PDA

View Full Version : What is the polarity supposed to be on an 077 tweeter?



Alobar
12-03-2015, 06:04 PM
Sorry to have to ask this but they say the only stupid question is one that's not asked and being a total noob I am a little unsure of myself. I just got the items together (L-pad and 1uF cap) to hook up my 077's to my L200's. I keep seeing on several schematics showing the pos hooking up to the neg on the tweeter. Is this the case? I know that JBL has done this at times..

http://i1112.photobucket.com/albums/k500/eaglesnest_1412/Capture_zpsbqyq1kr0.jpg (http://s1112.photobucket.com/user/eaglesnest_1412/media/Capture_zpsbqyq1kr0.jpg.html)

JeffW
12-03-2015, 08:05 PM
Probably depends on the crossover. It's not uncommon for 12dB slope crossovers, for example, to have adjacent drivers with flipped polarity to keep them in phase at crossover. The diaphragm on the 077 will have a dot next to the negative lead, that'll go to the black binding post. If you're unsure of the crossover design, you'd probably want to measure the mid/tweeter response to see if there's a big hole at crossover. If so, something's probably backwards.

The polarity of JBL crossovers/drivers can get extremely frustrating to decipher - there have been huge threads on it here. Measure it if in doubt, I bet there are a lot of JBL systems out there where guys have pulled drivers without noting what wire goes where and then get them hooked up wrong after a refoam or something.

1audiohack
12-03-2015, 08:22 PM
Hi Alobar;

I am not quite sure what you are asking. The absolute polarity of the 077 if it is properly assembled with a JBL diaphragm is forward motion with positive applied to black.

Which way it integrates best with a passive network is always up for debate.

Barry.

Alobar
12-03-2015, 08:43 PM
Probably depends on the crossover. It's not uncommon for 12dB slope crossovers, for example, to have adjacent drivers with flipped polarity to keep them in phase at crossover. The diaphragm on the 077 will have a dot next to the negative lead, that'll go to the black binding post. If you're unsure of the crossover design, you'd probably want to measure the mid/tweeter response to see if there's a big hole at crossover. If so, something's probably backwards.

The polarity of JBL crossovers/drivers can get extremely frustrating to decipher - there have been huge threads on it here. Measure it if in doubt, I bet there are a lot of JBL systems out there where guys have pulled drivers without noting what wire goes where and then get them hooked up wrong after a refoam or something. Thanks, I am currently running the 077's without an actual crossover, just a 1uF cap and an 8 ohm Lpad. Right now I have them pos to pos from the amp and the L200's are sounding so much better than before!


Hi Alobar;

I am not quite sure what you are asking. The absolute polarity of the 077 if it is properly assembled with a JBL diaphragm is forward motion with positive applied to black.

Which way it integrates best with a passive network is always up for debate.

Barry. as mentioned above, no crossover as the horn in these 200's tend to roll off anyway, at least that is how it was explained to me. I took these tweeters out of my L65's which from past experience with those seemed to be hooked up backwards with the woofers. Maybe the tweeters were the same way.
So because there is no actual network now how can one tell which way these connect other than by listening?

1audiohack
12-03-2015, 10:09 PM
I didn't see that Jeff had already posted, sorry Jeff.

I believe that theory takes the back seat to measurement and if that isn't available you go by ear. If a polarity flip isn't apparent by ear, then your golden either way. This really is possible that if you are near + or - 90 degree out of phase, switching polarity can be inaudible.

Barry.

Alobar
12-03-2015, 11:39 PM
I didn't see that Jeff had already posted, sorry Jeff.

I believe that theory takes the back seat to measurement and if that isn't available you go by ear. If a polarity flip isn't apparent by ear, then your golden either way. This really is possible that if you are near + or - 90 degree out of phase, switching polarity can be inaudible.

Barry.
Thanks Barry, I'll give my 60 yo ears a try to see if I can tell the difference in the next few weeks before I go to installing them into my L200's. Really pleased with how it sounds now so I suppose that's all that counts. :bouncy:

Mr. Widget
12-04-2015, 08:42 AM
Probably depends on the crossover. It's not uncommon for 12dB slope crossovers, for example, to have adjacent drivers with flipped polarity to keep them in phase at crossover.Yep, and as Barry said, feel free to experiment and just listen.

A single cap is a 1st order Butterworth crossover with a 6dB/octave slope. It will change the phase by 90. A second order crossover (an appropriate cap and coil) will give you a 12dB/octave slope which is 180 out of phase, and adding each additional section will increase the slope and continue to change the phase. A 24dB LR crossover is back in phase.

This is all great theory and does matter, but unless you are into heavy DIY land, just use your ears and in general there are no wrong answers if you're happy with the results.


Widget

Alobar
12-04-2015, 09:54 AM
Yep, and as Barry said, feel free to experiment and just listen.

A single cap is a 1st order Butterworth crossover with a 6dB/octave slope. It will change the phase by 90. A second order crossover (an appropriate cap and coil) will give you a 12dB/octave slope which is 180 out of phase, and adding each additional section will increase the slope and continue to change the phase. A 24dB LR crossover is back in phase.

This is all great theory and does matter, but unless you are into heavy DIY land, just use your ears and in general there are no wrong answers if you're happy with the results.


Widget
Thanks for the explanation, makes sense why these schematics would show a neg/pos connection. I have been doing a fair bit of reading on this site and am realizing that anything I thought I knew about speakers and crossovers I really don't know beans, but am starting to learn a few things anyway! The Butterworth xover is new and gives me something more to read up on. I live in a bubble here with almost zero chance to listen to anyone elses JBL's or anything for that matter. Thus I have nothing else to compare it to, but I do enjoy the music and can listen for hours!

By the way IMO the 077's have really made the 200's sound better, actually much better! I am waiting for the brackets to arrive from Lee in Montreal and then am going to a more permanent installation. My plan right now is to use the brackets to mount the tweeters on the front surface of the baffle, thus not drilling out the 3" hole (hate the idea of drilling out these speakers). There happens to be just enough room between the grille screen and the baffle to fit.

Here is my lashup so far, looking pretty tacky!
http://i1112.photobucket.com/albums/k500/eaglesnest_1412/0772_zpswu6xradl.jpg (http://s1112.photobucket.com/user/eaglesnest_1412/media/0772_zpswu6xradl.jpg.html)
http://i1112.photobucket.com/albums/k500/eaglesnest_1412/0771_zpsnzshgied.jpg (http://s1112.photobucket.com/user/eaglesnest_1412/media/0771_zpsnzshgied.jpg.html)