Newb wants to know the interaction of a N2400 network

[Bemopti123]

Hi, I am a newb who just purchased a pair of N2400 JBL crossovers in an Ebay auction. I have read that some of these crossovers are either 8 or 16 ohms, most of them being 8 ohm?

The question I have is when I go hunting for other components that go along with these crossovers. I see many JBL 075 tweeters that are either 16 or 8 ohm and older entire systems being 16 ohms.

What would be the issue with interactivity when I go hunting for components, I am right now pretty ignorant about the ohm of the crossover I purchased thus I am puzzled with which sort of components I should go searching for.... 8 or 16 ohm?

If I actually have purchased a 8 ohm crossover, is there anyway these can be electrically changed to make them into 16 or something similar?

Anyway, any experiences and opinions would be appreciated for a total newb.

Thanks.

Paul from NYC

[JeffW]

Here's a link to the schematic,

http://www.jblproservice.com/pdf/Network%20Schematics/N2400.pdf

somebody else will have to address the impedence issue except that the 075 are all the same, regardless of how they are labeled
Here's that link

http://www.audioheritage.org/vbulletin/showthread.php?23869-075-2402-076-2403-2404-077-2405

[Bemopti123]

Thanks for the info. So, all 075s are what they are 8 ohms, regardless of the fact that they are being advertised as 16 ohms....but the bidding feast that is happening for those labelled 16 ohms in Ebay is really puzzling, why almost double the price if they are the same as the 8 ohm version? Perhaps the bidders in question know something that some other people don't?

It is truly puzzling.

Paul

[scott fitlin]

Thanks for the info. So, all 075s are what they are 8 ohms, regardless of the fact that they are being advertised as 16 ohms....but the bidding feast that is happening for those labelled 16 ohms in Ebay is really puzzling, why almost double the price if they are the same as the 8 ohm version? Perhaps the bidders in question know something that some other people don't?

It is truly puzzling.

PaulYes it is sometimes confusing, but even though the 075,s are labeled 16 ohms, and all bullets are actually the same impedance, 10 or 12 ohms in reality, there is one thing that REALLY is different between the original 075, 2402, and 2402H.

The 075 and older 2402 have ALNICO magnets, and the later 2402H has a ferrite magnet. Over the years some people feel ALNICO has the better sound, and others say there is no real audible difference between the two. Regardless of whether or not an actual sonic difference exists, ALNICO is a more expensive magnet material because of it's primary ingredient COBALT!

Collectors and some audiophilliacs seek out the alnico magnet versions, and they will usually fetch higher prices than their ferrite equivalents.

Hope this puts things in perspective! :D

[JeffW]

Thanks for the info. So, all 075s are what they are 8 ohms, regardless of the fact that they are being advertised as 16 ohms....but the bidding feast that is happening for those labelled 16 ohms in Ebay is really puzzling, why almost double the price if they are the same as the 8 ohm version? Perhaps the bidders in question know something that some other people don't?

It is truly puzzling.

Paul

Unless they were NIB, I wouldn't care what they were labeled, impedence-wise. Probably the best thing you could do IMHO would be to install new diaphragms in some Ebay beater tweeter, anyway.

Snag some "8 ohm" models and use the money you save to buy some authentic JBL replacement diaphragms.

[Bemopti123]

So, are the diaphragms that JBL sell NOS or something common that they stock? Someone in GON was advertising the fact that the had gotten hold of NOS JBL diaphragms vs the stuff that is sold for $29.99 in Ebay and he made it seem that there were worlds apart.

The question go such as this:

1-Are original JBL 075 diaphragms easy to obtain or are their supplies limited? What are they supposed to go for?

2-Anyone tried to do a diaphragm swap with equivalent OEM diaphragms just to have the sound get worse?

3-What is the deal with those 075 with red wax covers over the screws and what can you expect if the unit you got necessitates a diaphragm transplant? How do you know this sonically?

4-Are there any woofers that are electrically compatible with the N2400 network that can replace the D130 woofers or pretty much am I stuck with getting those?

Thanks!

[JeffW]

So, are the diaphragms that JBL sell NOS or something common that they stock? Someone in GON was advertising the fact that the had gotten hold of NOS JBL diaphragms vs the stuff that is sold for $29.99 in Ebay and he made it seem that there were worlds apart.

You'll find little love here for aftermarket tweeter diaphragms. You can still get the real JBL diaphragms Here (http://www.speakerrepair.com/mm5/merchant.mvc?Screen=PROD&Store_Code=genem&Product_Code=10-274&Category_Code=JBL-Diaphragms).


The question go such as this:

1-Are original JBL 075 diaphragms easy to obtain or are their supplies limited? What are they supposed to go for?

See link above.


2-Anyone tried to do a diaphragm swap with equivalent OEM diaphragms just to have the sound get worse?

If you put something other than a JBL diaphragm in there, then it's not JBL any more, strictly speaking. If you've got the equipment to do before and after measurements, then you're set. If you're looking for somebody to tell you that the $29.99 diaphragm will measure and sound the same, you're in the wrong place. Not to come off as harsh, but this topic pops up regularly.


3-What is the deal with those 075 with red wax covers over the screws and what can you expect if the unit you got necessitates a diaphragm transplant? How do you know this sonically?

