zlast - are you talking about this El Pipo? I was aware of it before building my sub and I definitely didn't want to replicate it - I'm not terribly impressed with their results.
As for corner placement, my room is not square or rectangular, it is very oddly shaped, and about 3500 cubic feet.
You can use poly batting, foam, or fiberglass batting, doesn't matter. Tube dimensions are of the tube, you don't take lining into account, as it doesn't matter. And I'm not using an 18" diameter port tube, I'm using 8". Don't know what you mena about "inside the damping".
That's for the RLp15, I use an Avalanche 18, my driver's Fs is 16hz.
4' apart is WAY too close for being 9-12' back in my opinion - you're killing the width of the soundstage.
As for corner placement, my room is not square or rectangular, it is very oddly shaped, and about 3500 cubic feet.
"I'm skeptical that you can go thru fs without somehow accounting for it in either the electronics or the enclosure design."
It happens all the time; Fs becomes Fc when you put the driver in a sealed box.
Most commercial systems have Fc in the 30's and 40's Hz, and respond well below that.
"Speaker distortion will be very high under such conditions. It depends on suspension linearity like it does not above fs."
Is this a thoretical generalization or an observation?
In any but very large boxes, the sir stiffness dominates and is quite linear.
Oh, you were speaking of OB, I forgot.
"The idea that you can just slew through this second order resonance is counter intuitive to me."
The resonance is well damped by back-EMF, as evidenced by there being little or no hump in the response.
"there is a 12DB difference...that means you would need multiple vented enclosures to equal one TL. "
Since BR give flat response, if that were true, TR systems would have a big hump at the low end as the output rose well above the driver's reference efficiency.
It happens all the time; Fs becomes Fc when you put the driver in a sealed box.
Most commercial systems have Fc in the 30's and 40's Hz, and respond well below that.
"Speaker distortion will be very high under such conditions. It depends on suspension linearity like it does not above fs."
Is this a thoretical generalization or an observation?
In any but very large boxes, the sir stiffness dominates and is quite linear.
Oh, you were speaking of OB, I forgot.
"The idea that you can just slew through this second order resonance is counter intuitive to me."
The resonance is well damped by back-EMF, as evidenced by there being little or no hump in the response.
"there is a 12DB difference...that means you would need multiple vented enclosures to equal one TL. "
Since BR give flat response, if that were true, TR systems would have a big hump at the low end as the output rose well above the driver's reference efficiency.
Steve, Thanks.
No sound stage is what I'm saying.
The home theater specs want the L and R speakers up close to the viewing screen. They want this so that sound can pan from one, to the center, and to the other.
They are not supposed to be far from the viewing screen.
This is too close for audio listening. That is the problem.
You almost need to have two sets of L and R speakers. Inboards and outboards.
Anyway, it sounds like the use of damping materials doesn't mean that the dimensions of the enclosure or of the port tube need to be recalculated.
You mentioned once that I big subwoofer box could be a TV stand. Problem is that your driver might not be of the special AV shielded type. Likewise if you wanted to build your own center speaker.
Any experience with putting metal into a speaker enclosure to create your own magnetic shielding?
Noah, I don't understand there being a big boost from TL at the bottom end. That does not make sense to me at all. TL is somewhat of an oddity. The usual benefit presented is a gradual bottom end. BR has a sharp bottom corner. But TL lets you try to push it as far as you want.
As far as high speaker distortion below fs, its just a product of the suspension becoming dominant, rather than the second order resonance.
Back EMF is not going to be totally linear either.
When you are above resonance, linearity in suspension or back emf is not nearly as important.
I am still attracted to the idea that Curent Source Amps might be a better way to go, for dropping below fs. I'm not sure.
No sound stage is what I'm saying.
The home theater specs want the L and R speakers up close to the viewing screen. They want this so that sound can pan from one, to the center, and to the other.
They are not supposed to be far from the viewing screen.
This is too close for audio listening. That is the problem.
You almost need to have two sets of L and R speakers. Inboards and outboards.
Anyway, it sounds like the use of damping materials doesn't mean that the dimensions of the enclosure or of the port tube need to be recalculated.
You mentioned once that I big subwoofer box could be a TV stand. Problem is that your driver might not be of the special AV shielded type. Likewise if you wanted to build your own center speaker.
Any experience with putting metal into a speaker enclosure to create your own magnetic shielding?
Noah, I don't understand there being a big boost from TL at the bottom end. That does not make sense to me at all. TL is somewhat of an oddity. The usual benefit presented is a gradual bottom end. BR has a sharp bottom corner. But TL lets you try to push it as far as you want.
