Speakerplans.com Homepage
Forum Home Forum Home > General > Newbie Discussion
  New Posts New Posts RSS Feed - Phase in JBL dual 18”
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Phase in JBL dual 18”

 Post Reply Post Reply Page  12>
Author
Message
serioussound View Drop Down
Registered User
Registered User


Joined: 01 December 2013
Status: Offline
Points: 443
Post Options Post Options   Thanks (0) Thanks(0)   Quote serioussound Quote  Post ReplyReply Direct Link To This Post Topic: Phase in JBL dual 18”
    Posted: 17 April 2019 at 10:44am
I have a pair of JBL 2241H dual 18”.

1 driver was bad so I changed it.

After changed it I was so confused since 1 cab sound pretty much nothing compared to the other cab which gave nice full bass.

I then realised I wired the new driver out of phase. (Damn JBL color marking) Please help why was this effecting the sound so brutally much?



Back to Top
toastyghost View Drop Down
The 10,000 Points Club
The 10,000 Points Club
Avatar

Joined: 09 January 2007
Location: Manchester
Status: Offline
Points: 10920
Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2019 at 10:59am
180 degrees of phase rotation equals full cancellation.

https://www.youtube.com/watch?v=iIjPJERQnnw
Back to Top
Tonskulus View Drop Down
Registered User
Registered User


Joined: 15 September 2017
Location: Finland
Status: Offline
Points: 425
Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2019 at 12:11pm
Think about car and two equally strong persons trying to move it by pulling or pushing.

180 degree phase cancellation:  one person is pulling and another one pushing at the same side. Car is not moving at all, no work is done no matter how hard they are trying.

0 degree phase cancellation:  Both persons are pushing OR pulling at same time - now the car is moving by power of two persons.
 



Edited by Tonskulus - 17 April 2019 at 12:14pm
Back to Top
studio45 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 16 October 2007
Location: United Kingdom
Status: Offline
Points: 3863
Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2019 at 2:01pm
One was suckin' while the other was blowin' - so no pressure resulting...
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
Back to Top
serioussound View Drop Down
Registered User
Registered User


Joined: 01 December 2013
Status: Offline
Points: 443
Post Options Post Options   Thanks (0) Thanks(0)   Quote serioussound Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2019 at 2:31pm
I see never tested this before but it was crazy before I realised it ..
Back to Top
bob4 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 29 February 2004
Location: Finland/Germany
Status: Offline
Points: 1842
Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2019 at 4:09pm
Aaaaargh......... Why does everyone use wrong and outdated terminology? It is an issue of reversed POLARITY!

Don't perpetuate incorrect and sloppy terminology!
Back to Top
studio45 View Drop Down
Old Croc
Old Croc
Avatar

Joined: 16 October 2007
Location: United Kingdom
Status: Offline
Points: 3863
Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2019 at 2:02pm
If you walk up to a system - especially a bespoke build - and there's not as much bass as you were expecting, it's the No 1 thing to check. Usually the culprit is a short XLR link in the amp rack that should have been labelled as a polarity reverser, but isn't... or a Speakon link that the work-experience guy made.
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
Back to Top
Boxes-R-Blue View Drop Down
Registered User
Registered User
Avatar

Joined: 11 December 2018
Status: Offline
Points: 147
Post Options Post Options   Thanks (0) Thanks(0)   Quote Boxes-R-Blue Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2019 at 2:53am
Also, just for shits and giggles be aware JBL tend to run Red Back, black forward, IE the DEAD opposite polarity/phase/motor aspect to any other manufacture so you kinda need a Phase Popper to check the box is in line with the rest of your rig...
Back to Top
partya View Drop Down
Registered User
Registered User


Joined: 06 September 2013
Location: New Zealand
Status: Offline
Points: 105
Post Options Post Options   Thanks (0) Thanks(0)   Quote partya Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2019 at 5:06am
JBL standardised their polarity conventions in the early 90's, here is an older link to a list of positive / negative transducers --


Cheers
Turn it up! Turn what up?
Back to Top
Robbo View Drop Down
Old Croc
Old Croc


Joined: 05 December 2005
Location: Shropshire
Status: Offline
Points: 4221
Post Options Post Options   Thanks (0) Thanks(0)   Quote Robbo Quote  Post ReplyReply Direct Link To This Post Posted: 24 April 2019 at 4:19pm
This caused us loads of problems in the early 1970s when we used to hire in extra bass and mid cabinets to augment our own systems on some of the larger tours--I can remember crawling inside Martin 115 horns to feel which way the cone was moving when another crew member applied a 9v battery to a plugged in adaptor lead that we used for phase checking.
Back in those days a lot of companies including ours used a mix of JBL and Gauss in both bass and mid cabinets so from that day, I have always double checked drivers with a battery to ensure matched phasing---JBL reconed drivers were a common problem and very often moved in the wrong direction when non genuine kits were fitted.
I bet there are loads ofJBL HF drivers being used out there in the field that are fitted with copy diaphragms that are wrongly phased and no-one has ever noticed it.
Back to Top
madboffin View Drop Down
Old Croc
Old Croc


Joined: 03 July 2009
Location: Milton Keynes
Status: Offline
Points: 1537
Post Options Post Options   Thanks (0) Thanks(0)   Quote madboffin Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2019 at 12:14am
For some obscure reason, JBL driver magnets were the opposite way round to everyone else's, hence the nonconformist polarity.

If you put a JBL next to another manufacturer's driver on the bench (same way up), it was a bad idea to get your fingers between the two!


Back to Top
mojofilters View Drop Down
Registered User
Registered User
Avatar

Joined: 13 January 2018
Location: Tyne and Wear
Status: Offline
Points: 19
Post Options Post Options   Thanks (0) Thanks(0)   Quote mojofilters Quote  Post ReplyReply Direct Link To This Post Posted: 25 April 2019 at 12:07pm
Is it true that the old JBL polarity inversion standard was intended to mitigate potential damage from the cone moving forwards, if an amp getting turned on produced sufficient movement?

I was never sure if that was the audio equivalent of an old wives tale, or actually a pertinent problem back when such drivers were used with much less sophisticated amps etc?

If it was correct, wouldn't backwards cone movement of equivalent force potentially cause another type of damage?
Back to Top
 Post Reply Post Reply Page  12>

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2023 Web Wiz Ltd.

This page was generated in 0.207 seconds.