.
EBP: 100
total Q (Qts) .41 - good, but not optimal.
compliance (Vas) 1.13 cubic ft
BL Factor: 23.0 T-M
Xmax: 9.5mm
Xvar: 14mm
-----------------------------------------------
BTW, I'm looking forward to finally building some Keystones, next. But I'll only be using them when I have bandmates to help move them up any stairs. These dual 12's are for my solo & DJ gigs