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Post by SupaStealth on Sept 19, 2004 1:44:44 GMT -6
Well, i found out that next weekend there is a sound competition near by. My neighbor builds subwoofer boxes and he said he'd build a custom snailshell box (similar to the type of box used in bose subwoofers) then i'll get to do the SQL and the SPL, also i'll be able to test the quarter mile which is kind of the main reason i'm going, so i'll be sure to take lots of pictures and info. oh, for anyone in the area, this competition is around the Racine, Wisconsin area i believe.
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scottydl
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Post by scottydl on Sept 21, 2004 9:45:33 GMT -6
Sounds fun! Those events are quite enjoyable if you've got the time & money... neither if which I have anymore.   But it's always a good time to see others' cars and what they have done to them... although you'll find that some people take these gatherings a little *too* seriously. Looking forward to the pics! |
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Post by omegaic on Sept 21, 2004 9:51:35 GMT -6
Everyone needs a hobby!
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Post by R4D30N on Sept 22, 2004 11:16:41 GMT -6
what class will you be competing in?
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Post by SupaStealth on Sept 22, 2004 16:04:24 GMT -6
amatuer, AS2, i'm about right in the middle of the class with 613.1 points
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Post by R4D30N on Sept 22, 2004 20:24:20 GMT -6
what rating sytem is being run there? and what are you competing for SQ or SPL?
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Post by SupaStealth on Sept 23, 2004 6:53:25 GMT -6
Well, i got some bad news, i just learned that they upped the entrance fees to 50 dollars so my friend and I cant afford to b both running in the competition since i have to cover his entrance fee since he is building me a box, (that and i still need to buy some 2/0 wire and connectors) so i'll just be a spectator  . the 50 dollars covers the SQ and SPL and quarter mile run. |
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Post by SupaStealth on Sept 25, 2004 22:21:52 GMT -6
well, i worked out a deal with my buddy, i had an extra amp layin' around so i just gave him that and now i'm able to afford it, woohoo. i unofficially did the quarter mile at 98 mph and an unknown time yesterday with a hot engine. so i'm goina bring somethin' to cool down that pipe before i take my run cause that intake pipe heats up to at least 140 degrees F. i should be posting pics late sunday or sometime on monday.
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Post by SupaStealth on Sept 26, 2004 22:53:30 GMT -6
Well, we had a few issues with my subs so i couldn't run a tone at the competition and i had to use a song for the sql, i got a 138.0db, and then worked out the problem by the time the reality section (where they put the meter where the driver would be sitting) was up and did a 137.1 db, and a drive-by at 117.8db. and the new term lab meter which is harder than all the other meters to score high (usually about 3-4 db lower than others)
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Post by omegaic on Sept 26, 2004 22:57:09 GMT -6
How does that compare with the stock bose system? Did some research, check this out. science.howstuffworks.com/question124.htmApparently your stereo system produces sound equivalent to a gunshot or jet engine, or 1,000 times louder than a lawnmower. That's incredible considering more than 85dB can damage hearing. 138dB is 100,000 times louder than 85dB. Isn't a logarithmic scale great? |
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Post by kobalt on Sept 27, 2004 9:18:08 GMT -6
LOL! Wouldn't that blow out windows/eardrums at close range?
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scottydl
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Post by scottydl on Sept 27, 2004 9:32:45 GMT -6
138dB is 100,000 times louder than 85dB. I'm not sure I understand this. I seem to remember the figure that is takes 10x the source to double audible sound levels... so if 1 chainsaw equals 100db, it would take 9 more before the sound level is actually "twice as loud". This would seem to indicate that 138db is not even 2x as loud as 85db.  |
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Post by omegaic on Sept 27, 2004 9:41:35 GMT -6
From the link: On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB.
40dB = 10,000 times more powerful than 0
80dB = 100,000,000 times more powerful than 0
130db = 10,000,000,000,000 times more powerful than 0
130db = 100,000 times more powerful than 80db. At least as far as I can tell.
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scottydl
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Post by scottydl on Sept 27, 2004 9:57:08 GMT -6
Something still seems strange about that logic, although I can completely see how the 100,000 figure came up. I think it depends on your starting point... i.e. going from 80db to 130db would be a much smaller exponential increase than that same point on a scale from 0db to 130db. Maybe? Oh well, that's why I didn't keep my Math major in college.  |
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Post by omegaic on Sept 27, 2004 10:04:37 GMT -6
We can always test this theory. Just sit in your car for 8 hours with your stereo up at 130dB and see if your hearing is affected. That should be quite conclusive |
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Post by Letitroll98 on Sept 27, 2004 14:46:00 GMT -6
Yes Scotty, you have it sort of reversed. The doubling for 3db is the output power of an amp needed to get to a 3db increase in power response at the output terminals. (Power can be measured in db) This is related to sound pressure levels only indirectly as you have to apply all the modifying factors of the speakers such as inductance, reactance, free air resonence, enclosure size, speaker efficiency, etc.
