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B&C 21" Tapped horn idea - Page 2

post #31 of 109
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

that's kind of synchronicity. i was just curious how it compared to a comparable ported enclosure
approximately the same tuning too.]

Looking at my bass reflex model on WinSD, this horn picks up about 11-12dB at 25hz when driven to similar excursion. That's sure enough more work with less motion alright.

I stopped by Lowe's today pricing materials. Good plywood is tough to come by, but they had some decent looking maple 3/4" for reasonable cost. Might it be just as well to make it out of 3/4 MDF? Given that I'm not exactly going to be lugging this particular horn around....

Also found the PL Premium, and I am supposing it's going to take a bucketful or two of that stuff!

Purchasing and putting together a cut & drill list to come.
post #32 of 109
Awesome to hear. Have you used the PL before?

Most people, me included, use more than they actually need the first time. Then after that you realize how much you actually need for joining.
post #33 of 109
Quote:
Originally Posted by LTD02 View Post

i just didn't want him to build a massive horn that reached low into the teens and then be disappointed because of spl limitations around 30hz. as you know, that is the wheelhouse for movie bass.

I don't get it - isn't well above reference level already?
Quote:
Originally Posted by cattskinner View Post

Might it be just as well to make it out of 3/4 MDF? Given that I'm not exactly going to be lugging this particular horn around....

Just loading and unloading a sheet is reason enough.

More than that, MDF is both heavier and less stiff, not to mention much weaker, than ply, which lowers the panel self-resonance freq, which then requires better bracing.

Re bracing, I agree with Bill Fitzmaurice that by far the optimal and easiest to implement is cross-bracing.

What I intend to do on my next box is drill 1" holes all the way through the box and slide in wood dowels.

Getting glue on all of the surfaces might be challenging/messy, but I've found that traditional bracing is way too time consuming on top of not being as effective.
post #34 of 109
"I don't get it - isn't well above reference level already?"

yeah. full re-directed reference is around 121db or so. run it a little hot or with some eq and it's close to maxing out.

here is an alternative that creates a little longer path length and has more extension.

you can see how the max spl (red droop) in this one falls fairly quickly as extension is increased.

it's the op's call as to where to make that tradeoff. i wouldn't suggest much more tradeoff than this one.

i didn't confirm the rear chamber size in this one. just to give another possiblity.




post #35 of 109
SO is this horn about a 22hz or how low did it come out to be?

All this 21 horn stuff always has me thinking about the DSL TH221. Dont think I could go any bigger than the external size of that horn. And yet this horn is a LOT bigger than that one. WOW.
post #36 of 109
it is tough to say what the frequency of a front loaded horn is.

one way is to look at the cone motion minimum. in this case, it is around 25hz.

another way is to eyeball the low corner. in this case, it would be around 20hz.

a third way is to eyeball a -3db point below the low corner. in this case, it would be around 18.5hz.

so any of those would describe this big horn. :-)

it is pretty big, but has a simple fold and doesn't have to be moved.

that is the tradeoff here--maximum performance, maximum size, minimum cost and complexity.

[the rear chamber is around 400 liters or so]
post #37 of 109
I know in WinISD the sealed box is quite small for a .7 Qtc and when jumping up to 12cuft it does not change a lot below 20hz. Maybe a 1db difference down near 10hz. But that being said does the horn just multiply that small margin that much more?

Would have thought in a FLH you would want to keep the sealed area for the driver around Qtc.7 or .6. I know this has nothing to do with a sealed. Just curious is all. Will have to start simulating again and figure the rest out.
post #38 of 109
Thread Starter 
Quote:
Originally Posted by noah katz View Post

...MDF is both heavier and less stiff, not to mention much weaker, than ply, which lowers the panel self-resonance freq, which then requires better bracing.

What I intend to do on my next box is drill 1" holes all the way through the box and slide in wood dowels.

Getting glue on all of the surfaces might be challenging/messy, but I've found that traditional bracing is way too time consuming on top of not being as effective.

Noah, that sounds like a good solution. I had already been contemplating making something like the snap-ties used in concrete forming made out of heavy ReadyBolt, nuts & washers, then rubberized. But I think I like your solution better.

And Thanks for the input on MDF. It's going to be well worth paying a lot of attention to the structural integrity of this cabinet. There wouldn't be much sense in building something like this and then never pouring the coals to it, would there? Definitely not a Romantic Background Music unit. It will need to be really solid. I do NOT want to build something like this and have it turn out crappy.

