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Old 19th May 2006, 09:15 AM   #1
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Default subwoofer polarity reverse

good morning dear friends
i have purchased dynaudio sub 250 ie 10"200w rms subwoofer,immediatly after reaching home i opend it with intrest .while opening i didnt observe the polariy of the driver.
while boxing it up i found that there is no indication on the driver of the polarity.one black(-) and one red wire(+) coming from plate amp.i am very much confused,as there is no indication on the woofer.both connecters are exactly same.
any body please advise me how to find correct polariy of the driver.
what happens if i wrongly connect it?
waiting for ur valuable reply
thanking you
bye
srinivas.
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Old 19th May 2006, 09:57 AM   #2
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Some Dynaudio drivers have the + designation on the sticker that tells the model name and which is attached to the magnet.

If the polarity is wrong you might end up with a dip or hump in the frequency response at the crossower frequency between the main speakers and the sub.
Maybe you sub has got a polarity switch anyway since the best polarity is often a thing that has to be tried out by listening or measuring.

Regards

Charles
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Old 19th May 2006, 10:38 AM   #3
Bobken is offline Bobken  United Kingdom
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Hi,

You can safely check the driver's polarity with a small battery.

Use something like a single cell torch battery (i.e. just a volt or so, not a high voltage type) and briefly connect it across the two speaker terminals.

The cone will move either in or out and when it moves outwards (forwards), the positive battery connection will also be the positive connection of the speaker.
If on the first trial the cone moves inwards, just reverse the battery to be sure of this. Make these tests with the connections from the plate amp disconnected, of course.

I hope this helps.

Regards,
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Old 19th May 2006, 11:10 AM   #4
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Here's a FYI you can use to double check your findings against.

With the speaker face down and the input leads facing you, 95% of the time the + terminal is on the right. I have only ever come across maybe 2 or 3 speakers that had it the other way around.
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Old 20th May 2006, 05:44 AM   #5
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Default CLARIFICATION ON POLARITY

Dear friends
Thanks a lot for ur positive reply.
I checked both the battery method and right side positive method and I found both are giving opposite results to each other!with sub ,but gave me accurate with my jamo center speaker.
Any how thanks a lot for ur information, if u provide any additional information I am very much thankful
srinivas
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Old 20th May 2006, 10:14 AM   #6
Bobken is offline Bobken  United Kingdom
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Hi,

I don't wish to unduly criticise the advice of theAnonymous1, but if his rule of thumb works, it is more by luck than through any accepted 'convention'. Although I am sure he means well with his comments, it appears that on this occasion it has added some confusion to an otherwise very straightforward matter.

Speaker makers can and do choose for themselves how they 'allocate' these terminals, and although out of quite a few different units I have just checked, the majority are as suggested by Anon., they are not *all* deliberately made in this configuration.

You can *absolutely rely* on the suggested battery method, as when you are applying a positive DC voltage 'pulse' to the correct + driver terminal, the cone should move outwards, or forwards, to also give a positive sound 'pulse'. This is a fundamental design feature of these drivers.

You only need to touch the battery on the speaker terminals for a second, whereupon the cone should quite obviously move in, or out, depending on which way the battery is connected. It is very clear to see this effect on woofers with large extensions like you have here, and I have never had any difficulty with checking any mid-range drivers by this means, either.
However, there is often so little cone/dome movement with many HF tweeters that it is not always easy to see which way the cone moves without some magnification.

Don't be tempted to use much higher voltages with tweeters to exaggerate this movement, though, as you could cause them some damage through 'over-extending' their suspensions. They also have much less robust voice-coils, and will not be happy to take long-term DC voltages, as this can overheat these flimsy coils and distort them, or even burn them out eventually.

Most people will have a torch battery to hand or perhaps a single cell taken out of a remote-control to use for this purpose, and their nominal 1.5-ish volts will be quite safe for checking any conventional coil/diaphragm drivers, if the voltage is not applied for very long.

