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botelerc

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If you like that one , try this one for room gain on subwoofers:

Room gain formula for subwoofer:


C is the speed of sound 1125 or 1130 ft/s


Length of room in ft. is L






C/2*L


1130/2* 20=28.5 Hz so you will start gain 12 db/octave starting at
28.5.. This mean at 14Hz you will be up 12 db. Room gain is not
boundary gain which is usually 2-5 db.


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If you like that one , try this one for room gain on subwoofers:

Room gain formula for subwoofer:

C is the speed of sound 1125 or 1130 ft/s

Length of room in ft. is L

C/2*L

1130/2* 20=28.5 Hz so you will start gain 12 db/octave starting at

28.5.. This mean at 14Hz you will be up 12 db. Room gain is not

boundary gain which is usually 2-5 db.

You lost me. 1130/2*20 is not 28.5 it is 11,300.

I know about cabin gain, but I thought that was effective in pretty small spaces. I have also heard of "pressurizing a room" with a sub which provides gain. I am sorry if I am too big a dope to understand your calculations.

edit: dumb me, you meant 1130 / (2*20) . . . Still, the cabin gain and pressurizing room is something I would like to understand better...

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In the example of the 20 ft long room the room gain was 12 db at 14 Hz. If the room was 10 ft long the 12 db room gain would be at 23 Hz. The shorter room will get another boost at 11.5 Hz of 12 db. This is why subs perform better in smaller rooms. Sealed subs can take advantage of the room gain due to the slow roll off. The Key point: below a certain frequency the room will not support standing waves. When the wave length is greater than the length of the room, you get room pressurization (Pressure Vessel Effect). You get more gain as the frequency decrease since the wave lengths are longer.

Normal room gain is around 9-15 db with an average of 12 db so a sound with a spl of say 70 in an open space at 30 Hz would read 82 db in your room. Subs located in corners can get additional boundry gain of 2-5 db. Room gain starts a 40 Hz and sub will have max spl 40-70 Hz as a general statement.

Mustang, I think you garage is to big to ever effectively pressurize, lol. It is just to long[;)] I am in the same boat since my system is in a room 6,500 + sq ft, he he. I will never feel the pressure that some on the forum feel with smaller room, lol. Maybe I should put this system in the basement.[:|]

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In the example of the 20 ft long room the room gain was 12 db at 14 Hz. If the room was 10 ft long the 12 db room gain would be at 23 Hz. The shorter room will get another boost at 11.5 Hz of 12 db. This is why subs perform better in smaller rooms. Sealed subs can take advantage of the room gain due to the slow roll off. The Key point: below a certain frequency the room will not support standing waves. When the wave length is great that the length of the room, you get room pressurization. You get more gain as the frequency decrease since the wave lengths are longer.

Normal room gain is around 9-15 db with an average of 12 db so a sound with a spl of say 70 in an open space at 30 Hz would read 82 db in your room. Subs located in corners can get additional boundry gain of 2-5 db. Room gain starts a 40 Hz and sub will have max spl 40-70 Hz as a general statement.

Mustang, I think you garage is to big to ever effectively pressurize, lol. It is just to longWink I am in the same boat since my system is in a room 6,500 + sq ft, he he. I will never feel the pressure that some on the forum feel with smaller room, lol. Maybe I should put this system in the basement.Indifferent

6500 sq ft or cubic feet? Cause a 6500 sq ft room would definitely be hard to fill. You'd need about 20 more subs. Lol 80x80 living room. Me and the wife are laughing about how big that room would be. You could have a home theater, tennis court, mini golf, and a go kart track. That's what I would have anyways.
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6500 sq ft or cubic feet? Cause a 6500 sq ft room would definitely be hard to fill. You'd need about 20 more subs. Lol 80x80 living room. Me and the wife are laughing how big that room would be. You could have a home theater, tennis court, mini golf, and a go kart track. That's what I would have anyways.

That is funny, I meant 6,500 + cubic ft. I know some basshead would say I still need at least 2 more subs but, the wife anit having it! At 10 Hz, I can hit 110 db with only the 2 subs with the Radio Shack meter 14 ft. from the sub which is still good for this size room. Those are corrected numbers for the readings but, since you loose 3 db per meter, the 1 meter reading should be around 119 db. at reference level.thanks to room gain and boundry gain. I have both subs corner loaded and driver's facing the wall, he he.[;)]

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That helps. Thank you for eloquently explaining! It also makes sense of a conversation I had with an engineer at Danley Sound Labs regarding this shop. He said one of his fellow engineers had just mounted Danley subs above the congregation in a large church facing down. I expect this was a way to achieve room gain and pressurization in a very large room. As heavy as those speakers are, I'm not sure I would want to sit in one of the Damocles pews. I think 'd take my chances getting struck by lightning or getting hit by a meteor outside.

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People learn the 3 dB for double power rule, but it's the 3 dB increase that is approximately equal to 2x the power whereas 10 dB is exactly 10X.

10 x log(powerRatio) = X dB

10 x log(10) = 10 dB

10 x log(3) = 3.0103 dB

Good information, I wasn't aware of that. Isn't it also true that 6db is the measured twice as loud, whereas 10db is the perceived twice as loud?

3 dB is double the power
6 dB is double the voltage (and 4x the power)
10 dB is said to be perceived as twice as loud.

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