1/4 wave for dc160

[kenrhodes]

I'm toying around with the idea of having a t-line sub woofer based on the Dayton classic 6.5 dc160-8. According to some calculations I found online I will need a 5 and 3/8 round pipe (same size as the cone) 98 3/4 inches long (1/4 the length of 34hz) for a 32hz tuning. I was thinking about picking up some schedule 40 pipe and lining it with closed cell foam to reduce the internal dimensions.
Am I close or am I in the middle of a "pipe dream"?

[jhollander]

Re: 1/4 wave for dc160

Seems doable, but it would be easier to make it from wood and fold it to fit in your house. For a t-line you would typical stuff the first 1/3 to 1/2 and not line it.

You are not going to get much volume at 32 hz. Compare it to a ported enclosure of the Dayton III

[Paul K.]

Re: 1/4 wave for dc160

You're apparently assuming that it's always best for the line's 1/4-wave resonant frequency to be equal to the driver's fS. Actually, that's not correct as it's also dependent on the driver's Qts, assuming you want an overall fairly flat response. When Qts is around 0.4, having the line's 1/4-wave resonance equal to fS will usually give good results. but when Qts is lower than 0.4, and this driver's specs say it's 0.33, the line's 1/4-wave resonant frequency needs to be higher than fS, and if Qts is higher than fS, the line's 1/4-wave resonance needs to be lower than fS. Secondly, there are going to be some really big dips in the response with a non-tapered or non-mass-loaded line and even more so if the driver is located at the very beginning of the line, but for a true subwoofer that's crossed no higher than 200 Hz, those big dips will be negated by the crossover's rolloff because they're higher in frequency. You really need to model what you plan to build and do so with actual T/S measurements, not published ones.
Paul

I'm toying around with the idea of having a t-line sub woofer based on the Dayton classic 6.5 dc160-8. According to some calculations I found online I will need a 5 and 3/8 round pipe (same size as the cone) 98 3/4 inches long (1/4 the length of 34hz) for a 32hz tuning. I was thinking about picking up some schedule 40 pipe and lining it with closed cell foam to reduce the internal dimensions.
Am I close or am I in the middle of a "pipe dream"?

[JasonP]

Re: 1/4 wave for dc160

Thanks Paul. I was going to reply, but I figured I'd wait for the guy that knows first. Speaking of which, I'm surprised that 0.4 Qts is the right Q for an Fs tuned line, I'd have expected .5 or so just based on guess logic. Learn something new everyday!

[Paul K.]

Re: 1/4 wave for dc160

This is not an absolutely exact "rule". It's a guideline, but if you start there it will allow you to get to a good, final design more quickly.
Paul

Thanks Paul. I was going to reply, but I figured I'd wait for the guy that knows first. Speaking of which, I'm surprised that 0.4 Qts is the right Q for an Fs tuned line, I'd have expected .5 or so just based on guess logic. Learn something new everyday!