Collaborative Tapped horn project

Naudio said:
im trying to make a very compact folding design for my next project

it needs to be 130db 40-100hz


this may also apply to you as well mavo as your trying different designs

i have seen a few tapped horns without angled expansions, im not sure how impotent this is at low frequency's

ease if construction is a + for this design (no horrid angles, there hard to do in a bedroom)

An externally hosted image should be here but it was not working when we last tested it.


Interesting box design. Forgive a stupid question. Is the output port (not shown) a rectangular hole in the top right side the sam size as the inside tunnel (rectangular waveguide) at that point or is it a circular or square port immediately above the driver cone on the top panel?
 
Naudio said:
im trying to make a very compact folding design for my next project

it needs to be 130db 40-100hz


this may also apply to you as well mavo as your trying different designs

i have seen a few tapped horns without angled expansions, im not sure how impotent this is at low frequency's

ease if construction is a + for this design (no horrid angles, there hard to do in a bedroom)

An externally hosted image should be here but it was not working when we last tested it.


You really need to think about your requirements again. Getting 130dB out of one 12" woofer in a tapped horn is going to be extremely difficult at best. The simple math says if your tapped horn is 100dB at 1W/1M, then you will need to feed it 1000 watts (+30dB) to hit 130dB. This is if you don't account for any power compression. In the real world it’s not going to happen. You will need at least two tapped horns, or a dual woofer design with 12's if you are going to get close to 130dB.

P.S. You can actually build your horn the way you have it. It can have a stepped expansion and it will not hurt performance. The nice thing about building a tapped horn as a series of stepped expansions is the construction becomes much easier.
 
Naudio said:
how do i go about simulating such a box deign, im guessing just as you would any other, but is there a golden rule as to how much bigger each next part of the horn is

say throat and first expansion > then double size > then second part > double size, etc
First: excuse my english, its a bit rusty.

Since i have been modeling for caraudio i have build a sort of semi conical/exponetial (more like hyperbolic maby?)horn like this:
r74woh.jpg

I have also build a stepped variant.
The way i did it was just determing S1/S2 and S4 and then i draw it on a sheet 1:1.
I dont think its that critical as long as you find some sort of expansion that ends up well

Dag
 
You really need to think about your requirements again. Getting 130dB out of one 12" woofer in a tapped horn is going to be extremely difficult at best. The simple math says if your tapped horn is 100dB at 1W/1M, then you will need to feed it 1000 watts (+30dB) to hit 130dB. This is if you don't account for any power compression. In the real world it’s not going to happen. You will need at least two tapped horns, or a dual woofer design with 12's if you are going to get close to 130dB.

well mine reaches xmax with 60w this is 125db at 20hz (1/8 space lol)

so if i tune the horn slightly higher it should decrees the excursion and may allow me to get 135db (1/8space again) with 10x60w (600w)

you are correct in free/half space this is impossible
 
Dag-Johansen said:

...semi conical/exponetial (more like hyperbolic maby?)horn like this:
I dont think its that critical as long as you find some sort of expansion that ends up well
Dag

HornResp models conic, exponential and hyperbolic flares, and the choice you make does make a small, but measurable difference. The one flare it doesn't model is the parabolic, which is the worst choice for horn efficiency, and that's the one that everyone has drawn (including you). It's also the best choice, 'cause you can build it easily with plywood or MDF.
 
Don Snyder said:

The one flare it doesn't model is the parabolic.........and that's the one that everyone has drawn...........

You sure? It's my understanding that parallel walls with straight sloping baffle makes it a linear expansion, which if true, then more gain BW with less ripple than conic according to MJK's BLH worksheet. Note that to maintain this expansion through the bend requires a width/depth ratio of 1.0:1.4142 if I figured it right.

GM
 
Hi GM,

I hadn't thought it thru, and Sabbelbacke took me to task in post #1328.

Parallel walls with straight sloping baffle can be extended to intersect in a line. At the line, the area is zero, and one inch away it is finite, therefore the initial flare is infinite. As you get away from the line, the flare becomes less and less. The baffle is linear, but the flare of the baffle is parabolic.

There are slightly less accurate ways of figuring expansion thru a corner, and I follow John Sheerin's technique of preserving the area. See post #1490 for a quick and sloppy technique.
 
Don Snyder said:


HornResp models conic, exponential and hyperbolic flares, and the choice you make does make a small, but measurable difference. The one flare it doesn't model is the parabolic, which is the worst choice for horn efficiency, and that's the one that everyone has drawn (including you).

I know this have been discussed before and i do not understand it.
When i model my horn in hornresp the schematic diagram show the exact same net volum as the box irl.

