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Old 19th November 2012, 09:26 PM   #31
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Originally Posted by Patrick Bateman View Post
Click the image to open in full size.

After going to one dubstep show too many, I've decided to build the biggest sub I've ever attempted to shoehorn into my car.

If you got the need for bass, here's some reasons you might consider building this:

1) if you want to make bass, it's really tough to beat a big box with a lot of power
2) while I am only using eights, I am using eights with a lot of displacement in a tapped horn, so my sims indicate it should get loud and clean
3) All of my best projects have been knockoffs of existing designs. My th-mini clone and my Unity horn projects were all based on Danley's work. This sub is in the same vein, as it's based on the TH-Spud
4) This project is not expensive. All of the wood, two subs, and the wiring costs less than $300. I think the Alpine eights are a screaming deal, with lots of displacement, a well thought out design, distortion reducing shorting rings, and a flat BL curve. You could spend a lot more and get less.
5) One of the more unusual aspects of this sub box is where it's designed to be located. It's designed to go in the back seat of a car, not the trunk. I'm doing this for a number of reasons:
a) I've kept the stereo 'stock' in this car because it's better for the resale value
b) I think that it's more difficult to get the midbass 'correct in a car than the subs. In this design, the subs are going to be run well up into the midbass freuencies, possibly as high as 300hz.
c) I believe that subs in the cabin have the potential to play a lot louder than subs in the trunk. This is due to standing waves. (Basically the ideal location for SPL in a car is to have a sub in the center of a vehicle IMHO.)


Anyways, stay tuned, should get interesting. As time permits I will publish a diagram that's easier to follow. The one above is very rough.


This box is about 80% finished now, but I'm already considering a replacement for it. I bought a new car a week ago, and I literally have no place to put this sub.




Here's an idea that I am toying with:

1) take the sub above, which was based on the th-spud, and scale it down by as much as 75%.
2) In order to reduce the foot print to this extent, I'll have to use a much much smaller driver. Perhaps the 5" M130X from GR-Research?



As I understand it, cone area is one of the most important parameters in a horn. (Someone correct me if I am wrong.) So if I want to scale down the box size, I need to scale down the cone. Ideally I'd want a driver with a diameter of something like 4" with an FS of 50hz or so, and as much xmax as possible.

The M130X has a 5.2" cone, an FS of 50hz and an xmax of 7.8mm.

The VAS of the M130X is kinda high, but as I understand it, the cone area is more imporant than the VAS if you want to reduce ripple.

Again, if I'm off on this, someone correct me. I'll run some isobaric sims also, but I've generally found that going isobaric only improves output on the low end in a horn, but doesn't do much to improve frequency response in the midrange and high frequencies. (IE, if you want a smooth rolloff in a horn that's too small, use a small woofer.)
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Old 21st November 2012, 01:22 AM   #32
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What about this one? Tang Band W5-1138SM 5-1/4" Neodymium Subwoofer 264-831

Kelvin
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Old 21st November 2012, 07:07 AM   #33
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As noted in my recent post, my take on Danley's "TH-SPUD" has turned out fan-tas-tic. I'd say this is easily one of the three best subs I've built, maybe the best. It's really hard to go wrong when you clone a Danley box.

BUT...

I bought a new car, and I'm not going to thrash my leather seats with this humongous box.

so...

I'm evaluating a tapped horn with a similar layout, but using a smaller woofer.

Here are some reasons why this might be a good idea:

1) One 'neat' thing about tapped horns is that they're largely dictated by the Thiele Small parameters. In other words, you can take a tapped horn designed for an 8" sub, and replace it with a 4" woofer *if* the T/S parameters are in the same ballpark. YES you'll lose some output, but as crazy as this sounds, you can make a subwoofer with a 4" driver. And I'm not talking about some anemic box that quits at 100hz, I'm talking real solid output down to 40hz.

2) Tapped horns reduce excursion. So basically you can get surprising output from small woofers, as long as the voice coil doesn't go up in smoke.

3) Tapped horns reduce distortion, because reducing excursion reduces distortion.

Click the image to open in full size.
First off, here's the plans for my 'th-spud' clone, using a pair of Alpine SWR-843D car subs. This is the sub I've been listening to for a few days, which sounds great. The outside dimensions are 4' x 2' x 9.25". Six cubic feet.

Click the image to open in full size.
Here's Volvotreter's clone of the TH-Spud. Mine copies the folding, except mine is mirrored, and mine is tuned higher.

Click the image to open in full size.
This is the Seas L12. Yes kids, a 4.5" woofer for a subwoofer! The reason I selected the Seas L12 is that it has T/S parameters which are pretty similar to the Alpine. The Seas trades low frequency extension for efficiency. It's very low, just 83 dB.

