Hi, subject says it all.
I am just finishing to rebuild a freaking power amp, and fallen into my hands a nice sub for very cheap.
The sub i have is a car subwoofer, SWX 1242D capable of 1000wrms, 3000 peak, 12 inches, dual 4 ohm voice coil.
The amp is a QSC usa 900 clone, sligtly modified to pump around 1000wrms at 8 ohm in bridged mode.
I also have a "down converter" which takes the fundamental frequency down low and divide it by two and put it back into the music...it remembers me the so called "Epicenter" from Audio control, for car system applications. It realy makes the difference !!!
So, i have also a 12 inch concrete tube...it just lends me to build a EL PIPO.
(COPY/PASTE FROM THE WRONG FORUM, SORRY)
sub spec
I am also thinking about a front loaded horn, but i am totaly lost as to where to start picking up info for this. I searched a bit on this site, i returned me either super specific info with complicated calculations, or elusive info.
Can i have some help my friends ??
I have enough space, i am using my home basement for the project.
Is there any calculators tha i can download and enter my sub specs and "fo" wanted, then it returns most of the dimensions to build the horn ??
Id like to get pictures of finished projects similar to mine.
thanks !!
I am just finishing to rebuild a freaking power amp, and fallen into my hands a nice sub for very cheap.
The sub i have is a car subwoofer, SWX 1242D capable of 1000wrms, 3000 peak, 12 inches, dual 4 ohm voice coil.
The amp is a QSC usa 900 clone, sligtly modified to pump around 1000wrms at 8 ohm in bridged mode.
I also have a "down converter" which takes the fundamental frequency down low and divide it by two and put it back into the music...it remembers me the so called "Epicenter" from Audio control, for car system applications. It realy makes the difference !!!
So, i have also a 12 inch concrete tube...it just lends me to build a EL PIPO.
(COPY/PASTE FROM THE WRONG FORUM, SORRY)
sub spec
I am also thinking about a front loaded horn, but i am totaly lost as to where to start picking up info for this. I searched a bit on this site, i returned me either super specific info with complicated calculations, or elusive info.
Can i have some help my friends ??
I have enough space, i am using my home basement for the project.
Is there any calculators tha i can download and enter my sub specs and "fo" wanted, then it returns most of the dimensions to build the horn ??
Id like to get pictures of finished projects similar to mine.
thanks !!
Hey Pat.....
if their are any "Transmission Line Subwoofer" calculators out there, I'd sure like to find one !
I'm fixing to start experimenting with TL setups myself. I have searched unsuccessfully, for some type of calculator. So now I think I have decided to just get me a nice big sonotube (probably a 16" or 18") x 14ft or so. Then attach a couple of 15" Dayton Titanics to one end of it {in a push-pull configuartion}, and start playing around with this and a frequency meter. Too low... cut off some pipe. Too high.... add some stuffing.
On the one hand, a calculator would be great..... But on the other hand, personally speaking, I think I might take a little more pride and satifaction in the project if I did it myself, and it then especially if it came out bombastic
Peace,
Fish
PS, This guy is using two 10"s in each of these tubes. http://www.teresaudio.com/haven/subs/subs.html
This setup seems kind of modest to me.... but then this guy was not trying to rock the house down either. He was just shooting for the "nicest sounding bass" he could get, and claims he has found it with this setup.
if their are any "Transmission Line Subwoofer" calculators out there, I'd sure like to find one !
I'm fixing to start experimenting with TL setups myself. I have searched unsuccessfully, for some type of calculator. So now I think I have decided to just get me a nice big sonotube (probably a 16" or 18") x 14ft or so. Then attach a couple of 15" Dayton Titanics to one end of it {in a push-pull configuartion}, and start playing around with this and a frequency meter. Too low... cut off some pipe. Too high.... add some stuffing.
On the one hand, a calculator would be great..... But on the other hand, personally speaking, I think I might take a little more pride and satifaction in the project if I did it myself, and it then especially if it came out bombastic
Peace,
Fish
PS, This guy is using two 10"s in each of these tubes. http://www.teresaudio.com/haven/subs/subs.html
This setup seems kind of modest to me.... but then this guy was not trying to rock the house down either. He was just shooting for the "nicest sounding bass" he could get, and claims he has found it with this setup.
I know how you feel
I made few test last years with my actual sonotube.
12 feet long, 12inches diameter. I was using a 12inch subwoofer that i was already having, not good quality.
