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Making the Nelson pass crossovers warmer
Making the Nelson pass crossovers warmer
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Old 9th November 2015, 10:54 PM   #1
Paulytwo is offline Paulytwo  Australia
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Default Making Nelson Pass Crossovers (l300) warmer?

Hi all,
I posted the below on another forum and it was suggested that I may actually 'contact the creator' here :-) Any suggestions would be appreciated thankyou.
A link to that post, with an attachment that runs you through my build is here http://www.audioheritage.org/vbullet...ossover-please


---------------------
G'day All,

I've completed my Nelson Pass crossovers and installed them into the speakers with pleasing results.
I do however have a little issue with the 'warmth' of the sound (please dont start having a go at me for describing sound with words... there just isnt another way in this post :-p), which got me to wondering...

The Nelson pass design for the midrange driver specified an 8 Ohm Lpad rather than the JBL standard crossovers 16 Ohm. (3133 equiv. circuit).

Also - I'm unsure of the impedence of the components in these boxes as they've been around quite a while... How can I simply find the impedence of each driver?... Can I just look at their resistance and estimate from there?

I'd really like to confirm that my impedences are wrong because that would explain the sound to me, and give me a path to resolve the issue.

Oh - also - What should the impedences of each driver using the Nelson Pass crossover be?

Thanks for listening - Any advice appreciated (outside of 'Go Active') :-) Thanks

Pauly

Last edited by Paulytwo; 10th November 2015 at 12:28 AM.
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Old 10th November 2015, 02:11 AM   #2
Old'n'Cranky is offline Old'n'Cranky  Australia
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Your new to JBL aren't you

All the info you require is on that very heritage site.

Search for the model numbers of the drivers you have.
Amazing the amount of info and JBL technical documents they have for free download.
Also search for L300 and 4333.
HINT - Look at the drivers and crossovers used for both EARLY and LATE productions of both.
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Old 10th November 2015, 02:19 AM   #3
Paulytwo is offline Paulytwo  Australia
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G'day ONC

Yes - Only been buying and working with them for 40 years. I was referred to this site from that one.

Thanks.
Paulytwo
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Old 10th November 2015, 08:34 PM   #4
2 picoDumbs is offline 2 picoDumbs  Australia
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Link not working.
Can you post schematic.
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"If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
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Old 10th November 2015, 10:48 PM   #5
Paulytwo is offline Paulytwo  Australia
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Hi Pico,

Thanks for looking - Here's the circuit diagram -
NP xover.PNG
Thanks again
Pauly

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Originally Posted by 2 picoDumbs View Post
Link not working.
Can you post schematic.
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Old 11th November 2015, 07:39 AM   #6
2 picoDumbs is offline 2 picoDumbs  Australia
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I haven't forgot ya Pauly. I will look at the crossover properly tonight.
Are you open to the possibility of building an amp?
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"If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
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Old 11th November 2015, 07:56 AM   #7
Paulytwo is offline Paulytwo  Australia
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G'day Pico,

Thanks!

No - I wont be building an amp! Here in Australia, you could buy a really nice amplifier for what it would cost to build one. Also, the amp I'm using to drive them (400W Mosfet) is a pretty good amplifier - certainly can sound wonderful.

Thanks again - I look forward to your comments.

Pauly

Quote:
Originally Posted by 2 picoDumbs View Post
I haven't forgot ya Pauly. I will look at the crossover properly tonight.
Are you open to the possibility of building an amp?
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Old 11th November 2015, 09:21 AM   #8
Paulytwo is offline Paulytwo  Australia
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Hi again Pico

I have been researching a bit more and thought I should mention that I have used foil inductors for L1 and L3 (the series inductors) -

The Values and DC resistance of each are;
L1
2.2MH & 0.59 Ohms
L3
0.18MH & 0.5 Ohms

Hope that helps or makes a difference
Thanks again

Paulytwo

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Originally Posted by 2 picoDumbs View Post
I haven't forgot ya Pauly. I will look at the crossover properly tonight.
Are you open to the possibility of building an amp?
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Old 11th November 2015, 09:30 AM   #9
2 picoDumbs is offline 2 picoDumbs  Australia
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Do you have frequency response measurements for your drivers?
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"If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
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Old 11th November 2015, 09:41 AM   #10
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by Paulytwo View Post
Also - I'm unsure of the impedence of the components in these boxes as they've been around quite a while... How can I simply find the impedence of each driver?... Can I just look at their resistance and estimate from there?

I'd really like to confirm that my impedences are wrong because that would explain the sound to me, and give me a path to resolve the issue.
Drivers are mostly resistive so often measuring resistance is good enough to tell the difference between 8 Ohms and 16 Ohms.
You can also look for the specifications on the manufacturers data sheets?
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"If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
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