Transmission Line Subwoofer

unc2701 · 09-26-2005, 10:06 AM

The woman was out of town, so a friend of mine & i decided to throw together a sub subwoofer with the lowest possible WAF, cost and -3db limit. The cost and the ability to put it together stinking drunk were the true limits.

He had a spare Polk 10" DB series driver, and I just picked up the crown amp from hoosier, and there was plenty of scrap plywood in the garage from another project. For a crossover, I used a variable psuedo active FMOD... mid 50's to 60's seemed to blend well with the LSi 9's, but even going up to 89 didn't get too boomy.

So, 2 hours and $30 later (that includes the beer) we had this:

BrentMcGhee · 09-26-2005, 10:15 AM

hoosier21 · 09-26-2005, 10:20 AM

So how did it sound?

unc2701 · 09-26-2005, 10:23 AM

The sub fires upwards in to an 8' X 12" diameter concrete form tube. The tube could stand to be a hair shorter to match the Fs of the driver, but for our purposes it didn't matter that much. The idea is that the tube is 1/4 the Fs for the driver, so the backwave comes out of the tube in phase with the bottom end, extending your response. You also get some of the tight punchiness of a sealed enclosure since the length allows for a good bit of pressure to build up at the driver end of the tube. The only real drawback is that it's one ugly bastard. Oh, and if your driver's Fs is more like 20 hz, you need a 14 foot tube...

How did it do? for a driver with a Fs of about 40 hz, it was hitting things that it never should have been able to reach- well into the mid 20's I'd say. We were too drunk to, say, run test tones, but it had no trouble digging all the way down to the lowest notes (we had to break out some Chemical brothers & Outkast go past the low E).

So if you've got some free time it's a fun project to try out. Oh, and needless to say, the tube is going out with tomorrow's trash... (the woman didn't think it went with the rest of the decor...)

Vr3MxStyler2k3 · 09-26-2005, 04:16 PM

I'm confused... how is this a transmission line?

A transmission line is something like this...

thehaens@cox.net · 09-26-2005, 04:30 PM

Sid - I seen a T line sub that some of the guys were playing around with in Home Theater magazine about a year ago. It was something like 16 foot in length. They to, just wanted to see what it would sound like, from the article it was said that a T line sub is any cabinet design where the sub driver is mounted on one side of the tube...Wait a minute............

O.k. googled the H.T magazine description...here it goes

"Transmission Line: A (sub)woofer cabinet design where the driver is mounted at one end of a tube with the same diameter as the radiating area of the driver and a length of 1/4 wavelength of the 3dB down frequency. This "tube" may or may not be round and may be folded to decrease the size of the cabinet."

scott

not as large, but looks nice

http://www.teresaudio.com/haven/subs/subs.html#cabinets

phoneisbusy · 09-26-2005, 04:51 PM

Quote:

Originally Posted by Vr3MxStyler2k3

I'm confused... how is this a transmission line?

A transmission line is something like this...

unc2701's is a straight transmission line, I believe yours is a folded style. If you want it more esthetically pleasing and you think the wife will not notice a slight bump in the wall you can try...

http://www.t-linespeakers.org/projects/peter/index.html

heh...

regards

Dave

unc2701 · 09-26-2005, 05:31 PM

Yep, it's just a straight T-line... you could fold it like that picture, but that'd take time, money and sobriety. I will admit that the sonotube was vibrating some, but I doubt that PVC would be much better. Since the pressure is distributed equally, the cardboard is plenty thick (it's like trying to crush an egg by squeezing it...)

Vr3MxStyler2k3 · 09-26-2005, 06:32 PM

Gotcha

Cool

tryrrthg · 09-26-2005, 07:36 PM

Very cool project.

For those that have never seen this link before. Here is Nelson Pass' El Pipo T-Line sub.

09-26-2005, 10:06 AM	#1
unc2701 Polkologist Member Sales Rating: (4) Join Date: Feb 2005 Posts: 2,829	Transmission Line Subwoofer The woman was out of town, so a friend of mine & i decided to throw together a sub subwoofer with the lowest possible WAF, cost and -3db limit. The cost and the ability to put it together stinking drunk were the true limits. He had a spare Polk 10" DB series driver, and I just picked up the crown amp from hoosier, and there was plenty of scrap plywood in the garage from another project. For a crossover, I used a variable psuedo active FMOD... mid 50's to 60's seemed to blend well with the LSi 9's, but even going up to 89 didn't get too boomy. So, 2 hours and $30 later (that includes the beer) we had this: Attached Thumbnails __________________ Gallo Ref 3.1 : Bryston 4b SST : Musical fidelity CD Pre : VPI HW-19 Gallo Ref AV, Frankengallo Ref 3, LC60i : Bryston 9b SST : Meridian 565 Jordan JX92s : MF X-T100 : Xray v8 Backburner:Krell KAV-300i Last edited by unc2701; 09-26-2005 at 10:28 AM..