Measuring actual sound pressure levels comes from the reverse side of these equations. Therefore a 3db increase in measured sound pressure level is a doubling of apparent noise levels.
Supastealth, you seem like a great guy. Very respectful in all your posts and such. So with no disrespect meant, please don't drive in my neighborhood. Unless you're playing "Celtic Moods" of course. Best of luck with the hearing aid.
Signed,
NIMBY
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scottydl
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Post by scottydl on Sept 27, 2004 15:35:49 GMT -6
So with no disrespect meant, please don't drive in my neighborhood. Unless you're playing "Celtic Moods" of course. Then at least you can be very relaxed as you go deaf. ;D |
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Post by R4D30N on Sept 27, 2004 23:32:17 GMT -6
Supa I honestly don't beleive that, but for these reasons:
When testing SPL, you need to build up pressure in the cabin of your vehicle, which, with a "drive-by" of 117, there must be alot of pressure in the earth.
Your sound quality isnt rated in decibels. They take the cleanliness of your install and start a base point system, then they increment volume and give points for dB with or without distortion.
103 dB is 2x louder then 100 dB
I like how you used the information I told you about termlab here.
and my 2 10's hit 143.3 on a termlab. and a 146 on a B&W
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Post by R4D30N on Sept 27, 2004 23:39:27 GMT -6
LOL! Wouldn't that blow out windows/eardrums at close range? No. SPL over 160 dB can shatter glass, metal floors, and physically move hair. 160 dB is instant perforation of your eardrum. My freind has 3 cerwin vega strokers, and hits 162 dB |
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Post by omegaic on Sept 27, 2004 23:46:34 GMT -6
...just because he can.  |
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Post by R4D30N on Sept 28, 2004 0:02:05 GMT -6
ehh the 160+ kid competes for a hobby.. i just listen to mine
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Post by SupaStealth on Sept 28, 2004 0:07:32 GMT -6
heh, you people are funny, there are a few people that don't believe me so i guess i'll have to scan in the MECA sheet that says all my scores. i supose i might as well scan in my timeslip too.  Edit: i figured I'd post some pictures of my box and subs  This is what a Snailshell box looks like.  This is what my crappy subs look like in this beautiful box. |
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Post by Letitroll98 on Sept 28, 2004 0:54:17 GMT -6
Quote "This is what a Snailshell box looks like if you didn't know."
This is called a modified transmission line and is generaly filled with sound absorbing material to control the waveform. The transmission line's length and shape would be linked with the free air resonance, suspension compliance, and size of the speaker(s) to create a 6th order butterworth filter giving you the lowest and most even frequency response. The "modified" part comes from the fact that to build a true transmission line box for 12-15" speakers like these CVs are you would need a box about 4-5 times bigger than you have there.
Having designed about six or seven home audio speaker systems I'm glad to see some youngsters diving into the field. Best of luck to ya. I SAID BEST OF LUCK TO YA.
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Post by SupaStealth on Sept 28, 2004 7:45:10 GMT -6
Thanks for elaborating, i'm still really new with the whole audio competition stuff, this is about only my friends fourth "snailshell" box so we're still learning about getting the proper dimensions of the box while still making the box be able to fit in a trunk. We were actually having problems with my subs with this box, when we played a tone past a certain volume, the subs would oscilate from the max in position to the max out position rapidly. But we notice that on a song they would stay in control. So i had to use a song for bass during the competition.
at the end of the first horn we have a tuning board so we can adjust the airflow through there (its not on it in the picture) which allowed us to control the subs a little bit but not enough. it would probably work with a different pair though, since these subs are gettin' a little old.
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Post by Letitroll98 on Sept 28, 2004 14:53:00 GMT -6
Try these links: www.t-linespeakers.org/www.diysubwoofers.org/tls/And for good general speaker building info, not related to transmission lines: speakerbuilder.net/Hope this helps. Oh, I almost forgot, Quote: "We were actually having problems with my subs with this box, when we played a tone past a certain volume, the subs would oscilate from the max in position to the max out position rapidly." This is a direct consequense of an improperly designed speaker. You are inputting a signal frequency below the resonent frequency of the speaker. (By "speaker" in this instance I mean the whole box/driver combination) This results in the osillation you are observing. When you input a music signal it never drops below about 42hz, the lowest frequency of a bass guitar, ergo no osillation. A little design theory will go a long way here. You're not looking for perfectly flat frequency response, just max SPL. If you keep going with trial and error, you could build literaly thousands of designs b4 getting it right. With a little research you could actually get to your target. This method of problem solving is the stuff they should have been teaching you in school, not the War of 1812. |
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scottydl
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Post by scottydl on Sept 29, 2004 8:41:19 GMT -6
This method of problem solving is the stuff they should have been teaching you in school, not the War of 1812. That's right! Let's stick to the IMPORTANT stuff, darn it! ;D Me thinks that Letitroll knows his audio stuff. |
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But it's always a good time to see others' cars and what they have done to them... although you'll find that some people take these gatherings a little *too* seriously. 
. the 50 dollars covers the SQ and SPL and quarter mile run.
