Seconded... the air inside the boxes get hot after a few hours, eventually the pole piece glue fails trapping the voice coil. A ported box is easy to build with basic tools and is sometimes a better choice than TH (compact, low tuned boxes).
Thanks Chris,
There are 3 good reasons I prefer sealed box bass both at home and for live sound.
(1) Small size of individual subs... WAF at home and ease of transport, handling and setting up at gigs. I used to crew for a Jazz Funk band (JALN band) and I could easily stack as many subs as the ceiling height/stage allowed and then attach (huge wing nuts!) front-loaded horns onto each sub cabinet... We got rapid line array bass stacks with massive throw hitting 125dB averaged out over crowds of 500 to 1,000. The sound was legendary with sound "better than Earth Wind and Fire" reviews!
(2) Flexibility... Multi sub / distributed sub, line array or main stack, having the choice is a great benefit and reliability... A "tank" of a 24mm birch ply sealed box is the strongest portable ( with one strong guy) option.
(3) Sealed box with or without front-loaded horns have the best time response / step response (CSD plots) and its instantly recognisable when you hear that super tight accurate bass and low midrange. All delayed resonance / back loaded horns / ported / transmission lines suffer from muddy / distorted bass low mids when compared to sealed box.
"Quality over quantity" for me every time!
There are 3 good reasons I prefer sealed box bass both at home and for live sound.
(1) Small size of individual subs... WAF at home and ease of transport, handling and setting up at gigs. I used to crew for a Jazz Funk band (JALN band) and I could easily stack as many subs as the ceiling height/stage allowed and then attach (huge wing nuts!) front-loaded horns onto each sub cabinet... We got rapid line array bass stacks with massive throw hitting 125dB averaged out over crowds of 500 to 1,000. The sound was legendary with sound "better than Earth Wind and Fire" reviews!
(2) Flexibility... Multi sub / distributed sub, line array or main stack, having the choice is a great benefit and reliability... A "tank" of a 24mm birch ply sealed box is the strongest portable ( with one strong guy) option.
(3) Sealed box with or without front-loaded horns have the best time response / step response (CSD plots) and its instantly recognisable when you hear that super tight accurate bass and low midrange. All delayed resonance / back loaded horns / ported / transmission lines suffer from muddy / distorted bass low mids when compared to sealed box.
"Quality over quantity" for me every time!
Hey Arcgotic,
Today I use Precision Devices, 15 inch at home, I am too old to carry heavy subs anymore!
The attached sims give you a good indication of what they do with active amplifification and Eq.
Back in the day I think the JALN guys used PD, but it might have been Beyma, I cant remember as it was over 30 years ago!
Cheers
A.
Today I use Precision Devices, 15 inch at home, I am too old to carry heavy subs anymore!
The attached sims give you a good indication of what they do with active amplifification and Eq.
Back in the day I think the JALN guys used PD, but it might have been Beyma, I cant remember as it was over 30 years ago!
Cheers
A.
If you aren't worried about grills for punters, you can reverse the driver. Best of both.
Interesting point, if you manage to seal your subs well enough, with the air temp increase you'd see asymmetric driver displacement on suspension (due to air density increase) alongside the power compression. Think that's nearly impossible with time taken to get to temperature and construction methods.
Having said that, I faintly remember a PA manufacturer stating they ensure there is a high impedance hole or leak in their FLH designs to prevent this..
Interesting point, if you manage to seal your subs well enough, with the air temp increase you'd see asymmetric driver displacement on suspension (due to air density increase) alongside the power compression. Think that's nearly impossible with time taken to get to temperature and construction methods.
Having said that, I faintly remember a PA manufacturer stating they ensure there is a high impedance hole or leak in their FLH designs to prevent this..
No sealed box is so well sealed that you need to have such a pin hole. This is quite easy to test just connect a lab power supply to it and put about 9V DC across the woofer. You will see the cone jump and then slowly move further as the pressure equalizes over the course of seconds inside the box. Obviously don't do it too long to avoid burning the woofer out.
Magnet out should work fine for PA if you have enough amp power and can protect the amp (and speaker terminals - they are going to be at potentially lethal voltages).
Magnet out should work fine for PA if you have enough amp power and can protect the amp (and speaker terminals - they are going to be at potentially lethal voltages).
