Attn Autophiles: I need to port my sub box - help plz

[chuzie]

Got this info from the Memphis site.... It may as well be in Mandarin!


Model PR12S4V2
Driver Displacement 0.16cf
RMS Power Rating Net-Gross Internal Airspace 250w 1.373cf net-1.80cf gross
Slot Port Dimensions 12.5”x1.25”x18.5”
Tuning Frequency 39Hz

 

[BRONCROB]

That is simply giving the volume dispacement of the speaker and magnet in a ported box of specific volume with the dimensions for a port to produce 30 something hertz..low freq.bass...I wouldn't worry too much about perfection as far as box design goes.If you have a rear seat measure and see if the box you have will fit under it with a couple inches gap.That may give you decent bass and keep you from building a box.If you do decide to build a box,the rear pass corner is a popular spot for one and personally I wouldn't port it.

 

[AaronWelch]

So by what you listed above you are not putting enough juice into that woofer. It is rated for 250 watts RMS and your amp is probably putting out 35 watts X2 or 75 watts bridged.

 

[WorkerBee]

As previously mentioned you need to send more juice to that sub. A good quality amp and well matched box will make all the difference in the world. I have had really good luck with Crutchfield ( www.crutchfield.com ) in the past and their service is second to none. I would give them a call and buy a new box and amp. If you're the Amazon type you can buy some decent stuff off of there for cheap.

You can have the best sub in the world in a poor box with a poor amp feeding it and it'll sound like crap. On the other side you can have some fairly low cost subs sound pretty good if you put good clean power to them in a good box. Remember to buy proper size wiring and good quality patch cables. Those also make a big difference.

If you're up to the challenge of building your own box start learning online. There's a million online calculators to help you calculate port size, tuning frequency, etc. I have built many in the past with great results. I tend to lean towards ported boxes but sealed are also nice sounding when done well.

Good luck

 

[chuzie]

Thx fellas

 

[lowbush]

Thx fellas

The rating on that speaker to run it optimally is from 250 to 500 watts, try to get closer to that higher end. See if you can find a 500 watt monoblock amp that is reasonably prices and see what a difference it makes, as said before you can bridge the one you have but that is only going to put you at 100 watts still way under even the minimum needed.

 

[chuzie]

I find it odd that amp came with the sub. What a waste. Calling Crutchfield now.

 

[BRONCROB]

If you go amp shopping be aware that brand matters more than numbers. I have a Punch 200 sub mono amp and a XXX 1200 watt and the Punch drives two 10's waay better that the 1200 watt cheapo.Hell back in the day I had a punch 45 that sounded better than the 1200.

 

[chuzie]

Crutchfield just recommended the following:

Amp

http://www.crutchfield.com/p_777M1500/Sound-Ordnance-M-1500.html?showAll=N&search=777m1500&skipvs=T

Enclosure

http://www.crutchfield.com/p_777BB1...ker.html?showAll=N&search=777bb12150&skipvs=T

So if brand matters, how does this one stack up? This is a 4ohm sub so not sure how that computes with the rating of 500w@2ohms.

 

[BRONCROB]

I'm not familiar with that brand but the reviews look good.With your 4ohm sub you're looking at 300watts output which sounds like plenty.Make sure you have room for the box.What other speakers are you running for mids and highs?

 

[WorkerBee]

I don't have any experience with that brand either but Crutchfield typically doesn't sell junk. That amp will really come alive if you eventually upgrade the sub and run it at 2 ohms later down the road. Mono amps are designed to run at 2 ohms all day which is good. I believe from a cost standpoint they made a very good recommendation. You could always spend more but depending on how much you NEED bass it becomes an issue of diminishing returns.

 

[chuzie]

4 of these 5x8

2 of these cheap ass nb-4 with 1uf cap.

 

[BRONCROB]

Looks like your in good shape.

 

[Crawdad]

Go get a Rockford Fosgate Punch 300 and run everything with it! Ditch the 10" Chuz and get a 12", you will hear it more thump. Fosgate makes great amps, chk Amazon. I always had the Punch series which I think they still make. There's plenty of stereo shops down there, just go by one a chat with them.

 

[74strokerbronco]

do you have a model number on the sub ? you really can't design a box without either their recommended enclosure size for that particular driver , or whats called the T&S parameters. my bass box pro data base which I have not updated for atleast a year or so shows 104 drivers from Memphis but I could not find any with a 60oz magnet. but it's not like I looked at all 104 lol . 86 db is not a real efficient sub but non the less . some quick info the 86 db is reference to volume with 1 watt of power at a given hz.
for every 3db increase in volume you must double the power from the amp and 10db is equal to double the volume . also adding a 2nd sub is equal to a 3db increase in volume .hence double 1w to 2w 89db 2w to 4w 92db 4w to 8w 95db 8-16 98db 16-32 101db 32-64 104db 64-128 107db hence you have a clean 125 watts when bridged , to gain 3db more in volume you would need a amp that's 250 watts or add a another exact same sub .but to double volume you need a amp capable of 1000 watts or more and that sub won't take it . but a 3db gain in volume is quit noticeable. I had 2 jl audio 10's in a 5th order enclosure that with 1000w input would hit 133db in a car. for cars generally with the confined enclosed interior a given sub will act 12db louder than in a large room such as a house or open cab of a bronco.

 

[chuzie]

Wow. Great info. I think I will call Memphis and get this straitened out. You are right. Gotta have the model number. I don't want to do this twice.

 

[74strokerbronco]

I'm so out of date on the lines of quality amps , but the competition amps are always the better because there designed for low ohm loads and high current output, meaning a single amp can drive or power multiple subs/speakers . in my days of car audio competition back in the early 90's the fosgates and the true original no longer made phoenix golds ruled the shows. I still have a phoenix gold 2125 that mono bridged into a 2ohm load puts out a clean 1000w at .05% total distortion despites it's meager 125 watt per channel spec. in those days there was actually a standard of output rating for amps that manufacturers had to comply with now they can label just about anything they want. they give peak ratings with no distortion levels stated and the peaks are insane compared to true power. I've seen amps claiming 1000w peak power that component wise are only good to 125 .why they are allowed to claim it's a 1000w amp now is because they lowered the rating standards and because that amp may actually hit 1000w for 1 milli second when the caps fully discharge but at that moment the distortion levels are near 20-50% insane ! oh the good old days of honest RMS power are gone lol

 

[MyOriginal66]

Ditto on calling Memphis. I had a underseat box built for a JL Audio slim 13.5" sub. I called JL AUDIO and asked what the minimum airspace requirements were for the speaker. They asked me the dimensions of my planned box, what thickness material I was using for the box and what amp/power rating. They also asked intended usage (I told them a convertible early Bronco). They helped me compute everything and said I'm just above the minimum requirements but since I'm pushing 700 watts via a class D amp I'd be fine. I'm still 6months from hearing it but I hope it sounds good!

My box is sealed but firing down under a custom built rear seat.

All in all, if Memphis is anywhere as helpful as JL Audio was, it more than worth it to call them. Good luck

 

[TAWL_BOY]

Just remember that moisture will destroy MDF wood. I recommend getting a box in "outdoor" situations sprayed with bed coating.
If you will be running a ported box, you need to have it made where the inside can be sprayed too and then the last panel can be siliconed and screwed on.

But in drier parts of the country they may hold up better.