I haven't had much luck finding good baltic Birch around here, but I know a cabinet maker who might have some ideas, and gets his lumber direct.

What's your input on Maple? It seems pretty hard, and fairly void-free. Just not as many plies as I'd like.
post #39 of 109
chrap, the front loaded horn is in some sense increasing the area of the driver
to the area of the exit of the horn. with each movement, that much air
is moving back and forth. in this case, the mouth of the horn is about
three times larger than the cone itself, so it is kind of like having a
35" diameter driver with a medium strength motor in a sealed enclosure,
which would be optimized in a very big sealed enclosure vs. having a 21"
driver with a high power motor which is optimized in a relatively small
sealed enclosure.
post #40 of 109
the cabinet does not need to be barltic birch.

any decent relatively void-free ply will work
so long as it is well braced and there are
no air leaks.
post #41 of 109
Thread Starter 
Quote:
Originally Posted by LTD02 View Post


That is a clever looking alternative. Given a close call, I'd be tempted to opt for the slightly longer horn path. This just isn't the driver to pursue sub-20hz response with, but I wouldn't mind coming close.

Hmmmm ... and putting it together might prove a little easier in a couple of ways, given the sequence I'm thinking it will need to be built in (no small consideration; it won't leave a lot of room to work around once it starts to come together ). It's going to take a little planning. MORE than worth it, heh heh.
post #42 of 109
Thread Starter 
Quote:
Originally Posted by LTD02 View Post


it is pretty big, but has a simple fold and doesn't have to be moved.

that is the tradeoff here--maximum performance, maximum size, minimum cost and complexity.

Exactly what I'm after, and wouldn't it be a kick to give some of the really sexy expensive units maybe not exactly a run for their money, but at least be getting into their league with a poor-man's solution like this? Yeah I'm hooked.
post #43 of 109
chrap had a question that i chose to investigate in a simplistic fashion.

i went into winisd and changed the sd to 4800 on the 21sw115 driver,
then let winisd put it in a sealed enclosure with qts=0.707.

interestingly, sensitivity is sky high and the enclosure is HUGE,
so perhaps my 'theory' is at least partially accurate.

below is the 1w1m plot, 2pi space.

"Hmmmm ... and putting it together might prove a little easier in a couple of ways, given the sequence I'm thinking it will need to be built in (no small consideration; it won't leave a lot of room to work around once it starts to come together ). It's going to take a little planning. MORE than worth it, heh heh."

ok, great. it's not like it will take a ton of insight or work,
but i will double check the measurements and model tomorrow.

that folding pattern is actually what is used in most p.a. front loaded horns,
so don't give me any credit there.
yours is just a GIANT version, so you get more sensitivity and more depth.

"Exactly what I'm after, and wouldn't it be a kick to give some of the really sexy expensive units maybe not exactly a run for their money, but at least be getting into their league with a poor-man's solution like this? Yeah I'm hooked."

:-)

post #44 of 109
Thread Starter 
cool.gif
" it's not like it will take a ton of insight or work,
but i will double check the measurements and model tomorrow."

Those are some interesting results you got on WinISD!

I took your advice and checked the position I have in mind with a smaller sub, and the spot I have in mind works fine. It will fire into the room not far from the rear corner, roughly 2m from the center of the couch. Should be able to hear it from there., heh. It is fortunate it sounds good there because I'm just about limited to building in the very end of the adjacent room.

By planning the order things will need to go together I mean that I want to make doubly sure Yours Truly doesn't forget something and get 90% done only to realize I'd need to, say, turn it upside down to fasten something I'd forgotten mad.gif I'm a bit of a a scatter-brain when it comes to building, which is why I'm excited about this one.

Through my years of playing in dance bands, I'd had no experience with horns, and never had a clue what the guts of them looked like. I suspect I'll be learning more about them, as I'm toying with the idea of horn-loaded mains, now. It going to take a bit of an upgrade before the satellite part of the system can match this horn.
post #45 of 109
Quote:
Originally Posted by LTD02 View Post

the cabinet does not need to be barltic birch.

any decent relatively void-free ply will work
so long as it is well braced and there are
no air leaks.

Correct.