While I see your point, the ported designs I used to replace my sealed box subs had a 3:1 performance ratio: you needed 3x sealed subs to match 1x ported.
So, 3KW of amplifier, 3x high-end 15"s in sealed boxes, extra cables, mains power etc etc to match 1KW into 1x high-end 15" in a ported box.
If I had infinite money and mains power, sealed boxes would be fun for sure.
I have neither of those, and have found that ported boxes get much more output from the same driver/amplifier complement.
I set off using 4x sealed 15"s in small-ish indoor venues (maybe 100 cap working men's club) and having to keep a very close eye on things, to using 4x ported 15"s and having plenty of bottom-end grunt for medium-sized outdoor venues (a few hundred people outdoors was fine), and headroom to push things further if the organiser wanted it.
IMO, it's not even a comparison.
Chris
For sure, if you want the lowest cost "room-filling sound" for 100 guys in your local working men's club use ported / TH / TM L/ delayed resonance to give them quantity not quality... Good and loud for the humble fees these guys pay for PA... That is how 99% of the public get their "live sound" experience and it becomes the "reference"
That is a very different scenario from reproducing the best sound for home/studio / live sound "unplugged" events.
If you are reproducing upright bass / Cello/piano / male vocal etc it falls apart on anything other than sealed box/stacked line array.
It all comes down to giving the audience what the want and for 99% of audiences they will never experience high end bass and low midrange so they simply dont miss it and are happy to go home with their ears ringing from high SPL out of phase muck... Sad but true!
That is a very different scenario from reproducing the best sound for home/studio / live sound "unplugged" events.
If you are reproducing upright bass / Cello/piano / male vocal etc it falls apart on anything other than sealed box/stacked line array.
It all comes down to giving the audience what the want and for 99% of audiences they will never experience high end bass and low midrange so they simply dont miss it and are happy to go home with their ears ringing from high SPL out of phase muck... Sad but true!
Well, if you're happy with using a big pile of sealed boxes, then more power to you.
For a while, I ran 8x ported 15"s on a Crown MA12000i.
If I wanted to convert to sealed boxes and be able to provide sound for the same size venues, I'd need:
- Another 2x Crown MA12000i
- Another 16x drivers, at around £300 each.
That's a lot of cash - well into five figures - and we haven't bought any wood or hardware yet.
... Nor have we figured out how to power a rack with three of those Crown amps in. It'll be a large generator, for sure: something with a 32A 3-phase output would probably suffice.
For kicks, I ran a simulation using Hornresp, and it went like this:
- High power 12", modelled in two different boxes. One was ported, and the other was sealed.
- EQ'd the sealed box to match the ported box in terms of frequency response (ie, flat to 40Hz, dropping quickly below that). They deviated by less than 1dB across the range, so we're comparing apples to apples here.
The results went as follows:
- The group delay curves matched perfectly above 55Hz. At 40Hz, the ported box had 25ms of group delay, while the EQ'd sealed box had 22.5ms.
- The in-band cone excursion of the ported box hit 8mm one-way at 60Hz. For the sealed box, it's 38mm at 40Hz.
When you consider the RT60 of a typical venue, the situation gets worse: there's no way the 2.5ms difference in those two setups will be noticed compared to the hundreds-of-ms decay time of a typical room.
The difference in harmonic distortion (assuming one-to-one cabinet comparison) will be noticed immediately.
In conclusion, then, sealed boxes offer a tiny (arguably inaudible in most venues) improvement in time-domain performance, at the expense of exceptionally high cost, crazy numbers of cabinets and huge electrical demands.
There's no way I could recommend sealed boxes for a sound reinforcement role.
Chris
For a while, I ran 8x ported 15"s on a Crown MA12000i.
If I wanted to convert to sealed boxes and be able to provide sound for the same size venues, I'd need:
- Another 2x Crown MA12000i
- Another 16x drivers, at around £300 each.
That's a lot of cash - well into five figures - and we haven't bought any wood or hardware yet.
... Nor have we figured out how to power a rack with three of those Crown amps in. It'll be a large generator, for sure: something with a 32A 3-phase output would probably suffice.
For kicks, I ran a simulation using Hornresp, and it went like this:
- High power 12", modelled in two different boxes. One was ported, and the other was sealed.
