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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 12:21 pm 
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Joined: February 28th, 2013, 3:31 pm
Posts: 169
Cogito wrote:
...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.....

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

Shashi, how many cubic feet are each of these designs? Making a stereo pair?


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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 2:54 pm 
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Joined: October 21st, 2013, 6:53 pm
Posts: 263
Hey Sashi,

I want to try to replicate your performance graphs myself on Hornresp.

Can you please tell me what drivers you are using, and the approx. length of your line?


Thanks,

Chris


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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 7:35 pm 
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Joined: July 17th, 2016, 6:24 am
Posts: 570
Jim G wrote:
Shashi, how many cubic feet are each of these designs? Making a stereo pair?


For 8" drivers is little over 4cft each with the foot print is only about 1sqft for a single fold horn.

With the choice of drivers with only 3.5mm xmax, these subs do not give the feeling of traditional direct radiator subs, as they are moving less than 1/3rd of the volume of air of an equivalent twin 8" radiators. So, the wave pressure level will be significantly lower but the sound pressure level will be same.

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Shashi


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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 7:42 pm 
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Joined: July 17th, 2016, 6:24 am
Posts: 570
Chris,

Drivers: B&C 8PE21-16
Length (L23) = 1/4 wavelength at tuned frequency.

Pay special attention to the diaphragm excursion at the max power level you need. I am getting about 115dB with 12 watts with excursion under 2.5mm. I still have to play around to get the dimensions right.

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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 8:05 pm 
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Joined: January 14th, 2015, 11:15 pm
Posts: 188
Here is a similar TH design. What is interesting is the use of Advantech which you can buy a Lowes.

http://industriumvita.com/folded-tapped-horn-subwoofer-tuned-for-17hz/

If I were going to build a TH, I would consider the 6 fold version of the following design. Scroll to the bottom of the page.

http://wp.volvotreter.de/projects/th-2/the-tangband-30hz-horn/

Does anybody know of windows software that can be used to enlarge such a design so that it can be printed out on multiple sheets of paper?

ray


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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 8:37 pm 
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Joined: July 8th, 2016, 4:34 pm
Posts: 250
This might be interesting for making a midrange horn -

https://www.homedepot.com/p/1-2-in-x-48 ... /205079515

It is quite flexible and could be easily bent to the sides of a rectangular cross section horn. I think the internal damping would be quite high.


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 Post subject: Re: CNC Speaker Design
PostPosted: September 3rd, 2018, 10:11 pm 
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Joined: July 17th, 2016, 6:24 am
Posts: 570
ratbagp wrote:
Here is a similar TH design. What is interesting is the use of Advantech which you can buy a Lowes.

http://industriumvita.com/folded-tapped-horn-subwoofer-tuned-for-17hz/

If I were going to build a TH, I would consider the 6 fold version of the following design. Scroll to the bottom of the page.

http://wp.volvotreter.de/projects/th-2/the-tangband-30hz-horn/

Does anybody know of windows software that can be used to enlarge such a design so that it can be printed out on multiple sheets of paper?

ray


First link is new to me. Alpine is a Car subwoofer.

I am aware of the second link. Choose against it for two reasons: 1) Tagband is a low efficient, long throw, stiff cone woofer suitable for HT usage IMO, 2) multiple sharp folds create reflections which degrade the sound wave.

TH has become popular in HT market. Not as much in stereo usage.

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 Post subject: Re: CNC Speaker Design
PostPosted: September 4th, 2018, 8:28 am 
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Joined: February 28th, 2013, 3:31 pm
Posts: 1061
ratbagp wrote:
Here is a similar TH design. What is interesting is the use of Advantech which you can buy a Lowes.

http://industriumvita.com/folded-tapped-horn-subwoofer-tuned-for-17hz/

If I were going to build a TH, I would consider the 6 fold version of the following design. Scroll to the bottom of the page.

http://wp.volvotreter.de/projects/th-2/the-tangband-30hz-horn/

Does anybody know of windows software that can be used to enlarge such a design so that it can be printed out on multiple sheets of paper?

ray


When I was doing the drawing for the egg template I made a pdf of it and then used the print function in Adobe Reader to enlarge it to the size I needed. In the reader you can select an option that says "print current view" You can move the view around to different sections and print them one at a time. You should allow some overlap to make the joins easier and seamless.


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 Post subject: Re: CNC Speaker Design
PostPosted: September 4th, 2018, 8:54 am 
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Joined: July 8th, 2016, 4:34 pm
Posts: 250
Google -

large format printing near me

and see what pops up.


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 Post subject: Re: CNC Speaker Design
PostPosted: September 4th, 2018, 8:34 pm 
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Joined: February 28th, 2013, 3:31 pm
Posts: 169
Some might like these DIY transmission line subwoofers. They are described in post #7, but the whole thread is an interesting read.
http://www.audioheritage.org/vbulletin/ ... light=3182


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