First Sub & Enclosure Build

[lajaro]

Hi all:

New to car audio and need some advice on my first enclosure build.

I just picked up a Rockford 110S4 Sub (10" SVC 4 ohm rated at 150w RMS). Will be powering with amp bridged at 100w RMS for a budget SQ setup off my factory stereo (will be sending 40w RMS to the front 3-way components and will leave the 2-way rears off the head unit or disconnect altogether). All speakers are stock.

I will be building a wedge for my hatchback (VW MKV Rabbit) with the sub firing towards the back of the car. The manufacturer specs say the volume of the sealed box should be 0.50 to 0.80, with the recommended volume at 0.65 ft3. I already have the dimensions laid out for the recommended volume (taking sub displacement and bracing into account).

I've read that "As a general rule of thumb, making the enclosure too small will result in a lack of low-end bass response, and if it’s too large, you won’t have as much output as you could and the woofer’s power handling will suffer."

Before I start cutting though, I wanted to check in with you experts for my application. Should be targeting the recommended volume, or if I'd be better off with a smaller or larger enclosure? Don't want it too loud - just want to fill in the low end and add a little thump to the tunes.

Cheers!

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[Trixter 10+ year member]

if your going to underpower it some, i would built it on the larger side, .75 -.90. being your first enclosure build, why would you choose a wedge? a square box would be easier....unless you already have some carpentry experience then never mind.

 

[lajaro]

if your going to underpower it some, i would built it on the larger side, .75 -.90. being your first enclosure build, why would you choose a wedge? a square box would be easier....unless you already have some carpentry experience then never mind.

Thanks, Trixter...

I'm building a wedge to maximize space in the hatch (effectively, will sit 3" further back than a rectangular enclosure would) and will allow me to fasten it better to the back of the seat. Got some woodworking skills and have mapped it out so don't expect any problems making it happen.

I'm not sure I understand why it should be bigger, though. Doesn't that mean that "power handling" would suffer? Guess I don't understand that statement.

Couldn't I also use some insulation to achieve the same result? (Just something I read about - don't really understand the implications of this, either)

 

[Trixter 10+ year member]

yes the power handling would suffer....but you giving it less anyways.

the larger the box, the more effecient the sub becomes....meaning the easier it will move with less power.

so...if your going to under power it, put it in a larger box.

the mfg's specs are for giving it the rms power. your only giving it 2/3 of what it can handle...so make the box on the big side...even 1cu' would be ok.

the opposite is true....if you were going to give it 250w rms, you would have to put it in a smaller box to handle it.

think of the air in the box as a spring (which it really is) the smaller the box, the tighter the spring and the less movement so the more power it can take.....the larger the box, the looser the spring and and more movement so the less power it can take.

polyfil...probably....

 

[lajaro]

Thanks again, Trixter.

So am I to believe that RMS power is inversely proportional to the enclosure size from recommended value, and in this case (doing some simple math), the recommended enclosure size would in fact be 0.975 cu. ft?

I'm not saying your recommendation is wrong, but I'm confused as there are mixed opinions all over the place, some stating that I should just stick with polyfill and build according to manufacturer's recommended size.

Your help (and others if they chime in) is much appreciated!

 

[Trixter 10+ year member]

yes...your statement is correct.

the poly fill would be good if you don't have the room to expand on the box and you want to tune lower. it will not make the sub more efficient from a power handling stand point. poly fill only slows down the sound waves. it does not increase the box volume (actually it would take away from it).

staying with the recommended size a poly fill won't hurt anything. i was just give out and option to use your sub to its full potential.