I was just looking at mechanical properties of wood species the other day ( Table 4-3 in http://www.conradfp.com/pdf/ch4-Mechanical-Properties-of-Wood.pdf ), and noticed that lucky for us, Doug fir is as stiff as the higher stiffness hardwoods at 2/3 of the density.
post #46 of 109
this one is a slight variation on the other one.

it employs a slight exponential expansion in order to increase
sensitivity and max spl in the excursion limited region around
25hz by a little.

of course, you'll want to double check all measurements.







post #47 of 109
With these bigger drivers, you're probably not going to want the driver firing vertical unless you want a lot of vertical vibration on the cabinet. Rubber feet will help with that, but there's also the issue of gravity pulling the motor out of its symmetrical range.

We should also run the numbers to figure out which rear volume will reactance annul the horn - doing this will balance on the pressure on each side of the driver at Fc, and reduce cone flexing which will be a bigger issue with this large diaphragm.

Also, drilling a hole in the wall means you've pretty much fixed the acoustic source of the subwoofer into your room. Room modes will dominate the perceived performance, so it's good to make sure you're picking a location that is optimal for your space. The best way to do that would be to move an existing subwoofer along that wall until you find the ideal location. Even then, the horn presents a complicated acoustic impedance to the room which will affect these simulated results.

I would also recommend lining the horn with absorptive material so you don't get the cavern effect at higher frequencies - this becomes more of an issue as you make the horn mouth larger and larger.


How high in frequency do you want the horn to go?

The simulation tools are modelling the behavior of a perfect plane wave traveling through the horn. At higher frequencies, the wavefront leaves the walls and starts to suck in....especially wherever there are parallel walls. If you have a ~24" wide horn path the entire length of the horn, then you're going to see a 1/4 wave suckout at 142Hz...there will be corresponding peaks to either side of that frequency too. The directivity of the driver (for lack of a better description) is also going to play games with the wavefront shape at the throat. With the proposed design, you're going to get some wonkiness in the 150Hz region...if you can get the throat such that the throat opening is equidistant from the circumference of the driver, then you'll get better coupling at the throat...

Bifurcating the throat of the horn can reduce the inside/outside pathlength difference which helps with high frequency extension, but that may not be an issue here. If you do it right, you might be able to reduce your bracing needs by balancing the pressure across the bifurcation panel....I'd have to sit down and run some numbers to see if that's doable with a simple build approach.

Also, it's a bit counter-intuitive, but the areas needing the most bracing will actually be at the mouth end. We think about higher pressures at the throat due to the compression ratio, but that is getting turned into a velocity that gradually changes to a pressure at the mouth. It's the pressure that will cause your cabinet walls to vibrate. The mouth is also the larger aperture, so the panels vibrate easier too.


So basic summary of some of these comments - does bifurcation simplify bracing requirements and reduce differential between inside and outside radius? Can the driver be mounted horizontally such that the throat opening is centered on the driver?

And one other thought....

What about having two mouth openings? You could achieve two acoustic sources in your room with one driver, and possibly mitigate some of your horizontal room modes. There was a thread somewhere that talked about a "dual zoned bass array" or something to that effect.....the approach mentioned in that document used multiple drivers, but you can achieve the same with multiple mouth openings and a single driver....

I won't be able to reply to this thread for 3 weeks, but I'm very curious to see where you end up. There's lots of guys around here that can help out with some of these topics and maybe point to some other threads too. It's not often that a build has such design freedom.....whereabouts you live anyway? (Just wondering when the demo is, haha).

Btw, you should be using 1/8 space in hornresp....the room is technically smaller than that, but that's the best hornresp will do.
post #48 of 109
"With these bigger drivers, you're probably not going to want the driver firing vertical unless you want a lot of vertical vibration on the cabinet. Rubber feet will help with that, but there's also the issue of gravity pulling the motor out of its symmetrical range."

i don't think that has been a problem yet for any of the b&c horn loaded subwoofers.




"We should also run the numbers to figure out which rear volume will reactance annul the horn - doing this will balance on the pressure on each side of the driver at Fc, and reduce cone flexing which will be a bigger issue with this large diaphragm."

i'm not sure what you are referring to here. the fc of this horn is around 19hz. the driver fs is 30.5hz. how those are going to arrive at a reactance mitigated low corner isn't something that i am familiar with how to accomplish. acoustical impedance/reactance seems well matched, but i'm not sure exactly what you are suggesting.






"Also, drilling a hole in the wall means you've pretty much fixed the acoustic source of the subwoofer into your room. Room modes will dominate the perceived performance, so it's good to make sure you're picking a location that is optimal for your space. The best way to do that would be to move an existing subwoofer along that wall until you find the ideal location. Even then, the horn presents a complicated acoustic impedance to the room which will affect these simulated results."

he has tested his current sub in the location of the horn entry to the room and it appears to be fine.



