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Multi-Way Conventional loudspeakers with crossovers

Newbie SR71 build
Newbie SR71 build
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Old 11th November 2017, 04:41 PM   #1
djcantr is offline djcantr
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Default Newbie SR71 build

Ordered a Zach SR71 kit. Wanting to build into towers with a false bottom. Read somewhere (may not be exactly correct) that Krutke said if not building with the Madisound MD14 enclosure he would build it to 16 liters and tuned to 40hz instead of 44hz. I calculated cabinet drawing to 14.926 liters, I assume difference is because I did not factor in driver or port displacement. Am I right to think I should keep baffle width the same and increase depth and height slightly to get to 16.926 liters? Then driver and port displacement would get me to a net 16 liter volume? What length should the port be to tune to 40hz?
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Old 13th November 2017, 09:14 AM   #2
Moalboal is offline Moalboal
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Baffle width and driver placement should be as close as possible to the original design. You could probably extend the baffle below the midwoofer if necessary. Check out Audioexcite for some info: www.audioexcite.com >> ZaphAudio ZA-SR71 Review!
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Old 13th November 2017, 12:57 PM   #3
Michael Chua is offline Michael Chua  United States
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Quote:
Originally Posted by djcantr View Post
Am I right to think I should keep baffle width the same and increase depth and height slightly to get to 16.926 liters?
Yes, keep to the same width. If you make it wider, the baffle step will change.

I wouldn't worry too much with the increase in volume. 15L to 17L is marginal to the bass response. My ER18RNX is in a 15L ported box with a tube of 2" in diameter, 6.25" length.

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Mike
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Old 13th November 2017, 11:58 PM   #4
djcantr is offline djcantr
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Thanks for the responses, guys.

Years ago when I was into car audio when we would build sub enclosures we would subtract the displacement of the sub and port. So if we wanted a 2 cubic foot ported enclosure might have to build it to 2.2 cubic foot because the sub and port were calculated to displace .2 cubic foot of volume. Sure, some of the motor assemblies on those subs were pretty big. So in home audio are the displacement of the drivers and port not calculated and considered when designing the cabinets? Sorry if that seems like a dumb question, I just expected to have to subtract those from the volume but I’m not seeing anybody talk about that in anything I’ve read going into this project.
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Old 14th November 2017, 01:39 AM   #5
Dissi is offline Dissi  Switzerland
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The volume taken by drivers and port always has to be considered. But since cabinet damping also increases the effective volume, there's usually not much difference in the end.

My simulation program calculates for the SR71:

Geometric volume: 14.927 liters
Drivers and port subtracted: 14.056 liters
Volume increase of damping added: 14.759 liters
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Old 14th November 2017, 02:55 AM   #6
djcantr is offline djcantr
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That makes sense now. Thank you guys for answering my questions. Can't wait to finish this project and give these a listen!
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