Among other projects, I want to get beck to my idea of possibly improving upon my old sealed 18" system. (Four Bag End s18e's)
It basically comes down to finding the right driver, if it exists. It has to be at least 96dB sensitive at 80Hz, since that's what I have now. More sensitivity, or better sound, and I'll be happy.
## IMPORTANT: This is for live sound, NOT HT.
That's the main reason for this query.
Most sealed cabinet discussion concern HT, so I figure that some "recommended" numbers might only be necessary for ultra-extended LF, and not fully apply to my situation. I only need from about 35-40Hz, through 100Hz. I probably won't even use the Bag End integrator this time, opting instead for dsp Eq or a Driverack. Why boost all that LF, just to roll it off again?
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So I'm looking for that magic driver.
I read that one important parameter is to try to have EBP (Fs/Qes) as low as possible, preferably 50 or less. - But I can't find a single driver that has that number and is also reasonably sensitive. And again, maybe that's not critical with, say a 38Hz HPF?
Supposedly you also want a high Qts, but maybe that comes from car audio guys, trying to use crazy small enclosures? I have 3 ft/3 boxes now, which should give an enclosure Qts close to the "ideal" 0.707, although I don't even know if THAT number is ideal for me. MaybeI should go smaller, and aim for less LF but more overall efficiency? - in which case the required driver parameters might change again.
I'm basically lost here, as you can tell.
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BOTTOM LINE:
I've literally looked at every 18" driver I can find, with 96dB or better sensitivity, and one of the very few that even comes close to some of the other parameters numbers I've read about is the Beyma 18LX60v2.
Can someone with good knowledge of sealed subs take a quick look and see if this will work?
Beyma 18LX60v2:
Sensitivity: 98
xmax 9mm
Qts .48
Fs 35 / Qes .5 = EBP: 70
Beyma Speakers - Beyma 18LX60v2 speaker - Beyma 18LX60v2 1400 watt 18" woofer for all bass applications. Beyma 18LX60v2 and other Beyma 18" speakers here.
- THANKS.
It basically comes down to finding the right driver, if it exists. It has to be at least 96dB sensitive at 80Hz, since that's what I have now. More sensitivity, or better sound, and I'll be happy.
## IMPORTANT: This is for live sound, NOT HT.
That's the main reason for this query.
Most sealed cabinet discussion concern HT, so I figure that some "recommended" numbers might only be necessary for ultra-extended LF, and not fully apply to my situation. I only need from about 35-40Hz, through 100Hz. I probably won't even use the Bag End integrator this time, opting instead for dsp Eq or a Driverack. Why boost all that LF, just to roll it off again?
------------------
So I'm looking for that magic driver.
I read that one important parameter is to try to have EBP (Fs/Qes) as low as possible, preferably 50 or less. - But I can't find a single driver that has that number and is also reasonably sensitive. And again, maybe that's not critical with, say a 38Hz HPF?
Supposedly you also want a high Qts, but maybe that comes from car audio guys, trying to use crazy small enclosures? I have 3 ft/3 boxes now, which should give an enclosure Qts close to the "ideal" 0.707, although I don't even know if THAT number is ideal for me. MaybeI should go smaller, and aim for less LF but more overall efficiency? - in which case the required driver parameters might change again.
I'm basically lost here, as you can tell.
-----------------------------------------
BOTTOM LINE:
I've literally looked at every 18" driver I can find, with 96dB or better sensitivity, and one of the very few that even comes close to some of the other parameters numbers I've read about is the Beyma 18LX60v2.
Can someone with good knowledge of sealed subs take a quick look and see if this will work?
Beyma 18LX60v2:
Sensitivity: 98
xmax 9mm
Qts .48
Fs 35 / Qes .5 = EBP: 70
Beyma Speakers - Beyma 18LX60v2 speaker - Beyma 18LX60v2 1400 watt 18" woofer for all bass applications. Beyma 18LX60v2 and other Beyma 18" speakers here.
- THANKS.
When it comes to sealed boxes, displacement is king. In the case of this driver, the 9mm Xmax isn't bad, but a single B&C 18SW115 would be very close to a pair of those Beyma units.
That Beyma unit driven to Xmax will produce 112.5dB at 40Hz. You might get a little more before it starts sounding really bad, but it'll be somewhere around there.