"I would also recommend lining the horn with absorptive material so you don't get the cavern effect at higher frequencies - this becomes more of an issue as you make the horn mouth larger and larger."

example?




"How high in frequency do you want the horn to go?"

i think the application is bass horn, not midrange horn.




"Bifurcating the throat of the horn can reduce the inside/outside pathlength difference which helps with high frequency extension, but that may not be an issue here. If you do it right, you might be able to reduce your bracing needs by balancing the pressure across the bifurcation panel....I'd have to sit down and run some numbers to see if that's doable with a simple build approach."

this might have application for a midrange horn, but i don't see the advantage here. the horn design employs a relatively low compression ratio as well, so differential loading on the driver is going to be relatively minimal compared with other designs.




"Also, it's a bit counter-intuitive, but the areas needing the most bracing will actually be at the mouth end. We think about higher pressures at the throat due to the compression ratio, but that is getting turned into a velocity that gradually changes to a pressure at the mouth. It's the pressure that will cause your cabinet walls to vibrate. The mouth is also the larger aperture, so the panels vibrate easier too."

a bracing plan was suggested. i think it will be more than satisfactory. do you disagree with the bracing plan?




"What about having two mouth openings?"

that could be done, but would complicate things and a big part of the idea with this one is to keep things as simple as possible even if it gives up a little bit of the room mode minimizing behavior that you are talking about.




"Btw, you should be using 1/8 space in hornresp....the room is technically smaller than that, but that's the best hornresp will do."

agree...but for the sake of comparison with winisd models, 2pi space is being modeled. pressure vessel gain is also going improve bass response and that isn't in the model either.
Edited by LTD02 - 6/25/13 at 7:54pm
post #49 of 109
Thread Starter 
It is gratifying to see how much participation this thread has generated. It would not be possible without help. Now it long past the "possible" phase.

MBentz, I tried a smaller sub I have in the location I have in mind, a JBL 2245H in a relatively small ported cabinet (I was too lazy to drag the 21" across the room). It is pretty limited in low extension due to the 5.5 ft^3 size & 40hz tune, although it sounds great in it's effective range. How the next lower octave sounds out of that location is not something I can evaluate just yet, but there was nothing overtly wrong with the location. Which is fortunate, because while I can spare the space in the end of the room I can't divide it in two with the build.


I'm hoping to cross over at about 80hz, which is where I am currently using my low-pass. Much higher and I'm concerned about it getting directional. If I were to cross over higher, it wouldn't be much. 120 would be it, probably.

Thanks, and in three weeks I ought to be cutting wood!

Oh, and I live in SE Idaho. In a fairly tolerant blue-collar neighborhood where Harley Davidsons, illegal fireworks, and loud music are not considered "nuisance" but I'll bet they've never heard anything quite like this thing biggrin.gif

And luckier still, my wife loves my system; keeps me out of trouble!
post #50 of 109
Thread Starter 
LTD, that is a very workable refinement ... and moves this build a little closer to the "Monster" class. Go big or go home, and as long as I'm devoting the effort to build it, why not maximize its capabilities?

Question: I remember your suggestion about a hi-pass filter in the low 20's or so. The only filter I have is an inline 12dB/octave 20hz FMOD, and I don't suppose that will suffice. Suggestions?

Next question; What about a grill? I don't want to restrict airflow, but the mouth of this thing will be big enough the kids could crawl in there! It would be worth it to me to put a decent grill over it. Looking at Reliable Hardware's site, their 3/8" square hole grill material has 56.2% flow open area, so to be on the safe side I would want ample area and probably a little stand-off distance ?? The cosmetics would be easy enough to work out and aren't a concern for here.
Edited by cattskinner - 6/25/13 at 10:32pm
post #51 of 109
actually, a section of aluminum fence or something similar might be the ticket...very open and enough to keep people out, cheap too.

i'll monkey around some more and see what it needs for a high pass.
post #52 of 109
Thread Starter 
"actually, a section of aluminum fence or something similar might be the ticket."

Super, is there anything like resonance to be concerned about? My guess would be no, and it would be an easy solution.

I've heard many recommendations for 4th-order hi-passes, and am not familiar with them. Can they be had/made as passive in-line units to filter the signal prior to sub amp? My electronic crossover has 4th order at it's dividing network, but the hi-pass integral to the unit is 2nd order at 25hz. Too little too high? Might as well not filter out useful freq's, or turn sub useable freq's into heat and excursion.

