3 db per sub gain rule...

[djman37 5,000+ posts]

okay, that part I get, but does it have to be the SAME sub? make/model?

I'm thinking of mixing RE SE 12 and JL 12w6v1's of all things. Each pair would be in their own ported enclosure, separate chamber, common box thing.

Asking for trouble?

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[80INCHES 5,000+ posts]

yes

80

 

[iagrdshaka 5,000+ posts]

very much so

 

[djman37 5,000+ posts]

i kinda thought so. I'll double up on SE's.

thx

 

[delvryboy 5,000+ posts]

3db is good only in theory 90% of the time //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[GTonDubs 10+ year member]

if you mix 2 different kinda subs even if they are in the same exact box with the same tuning, each sub will perform very differently, you could risk blowing one of them, cause one is gonna like the box better than the other and at that there is always a possibility that they will have noise cancelation

 

[Spkrman]

ure gain per adding subs depends on *alot*... i mean.. a HELL of alot. There is more to factor in than just cone area and power //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

expect closer to 1.5db in most installs... sometimes you LOSE when you add cone.

 

[djman37 5,000+ posts]

gton,

each sub would have it's own recommended box, all of them tuned to the same freq, but I'm ditching the mixing subs idea and just going w/ the RE's.

spkrman,

yeah, sometimes the real world and the ivory tower of theory don't match up.

jmac,

that's the formula i was looking for I've found it on either bcae1 or 12volt I think. Thanks for the refresher!

I'm gonna add two subs and power them differently. Thanks guys for the input. I'm suprised there were no "JL will eat the RE's" or vice versa flaming. Later guys!

 

[Goldtaz1 10+ year member]

Theoretically ...
dB Difference = 20*log(Vd1/Vd2)

Vd = excursion*cone_area

2x Power = excursion*Sqrt(2)

Sub A excurts 10 mm (1 cm) w/ X power and has a cone area of 500 cm^2, making for a Vd = 500 cm^3. Two of sub A w/ X amount of power per sub = 1000 cm^3.

dB difference = 20*log(1000/500) = +6.021 dB

Take the same sub and compare it to two subs but w/ X amount of power split between the subs (X/2 power per sub). Excursion of each sub = 0.707 cm. 0.707*(500+500) = 707.107.

dB difference = 20*log(707.107/500) = +3.01 dB

Of course, this doesn't account for cancellation ...

I swear, how could anyone not love this guy?!?!?!?!? That's the kind of explanation I like to receive when I ask questions.

 

[audioholic 5,000+ posts]

...but I'm ditching the mixing subs idea and just going w/ the RE's...I'm gonna add two subs and power them differently...

What? You seem to have contradicted yourself there. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif What are you doing again?

 

[djman37 5,000+ posts]

I was going to pick up a pair of JL12W6v1's and make a box for them tuned to the same freq the RE's were already tuned to. Now I'm NOT gonna take on the JL's just get 2 more SE's

 

[HeatSeeker 10+ year member]

Theoretically ...
dB Difference = 20*log(Vd1/Vd2)

Vd = excursion*cone_area

2x Power = excursion*Sqrt(2)

Sub A excurts 10 mm (1 cm) w/ X power and has a cone area of 500 cm^2, making for a Vd = 500 cm^3. Two of sub A w/ X amount of power per sub = 1000 cm^3.

dB difference = 20*log(1000/500) = +6.021 dB

Take the same sub and compare it to two subs but w/ X amount of power split between the subs (X/2 power per sub). Excursion of each sub = 0.707 cm. 0.707*(500+500) = 707.107.

dB difference = 20*log(707.107/500) = +3.01 dB

Of course, this doesn't account for cancellation ...

Well ****, I always thought adding one sub with the same amount of power would increase 3 db. Glad to see I was wrong //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif Learn somethin new every day...

 

[InhumanAcura 5,000+ posts]

going from 2 LI 12"s to 4 LI 12"s we lost ~1db in like 3 different boxes off a vr1000....lack of power for the 4

 

[audioholic 5,000+ posts]

I was going to pick up a pair of JL12W6v1's and make a box for them tuned to the same freq the RE's were already tuned to. Now I'm NOT gonna take on the JL's just get 2 more SE's

Yes but my concern now is how do you plan to power these three subs. Your earlier comment suggests you will be powering the two new subs seperate to the original third sub, which most times is a bad idea. All three subs should receive the same power (yes, even if in individual chambers), so you're gonna have to match outputs via gain adjustments and a DMM. You are MUCH better off just getting one amp to power all three.

 

[Spkrman]

Of course, this doesn't account for cancellation ...

Or more importantly... when you introduce another box *alone* you will typically get a loss just from blocking air getting to the front. This is most apparant in trunks.

Cancellation is also a big issue.... and nearly impossible to get around.