The wax seals (if original) just mean the screws and thus the diaphragms haven't been changed. If your drivers were only played by a little old lady at low volume on Sundays, you might not need to change them. If they were rode hard and put up wet in a sound reinforcement application, they could look (and sound like) confetti in there. I wish I had kept the last pair of 2402 phragms I took out of a used pair of 2404H-1 tweeters. They played, but looked like a crumpled beer can.

New JBL diaphragms aren't exactly cheap, but they'll last a long time if not mistreated. Me, personally, I would buy some other brand of budget tweeter before I'd spend the coin on getting a JBL unit and putting an unknown diaphragm in it. That's not exactly true. Me, personally, I'd buy JBL drivers and put JBL parts in there (except maybe some of those 4" TruExtent Be phragms for the 2" compression drivers, but that's another story).


4-Are there any woofers that are electrically compatible with the N2400 network that can replace the D130 woofers or pretty much am I stuck with getting those

Thanks!

Somebody else will need to give that a whirl.

[scott fitlin]

To add to what Jeff says, I have tried aftermarket diaphragms, and they, well, some, are really different sounding than original JBL parts. It's hard to say that the actual alloy used in aftermarket parts is exactly the same, OR the weight of the diaphragm, and then there is the voice coil. A JBL voice coil is wound to JBL specification. Aftermarket parts try to approximate JBL,s parts as closely as possible, but I doubt they are really trying to exceed original manufacturers specification or even be as good. Things like weight, and the VC will definitely affect the sound out of your unit. Now, lets say you have two JBL 075 tweeters, and you refresh one with an aftermarket part, the other has it's original diaphragm. More than likely, you'll have two distinctly different sounding speakers, and for my money, this is NO GOOD!

A JBL diaphragm for a 2402, 2402H, or 075, is around $130 at OCS! An aftermarket equivalent is around $60. I know that the JBL part might not actually need to be priced that high, nor cost them that much to make, and OTOH, I also subscribe to the school of thought that " There Ain't No Free Lunch " in this world. Meaning that for less than half the price it is hard for me to believe I am getting the same quality as the JBL part. I also know that when we bought our JBL 2402H new in 1983 or 84, new JBL diaphragms then cost $75 or $80 a piece! So, how is it that in todays economies with only everything going up in price, the aftermarket parts price today, is lower than what I would pay for ORIGINAL JBL parts 25 years ago?

On a personal note, I have to replace a 2402 diaphragm myself, and I called a supplier, and they don't have the JBL part in stock. They offered me the aftermarket equivalent at the price I mentioned above, and I asked ARE THEY THE SAME SOUNDING? Their reply was that they are pretty close, and hard to tell! Well, that answers that! I feel I was being told they DO sound a bit different but, OK, that's enough, stop right there! I'll wait for JBL parts, thank you very much!

[Bemopti123]

I have learned much from your posts. There is NO WAY I would pay $260 for a pair of JBL advertised diaphragms and then have them switch it to some generic, no names.

So, perhaps I will be learning for a pair of pro versions of the 075s with new original JBL diaphragms in order to start my journey.

Thanks!

PS: I will be wondering about the last question I have had about the acoustical/electric equivalent of the D130 woofers.

[HCSGuy]

I'm not sure if I can answer your question, but I'll take a shot at it. The N2400 was designed to pair an extended range woofer (D130, D131, D123) with a 075 tweeter. The 2500hz crossover point puts it too high for a conventional woofer, so I can't think of a significantly better woofer that keeps the efficiency and upper range of the 130 but goes any lower, but one of the sound pros may have a better idea. Also, the N2400 had a long production run (approx 1957 until the end of JBL's enthusiasm for the home component business, probably the early 80's?). In that time, woofers transitioned from nominally 16ohm to 8ohm, so I suspect a running change was made in the crossover sometime around 1966 to accommodate this change, which you allude to in your original post. To find out what version yours is, you can post pictures and we'll guess, or you can drill it, open it up, and post component values and we can figure it out. You can check the tweeter attenuator knob - is it stepped or continuously variable? If stepped, 90% chance you have a 16ohm version; if continuously variable, 90% it's 8ohm. Unfortunately, as I think your upgrade path would probably include first replacing this piece, I would leave it clean, resell it, and build towards a S8R configuration or something else with more flexibility.

[Bemopti123]

From the experts here...would it be crazy to get a pair of 075 and use the N2400 to divide into the woofer portion of a Altec 604-8K to act as a D130? This would be a piece meal deal until I really get myself a pair of proper D130s.

PS: Have anyone done comparisons between a pair of these JBL drivers vs a Coaxial 15" such as the Altec I am talking about?

Thanks!

[Bemopti123]

After two weeks of bidding, I got myself close to perfect pairs of 16 ohm JBL 130As as well as 16 ohm o75 tweeters with original diaphragms! In order to start to play with it, I crossed the 075s with the N2400s into a pair of backloaded horns with a Fostex 206/8 Sigma fullrangers, old style with the whizzer. This set up in incredible. I never thought that the backloaded horns with the Fostex drivers were really that great but it was not until this haphazard set up that it sounded incredible.


Now, the question goes....about that N2400 upgrade. I saw the thread where a member basically gutted the N2400 and put everything back with better specs. When I went to the PartsExpress website, I saw that for the Lpad pot, there is an option of getting an 8 ohm Lpad or a 16 ohm one. Will the change to the 16 ohm Lpad improve things, because my N2400s are the 8 ohm variety sold in the late 60s to mid 1970s.

Any input is appreciated.