09-26-2005, 10:20 AM	#3
hoosier21 Polk Expert Member Sales Rating: (17) Join Date: Jul 2001 Location: Georgia Posts: 3,914	So how did it sound? __________________ Acurus RL11 - Preamp Aragon 8008ST - Power amp Sony DVP-NS999ES - SACD player ADS 1230 - Polk SDA 2B - Vandersteen 2Ci (8) 12" driver DIY - Subwoofer Crown K1 - Subwoofer amp Outlaw ICBM - crossover Beringher BFD - sub eq Where is the remote? Where is the $%#$% remote! "I've always been mad, I know I've been mad, like the most of us have...very hard to explain why you're mad, even if you're not mad..."

09-26-2005, 04:16 PM	#5
Vr3MxStyler2k3 Sid the Kid Member Sales Rating: (21) Join Date: Mar 2003 Location: NC Posts: 15,664	I'm confused... how is this a transmission line? A transmission line is something like this... __________________ Da Rig- Mains- Tyler Acoustics Super Towers Subwoofer- Tyler Acoustics Custom Seas 10" Stereo Subs Amplifier- Odyssey Stratos Extreme Mono Blocks Preamp- Odyssey Candela CD Player- Symphonic Line Vibrato The CD Player Power Conditioner- MIT Z Center Speaker Cables- MIT Shotgun S2 Bi-Wire Signal Cables- MIT Shotgun S2 Subwoofer Cables- MIT AVT 1 Power Cables- MIT Shotgun AC1 (Amps/Pre/CDP) MIT Z Cord II (Conditioner/Subs) Polks are in the truck!

09-26-2005, 04:30 PM	#6
thehaens@cox.net Polkhead Member Sales Rating: (1) Join Date: Apr 2004 Location: Southern Cali Posts: 1,012	Sid - I seen a T line sub that some of the guys were playing around with in Home Theater magazine about a year ago. It was something like 16 foot in length. They to, just wanted to see what it would sound like, from the article it was said that a T line sub is any cabinet design where the sub driver is mounted on one side of the tube...Wait a minute............ O.k. googled the H.T magazine description...here it goes "Transmission Line: A (sub)woofer cabinet design where the driver is mounted at one end of a tube with the same diameter as the radiating area of the driver and a length of 1/4 wavelength of the 3dB down frequency. This "tube" may or may not be round and may be folded to decrease the size of the cabinet." scott not as large, but looks nice http://www.teresaudio.com/haven/subs/subs.html#cabinets Last edited by thehaens@cox.net; 09-26-2005 at 04:33 PM..

09-26-2005, 07:36 PM	#10
tryrrthg Polkhead Member Sales Rating: (11) Join Date: Jul 2001 Location: Columbus, Ohio Posts: 1,799	Very cool project. For those that have never seen this link before. Here is Nelson Pass' El Pipo T-Line sub. __________________ The Had My First Child, Have To "Give Up" My Stereo Room, Condensed Two Channel & HT Rig: Mains: Dynaudio Focus 140 Integrated Amp: Arcam A85 Source: Slim Devices Squeezebox 3 -> Bel Canto DAC 1.1 Home Theater: Sony KDL-40V2500 HDTV, Sony BDP-S550 Blu-ray, Polk CSi3 & R15, Denon 2802 receiver, and DIY sub with Atlas 15

09-26-2005, 10:15 AM	#2
BrentMcGhee Polkazoid Member Sales Rating: (1) Join Date: Feb 2005 Location: Spotsylvania, Virginia Posts: 553

09-26-2005, 10:23 AM	#4
unc2701 Polkologist Member Sales Rating: (4) Join Date: Feb 2005 Posts: 2,829	The sub fires upwards in to an 8' X 12" diameter concrete form tube. The tube could stand to be a hair shorter to match the Fs of the driver, but for our purposes it didn't matter that much. The idea is that the tube is 1/4 the Fs for the driver, so the backwave comes out of the tube in phase with the bottom end, extending your response. You also get some of the tight punchiness of a sealed enclosure since the length allows for a good bit of pressure to build up at the driver end of the tube. The only real drawback is that it's one ugly bastard. Oh, and if your driver's Fs is more like 20 hz, you need a 14 foot tube... How did it do? for a driver with a Fs of about 40 hz, it was hitting things that it never should have been able to reach- well into the mid 20's I'd say. We were too drunk to, say, run test tones, but it had no trouble digging all the way down to the lowest notes (we had to break out some Chemical brothers & Outkast go past the low E). So if you've got some free time it's a fun project to try out. Oh, and needless to say, the tube is going out with tomorrow's trash... (the woman didn't think it went with the rest of the decor...)

09-26-2005, 05:31 PM	#8
unc2701 Polkologist Member Sales Rating: (4) Join Date: Feb 2005 Posts: 2,829	Yep, it's just a straight T-line... you could fold it like that picture, but that'd take time, money and sobriety. I will admit that the sonotube was vibrating some, but I doubt that PVC would be much better. Since the pressure is distributed equally, the cardboard is plenty thick (it's like trying to crush an egg by squeezing it...)

09-26-2005, 06:32 PM	#9
Vr3MxStyler2k3 Sid the Kid Member Sales Rating: (21) Join Date: Mar 2003 Location: NC Posts: 15,664	Gotcha Cool

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Rate This Thread
Rate This Thread: