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Room Volume and Bass Speaker Size
Room Volume and Bass Speaker Size
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Old 9th January 2019, 05:16 PM   #1
Veeren is offline Veeren  Portugal
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Default Room Volume and Bass Speaker Size

Dear all,

Why is it that my present room of 3m20 X 3m10 with sloping ceiling from 2m8 to3m40 seems to overload with two 8inch bass drivers in BR boxes
A room I had before that was 2m50 X 4m50 X 2m25 had two 12inch driver speakers (sealed boxes) in it without this ear pressure happening.

To move air at 50hz to a certain spl say 85db with the 8inch driver or 6.5inch must require moving the same amount of air as that of a 12inch driver to reach the same spl only moving less.

Also how can this "pressure" actually happen as there is pressure and suction both happening at low frequency not air being pushed out of the room.

Why would a larger driver produce more or less pressure on the ears for the same spl at the same frequency?

Can someone please explain?
Best regards, Veeren
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Old 9th January 2019, 05:19 PM   #2
jazbo8 is offline jazbo8
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Room Volume and Bass Speaker Size
See Bass driver vs room size
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Old 10th January 2019, 10:29 AM   #3
Veeren is offline Veeren  Portugal
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Default Room Volume and Bass Speaker Size

Thank you jazbo8,

I have started to read the thread but I read also conflicts, many say the bigger woofer the better but there is also a chart that indicates a about 4-6 inch woofer for my room volume.

This is no answer to my question.

Regards,Veeren
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Old 10th January 2019, 11:35 PM   #4
Bicicletta is offline Bicicletta
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Hi, comparing different systems in different rooms is a mess... It is not clear to me what you mean by "pressure". The speakers reproduce a frequency modulated signal in a resonant cavity, the room. At certain frequencies the resonance can be impressive: air, walls, furniture, windows, everything vibrate strongly . You can try a sweep to identify critical frequencies, also by comparing with a simulation:

AMROC-Room Mode Calculator

Is that the pressure you hear? Your room is outside the "Bolt area", and does not meet "Bonello's criterium". The sloping ceiling does not help, due to a kind of horn effect, and because an axial way is undefined, increasing the distance between the others. Perhaps you have brick walls covered with plaster... and improbable events happen all the time: does the Fb of a overextended BR match a mode?

Quote:
Originally Posted by Veeren View Post

To move air at 50hz to a certain spl say 85db with the 8inch driver or 6.5inch must require moving the same amount of air as that of a 12inch driver to reach the same spl only moving less.
This is not true, the larger cone is more efficient, see "acoustic impedance".

Quote:
Originally Posted by Veeren View Post

Also how can this "pressure" actually happen as there is pressure and suction both happening at low frequency not air being pushed out of the room.
If you use the wave model, you have pressure without changing the amount of air in the room.

Quote:
Originally Posted by Veeren View Post

Why would a larger driver produce more or less pressure on the ears for the same spl at the same frequency?
spl is for sound Pressure level, so the question seems an oxymoron. If you agree, I would rewrite it like this: "Why would a larger driver excite the resonant cavity differently, for the same sensitivity at the same frequency?
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Old 11th January 2019, 10:47 AM   #5
Veeren is offline Veeren  Portugal
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Thank you Bicicletta !

The "pressure"I was referring to is I think a temporary ear problem similar to ear blockage in a airplane due to a change in air pressure, it is not always the case fortunately.

Yes the room is outside of the "Bolt area" moving one wall for about a meter would just bring it inside the "Bolt area".

Walls are single ceramic brick with plaster covering.

I do get that the larger driver is more efficient so other than needing less power to move air why would this make any difference compared to a smaller driver? I will look up acoustic impedance...

A other thought I had was to tune the room by porting it to a other room using tuned tubes.

I agree, it should be: "Why would a larger driver excite the resonant cavity differently, for the same sensitivity at the same frequency?

Best regards,
Veeren
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Old 12th January 2019, 05:44 PM   #6
drewan is offline drewan  United Kingdom
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My room is as near the same size, but with a level ceiling. All BR speakers sound dreadful in here. Firstly try blocking the ports, stuffing with socks is what I do
Secondly I have 1m sqare panels of 10 kg mass loaded vinyl (MLV) behind the speakers. these pretty much killed the room modes esp 50-60Hz which your (and mine) suffer from. and not the last thing was a panel of thick wool carpet underlay about 750mm wide behind my chair. The wall finish in portugal is much harder than here so you will probably have to do more. I am doing more but it is still work in progress.
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Old 14th January 2019, 12:54 PM   #7
Bicicletta is offline Bicicletta
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You can chew a gum for that. And I do not think that tune the rooms is a good idea: someone here wrote that tune is enemy of fidelity.
I do not know the answer to the question, and two speakers that differ only in diameter do not exist.
Above the modal region, I can do a Gedankenexperiment, idealizing a speaker as big as the wall, another point-like, and no loss.
I have not found an applet to represent this. I'm sorry ...
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Old 14th January 2019, 01:18 PM   #8
Veeren is offline Veeren  Portugal
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Thank you Bicicletta,

thank you drewan for your answers and suggestions. I will look into the mass loaded vinyl panels.

At one point I will experiment with two 12 inch loudspeakers on baffles mounted in the corners using the corner walls as the speaker cabinet.

Best regards,
Veeren

Last edited by Veeren; 14th January 2019 at 01:20 PM.
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Old 14th January 2019, 02:03 PM   #9
Bicicletta is offline Bicicletta
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I've just mounted two subs in the corners. Their primary function is to regularize medium-low. So they are stereo, filtered at 150 Hz, and I changed the name into bass-units, just a little far from the midrange. They produce a deep narrow dip at the listening point, with which we will live together. If you use subs as subs, you can leave a degree of freedom on their position, to get more regularity on the bass. If you mean "baffle" as "open-baffle", please stop!
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Old 14th January 2019, 05:32 PM   #10
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by Veeren View Post
The "pressure"I was referring to is I think a temporary ear problem similar to ear blockage in a airplane due to a change in air pressure, it is not always the case fortunately.
Is your listening position near a wall?
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