- EQ'd the sealed box to match the ported box in terms of frequency response (ie, flat to 40Hz, dropping quickly below that). They deviated by less than 1dB across the range, so we're comparing apples to apples here.
The results went as follows:
- The group delay curves matched perfectly above 55Hz. At 40Hz, the ported box had 25ms of group delay, while the EQ'd sealed box had 22.5ms.
- The in-band cone excursion of the ported box hit 8mm one-way at 60Hz. For the sealed box, it's 38mm at 40Hz.
When you consider the RT60 of a typical venue, the situation gets worse: there's no way the 2.5ms difference in those two setups will be noticed compared to the hundreds-of-ms decay time of a typical room.
The difference in harmonic distortion (assuming one-to-one cabinet comparison) will be noticed immediately.
In conclusion, then, sealed boxes offer a tiny (arguably inaudible in most venues) improvement in time-domain performance, at the expense of exceptionally high cost, crazy numbers of cabinets and huge electrical demands.
There's no way I could recommend sealed boxes for a sound reinforcement role.
Chris
Chris,
You have missed my point,"quantity over quality".
Just because you (or most PA hire firms) cant make money out of reproducing accurate sound in commercial venues, does not change the physics of time-domain accurate sound reproduction.
Re your sim... Your sim results, or any sim results, are totally dependent on the driver used... 99% of Pro drivers are designed for ported/TH/TL/ delayed resonance systems...
So unless you know what TS parameters and mechanical properties are best suited to sealed box / DSP Eq loading (without DSP sealed box does not work) you can't make it work... As you clearly demonstrated, running a sim in both sealed and ported using the same driver will never work... This classic mistake has been repeated consistently by mainstream PA/home loudspeaker designers since the 1920s.
Compared to the "big picture" of NASA/science and real-world engineering, loudspeaker design is a tiny irrelevant backwater, so few physicists are attracted to the niche, but here is a link which explains some of the theory in a bit more detail.
Acoustical Reality — Manger Audio
Also, more here by renown audio designer and physicist John Watkinson, We need to talk about SPEAKERS: Sorry, 'audiophiles', only IT will break the sound barrier • The Register
Enjoy!
You have missed my point,"quantity over quality".
Just because you (or most PA hire firms) cant make money out of reproducing accurate sound in commercial venues, does not change the physics of time-domain accurate sound reproduction.
Re your sim... Your sim results, or any sim results, are totally dependent on the driver used... 99% of Pro drivers are designed for ported/TH/TL/ delayed resonance systems...
So unless you know what TS parameters and mechanical properties are best suited to sealed box / DSP Eq loading (without DSP sealed box does not work) you can't make it work... As you clearly demonstrated, running a sim in both sealed and ported using the same driver will never work... This classic mistake has been repeated consistently by mainstream PA/home loudspeaker designers since the 1920s.
Compared to the "big picture" of NASA/science and real-world engineering, loudspeaker design is a tiny irrelevant backwater, so few physicists are attracted to the niche, but here is a link which explains some of the theory in a bit more detail.
Acoustical Reality — Manger Audio
Also, more here by renown audio designer and physicist John Watkinson, We need to talk about SPEAKERS: Sorry, 'audiophiles', only IT will break the sound barrier • The Register
Enjoy!
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International audio designer explains how sealed box subs work
Sub-Woofer Controller
Rod Elliot has been designing, manufacturing and selling commercial audio (PA, musical instrument gear and home HiFi) since 1980 and 20 years ago as amplifier power became cheaper and living room space became more expensive he designed a solution to the huge ported / TH subs that were the norm at that time.
The link above explains the design theory, the build process and the sonic advantages... Some of the subjective benefits include:
" Given the performance, I would never consider a conventional sub again..."
" 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)...
" All in all, I feel it is unlikely that anything other than an isobaric enclosure could give the same performance for a box size even close to the EAS box, and even then would be limited to about 35Hz. Added to this is the rather unpredictable combined response of the main speakers and the sub, which is not an issue with this design. With an EAS system, more power is needed than a conventional design, but for many people, power is much cheaper than space."
In closing, I would suggest that the 3 references I have provided (Prof, Joseph Manger, John Watkinson and Rod Elliot) are all internationally respected authorities on the subject and are qualified and experienced in the art of accurate sound reproduction.
