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Does it make sense to keep this Sub ?

Kachda

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I recently bought a JBL Stage A120P subwoofer. Today, I measured the output of the sub by itself, and the speakers without the sub. Both measurements were done at the same SPL level, with the sub set to medium gain.

The sub (blue line) provides some SPL at ~55Hz, but drops off quite sharply below that. My speakers without the sub are able to have some useful output around 55Hz.

Based on this I think this particular sub isn't the right fit for my system. I should look for a sub that can provide some useful output at 40Hz or below, which this sub doesn't seem to do. Would this conclusion be correct ?
kefr3vssub.png
 

chuckt62

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No, but bump it up 3db.

ETA
answer was based on thread name, then you reversed the question, so no & yes.
 

DVDdoug

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If you push them louder the sub may go louder without distortion.

And if you have a home theater system the "point 1" LFE channel ONLY goes to the subwoofer so you'll lose the low frequency effects without it,
 
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Kachda

Kachda

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If you push them louder the sub may go louder without distortion.

And if you have a home theater system the "point 1" LFE channel ONLY goes to the subwoofer so you'll lose the low frequency effects without it,
I run it in a stereo system, no LFE channel here.

Unfortunately I cannot find any test of this sub that shows what the distortion is. And ultimately it doesn't provide what I was looking for, the feeling of bass that you get in the 20-40Hz range. Probably better off spending a bit more for a SVS 1000 Pro.
 

chuckt62

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That's funny I was just going to show my SB1000-pro plot from this afternoon:
12.2-SB1000-PRO.jpg
 

chuckt62

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They have some in the outlet with a $100 discount.
 
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Kachda

Kachda

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By setting the gain on the sub to the 9 o' clock position, I can get some useful output at 30Hz, though the 55 Hz output is much higher than the speakers. But I can use DIRAC to bump that down.
11.png
 

alex-z

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Have you experimented with different positions? You might be able to move that response peak at 55Hz.

The sub is still useful even though it doesn't play low. You get less overall bass distortion, and a more consistent seat to seat response.
 
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Kachda

Kachda

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Have you experimented with different positions? You might be able to move that response peak at 55Hz.

The sub is still useful even though it doesn't play low. You get less overall bass distortion, and a more consistent seat to seat response.
Dont have a lot of flexibility with the placement, but I’ll try. Thanks for the suggestion.
 

YSC

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the slope down seems a bit weird for the sub this size, would it be a boundary cancellation?
 
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Kachda

Kachda

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the slope down seems a bit weird for the sub this size, would it be a boundary cancellation?
I’ll measure it from a different position to see if it’s the room or sub. If it’s the sub it’s a true one note wonder.
 

DWPress

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First I would say it's not a good match but a couple things:

You say you have Dirac but then why the humps at 65 & 280 and dip at 160Hz? Seems like those would have been smoothed down assuming the rest of your sweep tapers down from 80-85dB. Same SPL level measured how? The first sweep at "medium gain" is set too low while "9 o'clock" is too high - a difference of 10dB. Try "7:30-8 o'clock" and remeasure. With a bit of Dirac magic or simple PEQ the JBL could be a lot more optimized for your space.

Just because @chuckt62 got that response from the SB1000 in his room doesn't mean you'll get it in yours. If you've got a bigger room you might need 2 subs. I am partial to the SVS sub I have but it compliments another bigger one in a 4225 cubic foot room.
 

sigbergaudio

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The sub is rated to 35hz, so it's probably at least 6dB down at 35hz, which corresponds with your measurements. Then the peak at ~45-80hz makes it look worse than it is.

I'd say your placement is actually quite good as you have lots of free output in that wide peak from 45-80hz where there's lots of punch in the music. Judging from your responses you have Dirac, so I'd use that to roll off the mains, and then use EQ and/or automatic room correction to make the sub flat, and you will have lots of free headroom.

If you don't typically play very loud, the sub can probably handle a bit of lift around 35hz too. And perhaps try to cross over the sub even higher to fill out some of the dip in the 100-200hz area.

So you could attempt to shape something like this (not sure exactly what's the right level for the sub here since you haven't measured the full respons, and it's somewhat a matter of taste as well, but as a start):

1654494027651.png
 

More Dynamics Please

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JBL specifies the low frequency for the Stage A120P as 32 Hz. When JBL does not include a -X dB with a low frequency rating it's safe to assume it's most likely -10 dB, a number which is cited in many of their other speaker specs.
 
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Kachda

Kachda

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JBL specifies the low frequency for the Stage A120P as 32 Hz. When JBL does not include a -X dB with a low frequency rating it's safe to assume it's most likely -10 dB, a number which is cited in many of their other speaker specs.
Thia makes sense. The difference between the 55Hz and 32Hz level is about 10db.
 
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Kachda

Kachda

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The sub is rated to 35hz, so it's probably at least 6dB down at 35hz, which corresponds with your measurements. Then the peak at ~45-80hz makes it look worse than it is.

I'd say your placement is actually quite good as you have lots of free output in that wide peak from 45-80hz where there's lots of punch in the music. Judging from your responses you have Dirac, so I'd use that to roll off the mains, and then use EQ and/or automatic room correction to make the sub flat, and you will have lots of free headroom.

If you don't typically play very loud, the sub can probably handle a bit of lift around 35hz too. And perhaps try to cross over the sub even higher to fill out some of the dip in the 100-200hz area.

So you could attempt to shape something like this (not sure exactly what's the right level for the sub here since you haven't measured the full respons, and it's somewhat a matter of taste as well, but as a start):

View attachment 211148
Thank you. This is exactly what I was intending to do. I was measuring the raw response of the sub and main prior to applying DIRAC in order to level match their SPL. That is when I noticed that the response (at least in the in-room response), is quite peaky and at a frequency which my mains can already deliver. Which is why I was wondering whether it would make sense to get another sub that can provide a flatter response (before in room effects) like the SVS 1000 PRO.

Since I can't find any measurements of this particular sub, I am not sure if the peaky behaviour is room driven or not. I will shift the position to try and see whther the peak changes.
 

sigbergaudio

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Thank you. This is exactly what I was intending to do. I was measuring the raw response of the sub and main prior to applying DIRAC in order to level match their SPL. That is when I noticed that the response (at least in the in-room response), is quite peaky and at a frequency which my mains can already deliver. Which is why I was wondering whether it would make sense to get another sub that can provide a flatter response (before in room effects) like the SVS 1000 PRO.

Since I can't find any measurements of this particular sub, I am not sure if the peaky behaviour is room driven or not. I will shift the position to try and see whther the peak changes.

It's almost certainly the room. You will find other subs that go deeper, but the peak is very likely the room.
 
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