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General speaker questions for audio and home theater.

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RE: Note that JA

Posted by seancuster71@gmail.com on March 12, 2025 at 16:41:08:
Yes, anechoic chambers are flawed I know some people might not believe it, but it is true. The problem is size bass waves are huge sound travels at 1125 to 1130 feet per second depending on your elevation. Divid the frequency in hertz into 1125 and you get the length of the wave. So, 1125 divided by 20 HZ equals 56 feet. The only anechoic chambers big enough to use for speakers are owned by largest companies and governmental research facilities in the world and are not used for speaker measurements. Leaving use with the fact no room is perfect. The anechoic chambers that are used for speakers are not large enough to measure low frequencies, so the lows are measured outside away from reflecting walls then the measurements are combined. This sounds crazy but it's true.

In 2020 or 2021 if I remember correctly Kipple NFS near field scanner was made available. Kipple is pretty amazing it makes anechoic chambers look like ancient technology. Kipple NFS cost $100,000 sounds expensive, but it is cheaper than building an anechoic chamber large enough to measure speakers.

And to make things even more interesting we can look at Speaker systems that used a combination of anechoic & outside measurements combined have been measured by Kippel NFS and they are accurate so what way is the best? just like old Altec JBL systems pre 1970's these speakers were not measured using the most accurate way which would be (IRM) impulse response measurements and they did not have computers and multiple commercial software available to simulate crossovers. But when old speakers that predate modern design methods are measured with modern equipment and checked for things like step response, impulse response, phase, filter response, group delay, they are 100% accurate.

Nelson Pass talks about JBL crossovers on his Pass DIY site. He says he decided to make some tweaks to a JBL crossover not saying the stock JBL crossover was bad it was the expansional horn that was causing a slightly unwanted effect and Nelson did not want to modify the old JBL cabinet by changing horns. So, he tried to correct this within the crossover, and he talks about how accurate the old school engineers were as it turns out the old school methods of crossover design were just as good as modern methods.

Speaker design combines scientific principles with artistic abilities leading to a blend of engineering and art. combine that with the subjective human perception and you have a fascinating field of study for sure. And that is what hooked me into speaker design and loving the reproduction of recorded sound.