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Discussion Starter · #1 ·
Anyways, I have decided to go Pro speakers for my garage conversion and was able to buy three JBL 4622N and a JBL 4641 subwoofer for $1K used. Breaking it down, this subwoofer comes to $250.

http://www.jblpro.com/catalog/Genera...?PId=204&MId=1


Is it worth keeping this subwoofer with my JBL set or should I look elsewhere? I don't know what is the actual measurement of my garage but it's a 2 car garage. I was looking into a DIY sub for around $1K.
 

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I'd use it together and then make the determination.


It will all depend on the manner in which the JBL mates with the characteristic room gain. It is obviously a vented, pro design. This means it's going to be strong to about 35hz to 40hz, then being vented, it'll roll off rather steeply. The specs state it's tuned to 25hz, but I'd guess that's a bit low.


Regardless, it's a killer music sub, and it will perform strongly, very strongly with music. Special effects of the LFE channel in HT, which is spec'd 3hz to 120hz, will place this piece at a disadvantage. It's just not designed to plunge down below 20hz. But listen to it, and carefully, very carefully eq to taste and see what room gain gives you back to supplement the inherent roll-off designed into the piece.


WRT room gain, or more accurately Pressure Vessel Gain (PVG); One has room gain and boundary gain. The two are different ways to increase in room levels of LF. Boundary gain is corner or wall loading, and the maximum added SPL for each boundary is 6 dB per boundary. The corner loading will add 18 dB less whatever is lost through the boundary (the more rigid a surface is, the less SPL it lets escape). Boundary gain is limited to 1/8th the wavelength. For a sub crossed at 80 Hz that is about a 14 foot wavelength.


If the sub-woofer's drivers are within 21 inches of all three boundaries (for corner loading), you will get boundary gain up to 80 Hz.


Room gain applies when the half wavelength is the same size as the largest room dimension. A room with a maximum dimension of approx. 18 feet will yield room gain beginning at about 32 Hz. A room with a max length of approx 25 feet, will yield gain about 23Hz or so. Now oftentimes, due to the cubic dimensions of anything occupying space in the room, the room gain will begin at a slightly higher frequency.


So, give it a try, corner load it, feed it plenty of power, EQ it and enjoy. A caveat on EQing vented boxes must be stated; below tuning they can become unloaded, and oscillate wildly, so be careful. But the 2241 woofer, is one of the most durable, drivers in the world. It's truly industry standard 18" pro audio driver.


Good luck
 

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btw, I'll buy it for $250, save you the headache,..etc...
 

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Typically these do best in a HT setup with some LF EQ. That'll get you down to 30Hz with considerable authority. But as already mentioned the room is 50% of the battle. I certainly wouldn't rule this bad boy out without trying it for a while.
 

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I just want to commend you on a great find. I would have snatched up that package if I found it. Even if you find the sub inadequate for HT or just want further extension, that is one awesome music sub and for that price, very nice.
 

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Discussion Starter · #7 ·
Thank you FOH, rdgrimes, and Luke for the inputs. MKtheater, thank you for answering all my questions through all the PMs I sent you before and after I purchased these JBL, no matter how dumb the questions were, you took the time to answer them all. I will definately test it out to see how it sound once it is set up.


Luke,


I came upon these by accident months ago while looking through craigslist. The previous owner was trying to get rid of these for months and no one would take it. I came upon some of MKtheater's post and started reading up on his posts. After a few PMs with MKtheater, I felt it was a good buy. You should of seen my wife's face though, she almost had a heart attack as I drag these into the living room.
 

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Actually, the existing sub would make a superb, near-field, midbass tactile thumper, aka NMTT.


Install a (4)18" IB, to cover 3hz. to about 80hz., however in parallel w/the IB, place the JBL right behind the seating area, firing into the back of the seats, and operate it high passed at 30hz, and limited to about 65hz to minimize localization.


Best of both worlds!



Good luck, nice find.
 

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Another vote to keep it and try it out. That published frequency response is close to 90db 1watt/1meter at 20hz... not many dedicated HT subs can claim that. And the headroom from 30db up is just obscene.
 

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Quote:
Originally Posted by rader /forum/post/19616847


Another vote to keep it and try it out. That published frequency response is close to 90db 1watt/1meter at 20hz... not many dedicated HT subs can claim that. And the headroom from 30db up is just obscene.

Regardless of the specs, a pro design like this isn't made to produce 20hz at high levels. It likely rolls off around 35 or 40, and being vented, it rolls off pretty quick. Make no mistake, there's probably more of these 18s around the world than any other 18. It's a beast, a musical beast. Their 15s and 18s have nice low compression characteristics, so it will remain very responsive and take high levels of power for an extended period.
 
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