my first spl...need help

[kaos]

im entering my first db drag race this weekend... i dont expect to win but im just curious as to what i will hit.. i own a 92 ford t-bird, im using 2 kicker comp 12" for power im using 2 sony xm2751 amps each bridged in mono ( 1 for each sub? i have also removed the back seat so more sound can get through... anyways my questions are what do u think i will hit? what cd should i use?
etc.. any help would be much appreciated!

[kaos]

sorry forgot, the amps put out 200 rms each when in mono

[audionutz]

kaos, to be successful at dB Drags, there are several things you must do (if you want me to list them, tell me) . Since were not talking about going after Alma's records, leaving the box in the trunk is fine-removing the rear seat even better! I've metered many SPL vehicles in my day, and my best guess would be @ 138dB on LinearX, 140dB on Audio Control. This is assuming the mic is ON THE DASH per dB Drag Racing rules. Please note that these numbers are TOTAL GUESSES---you must meter for yourself as all vehicles are different. Since you do not know your vehicle's resonant frequency (very important in SPL) I suggest you play music that exhibits a wide range of bass tones so that your car's "sweet spot" will undoubtedly be played (are you familiar with "Pure Silicon" on the official USAC SPL cd?) . GOOD LUCK! And a word from the wise-SPL will prove to be VERY addictive-so be prepared....

[kaos]

yeah, it would be real helpfull if u could list all the important things

[audionutz]

OK here's the list.....It's a very crude list, as there is always room for improvement.

To compete SUCCESSFULLY in DB DRAGRACING, you need;
1)the woofers as close to the rear of the front door openings as possible
2)a SEALED front cabin ,so no air "leaks out" that means NO A/C vents,NOTHING!
3)Woofers with a very high Xmax (excursion measurement) so they will "move" a lot
4)woofers with stiff cones
5)lots of amplifier power (as much as the speakers will take to EACH one!)
6)lots of reserve battery power to supply the amplifiers with the juice they need
7)upgraded alternator(s) to keep the positive voltage as high as possible, thus making the batteries very happy
8)there should be NO air leaks to the rear of the cabin (the "wall o' subs" needs to be sealed up tight)
9)The front cabin should be made as small as possible, which makes for more pressure/square inch (which is what SPL actually is)
10)The enclosure should be incredibly stiff so the speaker baffle doesnt flex.
11)the cabin should be reinforced so that it doesnt flex (roof braces,plexi windshields,concrete-filled doors,solid wood floors,etc.)
12)the resonant frequency of the vehicle must be determined with an RTA and the enclosure should be "tuned" to realize maximum output at the resonant frequency
13)this list could go on indefinitely---- i suggest you go to the DB drags and look closely at what the winners have done to their vehicles. Seeing is believing...Good Luck!

[Dr. Boom]

I have a TBird also, and they can be real tough. Good luck!

[kaos]

well just got back, went to wire the 2nd amo in this morning anf the power wire broke so we had to run a new one through right before the start... so i only used 1 amp bridged to mono subs in parrallel.. any way i hit 137.1 placed 8 of 12.. not too bad for a first try and a set of 5 yr old kicker comps.. it think ima go buy rockford dvc 12's and see what happens... i can see how addicting it is now though.

[audionutz]

Good job,kaos!

[kaos]

now im actually think about getting a new set of kicker.. that means i need to get a new box, now what is bracing, is it important... iwould like to make the box myself

[TepEvan]

137.1 running 2 12" comps of of 200watts? will wonders never cease

[kaos]

TepEvan:
A little skeptical are we?, if u want i would be more then happy to provide you with the hosts email address so u can verify my claim...
just let me know

[audionutz]

kaos, bracing is important so your boxes walls do not flex. Normally, if the box is small (like 2 woofers) and youve built it with 3/4" MDF, then it should be stiff enough. When you go to more than 2 subs, the walls of the enclosure become increasingly long/wide and need internal bracing. The best sub-bass originates from a SOLID box!
Braces can be any shape or size. I generally cut 4"wide strips of the 3/4 MDF to use as braces in small to medium enclosures (4" so the screws dont split the wood on the end!).
In large SPL enclosures, I use 2 by 4's as braces as well as an internal "frame" for the enclosure (think of it as a box-skeleton) because extreme SPL pressure can flex just about anything if un-addressed, and flexin' in SPL is BAD!!!

[alaska]

Glad to hear you enjoyed your first competition kaos. I'm getting ready to compete in my first one in a couple weeks, USAC sanctioned, triple-point event, outlaw SPL. I have an 89 Toyota Corolla with three 12" Planet Audio subs in a sealed box running a little over 300 watts to each (Kicker ZR240). I doubt i'll place very high but I just want to get it measured. Your Thunderbird is a tad bigger than my car http://www.caraudioforum.com/smile.gif and you hit a 137 so I'm hoping to do at least that. My question is does anyone know where I can get a copy of the rules for USAC's outlaw SPL online? Any info greatly appreciated. Thanks!

[alaska]

Oh, one more question...does it make a difference which way i fire my subs, is there a difference in the SPL levels? I have them firing toward the taillights right now and it hits hard enough to blur lettering on signs. Will the SPL be the same if i turn them around and fire into the cabin (back seat removed at all times of course)?

[kaos]

from what i understand each car varies as far as the difference of which way u fire your subs... also there are rules at www.termpro.com/dbdrag (http://www.termpro.com/dbdrag)

[IXLNXTC]

If your subs are in a box that you can move around....I would reccomed facing the subs towards the rear of the trunk. Also move it as close as you can to the rear.
For a explaination of why go to this page!!!
http://www.installer.com/tech/aiming.html

[dBDragQueen]

The rules for outlaw SPL are not on termpro.com..that is only dB Drag. As far as the rules for outlaw SPL I don't think that you can find them online. The basic rules are that the mic can go anywhere in front of the door jams 4 inches from every surface, and it cannot go into a port. One of the most common places for mic placement in Outlaw SPL is in the passenger side kick panel.

1999 USAC World Finals Outlaw 1001+ Consumer World Champion 166.1
1999 USAC World Finals Outlaw Extreme 1001+ Consumer World Champion 170.5

[jalovett]

i have 2 kicker compvr 12's running off a sony xplod 100x2.. i hit a 139.8.. I will be installing a 1.5 farad cap tomorrow.. i hope that will help a little..o yea by the way, i traded my rockford's in for the kickers..and i don't regret it a bit....

[db xtc]

if you want spl get the kicker xpl's. they are much better than the comps. i have four xpl 12's and hit 148.1db with subs in trunk. i am in the plans of building a wall with 8 12's just to make it go boom http://www.caraudioforum.com/smile.gif