Request: AR-10pi Woofer Equalizer/Tranformer Info

[DaveTerry]

I know this is a stretch, but I'm hopeful that it won't go unanswered.

Does anyone know the specifics concerning the Hyde Transformer that AR used in the 10pi?

I haven't found anything, and I've done a lot of reading.

Thank you to who ever is able to help.

-Dave

[tysontom]

The auto-transformer in the AR-10π is used as a contour network for the woofer's output, specifically adjusting the output for π, 2π  or 4π placement in a room, or corner/floor, along the wall or out in the room away from corners.  The auto-transformer gives greater placement flexibility for the speaker so that it can produce "flat" energy into the various mounting configurations, rather than be restricted to 180-degrees mounting (against the wall).

--Tom Tyson

 

[DaveTerry]

Thank you for taking the time to respond Tom.

Perhaps I should rephrase my question about the Hyde Transformer/Autoformer used in the 10pi.

Is the transformer an Impedance matching transformer, is it a multi-tap step up transformer, or was it something custom made for AR and we can only guess and make assumptions?

I don't have one to test, and there isn't any published data on it that I can find. The patent for the circuit used in the 10pi doesn't give much insight unfortunately.

 

Thanks Again,

Dave Terry

[owlsplace]

So, Dave, are you thinking about doing a one-off 10 pi reproduction? I was curious whether that was feasible for the LST at one point but decided it was much easier, and less expensive, to just buy a set.

Otherwise you are looking at finding an original transformer, deconstructing it, and then hand-winding another one.

Roger

[Rlowe]

Hello David, this might Help:

 

[tysontom]

12 hours ago, DaveTerry said:

Thank you for taking the time to respond Tom.

Perhaps I should rephrase my question about the Hyde Transformer/Autoformer used in the 10pi.

Is the transformer an Impedance matching transformer, is it a multi-tap step up transformer, or was it something custom made for AR and we can only guess and make assumptions?

I don't have one to test, and there isn't any published data on it that I can find. The patent for the circuit used in the 10pi doesn't give much insight unfortunately.

 

Thanks Again,

Dave Terry

Dave,

The auto-transformer is part of the "Woofer Environmental Control" portion of the 10π's crossover, and it is a precision impedance-matching device, in conjunction with other crossover elements (the 10 has a full half-section, 12 dB/octave π crossover on all drivers) to alter the level of bass energy as appropriate for π, 2π or 4π room placement.  The transformer also alters the slope of the woofer's response to maintain flat output in the crossover region.  Some have asked why not just use an equalizer to do the same thing?  An EQ setup would certainly work, but it would not be more accurate, and it would be needlessly complicated and more expensive.  The auto-transformer also does not have any effect on transient response or phase shift, and most amplifiers could accommodate the impedance shifts.  However, a high-quality, stable and sufficiently powerful amplifier should always be used with the AR-10π.

When you place a speaker in a corner, along a wall or out in the open, the balance of midrange and treble stays relatively constant; however, the level of bass energy is affected—due to the very long wave lengths—by the position of the speaker in relation to the room.  The optimum position for these speakers would be 2π, or 180˚ solid angle (in a bookshelf or back against the wall but up off the floor), but it was felt that a lot of rooms would not accommodate this mounting position, and some speakers would have to be placed out from the wall or even directly in a corner, etc.  The 10π's auto-transformer "Woofer Environmental Control" compensated for the woofer's output to keep the optimum balance between bass and midrange/treble, regardless of speaker location in a room.  It worked, but it came at a $100 higher price than the otherwise equal AR-11.

—Tom Tyson

 

[DaveTerry]

Sorry it took so long to respond to you guys......too much other stuff going on.

First, I want to say thank you to Tom Tyson for the excellent technical information, and also to Roger for his insight.

My initial idea, was to try and determine if there is an Autoformer out there, new or old, that would compare to the Hyde transformer that AR used in the 10pi. After that, try to purchase one, or wait and watch the 'net for a 10pi crossover.

I'd like to use an AR10pi/AR11 woofer as a separate sub woofer, along the lines of the AR9 concept, supplementing my AR11's. 

The fun and interesting part will be to copy/modify the 10pi Woofer Equalizer, and not burn down my house lol.

[Steve F]

The 10Pi autotransformer would be unnecessary if you are going to construct a home-built powered subwoofer using AR-12-inch woofers. The 10Pi’s WEC was a simple level control that adjusted woofer output level for three different very generalized local environmental conditions. As you can see in the curves that Tom supplied, the woofer responses are exact parallels of each other—strictly level differences. There is no contouring, only level adjustment.

If your home-brew sub is powered, then a level adjustment will be available to you either via the sub amp’s volume control or the pre-amp’s or receiver’s “sub out” level control. All HT receivers/pre-pros have a sub-out level control; many stereo pre-amps do as well.

 

If you’re building some type of passive AR9 woofer section, then things are a bit more complicated in terms of system integration and a simple Pi, 2Pi, 4Pi adjustment for the sub may not be sufficient. You won’t know until you try, but my gut tells me that finer level adjustment—as well as frequency (crossover) adjustment—will be needed. Again, HT receiver/pre-pros and many ‘better’ stereo pre-amps have adjustable sub  x-o controls as well.

Steve F.

[DaveTerry]

Thank You for that very helpful info Steve F.

I'll keep it mind as an alternative project in the event the 10pi plan turns to scrambled eggs.

 

DaveTerry