View Full Version : values on resistors in Lpad circuit, L96

Peter Kaae

01-13-2005, 08:21 AM

Iīm thinking of bypassing the potīs in my L96 speakers, and make a Lpad with two resistors instead. I know from previous threads, that it can enhance transparency in midrange and treple.

Could anyone tell me what value the resistors in this Lpad should measure?

/Peter

LE15-Thumper

01-13-2005, 09:41 AM

Set the L-pad the way you like it. Remove the L-pad from the circuit carefully without turning the shaft. Take an ohm meter and measure resistance this way :

R between pin 3 and 2 is your series resistor and R between pin 2 and 1 is your shunt / parallel resistor. Usually a 5 watt resistor should be large enough

Anyone feel free to let me know if I am incorrect.

Peter Kaae

01-15-2005, 08:01 AM

I find the values a bit confusing. I measured the values between pin 1+2 and 2+3 ..the pot is in centerposition ("zero") , and measured 4 ohms between 3+2, and 17 ohms between 2+1.

Now, the 17 ohms, which is the "resistor" parallel to the driver confused me.

Because, When the series resistor is 4 ohm, the parallel should be 8 ohms, right?

I see it like this ; if the driver is 8 ohm, we can put a 8 ohm resistor parallel, then the load would be 4 ohm...so we should put a 4 ohm resistor in front of that ( +side, in series), then the load would be 8 ohm again, but with attenuation, right? I Appreciate it, if anyone could give me some advise,

Thanks

Peter

4313B

01-15-2005, 08:22 AM

I Appreciate it, if anyone could give me some advise.Ok. I'm back.

Pull the L-Pads out and pull the 2.4 ohm and 20 ohm resistors out of the midrange circuit. If you have your L-Pads currently at the 12 o'clock positions for both the midrange and high frequency transducers then a rough estimate for replacement would be:

3.3 ohm series and 12.0 ohm parallel on the high frequency transducer

4.3 ohm series and 6.8 ohm parallel on the midrange transducer

You will probably want to use at least 20W on the midrange transducer. Double up on resistors to increase power handling and get the desired values in the charts. Here are some charts of values based on attenuation and common resistor values.

Additionally, if you Google for L-Pads and Attenuation networks you should find a few calcuators already waiting for you instead of having to slog through the math.

Earl K

01-15-2005, 08:49 AM

Giskard has posted a bunch of useful info for you ;

Additionally, here are a couple of personal observations to mull over ;

(A) Your basic understanding is correct in how the value of the "series" resistor is derived.

(B) Now many people fail to "zero" the DMM ( its' not always possible ) or at least get an impedance measurement of the probes themselves. These values can be surprisingly high if using a "Radio Shack" type DMM meter. I've seen "R" values as high as 1.6 ohms ( I just measured mine ). The probes themselves represent 1.4 ohms. This DMM can't be "zeroed" . Approx 4" of 14 gauge wire strapped across the DMMs probe receptacles - results in an approx. reading of .2 ohms . Obviously, in my case ( if I used those stock probes ), I would need to subtract 1.6 ohms from all my readings or (at least .2 ohms if using "zero-load" probes ).

Hope some of this helps <> Earl K

Peter Kaae

01-19-2005, 03:40 PM

..Thanks to LE15thumper, Earl K and Giskard.

I was very sucesfull with the Lpads. Was rewarded with

more details in the midrange and treple. Theese Speakers

are definately among the best JBLīs Iīve ever heard.

I can not think of a speaker that present for instance vocals

that realistic..itīs very exiting to hear Erykah Badu that close to me!

I allso replaced the LF 2,5 Mh Inductor with a better type, and could hear a stronger and more defined LE10H-1.

Now, I was thinking, if there is more things to tweak with

the N96 crossover? I have noticed that the 4313B have a slightly different circuit, with a conjugate in LF? Does this

make the LF perform even better? It seems like the midrange is cut at a bit deeper in frequency?, and the LE5 and 044 is opposite polarized in the L96 and is not in the 4313B? Is it better to polarize them as in the 4313B?

Greetings,

Peter

4313B

01-19-2005, 03:44 PM

Now, I was thinking, if there is more things to tweak with

the N96 crossover?Build a pair of biased 4313B networks.

boputnam

01-19-2005, 05:51 PM

Build a pair of biased 4313B networks. From the wayback machine - originally posted (and designed by...) Giskard, circa 2004:

Guido

01-21-2005, 04:30 AM

Build a pair of biased 4313B networks.

I can only second that. And as Bo wrote don't forget the little bypass ones ;)

Look here:

http://audioheritage.csdco.com/vbulletin/showthread.php?t=4225

Better Inductors are always good. Look at those DCR's

http://audioheritage.csdco.com/vbulletin/showthread.php?t=4217

L3 is meant to be that high!

Zekeman

12-27-2006, 09:19 PM

Please confirm for me the correct wiring shematic for the N96 network to the LE5 and 044 drivers...are my assumptions below correct?

Mid

White Positive

White/black Negative

Tweet

Yellow Positive

Yellow/black Negative

Thank You.

Paul C.

12-29-2006, 06:59 PM

Someone above referred to an L-pad as a "pot", and if so, that may be a source of confusion.

A pot has one resistive element, with the center post (2) tied to a wiper.

An L-pad has TWO resistive elements, with the center post (2) tied to a wiper that sweeps both elements.

More info on construction and use of L-pads here:

http://colomar.com/Shavano/lpad.html

An online calculator for fixed L-pads is here:

http://colomar.com/Shavano/lpad.html

DO bookmark this page. It not only has L-pad, but also crossover and zobel calculators.

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