I made some sound test with a frequency generator. The tube was horizontal. I read somewhere that it MUST be vertical...
Anyway, i got some noise going out of it, but was a bit disapointed about the SPL. There was something like 100w in play.
Its been 2 hours now that i am searching this forum...
there is a lot of simple questions unanswered, and there is far more bla bla bla (no offence to anyone plz) rather than real buildups or physical tests.
simple question like:
1-what kind of "system" makes the most SPL
2-what is the easiest one to build
3-what is doable and what is not
practicaly speaking, a system that makes terrific spl, but within a very narrow bandwidht is out of equation...
My quest is to build "something" that can makes music sound like music, from anything in between 0hz and 100hz, where most of the "normal on the shelf" speakers literally stop to play...
AND/OR something that makes the house going off of its foundations...
i wonder what 0hz sounds like...anyway...
I played a lot in the past in car audio, i made a lot of good "kit" with many subs, the better one was with 4 12 inches in a minivan. It was quite loud and very disturbing
i played with...bandpass, double bandpass, compound, ported, sealed,...
i know how good bass feel, and id like to make it in my house
I have big thought about a front or rear loaded horn. The fact that it can extend the fo of the sub 1/2 is tempting, but seems a lot complicated to build and calculate.
I made few test last years with my actual sonotube.
12 feet long, 12inches diameter. I was using a 12inch subwoofer that i was already having, not good quality.
I made some sound test with a frequency generator. The tube was horizontal. I read somewhere that it MUST be vertical...
Anyway, i got some noise going out of it, but was a bit disapointed about the SPL. There was something like 100w in play.
Its been 2 hours now that i am searching this forum...
there is a lot of simple questions unanswered, and there is far more bla bla bla (no offence to anyone plz) rather than real buildups or physical tests.
simple question like:
1-what kind of "system" makes the most SPL
2-what is the easiest one to build
3-what is doable and what is not
practicaly speaking, a system that makes terrific spl, but within a very narrow bandwidht is out of equation...
My quest is to build "something" that can makes music sound like music, from anything in between 0hz and 100hz, where most of the "normal on the shelf" speakers literally stop to play...
AND/OR something that makes the house going off of its foundations...
i wonder what 0hz sounds like...anyway...
I played a lot in the past in car audio, i made a lot of good "kit" with many subs, the better one was with 4 12 inches in a minivan. It was quite loud and very disturbing
i played with...bandpass, double bandpass, compound, ported, sealed,...
i know how good bass feel, and id like to make it in my house
I have big thought about a front or rear loaded horn. The fact that it can extend the fo of the sub 1/2 is tempting, but seems a lot complicated to build and calculate.
the late Bob Bullock's free DOS t-line boxmodel program might (?) work - someone here may have a feel for specifying stuffing density so could ~correlate to MJK's work (?)
http://www.hal-pc.org/~bwhitejr/
http://www.hal-pc.org/~bwhitejr/
Ive made a few sonotube pipes subs and all I can say is that they are worth the effort.
one was made with a 12" 8ft length of pipe and a 12" kenwood car stereo driver siliconed into place. pipe is filled with polyester
the other uses a 4" voice coiled 18" (industrial 98 db@1w, 1m) in a 10ft pipe, 18" diameter, siliconed into place. filled with fiberglass
I have used them both vertically and horizontally with no noticable difference.
The first system lives in my living room, The second lives in a 250 seat cinema.
awesome is a common comment at the cinema!
one was made with a 12" 8ft length of pipe and a 12" kenwood car stereo driver siliconed into place. pipe is filled with polyester
the other uses a 4" voice coiled 18" (industrial 98 db@1w, 1m) in a 10ft pipe, 18" diameter, siliconed into place. filled with fiberglass
I have used them both vertically and horizontally with no noticable difference.
The first system lives in my living room, The second lives in a 250 seat cinema.
awesome is a common comment at the cinema!
Hi Pat,
The facts are.
1. the mouth circumference >= wavelength of the lowest frequncy to be reproduced.
2. the flare rate, controlling the length, is related to the lowest frequency to be reproduced.
3. the horn length >=either a quarter or a half wavelength of the lowest frequency to be reproduced.
4. the throat area should be related to the cone area, usually equal to or down to one third Sd area.
5. the frequency range from a horn loaded driver cannot approach the ten octaves in normal music. Usually it is divided into two or three octave segments and each is designed for appropriately.
