Question on N7000/N8000 XO

[ngccglp]

Hi,

May I know whether the N7000/N8000 XOs are meant for:

1. 16 ohm mid, 8 ohm high OR

2. 8 ohm mid, 8 ohm high OR

3. 16 ohm mid, 16 ohm high

Thanks.

[Roddyama]

It's been a long time since I've used them but my recollection is that these were sold for the JBL home components for crossing over to the 077 tweeter (this is how I used my N8000's). The home components were typically nominal 8ohm speakers.

[Zilch]

The mids are 16 and the UHFs are 8.

Everything is nominal.

If you "Search," you'll find what they actually are.... :thmbsup:

[Roddyama]

According to this sites catalog images for 1976 home components found here :
http://www.lansingheritage.org/images/jbl/catalogs/1976-comp/page7.jpg
both Zilch and I are correct.
Apperently, in '76 at least, the N7000 was designed to cross from the 375, 16ohm mid driver to the 8ohm 075 or 077 but the N8000 crossed from the LE175 or LE85 mid drivers which were both 8ohm. In both crossovers the input impedance is listed as 8ohm. I didn't look at some of the other years catalogs since this was the one I remembered having.

[ratitifb]

equations :

LE85 mid : 8ohms = 16ohms :blink:
+
home component (consumer/black paint) = pro (grey paint)
3105 = N7000
3106 = N8000

if i well remember ...

solution ?

make a search on this forum there are some posts regarding Xover frequency responses vs impedance load

[Earl K]

Re: 3105 network
------------------------------------------------------------------------
The 3105 (N7000) was optimized for the 2402 (075) or 2405 (077) and the 2440 (375).

The 3106 (N8000) was optimized for the 2402 (075) or 2405 (077) and the 2410 (LE175) or 2420 (LE85).


- Here's a raw "Z" plot from one of Zilch(s)' le85s ( not mounted to a horn ) .

http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=9682&stc=1&d=1124845134


LE85 Impedance plot, no horn.
------------------------------------------------------------------------
Call it 10 Ohms.

Fmin is 1214 Hz.


- 10 ohms , across most of the bandwidth looks correct for a lowpass filter / OTOH / in the area where this driver is most likely going to be highpassed ( & with those impedance peaks shifted lower by an attached horn load ) , one could easily choose 20 to 30 ohms ( or less of course ) .


:)

ps 1 : here's an example of the AC impedance ( spikes ) shifting downwards, caused by the loading of the attached horn ;

http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=10030&stc=1&d=1126855672

ps 2 : similar Z plot ( but different enough to warrant the post ) of a 2426J on H3100 ( ignore the 2226j label )

http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=10031&stc=1&d=1126855841

ps 3 :


- Here are impedance plots of 4 slot tweeters 2 are labeled 8 ohm and are alnico 077s and two are older 2405 alnicos labeled 16 ohms.
- All four drivers are in exceptional condition and have their original diaphragms and seals.
- As JBL technical literature states all of these drivers use the same diaphragms and therefore should have the same impedances.
- The differences seen in these plots shows a random sampling of these drivers exhibiting slight production differences.

Red 077 "8 ohm"
Purple 077 "8 ohm"
Green 2405 "16 ohm"
Blue 2405 "16 ohm"

http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=8985&stc=1&d=1121547524

ps 4 :
- Here are Giskards' voltage drives for both crossovers mentioned ( N7000 & N8000 ) .
- The comparitive V-drives were obtained using different dummy loads ( 8 or 16 ohms ).
- One can extrapolate for themselves what twin, 10 ohm loads would look like ( or for that matter , a mix of different impedance loads ) .

http://audioheritage.org/vbulletin/attachment.php?attachmentid=287&stc=1&d=1058062116

[Zilch]

equations :

LE85 mid : 8ohms = 16ohms :blink:
+
home component (consumer/black paint) = pro (grey paint)
3105 = N7000
3106 = N8000

if i well remember ...

solution ?

make a search on this forum there are some posts regarding Xover frequency responses vs impedance loadIndeed, the stated (and marked) impedance varied according to other factors as Earl has illustrated, but the impedances themselves have remained the same.... :)

[ngccglp]

Thanks guys.

[qcautosports]

Are the internal parts of the N7000 replaceable? Are there replacement parts readily available to freshen up the old cross over?