As far as high speaker distortion below fs, its just a product of the suspension becoming dominant, rather than the second order resonance.
Back EMF is not going to be totally linear either.
When you are above resonance, linearity in suspension or back emf is not nearly as important.
I am still attracted to the idea that Curent Source Amps might be a better way to go, for dropping below fs. I'm not sure.
I highly, highly doubt you will be giving up anything with movies - in fact, movie reproduction should improve as well. A big, wide soundstage adds to the experience in many ways, whether for music or movies.
Correct, the cabinet would have to have sheets of metal on the inside.
Yeah, see here - Ryan shielded his sub cabinets. By the way, he's now ditching the sealed and going with a LLT - he's seen the light
Steve, for playing music in the movies, wider speaker placement would help.
But its not up to you or I.
Its the LucasFilm surround sound spec. It calls for the speakers to be just opposite the screen.
So, when something moves from left to right, the pan its sound based on that assumption.
If you change the speaker placement, it won't sound right for the visuals.
If you have a very big screen, like front projection from floor to ceiling, and if you sit closer for music listening, that might solve it.
Maybe someday the spec will be expanded to actually have inboard and outboard speakers.
Your 700 litre speaker is impressive. Brian.
But its not up to you or I.
Its the LucasFilm surround sound spec. It calls for the speakers to be just opposite the screen.
So, when something moves from left to right, the pan its sound based on that assumption.
If you change the speaker placement, it won't sound right for the visuals.
If you have a very big screen, like front projection from floor to ceiling, and if you sit closer for music listening, that might solve it.
Maybe someday the spec will be expanded to actually have inboard and outboard speakers.
Your 700 litre speaker is impressive. Brian.
I personally don't care much about what THX says. What about the Dolby spec?
Based on their diagram, the mains and you should create an equillateral triangle, or one pretty close to equillateral, meaning if you are 9' back, the speakers should be 8-9' apart.
In all honesty, I find the truth to lay somewhere in between. Not a true equillateral triangle, and not always at the sides of the screen (as that assumes too much).
An externally hosted image should be here but it was not working when we last tested it.
Based on their diagram, the mains and you should create an equillateral triangle, or one pretty close to equillateral, meaning if you are 9' back, the speakers should be 8-9' apart.
In all honesty, I find the truth to lay somewhere in between. Not a true equillateral triangle, and not always at the sides of the screen (as that assumes too much).
Steve, Interesting picture. I follow you.
I believe that in movie theaters, the left and right are actually behind the screen, just like the center.
I guess the real test would just be to pay attention to some feature films, and how the sound coordinates to the motion across the screen. From that, one should be able to decide where the speakers should best be.
This is a known issue. I still think that one could have multiple speaker sets. Eventually I hope they expand the surround sound spec to have five front channels, plus surrounds.
How about another angle on the below fs speakers?
Just an idea. I don't have the book in front of me. But in Martin Colloms's book he explains how those Bose shoebox size subwoofers work.
As I remember, there are three chambers. The driver goes between numbers 1 and 2. A tube connects numbers 2 and 3. Another tube connects number 3 to the outside.
Now, normally any significant driver loading, front or back, raises resonance, from say fs, to some loaded value, fl.
Maybe here it can work different, because there are two chambers on one side of the driver. Maybe these chambers 2 and 3 can make their own resonance which compensates for the driver resonance. So there really is no fs threshold. Maybe this is how it works?
Of course Bose designed this to sell real small cutsie stuff. For how small it is, the performance is impressive.
Suppose instead we designed one around your 18" driver? Suppose it was made real big, so the tube diameters can be large.
I know that the Allen organ company made some big coffin like enclosures for going down to 16 hz. Maybe they worked something like that?
I believe that in movie theaters, the left and right are actually behind the screen, just like the center.
I guess the real test would just be to pay attention to some feature films, and how the sound coordinates to the motion across the screen. From that, one should be able to decide where the speakers should best be.
This is a known issue. I still think that one could have multiple speaker sets. Eventually I hope they expand the surround sound spec to have five front channels, plus surrounds.
How about another angle on the below fs speakers?
Just an idea. I don't have the book in front of me. But in Martin Colloms's book he explains how those Bose shoebox size subwoofers work.
As I remember, there are three chambers. The driver goes between numbers 1 and 2. A tube connects numbers 2 and 3. Another tube connects number 3 to the outside.
Now, normally any significant driver loading, front or back, raises resonance, from say fs, to some loaded value, fl.
Maybe here it can work different, because there are two chambers on one side of the driver. Maybe these chambers 2 and 3 can make their own resonance which compensates for the driver resonance. So there really is no fs threshold. Maybe this is how it works?
