Nelson Pass Crossover - Effect of driver impedance

[pauly]

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

[toddalin]

You don't state whether you find them too warm, or not warm enough, but I assume the latter.

I had LE175s and tried lots of LE85s/2420s, but they never had the warmth of the LE175. Granted the LE175s didn't have as extended of a high end, but they are smoother near the crossover point. Finally, I came across a set in a pair of 4330s that I would consider changing them for. For some reason, they had more warmth than the others I had tried. When I opened them up, I found they had tangential diaphragms, similar to the LE175.

But I wanted to add a bit more warmth, and to this end modified my crossovers to add a couple MFD to the mid-filter. This creates a "bump" at bottom of the crossover frequency that fattens up the bottom of the mid a bit. It is interesting that when the Nelson circuit later came out, he had also made this modification. I guess GEHA (Great Ears Hear Alike).

If you want more warmth, you may try to swap the diaphragms for a set of 2410 offerings or try a set of LE175s/2410s.

[pauly]

Thanks Toddalin,

Your assumption is correct (not warm enough) - Puzzling that they were with the old crossovers!

Thanks
Pauly

You don't state whether you find them too warm, or not warm enough, but I assume the latter.

I had LE175s and tried lots of LE85s/2420s, but they never had the warmth of the LE175. Granted the LE175s didn't have as extended of a high end, but they are smoother near the crossover point. Finally, I came across a set in a pair of 4330s that I would consider changing them for. For some reason, they had more warmth than the others I had tried. When I opened them up, I found they had tangential diaphragms, similar to the LE175.

But I wanted to add a bit more warmth, and to this end modified my crossovers to add a couple MFD to the mid-filter. This creates a "bump" at bottom of the crossover frequency that fattens up the bottom of the mid a bit. It is interesting that when the Nelson circuit later came out, he had also made this modification. I guess GEHA (Great Ears Hear Alike).

If you want more warmth, you may try to swap the diaphragms for a set of 2410 offerings or try a set of LE175s/2410s.

[JeffW]

Have you thought of asking Pass? He has been known to respond to questions on his DIY Audio forum.

http://www.diyaudio.com/forums/pass-labs/

[pauly]

G'day Jeff,

Great idea - thanks for that - I've posted there & let's see how we go!

Pauly

Have you thought of asking Pass? He has been known to respond to questions on his DIY Audio forum.

http://www.diyaudio.com/forums/pass-labs/

[ivica]

G'day All,



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?

Thanks

Pauly

Hi pauly,

From my simulation putting resistor of the value of 33 Ohms in parallel with the L-pad , and have changed R3 , R4 from 16 Ohms to 13 Ohms,
would give almost the same FR response if using 16 ohm L-pad instead of 8 Ohms L-pad, but it has to be enlarge L-pad position

regards
ivica

[JeffW]

G'day Jeff,

Great idea - thanks for that - I've posted there & let's see how we go!

Pauly

Looks like they shuffled you off into the Multi Way speaker forum, but you are getting some input here, so that's a plus!

[Odd]

To reach Mr. Pass try here.
He responds normally very quickly.

[pauly]

Hey Ivica,

That's cool! Thanks for going to all that effort.
What would happen if you got rid of C4?

Oh - also - I should point out that I am using component values as per the Nelson Pass circuit - for eaxmple, I'm using 8 Ohm L-Pads.

Thanks again
Pauly

Hi pauly,

From my simulation putting resistor of the value of 33 Ohms in parallel with the L-pad , and have changed R3 , R4 from 16 Ohms to 13 Ohms,
would give almost the same FR response if using 16 ohm L-pad instead of 8 Ohms L-pad, but it has to be enlarge L-pad position

regards
ivica

[pauly]

Thanks Odd!
I've done that and hope he'll respond.

Pauly

To reach Mr. Pass try here.
He responds normally very quickly.

[tjm001]

Have you thought of asking Pass? He has been known to respond to questions on his DIY Audio forum.

http://www.diyaudio.com/forums/pass-labs/

As I'm about to construct one of these Pass crossovers for my L300-like enclosures, I too find this a very interesting post. I just ordered the parts for the original schematic just a few hours ago. Thanks.

Tom

[pauly]

Gray Tom,Just thought I'd let you know my progress.I am quite happy with the sound now - first I added a 20 ohm resistor across the tweeter (slot), just as jbl did in their 4333 crossovers. They also did that with the horn but I added a zobel network across the horn. I used 1uf caps and 8 ohm resistors there.Then I retuned the boxes as my vents were too short for the 2234 woofers. All those things made a big difference however the clincher was raising the frequency of my subwoofer from 80hz to 120 hz. That has 'thickened' up the sound significantly.Anyway, hope you find my journey useful with yours.Pauly

As I'm about to construct one of these Pass crossovers for my L300-like enclosures, I too find this a very interesting post. I just ordered the parts for the original schematic just a few hours ago. Thanks.Tom

[tjm001]

Gray Tom,Just thought I'd let you know my progress.I am quite happy with the sound now - first I added a 20 ohm resistor across the tweeter (slot), just as jbl did in their 4333 crossovers. They also did that with the horn but I added a zobel network across the horn. I used 1uf caps and 8 ohm resistors there.Then I retuned the boxes as my vents were too short for the 2234 woofers. All those things made a big difference however the clincher was raising the frequency of my subwoofer from 80hz to 120 hz. That has 'thickened' up the sound significantly.Anyway, hope you find my journey useful with yours.Pauly

Thanks Pauly. I appreciate the info.

Tom