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Zu Soul Superfly 8 ohm experiment

Have been Zu owner for many years starting with Tone progressing to Druid -then Essence and now Soul with nano tech drivers. Drive the speakers with Unison Research Preludio which is a 15 watt single ended class a amp which utilizes 6 ohm output taps. After reading a review of the speakers which suggested the speakers sounded best when paired with an amp that utilizes 16 ohm output taps i posed the question to Sean. he suggested i could experiment altering the impedance of the speakers by utilizing a 16 ohm resistor to lower the impedance to 8 ohms. I have generally been happy with the sound of my system except for a bit of hardness/glare in the higher frequencies that shows up on some recordings . i attributed this to the recording technique as ell as less than optimal listening environment (10x12 room ) also wondered if perhaps the preludio was not happy with the 16 ohm impedance. Decided to give Seans' suggestion a try and purchased a pair of 15 ohm Mills resistors from parts Express. Wrapped the leads around each of the speaker terminals -placed the spade lugs of the cables over the leads and tightened down the connector. have to admit I did not expect much, but was pleasantly surprised. Thought the speakers sounded cleaner - vocals clearer and a definite decrease in the high end glare/hardness . After changing speaker cables I had been bothered by what seemed to be an exaggeration of sibilance . but noticed that it now sounded much more natural and the hardness associated with it improved. wonder if any other Zu owners have had a similar experience ?
dcr

Showing 3 responses by dcr

dcr OP
10 posts
 
Funny you should mention the anticable site as a friend talked to me about it as well. Really happy with the sound of the speakers now and will probably leave the resistor in place for awhile. Speakers seem more coherent- bass response/detail is improved and sound stage width and depth greater. Noticed that the Zu Union and new Soul II both utilize an 8 ohm driver. I wish that Zu would offer an 8 ohm driver version of the Superfly driver as there seems to be few amps that are optimized for or have a 16 ohm tap.
dcr OP
10 posts
 
Thank you for the information . That explains why the speakers sound cleaner/clearer now as the distortion has been reduced. Checked the resistors for heat and did not seem even warm to the touch after 1.5 hours of listening. I am happy with the amplifier,although with a fixed output it may not be as versatile as i like. Agree that the resistor is not an ideal solution and hope that an 8 ohm driver will be added to the Zu lineup
dcr OP
10 posts
 
Purchased the Mills 15 ohm resisitors from parts express . they are rated @ 12 watts so may not be suitable if your amp is high powered. consider that the output from the amp will be halved by the reisistor meaning half will go to the speaker and half to the resisitor. my amp is 15 watts so half will be about 7.5 watts . the resistor is not noticeably warm or hot after playing the amp.
there are higher rated vishay resisitors (50 watts ) available from mouser.com but the mills resistors are working fine.

the resistor has a wire lead at either end - there is no positive or negative . with needle nose pliers gently bend the wire to form 90 degree angle @ the barrel of the resistor. at the far end of the wire - bend in to circular shape to fit around the terminal posts on the speaker. remove the cardas clamp and fit the circled ends around the posts and place the spade lugs over them before tightening down the clamps.
if you like email me, and i would be happy to forward pics
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