Of course Bose designed this to sell real small cutsie stuff. For how small it is, the performance is impressive.
Suppose instead we designed one around your 18" driver? Suppose it was made real big, so the tube diameters can be large.
I know that the Allen organ company made some big coffin like enclosures for going down to 16 hz. Maybe they worked something like that?
You're referring to a bandpass subwoofer. All of your output has to pass through a port, sometimes two ports. In "porting" the ported output with the intent of achieving a second resonance, I think you're creating more harm than good.
One of the main goals in my design was to minimize or eliminate the negative effects associated with port use in audible regions by only allowing the port output to come into significant play in extremely low frequencies. By doing so, I get free clean output where it's needed the most in trying to achieve a linear FR to very low frequencies, and I get to keep a clean and detailed top end that will sound better than a traditional ported subwoofer.
I'm puzzled as to why you are still obsessing over Fs. Has this thread not shown that it isn't that big of a deal?
One of the main goals in my design was to minimize or eliminate the negative effects associated with port use in audible regions by only allowing the port output to come into significant play in extremely low frequencies. By doing so, I get free clean output where it's needed the most in trying to achieve a linear FR to very low frequencies, and I get to keep a clean and detailed top end that will sound better than a traditional ported subwoofer.
I'm puzzled as to why you are still obsessing over Fs. Has this thread not shown that it isn't that big of a deal?
The way you are talking about minimizing the use of ports, except at the very bottom end, it does make me wonder if maybe TL might be more suitable.
I am still concerned about fs. I'm not convinced that the matter is fully explored.
You said your driver is fs=16hz. This is one of the lower numbers I've seen. Did you pick your driver to get a low as possible fs ?
As far as the Bose approach, yes, it is called band pass.
I still think there are more to all these matters. I don't feel qualified yet to assess all the trade offs of all the different ways.
Like I say, BagEnd and Elliot Sound have special circuit techniques to deal with going below fs. The BagEnd approach looks quite complex.
The most theoretical book I know of is Martin Colloms. Maybe there is something newer, better?
Maybe more people are using feedback?
I am still concerned about fs. I'm not convinced that the matter is fully explored.
You said your driver is fs=16hz. This is one of the lower numbers I've seen. Did you pick your driver to get a low as possible fs ?
As far as the Bose approach, yes, it is called band pass.
I still think there are more to all these matters. I don't feel qualified yet to assess all the trade offs of all the different ways.
Like I say, BagEnd and Elliot Sound have special circuit techniques to deal with going below fs. The BagEnd approach looks quite complex.
The most theoretical book I know of is Martin Colloms. Maybe there is something newer, better?
Maybe more people are using feedback?
I gave up 10 pages ago.
Brian, if you really want to learn this stuff, do what I said a long time ago. Throw out all your books that do not deal specifically with very low tuned subwoofers (all of them). Accept the fact that Steve has demonstrated a working realization of exactly what you want. Understand the fact that there are a couple of different ways to achieve this effect but they are ALL very well understood, documented and widely in use. Give in to the fact that you do not need to understand EVERY ASPECT fully or nothing will ever be built. You could spend a lifetime investigating how pollen and dust in the air affect your low frequency content but in the end IT DOESN'T MATTER.
Steve has shown you how to make a sub that is relatively flat to at least 10 hz with under $1000. Your questioning seems to indicate that you don't believe he measured his results properly or that he is exagerating the output.
Up to the last page, you are still asking about huge, low fs drivers. This question has been answered multiple times already. There is NO MARKET because NOBODY NEEDS OR WANTS THEM. The driver Steve is using is more than you will ever need.
Have you downloaded WinISD yet? Have you searched this forum for other low tuned subs? There's really nothing to talk about until you do your research. (Research on low tuned subs, not the generic speaker books you seem to love and trust so much.)
Brian, if you really want to learn this stuff, do what I said a long time ago. Throw out all your books that do not deal specifically with very low tuned subwoofers (all of them). Accept the fact that Steve has demonstrated a working realization of exactly what you want. Understand the fact that there are a couple of different ways to achieve this effect but they are ALL very well understood, documented and widely in use. Give in to the fact that you do not need to understand EVERY ASPECT fully or nothing will ever be built. You could spend a lifetime investigating how pollen and dust in the air affect your low frequency content but in the end IT DOESN'T MATTER.
Steve has shown you how to make a sub that is relatively flat to at least 10 hz with under $1000. Your questioning seems to indicate that you don't believe he measured his results properly or that he is exagerating the output.
Up to the last page, you are still asking about huge, low fs drivers. This question has been answered multiple times already. There is NO MARKET because NOBODY NEEDS OR WANTS THEM. The driver Steve is using is more than you will ever need.
