JBL L300 Modification by Nelson Pass

[10 Watt Street]

The January 2012 issue of Audio Xpress magazine has a revision of the JBL L300 by none other than Nelson Pass!
http://www.mygazines.com/issue/50140/11

[JeffW]

LOL, he probably just slapped a billet aluminum faceplate on it and a blue LED.

[grumpy]

Now, now... It's a good read and interesting DIY mod.

[JeffW]

Now, now... It's a good read and interesting DIY mod.

Whatever.

[Mannermusic]

Now, now... It's a good read and interesting DIY mod.

Yeah it is. Did you dig the 8 ohm series R in the horn circuit?! Also, very simple circuit and another way to eliminate the tapped coil. But the overall impedance has gotta be . . . changed significantly. Edison at work, like he said. 6 db, single pole tweeter with 1uF cap. Back to basics. Cool.

[richluvsound]

Thanks for posting this !

I may try this if and when I finish all the other projects ... Hopefully , GT will show Harmon the appropriate digit and set up shop with NP . WOW ! Can you imagine the frenzy that would cause in Japan ?

I silly dream I know ,but dreaming is still free !

Luvin Blue LEDs , Rich

[pos]

Interesting read, thanks!
Here are the relevant pages extracted in PDF

[4313B]

Very nice. I definitely like the single pole solution on the ring radiator.

And he experienced first hand the "fun" involved with that long exponential horn.

Someone needs to build a charge-coupled version of this network and give it a go.

[toddalin]

Some of the modifications reflect the findings and changes I made (e.g., slight shift in woofer circuit, lower crossover point to mid, simplification of the tweeter circuit) after final modifications when I built the "Keeper" crossovers for my L200/300s.

His tweeter circuit does not correct for the ~9KHz dip characteristic of the ring radiator design as the 3-pole original did.

[4343]

It does seem to smooth out the obvious peaks in the original measured response. CC is no big deal on the HF at least. Maybe I'll put together a Zilchnut version to try on a pair of bi-amp only boxes out in the store room.

[4343]

Well, I did build a pair of these, CC'd of course. Just from caps I had laying about., had to buy the I's and R's. Finished one cab and gave it a listen for a few minutes before other things got in the way of finishing the second. I might be able to get to it if it rains...

These are not L300's by any means, I have 2225H, 2461/2307/2308 and 2405 all stuffed into a tiny box with wheels, handles and a pole socket that have been bi-amped for decades, so this is just a way to lessen the load on the truck.

[badman]

LOL, he probably just slapped a billet aluminum faceplate on it and a blue LED.

Whatever.

Nelson's a longtime audio luminary, has done some great REAL circuit design, and is a staunch supporter of DIY. Your negativity is not warranted.

[Mr. Widget]

Nelson's a longtime audio luminary, has done some great REAL circuit design, and is a staunch supporter of DIY. Your negativity is not warranted.

Nelson Pass is an amazing man. He gives so much of his time and energy to help others enjoy this hobby... and he is genuinely gifted as an audio designer as well. Thank you "10" for posting the link... and thank you Nelson Pass for taking the time to share your journey!


Widget

[audiomagnate]

Is there a consensus around here on this mod? I picked up a nice pair last night and am very curious about this mod. I'm driving them with a Nelson Pass designed Nak PA7.

[georgebrooke]

Thanks for posting this !

I may try this if and when I finish all the other projects ... Hopefully , GT will show Harmon the appropriate digit and set up shop with NP . WOW ! Can you imagine the frenzy that would cause in Japan ?

I silly dream I know ,but dreaming is still free !

Luvin Blue LEDs , Rich

Hi Rich,

I know you are busy .. and I have heard your latest project. I am kinda torn about this upgrade. Firstly, Comparing my pair of 4343s against L300s "out of the box", IMHO, the 4343s run rings around them. Personally .. treading on ice here, I found my original L300s to be boomy and aggressive in mid/highs. The 4343s cured pretty well all of that. It would be nice to do all this with fewer units and simpler crossover and once the active crossover (on my project) is in place I should be able to simplify the passive part on the three top units in my 4343s and that is about as far as I would go. I am not convinced that these older horn units can be extended and tamed to cover accurately a broader audio spectrum. Can anyone nearby demo that I am wrong...please?
Having said all of that, I would love to hear the L300s again... especially with Nelson's new crossover.. so let me know when you are ready and I shall be on your doorstep

George