just a guy said:
There are at least three benefits of using a compression chamber in a tapped horn design.
1.) When using push-pull woofers with a compression chamber second order distortion is cancelled. This effect is very audible. You must hear it to understand.
2.) The air volume in the compression chamber can help flatten the response without resorting to adding inductors. On my dual W8-740 tapped horn, the response was flatter with the compression chamber.
3.) The large air volume in the compression chamber acts as an air spring which can help protect the woofer’s cone from high throat compression ratios. I’ve blown up my fair share of woofers. I’ve trashed some B&C 8PS21 woofers in a conventional single woofer tapped horn; blew a hole right through the cone. However, in another push-pull tapped horn using the same woofers I’ve had no problems and it has a higher compression ratio!
Rgs, JLH
AndrewT said:
I didn't use software--went by gut. Is it optimal? Who knows... was willing to blow an afternoon and $90.00 worth of material to find out.
The primary point is this: it works extremely well. The bass, though large, isn't "loud" in the traditional sense. It's "very" deep, solid--feels like an invisible hand is grabbing the room and giving it a bit of a twist. I've never heard anything like it. Low notes (first two octaves) are its speciality, higher notes don't seem to make it out the port.
Just got an iPhone, I'll take some pics when we fabricate the next module.
True. But none of the designs I posted are for dual drivers. They could be changed to dual driver designs easy enough but then there would be less total subwoofers for distribution throughout the room, which I'm told is also an audible improvement.
Not in my experience. In fact I've found the opposite to be true but my tapped horn modelling experience is limited and this was the first time I tried to model with a chamber.
Are you sure about that? I'm not nearly smart enough to confirm or deny this. Your examples don't include enough info to conclusively blame the problem on any single issue, it sounds like you doubled the amount of drivers, added a chamber and may or not have made significant changes to the actual horn and you never mention how much power was applied to each design.
Anyway, you obviously have way more experience than me, so you are probably right.
Do any of the commercial tapped horns use a chamber? The only one I was ever really interested in was the dts-20 so I'm not sure what's going on in any of the others.
Picture of TH-SPUD from another forum. One could argue that the lower woofer is in a compression chamber.
JLH, would you be so kind to elaborate on your point (1) or maybe give out some links to pages that do?
just a guy, in my experience, there is not much difference between two and four subs in my room. Both setups need equalization, two subs need a little more but have more very low frequency gain per sub. If you accept the fact that you need to equalize no matter what you do, you may as well stick with two subs.
JLH, would you be so kind to elaborate on your point (1) or maybe give out some links to pages that do?
just a guy, in my experience, there is not much difference between two and four subs in my room. Both setups need equalization, two subs need a little more but have more very low frequency gain per sub. If you accept the fact that you need to equalize no matter what you do, you may as well stick with two subs.
Attachments
Good point. But the other one is definitely not in a chamber and it looks like they both receive the same amount of power. Other than the slightly changed signal due to the series wiring (or maybe that's key) they are fed the same. I'd have trouble believing the chamberless driver is handicapped by it's lack of chamber or it would have a chamber too.
Thanks for that, I've never tried. I got 4 of these drivers specifically for trying a distributed sub system, maybe I don't need 4 separate subs. Probably 2 weeks before they arrive, so I have lots of time to decide.
just a guy said:
Just A Guy,
I’m all about quality and not quantity. I personally prefer two extraordinarily performing subs over four or more mediocre performing ones. I’ve never considered multiple subs because I’ve been able to achieve my desired results with a stereo set of properly designed tapped horns.
Whether the air chamber smoothes or ripples the response is very dependant on the tapped horn’s design and the woofer used. I have seen it go both ways. I just depends on your design.
I am very certain about the air chamber serving to protect the woofers. With less than 260W into one of my 8PS21 tapped horns I blew a hole through the cone. I then redesigned for a dual woofer setup. I started the redesign by keeping all the path lengths the same, but doubling the areas. I then arranged the woofers in push-pull with an air chamber. After much simulating, I actually had to reduce the throat area to get the smoothest response. Therefore, my throat compression ratio went up. Once I built it I was able to put about 600W into the push-pull tapped horn before I had to stop due to high SPLs. After inspection there was no damage to the woofers. I don’t know of any other way to be more convincing then that.
