Polarity -- Gotta check it!

Dr. J

G - I just picked up a new toy called a Galaxy Cricket by Galaxy Audio. It has a polarity checker on it as well as various cord checking functions. I started going through my ENTIRE system starting with all the cords. I actually got through all of the cords and only TWO were wired wrong where somebody (most likely me) attempted to fix them. The #2 & #3 pins were reversed. Ok -- no problem I will just reverse those two. When I got to the power cords that have Neutrik connectors on them I just eye-balled them making sure they were a +1 & -1, +2 -2.....etc. When I got to my speakers I found that one horn on my monitors was reversed & BOTH horns on my Mains were reversed! I couldn't believe it. All this time I have been using this system and the friggin horns were reversed. I knew something was wrong with the monitors because they had this wierd \"outer space\" like sound to them. I just flipped the wires and the polarity checked out ok even though they come from the factory wired wrong. You were right -- you can't believe what the manufacturer states is right. We are Talking 3 out of 4 horns! The Cricket confirmed on my mid woofers and the subs what I already knew by using the 9 volt method. I even checked out my guitar cabs for correct polarity as well. What a cool device this thing is. My 24 channel snake was all good as well. So now I have a couple of questions. On my mixer (SR24-VLZ Mackie --- I know I know you love those things don't ya? ) The inputs and outputs showed Balanced and in polarity BUT my Aux's all checked out UNBALANCED in polarity. It states right on the mixer over the top of the Aux's -- Balanced / Unbalanced. So is it common for the Aux's to be actually UN-balanced but you can use a Balanced cable on them or is something not right with this board? All 6 Aux's are like this. The same scenario goes for my Power amps. I use XLR's on everything I can just because they lock in place better than a regular cord. I don't know how to really check the power amps because the outputs or the speaker cables coming out of the amps to the speakers are all TWO wire Speakons --- so they can't be balanced. I guess here I should just make sure the polarity is correct by hooking the whole system up. And my final evaluation was the DriveRack itself. I couldn't get any definitive answers checking that thing. The cricket kept giving me Red flashing lights when the switch was in the T-2 position AND the T-3 Position. If pin 2 is \"hot\" I would have gotten a green light in the T-2 position. If pin 3 was cold then I would have gotten a red light in the T-3 position. I am only getting Red lights. Any advice on this? One last thing -- I haven't hooked the whole system up yet so I know that I still have to check to see if the polarity is consistent through the ENTIRE PA from the microphone to the positive outward motion on the speaker.

Dennis

If only one out of several monitors had a polarity reversed horn, it was probably a wiring mistake. If you only have 2 main cabinets and the horn was reversed on both, it is probably intentional. The manufacturer will reverse polarity if it gets them closer to alignment between the horn and the woofer (or mid). Whether it sounds better or not is another question.

Dennis

Dr. J

Thanks Dennis. Well my cabs are anything but stock. All of the woofers and horns have been replaced on these things. My horn drivers are from emminence. Anyway something got reversed somewhere at sometime. It is just good to know that my polarity checker worked like a charm. I checked the exact position of the horns with respect to where the mid driver sits. They are dang near perfectly aligned with each other from where the diaphragms are at. The only time delay factor I see here would be the \"Inherent internal\" delay that the LR 24 exhibits. Don't remember which gets delayed......Is it the horn to the mid or is it the Mid to the horn? I think the horn is the one that gets the delay put on it with respect to the horn. Gadget....... Dra??

Gadget

Hey Doc...
On page 28 of the manual the block diagram shows a quasi~balanced config, I assume will allow the use of either a balanced or unbalanced config...the diagram shows a resistor isolated ground in this case.. so ya it's particular to this mixer... and typical of the Mackie CRAP but I digress...

As for your \"highly modified\" speakers... I got a kick out of your
\"I just flipped the wires and the polarity checked out ok even though they come from the factory wired wrong. \"...well...I wish you'd straiten this out :roll: sorry... but ya, we ran into SRX 722 with different drivers right out of the box :oops: SHAME ON YOU JBL! I've run into speakers wired wrong from MOST mfgrs...and now that things come from off shore mostly :roll: caveat emptor...

The Driverack does A/D conversion and once onside the unit it's all digital so I'm not surprised that you cant polarity check that...

