Almost looks too simple - that's why I was wondering if the folding scheme is inherently flawed for this kind of SPL. I've used it with 15's in smaller boxes going down to 40 in a 4-pack. The drivers were the limting factor in that set of subs. But it looks like it might work for a flat-to-30 6-pack in this Bertha form factor. Or 4 boxes with barn doors. Or 6 with really big barn doors. Or V-plated in a 6-pack. Each arrangement seems to have thier advantages in where the excursion minima line up. It would likley work with any 21" with a BL above 30 - may require adjustment to the rear chamber. But now it's only in the 'play around with a couple sheets of OSB' stage. 18's want a narrower version with more boxes, which was what I was originally looking at.
That's an expensive ride 6 X 18" narrower cab AND amps? Have you simulated any 18" woofers preferably cheaper 18" Faital Pro Neo HP 1020 type is on my list? Thanks wg_ski!
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I have four 18TBW100 on hand. They live in my TH18s, but I can take them out to experiment with new designs. They simulate well in a 24" wide version, in a group of 6 or 8. That's the whole reaspn I went with the TH18 and the TBWs for my 'practical' rig - to have the right drivers on hand when building the big one down the road. What I was originally thinking about was replacing some old lab horns with something equivalently sized, but with drivers that can handle more than 200 watts RMS. The labs were the bomb when all I had was some old USA1310's. I acquired some used CA18's about 5 years ago, and bought a couple RMX5050's. As long as I'm running on a headroom basis the system holds up fine. Sounds great with undistorted music. But it would be cool to have a 30 Hz system I could really push with the bigger amps and get another 10dB. Not that I NEED it or anything... And with the wider cab option and barn doors, the 21's start to look mighty attractive.
That's what I am saying 6 X 24" wide cabs per side would be a mean sub system and 12 18" woofers AND amps? $$$$ Well I was thinking down the road of replacing the Bertha's PD2150 with 18Sound 21/9001 neo's. Have you simmed the 6 X 24" cabs with your B&C TBW? Thanks!
One driver per cab. Two 18's (4 ohm) or one 21 (8 ohm) on a CA18 or QSC5050. Two 18's in even a 28" wide cab is "too much driver". If the driver and box aren't matched properly, the efficiency suffers. You get the same SPL, but with a lower input impedance. Higher Z means less heat in the motors and amps. There's no point to going front loaded unless you can take advantage of the efficiency boost. If you don't, TH is just as good - and better if you undersize. I have simmed the simple prototypes (offset driver with exponential flare) with 18's and 21's and the results look promising. I've narrowed down the box sizes, path length, mouth and throat which work best in both form factors. The necessary volume is there (700 or 900 liters), so it should be a matter of getting the flare close enough so that at 30-80 Hz the differences don't matter.
Sorry wg_ski Im kinda slow when it comes down to the nitty gritty, how do you arrive at 30 Hz how many cabs? With the mouths together will 2 cabs loaded each 21" 9001 neo will it hit 30 Hz 28" wide cab? OR 4 X 28" wide loaded with say Faital 1020 neo 18"? Thanks!
It takes 8 cabs 24" wide loaded with 18's to make it to 30Hz without the low end drooping. 6 cabs 28" wide will do the same, but those need two 15's or a 21. You can cut the stack size down and use a flare extension to get the same mouth area. To tune this correctly it needs to continue at the same exponential rate as the internal flare. Again, approximations are fine as long as it's close. This has the advantage of controlling cone excursuon a little better down low. This is because the path length is now longer. This is how the Levan doors work, and why they were such a big help. For 30Hz, this is the way to go. If highpassed at 40, it's best to use the whole stack with no extensions, because it moves the excursion minimum to a more favorable location.
I verified this for myself back in like 2002. I built my first two lab horns, and by themselves put out more than my two 2x18's. But they needed about 6dB of boost at 30-40 just to get flat, and another 5dB cut at 80 to get rid of a midbass peak. I read about flare extensions being used in fixed installs and put one together out of OSB in the front yard. I wanted to know how it would sound if I built the whole stack. Turned it from 'yeah, it's loud, but so what?' to 'OMG!!!, that's some deep BU-HASS!!!'. I proceed to build the rest of them.
If you want to build 2 28" wide cabs with your 21's definitley build the flare extensions. Doubling the frontal area (to equal the area of 4 cabs) won't quite equal 6 boxes, but it will be noticebale enough that you'll want to use them. Doing more than a doubling is certainly possible, but I wouldn't recommend it because you'll never get it rigid enough to stand up to those SPLs. A 'small signal' test like I did you can get away with it a little floppy.
