275nd / S3100 compatibility

[Bernard Wolf]

Hi everyone - I have searched the forum but still do not have my question answered. I am wondering if a 275nd would be a drop in replacement for the 2426H thats in the S/3100 now. Of course I know it will fit , as the 3100 mkII uses the nd, but my real question is will the crossover need to be changed as well. On one of the posts I read someone mentions that the sensitivity might be higher on the 275nd and thus require a crossover change. Can anyone confirm this ?

Also, I do wonder if it would all be worth the effort. Will the nd sound that much better? The reason I ask all of this is that there is one 275nd up for sale at the moment and I am tempted to purchase it and wait for another.

Any input would be much appreciated.

Bernard

[pelly3s]

there really is only one way to find out if it will sound better and that is to do it

[Earl K]

Any input would be much appreciated.

Okay, you've asked for some input :

- I'd say, buy the 275nd and just drop it in ( if the price is right ) .
- I also think that you should build some new "DC-Biased" crossovers, utilyzing better parts than those which presently exist in your stock crossovers . Make them external .

- I have searched the forum but still do not have my question answered. I am wondering if a 275nd would be a drop in replacement for the 2426H thats in the S/3100 now.

- I'm not surprised you can't find anything definative here. My recollection is that no one here, has ever done this "one for one" swap .

Of course I know it will fit , as the 3100 mkII uses the nd, but my real question is will the crossover need to be changed as well.(?)

- I don't think anyone here can tell you that based on my above point .
- But, I would always assume that a crossover should be tweaked for a different component type.
ie; Logically, why buy another driver type , if it's not actually different sounding ?

On one of the posts I read someone mentions that the sensitivity might be higher on the 275nd and thus require a crossover change. Can anyone confirm this ?

- I can't confirm any sensitivity differences, but swapping out resistors for more appropriate values is simple enough .

Also, I do wonder if it would all be worth the effort. Will the nd sound that much better?

- I've wondered about that myself. I hold more stock in the fact that I can readily hear the differences between the various types of metals used for the domes . But I find that any audible difference caused by the magnet type is much harder/ if not impossible to pin down ( at least with compression drivers ) . I've heard a response difference in le14 woofers, seemingly caused by the magnets ( Alnico vs Ceramic ) / though I tend to think the differences I've experencied were more likely caused by partially discharged alnico magnets .

- If it was me ( & if I couldn't stand the suspense ), I would buy a pair of 275 replacement diaphragms ( plastic coated Titanium ) and install them into the stock 2426 drivers .

FWIW - I think a more interesting upgrade path would be to retrofit a pair of 1.5" exit ( 243x ) drivers onto those big ( 1" entry ) horns . Zilch has mentioned an existing JBL adapter ( I think ) .

ps ; Now that Zilch has a pair of similar 2346 horns ( along with the mentioned 3" diaphragmed drivers ) / help for this DIY modification just might appear along with some RTA measurements .

[Zilch]

Yup, and some H2600's are on the way.

2346's are a "trip." Just discovered last night that phase relationships wander all over the place unless the woofer is properly aligned with that long neck.

I'm dubious about down-adapting 1.5" to 1", but I'll try it....

[Earl K]

Yup, and some H2600's are on the way.

- I thought I previously read that N2600(s) are on the way. Anyway ,,,
- You obtained H2600(s) ? Okay , who are you blackmailing ?
- Well, if you get a pair of H2600 horns, it would sure be nice to get a close looky-see at the metal throat adapters. I think the metal throat splits into two parts .

2346's are a "trip." Just discovered last night that phase relationships wander all over the place unless the woofer is properly aligned with that long neck.

- Properly Aligned ? What does it physically work out to be ?

I'm dubious about down-adapting 1.5" to 1", but I'll try it....

- Yeh, these adaptions/contraptions are always dubious / still the exercise will give one an idea of the LF loading capabilties of a horn/driver combo .

[Zilch]

- Properly Aligned? What does it physically work out to be?

What I know at this point is if you just stack 'em 2346's facing front on woofers (as in S3100) and get the two drivers in phase perpendicular, when you move the 30° onto real horn axis, you've got a big notch at 3110A 800 Hz crossover frequency. Inverting the HF driver phase makes it flat again, but screws it up perpendicular.

"WAIT! You just DID that, silly!"

