Do you even read what people are posting for you?
http://www.diyaudio.com/forums/subwoofers/190832-bill-fitzmaurice-designs-question.html#post2607405
http://www.diyaudio.com/forums/subwoofers/190832-bill-fitzmaurice-designs-question.html#post2607405
Another interesting topic is the one called "Heat exchanger effectiveness", which talks about the cooling system used in the 12Pi hornsub, including power/thermal tests. It has a destructive test of a LAB12 woofer, where power was applied to the driver for an extended period, temperature measurements taken, and then power was slowly increased to the point of failure, taking measurements at each incremental increase. The same series of tests were run with a modified LAB12, one that has the cooling plug and plate installed. The amount of sustained power increased over 225%, and the driver never failed. This was also proven in the field, time and time again, in the controlled tests performed at the Prosound Shootouts in 2005, 2006 and 2007.
I think that any discussion of SPL, distortion and/or thermal power handling where comparisons are made should be accompanied by measurements that rise to this level. We did measurements at various power levels, from 100 watts to over 2000 watts, and we measured both SPL and distortion. Not everyone has the equipment or location to perform such a test, but comparison between subs like this can't really be made without at least a few high-power sweeps made outdoors, far away from buildings or other large reflective surfaces.
I think that any discussion of SPL, distortion and/or thermal power handling where comparisons are made should be accompanied by measurements that rise to this level. We did measurements at various power levels, from 100 watts to over 2000 watts, and we measured both SPL and distortion. Not everyone has the equipment or location to perform such a test, but comparison between subs like this can't really be made without at least a few high-power sweeps made outdoors, far away from buildings or other large reflective surfaces.
similar testing but different approach.
http://www.decware.com/techdb.htm
"The Death Box was originally a study in power handling. We studied why woofers blow up, especially in band pass boxes and in the process optimized a design to minimize the negative effects of abuse.
We built and tested over 80 revisions of the classic band pass box to improve power handling and SPL. This lead to eliminating the typical port and replacing it with a symmetrically perfect duct system that kept internal pressure evenly distributed on the woofer cone.
We also found cabinet resonance would excite the woofer in negative ways and reducing them improved performance."
DECWARE / The Death Box - High Output Subwoofer Cabinet
http://www.decware.com/techdb.htm
"The Death Box was originally a study in power handling. We studied why woofers blow up, especially in band pass boxes and in the process optimized a design to minimize the negative effects of abuse.
We built and tested over 80 revisions of the classic band pass box to improve power handling and SPL. This lead to eliminating the typical port and replacing it with a symmetrically perfect duct system that kept internal pressure evenly distributed on the woofer cone.
We also found cabinet resonance would excite the woofer in negative ways and reducing them improved performance."
DECWARE / The Death Box - High Output Subwoofer Cabinet
Interesting that the study you referenced mentions changing vent size. That's a real issue - the size and shape of the cooling vent(s), and the position and interface to the gap. It's very much like tuning the intake and exhaust of a car.
I began going in that direction, and there are some early discussions about a ducting system I first used. But ultimately, in my specific application, since the cabinet I was using reduced excursion, the venting was just not very effective. Most of the heat was being transferred and stored in the magnet and pole piece, so wicking it out gave the largest thermal improvement.
I began going in that direction, and there are some early discussions about a ducting system I first used. But ultimately, in my specific application, since the cabinet I was using reduced excursion, the venting was just not very effective. Most of the heat was being transferred and stored in the magnet and pole piece, so wicking it out gave the largest thermal improvement.
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I have distortion charts of the Keystone sub with Lab 12s, 4015Lf, and BC18SW115-4.
The results are in post #12 of
http://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers.html
My laptop was out for repair at the time, so I had not posted screen shots, and there seemed to be little interest in distortion, so I had not posted more info.
I will post the screen shots there tomorrow, have to leave for a 1 PM stage call.
This thread had a lot of distortion testing, and also seemed to generate little interest:
PSW Sound Reinforcement Forums: LAB Lounge => JBL SRX718 - Basic Distortion Measurements
Yeah, the PSW guys seem to have very little interest in distortion. I've even seen 'em post sub measurements done indoors. Not much help there.
I was looking for something more like the LMS charts, done outdoors at fairly high power levels and distance, like 10 meters. I really don't see comparible measurements in your thread. What system was used to measure? What signal was used? What was the method of measurement?
I was looking for something more like the LMS charts, done outdoors at fairly high power levels and distance, like 10 meters. I really don't see comparible measurements in your thread. What system was used to measure? What signal was used? What was the method of measurement?
