# Treating SBIR for Transmission Line Speakers



## Kaisergrendel (Jul 19, 2011)

Hello, I'm posting to ask if anything can be done to address SBIR for my transmission line setup pictured here:



















As you can see the speakers are placed very close to the rear wall, and there isn't space to move from farther off the wall. I know some people say SBIR isn't an issue for the rear of the speakers, but in the case of transmission lines where some bass is vented out the back, will there be a problem?


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## robbo266317 (Sep 22, 2008)

I cannot be sure, however it looks like they have adequate room to "breath" 
The only true way to tell is use REW to measure the response compared to predicted.


Cheers,
Bill


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## bpape (Sep 14, 2006)

SBIR is absolutely relevant for the wall behind speakers. In your case, with a rear port that close, it's definitely problematic.

Anything done behind the speakers to assist is going to also damp the output of the vent. You can do it - just have to be careful to not get things too close to the point where you're restricting airflow and the ability of the pressure loss to occur which forms the back wave through the line that is responsible for controlling the driver excursion at it's free air resonance.

Bryan


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