What kind of SPL could I expect from this system?

[RSDXzec 10+ year member]

I don't have an SPL meter nor can I buy one that measures over 130db, and I'm fairly certain I'm over that. The system consists of 3 12"s in 1.85cf chambers after displacements tuned to 31.5hz. The amp feeds it 1000wrms wired at 1.34 ohms. My car is a hatchback and the subs are facing towards the rear.

I know there's a lot of variables involved and guessing over the internet isn't really accurate at all but I'd like some idea of the decibel "range" I should expect to be in with something like this (eg 30's, 40's etc) from the more experienced users here who have heard multiple setups. The loudest system I've ever heard is my own so I really can't judge here, and I get an estimate on winisd but that doesn't factor in things like cabin gain. So far I'm only pushing 500watts to it until I upgrade my electrical and it's already began making my ears hurt a fair bit, but i'd like to know what to expect at the full 1000watts rms.

The box I built looks like this

and I designed it to have this shape in accordance to the shape of the back of the car to try and get a "horn effect" going.

Again I'm not asking for a .01db accuracy because that'd be stupid without actually hearing the system, just if it were your build in progress would you expect it to be in the high 30's or low 40's etc.

Cheers.

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[subzero 5,000+ posts]

I would guess around 134 dbs. maybe 136 in the kick, depends on how the tones resonate in your car.

 

[TreyE 10+ year member]

i guess 140-142

Are you going to get it metered after you build it? Im curious to know who gets closer

 

[RSDXzec 10+ year member]

I would guess around 134 dbs. maybe 136 in the kick, depends on how the tones resonate in your car.

seems reasonable I guess, would've liked to be closer to 140, the subs are soundstream PCW-12's if it makes any difference, I figured surface area and power were the main indicators (3 12"s on 1000wrms).

winisd predicts a peak of 124.5db at 54hz and what i've read on the net suggests cabin gain is generally around 12db, don't know if that "horn effect" I designed for helps there. I think the cabin is about 80-90cf and from doing (speed of sound)/(2*longest distance in car) I found the resonant frequency of the cabin to be between 60-65hz.

i guess 140-142
Are you going to get it metered after you build it? Im curious to know who gets closer

I'd like to if I could, but unfortunately I wouldn't be able to measure anything over 130db.

I'm aiming for guesses at the dash or "termlab legal"

 

[TreyE 10+ year member]

thats what i was guessing....hmmm might be lower than my guess with that low tuning

Why are you tuning so low?

 

[RSDXzec 10+ year member]

thats what i was guessing....hmmm might be lower than my guess with that low tuning

Why are you tuning so low?

well i don't go to any competitions as there aren't any in my area, so this box was made for music and I just can't get enough of the lows. For reference my last box was tuned to 25hz. This box seeing as I had to fit 3 subs in the trunk instead of 1, I had less room for each so I had to go a little higher to compensate, that and I also noticed on my last box I was lacking in the higher notes.

What would you say would be a good estimate over what winisd predicts for a real world measurement? With subzero's guess cabin gain of 12db seemed almost dead on.

I think the best I could to for metering would be to see how many watts it takes to hit 130db, then from there just estimate, eg, if I hit 130 @ 250watts, I should be at 136 @ 1000watts.(3db per double power)

For reference this is what winisd predicts

I was a bit disappointed that I couldn't get a flatter response with the small amount of space I had but I worked with it and tried to get the most sql out of it.

 

[TreyE 10+ year member]

I hated my box tuned to 24hz. Kinda hated my box tuned to 29hz. Loved my box tuned to 34hz.

With the lower tunes I had to play a certain type of music that hit certain notes to have it slam. At the higher hz it seemed to accept a lot more music types bsides like slowed rap songs lol

 

[RangerDangerV2 5,000+ posts]

dont see that design working very well...

 

[RSDXzec 10+ year member]

I hated my box tuned to 24hz. Kinda hated my box tuned to 29hz. Loved my box tuned to 34hz.
With the lower tunes I had to play a certain type of music that hit certain notes to have it slam. At the higher hz it seemed to accept a lot more music types bsides like slowed rap songs lol

I really enjoy frequencies between 25 to 45hz if I can get them loud enough. I wish I could just change tuning whenever I wanted to see the difference but I'm pretty happy with how it turned out.

dont see that design working very well...

Well it's doing great so far, had it in the car close to a week, here's a better picture of what it looks like completed/modelled but I'd have to take a photo of it in the car to give a better idea.

Only been able to give it 400watts rms due to my crap battery, soon enough I'll be getting an AGM deep cycle and pushing 1000watts, I have a wet cell starter battery now, not really made for audio lol.

 

[RangerDangerV2 5,000+ posts]

port is too small and the ratio of length to width should ideally be 1:1 or as close to that as possible...

 

[RSDXzec 10+ year member]

port is too small and the ratio of length to width should ideally be 1:1 or as close to that as possible...

yeah I talked to mobileenclosures about that, the limit for length to width is 8:1 before resonance issues occur and mine was closer to 7:1 so he said it should be fine. As for being too small the wind speed stayed under 25m/s in winisd at all frequencies when only pushing 1000watts. I think it peaked at 23m/s at 23hz.

 

[RangerDangerV2 5,000+ posts]

yeah I talked to mobileenclosures about that, the limit for length to width is 8:1 before resonance issues occur and mine was closer to 7:1 so he said it should be fine. As for being too small the wind speed stayed under 25m/s in winisd at all frequencies when only pushing 1000watts. I think it peaked at 23m/s at 23hz.

winisd is useless unless you are factoring in cabin gain //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

 

[RSDXzec 10+ year member]

winisd is useless unless you are factoring in cabin gain //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

does cabin gain change the port speed somehow? I haven't heard any port noise so far and I know what port noise sounds like (I put one of these subs in a box with a small port which was designed for another sub and it sounded like ***, it sounded a bit leaky and had really bad low end response, the frequencies that generally move more air).

All information on the net I've found said in car audio to definitely stay under 25m/s and I confirmed it with mobileenclosures. For home audio I found 17m/s to be the limit.

 

[RangerDangerV2 5,000+ posts]

does cabin gain change the port speed somehow? I haven't heard any port noise so far and I know what port noise sounds like (Put one of these subs in a box with a small port which was designed for another sub and it sounded like ***).

cabin gain will change almost every graph. I just stay away from winisd.

 

[RSDXzec 10+ year member]

cabin gain will change almost every graph. I just stay away from winisd.

fair enough, I thought cabin gain only changed sound output, not port velocity.

afaik cabin gain increases sound output the most near the cabins resonant frequency (generally around 50-60hz) therefore making the response curve I posted above even more peaked.