L300 xo - 4313b vs np

[karina]

Can some1 explain the main differences between 4313B (http://www.audioheritage.org/vbulletin/member.php?15-4313B)'s version - which found in old thread:
http://www.audioheritage.org/vbulletin/showthread.php?166-4333-S300-L300-equivalent-bandbass-circuit&p=1042&viewfull=1#post1042

Schematic:

75439

To Nelson Pass:
75440

What would u go with?

[tjm001]

What would u go with?





I went with the Nelson Pass version. The 4313B version is circa 2003. The Nelson Pass is I believe from about 2011 or 2012 http://www.firstwatt.com/pdf/art_l300.pdf

[audiomagnate]

I went with the Nelson Pass but after extensive listening and measurement I flipped the phase of the mid driver back to where it was in the original JBL design. His other changes to the woofer/mid crossover are actually relatively minor. With the stock Nelson Pass design I measured (and heard) a massive suckout centered at 875 Hz. It's in his smoothed graphs too, although not quite as severe. I personally found the speaker unlistenable with the stock NP design. After I flipped it back they sounded like L300's again, which is to say fantastic. The difference isn't subtle at all. Purple is the original NP design, green is with the phase of the mid flipped back to the original design, i.e. in phase with the woofer. I know that a second order design put the drivers out of phase at the crossover point, but the voicecoils are about a half a wavelength out of phase to start with, so I'm guessing that's what's causing the suckout. JBL (GT?) got it right in the first place, which doesn't surprise me at all.

Here's Mr. Pass' reasoning for flipping the phase of the mid:

"Initially I worked with variations around the original in-phase wiring of the midrange, but I found it difficult to construct a filter which was flat at 1 KHz and also sounded as good as I wanted. I think the difficulty revolved around the distance time delay of the midrange, whichcan be clearly seen in a MLSSA pulse (that is to say there are two of them – one from the woofer and tweeter and another from the midrange). Finally I began working with the midrange phase flipped.This is where I had to choose between faults. There is simply not an ideal complementary match between the character of these two drivers. After some more experimenting, I worked up my best compromise - a midrange high pass network which is different in the details and response curve, but delivers most of the warmth, intimacy and articulation I was looking for.This is where the instruments have a “float in the air quality” that takes the performance out of the box and into your room."

I repectfully disagree. If you're running L300's with an NP crossover, try flipping the phase of the mid and post your results here.

[tjm001]

Thanks. Very interesting. I'll try that. Might take me awhile cause I just had knee replacement surgery. Can't bend down too good yet. Those L300s are heavy too.

Tom

[ivica]

I went with the Nelson Pass but after extensive listening and measurement I flipped the phase of the mid driver back to where it was in the original JBL design. His other changes to the woofer/mid crossover are actually relatively minor. With the stock Nelson Pass design I measured (and heard) a massive suckout centered at 875 Hz. It's in his smoothed graphs too, although not quite as severe. I personally found the speaker unlistenable with the stock NP design. After I flipped it back they sounded like L300's again, which is to say fantastic. The difference isn't subtle at all. Purple is the original NP design, green is with the phase of the mid flipped back to the original design, i.e. in phase with the woofer. I know that a second order design put the drivers out of phase at the crossover point, but the voicecoils are about a half a wavelength out of phase to start with, so I'm guessing that's what's causing the suckout. JBL (GT?) got it right in the first place, which doesn't surprise me at all.

Here's Mr. Pass' reasoning for flipping the phase of the mid:

"Initially I worked with variations around the original in-phase wiring of the midrange, but I found it difficult to construct a filter which was flat at 1 KHz and also sounded as good as I wanted. I think the difficulty revolved around the distance time delay of the midrange, whichcan be clearly seen in a MLSSA pulse (that is to say there are two of them – one from the woofer and tweeter and another from the midrange). Finally I began working with the midrange phase flipped.This is where I had to choose between faults. There is simply not an ideal complementary match between the character of these two drivers. After some more experimenting, I worked up my best compromise - a midrange high pass network which is different in the details and response curve, but delivers most of the warmth, intimacy and articulation I was looking for.This is where the instruments have a “float in the air quality” that takes the performance out of the box and into your room."

I repectfully disagree. If you're running L300's with an NP crossover, try flipping the phase of the mid and post your results here.

