diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Wild Burro Audio (http://www.diyaudio.com/forums/wild-burro-audio/)
-   -   Who wants a shorting ring? (http://www.diyaudio.com/forums/wild-burro-audio/156443-who-wants-shorting-ring.html)

pjanda1 9th December 2009 12:46 AM

Who wants a shorting ring?
 
I've heard a couple of requests for shorting rings. I'd like to briefly give a couple of my thoughts, and hear a few of yours. First of all, I am not well versed in loudspeaker design. Most of WBAL is a combination of good networking and dumb luck. I'm learning all I can, and that is part of the fun.

I had the opportunity to compare back to back, a couple of Burro ancestors that had only two difference. One was mostly cosmetic, and the other was a shorting ring/copper pole sleeve. It's a tiny part that fits nicely on my pinky, but it makes an absolutely huge difference in the way the driver behaves. Basically, it eliminates a bunch of distortion, and causes the impedance curve to remain quite flat into the high frequencies. That sounds good, right?

Here is the rub: that rise in impedance, in combination with most amplifiers, helps keep the frequency response flat. Loudspeakers naturally have a rising frequency response above a frequency related to their diameter. Physics can be a bugger. When the impedance limits the power the amplifier puts out roughly in proportion to that rise, you get, for an 8" driver, maybe a 5 db rise on axis. Then, when you listen a little off axis and keep in mind that your room absorbs HF, you can get a pretty flat response out of a single driver.

But, when the impedance stays low, you get maybe a 10db rise on axis. Don't believe me? Check out the FE206E and FE207E response charts. See the difference? Think that is do to the 206's slightly lower Q? Take a look at the Betsy and BetsyK. They have a Q difference much greater than the 206 and 207, yet their rise is nearly identical. As a matter of fact, if you lay the BetsyK's response over the 207's (when measured on the same setup) they are very, very close. When you lay say, the BetsyK's ancestors (with the shorting ring) curve over that of the 206, you get, again, a response that is very, very close.

I can't tolerate the on axis rise of the driver with a shorting ring. In my system, they sound incredibly bright. Searingly bright. Shouty. It ain't a peak, it's a general trend. One of my customers owns another makers 8" driver with a shorting ring, and talks about a notch filter to cure it's ills. But, it isn't a break up mode, it's just 5-6db too much HF.

Folks tend to deal with it by using cabinets that have considerable bass gain, and gain up into the midrange. Some find that sound to be very detailed, and preferable. I also suspect that some shorting ring fans are a little older and have some hearing loss. Don't yell at me, there is nothing wrong with that. I'm 30 and I can only hear to 16K (I grew up on a farm, with shotguns, and went to play in incredibly loud orchestras and big bands). But, don't assume that the top end you like is the top end everybody likes.

If you like that sound, I won't stop you from using such a driver. I encourage everyone to use equipment they like, and I don't judge. I think different folks ears and brains prioritize different things. But for folks that like a reasonably flat in room response, with most cabinets, most rooms, and most amplifiers, if you have an 8" fullranger with a shorting ring, you need a compensation circuit.

That might be a good way to go. Theoretically, you could get lower distortion, and maybe better sound. Most of the customers I've heard from don't want to use any capacitors, inductors and resistors. I don't want customers unhappy with their speakers. But, for those that understand the effects of a shorting ring, not just those who assume it is better, I would consider offering a speaker.

So, who wants one? I would need a few customers to justify having them built. It wouldn't add more than a few bucks to the cost.

Speak up! Let's keep this thread focused on related motor issues though. If you're looking for something else, start a new thread.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

tinitus 9th December 2009 01:03 AM

Quote:

Originally Posted by pjanda1 (Post 2006776)

Speak up! Let's keep this thread focused on related motor issues though.

I dont know
Do have any specs on voice coil inductance
Is it any issue at all with such "light" drivers

Better think about underhung
Ups, I did it, sorry

pjanda1 9th December 2009 01:26 AM

That's why we've all got such short coils, isn't it?

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

tinitus 9th December 2009 01:36 AM

I dont know
These days even tweeters may be underhung
But maybe just convenient
Meaning, with short voice coil underhung is easier
Or, voice coil might be even shorter

badman 9th December 2009 07:59 PM

The rising response is an issue with 'normal amps' with the shorting sleeve.... The rising impedance emulates this in amps with higher output impedances, though not as dramatically. One can always EQ, if necessary, though some purists don't care for that approach.

The other concern with a loss of magnetic strength doesn't need to be addressed via changing the magnet, you have the option of adding a bucking magnet if your steel isn't saturated.

The other option, which can work for small batch production is plating. I'm betting you could do a thick(ish) layer of copper or silver easily enough on the pole.

kenpeter 10th December 2009 12:00 AM

Well the pole and top plate are somewhat shorting rings already.
not as efficient as copper or aluminum, but still a solid iron short.

I think the real magic might be in shorting extra turns that might
happen to overhang a given magnetic gap. Front and back, inside
and out.. Nothing but parasitic inductance to be lost here.

pjanda1 10th December 2009 03:54 PM

The copper pole cap is probably the easiest to implement. Less labor than plating, methinks. I don't know if I have access to any VC's that would work for shorting turns. The loss of strength isn't too bad. I can't recall the exact numbers off the top of my head. It might mean a slightly bigger box, but as long as one is building the enclosure with the drivers in mind, it shouldn't be a big deal.

Paul

badman 11th December 2009 04:24 AM

Quote:

Originally Posted by kenpeter (Post 2007982)
Well the pole and top plate are somewhat shorting rings already.
not as efficient as copper or aluminum, but still a solid iron short.

I think the real magic might be in shorting extra turns that might
happen to overhang a given magnetic gap. Front and back, inside
and out.. Nothing but parasitic inductance to be lost here.

Not even close to as efficient, and the only thing the shorting turns does is act as an electromagnetic brake, it does nothing for distortion. Note the effect of lowered Qms on drivers with an un-split aluminum former.

godfrey 14th December 2009 01:47 PM

Hi all

Shorting rings actually can/do reduce distortion. The voice-coil current causes fluctuations in the magnetic field, resulting in (mainly) 2'nd harmonic distortion. The induced eddy currents in the shorting ring help counter-act this.

Paul mentioned in another thread experimenting with whizzerless drivers.

Maybe a driver with a shorting ring (to clean up the distortion) but no whizzer (to tame the treble) would be a winner?

Regards - Godfrey

pjanda1 14th December 2009 04:05 PM

No one will argue that shorting rings reduce distortion. Funny that you should bring up the Betsy WoW (which I think will be my new acronym for With out Whizzer). I've read and talked to many folks who for some reason or another, want to believe the brightness of 8" fullrangers with a shorting ring is a single troublesome response peak, rather than an overall trend. It can sort of sound like a peak to the untrained ear, and of course, a peak might be a simpler idea to wrap your head around. Sometimes folk blame the whizzer, thinking it is responsible for all that nasty brightness, and then resort to cutting it off. I've seen even seen people endorse the result! But, while there is less treble overall, you've then got even bigger problems to address. The response still rises hard to 7k or so, and still needs shelving of some sort. Except, you also then need a tweeter!

Now, that isn't to say that a whizzerless widebander with a shorting ring doesn't have incredible potential, but you've got to be willing to design and build significant filters as well as add a tweeter.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers


All times are GMT. The time now is 12:50 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2