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Old 31st October 2011, 11:01 PM   #31
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Originally Posted by revboden View Post
I have to say, some of your analogies confuse me...

What is being thrown away?

I should point out that if I build a BR box they are semi-LLT tuned ~14hz and High-pass at 18Hz. I suspect you're thinking about tunings well above that. (which i don't like for many reasons)
When you wrote, "That's why I always have the High-pass set 4hz above the tuning frequency of a BR sub" I didn't for a second suppose you were talking about using a sub with a resonance of 14 Hz! It would be an understatement to say that is unusual.

Nor do I, or many people, have an opinion about the effectiveness of that kind of system since so very few people have ever been exposed to one.

If you were talking about boxes tuned for say, 30 Hz, then filtering out below 34 Hz would indeed be tossing out the content below 34 Hz along with the undesirable consequences of pumping signal into a BR below its resonance. All things considered, just maybe a good trade-off... I can't say. Perhaps for a small driver in a small box, a good design.

Bad me for not immediately supposing you were using a 14 Hz driver. Aside from my 12 Hz driver in an AR-1, can't say as I'd know where to find one.

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Last edited by bentoronto; 31st October 2011 at 11:07 PM.
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Old 6th February 2013, 09:43 AM   #32
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I read that these Seas woofers don't take well to being cranked up- whats your experience?
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Old 6th February 2013, 01:34 PM   #33
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Hi all,

A question that seems related to the topic being discussed here.

I was playing with the idea of building a (subwoofer) TL with LT. Tuning the TL so it's initial roll-off is ~12dB/oct (a small volume box with the line tuned to a low Freq with a taper of 10:1) and then boosting the drooping response with an LT. The benefit of using a TL is that it doesn't unload the driver below resonance (right?).

It seems that is almost the same as EQSS.

This gives a definite improvement in low freq SPL capability, GD is very well controlled, cone excursion is less then a sealed + LT for a given SPL.

Overall this should yield a system with more SPL capability and/or lower distortion, it almost seems to good to be true.. Am I missing something?
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Last edited by Mark.Clappers; 6th February 2013 at 01:50 PM.
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Old 6th February 2013, 05:35 PM   #34
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Quote:
Originally Posted by Mark.Clappers View Post
Tuning the TL so it's initial roll-off is ~12dB/oct (a small volume box with the line tuned to a low Freq with a taper of 10:1) and then boosting the drooping response with an LT. The benefit of using a TL is that it doesn't unload the driver below resonance (right?).

Overall this should yield a system with more SPL capability and/or lower distortion, it almost seems to good to be true.. Am I missing something?
TL do not control cone excursion below Fb, it rises like a BR.
Cone excursion would be less around FB in a TL or a BR than sealed, but more below Fb.
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Old 7th February 2013, 08:22 AM   #35
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Hi Weltersys,

I did see in my sims that excursion rises below Fb, but I also noticed that the acoustic impedance of the line only drops slowly below Fb. This leads me to believe that indeed eventually the driver becomes unloaded at very low frequencies, but in the designs I simmed the impedance only get's real low when the frequency drops to single digit numbers. So to limit excursion a HPF filter is needed (in my case a second order around 14Hz).

Is my train of thought correct (the acoustic impedance of the line controls cone excursion), or am I way of?

Check out the tool I use to sim TL's, made by a fellow forum member, very nice piece of SW (it's the only free windows based tool I know of simulating TL's):

Transmission Line Modelling Software
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Old 7th February 2013, 02:51 PM   #36
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Originally Posted by Mark.Clappers View Post
So to limit excursion a HPF filter is needed (in my case a second order around 14Hz).

Is my train of thought correct (the acoustic impedance of the line controls cone excursion), or am I way of?
Your question would get a better answer from the people that design the simulation programs than me, but sounds like your train is on the right track.
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