Hi audiomagnate,

I think it is very important where is measurement microphone being placed while doing measurements.
I would suggest to put it about to 3 m AWAY from the front panel at the "listening position height", and then make final decision ,
as measuring relative near the baffle (usually 1m away), time differences between drivers and the mic can introduce comb-filter effects.

regards
ivica

[johnlcnm]

Audiomagnate,

I sort of went thru the same scenario with a pair of 4429s following a thread by Bubbleboy. He measured the LF and HF frequency delay by inverting the phase of the inputs and looking for the best null. His number was 350 microseconds delay between the woofer and the mid horn. A number that seems reasonable. The 4429 is designed to be bi-amped. Two sets of input terminals and separate internal crossover networks. Using that delay I could tell the frequency response was different. Measurements confirmed a hole at 720Hz. Inverting the phase to the HF input corrected the hole at that frequency. However the sound was different then the stock 4429 driven normally i.e. in phase. The stock crossover is designed with the phasing of the two drivers incorperated. By my estimate I don't believe the driver delays can be measured accurately with the passive networks in the circuit. In the end the design of the crossover is integrated with the driver response and delays between the drivers. Bottom line: It would be hard to come up with a better crossover design for this system. I'm certainly not educated enough to do it. Oh, and JBL has the proper facilities and expensive test equipment to optimize the integration of their systems.

[Ian Mackenzie]

Have you considered the DEQX or mini dsp active crossovers? The issue is the path length differential

So a digital delay might be the answer if it made a significant improvement despite the dsp processing. Is the cost benefit worthwhile? Only you can determine the answer to that question.

Perhaps Ivica would be kind enough to help you and look at this as a side project because he has dsp active crossover and is fond of these horns.

Most of the efforts on the forums with dsp are using newer Jbl drivers.

It would be quite industrious if dsp was put to work for evaluation of before and after on Classics like the L300

Other than that l feel such a design is what it is.

It’s a classic but if you want a better sound buy the 4429 or build a clone 4435.

[audiomagnate]

I have a DCX 2496 that can do all that and I have triamped L300s with DSP in the past with great results, but these are for a buddy that wanted something simple. Stock L300s sound excellent to me. These didn't with the Nelson Pass crossover so I simply went back to the original phasing, which makes perfect sense and is verified by listening and measurements. This ain't rocket science.

[Ian Mackenzie]

In order to assist in resolving audiomagnate's concerns I referred your post to Nelson Pass who has requested I post his reply and a frequency response taken of the stock L300 and the modified L300 with the revised crossover.


Quote
"Hi Nelson

It would seem there is a difference of opinion on the L300 passive crossover?
Regards

Ian"

Quote
"BTW, I looked it up, and here are the curves of the loudspeaker
before and after. Clearly the phase of the crossover was not
altered from the original.

Perhaps this gentleman confused the white and black wires
of the crossover with the red and black of the midrange. My
reference was to the actual terminals on the driver.

np"


Below are links to others who have followed and built the Nelson Pass modified L300 crossover:

http://www.audioheritage.org/vbulletin/showthread.php?32305-JBL-L300-Modification-by-Nelson-Pass

http://www.audiokarma.org/forums/index.php?threads/got-some-new-crossovers-for-my-jbl-l300s.502767/

Quote
"I got one speaker done last night and was able to A/B between the new and old crossovers. WOW what a difference! :banana: I thought the old ones were good and couldn't imagine a HUGE improvement but thankfully I was wrong. Everything is SO much clearer and less grainy sounding in the HF. The bass is now shockingly well defined too - going back and forth between the two speakers (old vs. new xover) its amazing to me how seemingly blurred together all of the instruments are in the old vs. the new. Needless to say I am blown away and am putting in the second new crossover STAT :yes:. Thanks to Duaneange and dnewma04 for all their help with this!

https://www.stereo.net.au/forums/topic/84904-jbl-l200-to-l300-conversion-nelson-pass-x-over/"

[jfine]

I would stick with stock 300 xover design, but lose all the mylars and those wax filled caps in the resin box (leave em in, just unhook them), stock resistors, and use very nice caps, jupiters/sonicaps, mills resistors. Solens, Clarity, Daytons, etc., wasting $$$ and time, IMHO.

[Ian Mackenzie]

It makes sense to start with the L300 crossover so you can appreciate the qualities of original design.

But it appears you have been attempting to repair the original crossover and had other concerns with the compression driver looking at your earlier posts.(It might be more beneficial to continue in your original thread so the history of your journey can be seen before contributing or answering further questions.)

Have you resolved these earlier concerns?
If this is not the case my suggestion is start at the start and get the compression drivers serviced by a Jbl repair agent.
Then arrange new build of either the standard crossover (see L300 equivalent schematic) or the Pass modified L300 crossover.. The differences are discussed in the Pass article.

Fellow members have previously offered to do this for you.

The original Jbl crossovers are built and assembled in a way that only the factory or a service agent can repair. The complexity, potting of parts, wire colour codes, Jbl polarity conventions are easily confused by the diy loudspeaker person.

This came out in conversation with Nelson Pass yesterday.

In terms of diy you are better served to start a fresh and build a new network. Follow the schematic carefully and the parts list if provided. Ask or obtain help if you are unsure how to assemble a passive crossover and install it.

Good luck with your project.