Let's say ''unlimited amplifier power''... Limited enclosure volume (relatively)... For Maximum output between 28-35z (and up), which one would you choose?
A) Sealed box, Single 500cc Vd driver, EQ boost.
B) Passive radiator, Single 500cc Vd driver, EQ boost
C) 4th order bandpass, Single 500cc Vd driver, EQ boost
D) Sealed box 60-75% volume for ea.: Dual 500cc Vd drivers (total 1000cc), EQ boost
Basically the question is: will 2 drivers give higher output -at these very low frequencies- if the volume per driver is limited... V.S. B) and C)
(obviously A) is the loser here... just for reference purpose)
Also, i'm not so sure about the EQ boost effect/relevance on B and C... Is the driver won't reach the Xmax anyway, ''naturally'' without signal cheat?
A) Sealed box, Single 500cc Vd driver, EQ boost.
B) Passive radiator, Single 500cc Vd driver, EQ boost
C) 4th order bandpass, Single 500cc Vd driver, EQ boost
D) Sealed box 60-75% volume for ea.: Dual 500cc Vd drivers (total 1000cc), EQ boost
Basically the question is: will 2 drivers give higher output -at these very low frequencies- if the volume per driver is limited... V.S. B) and C)
(obviously A) is the loser here... just for reference purpose)
Also, i'm not so sure about the EQ boost effect/relevance on B and C... Is the driver won't reach the Xmax anyway, ''naturally'' without signal cheat?
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With unlimited power, the double sealed unit can reach xmax regardless of box size, and it will have 6db more output than the single sealed box.
The question is then, can you beat the sealed box's efficiency by 6db with a different alignment?
The answer is definitely yes, but the question then becomes how big of a cabinet are you willing to allow to beat that efficiency.
Past a certain cabinet size, higher order alignments will always win out on output, it's just a matter of at what cabinet size it would take to beat two sealed boxes.
Personally, if I want high output and small cabinet size, I go for 6th order parallel bandpass. You can achieve the efficiency of a tapped horn with a smaller cabinet, but in exchange you usually sacrifice bandwidth. You didn't specify how much bandwidth you need, so that would affect your decision as well.
The question is then, can you beat the sealed box's efficiency by 6db with a different alignment?
The answer is definitely yes, but the question then becomes how big of a cabinet are you willing to allow to beat that efficiency.
Past a certain cabinet size, higher order alignments will always win out on output, it's just a matter of at what cabinet size it would take to beat two sealed boxes.
Personally, if I want high output and small cabinet size, I go for 6th order parallel bandpass. You can achieve the efficiency of a tapped horn with a smaller cabinet, but in exchange you usually sacrifice bandwidth. You didn't specify how much bandwidth you need, so that would affect your decision as well.
Ballpark figure for enclosure volume? Criteria of width, depth or height?
40-60L, 60-90L, 90-120L, 120-160L or 160-220L?
Just SPL or do you consider group delay and phase response?
Seems you're talking about 12" drivers here.
Edit:
Added a classic ca 90 liter BR just for fun. 110db in halfspace at 25hz ok or do you need more?
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Is it a given enclosure size that is the limit?
Or does it have to use 500cc Vd drivers?
I spent some time with a question that is quite similar to yours.
How to maximize output from an 18L box in my car?
These are my thoughts:
I use an Alpine Type R 10" sub in my car. 20mm Xmax in a sealed 18L box. Sounds great and is loud enough in most cases.
I tested a 8" sub (15mm Xmax 500W) with two 10" beefy passive radiators and they are in simulations slightly louder down low. I have 2kW available, basically unlimited for any of these subs.
Testing revealed that the passive radiators werent ideal with high output. The sealed enclosure is simply Xmax limited. So the differences in the car arent as big as in the simulation. TS parameters are so way off at full power that a passive radiator box has to be designed with full power in mind and then it becomes peaky at low levels when Bl is too high, Re too low and so on.
Another problem can be the size of the box. Sub+passive radiators simply wont fit all box shapes. If you intend to maximize output from a given enclosure size passive radiators will take up a lot of space.
Unlimited amplifier power also has a problem. A sub in a sealed box can almost always be driven to Xmax without thermal issues. Not so easy with passive radiators. A smaller sub with passive radiators will have to handle a lot of power to beat the sealed box output.
In my mind the more exotic horns, bandpass and so on are great for extracting maximum SPL from a given subwoofer, but not from a given enclosure size. Hoffman dictates that efficiency will increase in a big enclosure, but not power handling.
Passive radiators can be the best solution if the enclosure is thin with a large baffle and rear panel. Then huge passive radiators and subs can fit in a relatively small box.