Regards,
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Old 20th May 2006, 11:18 AM   #7
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thanks bob,thanku very much for ur knowledgeful information,yester day i checked exactly with a remote battery ie 1.5v aa size small batery and i have seen the cone movement very clearly, thats sorted out my doubt.
if u dont mind please tell me what happens if we reverse the polarity?
because by the above said method i find the positve terminal of woofer and assembled the sub .now i have connected my player LR outs to the sub/sat inputs and set cross over to 80hz of the dyn sub and found that my sub is moving for very easily ie it is moving even for silly sounds also and giving me zarring sound ie heavy cone movement,even i kept the gain of sub just a little bit.
now i reverse the polarity and found that cone movemet is less and there is no zarring.
please advise what i have to do inorder to avoid jarring?
bye the bye i am using B&W DM320 as main and JAMO CENTRE18 as centre and MOURDANT SHORT MUSIC 10 i as surrundings and HARMAN KARDAN AVR 65 as amplifer.
waiting for reply
bye
srinivas
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Old 20th May 2006, 12:56 PM   #8
Bobken is offline Bobken  United Kingdom
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Hi,

The quick and easy answer here is that you get a 'suck' instead of a 'blow' when the cone moves if the relative connections are reversed!

Some people (and I am one of them) can immediately hear the difference on certain recordings when this phase is out by 180 degrees. However, on many recordings where individual instruments are recorded using separate mics, it is often a mix up of true phase, and then it is a toss-up as to which way will sound better.

A simple test for this (often-called 'absolute phase') is just to reverse *both* speaker connections on your main speakers (leave off the subs for this trial) and listen preferably to a close-miked vocal rendition, and you may well hear the difference.

When the phase is correct, I hear everything marginally clearer, which gives the impression of also being slightly louder, and voices and instruments are better defined. Most people who hear this say it easier to hear on bass notes, but I hear it just the same on mid-range drivers, too.

This subject has been discussed for years, and many still hold that there is no difference, but, as far as I am concerned, they are wrong. There is most definitiely a sonic difference, but on less good systems, and with badly 'phased' recordings etc., I accept that it cannot often be heard.
Some high-end UK speaker makers are paying much more attention to this subject recently, which can only be a good thing, as several (most?) multi-driver speakers have one of the drivers deliberately 'reversed' in phase, to make the crossover easier to implement, and this tends to make such issues even more complex.

If you imagine an 'ideal' case where everything has been controlled to ensure that the nominal phase is correct throughout the entire recording and replay chain, it may help to understand this topic. Assuming the recording is of a kick drum, and the mic is placed in front of this when recording, when it is hit (from behind the drum) with the pedal, the drum skin moves forwards and exerts a positive pressure or wavefront which radiates towards the listener. This will have an affect on the listener's ear drum (as a pressure, initially) and this will be slightly different subjectively to the listener than if it was a low-pressure event.

In order to replicate this positive wave-front as accurately as possible, the speaker's diaphragm should also move forwards towards the listener, but if something in the chain is 'reversed', the speaker's cone will initially move backwards (more like a suck, not a blow) which causes a rarifaction in the wave, as it is 180 Deg. out of phase as it first reaches the listener's ears.

Both ways make a sound which it must be said is very similar, but subjectively, and to those who can hear this effect, the 'correct' way is just more natural-sounding. There is a lot more to the subject than this brief explanation, as many other matters can affect phase issues to some degree or other, but if one starts off with it being completely reversed, in my experience, it will never sound quite as natural as it could.

As for your problem when the speakers are connected 'correctly' I regret to say that I don't have any explanation, but I will think about the matter some more. Theoretically, I can see no real differences here, as (apart from this initial 'sound-front' when a note commences) after this, the continuing 'note' is composed of a mixture of (AC) sine waves, which I think should affect the driver much the same, either way. All that is then happening is that the cone is vibrating (moving in and out) while a note is being sustained, and whether it *begins* as a push out on the cone, or the other way around, shouldn't (as far as I know) make any difference here.