From what I read in Ricci's threads, the B&C's in this class function well up to 20mm xmax, and in an email we traded he told me my driver would work fine up to 19mm or so, beyond which I could expect distortion but no damage until "you really beat on it beyond that" ...at which point motor force decreases rapidly, the suspension is super-tight and further voltage accomplishes nothing useful. On his SW152, he ran sweeps at ungodly levels, free air swept 10-20hz @4000 watts, with no damage. My driver is not equipped with that large a motor, spider, or voice coil, so it's not something that could be extrapolated easily. BUT, it does say something about B&C's ability to tolerate abusive signals. It's not my intention to abuse the driver, but if a second-order filter would work I've got one.

I have run some pretty serious voltage through this driver with test freq's well below cabinet tuning, and even unloaded I had to work pretty hard (or the amp did, EP4000) to really move the cone anywhere close to 3/4".
post #53 of 109
Electronic Hpass would be the easiest but you could also build a passive Hpass. More than likely you wont push this sub as hard as you might think with the horn design. But that being said I would definitely put in a Hpass for protection. Fc 19hz and Fs of 30 I would definitely want a Hpass just in case. May not mean anything but to me I am glad it has a large motor so the cone CAN be pushed hard in such a large cabinet. Man I cant wait to start building my other horn projects. smile.gif
post #54 of 109
"From what I read in Ricci's threads, the B&C's in this class function well up to 20mm xmax, and in an email we traded he told me my driver would work fine up to 19mm or so, beyond which I could expect distortion but no damage until "you really beat on it beyond that" ...at which point motor force decreases rapidly, the suspension is super-tight and further voltage accomplishes nothing useful. On his SW152, he ran sweeps at ungodly levels, free air swept 10-20hz @4000 watts, with no damage. My driver is not equipped with that large a motor, spider, or voice coil, so it's not something that could be extrapolated easily. BUT, it does say something about B&C's ability to tolerate abusive signals. It's not my intention to abuse the driver, but if a second-order filter would work I've got one."

yeah, the b&c21's have a really tight suspension, including yours, which affords them a level of inherent protection.

i couldn't determine which type of filter the fmod is, only that it is 2nd order 20hz.

if it is a second order butterworth, then the filter is -3db at 20hz, and -6db around 15hz, which is 1/2 and 1/4 power respectively.

here is how to check the model yourself. i forget which amp you have, but let's say it is an ep2500/4000 class, with 1300 watts into 8 ohms bridged. you can model it by inputting full power 1300 watts (102 volts) and checking excursion down to around 35hz, then reduce the power by 50% (voltage to 72) and check excursion at 20hz. then reduce power by another 50% (voltage to 51) and check excursion at 15hz. [reducing voltage by 1.414 reduces power by 50% btw.]

max excursion is right around 20-22mm in all cases, which is fine for a max.
post #55 of 109
How aboutt hardware cloth (wire fencing)?
Quote:
Originally Posted by cattskinner View Post

Next question; What about a grill? I don't want to restrict airflow, but the mouth of this thing will be big enough the kids could crawl in there! It would be worth it to me to put a decent grill over it. Looking at Reliable Hardware's site, their 3/8" square hole grill material has 56.2% flow open area, so to be on the safe side I would want ample area and probably a little stand-off distance ?? The cosmetics would be easy enough to work out and aren't a concern for here.
post #56 of 109
Thread Starter 
"How about hardware cloth (wire fencing)?"
Sounds like that, or a number of other options would work fine. So long as it is not going to interfere with the sound, or produce sound of its own, I guess it is less of an issue than I'd feared. Hmmm, in keeping with the theme of this thing that's emerging, I wouldn't have much trouble coming up with expanded steel grating, and just powder coat it black. cool.gif

QUESTION: Before I brush off my rudimentary geometry and get down to brass tacks figuring out cut lengths and joint angles, I'd like to verify something. The area of S2 is pretty critical I gather, as that determines the horn's compression ratio. In the image

it appears that the area of both S1 and S2 is determined in the vertical plane, not the plane of the driver's axis. Have I got that right? If so, given the measurements you've provided, I can solve the rest, probably. My wife's best friend's father is a heckuva' cabinet maker, and could solve it in a snap.

I was glad to hear that fir is as rigid as hardwood ply. It is a lot easier to pay for, and purchasing is coming up this weekend if things go well.