Small enclosures become difficult with ports and passive radiators when the subs have 20mm Xmax and you intend to use it...
Or does it have to use 500cc Vd drivers?
I spent some time with a question that is quite similar to yours.
How to maximize output from an 18L box in my car?
These are my thoughts:
I use an Alpine Type R 10" sub in my car. 20mm Xmax in a sealed 18L box. Sounds great and is loud enough in most cases.
I tested a 8" sub (15mm Xmax 500W) with two 10" beefy passive radiators and they are in simulations slightly louder down low. I have 2kW available, basically unlimited for any of these subs.
Testing revealed that the passive radiators werent ideal with high output. The sealed enclosure is simply Xmax limited. So the differences in the car arent as big as in the simulation. TS parameters are so way off at full power that a passive radiator box has to be designed with full power in mind and then it becomes peaky at low levels when Bl is too high, Re too low and so on.
Another problem can be the size of the box. Sub+passive radiators simply wont fit all box shapes. If you intend to maximize output from a given enclosure size passive radiators will take up a lot of space.
Unlimited amplifier power also has a problem. A sub in a sealed box can almost always be driven to Xmax without thermal issues. Not so easy with passive radiators. A smaller sub with passive radiators will have to handle a lot of power to beat the sealed box output.
In my mind the more exotic horns, bandpass and so on are great for extracting maximum SPL from a given subwoofer, but not from a given enclosure size. Hoffman dictates that efficiency will increase in a big enclosure, but not power handling.
Passive radiators can be the best solution if the enclosure is thin with a large baffle and rear panel. Then huge passive radiators and subs can fit in a relatively small box.
Small enclosures become difficult with ports and passive radiators when the subs have 20mm Xmax and you intend to use it...
D option would be the maximum size for the cabinet. So if a given driver requires 30 liters, option D will have 50 liters maximum for the two drivers and most likely just 40-45 liters...
What i'm afraid of is the dual drivers config will have a higher F3, therefore the 6db gain might be translated into a 2-3db @ 28-35hz...
On the other hand, it's already space-limited for single driver in a 4th order cabinet, i can't imagine how it would be possible to have a 6th order one...
Undecided yet, but it will be between 35 and 55 liters. Hopefully closer to 35 liters!
The real goal is to have higher output than a CM9 S2, which is -to my great surprise- very capable...
Thank you Johnny for the feedback. That is what i needed: some comments out-of-simulations... Sims are great but don't tell the whole story.
According to the experimentations i did so far, the true limiting factor is the Xmax w/ low frequency response goal. 40-50hz doesnt seem to be a problem at all in a sealed enclosure of this size, but as soon as it drops to a goal of 28-35hz, then Xmax is reached without any decent output (i'm talking 96-102db max with room gain, anywhere from 2-4 meters mic position) CM9 S2 (dual 6.5'' BR) is capable of 100-105db in the same context...
The sensitivity will perhaps only be 2-3dB higher, but that means the excursion will be less. Compensate with power to get full excursion and 6dB. Distortion will increase though.
Of course there is a limit to how small the enclosure can be. If you are at the limit with one woofer in 30L and go for two woofers in 45L it wont work very well at all.
The CM9 S2 may be well designed, but I highly doubt it cant be beaten.
30L can give you two beefy 8" subs (or one 10") ported to 30Hz with a 4" port or a couple of 12" beefy passive radiators. 1000W or so should give you decent output while staying within Xmax.
I think that should beat the CM9 S2 by at least 6dB.
I'm under the impression that Xmax is the major bottleneck here, not power handling (voice coil, thermal), will have to measure with a wattmeter but it looks like most of the ''common'' drivers with ''normal'' Xmax (8-14mm) are bottoming out way before their respective rated power handling. Probably the Xmech must be considered closely at this point where pistonic capacities is very stressed...
Edit: if that is so, then ''unlimited power amplifier'' is of no help, at all. Only Vd would be important.
Edit: if that is so, then ''unlimited power amplifier'' is of no help, at all. Only Vd would be important.
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FYI: i'm using this for the testing at this moment, which is some pulsated pure tones. A little more forgiving than pure tones...
25hz...30hz...35hz.. and so on.
Also have the pure tones to test in-between: 27hz...28hz...29hz...
25hz...30hz...35hz.. and so on.
Also have the pure tones to test in-between: 27hz...28hz...29hz...
An externally hosted image should be here but it was not working when we last tested it.
At 28-35Hz I agree that excursion will be the issue for sealed boxes. And to a less degree also for passive radiators.
With regards to xmax and xmech, it depends on the driver. Some driver wont go much further than xmax before bottoming out, others can add 50% to that number without even sounding bad.
