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Niklas Nord
04-22-2003, 01:42 AM
What would be the best solution for the JBL 2245H 18"
driver, suited for Very low frequency playback.

A flat response (in room) down to 14hz-18hz is that possible?

Lets say, i have 4 JBL 2245 woofers.

they will play frequency up to 50hz approx


Will 4 of them do some nasty things with my home?

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then from 50hz the 2234 will take ower...!!
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has anyone been trying to mount the 2245 with an passive radiator, like the stryke 18" radiator, in a big box with 2 or 3 radiators the 2245 would go lower and higher spl i think, but how would the hifi get... im in simulationmode right now:)

:p :cool:

Ian Mackenzie
04-22-2003, 02:12 AM
Nicklas,

It depends on what you are trying to do??

Box designs
Suggest you look at the article by Greg Timbers/ Lorr Kramer on the main site, it details all you need to know about the 2245H bass enclosures complete with drawings. I have seen other articles for Coffin style couplers at go very low also using multiple drivers.

I recall the 12 cu ft version is flat to 20 hertz, unless you live in a large living area anything below 25 - 30 hertz is wasted unless you sit over the top of the box a receive what is termed "global output " response which could result in a major bowel disfunction!

Matching to the System and the room
There are also problems with group delay using very low (ELF) subs crossed over low (50 - 80 hertz)and you will need to time align the cabinet for best effect, meaning the sub boxes will need to be positioned forward of the main system: See Drews Clues on the main site for setup and calibration of subs, Drews design uses the JBK 2242 18". Otherwise it will sound strange on musical program material.

I have not seen 18" passive radiators, but this would require more than one 18" passive per 2245 as there would be excursion limited output and compression of transients compared to a ported design.

Subs for Hifi
My 2245s are tuned to around 28 hz for -3db @ 32 hertz in a 9 cu ft box, as part of the complete composite system (JBL 4345) the results are outstanding in terms of bass extension and musical accuracy. With a Clair Bros Phase Linear 700 its also a killer for home theatre and in many respects sheer amp horsepower is a siginicant issue for sub woofers.

In most rooms there is significant 12 - 18 db room gain below 50 hertz so the issue of extension is not so crucial to me, more over the total response flatness and low distortion.


Please note I am by no means an expert, this is just what I have come across and learnt in practise.

I hope this helps

Ian

4313B
04-22-2003, 06:40 AM
Speaking of Drew, here's his 2245H solution:

http://www.audioheritage.org/html/perspectives/drews-clues/audiophile.htm

Here's the other links:

http://www.audioheritage.org/html/perspectives/drews-clues/drews-clues.htm

http://www.lansingheritage.org/html/jbl/reference/1983-subs.htm

MikeM
04-22-2003, 09:38 AM
check this out for a diffrent point of view. ( Instead of refigerator sized cabnets)
www.passdiy.com

Ian Mackenzie
04-22-2003, 02:45 PM
Hey Yeah,

Apparently he blew one of those 24" driver at a party!!! with an Xseries 1000 watt amp.

Why not consider the CLAW.

Ian