Currently I have my adire Tumult rocking in a bass reflex enclosure, but I've gotten bored and have decided to do an entirely new project. I am considering either a TL or horn loaded enclosure for my new project.
Project Goals:
Flat response to 10hz in room at the highest SPL possible.
With that in mind I am strapped on the decision between a transmission line and a horn loaded enclosure. From my understanding the horn should give me higher SPL and if designed properly, lower frequency response. I also had an idea for a horn which I havent yet seen on the internet. Give some ideas/reasons to go with one enclosure or the other. Size is really not a factor, though I'd like to stay under 4 4'x8' sheets of MDF due to weight issues and material cost. My horn idea is shown in the attached picture below. Could these loadings give me even lower frequency extension with proper tuning? I know impulse response would be comprimised, but I'm willing to do that.
Project Goals:
Flat response to 10hz in room at the highest SPL possible.
With that in mind I am strapped on the decision between a transmission line and a horn loaded enclosure. From my understanding the horn should give me higher SPL and if designed properly, lower frequency response. I also had an idea for a horn which I havent yet seen on the internet. Give some ideas/reasons to go with one enclosure or the other. Size is really not a factor, though I'd like to stay under 4 4'x8' sheets of MDF due to weight issues and material cost. My horn idea is shown in the attached picture below. Could these loadings give me even lower frequency extension with proper tuning? I know impulse response would be comprimised, but I'm willing to do that.
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Neither configuration will work as the acoustic load of the horn will swamp the tuning of the reflex system in a horn long enough to work to the sub bass. Forget flat to 10Hz, that would take a 28 foot horn, and room lift makes it unnecessary anyway. A horn flat to 30-35 Hz or so is plenty, room lift will supply the rest.
6cubic feet tuned to 10hz gives me a very shallow rolloff of 6db/octave anechoic. 10hz is -12db. How would a big horn compare to that? How would the horn's acoustic load "swamp" out the tuning frequency. I'm talking flat to 10hz in room, not anechoic. Typical horns use a horn loaded sealed enclosure, my design would use a horn loaded bass reflex enclosure. I dont see how the tuning frequency of the box would be changed as the port length area and box volume are not effected by horn loading. I think the horn would just provide higher dampening?
No. If I did I would have already done so. When I prototyped my Tuba 24 I tried it, since it does work in my DR horns (that go to 80Hz fc). It took me a while to figure out why it didn't work. Even with my DRs I found that with an fc below 100 Hz you can't put the vent at the horn throat, as the mass of the air column in the horn dominates the system, and the vents have to exit into the horn at least 1/2 way down the pathway. With a large bass horn the air column mass is so great that using a vent to tune the system lower than a sealed rear chamber is counter-productive; if anything raising the system resonance is required.
Good idea Simon, but who knows what effect that may have on the horn's response, except maybe Bill... Have you tried this before Bill? I do see how the horn could add apparent length onto the port. I suppose there arent a whole lot of standard equations and/or modeling software for such a situation to play around with. So basically if I did have a port exit into the compression chamber or throat it would effectively lower the tuning frequency by some unknown amount? If the horn were loaded with a reflex port that exited outside the horn and not into the horn I'd imagine the port tuning wouldnt be effected, but since the horn changes the response of the cone of the driver it would also change the output of the port.
You can exit the port outside the horn but if the horn is making the driver run at 1/2 its normal fs anyway then the port is moot. A ported rear chamber is fine on a short horn to extend bass response below fc, as in an A7 for instance, or one of my DRs, but when the horn is sufficiently large, as is the case in any true bass horn, the system f is too low for the port to be of benefit and a sealed rear chamber is the better way to go.
To see how it models imagine your rear chamber is 2 cuft, and the horn loading has lowered the system f to 10 Hz. Now try modeling your driver in a 2 cu ft enclosure tuned to 10 Hz and then try to figure out where to put all that duct length.
To see how it models imagine your rear chamber is 2 cuft, and the horn loading has lowered the system f to 10 Hz. Now try modeling your driver in a 2 cu ft enclosure tuned to 10 Hz and then try to figure out where to put all that duct length.
