help with audio entry

help with audio entry

whats the main difference between

P320 Sonic Boom - USAC SPL Power - Stock 901-1800 watts

P360 Sonic Boom - USAC SPL Power - Super Stock 901-1800 watt

P420 Sonic Boom - USAC SPL Power - Modified 901-1800 watts


what would mine fall under? And do you think I would have a chance?

I will have a 13w7, and a 1000/1

Check out this page - USACi homepage:
http://www.soundoff.org/rules.htm

Has all the rules and sample scoring ballots - so you know what they are looking for and minimize your deductions.

JL 13W7 - hard to say. Decent sub - with a good box and stout amp, maybe 110-130dB SPL. I think the link list the most recent winners - they been hitting 150dB+ SPL. Anything is possible - if you don't try, you'll never know.

ok it says smaller than 12" but larger than 15", WTF I have a 13". They did help but now I am more confused than worried.

You would sit in the 15" sub class. Usually guys that run 50+ dB SPL have a chance at this class level. To place in the World level - you have be running in the 150s+ dB SPL.

so in order to do the 15: sub class, i need to be making 150s+ db? :superconf I am just getting into this, what the difference between the class level andworld level other than the amount of db's, like qualifications

Sorry, what I meant was to be competitive - you would need to at least make 50dB SPL. Should be no problem with that sub, amp, and halfway thought of enclosure.

To be actually place (award level) - you would have to make sure that your system can push even more (150dB+ SPL based off of number from previous winners). The World level just means that if you want to win at something like the World Finals - 150dB+ is what you should be looking for.

Didn't mean to say that if you don't make 150dB+ - you won't win. Depends on who else is running in your class at the competition. You could walk into a competition that has guys running 60-70dB SPL max.

The guys that I see running a similar setup to yours (they usually run JL 13w7 with a 1000.1 amp on each coil) can get it to 120dB - 150dB. Quick test - if you can make your wiper blades bounce at least an 1" (of course it depends on how strong the springs are) - probably right at the 120dB - 150dB range.

thanks man, I appreciate your information a lot. I dont know about world competitoins, but I was looking into NOPI nationals, is that world? Also i havent the terminology "1000.1 amp to each coil"? what do you mean by coil? I assume you mean 1 amp to each sub, if thats not the case can you explain it to me, thanks.

I dont know what my set-up will make, everything should be in next week. I am going to measure how wide and tall i can make it, and then match the depth of the box to what the square footage (air mass) jl recommends for a sealed box. thanks again

I would consider NOPI worldwide - or at least internationally reaching. That's how we get the cool stuff over here.

What I mean by 1000.1 amp driving each coil:
- 1000.1 or written as 1000/1 (same thing - single channel, 1000W amp)
- feeding each coil, the JL 13W7 is a dual voice coil sub (DVC). You can wire the sub's voice coils to be in parallel (drops impedance by factor of two ~0.75 ohms), series (doubles the impedance ~3 ohms), or wire them up separately ~1.5 ohms each. Basically - these guys wire two amps to each DVC sub, one for each voice coil. If the sub can take the power and the amps can keep up with the juice = lots of BOOM BOOM.

Sealed box would be a good choice - strong bass with control (doesn't get too muddy) - also the smallest enclosed volume, a plus when you already tight on space.

Let us know what you think when you get it - from what I've seen capable from that sub, would be one of the hardest hitting MoFo, out there. I prefer the SQ of the w6 line, but the w7 is definitely a competition level sub.

wow so it is only 1.5 ohms if you wire them up indepentely to 2 different subs, thats really pricing and dnagerous, I will stick to one amp hahaha. I heard this sub once in a lexus, same set-up, but the guy had a huge sealed box. When he turned it on he closed his trunk too. I dont understand why he closed it, but I thought the bigger the box or what is specified, the better?

Yeah - that's pretty low. If that amp in not low impedance stable - you'll end up with a paperweight real fast (don't worry - it can take it).

A box can be too big or too small - has to be tuned to a certain "sweet spot" frequency. Otherwise it will sound like ass. Reason why some people say larger is better is because you have decreased the chance of have destructive interfence from happening and damping your sound (incident and or reflected way is absorbed into the surrounding area or low enough to not cause too much of a problem).

Most guys run the box with the woofer back toward the bumper, close to the trunk lid (towards the license plate). Reason - low frequency wavelengths are extremely long, and by facing your subwoofer toward the rear, close to the trunk lid, you can get a much better response (no or littledestructive interference). This means that the incident and reflected waves (think sound waves propogating out of the sub and bounced back by the trunk lid) are very close to being in phase, reinforcing the sound. Closing the trunk just helps control the wavefront - differences can be sustantial. All classical physics here - standing waves and harmonics. That's why at some sound competition somewhere - a guy with a 2.5 or 3 cu.ft sealed box with a single 10" sub, and two amps - will blow away guys with 10x the power and numbers of speakers.

wow, I did not know all of that. GOOD TO KNOW!!!! I was going to face the front of the speaker toward the rear only because I am keeping my spare dont I am not giving up the spare tire for the sub. You were talking about frequency's, do you tune it via your amp right? If not where, any special tools required.

True, your amp will have an onboard crossover - fully variable, selectable slope low pass filter - but cannot be used to "tune" the box in that way. The frequency is set by the design of the enclosure for the subwoofer. You should get soem example dimensions for the sub or you can calculate the numbers from spec sheet that should come with them. Should include info on driver free-air resonance, mechanical compliance of the driver, effective area of the driver, maximum cone excursion, impedence, etc.

Example: - pretty standard notation here
To determine the box size for a sealed enclosure system, you will need to know the following parameters for the driver (printed on a spec sheet that is in with the sub

Vas = Equivalent air compliance (L)
Qts = total Q of the driver at Fs
Fs = resonance frequency of the driver (Hz)

Choose a final Qtc (total Q of system at resonant frequency) for your particular design. Good starting values for Qtc are from 0.6 to 1.0. Sound quality vs power - transient response degrades with higher Qtc values, but the power handling of the system increases. A Qtc of 0.7 will usually give pretty good results, but you can use a higher figure if the subwoofer has a lower resonant frequency (ie < 20Hz) or if it's being designed for car use.

So know what (Sorry - can't make the math look pretty with just plain text

Qr = Qtc/Qts
Vr = Qr^2-1
Vb = Vas/Vr
Fb = Qr*Fs
F3 = Fb*((1/Qtc^2-2+((1/Qtc^2-2)^2+4)^0.5)/2)^0.5

(IF ... THEN ... ELSE for you programmers out there)
If Qtc>(1/2)^0.5 then dBpeak = 20*log(Qtc^2/(Qtc^2-0.25)^0.5) else dBpeak = 0

Vb = net box volume (L)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak/saddle point in system response

Sorry man - this is how you figure out the resonant frequency. That's why there are audio shops and pre-canned software to figure this out. I just threw out some equations out there for anyone that wants see how they come up with this stuff.

Easy way to figure it out - look at the sheet that comes with the sub. It will give you guidelines on how big to make the box. Then experiment with some audio foam (looks like fiberglass) and stuff the box with more of less stuff and optimize the sound (can be checked with a voltmeter). Then experiement with moving it around in your trunk to see where the sounds is best and rattles the least.

oh ok, I understood it that time