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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 5:09 pm 
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Joined: July 9th, 2016, 7:23 pm
Posts: 30
Location: Fairfax Station, VA
Cogito wrote:
Again from Altec literature:
Quote:
A characteristic feature of the sectoral horns is a beam width in the horizontal plane that is constant through the middle and high frequency range. Other horn types (except the multicellular horns) passes beams that become progressively sharper as the frequency increases, and generally cover a narrow area at the high frequencies.


Probably directionality of the higher frequencies is the reason almost all the direct radiating speakers have very small sweet spot for soundstage imaging.

I am not suggesting that sectoral are better than other horns or speakers of any other kind. Just trying to understand. What sonic characteristics of sectoral (not just 511Bs) horns is considered flawed?


In diffraction horns, diffraction is used to "spread" the sound. However, a diffraction is an impedance discontinuity. It causes reflections that reach the listener at different times, smearing the image, just as sharp edges at the edge of a baffle do. Impedance discontinuities also cause reflections back to the diaphragm and what that entails. If looking for controlled directivity as a priority, the Geddes OS waveguides or Minphase horns offer that with the least amount of diffraction.

The same goes for the horn's mouth. Large roundovers minimize impedance discontinuities. They will be delayed longer when reflected back to the diaphragm. However, according to Geddes, impedance discontinuities (changes in slope) near the throat are more detrimental to creating High Order Modes (HOMs) that are basically sound waves that, by bouncing around in the horn, take a longer path to your ear.


Last edited by Pooge on August 8th, 2016, 5:16 pm, edited 1 time in total.

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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 5:11 pm 
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Joined: July 17th, 2016, 6:24 am
Posts: 1099
J-ROB wrote:
Job #1 for a pro horn is dispersion control, i.e. defined coverage. The Altec sectorals will give you that. You got to light up the seats or else you failed.

They were obviously quite successful and in production for many years. Possibly the most popular and commonly-used horn of all time.

I am a bit puzzled that these rather-average horns were used in major recording studios but a primary characteristic of a recording studio monitor is to be predictable and repeatable, and Altec sectorals were that. An overgrown Yamaha NS-10, sorta. And they do resolve a lot of "detail," particularly compared with most of the other 50s-60s gear. They did the job to the satisfaction of top pros, it seems. Sounding too good is often cited as a drawback for a monitor.

Altec's generally, and the 511/811s specifically, wide acceptance and long reign in pro audio is testament to the fact that they knew what they were doing and many pros agreed.

The Altec engineers weren't designing for audiophiles per se, but they did come up with some excellent parts for home listeners to re-purpose. However, you have to evaluate the stuff carefully on a case by case basis--- just like everything else.


Thx for the explanation.


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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 7:09 pm 
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Joined: July 8th, 2016, 4:34 pm
Posts: 570
Has any of you tried to make a diy horn (especially the critical throat region) with a 3d printer.


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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 7:15 pm 
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Joined: December 14th, 2013, 2:19 pm
Posts: 948
That's actually a great idea.

I may put it on my short list, once I perfect the Lynda Carter model I've been working on.


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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 7:33 pm 
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Joined: July 24th, 2015, 4:17 pm
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Location: Parkville, Maryland
Check with Joe Stromick of JS Audio. Lynda Carter lives in Bethesda. :shhh:

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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 7:34 pm 
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brombo wrote:
Has any of you tried to make a diy horn (especially the critical throat region) with a 3d printer.


This speaker was one of the entries at this year's Midwest Audiofest design competition. Although not a horn it was done with 3D printing. The upper and lower sections were done with different materials added to the plastic to achieve different densities. It sounded quite good. I'm sure someone could build a horn that way.


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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 7:36 pm 
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Not the 90 year old version. You are sick!

I'm talking Wonder Woman years.

That's not sick. Right Roscoe?


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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 7:40 pm 
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Stuart Polansky wrote:
That's actually a great idea.

I may put it on my short list, once I perfect the Lynda Carter model I've been working on.


So the discussion about damping with rubber is useful after all!

One of the guys I'm meeting in Korea this week just submitted his PhD thesis on horn simulation. While much is well known, such as the above info that Geddes translated into his proprietary jibber-jabber, I have not found much in the way of a succinct overview. I'll talk to my friend about this.

One super smart guy who worked with these questions a lot is Jean Michael L'Cleach, who went on to join the ancestors last year, sadly.

Some interesting points in his 2010 ETF lecture

http://www.rintelen.ch/download/JMMLC_h ... _etf10.pdf


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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 7:56 pm 
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Joined: July 9th, 2016, 7:23 pm
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Location: Fairfax Station, VA
Don't know how good 3-D printing is right now. Don't know if you can get a fine enough resolution for the throat yet. I had thought of using it for a phase plug, but heard the printing has a minimum step size. Also, the throat walls should be very rigid. Can the 3-D "ink" meet that criteria?

Geddes top priority is pattern control and home theater. He doesn't care about acoustic load. As one who prioritizes pattern control, he's made some good engineering choices.

LeCleach did concern himself with acoustic loading, low diffraction, and wave front characteristics. I have been trying to get a custom made LeCleach made for several years. Note that off-the-shelf horns don't necessarily have a throat with an opening angle suitable for any driver, even though the opening matches the exit opening of the driver. It should also match the exit angle of the driver.

Not easy to find someone in this country to route a horn with that degree of specification or size, for something less than a second mortgage. I found someone in Hungary, but not ready to take that leap, yet.


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 Post subject: Re: Hello
PostPosted: August 8th, 2016, 8:29 pm 
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Joined: April 20th, 2014, 5:21 pm
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You can make a workable gun 3-D print, so why not a throat?

The question of throat angle vs exit angle of driver is one of the aspect of horns I want to know more about. I understand that they should match but say you have a 2" horn and a 1" exit on the driver with given exit flare. How to optimize that throat flare? I'll chat up Bjorn on the subject, see if I can learn something.

Horns were always mostly about pattern control. I think the early work by Western Electric scientists, who invented and formalized most of the basics, came out of the mindset of network engineers. They were trying to optimize acoustic impedance matching for power transfer like the WE engineers did for telephone lines and 600 ohm studio lines...but the first theater amps were two watt PP 205Ds!

With cheap watts, who cares anymore?

Martin from Azura is a cool guy. Ask him what he can do.


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