Dag
 
hello, i am wondering: what is a good driver in the context of tapped horns? i spoke with william cowan and he said, he would only consider drivers with shorting rings. he pointed me to the http://www.eighteensound.com SDR/DDR papers. the drivers from http://bmspro.info also seem to be made with this advanced features.

pondering the use of car drivers... their ts parameters sure are nice for tapped horns, but when i think of car audio, i directly think of parts with horrible error margins and lots of distortion because of "it needs to be able to take 15000w and look evil" tradeoffs. regarding hifi drivers... i just cant take these little things serious any more. too small, too much attention on the looks, too expensive compared to the work they do. this leaves me with pro drivers, more specifically with the aforementioned two companies.

what would you add to the list of superior tapped horn driver choices with reproduction quality as the deciding factor?
 
MaVo said:
hello, i am wondering: what is a good driver in the context of tapped horns? i spoke with william cowan and he said, he would only consider drivers with shorting rings. he pointed me to the http://www.eighteensound.com SDR/DDR papers. the drivers from http://bmspro.info also seem to be made with this advanced features.

pondering the use of car drivers... their ts parameters sure are nice for tapped horns, but when i think of car audio, i directly think of parts with horrible error margins and lots of distortion because of "it needs to be able to take 15000w and look evil" tradeoffs. regarding hifi drivers... i just cant take these little things serious any more. too small, too much attention on the looks, too expensive compared to the work they do. this leaves me with pro drivers, more specifically with the aforementioned two companies.

what would you add to the list of superior tapped horn driver choices with reproduction quality as the deciding factor?


In my experience it is poor practice to pay for something that makes no subjective difference. In regards to a tapped horn being used as a subwoofer, it doesn’t make sense to spend a lot of money on unnecessary driver features. Shorting rings are nice if you were going to use it up higher in the frequency range. However, the high frequency ripple of the tapped horn precludes you from doing this. It just would not be high fidelity. Case in point, I have a nice little 45Hz tapped horn made with a pair of $2 woofers that were on clearance at MCM Electronics. They are no-name high excursion 4” woofers made in China with cheap stamped baskets. In the bass frequencies, I cannot hear any subjective differences between them and my 40Hz tapped horns that are loaded with much higher quality B&C Speakers 8PE21’s. I would build a taped horn with a car audio woofer any day of the week and be proud of its performance. The Danley Matterhorn was built with car audio woofers. The woofer inside of the DTS20 looks like a classical car audio woofer. The most expensive woofer I would be willing to buy for one of my tapped horns is the Eminence Definimax 12HO. That is only because I know it would destroy my house before I could destroy it. Don’t get too hung up on driver “quality”. With horns 90% of the performance is from the enclosure/horn. As long as the T/S parameters are reasonably close, it will work fine.
 
JLH, there are several points in your post which i dont agree with.

- I doubt that every driver is 100% linear within its xmax. Suspensions are not linear, BL product is not linear, LE isnt linear and so on. The companies i stated introduced technology to combat this. Have a look at this pdf: http://www.eighteensound.com/staticContent/technologies/products/18_Sound_DDR.pdf

- You say, that "a pair of $2 woofers" and an pair of B&C drivers perform the same. According to the 1mm xmax of your driver, i am tempted to say, that it sounds the same in a th as a 2 dollar driver because it exceeds xmax even at normal listening levels. This driver looks like a midrange to me.

- You say that DSL use car audio drivers. That is true, but Tom has do make the tradeoff of maximum output per volume per price or no one will buy his designs. There are simply no pro drivers with 27mm of xmax. He has to use what exists in order to achieve the output he needs. If there were drivers with the same power handling and xmax AND better technology, i dont think he wouldnt use them (well, he also has a price problem, which we diy people dont face so much, as we only build few enlcosures of one design).

- Lastly, you say i should ignore the last 10% of the quality. Why? There is no reason to put a bad driver into a good enclosure. Pro drivers are not so expensive, that one couldnt afford them - in contrast to some esoteric hifi drivers, which i would never use. I would make your compromise every time, if it would be my job. But since this is a hobby, i allow myself the pleasure of excess.
 
MaVo said:
hello, i am wondering: what is a good driver in the context of tapped horns? i spoke with william cowan and he said, he would only consider drivers with shorting rings. he pointed me to the http://www.eighteensound.com SDR/DDR papers. the drivers from http://bmspro.info also seem to be made with this advanced features.

Look for measured data. Some other pro driver manufacturers do a very good job with more subtle refinements of pole-piece design and materials choice. It is tempting to be attracted by "triple demodulating rings" and the like, but it is worth a check if it really makes a performance difference at ~50Hz.

From searching around my impression is that there are several good options around the price range of the makes you mention (size for size), but they may or may not have the right T/S parameters.

If you pin down the horn dimensions (maximum tolerable, of course - bigger is better) you'll probably not be left with very many driver options with the right parameters. See what data you can find on those few drivers. Otherwise the field is too large.

Ken
 
Naudio said:


yep dam nice driver, works well in my horn, highly recomended
^ I too can vouch for the Eminence Magnum 12HO, it isn't cheap but it is well made and works well for TH's (25Hz-35Hz tuned). It may not have the greatest Xmax but I know that it's pretty damn bulletproof.

Perhaps the Eminence 3015LF would give more output overall, so this might be another one to consider?