Dr. J

G -- Do you think flipping the wires was the right thing to do? I have no other way to know without opening up the horn drivers and try to visually see if there is forward motion with a positive charge. Yeah -- this is all based on the fact that the Cricket is wired right. Well -- I hope they took the time to wire the thing right. If they didn't then who the heck can you trust........ I'm pretty sure it is good since every test I did with the 9-volt I got the same result with the cricket. Hey are the Aux's supposed to be \"Balanced\" as well? Or at least on a good board? G- any thoughts on my previous post above on delaying the tops to the mids or vice versus with the LR 24?

Dennis

I assume your Cricket is a two piece unit.........a \"send \" unit and a \"receive\" unit. The receive unit will respond to a 9V battery pop just as well as a \"send unit pop\". Battery pop a midrange speaker and watch the motion of the cone as well as looking for a receive unit green light. That will tell you the Cricket is in polarity. There will be a bit of a learning curve with subs. They can give false readings.

Dennis

Dr. J

Yes the Cricket is a Two piece device with a send and a receive. One of the devices sends a positive pulse and drives the speaker while the other device has an external mic on it that picks up the pulse sent if you hold out in front of the speaker about 2-3\" and detects wether or not the cone or horn diaphragm is moving in the positive outward direction. Thanks Dennis!

Gadget

Actually I bet the unit is based on the one I have which actually sends out a positive pulse, then a negative pulse...if the receiver senses negative..then positive it reports reverse polarity...so as for the speakers...

What speakers are they anyway...went to look but... too busy..

I would say that unless they are JBL... then yes believe the pulser...JBL reverse wires some drivers...go figure...As Dennis points out some crossovers DO skew the phase so far that reverse wiring the driver is incorporated... but those are very complex ones and seldom if ever used in livesound speakers...

Take a look at the schematic and see if the negative and ground are separate feeds from the op amp... or just a resistor between the two... I'll look later.. Right now I'm super busy bringing my \"genius\" to the world of high end remodeling...

Sorry.. meant to address that but again... genius...
remember :shock: It's the nature of the beast that there is delay in all elements... The posted delay is to the tops with respect to the subs, (tops delayed but alas... I have begun to suspect that there is delay within delay, on my monitors the overall \" delay sits @ about 6.2-7.2 ms depending on the processor...and then there is an additional 4... ms applied to the 12\" woofer, and I suspect if the delay was fine enough that there would be a short delay on the horn as well... nothing scientific... but it just SOUNDS better :roll:
Gotta fly..
be well!

Dr. J

No problem G -- Thanks. The Mid speakers in this cabinet have 2032H stamped right on them. The JBL site lists them as a 15\" 8 ohm speaker and that is it. So they must be JBL's. When I use a 9 volt on them -- I get a positive outward motion on the speaker. I think they are ok. Same for my subs. The horn drivers are Eminence PSD 2002. They are the ones that were giving me a reversed signal. I think I will check the polarity of the whole system when I set it up next time. If I can verify that from the microphone THRU the system to the speaker produces a positive outward motion on the speakers -- then I guess I will be set.

Dennis

I have run into quite a few low to mid price speakers with reverse polarity horns but I will admit, JBL is a prime example. I was working with an old SR4725A; 15\" plus reverse polarity 2\" horn. When I checked out response on SMAART, it indeed \"looked\" better and flatter on the Magnitude screen while reversed, but vocal intelligibility improved a bit when the wiring was \"corrected\". The final test has to be your ears.

Believe your Cricket. It is working perfectly fine. If you get inconsistant readings on subs, temporarily increase your low crossover point to 200 or 300Hz, do the test and then restore the correct XO point. For more complex tests, this could create a problem but for Cricket tests it will work fine.

Dennis

Dra

I recall that Yorkville's older Elite EX2000 (2x15, 2\" exit horn and bullet tweet) had the 15's wired \"backwards\" because of cross-over phase issues.

Definately do some tests to see how things sound. Monitors on the other hand CAN benefit being out of phase to reduce feedback (in the right setting). Many monitor boards have phase inverters on every channel.

DRA

Dr. J

Will Do... Thanks Dennis! Thanks Dra! Wait -- Is phase going to be the same as polarity? I know Polarity is an \"Absolute\" it is either IN or OUT. I'm trying to understand why you would purposely want a speaker to have an INWARD action over an Outward action. Hmm not sure on that one BUT I do understand the phase thing when you get speakers a certain distance away from each other that the waves themselves get out of balance which makes the speakers sound out of phase. Kind of like the whole Boundary topic listed here in the FAQ section. I would think that you would want the POLARITY to be absolute and then phase be corrected by keeping your speakers placed the right way in a particular venue..... Don't know guys -- I'm just a Chiropractor trying to help Good sound NOT be an accident!!