The sensitivity measurement isn't particularly important in subwoofers - the cabinet has a huge amount of influence over the sensitivity of the finished product.
For instance, in a big sealed box you might get 80dB@1w@20Hz. Make it a tiny sealed box, and it might drop below 70dB@1w@20Hz. A really big tapped horn might be 96dB at 20Hz.
Sensitivity tells you how much power you're going to need before you hit the mechanical limits of the drivers. If you found a magic driver with really high sensitivity but very short Xmax, you won't get much output compared to something with more Xmax and lower sensitivity.
That works up to a point. If the motor isn't powerful enough to get the cone to Xmax with sensible power inputs, you'll burn the voice coil before you get all of the available output from the drivers.
For what it's worth, the EQ required to sort out a sealed box isn't trivial. The Bag End integrators will have EQ curves that vary according to the signal level. At high volumes, they'll cut back on the EQ boost to try and keep some headroom. At low volumes, they might use loads of boost (30dB+) and get flat to 10Hz.
I used a set of four Beyma 15P1200Nd drivers in sealed boxes for a while. They worked okay for smaller indoor gigs. You could get away with using them for up to 100 people, but you might have to set a highpass as far up as 60Hz in order to stop the amps clipping.
Chris
That Beyma unit driven to Xmax will produce 112.5dB at 40Hz. You might get a little more before it starts sounding really bad, but it'll be somewhere around there.
The sensitivity measurement isn't particularly important in subwoofers - the cabinet has a huge amount of influence over the sensitivity of the finished product.
For instance, in a big sealed box you might get 80dB@1w@20Hz. Make it a tiny sealed box, and it might drop below 70dB@1w@20Hz. A really big tapped horn might be 96dB at 20Hz.
Sensitivity tells you how much power you're going to need before you hit the mechanical limits of the drivers. If you found a magic driver with really high sensitivity but very short Xmax, you won't get much output compared to something with more Xmax and lower sensitivity.
That works up to a point. If the motor isn't powerful enough to get the cone to Xmax with sensible power inputs, you'll burn the voice coil before you get all of the available output from the drivers.
For what it's worth, the EQ required to sort out a sealed box isn't trivial. The Bag End integrators will have EQ curves that vary according to the signal level. At high volumes, they'll cut back on the EQ boost to try and keep some headroom. At low volumes, they might use loads of boost (30dB+) and get flat to 10Hz.
I used a set of four Beyma 15P1200Nd drivers in sealed boxes for a while. They worked okay for smaller indoor gigs. You could get away with using them for up to 100 people, but you might have to set a highpass as far up as 60Hz in order to stop the amps clipping.
Chris
If you can afford the $.... PD is the real deal
I am a big fan of Beyma as company and of their products... They have some great 10, 12 and 15 inch divers, and the TPL... WOW!
But their big drivers are under voice coiled and suffer from high power compression (thermal distortion) and the tend to go too heavy on the Mms and to low power on the motor... Compare the Mms / Bl ratio of the Beyma to the Precision Devices.
I have attached like for like sims comparing the Beyma 18 inch with the Precision Devices 18 inch....
Beyma needs 200 litres (Q of .707) Precision Devices needs 60 litres (Q of .5)
But look at the power compression.... The high SPL's out of the Beyma will sound trashy.
The PD sounds crystal clear and retains texture and detail all the way to full power.
The reliability of PD is legendary and the after sales is 5 star.
The 60 litre cabinets are way easier to move / set up and can be made acoustically dead using 24mm birch ply.
Only down side of PD is the cost...
I am a big fan of Beyma as company and of their products... They have some great 10, 12 and 15 inch divers, and the TPL... WOW!
But their big drivers are under voice coiled and suffer from high power compression (thermal distortion) and the tend to go too heavy on the Mms and to low power on the motor... Compare the Mms / Bl ratio of the Beyma to the Precision Devices.
I have attached like for like sims comparing the Beyma 18 inch with the Precision Devices 18 inch....
Beyma needs 200 litres (Q of .707) Precision Devices needs 60 litres (Q of .5)
But look at the power compression.... The high SPL's out of the Beyma will sound trashy.
The PD sounds crystal clear and retains texture and detail all the way to full power.
The reliability of PD is legendary and the after sales is 5 star.
The 60 litre cabinets are way easier to move / set up and can be made acoustically dead using 24mm birch ply.
Only down side of PD is the cost...
This is incredibly helpful! I know a little about the importance of power compression, esp with sealed boxes, but many manufacturers seems to hide these numbers. It's very had to compare.
I had no idea the Beyma would need that much volume for .707.
With the PD and only 60L, I could even add some frontal area, create push-pull pairs, and still fit four of them in my truck. - But what kind of LF can I get with such a small cab? And doesn't that limit output at 80 Hz as well? - this stuff is very confusing, as many articles talk about Qtc, and higher / lower than .707, but they NEVER explain which is the higher number! Is .5 lower or higher than .707?
I know .5 is critically damped
. I know a smaller box protects the driver better. I know a smaller box has better transient response, or whatever you choose to call that. But there's also a trade-off with OVERALL efficiency (according to most articles, and there are other significant tradeoffs as well.
Unfortunately, every articleI read seems to contradict the last one. SO A SIMPLE QUESTION:
Given my limited frequency needs (no HT) and my overriding, #1 priority of maximum "overall" efficiency (You sort of know what that means) Is the PD still your choice in a 60L enclosure?
I had no idea the Beyma would need that much volume for .707.
With the PD and only 60L, I could even add some frontal area, create push-pull pairs, and still fit four of them in my truck. - But what kind of LF can I get with such a small cab? And doesn't that limit output at 80 Hz as well? - this stuff is very confusing, as many articles talk about Qtc, and higher / lower than .707, but they NEVER explain which is the higher number! Is .5 lower or higher than .707?
I know .5 is critically damped
. I know a smaller box protects the driver better. I know a smaller box has better transient response, or whatever you choose to call that. But there's also a trade-off with OVERALL efficiency (according to most articles, and there are other significant tradeoffs as well.
Unfortunately, every articleI read seems to contradict the last one. SO A SIMPLE QUESTION:
Given my limited frequency needs (no HT) and my overriding, #1 priority of maximum "overall" efficiency (You sort of know what that means) Is the PD still your choice in a 60L enclosure?
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I was afraid of that.
I don't really know what the sensitivity is of the stock Bag End speakers (and they're not going to tell me.) I only know that the finished sub is rated at 96dB @ 80hz, and it's a sealed box with net 3 ft/3. I was assuming that a sealed enclosure's sensitivity was exactly tied to the driver's sensitiviy, since there's no port or horn, and thus hoping to find a really good driver rated for 97 or better.
The more I learn, the more I don't know .....
Now you're just kinda' freaking me out. I believe you, but if this is true, then how does anyone ever use sealed subs with some similar kind of dynamic EQ?
Doing this yourself would likely not be possible for 99.999% of all DIY'ers, so what exactly is everyone doing?
And if I change drivers, but keep using the Bag End integrator, won't I then have completely wrong response? Is this just hopeless?
Bag End indirectly gives the sensitivity of the driver with the four "Maximum Calculated Continuous Acoustic Output" figures on the spec sheet, though the "V" plenum of the S18E cabinet will raise the upper sensitivity by a couple dB over the raw sensitivity of the driver at 80Hz, so it's probably about 94 dB 1w 1 meter.
Interesting that you have been complaining about cabinets with "too much" upper response, but like the sound of yours, which rise at 12 dB per octave, or have bass response (and sensitivity) which drops at 12 dB per octave over the pass band-not much bottom, either way you look at it.
Since the Bag End S18E has only 85 dB sensitivity at 40 Hz, it can easily be exceeded by a great margin in a 5.34 cubic foot (external) cabinet volume. With the current driver driven to 800 watts, maximum output is only 113 dB at 40 Hz.
You could increase the 40Hz output to around 120 dB at 800 watts, a 7 dB increase (about "twice as loud" sounding) by substituting a single "old reliable" LAB12 with a port in your Bag End S18E cabinet. The port could be fit on the driver cover, no modification of the actual cabinet would be needed.
The "V" plenum of the S18E cabinet will raise the upper sensitivity, counteracting the "drooping" upper response in McJerry's LAB 12 simulation- the overall response would be flat.
There are many drivers that could do better, but this should give you an idea of what you are missing.
Cheers,
Art
Attachments
Hydrogen Alex simulation stated:
"110 dB max continuous SPL at 30Hz. 115 dB max continuous SPL at 40Hz."
2 dB more at 40 Hz than the S18E-AD, using 20% more power.
Thermal limit would be around 121 at 80 Hz, about 3dB shy of what you have now.
With a PP plenum, the upper response would be equal, but LF output still quite lame by comparison to something that moves you.
For example, a single XOC1 TH-18 or Keystone sub could put out what four Precision Devices 1851 in 60L sealed cabinets could, using 1/4 the power.
Sealed subs don't get the party going if your #1 priority is "maximum overall efficiency".
Cheers,
Art
The bag end integrator provides 35 dB of boost at 10 Hz relative to 80 Hz, then uses progressive frequency dependent low frequency limiting.
It's not "hopeless" if you like a program dependent "loudness contour", but the EQ won't match another sealed speaker response unless it also drops 35 dB at 10 Hz relative to 80 Hz.
Simple, we manage our expectations.
Sealed boxes are not a good way of getting PA SPLs at low frequencies, unless you're willing to use a lot of cone area. As a result, there aren't many PA speaker manufacturers that make sealed box subwoofers.
Bag End is the exception, but if their subs really did beat all the competition, don't you think other manufacturers would start doing something similar?
FWIW, a ported 15" in a box similar size to these will do 121dB at 40Hz. If you were pushing the sealed boxes to the limits, the ported box would be strolling along. Guess which is going to have less distortion.
Chris
By "hopeless," I meant the amplitude-dependant part, which Chris661 mentioned.
How the heck would a DIY'er implement that, let alone figure out the right curves & such?
(Unless Chris is wrong, or maybe he's just referring to the concealment circuit?)
BTW - How in the world do you know all this stuff, like the specs on that integrator?
I'm looking at the ELF specs right now, and they don't say how much boost. This kind of knowledge is scary. (So who really killed Jimmy Hoffa?
)
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^ See? Stuff like that. Scary.
- And very helpful, thanks.
No, I haven't. I only asked why someone would want a subwoofer with rising response about 100 Hz. (Where most folks don't use it, anyway.) Yes, I know you answered that one, but I'll be dead & buried before I understand your answer.
Sure, but then I could put 4 of them in my truck, and that why this particular thread is ONLY asking about how to maximize my sealed sub system. It may be a useless endeavor, but I'm trying to see how far I can take it. (While still looking hard at other design options)
The advantage of sealed is that I have FOUR 18's on stage. That's a lot of cone area. Also, of course, that transient response. (or phase alignment or whatever you wanna' call it. It's lovely.
The downside is some efficiency loss, a lot of power compression, (I think) and theoretically more distortion than either a BR or a horn design.
It's a clever idea. But again, not the subject of this thread. If I end up with a BR design, it will be either three 2X12" PPSL, or (because of specific, preferred cabinet dimensions) three 4x10" PPSL.
- But that discussion is for another day.As is my idea to build two Keystone subs and then cut them in half, so they're more portable.
- And yes, I'm actually seriously considering this.
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Rod Elliot is one of the most respected and experienced electronic and acoustic engineers.... Over 20 years of proven success and here is a link to his
"big driver / small box / kick *** performance"
Sub-Woofer Controller
Rod has built and tested more speakers and subs than most and after trying all the usual ported / Transmission Line / passive radiator designs here are some of his conclusions on the BDSSB (Big driver Small Sealed Box) design:
"Overall, I would have to say that I doubt that any conventional design would be as compact, or would have such clarity and solidarity. Being a sealed box, there is none of the "waffle" that ported designs often give, and the speaker is protected against excessive excursion by the air pressure in the box itself (below the cutoff frequency, anyway).
The bottom end in my system is now staggering. It is rock solid, and absolutely thunders when called upon. The 400W amp is more than sufficient for the job, considering it has to keep up with a biamped main system capable of very high SPL (up to 120dB at my listening position). In fact a quick test indicates that 200W would have been enough (but ... better to have it and not need it than need it and not have it).
Given the performance, I would never consider a conventional sub again, ..."
Now imagine how much better your results will be with the 18 inch PD flagship driver Vs the basic 15 inch driver he used...!
"big driver / small box / kick *** performance"
Sub-Woofer Controller
Rod has built and tested more speakers and subs than most and after trying all the usual ported / Transmission Line / passive radiator designs here are some of his conclusions on the BDSSB (Big driver Small Sealed Box) design:
"Overall, I would have to say that I doubt that any conventional design would be as compact, or would have such clarity and solidarity. Being a sealed box, there is none of the "waffle" that ported designs often give, and the speaker is protected against excessive excursion by the air pressure in the box itself (below the cutoff frequency, anyway).
