Hey guys...I do have a sub that is now being built by a cabinet shop after 6 months of simulating and planning that is very close to what is asked about in this thread. I have been thinking about it for a long time. In theory (Sim land) it will take 130v peaks (4 ohm nominal cab) without driver damage all of the way down to 14.5hz and should produce peak levels in the 120-125db range 16-40hz in half-space at 2 meters with more available on up from there. It is a TH with a 17-18hz effective knee with a gently sloping response that should be reinforced well by boundaries. The cab is externally 45x45x24". The thinking behind it was IMAX, Omnimax, commercial theater, or other LARGE spaces where deep extension is needed. I have need (Ok want) of a sub like that. My inspiration was the TH50 and the TH221. Whether or not it will actually perform anything like the simulation is the thousand dollar question. Who knows maybe the drivers will grenade or I made a major error in the math somewhere. I will be testing the finished pair in the summer along with a smaller 30hz knee 36x36x24" TH I am also having built for more regular SR type duty. Give me a couple of months and there will be a lot of data on the 2 for better or worse. The whole point to this long winded reply is that I think a cab like suggested by the OP is possible and I am trying to build it.
BTW thanks for the plug WelterSys.
BTW thanks for the plug WelterSys.
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Hey guys...I do have a sub that is now being built by a cabinet shop after 6 months of simulating and planning that is very close to what is asked about in this thread. I have been thinking about it for a long time. In theory (Sim land) it will take 130v peaks (4 ohm nominal cab) without driver damage all of the way down to 14.5hz and should produce peak levels in the 120-125db range 16-40hz in half-space at 2 meters with more available on up from there. It is a TH with a 17-18hz effective knee with a gently sloping response that should be reinforced well by boundaries. The cab is externally 45x45x24". The thinking behind it was IMAX, Omnimax, commercial theater, or other LARGE spaces where deep extension is needed. I have need (Ok want) of a sub like that. My inspiration was the TH50 and the TH221. Whether or not it will actually perform anything like the simulation is the thousand dollar question. Who knows maybe the drivers will grenade or I made a major error in the math somewhere. I will be testing the finished pair in the summer along with a smaller 30hz knee 36x36x24" TH I am also having built for more regular SR type duty. Give me a couple of months and there will be a lot of data on the 2 for better or worse. The whole point to this long winded reply is that I think a cab like suggested by the OP is possible and I am trying to build it.
BTW thanks for the plug WelterSys.
You are welcome, Josh.
The OP has already stated the Lab Sub, slightly smaller than the sub you have under construction, is too large.
The 30hz knee 36x36x24" is still large at 18 cubic feet, and too high of a LF corner to satisfy the OP.
Having put several seconds of 110 and 120 V sine waves into the B&C18SW125-4, the B&C21SW125 (IIRC what you are using) should have no problem with 130V peaks.
Try some horn extenders when your TH are done, about one sheet of plywood gained 3 dB with my Keystone sub, and takes up very little space when broken down.
Art
That's the only way you're going to get the mouth and the path big enough - with some sort of flare extension. The core "box" may not have to be more than 10 or 12 cubic feet, but assembled it will need to be as big as a barn door. Speaker boxes, even horns, are mostly air. Hinge pins and butterfly latches can be your friends.
Flare extensions work on tapped horns
Good to know that, so when I build a subharmonic subwoofer, I can just add about a meter to the mouth with a fold up horn and gain extension and dB? I am assuming a 45 degree angle flare on the mouth of the tapped horn or would something different be a better solution?
Good to know that, so when I build a subharmonic subwoofer, I can just add about a meter to the mouth with a fold up horn and gain extension and dB? I am assuming a 45 degree angle flare on the mouth of the tapped horn or would something different be a better solution?
What you need to do with a flare extension is to calculate it as part of the horn. The taper rate needs to be correct both inside and outside the box - an abrbirtary flare may or may not give good results. If you want to load your driver(s) properly and get good power handling I wouldn't take chances here. If you're using an external flare, and it's going to be *big enough*, do the horn front loaded instead of tapped. The whole point of tapped horns is to get by with a smaller mouth, and you give up excursion to get it so I wouldn't do it with a 20 Hz horn.
I used them *once*. I originally built two lab horns to replace 8 large low tuned 18's. They did, but because the array was undersized, the rising response and ripple required a lot of EQ to fight, and it compromised power handling. So one evening I punched in some numbers into Excel to calculate the next couple segments at a 26 Hz hyperbolic flare to get to 3x the mouth area. Then cut up some OSB panels and pinned it all together. The result was the most amazing BUH-HASS I ever heard outside - from only 400 watts. I built 6 more cabs over the next two years and got rid of the flares.
I used them *once*. I originally built two lab horns to replace 8 large low tuned 18's. They did, but because the array was undersized, the rising response and ripple required a lot of EQ to fight, and it compromised power handling. So one evening I punched in some numbers into Excel to calculate the next couple segments at a 26 Hz hyperbolic flare to get to 3x the mouth area. Then cut up some OSB panels and pinned it all together. The result was the most amazing BUH-HASS I ever heard outside - from only 400 watts. I built 6 more cabs over the next two years and got rid of the flares.