Umm.... I did say size was no problem here really, just wanted to keep the cost of the materials under about 100 dollars and for $20/ sheet of MDF and liquid nails + screws I'm looking at about 4 4x8 sheets of MDF to work with and pleanty of screws and liquid nails to hold it together. WinISD shows that a Tumult would require a 17' port 4"x4" to achieve 10hz tuning in a 2cubic foot enclosure.... That is getting excessively long, but can be done and if it is folded at unequal lengths resonances in the port shouldnt be a large problem. Cant I use a larger rear chamber than 2 cubic feet? At 6 cubic feet my 10hz port is only 9 feet, still long, but reasonable. The port has 4 folds. What sort of response would I get with a sealed horn configuration at 10hz in room. If It isnt better than my ported box then perhaps I shouldnt even change the setup. Would a TL get me down there?
I was being facetious. You don't want to tune to 10Hz. How big is your room? Cabin gain at 12dB/octave starts where the longest dimension is 1/2 wavelength; with a 24 foot long room that's 24Hz, so there's no point in having the fc or the fb any lower than that, and higher still is called for with a smaller room. Then there's the matter of content; power requirements below 35 Hz drop precipitiously, so between room lift and the diminishing demands of the program content that makes a 35 Hz horn adequate for all but the largest of spaces.
Currently I have the sub in my living room for HT use, but I plan to move it to the basement of my shed. The basement is currently a 24'x24' room with concrete walls on 3 sides plus a full concrete floor and ceiling. I plan on building a wall however to seperate the room into 2 parts and make one a recording studio, but that may be months down the road and I have no detailed plans. I kinda had the crazy idea to get the maximum possible SPL @ 10hz in room. Flat to 10hz would be nice, +db @ 10hz would be nicer!
I'd have the parthenon, beleieve me, but the funds are a little short. Currently I have my Tumult in 6cubic feet tuned to 10hz and trust me there is LOTS of output down there. (the windows visibly flex, everything rattles, the lights flicker, curtians blow in the "wind") But I just felt like perhaps more output could be achieved. A horn or TL seemed like a good place to go, as the horn is known for its high efficiency and the TL is known for its extension down low among other things. Honestly I've never built a TL period, and I've only constructed one horn, which I modeled after another design. I suppose the idea of amazing SPLs at infrasonic frequencys is something practical only for the car audio enthusiast. I wonder if the adire parthenon can be mounted in any sort of baffle/enclousre. I know what they show on their site is only the driver itself and the only suspension is spiderlike. But I'd imagine they have some sort of surround developed for use in baffles. Anyhow, I'm thinking I may just construct a standard horn. I think 30-35hz would probably adequate as bill said, but I'm going to aim for 25 or lower. I've heard Hornresp is a quite usefull so I'll give that a whirl. If anyone else has something on their mind feel free to chime in
Well, I just downloaded HornResp and to say the least, I'm not lovin it. Not quite as user friendly as say WinISD. Basically I have no idea what I'm doing here. The program seems pretty guess and check, but I have no idea where to begin. Also all these new parameters I must enter are getting confusing. What is CIR? "Exponential or hyperbolic-exponential horn mouth circumference in flare cutoff frequency wavelengths"
I really need some pointers on this, anyone help
I really need some pointers on this, anyone help
go to the menu and say HYPEX
Put your mouse over an unknown box,it tells u down the bottom
Make compression ratio no more than 2.5:1 and probably the cone WONT break.
Make mouth something you can fit,even if rectangular in shape.
The loading conditions will make a large effect,have you got a corner free?
a 24hz horn is possible if you can fit a LABHORN sized enclosure with a 1metre mouth extension that extends up the wall to the ceiling. The output at 10hz wont really be much more than a sealed box because the horns only long enough for ~28hz.
http://www.diyaudio.com/wiki/index.php?page=basshorn
www.volvotreter.de 'downloads' dinsdale horn design
CIR should be >1 ,but it probably is less than this.
Example
Put your mouse over an unknown box,it tells u down the bottom
Make compression ratio no more than 2.5:1 and probably the cone WONT break.
Make mouth something you can fit,even if rectangular in shape.
The loading conditions will make a large effect,have you got a corner free?
a 24hz horn is possible if you can fit a LABHORN sized enclosure with a 1metre mouth extension that extends up the wall to the ceiling. The output at 10hz wont really be much more than a sealed box because the horns only long enough for ~28hz.
http://www.diyaudio.com/wiki/index.php?page=basshorn
www.volvotreter.de 'downloads' dinsdale horn design
CIR should be >1 ,but it probably is less than this.
Example
Attachments
heart palpatations? What I dont get here is why hornresp doesnt use hardly any of the t/s parameters and somehow its supposed to give me frequency response?- Status
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