Dr. J

Ok -- This is the way I understand this. I have had some physics a while back and I know that POLARITY is an absolute. It is either IN or OUT at all distances and at all times. When the Distances get offset between two signals (Even though they are moving in the same direction) there begins PHASE issues. The inherent delay in the LR24 filter could put A stack of speakers out of phase with each other although they are in perfect positive Polarity. Goes the same for Horns, mids and subs all being at different positions in their cabinets where the diaphragms aren't lined up. That would be phase issues just between the speakers in ONE stack. That alone to me is why it would be important to time align the stacks. They would be in perfect Polarity and Phase. Then if you take into consideration the topic on Boundaries (Like in the FAQ) where each Separate PA stack are at different lengths appart from each other -- then you may get into phase issues because of what the ROOM is doing to your perfectly in Phase and positive polar stacks.... Anyway -- this is the way I see it but I am an eager learner so let me have it! :shock:

Dennis

Check this out

http://mixguides.com/studiodesign/basics/understanding-phase-sound-1001/

Dennis

Dr. J

Great article Dennis. Thanks! So polarity and phase ARE two different things. Phase is a lot like delay. I think these words get thrown around a lot as being the same. So if your speakers are out of phase it doesn't mean that the polarity is inverted. It just means that the phase is off. Right now I know my system is in perfect positive polarity. From the microphones to the board through ALL of the gear & out to the speakers --making the speakers move in an outward motion. Now wether or not it is in phase -- I doubt it. I haven't time aligned the cabinets yet. Doesn't the distance you place the speakers apart cause phase issues as well? I just don't want to think or want other people to think that if the system is out of phase -- then you gotta get in there and FLIP the wires and it will be all good. Wow -- This is cool stuff but I think I am getting a headache! Dennis -- how do you deal with phase issues with a live sound system? Is it all in creative speaker placement? Is that the best way to deal with it by moving a stack \"a foot closer to each other or a foot apart, back, forward, stay away from the wall....etc. I will assume everything else has already been time delayed.

Gadget

You will ALWAYS have phase issues...and it keeps changing...that's the real paradox here...the best can hope for is to get it close and monitor it ... there is way more going on here than meets the eye :idea: and this axiom holds true :

The more you learn the LESS you KNOW!

Don't beat yourself up about it... next we need to start looking at issues like Impulse response, Transfer function, and THEN we can start to deal with Phase response...and Polar response...

Remember...it's all about the learning curve...and this ones a STEEP mother...

have fun... I'll send you a program...

G

Dr. J

Thanks Gadget! It is funny that you stated that because I remember you saying that in many posts. \"The more you learn the less you know\". Good stuff here!!!

Dennis

I depend a lot on various computer programs. A program such as EASE can be used to design or adapt a speaker system to a room. You will be able to see where cancellations will happen and reposition virtual speakers instead of 200lb speakers. With a program like SMAART, you will be able to time align speaker cabinets and also fine tune your system in a venue.

Dennis

Dr. J

Dennis -- do you find that the Smaart unit shows that the LR24 filter has an \"Inherent delay\" in it with respect to delaying the horns to the mids? There is a thread here on that topic. I was just wondering if you noticed the same thing. Thanks!

Dennis

I believe it might be more correct to say the LR24 causes a phase shift resulting in delay. Check this thread at Prosoundweb......
http://srforums.prosoundweb.com/index.php/m/271190/0/?srch=phase+shift#msg_271190

Dennis

Dennis

I guess I didn't really answer your question. SMAART will show all issues with the phase response of your speaker(s). It is the operator's responsibility to interpret the results and determine the cause of each issue.

Dennis

Gadget

You might want to add that SMAART doesn't teach itself...It's got a steep learning curve...

Dennis

Yes, I would want to add that. And regarding SMAART, \"The more you learn the LESS you KNOW!\"

Dennis

Dr. J

Thanks Guys! Great discussion for me. Looks like I need to take the system out and work with it some more. Got some new Fane subs being built right now so I will have to include them in my endeavor to tune it up. The Audix TR40 is backordered until late May & early June. Is there a large demand for those now or what is the deal. I can't find anyone that has them. All I have to use for now is the Behringer RTA that cost a whopping $49. I found an Earthworks M30 on ebay for $230 for a matched pair but my buddy told me they weren't used for RTA Measurements. I later found out that it would have been ideal!! Better luck next time. Have a great Saturday guys! I'm heading for a little fun today.....