However, I don't doubt what you say regarding this difference, but the kind of cone-movement you refer to (if I understand you correctly) appears to me more like a lack of overall damping in the speaker/amp combination, or, perhaps if you are listening to LPs (not CDs) there is some 'rumble' or LF 'vinyl roar' from the TT, which is well known to cause excessive cone-flapping.
I don't know how close your subs are to the main speakers, and I wonder if one is somehow affecting the other in some way. Perhaps the pressure waves from the main speakers could be exerting a force on the sub's cones and partly cancelling the movement of the sub's cones under some circumstances, although I have not heard of this before. Maybe you could check this by merely running the subs alone, and see if this has any affect.

If I think of anything useful, I will post again.

Regards,
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Old 20th May 2006, 03:10 PM   #9
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Quote:
Originally posted by Bobken

In order to replicate this positive wave-front as accurately as possible, the speaker's diaphragm should also move forwards towards the listener, but if something in the chain is 'reversed', the speaker's cone will initially move backwards (more like a suck, not a blow) which causes a rarifaction in the wave, as it is 180 Deg. out of phase as it first reaches the listener's ears.

Actually it is the other way around, meaning that you need to reverse it along the chain to make the microphonediagaphm moving inwards to be a conemovement outwards.
Sorry, have forgotten where that shift should take place but IIRC it is somewhere in the mixingdesk.

Kick are most often miced from the public front but sometimes also from the drumguys front, which requires a shift on one of the mics if both are used together.
Snare are usually miced from the upside (With Hihat bleeding into it) but also from the bottomside sometimes.
Tomtoms usually are miced from the upside only which gives them a initial suck, which drummers that sits on the suckside finds most natural.

Sorry, forgot to mention that nowadays gating is more or less standard on drums.
And the gate opening is delayed which also may affect if it is a suck or blow at the attack, depending on the time that is used.
(I dont use gates myself)
A Gate
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Old 20th May 2006, 04:05 PM   #10
Bobken is offline Bobken  United Kingdom
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[QUOTE]Originally posted by electroaudio
[B]


Actually it is the other way around, meaning that you need to reverse it along the chain to make the microphonediagaphm moving inwards to be a conemovement outwards.
Sorry, have forgotten where that shift should take place but IIRC it is somewhere in the mixingdesk.

Hi,

Sorry to disagree here, but what I said was quite correct in order to illustrate the point I made in relation to a kick drum, which was used as a simple example. I only used this example as it is more easy to visualise which way the drum skin moves in a case like this when first struck (this is forwards), and which way the speaker cone needs to move (also forwards) to replicate the same phase effect.

If you wish to experience the same aural sensation as if you were in the audience listening to an un-amplified kick drum being struck (i.e. the most natural sound) you need to do exactly what I said, assuming "an ideal case, where everything has been controlled to ensure that the nominal phase is correct throughout the entire recording and replay chain", as I also very carefully stated in relation to this comment.

A kick drum's skin is (normally) vertical and is propelled forward towards the audience (i.e. a positive wave) as the kick comes from within (or from the rear of) these particular drums, unlike others which are normally struck from the outside, inwards.
By the same token, if you wish to replicate this effect as closely as possible (as far as the same phase effect is concerned), the normally vertically-aligned cone of the speaker also needs to move forward towards the listener.

If you wish to complicate this issue, of course many mixers do all sorts of things with phase effects during and after recording sessions, as I also suggested, and some recordings are just a mix of different phases.
However, for the purpose of merely illustrating the effects of absolute and reversed phase, which was what this poster had asked about, I feel this is simply adding unnecessary confusion to this matter.
In fact I deliberately chose a kick drum for this example, as the skin does move out towards the audience (unless the drummer is facing backwards!) and this should be easy to visualise, whereas (almost) all other drums will be struck from the outside (or top) and the skin will probably be (mostly) almost horizontal, with the strike being mainly downwards in these cases.

Regards,
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