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Old 30th July 2011, 01:05 PM   #2051
Mark Kravchenko --- www.kravchenko-audio.com
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Thanks for the tips Bjørn

( I figured out how to pull off the ø )

The mic looks interesting.

There are some available from this company to:
PCB Piezotronics, Inc.- Sensors that measure up!
Model:
Model 377A12 Spec Sheet

I think the top end for that capsule is 178 db

Don't know the price on it however.

As for the AES papers.

Yes I have a great deal of catching up to do. I have not dove into the AES pool for about ten years. I had all the relevant information on horns and such up to the late 80's but then I started working in the loudspeaker field. Not enough time in the day. You stop studying full time and you end up working full time.

I think a membership with the AES would make the most sense. Quick and easy and no trip to the library required. Can you download off of the AES site?


As for Josh's comments all I can say is I tried an experiment at a small audio meet here in Ottawa last winter. Four subwoofer designs with all the same driver compliment.

Vented
Front Loaded Horn
Tapped Horn
My weird Unhorn ( quasi bandpass in reality )

From measurements and listening I have to say that the tapped horn (which was a true gain enabling design, it had 7 db of gain not just a tappered pipe) had a great deal of out of passband harmonics. We crossed it over with a fourth order at 80 hz using a behringer DCX as a crossover and DEQ set up as a spl meter and RTA. We tried hard to remove the area in reproduction that created the geatest harmonics and it still was very peaky. Some observers liked it. It imparted a rich overtone to the bass. Not true to signal input. The front loaded horn on the other hand played true to it's roots of high volume and low distortion. Again not a sound that everyone liked. A vented box against those performers did it's best but could not keep up.

Some of the observations can be found here:

Winter DIY OTTAWA MEET

An attempt to make all things equal was made.

If some correlation between sound pressure and air particle velocity can be made, maybe we will have a useful tool in the design of horns and their physical dimensional aspect ratios. All these things add up to a better design if attention is paid to the correct details.
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Old 30th July 2011, 11:37 PM   #2052
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Bjorn,
Unfortunately I have not tested any FLH's in the same manner yet. Perhaps someone else has done some but I know of none off hand.
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Old 31st July 2011, 03:31 AM   #2053
GM is offline GM  United States
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Originally Posted by Josh Ricci View Post
The phenomenon I am interested in most is one where the horns output seemingly plateaus in a few narrow frequency ranges and further increases in power produce no further output gains.
High aspect ratio ducts are resistive in nature, so more power = more resistance and one reason why auto, etc., mufflers are 'pancaked', so it seems reasonable to me this is what's causing it, tapered, tapped or not.

GM
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File Type: gif Effect of muffler shape on attenuation.gif (9.1 KB, 203 views)
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Old 31st July 2011, 07:29 AM   #2054
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Originally Posted by mwmkravchenko View Post
So a high power stepped sine wave test should get to the bottom of some of this. Say 1/24th octave short duration bursts.

It will excite the horn to a high pressure point and be traceable as to what frequency is of greatest concern in terms of output distortion.

If these things can be correlated to air speed then we (not me I'm a math imbecile ) may have something useful to model with mathematically.
Hi Mark,

To hopefully assist you in your ongoing investigations, the next Hornresp update will contain three new tools accessible from the SPL response chart window, enabling system efficiency, air velocity and air pressure to be plotted against frequency. Values can also be sampled at specified frequencies, as shown in the attached screenprints.

The update will be released sometime later this week.

Kind regards,

David
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File Type: png Tools.png (26.3 KB, 206 views)
File Type: png Efficiency.png (21.5 KB, 210 views)
File Type: png Velocity.png (21.6 KB, 207 views)
File Type: png Pressure.png (22.1 KB, 206 views)
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Old 31st July 2011, 08:23 PM   #2055
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Originally Posted by David McBean View Post
Hi Mark,

To hopefully assist you in your ongoing investigations, the next Hornresp update will contain three new tools accessible from the SPL response chart window, enabling system efficiency, air velocity and air pressure to be plotted against frequency. Values can also be sampled at specified frequencies, as shown in the attached screenprints.

The update will be released sometime later this week.

Kind regards,

David
Even though I am not Mark....

Wow.

Thank You!
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Old 31st July 2011, 11:01 PM   #2056
Mark Kravchenko --- www.kravchenko-audio.com
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I think I'm Mark.

Mike you are priceless!

This is going to be so much fun. More toys to play with!

I hope that first off I can get an anemometer that will behave.

Second a proper high spl mike that will behave.

Third I hope that as always David calculation consternation's make real world sense.

I have always wondered if there were concrete reason's why some horn folds behave well and some do not.

I think that I'm going to get a little closer to knowing what is what in terms of a optimally folded and designed horn.

So onward and upward.

The math has been lifted off of my little brain.

That leaves the real world of horn path design and then construction.

I have a job where I have to pull off a 20 hz horn with two eight inch drivers in the smallest space available.

Should I be able to do this successfully this will be very interesting.

Thanks again David.

You truly make my life a lot easier.

And I continue to ask the questions.

Now I can find some of the answers.

Sweet!
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Old 1st August 2011, 07:04 AM   #2057
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Default Hornresp Version 28.60

Hi Everyone,

Tools that enable system efficiency, sound pressure (previously called air pressure) and particle velocity (previously called air velocity) charts to be displayed have now been added to Hornresp. The tools are available under the SPL response window. Click on the charts to sample at a specified frequency (press the Esc key to remove sampling).

Please let me know if you find any bugs.

Kind regards,

David
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Old 1st August 2011, 12:55 PM   #2058
Mark Kravchenko --- www.kravchenko-audio.com
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I have been playing with the new version for a little while.

This is really interesting.

I have been comparing a horn path shape I have optimized versus the same horn done through best calculation methods. As in Hornresp spits out an ideal horn.

The differences are very informative.

And I have a couple of ideas of where the greatest difference can be made in the horns usable pressure bandwidth.

Particle velocities are amazingly fast depending on the horn's area. So I think that is where I will start off simulating the differences.

Josh when you get to play with this I'd be interested in your observations as you have pushed your horns hard as well.


A bit more modeling will get to the point where I want to build a box.
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Old 1st August 2011, 02:26 PM   #2059
Mark Kravchenko --- www.kravchenko-audio.com
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Is there any way to run more than one Hornresp at once?

I keep doing screen captures and comparing the differences.

But that is a bit of a pain.
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Old 1st August 2011, 08:18 PM   #2060
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Originally Posted by mwmkravchenko View Post
Is there any way to run more than one Hornresp at once?
Make a second copy of the 3 Hornresp files in a different folder. (Hornresp.exe, Hornresp.dat, msvbm60.dll) You can then start both copies.

You will need to use import/export to keep the two copies of hornresp.dat in sync. Or you can make any changes you want to save in one copy, then exit both and copy the hornresp.dat from one to the other. Be careful and keep backups, sooner or later you will mess it up...

One thing I often do for comparing graphs in Hornresp is to use Paint, the basic image editor included in Windows.

- Produce a graph in Hornresp.
- Capture it to clipboard (Alt-PrintScreen).
- Start Paint, paste (Ctrl-C).
- Produce another graph in Hornresp.
- Capture it to clipboard (Alt-PrintScreen).
- Turn off Draw Opaque in Paint (Image --> Draw Opaque, untick.)
- Paste (Ctrl-c)
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