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One thing I have to add before we go too much further. I feel the need to say a "sanity check" is in order. Somewhere, we are definitely not talking apples and apples here. I'd say it's not even apples and oranges, more like apples and basketballs or something, not even in the same ballpark. You seem to have said that a pair of LAB12 woofers in a vented cabinet run at 400 watts each (800 total) generated only about 6-7% distortion. Distortion from a direct radiating LAB12 run at 400 watts is way higher than that.
The LAB12 woofer is a pretty good part, but at those power levels, a direct radiating LAB12 generates over 10x that distortion. At the lowest frequencies, it's above 100% THD at 400 watts. In fact, if you run it continuously at that power level for more than about an hour, the voice coil will fail. So somehow or another, we're not talking the same language here.
The LAB12 woofer is a pretty good part, but at those power levels, a direct radiating LAB12 generates over 10x that distortion. At the lowest frequencies, it's above 100% THD at 400 watts. In fact, if you run it continuously at that power level for more than about an hour, the voice coil will fail. So somehow or another, we're not talking the same language here.
I like push-pull, I converted a rather boomy pair of Cerwin Vega PA boxes into a single Isobarik push-pull sub with passive radiator tuned to 21.5Hz. Both those rather odd "tricks" to control cone motion below Fs. (It works well, sounds good to me and my buddies and reality trumps theory why it won't)
Really like push-pull but the heat tube for additional voice coil cooling is interesting. AFTER I learn Horn Response, I'll built a TH with a single 10" woofer I have laying around. The ten has a vented VC so I'll make a extension tube for it but with a literal twist. I was thinking of curving the tubing and thermal epoxy to glue it to a curved piece of aluminum sheeting. The aluminum sheeting will be wrapped around the magnet to secure it and I figure a 6 to 8 inch length of tube with open end should pull the heat out of the coil. By curving the tube, it should "scrub" the heat off better than straight so I won't need to restrict the end.
My 10" sub has decent Xmax (10mm) but the VC needs some help. Figure a thin walled tube, thermal epoxy and aluminum sheet wrapped around the magnet should do it. I'm not asking for twice the power handling, just want to keep the thing cooler since garage sound involves beer, high volume and long summer nights. IF it works well, then the eventual 18Hz dual 12" push-pull tapped horn will run that concept.
If it don't work well, at least it is easy to remove and no harm done.
Really like push-pull but the heat tube for additional voice coil cooling is interesting. AFTER I learn Horn Response, I'll built a TH with a single 10" woofer I have laying around. The ten has a vented VC so I'll make a extension tube for it but with a literal twist. I was thinking of curving the tubing and thermal epoxy to glue it to a curved piece of aluminum sheeting. The aluminum sheeting will be wrapped around the magnet to secure it and I figure a 6 to 8 inch length of tube with open end should pull the heat out of the coil. By curving the tube, it should "scrub" the heat off better than straight so I won't need to restrict the end.
My 10" sub has decent Xmax (10mm) but the VC needs some help. Figure a thin walled tube, thermal epoxy and aluminum sheet wrapped around the magnet should do it. I'm not asking for twice the power handling, just want to keep the thing cooler since garage sound involves beer, high volume and long summer nights. IF it works well, then the eventual 18Hz dual 12" push-pull tapped horn will run that concept.
If it don't work well, at least it is easy to remove and no harm done.
I was thinking I could of swore I posted that...
So 60, you going to play around with the program? I read that thread awhile back and the evil seed was planted. The TH project is in the "cue" and is slated for July/Aug time frame.
The cool thing about Horn Response is you can plot one, two, four or more tapped horns and calculate hassle VS weight VS price etc to get what you want. Sixteen 6.5" tapped horns will give you 25 Hz at 102dB at one watt--handle over 1,000 watts (over 130 dB) and easy to rack N stack. They are available in "flat packs" with the wood pre-cut, routed and holes drill for the screws.
Cost is around $3K for 16 of them but much cheaper than the medical bills for a blown back! 😱
So 60, you going to play around with the program? I read that thread awhile back and the evil seed was planted. The TH project is in the "cue" and is slated for July/Aug time frame.
The cool thing about Horn Response is you can plot one, two, four or more tapped horns and calculate hassle VS weight VS price etc to get what you want. Sixteen 6.5" tapped horns will give you 25 Hz at 102dB at one watt--handle over 1,000 watts (over 130 dB) and easy to rack N stack. They are available in "flat packs" with the wood pre-cut, routed and holes drill for the screws.
Cost is around $3K for 16 of them but much cheaper than the medical bills for a blown back! 😱
As it seems you are also a Christian, let me say this before my recommedation:
The Lord helps those who help themselves.
Give a man a fish and he eats for a day. Teach a man to fish and he can feed himself for life.
Do you feel ok "begging for fish" everywhere you go because you have "poor fishing(math) skills"?
