Impossible car audio challenge?

[Antichrist]

Talking about subs and amps.

 

My girlfriend has a small Cadence audio amp, and 2 Cadence 12" subs, SEALED. (Components picked and installed by me) I forgot exactly, but she's running somewhere between 500 and 600 RMS to both subs.

 

Her subs are in her 1996 Monte Carlo (car), in the truck, facing back.

 

Now the impossible part...

 

I have an OLD JBL GTS 180x amp, 60x2 @4 ohms, 90x2@2 ohms, or 180x1 bridged. And I just ordered a 12" Power Acoustik PEN 12W: 450 RMS.

 

I want to come as close to, if not louder then her with this sub in my 1995 Tahoe (SUV).

 

Manufacturers specs are 2.0 ported, with a 12.5" long port, 4" round.

 

I will be building the box myself, this weekend, out of 3/4" MDF. Any tips or suggestions for the box shape/design to get the most volume out of this sub?

 

Link to sub spec sheet: http://www.poweracoustik.com/pa2006/manual%20and%20catalog/Subwoofers/PEN-12W.pdf

[TulsaGeoff]

180 watts vs 1200? That sounds like a mission. I have my ports facing the back of the car and the subs pointed upwards. It's loud. Not sure about max configuration though. That's just what the custom box builder did for me.

 

Port tuning: 39hz seems kind of high:

Tuning of a ported subwoofer box is determined by a combination of port area, port length, and net volume of the subwoofer box. Tuning changes the frequency at which the frequency response peaks (is loudest) and can change the way a subwoofer box sounds in your setup. Your tuning choice will be determined by the goal of your system install.

 

If you're looking to achieve an SPL setup your car (getting as loud as possible), you'll want to tune fairly high. High tuning for SPL is usually somewhere around 45Hz or possibly higher. At this high of tuning, the sound quality will not be very good, but it will be louder than if you were to tune low.

 

A SQ (sound quality) based setup will call for a tuning fairly low - even down around 25Hz. This will also allow you to hit the ultra-low notes with your system. Lower-tuned boxes produce better sound quality, more like a sealed box. The downside to lower tuning is that it flattens the frequency response, which will cause the box to lack the boost around the tuning frequency.

 

To achieve a good mix between SPL and SQ with a ported box, we have found that it's good to be in the lower 30's for tuning. If you tune up around 35Hz, you'll get a fair amount of SPL out of the box and still have fairly good sound quality. If you tune closer to 30, the box will yield better sound quality but have a little less output than the 35Hz. A range between 30 and 35 Hz is generally good for most general setups.

 

If you want SPL, tune high. If you want SQ, tune low. If you want somewhere in-between the two, we have found a good tuning is right at 33Hz. This is why we default the port tuning to 33Hz on our customization pages for our ported enclosures. When choosing a ported subwoofer box, the freedom to tune the enclosure is a great way to get your system sounding the way you want it to sound.

[Antichrist]

She has 600RMS combined. Somewhere in the neighborhood of 250-300 per sub.

 

Manufacturer suggests a 4" round port, 12.5" long, and that lists tuning as: FB/F3 (Hz) 35/31. I'm not sure if this means it'll be tuned for 35, or 31.

 

I plan on using a slot port with similar area. 4" port = 12.56 square inches. I'm playing with slot dimensions now, and so far have come up with:

12.25 sq inches with a slot port 6.125" x 2"

12.75 sq inches with a slot port 6" x 2.125"

 

I'm definitely planning on lower tuning, I don't compete in SPL, and my sub preference is extremely loud SQ, or SQL as many call it.

 

Box dimensions I have so far: 15.5 width, 15.5 height, 19.5 depth, giving me a total of 2.04 cubic feet.

 

I'm tinkering a little with dimensions so I can add 1 or 2 braces within the box.

[TulsaGeoff]

Okay good, I saw the port frequency on those blue prints. Sounds like you have a pretty good idea of what to do.

 

Stiffen that box up. Stiffer = Louder. I'm sure you already knew this though

 

Are you going to carpet the box?

[Antichrist]

I'm still undecided whether or not to use a thin layer of polyfill on the inside walls to minimize deflections.

 

Port, I've decided on a 3 9/16"x 3 9/16" port, giving me 12.69 square inches of port area. Manufacturer calls for 12.56 square inches. I'm going to slightly round the inner corners of the port, and then give it a light coat of rubberized undercoating to 1: deaden any remaining deflections, 2: make it look nicer, and 3: I have half a can in my garage

 

I was going to skip bracing completely, since I'm only going to be running 180 RMS, But I have a ton of 1/2" MDF sitting in my garage that I can use for bracing, and I figure if I ever pick up a new amp, and double the power to say 400 RMS instead of 180RMS, I'll definitely need the bracing then.

