Transmission Line Two-Ways Project

BAM · 21st January 2004, 12:27 AM

Ok, I just got more or less commissioned by a friend to design him a pair of speakers for a $17 Goodwill reciever for playing mostly country music. I have been itching to built a Transmission Line, and this offers me my chance. I am planning on using Tangband drivers. The Tangband W4-656S shielded 4" midbass offers a relatively smooth response to where I want to cross over, which is first order at 4500 Hz. From there, I will have a Tangband 25-669SD shielded dome tweeter handling the highs. This, I think, is the same tweeter that is the GR-Research T1 tweeter. I used MJK's alignment tables and discovered that the line length I need to get response down to 65 Hz (the W4-656S's Fs) is 51.7". The enclosure I designed gives me a line length of 65". Is this a bad thing to have a line that is too long? Or am I still ok? Also, the driver is not at the exact end of the line, but is down the line about 5". Can I just put a piece of BlackHole 5 and some open-cell foam at that end of the line and have everything be fine as long as I account for the offset in my line length?

Timn8ter · 21st January 2004, 04:10 PM

Having built two ML-TQWTs my experience is that it's better to have the line length equal to 1/4 Fs and maybe even tune the pipe just above resonance frequency. I quickly ran the numbers in MK's program and the line length looks bad. Even added stuffing didn't offset the response. I recommend sticking pretty close the MathCAD numbers and try different port sizes and So and Sl ratios. Something else to consider is adding another woofer in bipole configuration for BSC.

21st January 2004, 12:27 AM	#1
BAM diyAudio Member Join Date: Sep 2001 Location: Carmel, IN; West Lafayette, IN	Transmission Line Two-Ways Project Ok, I just got more or less commissioned by a friend to design him a pair of speakers for a $17 Goodwill reciever for playing mostly country music. I have been itching to built a Transmission Line, and this offers me my chance. I am planning on using Tangband drivers. The Tangband W4-656S shielded 4" midbass offers a relatively smooth response to where I want to cross over, which is first order at 4500 Hz. From there, I will have a Tangband 25-669SD shielded dome tweeter handling the highs. This, I think, is the same tweeter that is the GR-Research T1 tweeter. I used MJK's alignment tables and discovered that the line length I need to get response down to 65 Hz (the W4-656S's Fs) is 51.7". The enclosure I designed gives me a line length of 65". Is this a bad thing to have a line that is too long? Or am I still ok? Also, the driver is not at the exact end of the line, but is down the line about 5". Can I just put a piece of BlackHole 5 and some open-cell foam at that end of the line and have everything be fine as long as I account for the offset in my line length?

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21st January 2004, 04:10 PM	#2
Timn8ter diyAudio Member Join Date: Jul 2003 Location: Seattle, WA	Having built two ML-TQWTs my experience is that it's better to have the line length equal to 1/4 Fs and maybe even tune the pipe just above resonance frequency. I quickly ran the numbers in MK's program and the line length looks bad. Even added stuffing didn't offset the response. I recommend sticking pretty close the MathCAD numbers and try different port sizes and So and Sl ratios. Something else to consider is adding another woofer in bipole configuration for BSC.