The bottom end in my system is now staggering. It is rock solid, and absolutely thunders when called upon. The 400W amp is more than sufficient for the job, considering it has to keep up with a biamped main system capable of very high SPL (up to 120dB at my listening position). In fact a quick test indicates that 200W would have been enough (but ... better to have it and not need it than need it and not have it).
Given the performance, I would never consider a conventional sub again, ..."
Now imagine how much better your results will be with the 18 inch PD flagship driver Vs the basic 15 inch driver he used...!
The maths behind the truth
In the above link Rod Elliot explains the real world build / performance / results / sound quality.
The attached PDF by another top acoustic engineer explains the maths / physics and biology (human ear brain function) of why sealed box is the only way to produce accurate sound.... Also the flip side why all ported / transmission line / passive radiator designs are fundamentally flawed and unfit for purpose.....
These facts are very unpopular as many DIY guys are old school and have been brought up on ported / TL designs.... The truth hurts!
Also the vast majority of commercial loudspeaker designs and DIY vendors rely on ports / delayed resonance to "enhance" the bass.... Never mind the quality feel width!
So you wont find much support for sealed box designs.
In the above link Rod Elliot explains the real world build / performance / results / sound quality.
The attached PDF by another top acoustic engineer explains the maths / physics and biology (human ear brain function) of why sealed box is the only way to produce accurate sound.... Also the flip side why all ported / transmission line / passive radiator designs are fundamentally flawed and unfit for purpose.....
These facts are very unpopular as many DIY guys are old school and have been brought up on ported / TL designs.... The truth hurts!
Also the vast majority of commercial loudspeaker designs and DIY vendors rely on ports / delayed resonance to "enhance" the bass.... Never mind the quality feel width!
So you wont find much support for sealed box designs.
Alex,
While I have the utmost respect for Rod's work, we're talking about PA systems here. A 15" driver in a sealed box does not work for PA use. I know this, because I tried to make it work for a couple of years. Four of them, and you can get by in smaller venues. Put those same drivers (driven by the same amplifier) in ported boxes, and you can have a fairly serious outdoor party for a couple of hundred people.
The difference is not subtle: there's around 10dB difference in output at 40Hz for the same power input. As a result, the sealed boxes would be at the limiters while the ported box is seeing 1/10th the power and keeping up just fine.
Chris
While I have the utmost respect for Rod's work, we're talking about PA systems here. A 15" driver in a sealed box does not work for PA use. I know this, because I tried to make it work for a couple of years. Four of them, and you can get by in smaller venues. Put those same drivers (driven by the same amplifier) in ported boxes, and you can have a fairly serious outdoor party for a couple of hundred people.
The difference is not subtle: there's around 10dB difference in output at 40Hz for the same power input. As a result, the sealed boxes would be at the limiters while the ported box is seeing 1/10th the power and keeping up just fine.
Chris
My point exactly..."not subtle: there's around 10dB difference"
You do know Rod has been playing live and building PA's for over 30 years....?
Also worth pointing out a few other errors in your post...
(1)"... I know this, because I tried to make it work for a couple of years..."
With all due respect Chris, just because you failed does not mean others make the same mistakes.... Rod's CV (design skills, experience and commercial success) are in a different league from yours.
As far as John Watkinsons paper goes.... Feel free to comment on the pertinent facts (Time domain, HAS, air pressure events ETC)
(2) "The difference is not subtle: there's around 10dB difference in output at 40Hz for the same power input...."
Exactly as I described in my previous posts... " Never mind the quality feel the width!"
I have linked to and posted solid data and proven designs from two highly regarded international designers .... Peer reviewed data.
So again with all due respect your comeback of " well I tried and failed and found it was louder with a port...." Really doesn't cut it as a scientific counter point that can help the OP make an informed decision.
Nothing personal Chris, I am only presenting facts.
You do know Rod has been playing live and building PA's for over 30 years....?
Also worth pointing out a few other errors in your post...
(1)"... I know this, because I tried to make it work for a couple of years..."
With all due respect Chris, just because you failed does not mean others make the same mistakes.... Rod's CV (design skills, experience and commercial success) are in a different league from yours.