 

Box will be carpeted in red garnet, to match the Tahoe's interior, and I'm currently planning on a recessed front baffle, and I'm going to either cover the front baffle in aluminum diamond plate if I have enough in the garage (obviously secured properly to eliminate resonance), or I'm just going to paint the front baffle in Arctic white to match the trucks exterior.

 

Is there anything I'm missing? Any suggestions/alterations? I'm still doing everything on paper now, and probably won't pick up the MDF until tomorrow or saturday, depending on when I get the design finished...

[Fogarty]

Simple : step 1:you take the woofer in a open box, just one single vent for more air-movement wich means that you hear more base.

 

Step 2: cover the inside of the box with (i call it pyramid sheets) you know what i mean probably the black cloth thing with pyramids on it.

 

Step 3: make sure the box is airtight except for the vent, also add a rubberring where the sub is placed so no air can get out at any time.

 

step 4: use both the channels from the 2x90watts) not sure if your subs got 4 attachments for cables, but if it does, place the first channel positive on the woofer, and the second one too, you can try if your amp can handle if you put positive to negative but i dont think so.

 

 

also make sure you use the right wood (mdf - at least 2cm thick) best is to double the back and front of the box.

 

well good luck with it bro, should be banging kinda loud like this

 

BTW!!! best is not to add anything stiff on the inside!! may cause a vibrating sound, but you can on the outside to stiff it, and tulsa, stiffness does not mean louder at all, and trust me i know what im talking about, ever seen my vids ive posted here on the forum? (directing you to youtube)

[TulsaGeoff]

BTW!!! best is not to add anything stiff on the inside!! may cause a vibrating sound, but you can on the outside to stiff it, and tulsa, stiffness does not mean louder at all, and trust me i know what im talking about, ever seen my vids ive posted here on the forum? (directing you to youtube)

 

 

The stiffer the box, the more efficient the speaker is. Its the whole basis for using MDF instead of particle board. Its the reason why SPL pro's use concrete and fiberglass in box and car design. Whenever something flexes like the box or the car you are losing potential decibals.

 

Will it make a difference? Maybe. Just saying.

[Fogarty]

The stiffer the box, the more efficient the speaker is. Its the whole basis for using MDF instead of particle board. Its the reason why SPL pro's use concrete and fiberglass in box and car design. Whenever something flexes like the box or the car you are losing potential decibals.

 

Will it make a difference? Maybe. Just saying.

like i said in my reply to anti: stiffening is helping to improve the sound, but not on the inside of the box,

[Antichrist]

Speakers work by moving air. Subs, speakers, it's all the same. This is energy. When something absorbs that energy, like a wall of a large box flexing, that WILL reduce power, and will most likely reduce SPL, efficiency, sound quality, etc...

 

What methods do you guys use for bracing in the netherlands??

 

Over here, I've only seen bracing done internally...

 

EDIT: And as far as vibrations, it shouldn't happen when internal braces are done properly.

[TulsaGeoff]

The box is going to have two chambers right, well seperate chambers for each sub? What is it going to look like?

[Antichrist]

Nope.

 

1 sub.

1 chamber.

1 port.

 

With 1/2 to 1/3 the wattage she's using...

 

Which is why I said it's an impossible challenge

[TulsaGeoff]

Nope.

 

1 sub.

1 chamber.

1 port.

 

With 1/2 to 1/3 the wattage she's using...

 

Which is why I said it's an impossible challenge

 

Oh my bad. I over looked the 1 sub If you could do something to where it doesn't slide around that would be cool. My box probably weighs in excess of 60lbs, but it can still slide back a few inches to the barn doors. The back of mine has some metal triangle brackets screwed into the floor. Maybe you could rig something up.

[Antichrist]

I have those same brackets for the cargo net. I'm probably going to just use a ratchet strap short term, but I'd like to add a little something back there so it looks nice as well.

 

I gotta get over to my girlfriend's garage this weekend to see how much diamond plate aluminum I left there. My whole design is really hinging on that crap..

 

And where the hell is Fogarty? lol I'm curious how they brace boxes over in the Netherlands. I've only seen internal bracing here. MDF, or threaded rods, washers, and nuts. Never seen an outside brace :-/

[TulsaGeoff]

You know that you are both going to have to go somewhere and get metered to make this official.

[Antichrist]

Ha.. screw meters. You ever hear of a butt dyno?

 

At our levels of SPL, it's not even worth metering. She's probably in the neighborhood of 132-135.

 

And box dimensions are finalized.

 

Outer dimensions:

20" wide. 15" high. 16.5" deep.

 

Inner dimensions:

18.5" wide. 13.5" high. 14" deep.

 

Total of 2.02 cubic feet.