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Author Topic: Replace my Danley TH115's with...?  (Read 2562 times)

Douglas R. Allen

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Re: Replace my Danley TH115's with...?
« Reply #20 on: July 19, 2021, 06:02:15 AM »

   I've often thought about tapped horns and how I do have very basic understanding of how they work. With the experts here I was wondering about the concept so thought I would ask. As a tapped horn takes both the front wave and back wave of the subwoofer , the back wave would be 1 cycle off correct? The back wave has to go though the box, through the port/horn length and exit the front to be in phase with the 2nd wave coming out of the box. This distance has to be at least roughly 1/2 wavelength for it to be in phase with the front's wavelength. This distance combined with the rear wave being 180 degrees out of phase with the front is enough so it is in phase with the next wave the front is reproducing.  So the start/stop of the first/last wavelength will have 2 starting and departing waves of a signal. Sort of like some cardiod subwoofer setups of course without the benefit of cardiod rear rejection. I truly doubt this can be perceived by a listener but at the same time if a single wave is put into a tapped horn 2 waves are coming out? The first wave and the rear wave later?  I've often wondered if this is somehow noticed by some and not others?
   I feel , at least when the horn length is correct for the frequency going through it this would be a none issue. But if the sub is used maybe higher in frequency than the horn length this may cause some issues with some cancellation? Like 2 subs not in alignment where the lower frequencies are large enough ( closer than 1/4 wavelength ) but the higher frequencies are not?   
 
   Thanks for any input;
      Douglas R. Allen
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David Sturzenbecher

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Re: Replace my Danley TH115's with...?
« Reply #21 on: July 19, 2021, 10:45:24 AM »

   I've often thought about tapped horns and how I do have very basic understanding of how they work. With the experts here I was wondering about the concept so thought I would ask. As a tapped horn takes both the front wave and back wave of the subwoofer , the back wave would be 1 cycle off correct? The back wave has to go though the box, through the port/horn length and exit the front to be in phase with the 2nd wave coming out of the box. This distance has to be at least roughly 1/2 wavelength for it to be in phase with the front's wavelength. This distance combined with the rear wave being 180 degrees out of phase with the front is enough so it is in phase with the next wave the front is reproducing.  So the start/stop of the first/last wavelength will have 2 starting and departing waves of a signal. Sort of like some cardiod subwoofer setups of course without the benefit of cardiod rear rejection. I truly doubt this can be perceived by a listener but at the same time if a single wave is put into a tapped horn 2 waves are coming out? The first wave and the rear wave later?  I've often wondered if this is somehow noticed by some and not others?
   I feel , at least when the horn length is correct for the frequency going through it this would be a none issue. But if the sub is used maybe higher in frequency than the horn length this may cause some issues with some cancellation? Like 2 subs not in alignment where the lower frequencies are large enough ( closer than 1/4 wavelength ) but the higher frequencies are not?   
 
   Thanks for any input;
      Douglas R. Allen

I personally do feel that the late arriving energy through the horn is audible to some degree.  For this reason, I personally feel that the DBH-218 as well as the BC-218 (the main non-TH danley subs I am familiar with) have better "impact" then those in the TH lineup.
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Ivan Beaver

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Re: Replace my Danley TH115's with...?
« Reply #22 on: July 19, 2021, 10:53:45 AM »

   I've often thought about tapped horns and how I do have very basic understanding of how they work. With the experts here I was wondering about the concept so thought I would ask. As a tapped horn takes both the front wave and back wave of the subwoofer , the back wave would be 1 cycle off correct?
The polarity between the front and rear of the driver is 180* or 1/2 cycle off, NOT 1 cycle.

The tapped horn works because both sides of the driver are being used (in a front loaded/ported cabinet only 1 side of the cone is being used).