6. the room loading on the horn can usefully reduce the mouth area required for good sound reproduction. This is usually only applied to the bass frequencies, mid and treble frequency horns are usually designed for operating into free space.
The result of all this is that as the required bass frequency goes down the bigger the horn becomes, in volume, length and width.
most of the information on this site and the references quoted in it are consistent. There are anomalies but often they are more to do with the amount of truncation of the true horn and the sound (depth and quality/response variation) that results from that truncation (cutting off the horn before it reaches it's required length/mouth area).
The facts are.
1. the mouth circumference >= wavelength of the lowest frequncy to be reproduced.
2. the flare rate, controlling the length, is related to the lowest frequency to be reproduced.
3. the horn length >=either a quarter or a half wavelength of the lowest frequency to be reproduced.
4. the throat area should be related to the cone area, usually equal to or down to one third Sd area.
5. the frequency range from a horn loaded driver cannot approach the ten octaves in normal music. Usually it is divided into two or three octave segments and each is designed for appropriately.
6. the room loading on the horn can usefully reduce the mouth area required for good sound reproduction. This is usually only applied to the bass frequencies, mid and treble frequency horns are usually designed for operating into free space.
The result of all this is that as the required bass frequency goes down the bigger the horn becomes, in volume, length and width.
Thanks guys....
Hey Cameron G, each successful TL subwoofer pipe I hear of, gives me that much more confidence.
I notice you said they work fine horizontal.... as I originally suspected.... Although I think I have figured out at least one reason this is not rcommended > The stuffing needs to be spread evenly, and given some time and use, if layed on its side, the stuffing might tend to squash down to the bottom side. Maybe if one could find a stuffing with more body... like maybe furniture batting ?
Peace,
Fish
Hey Cameron G, each successful TL subwoofer pipe I hear of, gives me that much more confidence.
I notice you said they work fine horizontal.... as I originally suspected.... Although I think I have figured out at least one reason this is not rcommended > The stuffing needs to be spread evenly, and given some time and use, if layed on its side, the stuffing might tend to squash down to the bottom side. Maybe if one could find a stuffing with more body... like maybe furniture batting ?
Peace,
Fish
hope this helps think its worth you checking it out cheers TC
i still dont have some clear idea as to which design to choose... horn or tl ?what should i expect from both if properly designed ?
i will try the tl for sure asi have all the material to do it, but i would like to get some idea with my Alpine sub spec, what box dimensions it could be for the horn type.
What are the basics with horn type, such as, do i have to choose a fo, 1/4 or 1/2 lenght,...
Sure that my wich is to find someone kind enough to help me design or find box dimensions for a horn box with my sub spec.
thanks.
Hi,
tell us how low you want the bass horn to go and we'll tell you if it can fit inside the house.
Will it be floor (one boundary) or floor+wall (two boundaries) or corner (all three boundaries) loaded?
How much truncation do you think you can accept?
I have no idea, all I know is that more truncation means more deterioration in performance.
tell us how low you want the bass horn to go and we'll tell you if it can fit inside the house.
Will it be floor (one boundary) or floor+wall (two boundaries) or corner (all three boundaries) loaded?
How much truncation do you think you can accept?
I have no idea, all I know is that more truncation means more deterioration in performance.
Andrew, the speaker seems to load well with the pipe, whether it reacts like a large infinite baffle or a ported design I do not know.
I have always liked the sound of voight 1/4 wavelength styles of speakers and have used a tapered pipe (6.5inch Vifa 2 way) as my main speakers for over 10 years now. When it came to adding a sub, the natural 1/4 wavelength bass sound was my modivation to experiment. It was far easier than I suspected.
My approach was simple, tune the pipe to the 1/4 wavelength of the speakers fs, fine tune with dampening material. The most time consuming aspect of the project was picking up the pipe from Boral formworks, and each was made and working on the same day.
To me 1/4 wavelegth speakers have a more efficient low end than ported or sealed. I cannot comment on horns, but am very tempted to try to build one next! Audio Express have an interesting design recently published. A friend of mine boosts the 27hz in his horns and they sound awsome!
Other 1/4 wavelength ideals that I have had luck with is the use of Altec inspired wings/ baffles added to the sides of standard style cinema speakers. I guess that if you create the conditions to create a more perfect wave, the more natural the sound.
