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TP12LL34 Duality and positive feedback
TP12LL34 Duality and positive feedback
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Old 8th November 2019, 12:03 PM   #21
Brian Steele is offline Brian Steele  Grenada
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Quote:
Originally Posted by papasteack View Post
It's a simple passive network impedance trick damping back emf.
Doesn't the amplifier already do that?
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Old 8th November 2019, 12:32 PM   #22
papasteack is online now papasteack  France
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Quote:
Originally Posted by Brian Steele View Post
Doesn't the amplifier already do that?
I woud have better said "undamp" since it raise impedance

Last edited by papasteack; 8th November 2019 at 12:39 PM.
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Old 8th November 2019, 12:39 PM   #23
martinsson is offline martinsson  Sweden
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I think we better wait and see how much of a real world noticable issue (or not, my guess) the upper out of band distortion really is in this case, for now I'm more intrested in taking part of the build progress and nedless to say the result, this is Johannes design and build, and I belive it to hold alot of promise.

Tapped pipe (or contant area tapped horn) is a well known principle, and one that is very efficient in relation to the required external volume, if he can add a bit of passband extension and remedy the mid passband dip to some extemt, and spice it up with some midbass punch, all without adding significantly to the build complexity, well then thats progress in my book.
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Old 8th November 2019, 12:54 PM   #24
papasteack is online now papasteack  France
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I would be curious looking around crossover bandwith at REW waterfall response of this kind of design crossed in a full system. At those frequencies, it need to be mesured outdoor, so this make thing complicated.
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Old 8th November 2019, 01:32 PM   #25
Circlomanen is offline Circlomanen  Sweden
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Measurement outdoors in November here on Swedish westcoast might be a little "complicated"....
But I will do my best.

The driver is mounted in the 44 mm baffle and all the internal sharp corners are rounded with a router.
I hope I can measure it tomorrow.
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Old 8th November 2019, 01:52 PM   #26
Brian Steele is offline Brian Steele  Grenada
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What does the displacement-limited theoretical SPL for that design look like? The driver's specs suggest a pro audio 12", and those usually have limited Xmax as compared to say a 12" driver designed for HT subwoofer use.

For comparison purposes, the attached is the theoretical displacement-limited output of a Dayton Audio RSS15HFA 12" driver (14.3mm Xmax) in a damped 175 liter offset TL design.
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Old 8th November 2019, 03:21 PM   #27
Circlomanen is offline Circlomanen  Sweden
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maxsplTP12LL34.JPG

This is the theoretical max spl based on 8 mm xmax and 700 watts of power.
Based on my experience with lots of tapped pipes with lots of positive feedback I would say 120 dB max spl from 23 Hz to 110 Hz with some extra headroom (10 dB) in the mid bass. All in 1,0 Pi radiation angle and without the room gain.

TP12LL34drymount.jpg

Dry mounting of all the parts to see that they all fit before I commit to the build.
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Old 8th November 2019, 03:38 PM   #28
papasteack is online now papasteack  France
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Quote:
Originally Posted by Brian Steele View Post
What does the displacement-limited theoretical SPL for that design look like? The driver's specs suggest a pro audio 12", and those usually have limited Xmax as compared to say a 12" driver designed for HT subwoofer use.

For comparison purposes, the attached is the theoretical displacement-limited output of a Dayton Audio RSS15HFA 12" driver (14.3mm Xmax) in a damped 175 liter offset TL design.
B&C Speakers from first post hornresp pic record label. Nice one .
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Old 8th November 2019, 07:04 PM   #29
Petter Persson is offline Petter Persson  Sweden
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Well... people have been canceling resonances ever since the Voight-horn (or earlier?) was invented. Can you please show an example you've built/designed or listened to where this would been its major drawback?

If a discontinuity in GD in an infinitesimal small interval would be detrimental, it would have shown here for example:

Compound loading 6th order quarterwave "Super Planar" horns and pipes concepts/builds

I reed you like the response of the cab you're building. I've built a couple my self of similar design (though some years ago now...) and I agree with your description. However, I've come to the conclusion that they tend to add its own character to the sound of which I finally got tired of. I don't worry about distortion, they all sounded very clean and impressive (at first). What I did not like after a while were the suck-out at the upper end and the high GD at the lower end.


You're right about that my proposals are more sensitive to folding and driver mounting position. But as performance goes up, tolerances goes down...


GD of your design in gray and the 167-liter version.

Click the image to open in full size.


I don't see any problems with summation, 1/4 wavenength at 172 Hz is still 0,5 meters...


That was that...

Now I'm looking forward to your build and impressions Keep up the good work and let us know what's happening!


Quote:
Originally Posted by Circlomanen View Post
The reason I don´t design speakers like that is seen in the GD graph. Those small kinks in the spl graph might not look like much but is easy to hear in real life.

To sum two resonators outside of the box is seldom a good idea. They compress and become turbulent at different spl and will sum very differently dependent on power input, placement and radiation angle.If you need to adjust to within a cm or two to get a simulated flat response then it does not take much to throw the summation off in real life.

Timing and a good summation is often much more important then a flat spl curve or some small theoretical simulation artifact way above the passband in my experience.
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Old 9th November 2019, 07:43 AM   #30
martinsson is offline martinsson  Sweden
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God morning Johannes, this is your diyaudio wakeup call (in writing) (on a forum) (not the best way perhaps come to think about it)

It's going to wonderful standard grey skies with slight drizzle and just above freezing this morning so get out of bed/coffin/canot (what ever applies) and get to work bringing us some updates on the build, I have been up since 03:30 this morning (true) with rather stale popcorns refreshing this page you know (not so true, but stll).

I have not heard any distant rumbling so far so I thought I'd better check up on the progress.
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