H frame reverse polarity question

0 Members and 1 Guest are viewing this topic. Read 475 times.

audiogurujax

  • Jr. Member
  • Posts: 130
H frame reverse polarity question
« on: 23 May 2018, 01:44 am »
As most of you know when you build a Multi woofer H fame the polarity of the woofers that are facing backwards needs to be inverted from the ones facing forward. my questions are:

  • First what is the benefit of facing half the woofers backwards instead of having all of them facing forward, therefore no need to reverse polarity on any of the woofers?
  • And second, isn't having a driver with inverted polarity create more distortion since drivers are not optimized to move in an inverted polarity?


Thanks

Chops

Re: H frame reverse polarity question
« Reply #1 on: 23 May 2018, 12:24 pm »
As most of you know when you build a Multi woofer H fame the polarity of the woofers that are facing backwards needs to be inverted from the ones facing forward. my questions are:

  • First what is the benefit of facing half the woofers backwards instead of having all of them facing forward, therefore no need to reverse polarity on any of the woofers?
  • And second, isn't having a driver with inverted polarity create more distortion since drivers are not optimized to move in an inverted polarity?


Thanks

1) Reversing one driver helps cancel out odd harmonics and/or distortion from the motor and suspension systems of both drivers.

2) Drivers work off of A/C, meaning the signal goes both ways. The driver doesn't care which way it's wired up polarity wise. A well made driver should move equally in both directions with a resting point dead center of the two peaks.

Danny Richie

  • Facilitator
  • Posts: 12085
    • http://www.gr-research.com
Re: H frame reverse polarity question
« Reply #2 on: 23 May 2018, 02:25 pm »
What he just said plus it balances out the weight.

You can face them either way and get the same great results.

But a few have tried them both ways and formed a preference. I look forward to some more comparisons myself.

Davey

  • Restricted
  • Posts: 1452
Re: H frame reverse polarity question
« Reply #3 on: 24 May 2018, 05:15 pm »
FYI, the inverted configuration of one driver minimizes even-order harmonic distortion, not odd-order distortion.  You could expect to see approximately a -15db reduction in second-order distortion by flipping one of the drivers.  You're reducing the asymmetry of the configuration by doing this, which inherently reduces even-order distortions.

Whether it sounds better or not, is up for debate.  :)

Dave.

Danny Richie

  • Facilitator
  • Posts: 12085
    • http://www.gr-research.com
Re: H frame reverse polarity question
« Reply #4 on: 24 May 2018, 07:48 pm »
In my experience a small variation in measured distortion levels in a given area rarely relate to what we hear in music playback, especially in ranges below 200Hz. However, how fast a driver can dissipate stored energy and return to rest is very significant. And these servo controlled woofers can do that like no other. 

Davey

  • Restricted
  • Posts: 1452
Re: H frame reverse polarity question
« Reply #5 on: 24 May 2018, 08:50 pm »
Yes indeed, but that's a different issue than was queried here.  The servo control on woofers so equipped can be working to absolute perfection, but it still won't address the asymmetrical radiation the typical driver has.  The only way to address that system issue (should you choose to) is to add a second driver with the opposite orientation.

Dave.

Captainhemo

Re: H frame reverse polarity question
« Reply #6 on: 26 May 2018, 10:38 pm »
I've done them both ways and if  I HAD to say  I likked  one orientation better, I'd  probably say the   all forward but  the differences are  marginal.  When I  first heard the  triples all  forward, I felt the bass were  a  touch cleaner with   a bit more slam.  However, since then,  I've  gone back to a  pair of opposed duals and have them    really dialed in.. not  sure  now it  can get  much better.


But a few have tried them both ways and formed a preference. I look forward to some more comparisons myself.

When you are   fully settled in,  glue up that  set of  all forward  triples we sent you    and give them a  try.  they'll be a  great match for your  Oticas    :thumb:

jay

Jonathon Janusz

  • Full Member
  • Posts: 746
Re: H frame reverse polarity question
« Reply #7 on: 27 May 2018, 01:50 am »
The servo control on woofers so equipped can be working to absolute perfection, but it still won't address the asymmetrical radiation the typical driver has.  The only way to address that system issue (should you choose to) is to add a second driver with the opposite orientation.

I know we are really splitting hairs here, but would this attribute inherent in typical drivers make one of these subs with all drivers facing front a system with a slightly cardioid radiation pattern (given that the depths of both sides of the H-frame are the same and everything else is equal and or symmetrical) rather than textbook dipole pattern?  This would account for the perceived increase in bass energy Jay reported in difference between the two setups as this setup would then fire just a wee bit more forward than back with all drivers facing front? 

This then begs the question (for those OCD about the looks of the system, which is where I think the idea of facing all to the front started way back when?), could one reduce the cavity depth at the front ever so slightly to decrease/reshape the output from an all drivers front facing arrangement to restore the driver radiation pattern to that of a reversed driver setup, more representative of a textbook symmetrical dipole, thus giving those who like the all drivers front look the best of both worlds?

Also, if one were trying to maintain the nth-degree of symmetry in the radiation pattern, wouldn't one need to make these subs in multiples of two drivers per stack, as a triple would only be able to reverse one of three drivers and thus still end up with a similar situation to a dual with both facing front where the output to the back is less than that out the front?

Again, please, for any reading don't think that I'm trying to contrive some sort of "night and day" kind of discussion out of the asking; this really is splitting fine hairs on what is still arguably (IMHO) one of if not the bass system audiophiles can put in their homes by which all others should be compared.  :thumb:

Danny Richie

  • Facilitator
  • Posts: 12085
    • http://www.gr-research.com
Re: H frame reverse polarity question
« Reply #8 on: 27 May 2018, 02:49 pm »
Jonathon, there is an even bigger variable that is the room. Positioning of the woofers, toe in, and room reflections can over ride the little stuff real easily. 

Jonathon Janusz

  • Full Member
  • Posts: 746
Re: H frame reverse polarity question
« Reply #9 on: 27 May 2018, 03:18 pm »
Jonathon, there is an even bigger variable that is the room. Positioning of the woofers, toe in, and room reflections can over ride the little stuff real easily.

Danny, I hear you.  If then for no other reason than for sake of discussion and satisfy curiosity, how about the above if we were looking at these speakers in an anechoic chamber or outdoors, isolating just what the speaker is doing and nothing else?

Thanks for your time!

Jon