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Multi-Way Conventional loudspeakers with crossovers

Scaling port response to speaker nearfield
Scaling port response to speaker nearfield
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Old 26th March 2020, 10:59 AM   #11
mecedo is offline mecedo
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Quote:
Originally Posted by mbrennwa View Post
I guess your goal is to scale the sound output (SPL) from the port in order to merge it with the woofer output, correct?

Yes, It is.


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Originally Posted by mbrennwa View Post
As an alternative, I'd recommend the "microphone in box"

I think it's a lot of work with this technique and it's inconvenient. Additionally I have bent tunnel with 90 degree elbow.


There's another technique described here:
https://www.klippel.de/fileadmin/kli...asurements.pdf
Putting mic close to the baffle between speaker and port. But it works only if you have port and speaker on the same plane.
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Old 26th March 2020, 11:01 AM   #12
celef is offline celef
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I have not checked your links but second graph looks most correct
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Old 26th March 2020, 05:07 PM   #13
mbrennwa is offline mbrennwa  Switzerland
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Scaling port response to speaker nearfield
Quote:
Originally Posted by mecedo View Post
I think it's a lot of work with this technique and it's inconvenient.
Uhm, not at all! All you have to do is to put the microphone inside the box, and take the measurement. It's less work than two nearfield measurements (woofer, port), which then need careful merging, and in the end you're not sure if the merging is correct.

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Originally Posted by mecedo View Post
Additionally I have bent tunnel with 90 degree elbow.
Is this a press-fit port that can be unmounted easily? If so: take it out, put the microphone in the box, with the wire going through the port, and reinstall the port. Then take the measurement. Done.
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Old 26th March 2020, 06:30 PM   #14
montana1 is offline montana1  United States
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Hi mbrennwa,
Is this measurement technique the same as you used on the Monkey Box build? If so, it seems like an awesome method to avoid making guesses in how much to scale port when splicing. Im building a larger stand mount currently that has (2) ports on front baffle and its nearly impossible to do an accurate near field measurement of woofer without interference from the ports. This method would solve that problem.

Best Regards,
Rich
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Old 26th March 2020, 07:20 PM   #15
mbrennwa is offline mbrennwa  Switzerland
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Scaling port response to speaker nearfield
Quote:
Originally Posted by montana1 View Post
Hi mbrennwa,

Is this measurement technique the same as you used on the Monkey Box build? If so, it seems like an awesome method to avoid making guesses in how much to scale port when splicing. Im building a larger stand mount currently that has (2) ports on front baffle and its nearly impossible to do an accurate near field measurement of woofer without interference from the ports. This method would solve that problem.



Best Regards,

Rich
Yes, I used this for the Monkey Coffin. It works with any number of radiators (woofers, ports). The original Small paper is a good read (I have a PDF copy).
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Old 26th March 2020, 07:43 PM   #16
montana1 is offline montana1  United States
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Hi mbrennwa,
Is it possible for you to post that Small paper? I would love to give it a read.

Best,
Rich
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Old 26th March 2020, 09:08 PM   #17
mbrennwa is offline mbrennwa  Switzerland
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Scaling port response to speaker nearfield
Hmmm, I had to buy the paper from the AES, and I guess it's possibly not okay to post the PDF for free access. But, wait, it was published 48 years ago, so maybe... aehm, I have no clue. It's probably best if you send me a PM with your email.
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Old 26th March 2020, 09:32 PM   #18
montana1 is offline montana1  United States
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Just sent you a PM.

Thanks so much,
Rich
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Old 26th March 2020, 10:35 PM   #19
gdan is online now gdan  Greece
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Scaling port response to speaker nearfield
Joe D' Appolito wrote a excellent article in audioxpress about methods of low frequency measurements (including Near field and Microphone-in-the-box measurement).

The article is posted on line here:

Measuring Loudspeaker Low-Frequency Response | audioXpress
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