Possibly the most instructive material I ever found concerning TL design variations was a page created by Bob Brines. In it he compared various TL designs (TL vs. MLTL vs. TQWT vs. ML-TQWT vs. negative tapered QWT), using Martin Kings Worksheets. He modeled each design variation using the same driver, and with each version tuned to the same frequency. It pretty clearly showed how each alignment influenced the frequency response.
Sadly, since Bob is no longer in business, the page no longer exists.
the original url was this:
brinesacoustics.com/Pages/Quarter_Wave_Resonators/Quarter_Wave_Resonators.html
but don't bother going there.
I was able to find it on the wayback machine here:
Quarter Wave Resonators
unfortunately, the frequency response graphs are missing from the archived page! So, the page is now virtually useless.
Does anybody have a copy of this page that includes the graphs? I think many here would find it useful, especially those new to quarter wave design and modeling. Bob himself wrote that the page was not intended to be a design tutorial, but I think it comes pretty darn close.
Eric
Sadly, since Bob is no longer in business, the page no longer exists.
the original url was this:
brinesacoustics.com/Pages/Quarter_Wave_Resonators/Quarter_Wave_Resonators.html
but don't bother going there.
I was able to find it on the wayback machine here:
Quarter Wave Resonators
unfortunately, the frequency response graphs are missing from the archived page! So, the page is now virtually useless.
Does anybody have a copy of this page that includes the graphs? I think many here would find it useful, especially those new to quarter wave design and modeling. Bob himself wrote that the page was not intended to be a design tutorial, but I think it comes pretty darn close.
Eric
Looks like a summary of the article. May add to the report above. https://audioroundtable.com/misc/Quarter_Wave_Generators.pdf
woodo,
Awesome! Interestingly, not all the examples are identical in the two versions. For example, the TQWT example in the article is 93" long, while it's 84" in the pdf you found. There's a few other minor differences too. So I'm not sure if the differences were typos in one or the other, or if Bob revised the examples at some point. In any event, it's great that you found it.
Thanks,
Eric
Can Hornresp be used to model full range TL designs? Inputting data from single 2" FR drivers I see their acoustical power graphs drop off pretty quickly after 1000Hz, and the bat/owl ears start to repeat.
"Above a few hundred Hz, the line filling material completely absorbs the driver backwave, giving the TL an open, non-boxy sound.” ... which doesn't seem to match Hornresp results where adding stuffing doesn't really eliminate those peaks/dips.THOR: A D’Appolito Transmission Line | audioXpress
"Above a few hundred Hz, the line filling material completely absorbs the driver backwave, giving the TL an open, non-boxy sound.” ... which doesn't seem to match Hornresp results where adding stuffing doesn't really eliminate those peaks/dips.THOR: A D’Appolito Transmission Line | audioXpress
Yes, although I suspect David uses slightly different damping coefficients in his software while the models on here will depend on the quantities the individual designer has applied in that particular case. The Thor was based on the d'Appolito alignments, which lean toward a 'pure' max-flat impedance TL design rather than being high[er]-gain varieties.
Scott, Can you clarify? By that do you mean the Thor is based on a more heavily stuffed design? Or something else?
Thanks,
Eric
Basically, there is no single type of TL alignment for a given driver, in the same way there is no single vented box alignment. There are lots of (technically an infinite number) of different alignments that get lumped under the generic title, and within reason, you go with what best suits your particular requirements.
The Augspurger derived alignment that d'Appolito used for the Thor is an acoustically well-damped type targeting a relatively flat impedance, no more than 1dB drop on the third harmonic, and less than 0.5dB deviation above that. In essence, they lean toward a near-aperiodic line with a bit more gain than a sealed box, but are not high-gain lines as such. They are typically quite heavily damped (stuffed) to achieve that target objective. So they don't have as much output on the low end as some, but they do present a relatively unreactive load, and the extensive line damping largely eradicates any likelihood of early reflections modulating the driver's moving components or passing through any acoustically transparent surfaces (suspension, some cones etc.).
The Augspurger derived alignment that d'Appolito used for the Thor is an acoustically well-damped type targeting a relatively flat impedance, no more than 1dB drop on the third harmonic, and less than 0.5dB deviation above that. In essence, they lean toward a near-aperiodic line with a bit more gain than a sealed box, but are not high-gain lines as such. They are typically quite heavily damped (stuffed) to achieve that target objective. So they don't have as much output on the low end as some, but they do present a relatively unreactive load, and the extensive line damping largely eradicates any likelihood of early reflections modulating the driver's moving components or passing through any acoustically transparent surfaces (suspension, some cones etc.).
Perhaps this is what you are looking for (a Safairi archive, should be openable in any web browser).
dave
So I put a 1" full-range (Tang Bang W1 1070SH) into Hornresp and got a result that wasn't that interesting.
Then I started playing with some of the sliders and got a freq response that is much flatter and wider bandwidth, except it's a very strange taper shape.
Baseline is a 10:1 taper, the flatter red line is the diamond shaped taper...
How to explain this? Even when Fb and Volume are kept more or less the same, the diamond taper maintains a flatter response. Is this just a case where the modelling stops being accurate?
An externally hosted image should be here but it was not working when we last tested it.
Then I started playing with some of the sliders and got a freq response that is much flatter and wider bandwidth, except it's a very strange taper shape.
An externally hosted image should be here but it was not working when we last tested it.
Baseline is a 10:1 taper, the flatter red line is the diamond shaped taper...
An externally hosted image should be here but it was not working when we last tested it.
How to explain this? Even when Fb and Volume are kept more or less the same, the diamond taper maintains a flatter response. Is this just a case where the modelling stops being accurate?
Well, a proper explanation probably requires way more math skills than I have, but basically the long vent of the latter makes it a MLTL, so has much more acoustic loading around/at tuning and why they've been my default high SQ vented cab alignment since '65.
No, T/S theory begins and ends at:
Fhm = 2*Fs/Qts'
Flc = Fs*Qts'/2
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
Some programs will calculate to a higher frequency if either inductance and/or added resistance is inputted, but even then it's only accurate out to ~ [Fs*8 pi] in Hornresp. No clue about others, though ones that allow inputting measured responses probably are accurate 'enough'.
GM