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Tapped horn sub for Belle’s


Vince1966

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23 hours ago, Vince1966 said:

Im hoping Mrs. Clause brings me a new Trac Saw for the Cabinet builds,

That's the only way to go.  You'll be amazed at how accurate they are and how much easier they are to use than a table saw, especially for ripping full sheets.

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On 12/21/2020 at 8:48 AM, CECAA850 said:

The exact placement of the driver dictates that both waves will be in phase with each other though.

 

 

In phase yes, Carl, but still time lagged and cannot be corrected. Therefore any time there is a tonal change, it will have milli seconds of smear of the last note as the second wave exits the horn. Is this noticeable? For most, I would say the brain corrects for this but I am certain you would notice it in an A/B comparison with a true horn sub just like your brain corrects for time misalignment and you don't notice it until you A/B with time alignment.

 

That big a deal, probably not but I think we all strive for the closest to perfection that we can achieve. This is for someone with plenty of extra space... :D

 

Rog

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32 minutes ago, twistedcrankcammer said:

In phase yes, Carl, but still time lagged and cannot be corrected. Therefore any time there is a tonal change, it will have milli seconds of smear of the last note as the second wave exits the horn. Is this noticeable? For most, I would say the brain corrects for this but I am certain you would notice it in an A/B comparison with a true horn sub just like your brain corrects for time misalignment and you don't notice it until you A/B with time alignment.

 

That big a deal, probably not but I think we all strive for the closest to perfection that we can achieve. This is for someone with plenty of extra space... :D

 

All true, @twistedcrankcammer, but in a real room the time delay generally gets lost in the various reflections that occur. The engineer in me says that they cannot work. The audiophile in me has actually heard a few, and they can sound really good if executed properly. IMHO.

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I'm confused (surprise!) if two waves are in phase how can they be time delayed? Are we saying the first wave form the closer diaphragm is in phase with the second from the further away diaphragm? And the last wave from the closer one has no corresponding one from the further one because it has already stopped? This can be heard?

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4 minutes ago, babadono said:

I'm confused (surprise!) if two waves are in phase how can they be time delayed? Are we saying the first wave form the closer diaphragm is in phase with the second from the further away diaphragm? And the last wave from the closer one has no corresponding one from the further one because it has already stopped? This can be heard?

 

Design details vary, but for the sake of explanation let's assume that the front of the woofer radiates directly into the room while the back of the driver radiates into the pipe. The pipe is (approximately) ¼ wavelength long at the system cutoff frequency, and curls around to exit adjacent to the front of the woofer. Thus, at the system cutoff frequency the front wave and the delayed back wave are -270° apart in phase (-180° to start out with, minus 90° due to the delay), so the response is -3dB for continuous tones. At twice that frequency, the front wave and the back wave are -360° apart (-180° to start out with, minus 180° due to the delay), so the response is 0dB for continuous tones. At higher frequencies the back wave starts to interfere with the front wave, so internal damping is used to attenuate those higher frequencies as they pass through the pipe.

 

That's all fine for continuous tones, but as @twistedcrankcammer pointed out, there is always a "double hit" delay in the transient response. 

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