AR-3a Improved tweeter wiring

[Stephen M]

Hi,

I'm a bit confused about the wiring of the tweeter in this schematic. It seems to me the +ve terminal of the tweeter should be connected to black, not yellow as shown below. I'm basing this on the fact that the woofer and midrange have -ve to ground, and so it logically follows that the tweeter should too. I'm also assuming the yellow dot on the tweeter terminal indicates +ve.

Am I wrong, or is the schematic? I suspect I'm wrong, but anyway....

Cheers

Stephen

 

 

 

 

 

[mike tarelli]

Hi Stephen,

With those two names on the schematic you can be sure it's correct. Certainly that's how mine are wired.

Mike

[Stephen M]

Hi Mike,

Thanks, I guess I should have asked a different question:

"Why is the tweeter wired differently to the other drivers? Why is tweeter +ve wired to the -ve side?"

 

[Stephen M]

I've also done a quick survey of other schematics posted here. In each case the tweeter is wired with the same polarity as the other drivers. I'm retuning to my initial question: Is it possible that the tweeter should be wired opposite to what is shown in the above schematic? 

[JKent]

Some speakers are designed with the tweeter polarity reversed. If you do a google search you can find several examples. There has been quite a bit of discussion in these pages regarding whether or not to reverse the polarity of the Hi-Vi replacement tweeters when using them in AR speakers. Also take a look at page 12 of Restoring the AR-3a. It mentions reversing the polarity of the AB Tech replacement tweeter.

So, to answer "Why is the tweeter wired differently to the other drivers? Why is tweeter +ve wired to the -ve side?" I'd say "because they sound better that way in this system."  And to answer "Is it possible that the tweeter should be wired opposite to what is shown in the above schematic?" I'd reiterate Mike's comment. The schematic is the work of Minh Luong and John O'Hanlon, two of the authors of the AR-3a restoration book. Minh is a real AR speaker expert and John is a Ph.D engineer and professor of computer and electronic engineering, so you can be sure they got it right.

OTOH, if you want to try playing with the tweeter polarity in your 3a Improveds, go ahead and see which you prefer.

Kent

[RoyC]

As Mike and Kent have assured you, the AR-3a Improved's original tweeter is wired as shown in the schematic. Bear in mind, however, that the HiVi tweeter is not the same as the original tweeter, and its use in the original AR-3a, with an added parallel coil, provides an approximation of the original sound. Consequently, contrary to the theoretical assumption we made when writing the 3a restoration guide, some people prefer the polarity reversed and others do not. In other words, there is no "correct" configuration when using this tweeter with the 3a.

To make matters more interesting, the 3a Improved is a different animal than the original 3a. I only know of one other person who has tried to use the HiVi tweeter with the 3a Improved, and after much experimentation replaced it with the AR-11 tweeter. In my opinion, Kent's advice is the best you will receive under the circumstances.

Roy

[Stephen M]

Thanks Kent and Roy,

At this point I'm not inclined to change the polarity, as I like the sound as-is. Following up on Kent's post, I've done some more reading and have learned that there are indeed instances where the phase of tweeter or midrange are inverted, depending on the crossover. I don't have the knowledge of crossovers or filter circuitry to understand the reasoning behind this fully. I'm sure the authors of this schematic got it right.

The HiVi tweeters sound very good to my ears. Initially the system seemed very bright, but it has improved greatly since I put a rug over the bare floorboards between the speakers and my listening position. I intend to continue tuning the room to flatten the response as much as possible, starting with bass traps to address significant nulls at 72Hz and 216Hz.

Cheers

Stephen

[JKent]

10 hours ago, Stephen M said:

The HiVi tweeters sound very good to my ears. Initially the system seemed very bright, but it has improved greatly since I put a rug over the bare floorboards between the speakers and my listening position. I intend to continue tuning the room to flatten the response as much as possible, starting with bass traps to address significant nulls at 72Hz and 216Hz.

I didn't realize you are using HiVi tweeters. That introduces a whole other factor. Did you use the 0.05mH coil? There may be other necessary changes to the crossover and Roy may be the best one to consult on that.

Kent

[Stephen M]

Roy has offered some advice regarding these tweeters. He pointed out that the AR-3a Inproved crossover already has a 0.1mH inductor across the tweeter, and suggested keeping this in place and testing before making any changes. At the moment I'm pretty happy with this setup, but time will tell.