Rgs, JLH
MaVo said:
MaVo,
Take a look at the below Dumax Report on the Dayton Titanic Mk III subwoofer.
http://www.parts-express.com/pdf/295-404dumax.pdf
Of course this is not the woofer I used, but the asymmetry seen in this report is very illustrative of most woofers on the market. Even the best pro sound woofers have a degree of asymmetry. Since the motor’s ability to control the cone is not symmetrical, this leads to even order distortion. However, when you use woofers in push-pull with a common chamber; the chamber acts as an acoustical summation device. The suspension non-linearity and the asymmetrical drive get canceled. Where the two woofer’s motor strength differs, the net result is an average of the strengths (Green line). See below graphics.
From original report
Superimposed and flipped to show non-linearity – Green line shows result of summation
Notice how the Bl non-linearity begins at only 3mm of cone travel. Notice how Kms non-linearity begins at only 7mm of cone travel.
This is the best I can explain this from a technical stand. If you guys still don’t understand, I can’t help you. Subjectively, I would not consider using anything but push-pull for “subwoofer” applications. However, I am willing to use single woofers for mid-bass and higher frequencies where dual woofers are not practical. It all depends on your application. Everyone’s situation is different.
Rgs, JLH
Great explanation, thanks. That bl curves could be asymmetrical, was the missing link for me.
JHL, very nice, clear as mud, thanks 🙂 ehh, I suppose drivers should be "clammshell-mounted" fore optimal result
FlipC said:
It applies directly to the SPUD. Looking at MaVo's post #2665 you can see how it works. We need to assume a positive voltage applied to the "+" terminal of the woofers causes the cone to travel toward the magnet. Since the woofers are reverse mounted and wired in opposite polarity they both force a low pressure in the horn throat when a positive voltage is applied to the box's "+" terminal. This is because both cones will be moving toward the mouth of the horn and away from the throat.
What Hornresp data are you looking for? I've posted my dual Tang Bang W8-740 horn in here before. It can be used as a guide for your own design.
Rgs, JLH
tinitus said:
They can be mounted like the SPUD in MaVo's post #2665 or you can create a defined chamber like I did with my dual W8-740 tapped horn. The chamber feeds the throat of the horn. One woofer’s magnet sticks out in the mouth of the horn, and the other woofer’s cone faces the mouth. A clam shell does not work. You want the cones traveling in opposite directions in relation to their magnets. A clam shell only doubles volume displacement. Only reverse mounting and reverse polarity provides both 2X displacement volume and distortion cancellation. See graphic below
Rgs, JLH
And I was thinking those Eminence 4012HO THs put out a lot with single drivers.
Wonder what it would do re-designed for a pair of 4012HOs in each cab...
Or maybe start with a pair of smaller drivers, need something that's good to ~ 60Hz, a pair of Tang Bands should work for that.
No; gotta finish my front horns first...
But Tapped horns are fun, and put out a suprising amount of bass.
Wonder what it would do re-designed for a pair of 4012HOs in each cab...
Or maybe start with a pair of smaller drivers, need something that's good to ~ 60Hz, a pair of Tang Bands should work for that.
No; gotta finish my front horns first...
But Tapped horns are fun, and put out a suprising amount of bass.
serenechaos said:
If you thought the single 4012HO tapped horns were bad, you have no idea what a pair of W8-740's can do. Needless to say, my dual W8-740 tapped horn was banned from the house by the Misses.
JHL, thanks fore the very nice pictures and detailed explanation
I thought the problem was due to the fact that most drivers move different when going in or out, due to different flux changes, or whatever, especially at large excursions
I actually thought the drivers should be reversed to have any effect on this...I guess I thought wrong
I thought the problem was due to the fact that most drivers move different when going in or out, due to different flux changes, or whatever, especially at large excursions
I actually thought the drivers should be reversed to have any effect on this...I guess I thought wrong
JLH said:
Only reverse mounting and reverse polarity provides both 2X displacement volume and distortion cancellation. See graphic below
Rgs, JLH
Are this called reversed mounting...and how can you reverse the polarity when mounted like you show
Im sorry, not your fault, but I really dont understand it
But forget it, please go on
JHL, man Im sorry, im a fool
I see your neat trick now...seems I didnt understand your design at all, with the inside of the "driver-box" loading the line
I didnt understand how you would get 2xdisplacement either, but now it makes perfectly sense
Its beautiful intelligent design, I want it 😎
And folks, please... ignore my previous post
I see your neat trick now...seems I didnt understand your design at all, with the inside of the "driver-box" loading the line
I didnt understand how you would get 2xdisplacement either, but now it makes perfectly sense
Its beautiful intelligent design, I want it 😎
And folks, please... ignore my previous post