Everest rotated the LF driver that 30° to put both drivers on parallel axes. I gotta free up some space here to work with different physical alignments to see what's up. Presumably H2600 will exhibit the same behavior. In any case, real time-alignment would appear to be, well, "challenging."

Regarding the 275ND crossover, clearly S3100 and S3100 MKII use different topologies, the latter using what I'm calling the "parametric" approach of cascaded notches. I'll have to model them both to see if the newer (12/00) MKII is really different, or merely "improved" over the earlier (11/95) 2426H version. That'll also answer the question of "drop-in" interchangeability of the two drivers. Both networks are 750 Hz, 12 dB/octave, looks like....

If you get a pair of H2600 horns, it would sure be nice to get a close looky-see at the metal throat adapters. I think the metal throat splits into two parts .?

We'll see. Comes with, apparently:

319381-001 HORN S2600/S3100 (+useTHROAT 318793-001)

May afford opportunity to make a custom 1.5" throat for 243x drivers....

[Bernard Wolf]

man .. ... you guys leave me in the dust so fast isn't not even funny

will take me a day and a half to figure all of this out.... but thanks for the extra quick response.... should have put a stopwatch on it

Bernard

[Bernard Wolf]

[QUOTE=Earl K]

- If it was me ( & if I couldn't stand the suspense ), I would buy a pair of 275 replacement diaphragms ( plastic coated Titanium ) and install them into the stock 2426 drivers .

/QUOTE]

Do you think that would be a drop in replacement then ? No need to tweek the x'over? Same sensitivity ? If that were the case it would be a simple way to go, assuming I can find the diaphrams that is.

Bernard

[Earl K]

Hi Bernard,

For The Sake of Clarity

Do you think that would be a drop in replacement then ?

- I'll only assume the 275nd diaphragm will physically "fit" into the 2426h magnet assembly .
- This "fitup" assumption is based on an older link to a web-page ( since deactivated ) that was posted by an ex-JBL intern/apprentice who built an MTM system using 10" drivers ( 127H-1 ) with a 2426 that was fitted with a 275nd diaphragm . Since he had "inside" ( JBL ) exposure to workable mods, I'm just following his lead .

No need to tweek the x'over?

- I would assume the ( N3100 ) crossover would need some tweaking . This hybrid driver combo will likely have a response curve ( just guessing ) that has less lower mid response and more HF response than a stock 2426h. ( See Ziches crossover studies )

- I would guess the hybrid will require a reworking of at least some values within the crossovers hipass section. Again, see Zilches excellent graphs of the two crossovers voltage drives for my reasoning .

- The hipass section of the "mkII network" was obviously reworked to accomodate for a differing of the responses between the two driver types

"Overall" Same sensitivity ?

- I doubt it . See the above and look at Zilches voltage drive graphs . Also, note that the rework of the S3100 to the S3100 mkII allowed for a 1 db net increase in "system" efficiency ( this info is from the technical cut sheets ). The values of the damping resistors in the LF were raised ( in the mkII ) effectively burning off a little less energy. I assume this coupled with the rework of the hipass section allowed for the newer ( higher ) system rating .

If that were the case it would be a simple way to go, assuming I can find the diaphrams that is.

- Nothing is ever simple with this stuff.



ps ; Would I still try out this hybrid driver ? Yes , but then I'm always willing to tinker with stock networks .

[Bernard Wolf]

thanks ever-so-much Earl, much appreciated... although most of whats being recommended is out of my league. I think what I will do is try to get that single 275nd if the bidding does not go too high. From there I have a friend - not local unfortunately - who can help me to build a mkii network while I wait to find another nd. Sound like it will be a long term project, but I don't mind that. In the meantime I could at least find out if the nd diaphram will actually fit as a retrofit.. thats assuming I win that bid.

Will let you know what happens when the bidding stops

Bernard

[Earl K]

Hey Zilch,

,,,,(+useTHROAT 318793-001)

- I'd do it for you on S2600 horn, but that it comes without throat adapter.
- [Whatta b_ttl_ck!]
- Time out while I raise holy HELL with them....

Say,, did you have a conflab with JBL about this missing H2600 throat ?

And ?

<.

[Zilch]

1.5-inchers...

Use a 1" exit cd with a titanium diaphragm that has a coating of aquaplas.

That'd be 275ND replacement diaphragm in like 2425/6, no?

Others?