Have you downloaded WinISD yet? Have you searched this forum for other low tuned subs? There's really nothing to talk about until you do your research. (Research on low tuned subs, not the generic speaker books you seem to love and trust so much.)
This is my first post to this thread, and apologize if this info was mentioned before.
Looking at the Fostex FW800N, it has a very high Vas, which means it needs to be in a very large box or infinite baffle. Reference Audio Magazine, December, 1999 issue by Tom Nousaine on DIY subwoofers. In the article, there were several "Subwoofer in the floor" installations that this Fostex would be ideal for, and would probably get to 10Hz or lower if so mounted. The Xmax of this Fostex driver, however, is fairly limited at 2.3mm, and really won’t get that loud compared to smaller 22” T9922 – 44 (True22 ) (http://www.mtx.com/caraudio/products/subwoofers/jackHammer.cfm) or 18” JBL 2242H (http://www.jblpro.com/FullLineCat/Portable C.pdf) et al, subwoofers.
The Nousaine article goes on to describe four subwoofer installations that are along the lines of “Giant subwoofers”. One described four 18” JBL drivers mounted in the floor of the listening room, the RK 4-18, using the basement as an enclosure, that achieved 126dB spl at 16Hz in the listening position, and has considerable output at 8Hz. There was an economical installation similar to this using four 15” low cost woofers in the floor, the TH 4-15, that performed incrediblly well into the subsonics.
The owner of the TH 4-15 used an EV 30W 30” subwoofer in a previous installation that also did remarkably well into the subsonics. The JBL’s, EV’s, and others can be found on eBay or Parts Express
Looking at the Fostex FW800N, it has a very high Vas, which means it needs to be in a very large box or infinite baffle. Reference Audio Magazine, December, 1999 issue by Tom Nousaine on DIY subwoofers. In the article, there were several "Subwoofer in the floor" installations that this Fostex would be ideal for, and would probably get to 10Hz or lower if so mounted. The Xmax of this Fostex driver, however, is fairly limited at 2.3mm, and really won’t get that loud compared to smaller 22” T9922 – 44 (True22 ) (http://www.mtx.com/caraudio/products/subwoofers/jackHammer.cfm) or 18” JBL 2242H (http://www.jblpro.com/FullLineCat/Portable C.pdf) et al, subwoofers.
The Nousaine article goes on to describe four subwoofer installations that are along the lines of “Giant subwoofers”. One described four 18” JBL drivers mounted in the floor of the listening room, the RK 4-18, using the basement as an enclosure, that achieved 126dB spl at 16Hz in the listening position, and has considerable output at 8Hz. There was an economical installation similar to this using four 15” low cost woofers in the floor, the TH 4-15, that performed incrediblly well into the subsonics.
The owner of the TH 4-15 used an EV 30W 30” subwoofer in a previous installation that also did remarkably well into the subsonics. The JBL’s, EV’s, and others can be found on eBay or Parts Express
I'm not finding an EV 30". I see two different 18" versions. The lower fs is 24hz. Sounds like Steve has fs of 16hz on his.
This whole subject of drivers bigger than 18" seems to be quite new.
To me, going below fs is still territory I am uncertain of, but interested in learning more about.
I'm going to get the Martin Colloms book back
This whole subject of drivers bigger than 18" seems to be quite new.
To me, going below fs is still territory I am uncertain of, but interested in learning more about.
I'm going to get the Martin Colloms book back
It is possible to simulate a infinite baffle with two speakers.
The first speaker will have a first order high pass filter.
(With my speakers this is at 400 hz – ESL unit)
If you use a first order high pass filter at the lowest frequency you want to use for the woofer the response will be flat up to the same frequency as the high unit wit a first order role off, creating a natural first order filter between both units.
(My speakers start at 50 Hz up to 400 Hz)
To do this you need quality units with high SPL and a big amp.
For more info about the diy kit I use see the kit supplier at http://www.metrum-acoustics.nl/
I also created a Sub for these speakers using a big 32” Clarion SRW 8000 unit.
The low frequency is tuned at 17 Hz and the acoustic role off at about 85hz.
For home theatre use my amp filters 24 Db at 80 hz.
For audio use a added a first order role off at 50 hz.
So a sub can be created with one big high SPL unit ore a big array of smaller units. The lower the frequency you use you the more units you need.
You can start with lets say 4 high spl 12” units.
The first speaker will have a first order high pass filter.
(With my speakers this is at 400 hz – ESL unit)
If you use a first order high pass filter at the lowest frequency you want to use for the woofer the response will be flat up to the same frequency as the high unit wit a first order role off, creating a natural first order filter between both units.
