View Full Version : Suggestions for improvement

06-05-2008, 04:55 AM
My latest project, now that I've moved into a new house, is to get the JBL 4670 theater speakers up and running. Yesterday, they were set up in the garage for a first run. Here's the parts breakdown on them:

Tweeter: 2445J with 2380 horns
Crossover: 3160 (500 hz) properly wired and padded down per the installation instructions
Woofer: 4508 cabinet with dual 2225Js wire in parallel. One driver recently reconed due to damage during the move.

Initial good and bad

These things can throw one heck of a great soundstage across a large 2 car garage alright. I listened to a number of tracks last night and the midrange is quite outstanding.

This is not the case with the low frequency end. Here things are quite muddy and seems to lack the depth and detail heard from the tweeters. Specifically, double bass is indistinct when plucked, massed low strings appear as a 'mass' rather than distinct. All these observations come from high quality recordings (Reference Recordings, etc) and my own knowledge of how a double bass sounds (I play in jazz combos and ensembles).

I realize these components are intended for theater work, but did expect better detail from such a setup.

So, any suggestions on how to improve this situation? I'll be spending the next few weeks with the setup, including moving them around the room but don't believe what I'm hearing is a placement issue - but I'm open to being swayed on that, too.

Test gear, here, not that great but can run frequency sweeps, etc, once the rest of the gear is pulled from a box.

Thanks for the suggestions!



Earl K
06-05-2008, 09:11 AM

A "biamped" 2226H ( tuned to 50 hz in a "critically damped" alignment of .5 Qtc ) has a tight enough sound / with reasonable "note to note defination" .

Suggestions :

- try biamping your 2226Js
- check the system alignment ( & tuning ) of the 4508 cabinet ( maybe its' too big & tuned too low ) . Do you have any SIM software to look at different box tunings for this woofer ?

<> Earl K

- FWIW, all things being equal, the 16 ohm 2226J is a "weaker" woofer when compared to the 8 ohm 2226H / strictly from the perspective of the BL figure ( the "J" isn't twice the "H" ).

06-05-2008, 11:19 AM
Dear David,

I am using the same 2445/2380 driver/horn combo on top of a L200b and just using the 2235-15" woofer. I biamped them using an active crossover at 800hz.

Its quite alot of sound for my workshop above the bar. I also have a dbx 2231 dual 1/3 octave EQ in the setup and the 2445 can get a little harsh at times, but will easily throw the music to the end of the building, easily.(75')

The 4508 enclosure is the same as my EN8 hi-fi enclosure I use for dj gigs, just in walnut veneer with a grill cloth. Very wife appreciated. Earl is correct to use two 2226h 8 ohmers in that cab when matched with a 2' driver.

Open up the garage door and point the stacks outside. How does it sound over at the neighbors house across the street? Pretty good I bet.


Mike Caldwell
06-05-2008, 08:43 PM
Just for the sake of checking have you verified the polarity / phase of all the 2225 woofers.

Mike Caldwell

06-06-2008, 05:32 AM
Thanks for the comments, folks.

Mike, after a career in computer repair and engineering, I appreciate your questioning all assumptions. I can confirm the woofers are in phase in both cabinets. These run in parallel at 4 ohms with the 3160 crossover.

As for switching to the 2226 series woofers, this _could_ get expensive quickly. I think this project will likely go in the bi-amp direction as I have the amps to handle it.

Thanks again!



06-06-2008, 05:47 PM
Just for the sake of checking have you verified the polarity / phase of all the 2225 woofers.

Mike Caldwell


Your post, in addition to another I read here while running through searches, got me to thinking a bit more:

Fact: So, I've picked up these 21 year-old movie theater systems which literally sat in the same position for 20 of those years until I moved them.

Fact: I reconed one driver due to moving damage.

Fact: I cannot confirm that they ever worked correctly as I purchased them within 2 hours of learning of their availability without any demo.

The age part started bugging me today so, when I got home, I pulled all the drivers and checked all the physical connections in the horn drivers, woofers, and the crossover.

Turns out that a number of these connections were loose enough to be turned by hand, including those at the back of the woofer cabinets where both of the 8 ohm woofers are brought together using lugs held together with pressure from the push terminal screws.

A good cleaning cleared things up nicely and the old beasts are honking on again. On other boards, I admonish folks to clean all their vintage gear first before they evaluate it. Should have taken my own medicine.....

Appreciate all the help and support, folks.