As far as John Watkinsons paper goes.... Feel free to comment on the pertinent facts (Time domain, HAS, air pressure events ETC)
(2) "The difference is not subtle: there's around 10dB difference in output at 40Hz for the same power input...."
Exactly as I described in my previous posts... " Never mind the quality feel the width!"
I have linked to and posted solid data and proven designs from two highly regarded international designers .... Peer reviewed data.
So again with all due respect your comeback of " well I tried and failed and found it was louder with a port...." Really doesn't cut it as a scientific counter point that can help the OP make an informed decision.
Nothing personal Chris, I am only presenting facts.
For PA use, I'd bet the few dozen to hundreds to thousands of partygoers, etc. in the audience couldn't care less about most of that. Clear relatively undistorted (THD) output is key, followed by how much it would take to reproduce that, followed by everything else.
That paper seems to reference what we would need if I have to say reproduce the sound of walking T-Rex realistically enough so if I close my eyes, I can pinpoint were it is in my room. Probably relevant to 0.01% of the people in this forum looking for advice.
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Answers based on facts ... Not opinion based on bias
As you sell good old ported subs / delayed resonance subs for a living you have to jump to defend your products.... Sadly such blatant commercial bias is common.
Choosing to keep your head in the sand does not change the facts.
If you can present any peer reviewed evidence to prove Rod Elliot or John Watkinson is wrongs feel free....
As you sell good old ported subs / delayed resonance subs for a living you have to jump to defend your products.... Sadly such blatant commercial bias is common.
Choosing to keep your head in the sand does not change the facts.
If you can present any peer reviewed evidence to prove Rod Elliot or John Watkinson is wrongs feel free....
LOL - I don't sell any subs for a living. I make my living in IT. I have ZERO to gain from any input I provide here, apart from the satisfaction of helping someone to achieve what they want to achieve with their project.
BTW - Hands up all the DJs or PA system providers here who have ever had a customer come up to you and say that "can you fix the time domain issue please?" as opposed to something like "turn it up the bass - it needs to be louder!"
Goodness me.
You realise the system he puts forward in your link isn't intended for PA use, right?
The fact of the matter is this: a ported subwoofer will get louder than a sealed subwoofer, over a narrower bandwidth.
When it comes to PA systems, where going down to 35Hz or so will cover 99% of gigs, the narrower bandwidth is fine, and the increased SPL is exactly what's needed.
Note at the end of Rod's article: "I measured 80dB SPL at 1 metre in my workshop (sub-woofer perched on a stool in more or less the centre of the space) with at 25Hz and 70W"
That works out as one inefficient box. Drop 700w in there and you'll get 90dB before the driver burns up. That just isn't worth having at a gig - I can raise my voice to that level.
With regards to my own use of sealed boxes, I think perhaps you're missing an important point: I've actually tried using sealed subwoofers in a PA system.
I did similar things to Rod, except I applied an EQ curve that allowed them to work over a wider bandwidth. I used better drivers and more power, too.
My observation about sealed subwoofers in PA situations is this - you better have an awful lot of them.
The biggest gigs I do use 8x 15"s in ported boxes. They each get around a kilowatt at full power. If you wanted to match those 8x 15"s with sealed boxes, you'll need around 24x 15" drivers. Never mind the quality, that's literally just to make sure they're heard. Now, each of those 15"s will probably also require a kilowatt per driver. Suddenly, your power requirements have tripled. More amplifiers, bigger power distro, bigger generator. Your running costs have gone up, and your load-in/out times have also gone up on account of having to move all of those boxes. Next up, I hope you've got some really good software to figure out how to position those 24 boxes, because a pile of subs that big is going to start to have some interesting directionality.
So, I cannot allow myself or anyone else to recommend sealed boxes for a PA system in good conscience, unless they are fully prepared to use a lot of speakers, with all the compromises that would entail.
When it comes to absolute quality, I believe an infinite baffle system is the way to do it. Small sealed boxes are incredibly inefficient, which means lots of power and therefore lots of distortion from flux modulation and the like.
Absolute quality, despite what the manufacturers might have you believe, is not what is required of a PA system. The requirements of a PA system is to deliver acceptable sound to the entire audience. Sealed boxes can do that, but, as I said earlier, you'll need a lot of them.
Chris
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