Author Topic: Wharfedale Emerald 99 Mk IV  (Read 11377 times)

honesthoff

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Wharfedale Emerald 99 Mk IV
« on: March 20, 2007, 12:29:00 PM »
I pulled out a pair of the above from storage about two months ago and hooked them up for a "new" office system and found the tweeter was fried.  After contacting Wharfedale and finding no replacement was available, I ordered a set of very similar Vifa's from Madisound.  My problem is the Wharfedale's have one blue and one yellow wire which attach to the new tweeter and I forget which goes where.  Does it matter?  The Vifa's have no markings on the terminals.  Any help would be appreciated.

Offline richidoo

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Wharfedale Emerald 99 Mk IV
« Reply #1 on: March 20, 2007, 01:52:59 PM »
Yeah it does matter. Because the driver is a simple DC linear motor, the wiring polarity determines whether the tweeter pulls air in or pushes air out on a positive voltage swing. The polarity must be same for each speaker for the tweeters to be in phase, and you could experiment to determine that by ear easily, because your stereo image would be terrible with these polarities not matching. But in addition to the L/R tweeter polarity being in unison, the tweeter polarity must also be wired correctly in relation to the other drivers. And the larger drivers and tweeters could well be wired opposite, that is one of designer's variables when tuning a speaker system.

The larger drivers, having larger mass, will accelerate slower than the tweeter. The crossover circuit (including wiring polarity) is designed very carefully to allow the motion of the faster tweeter to "hand off" the motion to the larger drivers gracefully. Wiring tweeters backward would ruin this dance.

How to find your way out of the woods, I dunno. Since the motion of a tweeter is so small, it is not possible to look at it to see which way it moves with a battery put across the leads like you can do with a larger driver.  Maybe there is a plus sign next to a lead on the new tweeter. You could get that info from Vifa on a technical drawing of the driver. Then you need to know from Wharfedale how the tweeter should be wired to the crossover. If you have that info, you can use a D battery and voltmeter to wire the tweeters correctly. Just mark the woofer wires before you remove them from the woofers!

If you can't easily get that info, I would try working out one speaker first, to  get the tweeter/crossover wiring correct on one speaker. You may be able to hear an improvement in one polarity vs the other. Listen to transient signals and acoustic instruments rich in high-midrange frequencies on an excellent recording. Stuff like female voice, listen for the articulations like letter T and S sounds. Cymbals, oboe, violin, splatty trumpet, some of the harsher music that you are very familiar with what it is suppsed to sound like. If possible, play it in mono through the one speaker and pick the tweeter polarity that a variety of music signals sound best. Then add the other speaker and swap polarity of the that other tweeter until the stereo image is good in the high frequencies, like a cymbal is locked in the center of the stereo image. Actually you will have the yellow and blue wires to use on the second speaker, but check imaging anyway.

I sure hope you get a better answer than this from a real speaker expert.
Rich