I usually place my 8 ft pipe in the corner with the driver facing down on 2" feet and the other end only is a few feet from the ceiling, when I place it on its side, it is then fairly close to both side walls, so perhaps the results are only similar due to the shape of my particular room.
The cinema is set up driver facing down at 1/3 width behind the screen. The sub is powered by a 300w amp and has had no problems at extreme sound levels and its a big room! it is only required below 50hz.
Most of my work done in cinemas I have seen the results through a spectrum analizer, unfortunatly not in this case with the pipe sub. To my ears/bones the result is equally as impressive as my last cinema sub which was based on an expensive EV driver ($ 750 )with a foam surround in a 600 litre box tuned to 25hz, it was measured 3db down at 25hz. The sonotube used a cheaper driver ($400 )with a cloth surround (tighter suspension).
Now I do not understand the theory, but have been told that a usable response from 22hz can be expected from the sonotube sub. Hopefully I will see the results through a spectrum analizer one day.
Next time I make one I will be using rockwool as the dampening material!
I have always liked the sound of voight 1/4 wavelength styles of speakers and have used a tapered pipe (6.5inch Vifa 2 way) as my main speakers for over 10 years now. When it came to adding a sub, the natural 1/4 wavelength bass sound was my modivation to experiment. It was far easier than I suspected.
My approach was simple, tune the pipe to the 1/4 wavelength of the speakers fs, fine tune with dampening material. The most time consuming aspect of the project was picking up the pipe from Boral formworks, and each was made and working on the same day.
To me 1/4 wavelegth speakers have a more efficient low end than ported or sealed. I cannot comment on horns, but am very tempted to try to build one next! Audio Express have an interesting design recently published. A friend of mine boosts the 27hz in his horns and they sound awsome!
Other 1/4 wavelength ideals that I have had luck with is the use of Altec inspired wings/ baffles added to the sides of standard style cinema speakers. I guess that if you create the conditions to create a more perfect wave, the more natural the sound.
I usually place my 8 ft pipe in the corner with the driver facing down on 2" feet and the other end only is a few feet from the ceiling, when I place it on its side, it is then fairly close to both side walls, so perhaps the results are only similar due to the shape of my particular room.
The cinema is set up driver facing down at 1/3 width behind the screen. The sub is powered by a 300w amp and has had no problems at extreme sound levels and its a big room! it is only required below 50hz.
Most of my work done in cinemas I have seen the results through a spectrum analizer, unfortunatly not in this case with the pipe sub. To my ears/bones the result is equally as impressive as my last cinema sub which was based on an expensive EV driver ($ 750 )with a foam surround in a 600 litre box tuned to 25hz, it was measured 3db down at 25hz. The sonotube used a cheaper driver ($400 )with a cloth surround (tighter suspension).
Now I do not understand the theory, but have been told that a usable response from 22hz can be expected from the sonotube sub. Hopefully I will see the results through a spectrum analizer one day.
Next time I make one I will be using rockwool as the dampening material!
Greets!
http://www.crutchfield.com/S-AuK3sU...g=520&tab=features_and_specs&i=500SWX1242#Tab
According to these published specs an Alpha TL (which is basically what the El Pipe-O is) tuned to Fs would be:
L = 117.38"
CSA = 25.481"^2 (~5.696" dia. or 5.048" square)
stuffing density w/ polyfil = 0.781 lbs/ft^3 (21.63 oz total)
These can be rounded up to the nearest inch/whatever without penalty. Considering the driver's highish Qts and power rating, I'd use at least a ~6" pipe.
WRT FLH, this driver really wants to be BH loaded, which if there's enough room (probably not) and budget will get down to around 9 Hz with a ~43% calc'd efficiency (108+ dB/W/m half space), but a ~19.8 (or less) - ~70 Hz FLH is doable too. Any higher and the CR gets too high.
GM
http://www.crutchfield.com/S-AuK3sU...g=520&tab=features_and_specs&i=500SWX1242#Tab
According to these published specs an Alpha TL (which is basically what the El Pipe-O is) tuned to Fs would be:
L = 117.38"
CSA = 25.481"^2 (~5.696" dia. or 5.048" square)
stuffing density w/ polyfil = 0.781 lbs/ft^3 (21.63 oz total)
These can be rounded up to the nearest inch/whatever without penalty. Considering the driver's highish Qts and power rating, I'd use at least a ~6" pipe.
