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Discussion Starter · #1 ·
Hi everybody,
I am new to the forum (first post), new to REW and used to make unreliable measurments with any kind of cheap stuff using my engineering background to extrapolate some useful data. Audio isa hobby for me but I take it very seriously, you can see it because I own a bose acoustimass 5 system (I am joking :) I changed countless audio chains, this is a pc audio system made with old stuff, ampli is the final stage of Harman Kardon PM665 feed with sabre ES9023 from hifimediy).

This is a reading with uncal cheap mic, made too low because of neighborhood. I can change anything but peaks and deeps are almost always the same (this is with sub near a corner, under the desk).

I think is due to the kind of sub (dual reflex with third common chamber) with added modal resonance of this stupid too square room (4,4 x 3,6 x 3m) full of stuff around (someone call it a mess but is in fact a very good room treatment for mid-high freqs:)).

I am curious to know if someone else found similar behaviour and I found that graph just interesting enough to be my first post. :)
 

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First of all welcome to the Shack,
The mic you are using do you have a calibration file loaded for it? Otherwise the readings won't be very reliable. The Bose " sub" is not really a sub at all because it barley goes deep enough to handel the sub frequencies. It's better called a bass bin as it's frequency response is from 35-250Htz at best.
 

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Discussion Starter · #3 ·
First of all welcome to the Shack,
The mic you are using do you have a calibration file loaded for it? Otherwise the readings won't be very reliable. The Bose " sub" is not really a sub at all because it barley goes deep enough to handel the sub frequencies. It's better called a bass bin as it's frequency response is from 35-250Htz at best.
mic is not calibrated but when you read 20db of difference in 15hz you can bet the problem is not the mic :)
this graph is not reliable but I think it describes the behaviour of the box in a clear way.
I agree bose sub is not a sub and is a very bad audio thing, is too weird to listen at it even for "iphone trained ears".
Personally I prefer bookshelf loudspeaker with a 120hz rolloff than using a box like that but AM5 has a so high crossover point that I cannot get rid of the "sub" :(
 

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That graph looks more like the room you're in is the issue more than the AM module. Try taking your measurements from a few other positions in the room to verify. A 20db swing like that would be clearly audible in a sweep test. It would sound choppy.
 

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Discussion Starter · #5 ·
That graph looks more like the room you're in is the issue more than the AM module. Try taking your measurements from a few other positions in the room to verify. A 20db swing like that would be clearly audible in a sweep test. It would sound choppy.
Despite mi effort in changin sub position (not a lot of new positions available right now) I get similar behaviour
the phase is something terrible, shifting 180° every peak.

peak at 38Hz changes up to 12db
peak at 48Hz 4db
peak at 60Hz 10db

what isinteresting is that there is no position that damp all the peaks.
what I wish to do is carry the sub outside in the grass with the mic really close and makethe measure at low volume, this will solve the question forever. Anyway I have no time for that actually :(
 

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if you want to see what the sub can really do place it outside and the mic 3 feet away from it and measure and then you will have a bit better idea what the sub is doing without the coloration of the room messing up your readings.

However a lot of cheep mics may have a huge dip below say 30hz the cheep one I used to try and use before replacement fell off starting at 35hz by more then 20db just to give you a idea of some of the stuff that can be going on.
 

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Discussion Starter · #7 ·
if you want to see what the sub can really do place it outside and the mic 3 feet away from it and measure and then you will have a bit better idea what the sub is doing without the coloration of the room messing up your readings.

However a lot of cheep mics may have a huge dip below say 30hz the cheep one I used to try and use before replacement fell off starting at 35hz by more then 20db just to give you a idea of some of the stuff that can be going on.
I agree with you, I just miss the time to do that.
my cheapest mic (creative) has a very bad peak at 50hz, I guess it senses the powerline but really I can't understand how (the micinside the pc does not.

Nobodywith a bose "sub" here? it would be interestingto see some graph
 
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