Whilst my opinion or your opinion may not carry the same weight, we all have a right to express our opinion, so whilst I respect your opinion I must respectfully disagree with it!
Sub-Woofer Controller
Rod Elliot has been designing, manufacturing and selling commercial audio (PA, musical instrument gear and home HiFi) since 1980 and 20 years ago as amplifier power became cheaper and living room space became more expensive he designed a solution to the huge ported / TH subs that were the norm at that time.
The link above explains the design theory, the build process and the sonic advantages... Some of the subjective benefits include:
" Given the performance, I would never consider a conventional sub again..."
" 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)...
" All in all, I feel it is unlikely that anything other than an isobaric enclosure could give the same performance for a box size even close to the EAS box, and even then would be limited to about 35Hz. Added to this is the rather unpredictable combined response of the main speakers and the sub, which is not an issue with this design. With an EAS system, more power is needed than a conventional design, but for many people, power is much cheaper than space."
In closing, I would suggest that the 3 references I have provided (Prof, Joseph Manger, John Watkinson and Rod Elliot) are all internationally respected authorities on the subject and are qualified and experienced in the art of accurate sound reproduction.
Whilst my opinion or your opinion may not carry the same weight, we all have a right to express our opinion, so whilst I respect your opinion I must respectfully disagree with it!
wow...now i'm even more confused....
where does Mr Elliot mention using this for live sound application?
what Manger products are widely used for pro Pa?
and while i recognize John Watkinson's name in connection with audio visual systems to my knowledge he's not a live sound enginneer or is he?
where does Mr Elliot mention using this for live sound application?
what Manger products are widely used for pro Pa?
and while i recognize John Watkinson's name in connection with audio visual systems to my knowledge he's not a live sound enginneer or is he?
Well, it's lucky that I have a degree in Physics, then.
In theory, yes, sealed boxes can offer good performance when ultimate SPL isn't a concern.
In practice, ultimate SPL is THE concern for a subwoofer like the OTH40C which, I'd like to remind you, is the subject of this thread.
Having had a look at the Magner paper, the problem they're showing with the impulse responses is nothing to do with the sealed/ported/whatever boxes, and entirely to do with phase lags due to a passive crossover.
Modern FIR-processed systems are capable of being impulse-perfect, reproducing square waves, etc etc etc.
I've run another simulation, just for you. This time, I'm comparing two 12" drivers. One has a Qts of 0.31 and went in a ported box, and the other has a Qts of 0.5, which makes it more suited for sealed boxes.
Once again, I added some EQ to the sealed box (as you note, they tend to require some DSP). Since the response shapes varied quite drastically, I could only match the frequency responses from 30-110Hz - above that they started to diverge.
The sealed box now has 25ms of group delay at 40Hz (same as the ported box), and of course cone excursion has skyrocketed.
I tried going the other way, and EQing the ported box to match the sealed box. It was more difficult, but the group delay (and phase) curves started converging as the frequency responses were more closely matched.
It would appear, then, that when we're comparing sealed and ported cabinets, they're both acting as minimum-phase devices. ie, the phase response is some function of the frequency response, and it's the steeper rolloff of a ported box that results in the phase shifts.
In conclusion, if you EQ a sealed box to match the frequency response of a ported box, you'll get the time domain performance of the ported box, but with more harmonic distortion.
Chris
Hi Turk,
Yes most peole get confused if they hear that 99% of the loudspeaker design industry has been barking up the wrong tree for 100 years!
Prof Manger (RIP) are physicists, mathematicians and audio engineers experts in the field and if you read the reports and references they include you will undestand that the fundamental laws of physics that govern sound generation and sound reproduction do not change in line with increasing volume!
Rod Elliots single sub is designed to keep up with his main domestic home cinema speakers which hit 120dB peaks (max 114dB continuous) .
If you need to hit PA SPL's (130dB continuous 136dB peaks) here are some guidelines.
(1) For every doubling of Sd (driver surface area) you gain 3dB SPL.
(2) Assume series / parallel driver wiring to maintain origianl driver Ohm rating. One can wire in parallel and reduce from 8Ohm to 4 or even 2 Ohm and gain another 3dB or 6dB SPL IF your power amps are stable into low loads.