WRT FLH, this driver really wants to be BH loaded, which if there's enough room (probably not) and budget will get down to around 9 Hz with a ~43% calc'd efficiency (108+ dB/W/m half space), but a ~19.8 (or less) - ~70 Hz FLH is doable too. Any higher and the CR gets too high.
GM
Hey GM.....
First off, please don't take this as if I'm arguing with you, as you wouldn't have to know much, to know more than me. However, I have read (and gained as much, in viewing successful TL horn designs) that a 12" sub should have at least a 12" diamter pipe.... if not 13" or 14". Remember El-Pipo used a 24" pipe, for two 21" inch subs.... then later, for single 21" subs....
How do you conclude that a 6" pipe would be okay for a 12" woofer ?
Here are the specs for the 15" sub woofer(s) I'm looking at:
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=295-420
I was thinking of at least a 16" diameter pipe, if not 18"...... No ?
Geeez, what I'd give for a straight up TL design calculating program.... just type in the woofer specs and click go.....
Peace,
Fish
First off, please don't take this as if I'm arguing with you, as you wouldn't have to know much, to know more than me. However, I have read (and gained as much, in viewing successful TL horn designs) that a 12" sub should have at least a 12" diamter pipe.... if not 13" or 14". Remember El-Pipo used a 24" pipe, for two 21" inch subs.... then later, for single 21" subs....
How do you conclude that a 6" pipe would be okay for a 12" woofer ?
Here are the specs for the 15" sub woofer(s) I'm looking at:
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=295-420
I was thinking of at least a 16" diameter pipe, if not 18"...... No ?
Geeez, what I'd give for a straight up TL design calculating program.... just type in the woofer specs and click go.....
Peace,
Fish
Greets!
Conventional wisdom says use a pipe of ~the same CSA as driver Sd, but it's BS and even the pioneer speaker designers knew this since it was well known from building pipe organs that the circumference of a pipe sets its LF cutoff, so to get around this humongous size required they put the driver in a big box and tapered it down to a big, long tube vent that was equal to ~Sd to keep acoustic efficiency fairly high. Somewhere along the line the box was reduced because as more power became available they didn't need so much box efficiency, then dropped altogether as the Vas of the drivers dropped (acoustic suspension era) and continues unabated today in the quest to get ever smaller cabs and why this ultra low Vas driver only requires a small pipe to load it properly.
So much for 'conventional wisdom'. It was ~valid at one time, but no longer unless a high Fp is desired or acceptable.
That said, the bigger the pipe the greater its gain up to a point of diminishing returns, which is around 4x Vas, so at ~7810.6"^3 for this driver, a ~9.2" dia. is the theoretical point of diminishing returns in a ~117.38" long pipe. There's a trade-off for this extra gain though, its Qp will be higher, as will its harmonic distortion, so will require more stuffing for best performance.
WRT a 'straight up' TL calculator, many moons ago I posted an Alpha TL Excel spreadsheet based on Rick Shultz's formulas, which I believe were an extension of G.L. Augspurger's work and the one I used. For a more flexible designer that allows tapering and driver location at other than the closed end of the line, download MJK's Classic TL paper and make your own calculator.
WRT the Titanic, for Fp = Fs:
L = 168.31"
CSA = 73.963"^2 (~9.704" dia. or 8.6" square)
stuffing density w/ polyfil = 0.461 lbs/ft^3 (53.13 oz total)
Max pipe size = ~20.2" dia.
GM
Conventional wisdom says use a pipe of ~the same CSA as driver Sd, but it's BS and even the pioneer speaker designers knew this since it was well known from building pipe organs that the circumference of a pipe sets its LF cutoff, so to get around this humongous size required they put the driver in a big box and tapered it down to a big, long tube vent that was equal to ~Sd to keep acoustic efficiency fairly high. Somewhere along the line the box was reduced because as more power became available they didn't need so much box efficiency, then dropped altogether as the Vas of the drivers dropped (acoustic suspension era) and continues unabated today in the quest to get ever smaller cabs and why this ultra low Vas driver only requires a small pipe to load it properly.
So much for 'conventional wisdom'. It was ~valid at one time, but no longer unless a high Fp is desired or acceptable.
That said, the bigger the pipe the greater its gain up to a point of diminishing returns, which is around 4x Vas, so at ~7810.6"^3 for this driver, a ~9.2" dia. is the theoretical point of diminishing returns in a ~117.38" long pipe. There's a trade-off for this extra gain though, its Qp will be higher, as will its harmonic distortion, so will require more stuffing for best performance.
