Okay,so a few days ago i finished my bass modules using these drivers , 37 l , simulated in winisd , tuned to 31 hz , 22 cm long port ... frequency response should fall off smoothly with +1 db boost in bass region according to simulation , with - 3 db at 40 hz . Now , in reality when i play bass sweep the bass starts to play right from 30 hz up to 41 hz then drops in volume between 41-51 hz and starts climbing again fast from 52 hz . Is the reason for this :
a) simulation program sucks
b) it was desigend properly but my room acoustics sucks out bass in that region.
c) the speakers are not broken in and they will fill that hole once they are broken in ( i doubt it )
Should this speaker be tuned to 38-40 hz ?
If anyone has this speaker in simillar sized enclosure please tell me how it behaves and what frequency was it tuned?
a) simulation program sucks
b) it was desigend properly but my room acoustics sucks out bass in that region.
c) the speakers are not broken in and they will fill that hole once they are broken in ( i doubt it )
Should this speaker be tuned to 38-40 hz ?
If anyone has this speaker in simillar sized enclosure please tell me how it behaves and what frequency was it tuned?
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I did further sweeps and tests and here are conclusions :
1) only one speaker playing with port plugged = beautiful steady rise in response from 30 hz without any dips .
2) only one speaker playing with open port = slight dip in 40-50 hz region
3) both speakers unplugged = bigger dip in 40-50 hz , i can hear glass rattle but not much bass.
I dont know what to think of it.Tomorrow i'll try them in a different room.
1) only one speaker playing with port plugged = beautiful steady rise in response from 30 hz without any dips .
2) only one speaker playing with open port = slight dip in 40-50 hz region
3) both speakers unplugged = bigger dip in 40-50 hz , i can hear glass rattle but not much bass.
I dont know what to think of it.Tomorrow i'll try them in a different room.
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yes pretty much , they sit close to each other though .. and when i wrote only one speake playing i meaned that other was disconneted , not that one played with port plugged and other without . Too bad i have only one port plug .I now think that they cancel each other in this region or that maximum response from ports is too low and this software cheats a bit.
Look at the measurements made on the Audiexcite site, they differ from those of the company...
www.audioexcite.com >> SB Acoustics SB23NRXS45-8
www.audioexcite.com >> SB Acoustics SB23NRXS45-8
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
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
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.
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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