stipek

This was put on by the local shop and wasn't too serious. I got a trophy and a free t-shirt. It was decided that only music would be used so I didn't get to test any tones. The song I used was a standard bass song that has peaks at 30, 40 and 50 hertz. Once I do some testing I be able to narrow it down and hopefully get a little more db's. What was funny was that on my third run I tried the visors, glove box, over head compartments, etc. and gained a couple points, again not knowing if it would hurt or help. Some probably hurt while othere things helped but all in all I got a litlle. I did have the back seats down the whole time but I had a few people come up and ask what I was doing with the visors and stuff. Not that its a big secret I told them because we are all there to learn but these guys have been going to comp tons of times and they are asking me for advise and didn't know this. Small town and none are national competitors so they may not have researched as I do.

Oh yeah, that was on the glass too. Equipment: 2 MTX TR7512-22 (500W RMS) on a Jackhammer JH600 amp (600W RMS). Subs up port back tuned to 33 in a 2003 bravada. The runner-up was running american bass 12's with a 1000W amp in a bonneville. He had the rear deck speakers out. Beat him by 0.1 db. He had 0.1 db higher than me in his previous run. Definitely think I could use a power upgrade to 1000 or maybe even a 1200W amp. You can check out my build on here. 2003 Bravada build. Will put link in signature.

Went to my first comp and finally got some numbers. Only got to try 3 different songs but did my best with 141.7 db on bass mekanik - Dr. Oblivion and won the street b class.

Let's just say the first time I cranked it up I was like "Now that's what I'm talkin' about." Definely glad I made the change and SQ is still awesome. With the sealed I got some good rear view mirror vibration. Now it actually tilts down and I need to re-adjust it. That should tell you a little bit about the added force it has.

yes sir. impedance rise is highest around box tuning (for ported boxes of course) No, in a ported enclosure you will have two impedance peaks and the tuning frequency is in between them. Like this one would be tuned to ~31hz. This ported box is calculated to have 33 hz tuning but with the kerfed port there is no hard fact as to how much is effective port so that figure may be off just slightly... I used 1/2 the length. Also ported boxes peak usually 5-10 hz above the tuning freq. I have yet to get metered to see what the peak freq of vehicle or more so this "system" is. From listening to it I'm guessing around 45 Hz. Have had some say resonance freq of this vehicle is around that 45-48 Hz range. 2003 Bravada.

Wish I had a meter...I would do that for sure cuz as you said that is what would be more interesting is the db's.

Don't know how useful this information is but everyone ask how much of an output you gain from a ported enclosure vs a sealed one. Although these numbers don't directly relate to db's I recently switched out my sealed box for a ported one. All other equipment and settings remained the same so no other variables affected the test. Interpret them as you may. This is 2 MTX TR7512 on a MTX JH600 amp. (volume was not at absolute max clean because tones were at 0 db and I set the gains with a scope using a -4.6 db tone and did not want to reset them so I just turned the volume down a couple ticks)

I also heard that birch is stiffer than MDF which is better but how much better is unknown. It's not like your decidng between mdf and particle board. The next box I build I think I will spend the little xtra for the birch just to try it.

Thanks everyone..sounds like LB has the setup I'm lookin for.

Subs back about 6 inches from gate. Best removable box is to wire subs as desired to one set of screw type terminals that accepts banana clips and connect amp mono. Then you have one speaker wire to disconnect and take out the box.

Yeah the cap will be gone. It was a fix in a 92 lumina and figured i'd use it as long as I had it. Got an 03 bravada now. probably won't go bigger than that. As years go by I have less and less free time so I'm lookin for just what is necessary for this amount of power. So 1/0 big 3 with one run to battery in back and I can keep the stock bat and alt?

I'll lookin to upgrade in the future to 2000W so if I were to have say a crescendo bc2000 running two 1000W subs, what electrical upgrades would be necessary? Right now I have everything stock, no big 3, 1F cap. I was thinking 1/0 wire everywhere, big 3, and one extra battery (don't know which one). Would this be good?

Good thread...thanks. I think I will flatten it back out and then put a piece of wood at the end to run it down the port a little farther. I could just redo with the wood inbetween the two Pvc pieces but I'll probably have to 45 the bend because I don't want to choke it too much. Also think I'll do pvc on the two pressure points just because.

I was contemplating this also. If separating the two waves with the flat top T is most beneficial, then why not just run the divider all the way down. In other words what are the benefits of having a shared port? Don't mean to thread jack, just seems like a question for those reading this might also be interested in.

Here is the "T" divider using 3" pvc. So it only extends down the port 1 1/2 inches and the port width at the top is 2 1/2 inches. Should I make an extension from that down the port farther or will this be ok?

Oops forgot to erasw the first http...here it is. Here is a super rough draft of the box. Between which points do you suggest the 45?

Here is a super rough draft of the box. Between which points do you suggest the 45?

along the front panel right because the port is in the back. I have the bend in the front and that may be a little tricky. also i want to post a pic of the "T" divider. I used pvc roundover instead of 45 mdf. Never posted pics. How do I do that?

so if i wanted to, looking at the front through the port it would be the front left/right corners running vertical? I forgot to mention the port outlet has a 5 inch radius bend if this makes a difference.

Before i seal up my box, i'm doing subs up port back for 2 12's. the port is in the center and there is a T divider in the back. Any suggestions on what corners to put 45's in?

some say 1/3 of the kerf length is actual port length. it depends on how large the kerf is. if its an inch then it is basically noneffective. another rule of thumb is 1/2 the length. i haven't found any published literature confirming any calculations. for box building purposes i add 1/2 of the kerf length to the port length and the tuning should be close to the calculated tuning in torres.

Put it this way...it won't be quieter. I'm guessing maybe 2db gain. If that is worth it is up to you.

Kinda...you really have two 14.5h x 2w ports next to each other with no divider to create separate chambers. So when the port(s) get 2" from the back wall, one goes left and the other goes right

Some have taken out the rear deck speakers and let the sound into the cabin that way bouncing off the rear window sending it forward.

Yes the same for hpf and ssf. I believe with lpf setting u want to turn the knob up until voltage drops. If you want it set at 80 Hz, play a 80 Hz tone. Start with the knob at say 60ish and turn it up slowly until the voltage begins to drop. Tahdah. Hpf you go the other way. Play a 125 Hz tone and start with the knob higher than that and turn it down until volts drop. Ssf its safer to have the subs unhooked. And follow steps for settings lpf.