What can I do with this 8" TB sub without a 100 foot long port? - diyAudio
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Old 14th February 2007, 07:35 PM   #1
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Default What can I do with this 8" TB sub without a 100 foot long port?

I have acquired this 8" TB Neo sub for free, and I can't figure out what to do with it. I'd be fine using it in my car or as a small home sub, but whenever I use software to model a box for it it gives me a port so long that the box required to hold it would defeat the whole purpose of a small but powerful driver like this. I am not that experienced with using those programs so i could be doing something wrong. I have searched both here and on Google on gotten nothing but dead-end threads with the same question as me, but nobody seems to answer. Anybody got any ideas?

http://www.partsexpress.com/pe/showd...number=264-833
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Old 14th February 2007, 09:33 PM   #2
owdi is offline owdi  United States
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For home use, how about a .6 cu. ft. box with this port.

Build the box out of 3/4" MDF to be 9"x16"x13"

Mount the port and the woofer on the 9x16 side.

Use the maximum length of the port, which is 11 inches. The end of the flared port will be 1.25" from the back wall. This will extend the acoustic length of the port to about 14"

In a .6 cu ft. box w/ 2" x 14" port you get a tuning frequency of about 30hz.

Assuming your plate amplifier has a rumble filter (2nd order highpass at 25hz), at 120 watts air velcity in the port will be 37 ft/sec. Not ideal, but the heavily flared port will prevent any kind of chuffing.

If you want to build the subwoofer amplifier into the box, make the box taller. 9"x20"x13" could also work.

Dan
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Old 15th February 2007, 06:49 AM   #3
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That's interesting. I still have a 75 wrms PE plate amp. I wonder if that will be enough to move some air with that thing.
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Old 15th February 2007, 01:39 PM   #4
eddog is offline eddog  United States
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Check out http://www.billfitzmaurice.com I built his Tuba18 box and it is very good! This model of Tang Band can be used in his AUTO TUBA design also i believe. There are lots of other designs on that site also.
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Old 15th February 2007, 01:47 PM   #5
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Your problem is that the Vas of the drive unit is quite small, and Xmax fairly large. To get a vent that does not chuff due to the large excursion of the drive unit, it needs to be wide, which means it needs to be long because of the small box. The answer is a passive radiator for best efficiency, or use the box sealed with some EQ and trade SPL.
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Old 15th February 2007, 02:45 PM   #6
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There are lots of posts around the net about folks using these, so a search is probably worthwhile. (also search on the W8-740C which is a ceramic magnet version with similar tradeoffs).

The nutshell summary is that you have 4 basic choices, in rough order of practicality:
1) sealed box in the car, where cabin gain compensates for the high F3 rolloff. You could try an eq'd sealed box in the home, but there isn't that much volume displacement to work with.
2) Passive radiator. Only practical way to get a useful small box for home use
3) Tuba. I haven't built one (yet - TT on the slate when I can get back in the shop), but they're amazing looking designs if you have space for a big box
4) Get a few more of the same drivers and run them in the same box, which brings the box size up to the point where the ports aren't quite so silly. Maybe not that cost-effective though, as a single Dayton RS series sub driver costs about the same as 3 more of the TB's.
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Old 16th February 2007, 03:36 PM   #7
owdi is offline owdi  United States
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#4 doesn't solve the problem, because as you add drivers the port area and length requirements increase.

Paul - the solution I suggested will work very well with the 75wrms amplifier. If you want to use it in your car, I'd highly recommend against ported. Instead, go with a .25 cu. ft. sealed enclosure. The QTS of .55 will sound great in a car.

Dan
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Old 16th February 2007, 03:45 PM   #8
beerman is offline beerman  United States
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you could try this, though it's a lot of cutting and not very efficient because of the snaking port.
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Old 16th February 2007, 10:53 PM   #9
pjanda1 is offline pjanda1  United States
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I built this odd contraption for the MCM 55-2421, a cheaper clone of the W8-740C. I choose this as I had the left over parts. The enclosure is a tube with a 7.25" i.d.. If memory serves, the thing is about 30" long. It has a pvc port with a 3" i.d., about 27" long. The driver fires into the bottom. The port is held in with a closet fitting, that is filed by hand to be very flared. Obviously, it's not the ideal solution in terms of resonances, but it works pretty well. It models -3db a little below 40hz, and it pretty flat to 35hz in room. The port chuffs easily with 30-35hz sine waves. I gave it to my step brother. With the typical stuff he listens to, it sounds great. There isn't enough content down there for the chuffing to be audible. It also isn't the most efficient use of space, but it fits decently at the very front of his trunk. It's a cheap and easy build. It's an easy way to get a long enough port into a small enough enclosure.

This is my least favorite implemenation of three I've tried for this driver. However, the 8ft transmission line isn't going to work in your car. (I no longer needed it, so I cut it down to build the ported enclosure.) I also built a passive radiator system for a friend. Its tiny and works great. Its an E.B.S. that reaches 30hz easily, but must be crossed over below 60hz. Unfortunately, the nice, cheap P.R. I used isn't available anymore. I haven't seen another cheap P.R. that has enough mass to tune suitably and enough Xmax to use the drivers capabilities. I think it would be silly to pay twice as much for the P.R. as for the driver.

I know the TB Neo is a bit differnet, but I thought I might give you some ideas. The Fitzmaurice AutoTuba would be great if you have the room and can build it. Note however, that he uses a little sealed box in his own trunk, as he, like most of us, doesn't need that much bass in his car.

Whatever you choose, I predict you'll be very happy with that driver in your car.

pj
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Old 18th February 2007, 12:20 AM   #10
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I think I have enough scrap wood around here to try it in both a .25 enclosure in the car and a bigger one in the house and see where it is most valuable. I'm already thinking it will please my wife to have it in her car, except I was just about to put a 15" free air sub in there with some EQ for ***** and giggles. I'd better ask her before I do that anyways. Thanks for the input everybody.
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