(3) Replacing point source subs with a Vertical line array of subs brings major benefits. All point sources ( at all frequencies, not just subs) suffer from 6dB losses in SPL with every doubling of distance, Line arrays only have a 3Db loss per doubling of distance. This may not be significant in small domestic rooms / nearfield recording studios, but this is HUGE in the live sound world.
Example at 50Hz:
For a small 500 seat / 1,000 body dance floor venue with a typical stage height clearance of 4 to 5 meters the sub stack needs to cover at least 70% of the floor to ceiling height to benefit from the line array benefits.
So use twin stacks (one left / one right stage) with 6 subs per stack (12 subs in total to give you max continuous SPL of over 125dB (131dB peaks) at 1 meter.
At 8 meters into the audience the sealed box array is maintaining 119 dB SPL with 125dB peaks.
This MATCHES the SPL at 8 meters of a 137dB (143dB peaks) point source sub!!!
At all distances beyond the 8 meter mark the line array / sealed box will have far superior SPL and lower distortion.
The sealed box line array also has the huge benefit of NOT deafening the front 5 rows of the audience with ear-bleeding levels, plus the back rows still have a high quality, high SPL experinece.
Yes most peole get confused if they hear that 99% of the loudspeaker design industry has been barking up the wrong tree for 100 years!
Prof Manger (RIP) are physicists, mathematicians and audio engineers experts in the field and if you read the reports and references they include you will undestand that the fundamental laws of physics that govern sound generation and sound reproduction do not change in line with increasing volume!
Rod Elliots single sub is designed to keep up with his main domestic home cinema speakers which hit 120dB peaks (max 114dB continuous) .
If you need to hit PA SPL's (130dB continuous 136dB peaks) here are some guidelines.
(1) For every doubling of Sd (driver surface area) you gain 3dB SPL.
(2) Assume series / parallel driver wiring to maintain origianl driver Ohm rating. One can wire in parallel and reduce from 8Ohm to 4 or even 2 Ohm and gain another 3dB or 6dB SPL IF your power amps are stable into low loads.
(3) Replacing point source subs with a Vertical line array of subs brings major benefits. All point sources ( at all frequencies, not just subs) suffer from 6dB losses in SPL with every doubling of distance, Line arrays only have a 3Db loss per doubling of distance. This may not be significant in small domestic rooms / nearfield recording studios, but this is HUGE in the live sound world.
Example at 50Hz:
For a small 500 seat / 1,000 body dance floor venue with a typical stage height clearance of 4 to 5 meters the sub stack needs to cover at least 70% of the floor to ceiling height to benefit from the line array benefits.
So use twin stacks (one left / one right stage) with 6 subs per stack (12 subs in total to give you max continuous SPL of over 125dB (131dB peaks) at 1 meter.
At 8 meters into the audience the sealed box array is maintaining 119 dB SPL with 125dB peaks.
This MATCHES the SPL at 8 meters of a 137dB (143dB peaks) point source sub!!!
At all distances beyond the 8 meter mark the line array / sealed box will have far superior SPL and lower distortion.
The sealed box line array also has the huge benefit of NOT deafening the front 5 rows of the audience with ear-bleeding levels, plus the back rows still have a high quality, high SPL experinece.
Exactly!
If you're doing PA and you're in love with the "sealed" sound, just take a vented box with an Fb that's close to or lower than the lowest frequency that you're interested in producing, and EQ it to have the response of a sealed box in the passband above that. Then sit back and enjoy the same transients and much better performance
Of course no-one really does that, as they want to enjoy the extra low end output that vented boxes provide as well.
This is a common mistake... A driver Qts of 0.5 makes it entirely unsuitable for sealed box!!
A driver Qts of 0.25 is the highest acceptable figure, and in fact, around 0.2 Qts is ideal.
Precision Devices, Beyma and RCF have a few ( 2 or 3 at the most) good examples 12, 15 and 18 inch domestic / small venue live sound, and there are a few 21 inch drivers for larger-scale venues.
Generally low Qts and high VAS with superb mechanical construction, large ferrite magnets (better heat dissipation) and linen (not rubber) surrounds are a good start.
No matter what driver you use, you have to look at the END RESULT. If the end result is a system with a particular Qtc and Fb in a specific net box volume, the transient response should be the same, no matter what driver you used.
BTW, all else being equal, high Vas drivers = light moving parts and/or shorter coil = much more likely to distort under high SPL conditions.
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