Now for my recommendation: If you show some initiative in figuring out dimensions for one of the "keystone" designs, you will find people coming out of the woodwork to guide you to a successful build. This is likely to be the only single-box design that will work with such a cheap driver.
The Lord helps those who help themselves.
Give a man a fish and he eats for a day. Teach a man to fish and he can feed himself for life.
Do you feel ok "begging for fish" everywhere you go because you have "poor fishing(math) skills"?
Now for my recommendation: If you show some initiative in figuring out dimensions for one of the "keystone" designs, you will find people coming out of the woodwork to guide you to a successful build. This is likely to be the only single-box design that will work with such a cheap driver.
Build JBells 30 Hz tapped horn
It works, it's proven, very high quality and you won't have problems with it. The issues is what you are asking generally are not available in PA subwoofers--30Hz outside! Not in a corner, not in a building--outside! Can I only use ONE of them? 😱
I understand what you want it for--that odd gig that folks want to be blown away with deep bass. The times are a changin' so having the 30 Hz capability makes a lot of sense, music is not returning to the vinyl 60's... (I have an 18 year old son and my HVAC rattles when frequencies in the 20 to 30Hz range hit my subwoofer)
A giant sub also pleases the aesthetics requirement for the crowd. 20 years ago I did PA and many people loved that 9 foot stacked speakers (although generally, only 6.5 feet of them were actually on) They liked the look, I had spares if I needed them.
I'm 46 and did the schlepping around 157 pound cabinets 15 years ago--you only have one back. Since my goal is 130 dB at 18 Hz out doors (hence my name) I need to learn, live and love horn response! I'm very aware that what I want borders on insanity but it's not for music, it is not for indoor use, I don't care if the response dies at 50Hz. It must be low distortion and I have to be able to move and assemble it by itself.
The "Zombie Horn" project seems to be close to impossible, yes--it has to run off one 120V 15 amp outlet--but I keep reading all the crazy stuff JBell does and have ideas.
That might be what you're looking for--30Hz for outdoor use using two horns and a "mouth extender" plate. It will give you the deep bass, the output and the lethal look of a beast. On the positive side, it should be able to be moved by one person. Each box should weigh less than you and they can be bass bins with tops when not run in deep bass mode with plate.
So far, JBell's 30 Hz tapped horn seems to be what you want. The other option is linking two horns together and the mouth extender plate (in theory) On the good side of things, there are actual plans to get what you specify. They have to be followed to the letter and the drivers are not cheap--but what you want ain't cheap anyway. After all, blowing $200 plus on wood, connectors, glue, carpet, paint, edge hardware, handles, wheels etc before you even get to the driver...it puts things in perspective.
It is rare to find a horn design that uses both an inexpensive driver or an expensive one as an option. Blow up the $70 driver and you're stuck--the box needs to be redesigned to fit the specs of the expensive driver. Horn Response will tell you what you want to know, what it will do with any speaker. Maybe two tapped horns with $60 JBL GTO car subwoofers will work--in theory.
Good luck!
It works, it's proven, very high quality and you won't have problems with it. The issues is what you are asking generally are not available in PA subwoofers--30Hz outside! Not in a corner, not in a building--outside! Can I only use ONE of them? 😱
I understand what you want it for--that odd gig that folks want to be blown away with deep bass. The times are a changin' so having the 30 Hz capability makes a lot of sense, music is not returning to the vinyl 60's... (I have an 18 year old son and my HVAC rattles when frequencies in the 20 to 30Hz range hit my subwoofer)
A giant sub also pleases the aesthetics requirement for the crowd. 20 years ago I did PA and many people loved that 9 foot stacked speakers (although generally, only 6.5 feet of them were actually on) They liked the look, I had spares if I needed them.
I'm 46 and did the schlepping around 157 pound cabinets 15 years ago--you only have one back. Since my goal is 130 dB at 18 Hz out doors (hence my name) I need to learn, live and love horn response! I'm very aware that what I want borders on insanity but it's not for music, it is not for indoor use, I don't care if the response dies at 50Hz. It must be low distortion and I have to be able to move and assemble it by itself.
The "Zombie Horn" project seems to be close to impossible, yes--it has to run off one 120V 15 amp outlet--but I keep reading all the crazy stuff JBell does and have ideas.
That might be what you're looking for--30Hz for outdoor use using two horns and a "mouth extender" plate. It will give you the deep bass, the output and the lethal look of a beast. On the positive side, it should be able to be moved by one person. Each box should weigh less than you and they can be bass bins with tops when not run in deep bass mode with plate.
So far, JBell's 30 Hz tapped horn seems to be what you want. The other option is linking two horns together and the mouth extender plate (in theory) On the good side of things, there are actual plans to get what you specify. They have to be followed to the letter and the drivers are not cheap--but what you want ain't cheap anyway. After all, blowing $200 plus on wood, connectors, glue, carpet, paint, edge hardware, handles, wheels etc before you even get to the driver...it puts things in perspective.
