General SPL General discussion of Sound Pressure Level topics.

SPL - importance of what's going on inside the box vs. outside

Old 09-02-2010, 10:03 AM
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SPL - importance of what's going on inside the box vs. outside

what is more important in the world of spl?

what is happening inside the box or outside of it?

discuss, but please do not say "both are just as important" cuz that's not a discussion.

i will start off by saying that it is the box, as many things that are outside of it will influence what is happening inside, so it all comes back to the box.

your thoughts?
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Old 09-02-2010, 11:14 AM
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I would have to say the box as well. I've built plenty of boxes over the past 3 years and have used at least 4 vehicles for spl. Each car has peaked at a different frequency. I think that once the box is built to the resonance frequency of the vehicle then it will get as loud as loud can possibly be. For this reason only is why one would deaden a vehicle first before one builds the box.
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Old 09-02-2010, 11:22 AM
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I've recently learned that where the box/port is has a lot to do with how the subs react.

When I first tested my new enclosure, I "thought" because I had a 12" flared port, I should place it about 6"-7" from the back door. 1/2 the port size. Well.... the subs did some funky compression thingy and started to only move half way at higher volumes and wouldn't get any "louder". After moving it forward and back I seems that I only needed 4" of space and that strange "compression" effect went away.

Also, when I open the rear hatch, it takes little power to make full excursion. This is how many people blow subs. Showing off with the hatch/trunk open, when the system is designed around it being a loading wall.

Last edited by DeadlySones; 09-02-2010 at 02:34 PM.
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Old 09-02-2010, 12:04 PM
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I say inside box, if the circulating air is not co operating. Then you will not get nearly as loud as say a box that has been resined and 45s in corners, or for the aeroport guys just resined
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Old 09-02-2010, 12:22 PM
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about the outside, the wavelength and the peak of the wave should be where the mic is no?



let say the burp at 55Hz, the 1/4 of the wavelength (peak) will be around 5 feet, so i guess that if the speaker at 5 feet from the mic it will have better result than 7 feet unless there's some phase shifting... make sense ?
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Old 09-02-2010, 12:37 PM
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Originally Posted by DeadlySones View Post
I've recently learned that were the box/port is has a lot to do with how the subs react.
ahhhhhhhhhh tell us more
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Old 09-02-2010, 01:03 PM
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in street, the vehicle you work with can only be altered by sound deadening, so the obvious answer would be to look at the enclosure. this volume and overall shape of the enclosure will change depending where in the vehicle its located. The performance will also change too.
In a crx, you would do best to have cone pressure at the b-pillar (mid 60hz) but loading port pressure at the hatch(high 40hz) brings your burping freq down to where the car(mid 50hz) peaks its spl.

Something ive thought about is big walls using say, 4x 18" in an astro....they always build to the b-pillar which should tune around 64-66hz but to achieve even cone pressure and max spl, they should build away from the b-pillar where the wall actually wants to peak.

im sure ive got more but i just woke up lol
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Old 09-02-2010, 02:13 PM
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Originally Posted by bart pyle View Post
in street, the vehicle you work with can only be altered by sound deadening, so the obvious answer would be to look at the enclosure. this volume and overall shape of the enclosure will change depending where in the vehicle its located. The performance will also change too.
In a crx, you would do best to have cone pressure at the b-pillar (mid 60hz) but loading port pressure at the hatch(high 40hz) brings your burping freq down to where the car(mid 50hz) peaks its spl.

Something ive thought about is big walls using say, 4x 18" in an astro....they always build to the b-pillar which should tune around 64-66hz but to achieve even cone pressure and max spl, they should build away from the b-pillar where the wall actually wants to peak.

im sure ive got more but i just woke up lol
very good point about the wall being after the pillar
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Old 09-02-2010, 02:32 PM
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Originally Posted by Father Yuli View Post
ahhhhhhhhhh tell us more
Added it to the original post.

I should have quite a bit to add to this over the next few weeks, lol. Seeing as the SPL design for regionals will be starting soon, and I've got A LOT to try and learn. We have all the tools we need now to test for power, rise, DB's, the works, so should be good. Our team is going to learn lots over the next few weeks.

Looking forward to Ontario Regional Finals, Sept. 26th!!!

Last edited by DeadlySones; 09-02-2010 at 02:38 PM.
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Old 09-02-2010, 03:25 PM
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Paul you need more power man, your score would sky rocket i think.
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