With regards to xmax and xmech, it depends on the driver. Some driver wont go much further than xmax before bottoming out, others can add 50% to that number without even sounding bad.
More exotic alignments have a possibility to be louder for a given enclosure size and frequency, if they are of a higher order. Higher order usually also means more resonant.
Port is a bit small. Hard to find suitable 8"s, might find some 2 x 6.5"s. Better to go up to a 10" and 55 liters.
This is in halfspace as usual.
Edit:
Can certainly understand the request for anything else than a BR box, but at this size, and with these design criteria, it will be really hard to get it right no matter which path you choose. A chuffing port will at least allow the drivers to cool down a bit.
Edit2:
Arent the CM9 S2 more like 55 liters?
Edit3:
A single Peerless SLS 12" can get there in 55 liters.
Peerless by Tymphany 830669 12"
This is in halfspace as usual.
Edit:
Can certainly understand the request for anything else than a BR box, but at this size, and with these design criteria, it will be really hard to get it right no matter which path you choose. A chuffing port will at least allow the drivers to cool down a bit.
Edit2:
Arent the CM9 S2 more like 55 liters?
Edit3:
A single Peerless SLS 12" can get there in 55 liters.
Peerless by Tymphany 830669 12"
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There is really no free lunch at all, isnt it?
damn, i should learn that once for good
Some things we never learn.
It's just those cycles under 30 that are really expensive in terms of volume, this is why PA just stopped caring about stuff below 40hz, it's space and weight.
If you settle for 30hz I can probably find some reasonably priced 10" that can do 110db halfspace at under 60 liters, hopefully with little to no chuffing.
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Yes, exactly. And downright useless outdoor as well...
Problem is: i really nailed down my objective to 28-35hz. At first i wanted something perfectly flat starting from 22-25hz but that is just unrealistic considering space & budget for this project.
NOW i realize how spoiled i am with my main system at home with EQ-boosted-to-death 4x 10W7's in small sealed boxes...
So what is the budget?
Some decent passive radiators cost a little bit as well.
Just trying out the Dayton Audio DCS255-4 a bit. you get 110db in halfspace flat down to acoustic impedance peak at 32hz. 51 liters
I really get the 28hz thing, but it's 26hz or bust in my book. Not at 110db in 51 liters though.
Kaffimann:
Arent the CM9 S2 more like 55 liters?
for what i see, it looks like 35 liters MAXIMUM (internal net), unless they cheated with an extension behind the FST...
anyway, B&W did a good job on that one.
I'll order a pair of Klipsch RF-82 II as well, for benchmarking, because that's another ''cheap'' commercial speakers that are impressive, sub-bass wise...
http://www.klipsch.ca/products/rf-82-ii-floorstanding-speaker
Also i noticed a lot of commercial products nowadays using passive rads. It seems to be THE way to get lowest possible response at max output...in a small volume.
Arent the CM9 S2 more like 55 liters?
for what i see, it looks like 35 liters MAXIMUM (internal net), unless they cheated with an extension behind the FST...
anyway, B&W did a good job on that one.
I'll order a pair of Klipsch RF-82 II as well, for benchmarking, because that's another ''cheap'' commercial speakers that are impressive, sub-bass wise...
http://www.klipsch.ca/products/rf-82-ii-floorstanding-speaker
Also i noticed a lot of commercial products nowadays using passive rads. It seems to be THE way to get lowest possible response at max output...in a small volume.
If i can beat the CM9 by 3db (anywhere starting from 28hz) i'll be satisfied. Even if that requires double or triple power. But that is the problem: power is not a problem solver in my case...
Yes you are right: passive rads are costly, at least the good ones. Maybe the best solution is the one that big companies are choosing: dual sub/woofers for more Vd and 3db gain from acoustic coupling... I mean, they're not big companies for no reason
In my experience that is a too simple statement to make. While I down want to hang you out to dry, I do wish you could back it up with your experiences.
In the 90s I built a lot of bandpass boxes, convinced that they would be louder. Later I realized that they simply werent. Then I went on to horns...
I have simulated a lot of horns, tapped horns, bandpass, built too many of them, and my opinion is still that you can get high efficiency, but overall output is difficult. At least over any reasonable bandwidth. I had a 200x50x120cm FLH in my living room for a while. Very interesting sound from it, felt massive. But the two 60L bass reflex boxes that replaced it was louder, even if it felt counter-intuitive. They could take more power and that made the difference.
I would love to see any realistic simulations or IRL measurements where a high Xmax, high power handling subwoofer in bass reflex is outperformed by something more exotic of similar size enclosure.
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