It is rare to find a horn design that uses both an inexpensive driver or an expensive one as an option. Blow up the $70 driver and you're stuck--the box needs to be redesigned to fit the specs of the expensive driver. Horn Response will tell you what you want to know, what it will do with any speaker. Maybe two tapped horns with $60 JBL GTO car subwoofers will work--in theory.
Good luck!
How small could you design and build a 35hz subwoofer?
try to avoid lengthy responses that dont actually answer the question 😉
for use with a portable 12v system,
if you were asked to throw an idea out there (box and driver)
how would you go about designing and building the smallest 35hz subwoofer.
not too loud, lets say normal tv listening volumes, but with the ability to deliver real 35hz accurately,
and small as possible. (no bigger then a shoebox)
im almost tempted not to post this question, its only intended as fun, but im sure some will give non fun responses about math and hornresp and corners.
go on, have a little fun.......
try to avoid lengthy responses that dont actually answer the question 😉
for use with a portable 12v system,
if you were asked to throw an idea out there (box and driver)
how would you go about designing and building the smallest 35hz subwoofer.
not too loud, lets say normal tv listening volumes, but with the ability to deliver real 35hz accurately,
and small as possible. (no bigger then a shoebox)
im almost tempted not to post this question, its only intended as fun, but im sure some will give non fun responses about math and hornresp and corners.
go on, have a little fun.......
if i build a monster, im building just one.
i have the idea that a $160 800 watt dayton driver will give me more of everything then the $70 MFW 15.
its just matching the ts params to the TH and designing the box.
you wanna check these calcs and gimme a 3D image of how to build the box?
i have paypal and am happy to pay for peoples time
http://img862.imageshack.us/img862/2115/60ndownth.jpg
i have the idea that a $160 800 watt dayton driver will give me more of everything then the $70 MFW 15.
its just matching the ts params to the TH and designing the box.
you wanna check these calcs and gimme a 3D image of how to build the box?
i have paypal and am happy to pay for peoples time
http://img862.imageshack.us/img862/2115/60ndownth.jpg
This is my beach radio....12 volt powered. 😉
yes thats (2) ss15's, (2) deka 904 d batteries, (2) solar panels, (2) cooling fans, (2) alpine pdx amps etc etc. (pioneer usb head unit, eminence beta 8a midranges, pyle sealed back midranges, horn tweeters) this thing rocks the beach!!
the second (black) ss15 was never meant to be used with the beach radio...BUT, i liked the kick so much better with the second cabinet added that i decided it HAD to come to the beach with me lol
yes thats (2) ss15's, (2) deka 904 d batteries, (2) solar panels, (2) cooling fans, (2) alpine pdx amps etc etc. (pioneer usb head unit, eminence beta 8a midranges, pyle sealed back midranges, horn tweeters) this thing rocks the beach!!
the second (black) ss15 was never meant to be used with the beach radio...BUT, i liked the kick so much better with the second cabinet added that i decided it HAD to come to the beach with me lol
I know this is totally not what you want, but it shows the possibility of 12v powered stuff 🙂
I would start with the tang band 6.5" subwoofer. it has the xmax that will actually let you hear (maybe feel) 35 hz in a small package. I have two of volvotretters 38hz tang band double folded horns in my living room. bigger than a shoebox, yes, but they are great for mini subs!
I would start with the tang band 6.5" subwoofer. it has the xmax that will actually let you hear (maybe feel) 35 hz in a small package. I have two of volvotretters 38hz tang band double folded horns in my living room. bigger than a shoebox, yes, but they are great for mini subs!
The SPL plot shows a nice Response but check the impulse behaviour (HornResp - SPL response - "tools" - impulse - response).
Also check Group delay (HornResp - Window - 8 Group Delay).
That are the worries for this driver...
Also check Group delay (HornResp - Window - 8 Group Delay).
That are the worries for this driver...
Shoebox is bordering on too small to keep up with "normal tv listening volumes" and deliver flat to 35 Hz, unless you are talking about NFL basketball player shoe boxes, or "normal tv listening volumes" means only 75 dBC or so.
I have a "breadbox" size sub I use in my little Casita travel trailer that runs off a tiny 12v power amp, it is flat to about 40 Hz, and uses an 8" 8 ohm Radio Shack driver IIRC. The sub keeps up well with a pair of 4 ohm speakers I cut out of some ghetto blaster, which actually sound OK run off an Ipod headphone output.
There are a lot of very small, low FS drivers available now that may satisfy your request, but you need to define some actual dB levels and cubic foot dimensions, and the power of your 12v amp to see what would work.
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