Box help for a 21'' sub

[dangaranga]

So my friend who is new to car audio decided to buy a cheap 21'' sub and i am trying to help him figure out a box setup. He wants to go sealed but I'm not sure if that's the best route.

It's Going in a neon and he says he has 28x22x15 to work with which comes out to 4.24 cu ft

Here is the sub and any help is appreciated and please no ridiculing about the sub he already admitted it was an impulse buy so help us lol

http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-2985-/55-2985

General Specifications:

• Nominal Diameter: 21 inch
• Rated Impedance: 8 ohms
• Operating Bandwidth: 25Hz ~ 2.5KHz
• Power Handling Capacity: 800W RMS
• Sensitivity (1W/M): 99 dB
• Voice Coil Diameter: 4 inch
• Overall frame diameter: 21.26"

• Thiele-Small Parameters:
• Resonance Frequency Fs: 25.9 Hz
• DC Resistance Re: 6.3ohm
• Mechanical Q Factor Qms: 3.51
• Electrical Q Factor Qes: 0.43
• Total Q Factor Qts: 0.38
• Equivalent Cas air load Vas: 705.0 liters
• Voice Coil Over Hang X-max 7mm

Physical Information:

• Cutout: 19.69"
• Mounting Depth: 9.29"
• Basket: Die cast frame
• Magnet Type: 100 OZ
• Cone Material: Treated paper
• Surround: Cloth
• Dust Cap: Paper
• Damper: Cloth

[bbeljefe]

The EBP on that driver is 60.23, which better suits it for ported enclosures but I would hazard a guess that that speaker will fall flat of its ass below 35 hz in 4 cubes.

It's a very efficient driver in a huge enclosure or, perhaps, infinite baffle but I don't think you'll be able to get much out of it in that air space because it was designed to be used in large venues, not small automobile cabins.

I stuck what T/S numbers were available into WinISD Beta and it wants 10.11 cubes for sealed and 20.44 cubes for ported, tuned at 27.5 hz. And WinISD recommends for flat responses, not the peaks we look for in mobile audio. To get it to peak around 40-45 hz like a car audio sub you'd likely need another 3-5 cubes of ported air space, lest you lose all of your low frequency response, as mentioned above.

I don't know if you remember the Terminator from back in the mid eighties but, it was a DB drag car that had a 30" PA woofer not unlike the one your friend has. It was a 1960 Cadillac hearse and the majority of the cabin was consumed by the subwoofer's enclosure. I don't know what your friend drives but there's a good chance that most of his car would fit in the subwoofer box for that EV 30". ;-)

I think you would do well to educate your friend on the differences between pro/venue audio and car audio rather than making a doomed for failure attempt at stuffing ten gallons of shit in a five gallon bucket. And that's not an insult to the speaker he bought. I'm sure it's a good driver in its intended environment.

[87chevyboi]

build an enclosure and put that bitch in his house beside his tv for surround sound or cd player, it will sound like garbage....Like dude said above, its got to be a hell of an enclosure for it and it just wouldnt work out in the longrun...More work for something that aint gonna pay off

[SnowDrifter]

A 21" in a neon? Based on your dimensions I'm assuming the trunk? In 4 cuft? Sub facing up? With a driver that's more suited to live sound vs. the car audio scene?

Dude I'm going to be honest with you: There is no way this will work well. Sorry. Put that thing in a home theater or something and get some proper subs for the neon.

[dangaranga]

Thanks for the responses guys, pretty much confirmed what i had thought and tried to tell him, he has 4 hifonics 12's sitting in his garage and i tried to tell him he would be better with two of those in the space he has available but he is set on using that 21'' lol so i am thinking after that 21'' doesn't work out we can add a baffle to the box and make the 12's fit in there hopefully

Thanks for the help

[bbeljefe]

Well then if he has other drivers, design a ported box for them and make the baffle replaceable, that way when the 21 sounds like sheeit all you have to do is build a new baffle and baffle him with your mad design skilz. ;-)

[dangaranga]

That's the plan lol i can't tell you how many people i have seen just go and buy something even when i or someone else tells them to stay far away only to be pissed and disappointed when it doesn't work out or sounds like shit lol

[CleanSierra]

If it were MY friend, I wouldn't waste my time or his even building a box for this sub. That's exactly what it is, a waste of time. If you are a good friend, just build the box for the 12s only. You don't want to risk the chance of the guy being like,"this shit SLAMS yo". I'm good enough friends with all my friends that they trust my input and knowledge in car audio. They wouldn't have me attempt a box that I told them would never work in the first place.

[dangaranga]

Well he just put a bid on a house so i will try and convince him to use that 21'' for a home or garage stereo setup, i am gonna help him build the box so that we can change out the baffle easily and throw in the 12's, at this point he pretty much wants to install it for shits and grins but i know he will dissapointed. His last setup he did himself with 4 12's in a sealed prefab in the trunk of his passat on an ap 1500, and my 1 12'' pioneer in the box i built in my truck was considerably louder than his and we even have the same amp so after that fiasco he actually started to listen to me on what to do and what not to do except for his impulse buy on this 21'' while i was away at college lol

[Kevin M]

I was going to use 2 of those 21" IB in my car before I did the 3 18". I see they have gone down in price too. The only way it would work in a box is if it were in the 8-12 cu. ported territory(at least)... And in a neon that means a wall. I think those 4 12" in the right enclosure will get him what he wants.