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alnico
12-26-2011, 10:10 PM
a question for the experts from JBL,

Excuse my English.
I have a home theater, JBL L-112 with front, rear and center for 4688 TCB cabinet low frequency(2240).

But I have a deficiency at the low-mid.
I would like the punch (kick bass) added at to the tcb 4688 (ultra low frequency)
Is it a good idea to add Jbl 4530 (with 2225) or Jbl 4648 which are mounted front speakers(front load).

What is the difference I would get with the speakers mounting " rear loading horns " and '' front load ".

thank you for also recommended for another model

more10
12-27-2011, 05:42 AM
A rear loaded horn will give more output in lower frequencies, front side of driver will add 3 dB to sound pressure from horn because front side is in phase with the horn. But when the front side is out of phase, at some higher frequency, there will be a 6 dB dip in frequency curve. For a 4530 the dips is at 150 Hz, for a 4520 around 120 Hz. The front side will be in and out of phase depending on frequency, creating a comb filter pattern.

In order to avoid this comb filtering, most back loaded horns have a back chamber working as a low pass filter, the horn will stop working at some frequency.

Transient response for a back loaded horn is a bit strange you can see some curves of that in this article: http://www.quarter-wave.com/Horns/Back_Horn.pdf.

Front loaded horns likes drivers with low QES and high BL, like JBL 2220 and 2202. JBL recommends 2225 for 4530, not very low QES at all.

more10
12-27-2011, 05:54 AM
http://speakerplans.com/index.php?id=1850horn
http://speakerplans.com/index.php?id=186horn

Front loaded horn plans. You are allowed to build 4 speakers from these plans. Unfortunately not designed for JBL drivers

Lee in Montreal
12-27-2011, 06:18 AM
The 4530 would be great for 50-120Hz. Great kick but not really a mid cabinet, and not easy to integrate as phase will be a problem (7' horn/delay). To complement your TCB, and to get great upper bass and lower mid (voice and snare drums) while alowing easy phase integration, I think you could use a set of 4560. And it's your lucky day as somebody on Montreal's Kijiji has a pair for dirt cheap, loaded with what seems to be 15" 2225 for $300 obo.

http://montreal.kijiji.ca/c-acheter-et-vendre-equipement-electronique-haut-parleur-W0QQAdIdZ339377526

54228

If I had extra room to store them, you bet they'd already be in my garage.

BTW Did you pucrhase the TCBs off Kijiji not too long ago?

alnico
12-27-2011, 07:49 AM
I do not think it would be difficult to choose.So should not I take 4530?And I would have better performance with 4560?

And what do you think of 4648 as 2225 are mounted in front (front loading).

Lee in Montreal
12-27-2011, 08:05 AM
I do not think it would be difficult to choose.So should not I take 4530?And I would have better performance with 4560?

And what do you think of 4648 as 2225 are mounted in front (front loading).

Boomy. Inneficient. Tasteless. If you have them for close to free, then sure. Test them. But as you already have three TCBs, you'll be cutting off the 4648's lower end and be left with the boring part they have to offer.

BTW The ad to which I linked you is missleading. The speakers are not really JBL 4560, but more like Altec's A7 which are also known for very sweet lupper bass and lower mid, while being very efficient. Also, here'S a shot I found of somebody preferng his A7s over a pair of 4648... (left of the picture). ;-) The A7 cabinets are musical cabinets. The 4648 are just boomboxes...

http://forums.klipsch.com/forums/storage/5/619769/Copy of more horns 023.jpg

Lee