There is an issue with the tapped horn design, as with all other designs.  Everything has a compromise

The tapped horn idea only works over the lower 2 octaves or so.  So as you go higher (out of the intended response of the cabinet or the intended freq bandwidth), the path lengths vs freq wavelengths falls apart, and the sound can get a little "wonky".  As a general rule, as long as you low pass them below 100hz (or a little higher if needed) you will avoid or greatly diminish the effect, which is basic combfiltering on the higher, out of band freq.
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Mark Wilkinson

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Re: Replace my Danley TH115's with...?
« Reply #23 on: July 19, 2021, 03:13:12 PM »

In case you haven't seen, or like me, forgot about this paper ...http://www.danleysoundlabs.com/wp-content/uploads/2012/01/The-Tapped-Horn.pdf
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Douglas R. Allen

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Re: Replace my Danley TH115's with...?
« Reply #24 on: July 19, 2021, 03:16:39 PM »


The polarity between the front and rear of the driver is 180* or 1/2 cycle off, NOT 1 cycle.


   Sure, that's a given. The added length of the horn is another 1/2 cycle so the wave exit's 1 cycle behind but in phase with the next wave. I wasn't sure if the horn length was set to match the highest frequency of the intended bandpass like 100hz and the lower frequencies would be still "close enough" due to the size of their wave or if the horn's internal length was based on a lower frequency. Sadly I have yet had the chance to hear one in the wild if you will. The design certainly gets high output out of a smallish box with great response.

   Douglas R. Allen
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Martin Morris

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Re: Replace my Danley TH115's with...?
« Reply #25 on: July 19, 2021, 07:06:05 PM »

The polarity between the front and rear of the driver is 180* or 1/2 cycle off, NOT 1 cycle.

The tapped horn works because both sides of the driver are being used (in a front loaded/ported cabinet only 1 side of the cone is being used).

There is an issue with the tapped horn design, as with all other designs.  Everything has a compromise

The tapped horn idea only works over the lower 2 octaves or so.  So as you go higher (out of the intended response of the cabinet or the intended freq bandwidth), the path lengths vs freq wavelengths falls apart, and the sound can get a little "wonky".  As a general rule, as long as you low pass them below 100hz (or a little higher if needed) you will avoid or greatly diminish the effect, which is basic combfiltering on the higher, out of band freq.

Ivan

The upper band - between 100 - 200 hz - looks good as a raw response ... or were there any filters used in the TEF  measurement? - I've measured a few DIY full horns and a couple of tapped horns, and some have looked a lot worse above 100 Hz than the TH115 does.

Back to Ryan's system, how high could you extend the X over point to relieve the strain on the 12's in his top boxes?

Cheers
Martin
« Last Edit: July 19, 2021, 10:38:17 PM by Martin Morris »
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Caleb Dueck

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Re: Replace my Danley TH115's with...?
« Reply #26 on: July 20, 2021, 10:33:54 AM »

I personally do feel that the late arriving energy through the horn is audible to some degree.  For this reason, I personally feel that the DBH-218 as well as the BC-218 (the main non-TH danley subs I am familiar with) have better "impact" then those in the TH lineup.

My experience as well.  There aren't many applications where a large cluster of DBH, DBH -LC, or BC subs won't bring a huge smile. 
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Ivan Beaver

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Re: Replace my Danley TH115's with...?
« Reply #27 on: July 22, 2021, 09:47:31 AM »

Ivan

The upper band - between 100 - 200 hz - looks good as a raw response ... or were there any filters used in the TEF  measurement? - I've measured a few DIY full horns and a couple of tapped horns, and some have looked a lot worse above 100 Hz than the TH115 does.

Back to Ryan's system, how high could you extend the X over point to relieve the strain on the 12's in his top boxes?

Cheers
Martin
There are no filters or processing of any type in the TEF measurements.  Just the output of the TEF into a power amp
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Ivan Beaver
Danley Sound Labs

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ProSoundWeb Community

Re: Replace my Danley TH115's with...?
« Reply #27 on: July 22, 2021, 09:47:31 AM »


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