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dmtp
07-03-2008, 10:35 AM
I have searched the forum, but cannot find any specific info on the tuning freq (or vents used) on the various 4310/4311/L100 models.
These all had an interior cabinet of ~1.75 cf (if my math is correct based on 3/4" walls).
What was the diameter of the "hole" in the unvented (=3/4" vent) units?
What length vent tubes were used? (?same diam as hole?)
What frequencies were they tuned to? (easy to calc from diam/length or vice versa!)
If anyone has this info, a simple chart with the various options might be of a lot of interest!
Thanks!

dmtp
07-04-2008, 07:17 AM
Well, lots of people are looking, but none posting. :banghead:
With a little more sleuthing, I found the following:

L100 (early) = 2" d x 1" l (thickness of panel)
L100A (late) - 3"d x ~8" ("L" shaped vent)

no info on 4310/4311

Doctor_Electron
07-07-2008, 12:24 AM
Measuring one of my 4310WX, S/N 50871:
Back end of vent tube to baffle surface: 7.25 inches.
Opening in baffle: 3 inches.
The baffle opening is 3 inches, to a depth of 3/8 inch, then reduces to 2 3/4 inch dia. opening. (3 inch O.D. tube with .125 inch thick walls is inserted into baffle from rear, stopping 3/8 inch from front surface of baffle). Thus, the tube is 2 3/4" dia. for 6 7/8 inches, then increases to 3.0 inches for 3/8 inch.

ratitifb
07-07-2008, 12:59 AM
Try a search with woofer references like 2212, 2213, 2213H, 123A-1, 123A-3 + box ;)

Mannermusic
07-07-2008, 08:31 AM
I have searched the forum, but cannot find any specific info on the tuning freq (or vents used) on the various 4310/4311/L100 models.
These all had an interior cabinet of ~1.75 cf (if my math is correct based on 3/4" walls).
What was the diameter of the "hole" in the unvented (=3/4" vent) units?
What length vent tubes were used? (?same diam as hole?)
What frequencies were they tuned to? (easy to calc from diam/length or vice versa!)
If anyone has this info, a simple chart with the various options might be of a lot of interest!
Thanks!

Hi Mark,

I dug out the tuning data I ran on the 4312 Monitors I bought last year (HP signal generator). I think all these JBL bookshelf speakers are similar - same size. In a nutshell, they are tuned to 39 Hz. The Helmholtz double peaks fall at 64 Hz and 14 Hz. Obviously, it's the 64 Hz peak that makes the thing so boomy. I was able to get the thing to tune a bit lower - 36 Hz - by reducing the tube size from 2 3/4" X 9" to 2" X 9". This reduces the upper peak from 64 Hz to 60 Hz which sounds a bit better but still too boomy for my taste. Finally, the best result is to simply block the port (closed box) which results in a single peak at 55 Hz which is still no rose but listenable and audibly smoother as you sweep through the tuning region. It also changes the character of the overall sound, however - have to decide whether you like it depending on personal taste and your room acoustics, etc.

I also tried swapping in an LE10A (made an adapter) and found the Helmholtz tuning came in at 33 Hz with the 2" X 9" tube above. And closed box produced a single peak at 50 Hz which, again, sounded smoothest. Good luck with your experimenting! Mike

Earl K
07-07-2008, 08:51 AM
Hi Mark,

Some thoughts ;

- Any box with a port in it , becomes an helmholtz resonator. This type of box has a tuning ( via the port ) . " Fb " , typically is the notation used to denote the box tuning .

- Stick any speaker into this "tuned box" and one gets a " system - alignment" which is created by the interaction between the 2 parts ( speaker & tuned box ) .


Anyways ;
- I remember Giskard ( some years ago now ) , pointed out that JBL started out by tuning many of their older boxes in the lower 40s Hz range . This gave ( with the typical woofers of the era ) , a peak in the upper 50s - to low 60 hz area . Sure enough , my old S99 cabinets are tuned to about 41 or 42 hz and have a peak in the 60s area .
- Then they ( JBL ) changed their idea of a stock tuning by going lower ( into the low to mid 30 hertz range . By tuning down a bit , things got less boomy and the resulting droopy bass curve better matched up with the typical amount of LF room gain from the typical american living room . ( LF Room Gain adds it's energy into the mix & increases the overall amount of low frequency level ) .

- If you have some box tuning software , you can reverse engineer the tuning numbers to show you that a 1.75 cu' box ( with a 2" square hole cut into 3/4" plywood ) has an approximate tuning ( Fb ) of 40 hz . The same box with a ducted port ( something like the diameter & length mentioned by Dr. Electron ) will have a box tuning in the mid 30s . ( just like Giskard mentioned all those years back ).

- Hope this helps you somehow .

:)

Doctor_Electron
07-07-2008, 11:12 AM
Could an LCR etc. notch filter do anything for the 64 Hz. peak? What is the amplitude and width of the peak?
If that's not practical, what about using a parametric eq. in the signal path before the power amplifier? I am seriously interested. Thanks!

Mannermusic
07-07-2008, 02:13 PM
Could an LCR etc. notch filter do anything for the 64 Hz. peak? What is the amplitude and width of the peak?
If that's not practical, what about using a parametric eq. in the signal path before the power amplifier? I am seriously interested. Thanks!

Here you go, just what the Dr. ordered: http://www.marchandelec.com/wm8.html

Skywave-Rider
07-07-2008, 11:33 PM
Mark,
Interesting thread for me because I'm working with 123A-1s myself.
My box, repurposed (found) is 2.3 cu ft, not subtracting horn/compression driver volume, but taking into account woofer displacement. It is sealed and has about 80% fiberglass fill. You did not mention if you already have the cabinets, so here's my nearfield response, if you are building up, maybe you'd consider slightly larger?:hmm: