Advice on building some SPL sub boxes

[holdenboy]

So DVC 4 ohms subs wired in series inside the box (8 ohms) then wired in parallel to the amp (4 ohms)........surely you mean amps so each amp sees 2 ohm?

What ive found to be the easiest (and loudest) is to do the old strip, wrap and tape. Its not the best for a solid connection but does not sacrifice any conductivity as its just copper on copper.

 

[acarmody]

My amps do see their most power at 2-ohms, but when they are linked it makes it a single 4-ohm.

 

[acarmody]

Well ports are just about finished. And I did an embarrassingly crap job of using resin to round of the edges of the box. But to give an idea of the weather is like here, I spread the resin at 1pm, come 9pm and its still soft and sticky, and yes I did use the right amount of hardener.

 

[holdenboy]

Yep, add 40-50% extra hardener if the temp is under 15 degrees, 8 hours is ridiculous.

 

[acarmody]

Tomorrow is supposed to max out at 20 degrees but still windy, so probably going to be cold still. Extra hardener it is.

I felt like a bit of a retard today, I had the 4 pieces of PVC cut to length and flared, and then put both coupling on and then put them in the boxes, then it hit me, I need 2 ports per box, so 8 halfs in total, :bang: . Also the 4" pipe I have is pretty hard to flare compared to my 6" stuff. This stuff is pretty easy to bubble or split, I'm getting a bit better than 50% success/fail rate.

 

[acarmody]

I just need to wire up the second box tomorrow and I'm done with construction, not enough time to fiberglass though. I did run one box with one port blocked so I can listen to it on the way to work, and damn this one box is nearly as loud as the two sealed one together. ALso I tried a few places today looking for an SPL meter and bloody hell not many people have them, Northfield Moorooka has some other brand SPL meter that they use for comps that goes up to 160dB but they are completely booked out.

 

[holdenboy]

Looks the goods, i assume the bottom port is just blocked for music?

Yeah Northfield Moorooka probably have an AudioControl mic.......sounds like it anyway.

 

[acarmody]

Yep blocked for music. And yeah that brand sounds right.

Alright so it looks like I will be tuning on the day. So the peak frequency should be between 40-50hz right? So if I take a 40-50hz sweep and also a track with each one of those frequencies (40hz, 41hz, 42hz etc) I should be right? Or do you think I should make a track that goes up in 1hz increments with about 3seonds per frequency?

EDIT: I don't suppose you know where to get these frequencies from?

 

[acarmody]

There was a small problem using the joiners as it tends to flatten where it clamps down and balloons out thus creating an out of whack join, solved by using a middle clamp as well as the two on either end, very straight now.

All finished and ready for the comp tomorrow.

I still need to find some tone tracks.

Also my plan for tomorrow is, 1st run is a 40-50hz sweep, find peak frequency, 2nd run just burp that frequency, 3rd run is wire down to 1/2 ohm and pray. Sound about right?

 

[holdenboy]

Great job, looks awesome (loud).

Did you sign up over at DecibelCar.com? There is a download for a test tone CD (includes sweeps i think) on there.

At the top menu, click on Knowledge Base then Downloads, the test tone CD is in there.

But yeah, run sweep at 3/4 volume so you dont heat up gear / drain battery when the score dosent matter. Second run play the peak at full volume and third run you can load it 0.5 if youre not happy with the score, if you are happy theres no point risking amps to gain a db or so, if thats the case then try one track down (one hz) with the same volume for the third run......also make sure to charge the battery in between runs (if power is available, if not then run the engine for 5min beforehand).

Try to keep the interior / boot as cool as possible, i know it wont be that hot up there but cool gear = good numbers.

I'll be online for a few hours tonight so just PM or reply in here as usual if you have any more questions.