WRT a 'straight up' TL calculator, many moons ago I posted an Alpha TL Excel spreadsheet based on Rick Shultz's formulas, which I believe were an extension of G.L. Augspurger's work and the one I used. For a more flexible designer that allows tapering and driver location at other than the closed end of the line, download MJK's Classic TL paper and make your own calculator.
WRT the Titanic, for Fp = Fs:
L = 168.31"
CSA = 73.963"^2 (~9.704" dia. or 8.6" square)
stuffing density w/ polyfil = 0.461 lbs/ft^3 (53.13 oz total)
Max pipe size = ~20.2" dia.
GM
AndrewT said:
OK, my quest is to fill the gap into my home theater.
I cant realy fit anything into the listening room, but i can use the whole home basement to do it.
So my idea was to bolt the tl line right under the floor of the listening room, and could even use a 90 degree elbow and vent it behind the stereo/tv cabinet with a fake register...
so i want deep low loud bass...
the front loaded horn also seemed to me to be good because of the spl output it seems to make...
If i go this route, it will reside on the concrete floor, in one corner of the home basement.
I do believe fun happens with home cinema with 15hz thru 80 hz...
And, i dont have any idead as to what you means with "truncation, boundary,...".
thanks.
enormous horn for 15Hz
Hi,
for 15Hz you require a VERY big horn.
I'll give some numbers and you'll see the futility of bass and sub-bass horns.
Using two 18inch drivers and setting throat area = 2*Sd makes the horn shorter.
Using floor and wall loading i.e. putting the horn mouth up against a wall AND floor junction reduces the horn mouth by 75%. This also shortens the horn.
The horn length should be 8.3m (=27feet) and the mouth area= 20.8sqm (=224sq Feet).
If you truncate it (chop off the front end to make the horn shorter and the mouth smaller) by 50% then the horn length is 4.15m (=14feet) and the mouth area is reduced to 2.1sqm (=23sq Feet). That is still a big horn and the performance in the range 15Hz to 30Hz will be severely compromised. This truncated horn is too short, the minimum length is between 5.7m and 11m (quarter to half a wavelength).
One can either truncate less and add back in some of that big mouth or go to the small end and make the throat smaller (this requires a lot less volume).
If you use one driver (throat =1*Sd), the horn will increase in length by 1.25m and if you reduce the throat to half of Sd then it will increase in length by a further 1.25m. The 50% truncated horn is now 6.65m (=22Feet) long (comfortably over 5.7m).
Do you have sufficient space in your floor for a mouth that size?
A 15Hz horn is only for incorporation into the design of the building not as an add-on.
A 20Hz horn is a lot smaller and 27Hz is very much smaller again, have a look at Tom Danley's Labhorn. Download his paper on designing the speaker for lot's of detail.
Hi,
for 15Hz you require a VERY big horn.
I'll give some numbers and you'll see the futility of bass and sub-bass horns.
Using two 18inch drivers and setting throat area = 2*Sd makes the horn shorter.
Using floor and wall loading i.e. putting the horn mouth up against a wall AND floor junction reduces the horn mouth by 75%. This also shortens the horn.
The horn length should be 8.3m (=27feet) and the mouth area= 20.8sqm (=224sq Feet).
If you truncate it (chop off the front end to make the horn shorter and the mouth smaller) by 50% then the horn length is 4.15m (=14feet) and the mouth area is reduced to 2.1sqm (=23sq Feet). That is still a big horn and the performance in the range 15Hz to 30Hz will be severely compromised. This truncated horn is too short, the minimum length is between 5.7m and 11m (quarter to half a wavelength).
One can either truncate less and add back in some of that big mouth or go to the small end and make the throat smaller (this requires a lot less volume).
If you use one driver (throat =1*Sd), the horn will increase in length by 1.25m and if you reduce the throat to half of Sd then it will increase in length by a further 1.25m. The 50% truncated horn is now 6.65m (=22Feet) long (comfortably over 5.7m).
Do you have sufficient space in your floor for a mouth that size?
A 15Hz horn is only for incorporation into the design of the building not as an add-on.
A 20Hz horn is a lot smaller and 27Hz is very much smaller again, have a look at Tom Danley's Labhorn. Download his paper on designing the speaker for lot's of detail.
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