I verified this for myself back in like 2002. I built my first two lab horns, and by themselves put out more than my two 2x18's. But they needed about 6dB of boost at 30-40 just to get flat, and another 5dB cut at 80 to get rid of a midbass peak. I read about flare extensions being used in fixed installs and put one together out of OSB in the front yard. I wanted to know how it would sound if I built the whole stack. Turned it from 'yeah, it's loud, but so what?' to 'OMG!!!, that's some deep BU-HASS!!!'. I proceed to build the rest of them.
If you want to build 2 28" wide cabs with your 21's definitley build the flare extensions. Doubling the frontal area (to equal the area of 4 cabs) won't quite equal 6 boxes, but it will be noticebale enough that you'll want to use them. Doing more than a doubling is certainly possible, but I wouldn't recommend it because you'll never get it rigid enough to stand up to those SPLs. A 'small signal' test like I did you can get away with it a little floppy.
LET"S DO IT ! I'll build the extensions too but how big is the extensions and can it be collapsible? And I am using the PD2150? Is that possible? Thanks wg_ski!
In the sims I was running, with about a 24 Hz flare rate the area should double in 77cm (30") of length. You're going to need a couple of 4x8 sheets and a lot of butterfly latches and straps. Stiffening ribs will be needed on the final assembly. Of course you want it collapsible - that's the whole point - not to take up truck space when it's mostly air. Build it out of junk wood first - same as you would with your prototype cab. If things don't work out or need adjustment you don't burn all your good birch ply.
When you do test it out you can give your neighbors a good pounding with only about 200 watts. It will bring you back to the Studio 54 days for sure.
When you do test it out you can give your neighbors a good pounding with only about 200 watts. It will bring you back to the Studio 54 days for sure.
Send it over wg_ski and let us look at it? I have 5 sheets of BB in the garage Ok I'll will build it with scrap ply LOL OR HOHOHO !
Her's a sim for the B&C 21. 48x48x29.5 external and makes good use of 4x8 wood (sim wants 904 liters without the flare extension, this should be enough). Note the main flare is just exponential - but if the approximation in 4 segments is good, it should turn out reasonable. I have it as an OD, because that's how I would build it. Try it with and without the last segment, in 2 to 8 boxes, with the B&C and the PD drivers. I have a similar one for an 18, just cuts the width down by 4" (but is even more wood-efficient with all the internal panels at 24"). oops, first one is wrong screen shot for a 21.
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Looks good, so from your sketch post 19 with 2 cabs mouths together in PD2150 loaded each I will get down to 30 Hz 48 X48 X 29.5 each plus extension? tnx
Again, the sketch in Post 19 is conceptual. The exact locations of the internal panels are still to be worked out. The idea is to move the endpoints of those 5 segments around until it reasonbly approximates the second (exponential) segment of the Hornresp sim. The path length I get is within a couple inches, and even taking internal panels and bracing (expect to lose 1.5" of width and 1.5-2" of depth) into account there is enough volume to do the job. It's just a matter of bending it till it fits. If you just threw it together, it would probably "work", but will certainly work best when the expansion is right. These FLHs, when stacked, are not THAT sensitive to the flare being exact. But if you cut down the volume or lose length is when you run into problems. A single lab horn pretty well sucks, two is useable, and at 8 all the 'wonkines' is just flat gone.
Build the number of cabs you expect to stack, then build the extension to work with the group. It's pretty good at 2, crazy SPL at 6. Three high and two wide would be almost square, so that would be ideal if you could swing it 🙂. Also, your PD driver will be somewhat different, but my experience is that if the BL and cone mass are close it will work. If not you need a different horn or driver. You may need to adjust the rear chamber size to move (the effective) fs, but 5 minutes in Hornresp and you'll be able to adjust it.
Build the number of cabs you expect to stack, then build the extension to work with the group. It's pretty good at 2, crazy SPL at 6. Three high and two wide would be almost square, so that would be ideal if you could swing it 🙂. Also, your PD driver will be somewhat different, but my experience is that if the BL and cone mass are close it will work. If not you need a different horn or driver. You may need to adjust the rear chamber size to move (the effective) fs, but 5 minutes in Hornresp and you'll be able to adjust it.
Any chance how to start the folds on this, I'm a newbie I also am interested in success and just curious how do you do the measurement on how much pressure the cone will receive at a certain power input? Like 200 watts don't want to break or tear the expensive new cone? Thanks!
wgski, your sim on this page is confusing to me..... that is a *massive* mouth. even in a stack of 6 it doesnt really dig below 40hz...
The conclusion I've come to is that if you want a real 30Hz, you're just not going to fit it all inside the box. Sure you can build a little TH that's flat to 30... at 90dB/W. I want 100, dammit.😀 And keeping it all in the 4x4 form factor results in 20+ mm excursion requirements at 30 Hz.
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