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Multi-Way Conventional loudspeakers with crossovers

sb23nrxs45-8 simulations and reality
sb23nrxs45-8 simulations and reality
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Old 4th August 2020, 10:50 PM   #11
AllenB is offline AllenB  Australia
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sb23nrxs45-8 simulations and reality
It is important to separate the room from the speakers when you measure. Since you are testing the box alignment you need to hear nothing but the box. Bring the speaker into the room and put the mic right next to the speaker.
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Old 5th August 2020, 06:32 AM   #12
GM is offline GM  United States
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Originally Posted by KitQ View Post
I now think that they cancel each other in this region..........
You're right, take it out of the room, it's acting as a passive radiator.

Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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Old 5th August 2020, 12:51 PM   #13
hifijim is online now hifijim  United States
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Two things come to mind:

1) exactly what Allen B said... For low frequency measurements, do a near field measurement of the woofer, and a near field measurement of the port. I forgot the exact math on how the two responses are added together, but an internet search will tell you. The alternative way (which is both better and more difficult), is to take them outside on a large flat surface (i.e. driveway) and do a ground plane measurement.

2) measure the T/S parameters of your drivers. This is what denbret was getting at. In most cases, the sample to sample variation among drivers is such that the Fs, Qts, and Vas variations tend to cancel each other out. This is almost always the case with a sealed box, and most of the time it is true for vented alignments... but it is worth checking
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Old 5th August 2020, 02:47 PM   #14
hweb is online now hweb
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At low frequencies (<100Hz) the room almost always dominates the speaker response (in most domestic settings, anyways - a large hall or gym might differ). If you want to prove this out, move the speakers to another room with different dimensions (preferably one with different ceiling height). You'll probably see vastly different response.

BTW - This is the reason why I generally just build sealed enclosures for low bass and EQ as the room necessitates. Below ~100Hz the room is in charge.
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