Click the image to open in full size.
Here's the SPL output of the Alpine and the Seas in a tapped horn. The reason that the response shape is so similar is that both boxes are tuned to the same frequency. In other words, the pathlength of the horn is EXACTLY the same. But the big difference is the VOLUME of the horn. While the Alpine horn takes up six cubic feet, the Seas horn takes up just 1.5 cubic feet! A reduction of 75%!!!

We could probably get this down even further. The main reason that I made the pathlength identical was to demonstrate that the response of the tapped horn is largely dictated by the horn, not the driver that's ON the horn. The bigger the driver is, the peakier the response gets if the horn is too small.

Click the image to open in full size.
Here's the excursion of the Seas tapped horn, versus the Alpine tapped horn. It's basically the same. Of course the Alpine has more xmax, and the Alpine generates more SPL with the same voltage.

Click the image to open in full size.
Here's the group delay curve.

What's interesting about these curves is that the shape of the response curves are very similar, the Alpine is just louder. So the Seas tapped horn might be an attractive alternative if you don't need to get really loud. Despite the woofer being much much smaller, the F3 is darn near identical! So the sonic 'signature' of the two tapped horns should be remarkably similar, as long as you don't need to achieve high SPL.

Obviously, I'm really tempted to order a couple of these and give it a try. The box is so small I could probably fit it behind my car seat.
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Old 21st November 2012, 02:15 PM   #34
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Quote:
Originally Posted by Patrick Bateman View Post
Patrick,

2) Tapped horns reduce excursion. So basically you can get surprising output from small woofers, as long as the voice coil doesn't go up in smoke.

3) Tapped horns reduce distortion, because reducing excursion reduces distortion.
#2 is partly correct, for a given voltage input a TH driver will have less excursion than that driver loaded in a BR, while putting out more SPL.
A TH with a light cone may suffer from cone damage before voice coil burn out, Pyro's kinked 3015LFs in SS15 style TH are an example of that.

#3 is true for a given voltage input, but false when excursion is considered.
At the same excursion, a TH has more distortion (and SPL) than a BR.

There are many attracted to light weight cones for use in TH, as they sim well regarding sensitivity.
The high sensitivity the lightweight cone brings is good for low power applications, but a light cone that is adequate for BR is put under far more stress when run to Xmax in a TH, the output will no longer be clean, and the cone may fold up before it burns up.

Of course, the people looking for loud often don't care about clean...

Art
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Old 22nd February 2013, 07:59 PM   #35
kees52 is offline kees52  Netherlands
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I guess he's still standing...

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grapjas.
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Old 18th July 2013, 03:51 PM   #36
von Ah is online now von Ah  United States
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Patrick, did you ever build the Seas L12 TH? That looked interesting...
Quote:
Originally Posted by Patrick Bateman
So the Seas tapped horn might be an attractive alternative if you don't need to get really loud.
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Old 13th November 2013, 07:24 PM   #37
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Default How did this turn out?

Quote:
Originally Posted by Patrick Bateman View Post

Here's a comparison of the Alpine Type-R 8" versus Exodus Audio Anarchy, 250watts into 2ohms:

Click the image to open in full size.

I used Mike's "Insubnia" as the baseline, and widened the box to 9.5" to accomodate the woofer. Everything else is identical. (Height, Length, etc.)

Click the image to open in full size.
Here's what the insubnia looks like (not my pics)

Here's additional info:

Audio Psychosis • View topic - Cheap and Different Sub

I think you could get similar results with the dual four ohm 10" woofer, which is stocked at Best Buy. Would have to make the line a bit longer of course.
How did making the insubnia wider and using a larger driver turn out?
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Old 3rd January 2014, 08:47 PM   #38
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Originally Posted by paulmckim View Post
How did making the insubnia wider and using a larger driver turn out?
Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

The original idea was to do the Insubnia, but substitute the Alpine SWR-843D for the Anarchy woofer. You can do this because the Thiele Small parameters are similar enough that you can use the same tapped horn. (You need to increase the width to accomodate the larger basket.)

But as time progressed, I re-arranged things to make the subwoofer fit into the back seat of my car.

Then I sold the car :P

So it's been in my garage for about a year and I think I'm going to resurrect it and use it as the subwoofer for my new Synergy horns, which are documented in the thread "Monster Massive."
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Old 4th January 2014, 11:39 AM   #39
kees52 is offline kees52  Netherlands
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My is told to correct the cone surface when the woofer is in it like this way, magnet pointed to port.

like this.
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File Type: jpg infinity1260W-tapped.jpg (375.4 KB, 119 views)
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Old 30th January 2014, 02:36 AM   #40
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grapjas.
Click the image to open in full size.

Done.

Detail in the thread titled "Monster Massive"
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