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In Reply to: RE: Bull-Nosed Horn Project posted by djk on October 07, 2014 at 00:45:07
djk,A couple more questions if I may. You never know unless you ask!
Is there any possibility that the self cancellation of harmonics also extends to the input signal itself?
I'm sure you have listened to straight conical or tractrix mid/bass horns before. How do you rate them as compared to the PPSL and the LS bassbin?
Last night I was listening to Neil Young's, "Live at Massey Hall" on my modified LS's. Half of that album is just him on the piano. You know how when you are close to a piano being played you can hear and feel the sound board resonate? I swear to God it sounded/felt like a piano soundboard was right in the room with me. Totally amazing. I would hate to give that illusion up. I vent this, because terms like, Push-Pull, self cancellation of the second harmonic, and more pronounced third harmonic make alarm bells clang wildly in my head. In fact, they fill me with fear and loathing.
I do try to EQ the 140hz peak, but my equalizer has a 120Hz slide, so I can only adjust it a couple of db.
I guess I am just going to have to take a drive up to Marrieta, GA and take a listen to Les Hudson's versions. Of course, you never really know till you get them home. Do you think that one day you will allow him to build the Bull-Nosed version?
Thanks,
Jamie
Big speakers and little amps blew my mind!
Edits: 10/10/14Follow Ups:
"Is there any possibility that the self cancellation of harmonics also extends to the input signal itself?"
Of course not!
"I'm sure you have listened to straight conical or tractrix mid/bass horns before. How do you rate them as compared to the PPSL and the LS bassbin?"
This is what I use on top of my PPSL.
http://i56.photobucket.com/albums/g196/dkleitsch/CoePA-2009.jpg
"In fact, they fill me with fear and loathing."
Just means you need to learn more to lose your fear.
Hi djk,
"This is what I use on top of my PPSL."
LOL, I gotcha!
In one of your posts you said there were similarities in the arguments about differential amps, and I mistook that for a push pull amp, and I spent some time thinking in the wrong direction. I don't know any of the technical arguments regarding differential amps. I think I read something by Broskie about long tailed pairs. The following is what I came up with vis a vis the PP, and it may carry over to differential as they seem to use a lot of negative feedback. Feel free to skip over it.
PP and PPSL both self cancel the second harmonic, but I believe the PP amps increases the third harmonic, and then multiplies it out to higher odd order harmonics. From what I've read about the PPSL they don't change the already present odd order harmonics. The third may be more prominent because the second is reduced, and then only when the bin is "pushed hard." That's a huge difference. I doubt they will get pushed hard too often in the home enviroment. Oh, maybe once. I say, "Good thing they aren't like PP amps!"
Any bassbin that's 105db efficient, can cover a decade, can go up to 400hz, isn't too big, and is lower distortion than an already low distortion front loaded horn is something worth looking at very closely indeed.
I've been wondering about how to upgrade my bins for a long time. I was leaning toward a straight horn, but it would be too directional being three and a half feet long. I like my horn system to spread the music some. I'm guessing that the PPSL would be less directional?
Another poster mentioned the late great JMLC. Seven years ago I read an interview with him, and he said that he kept two sets of mid horns. One for listening by himself, and one for guests. At the time I thought that was absurd, but now I know exactly what he meant.
What is the difference between four 8", two 12", and two 15" drivers? Just the low cutoff? I noticed in your link that you had the bottom vent on the side.
I congratulate you on your excellent work. It may turn out to be a giant horn killer.
Jamie
Big speakers and little amps blew my mind!
"From what I've read about the PPSL they don't change the already present odd order harmonics."
For the most part.
The low-pass action of the plenum will roll-off higher harmonics at about 12dB/oct, so with careful design you can get some reduction in 3rd (and higher) harmonics at the cost of bandwidth.
"The third may be more prominent because the second is reduced, and then only when the bin is "pushed hard." "
In practice, no.
What does happen is it sounds fine up until the amplifier clips and then the 3rd sticks out like a sore thumb as it goes straight up from the clipping. If of brief duration in live music it seems to be a non-issue, with RAP and its steady drone notes it can sound horrible (use an amp wih a clip-limiter).
"I'm guessing that the PPSL would be less directional?"
At low frequencies, yes.
The Di at higher frequencies increases as much as 3dB as the radiation changes from 2Pi to 1Pi as controlled by the width of the front panel (around 200hz usually).
"What is the difference between four 8", two 12", and two 15" drivers? Just the low cutoff?"
Pretty much.
The quad driver set-up looks way cool, and usually gets "WTF is that" remarks.
"I noticed in your link that you had the bottom vent on the side."
Whatever works the best for you, cosmetics, etc.
"I congratulate you on your excellent work. It may turn out to be a giant horn killer."
Thanks, I don't build bass horns anymore, just mid-bass/midrange and HF horns.
Hey Dennis,
Just for fun-
What would happen to the numbers if you used sealed back drivers? :) Probably ruin the push pull effect.
Yes I have an unhealthy fixation with efficiency. I know that now. That's why I'm in this place, for help.
Jamie
Big speakers and little amps blew my mind!
That is a silly question.
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