Thanks for the tip, wg_ski
I'm sure putting a flare on a tapped horn would create many issues considering the driver is at the mouth--with the flare the mouth moves back. I have seen flares on FLH boxes and I assumed it was to drop them lower in frequency response.
Getting eager to build a horn, either tapped or FLH with a single 10" (Tangband WT-644F) I have laying around. Seems a FLH would be better than a tapped since I can make the box "two piece" with two tunings. A 4 foot x 2 foot x 2 foot box to fit in the back seat of the car and a folding flare to get extension after it gets to it's destination. My son ponders what a horn subwoofer would do in the back seat and I want to build a "garage sub" for the man cave. I guess to get both would be a front loaded horn with the flare, change the settings for back seat use then throw in the garage with the flare extension to get the response down into the low 20's (Fs = 32)
No need about WAF when the beast will sit in the garage--right?
I'm sure putting a flare on a tapped horn would create many issues considering the driver is at the mouth--with the flare the mouth moves back. I have seen flares on FLH boxes and I assumed it was to drop them lower in frequency response.
Getting eager to build a horn, either tapped or FLH with a single 10" (Tangband WT-644F) I have laying around. Seems a FLH would be better than a tapped since I can make the box "two piece" with two tunings. A 4 foot x 2 foot x 2 foot box to fit in the back seat of the car and a folding flare to get extension after it gets to it's destination. My son ponders what a horn subwoofer would do in the back seat and I want to build a "garage sub" for the man cave. I guess to get both would be a front loaded horn with the flare, change the settings for back seat use then throw in the garage with the flare extension to get the response down into the low 20's (Fs = 32)
No need about WAF when the beast will sit in the garage--right?
The Keystone sub is slightly smaller than the size you mentioned, F3 mid 30s. It works well wit a variety of drivers.
http://www.diyaudio.com/forums/subwoofers/184986-horn-extender-wave-guide-th.html
A waveguide I had sitting around added 3 dB across the entire pass band with no FR issues.
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A horn extender big enough to work for a 20-30 Hz horn could have a half dozen bags of potting soil put in it without changing the response much.
"Honey, I built a potting soil storage bin for you".
The garage would be great for a horn flare
Lay the sucker up in the rafters--use the roof for a flare?
Usually, using the room corner as the last portion of the horn is easier to design and implement, but if you want lug your sub into the rafters, more power to you.
Of course, "subharmonic" PA subs (what this thread is about) can't depend on any boundary loading other than the floor (ground) at each gig.
Design needs to be in 2 Pi. Floor is only thing you can count on.
Wave guides as an extender is interesting. I use to use them with my Cerwin EQ's.
So far I have either a 1600 plus Lt cabinet (TH221 clone)
that hits 20 Hz at 130 DB with cut off at 18 Hz with 60v. Or a 555 Lt TH21 using 72v to hit 20 at 113 DB. Really a 30 Hz sub. But 3 in the space of 1.
HR of Th221 @ 555 Lt
HR of Th221 (Black) Vs 3 Th21
Wave guides as an extender is interesting. I use to use them with my Cerwin EQ's.
So far I have either a 1600 plus Lt cabinet (TH221 clone)
that hits 20 Hz at 130 DB with cut off at 18 Hz with 60v. Or a 555 Lt TH21 using 72v to hit 20 at 113 DB. Really a 30 Hz sub. But 3 in the space of 1.
HR of Th221 @ 555 Lt
An externally hosted image should be here but it was not working when we last tested it.
HR of Th221 (Black) Vs 3 Th21
An externally hosted image should be here but it was not working when we last tested it.
Now your "smaller" cabinet is 2/3rd the size of a LabSub.
For as low as you want to go, large cabinets are a needed unless you have tons of power.
Designing the last section of the horn as a knock down extender can allow double the cabinet size with only a marginal increase in transport size.
3 of these will get you closer to 140dB from 30dB-up and save some space (~461L).
The design is by Xoc1. It uses the BMS 18N850v2 (16mm xmax). This post can be found here: http://www.diyaudio.com/forums/subw...at-30-ft30-pa-th-awesomeness.html#post2379086
Cheers,
Justin
The design is by Xoc1. It uses the BMS 18N850v2 (16mm xmax). This post can be found here: http://www.diyaudio.com/forums/subw...at-30-ft30-pa-th-awesomeness.html#post2379086
Cheers,
Justin
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Upper cut off being 50 Hz. Low cutoff 15-18 Hz.
Hi Crescendo,
While this is a nice design, with a -3dB point of 32 Hz it doesn't begin to fit this thread. It takes about 1000 L_net to get this driver to a F3 of 23 Hz, still not low enough unless FlipC changes his goals.
Regards,
Hi Crescendo,
While this is a nice design, with a -3dB point of 32 Hz it doesn't begin to fit this thread. It takes about 1000 L_net to get this driver to a F3 of 23 Hz, still not low enough unless FlipC changes his goals.
Regards,
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