(My speakers start at 50 Hz up to 400 Hz)
To do this you need quality units with high SPL and a big amp.
For more info about the diy kit I use see the kit supplier at http://www.metrum-acoustics.nl/
I also created a Sub for these speakers using a big 32” Clarion SRW 8000 unit.
The low frequency is tuned at 17 Hz and the acoustic role off at about 85hz.
For home theatre use my amp filters 24 Db at 80 hz.
For audio use a added a first order role off at 50 hz.
So a sub can be created with one big high SPL unit ore a big array of smaller units. The lower the frequency you use you the more units you need.
You can start with lets say 4 high spl 12” units.
Giant Subwoofer
The Electro Voice company first introduced the 30W thirty-inch speaker in the Patrician 4 way system in 1959. This system was available through the late 60’s, and the speaker as a component through the late 70’s. The Patrician was designed to be a corner mounted speaker to use the walls of the room as extensions of the low frequency horn contained in the speaker cabinet. See http://www.telex.de/html/presseartikel_e.php?id=207 . The Patrician system is very large and heavy. A search of eBay showed a pair for sale. A search of vintage audio websites showed the 30W speaker available from at least one site. The speaker has a very large Vas, and needs a large box, or basement, to house it. According to a retired EV speaker engineer, a 100 cubic foot enclosure was required to obtain adequate response down to 16Hz. For lower frequencies, a larger box or preferably a basement is recommended. I remember hearing both the Patrician in an audio store, and the 30W in a basement subwoofer installation and both were very impressive. The practical drawback to the 30W is that is has a small diameter voice coil, I believe 2.5”, and a short stroke, about 3mm. The sensitivity rating was in the neighborhood of 98 or 99 db/1Watt/1meter, so it is quite efficient, but the 2.5” voice coil cannot dissipate large amounts of power by today’s standards.
Recent DVD movies have had a great amount of sub sonic material in them. I saw one that had extremely low excursions in the 3-4Hz region. In addition, I can recommend two audio CD’s as a test of true subwoofer subsonic capability: TELARC CD-80041, Tchaikovsky 1812, and TELARC CD-80079, Beethoven Wellington’s Victory. Both has significant content in the 5 to 6Hz area and can only be adequately reproduced by a subwoofer of substantial capability. The 1812 is particularly renowned as the subwoofer speaker and headphone killer. Many speakers have met their demise in trying to play this CD. Another area where there is significant low frequency content is in a marching band bass drum. There is a "“whoosh" that follows hitting the drum that is absent in systems with inadequate low frequency response. If the ideal of sound reproduction is to give you the feeling that you are there, then having this sub sonic content is required.
The Electro Voice company first introduced the 30W thirty-inch speaker in the Patrician 4 way system in 1959. This system was available through the late 60’s, and the speaker as a component through the late 70’s. The Patrician was designed to be a corner mounted speaker to use the walls of the room as extensions of the low frequency horn contained in the speaker cabinet. See http://www.telex.de/html/presseartikel_e.php?id=207 . The Patrician system is very large and heavy. A search of eBay showed a pair for sale. A search of vintage audio websites showed the 30W speaker available from at least one site. The speaker has a very large Vas, and needs a large box, or basement, to house it. According to a retired EV speaker engineer, a 100 cubic foot enclosure was required to obtain adequate response down to 16Hz. For lower frequencies, a larger box or preferably a basement is recommended. I remember hearing both the Patrician in an audio store, and the 30W in a basement subwoofer installation and both were very impressive. The practical drawback to the 30W is that is has a small diameter voice coil, I believe 2.5”, and a short stroke, about 3mm. The sensitivity rating was in the neighborhood of 98 or 99 db/1Watt/1meter, so it is quite efficient, but the 2.5” voice coil cannot dissipate large amounts of power by today’s standards.
Recent DVD movies have had a great amount of sub sonic material in them. I saw one that had extremely low excursions in the 3-4Hz region. In addition, I can recommend two audio CD’s as a test of true subwoofer subsonic capability: TELARC CD-80041, Tchaikovsky 1812, and TELARC CD-80079, Beethoven Wellington’s Victory. Both has significant content in the 5 to 6Hz area and can only be adequately reproduced by a subwoofer of substantial capability. The 1812 is particularly renowned as the subwoofer speaker and headphone killer. Many speakers have met their demise in trying to play this CD. Another area where there is significant low frequency content is in a marching band bass drum. There is a "“whoosh" that follows hitting the drum that is absent in systems with inadequate low frequency response. If the ideal of sound reproduction is to give you the feeling that you are there, then having this sub sonic content is required.
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