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 Post subject: Re: CNC Speaker Design
PostPosted: September 2nd, 2018, 6:12 pm 
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Cogito wrote:
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I have modeled several Tapped Horns, several Closed Back Horns, and several Transmission lines, but none of these designs have resulted in HORNRESP performance graphs that suggest they have any significant advantage over Infinite Baffle!


If you are looking for better frequency response in horns, you will be disappointed. Typically horns are decade devices, even then too they start beaming on the higher end. In tapped horns, you will be lucky to get 2 octaves of usable bandwidth.

The reason to get horns is their sonic qualities; detailed, extremely dynamic and uncompressed sound which no other type of audio device can replicate.


Horns can be very dynamic, uncompressed, and with high efficiencies but there are other solutions that will give you the same or better results but with a much higher power requirement. The four 15" subs I have in sealed boxes are flat to 10 Hz with DSP EQ and have less than 4% distortion at 106 dB at an 11 ft listening postition at 10 Hz. Their sensitivity is 96dB. They have excellent transient response, low distortion and a low frequency response that cannot be matched with a horn having a mouth size anything less than a large house. However even at 96 dB, sensitivity is lower than a horn. At higher frequencies the horn can also control the radiation pattern lowering early reflections that can mess up coherence but at low bass frequencies the wavelengths are so long that they cannot exercise that control. However, that does not matter because most horn implementations cannot reach very low frequencies. Nothing against horns, but each solution has compromises and no one technology is supreme.


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 Post subject: Re: CNC Speaker Design
PostPosted: September 2nd, 2018, 6:13 pm 
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brombo wrote:
You might consider an acoustic lens at the mouth of the horn to alleviate beaming. JBL used to do that.


Those are cheap and sub-optimal tricks manufacturers resort to keep the costs low and sizes small. We DIYers do not have same limitations.

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 Post subject: Re: CNC Speaker Design
PostPosted: September 2nd, 2018, 6:30 pm 
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They have excellent transient response, low distortion and a low frequency response that cannot be matched with a horn having a mouth size anything less than a large house.


Well, yes and no Tom.

For the most sonically optical horn, you are right, mouth size is impractical for most of us. There are ways around it. Tom Danley applied for patent of Tapped Horn design. Mouth size is very small and lengths are quarter wavelength. By folding, size also becomes WAF compliant. See his white paper here:
http://www.danleysoundlabs.com/danley/wp-content/uploads/2012/01/The-Tapped-Horn.pdf

Quote:
Nothing against horns, but each solution has compromises and no one technology is supreme.


Agreed.

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 Post subject: Re: CNC Speaker Design
PostPosted: September 2nd, 2018, 7:00 pm 
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Joined: July 8th, 2016, 4:34 pm
Posts: 279
Also this -

https://en.wikipedia.org/wiki/File:Elec ... n-1975.jpg

http://www.xlrtechs.com/dbkeele.com/


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 Post subject: Re: CNC Speaker Design
PostPosted: September 2nd, 2018, 8:34 pm 
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Joined: October 21st, 2013, 6:53 pm
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brombo wrote:
You might consider an acoustic lens at the mouth of the horn to alleviate beaming. JBL used to do that.


Is that a tic tack toe kind of thing that splits the sound waves into several narrower paths?


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 Post subject: Re: CNC Speaker Design
PostPosted: September 2nd, 2018, 9:42 pm 
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brombo wrote:


Informative links, thanks.

For home audio, the problem of both FR and beaming can be solved by using multiway horn system like Avant-garde Trio.

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 Post subject: Re: CNC Speaker Design
PostPosted: September 2nd, 2018, 11:02 pm 
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Example of JBL horn with lens -


Attachments:
jblhornlens.jpg
jblhornlens.jpg [ 15.07 KiB | Viewed 1391 times ]
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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 7:51 am 
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Nice paper by Tom Danley. I have know Tom for many years. We recently served as judges together along with Jerry McNutt of Eminence at the 2016 Midwest Audiofest Speaker Design competition. In the photo, from the left is yours truly, Jerry, and Tom.

Looking at the paper what Tom is essentially doing is turning the horn into a ported system. That will extend power output at the tuning point as any ported system will do but will have the same problem with transient response that any ported system will have since the output relies on a pressure wave that is 180 degrees out of phase. The normally good transient response will suffer. As always, there are compromises and no silver bullet.

Also note in his magnitude response graph that the response of that particular horn array starts rolling off at 70 Hz and is down 19 dB at 20 Hz. Forget about low bass. Definitely smaller size though.


Attachments:
MIDWEST AUDIO FEST 2016-117_small.jpg
MIDWEST AUDIO FEST 2016-117_small.jpg [ 459.86 KiB | Viewed 1385 times ]
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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 9:46 am 
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Joined: July 17th, 2016, 6:24 am
Posts: 605
Tom,

Danley's products are geared towards pro-audio and HT markets. His primary design goals seem to be compact size for portability and very high spl around 45Hz for the thundering bass effects. He uses large high excursion and stiff woofers, IOW a typical HT sub driver.

I am taking a different approach. Using two 8" high complaint and small excursion woofers (not subwoofers) in parallel push-pull configuration. My goal is to preserve the micro-dymanics in a low distortion and high efficient horn loaded sub. Hornresp modelling gives me flat 105dB from 35Hz to 100Hz.

Attachment:
IMG_3217.JPG
IMG_3217.JPG [ 99.01 KiB | Viewed 1380 times ]


FR curve is shown with high-pass and low-pass filters applied.
Attachment:
2018-09-03_8-59-22.jpg
2018-09-03_8-59-22.jpg [ 48.01 KiB | Viewed 1380 times ]

Attachment:
2018-09-03_9-32-53.jpg
2018-09-03_9-32-53.jpg [ 44.46 KiB | Viewed 1380 times ]


If this is successful, I might build the 12" driver version which goes down to 25Hz flat.

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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 10:34 am 
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Should be an interesting design for that frequency range. I'll be interested in hearing it.


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