Oh and RE: "Btw, you should be using 1/8 space in hornresp....the room is technically smaller than that, but that's the best hornresp will do."
And: " max excursion is right around 20-22mm in all cases, which is fine for a max"

If that's true, or close to true ...
Modelling 110 volts and eighth-space the excursion does not exceed 22mm until it drops below 21hz and looks like this:



Chrap, you are probably right, I might not need to push this really hard for the most part. Distortion ought to be negligible even at some pretty generous levels. Build and the amp driving it (EP4000) all for under a grand, it looks good on paper. I'm eager to get going on it. Ten more days and my semester rotation is over and I'm on it!
Edited by cattskinner - 6/27/13 at 6:03am
post #57 of 109
Now I am becoming more and more curious. What does the SW115 offer or doesnt offer that the 152 cant or can?

This kind of SPL is amazing. I would need four of my 15's to get there and that makes the 21" cheaper in the end at normal retail. Now I could not move this cabinet and one of these cabinets is bigger than four of mine but still it is another viable option.
post #58 of 109
The SW115 has a coil overhang of 10mm and B&C rates the Klippel defined xmax as 14mm. The coil leaves the gap entirely at 24mm. There is basically no way that the driver will go much past probably 18-20mm one way. I would model to use about 15mm with 20mm as the sounds not very good and not very linear anymore limit. It will be highly distorted by that point but in no mechanical danger

I would never model using 0.5 or 1/8 space as a realistic indicator of headroom or response shape in a real room. (Only use that for modeling in car cabins).

In the last 2 rooms I have been in the average SPL was only slightly better than modeling in full space or 4.0 on HR because you don't sit at 1 meter from the sub you sit like 4 meters from it. Modeling in 2.0 or 4.0 matches up much better with what you will actually deliver to the seats broadband. I always use fullspace for output modeling.
post #59 of 109
Thread Starter 
With you on that one, and thank you for the clarification, Ricci, and if I have referenced your input in error my apologies.

I have had some similar suspicions about "room gain," though I've heard a number of different opinions on that one. My feeling is that modeling predictions for a room would take some fairly sophisticated empirical measurements. With no homogeneity in the building materials of the room that could be quantified, unpredictable objects/furniture in the room ... and so on. I do not have measurement equipment at all beyond an old BSR 3000 that I can't seem to get a mic for. I'm relying entirely on the genius of Room Optimization, something an old dude like me still isn't entirely comfortable with even while the results impress me.

What does stick out to me is my experience with this driver in a 257 BR tuned to a theoretical 32Hz. It's already pretty impressive. Modeled to the same standards of excursion between WinSD and Hornresp in 2.0 x Pi, this build shows pretty significant gains below 40hz, especially in the 20-30hz range, which is exactly what I was hoping to achieve with a large horn build so as to gain a bit for HT.

My listening room is 195 square feet, and my listening point is almost exactly 2 meters from the horn mouth's intended location. If I thereafter feel any serious need for more SPL, I should get my ears, AND my head, checked!

Chrap, I'm no authority, but I suspect the 152's higher performance might be a waste in such a large, lower-compression design. Just plugged into the Hornresp model with no modification, it didn't like this horn at all. That said, if I had had money for a 152, I'd have bought one. But I got this one super cheap and haven't regretted it a bit

Modeled for a more conservative 14mm @ 2500watts, 1/2 space, looks like this:



and 1000 watts, with excursion a shade over 15mm




And I still call that pretty generous for what it is: Getting the most bang for the buck I can with a pretty good driver I have on hand, on a meager budget, with a build so simple anyone could do... even me. smile.gif
Edited by cattskinner - 6/27/13 at 6:32pm
post #60 of 109
"it appears that the area of both S1 and S2 is determined in the vertical plane, not the plane of the driver's axis. Have I got that right?"

it is on the plane of the driver's axis. i should have tilted the bracket on an angle to show that.

also, that is the height inside of the horn. it does not account for wood panel thickness.
the 3.875" is air space, on the woofer center axis, in between the two panels.

try to get it as close as possible. if it is off by a hair, it won't completely ruin the horn,
but it might change the response a bit.

all the other measurements have a little wiggle room in them. try to get them as close a possible,
but don't worry if they are off by a smidgen.

"I wouldn't have much trouble coming up with expanded steel grating, and just powder coat it black."

sounds good. the key point is to not put anything that will impede air flow. expanded steel grating would
be fine even a 'check' pattern of rebar could work.

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