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um18-22 odd sound

421 views 11 replies 9 participants last post by  ronny31 
#1 ·
#6 ·
So the voice coil must be closer to one side than the other, and when you tap it on the opposite side it pushes over into the magnet. I ordered 4 of these and initially I returned one because of a cosmetic blemish on the cone, and now that my second 6000dsp shows up, I have to send another one back. Oh well.
 
#7 ·
There seems to be a high-ish QC issue with the UM18s. It could simply a correlation b/t how many they sell and a "typical" amount of failures/bad parts. The UM series isn't exactly a boutique driver. I have gotten bad drivers from them before and they took care of me. PartsExpress has excellent customer service though and will take care of you. I got lucky with the four UM18s I purchased last July; no issues.

I did an initial "easy break in" just feeding them a 30Hz sinewave at about 10v or so.

Then I built Ricci's test stand to REALLY break in all four. Details and cool video here: http://www.avsforum.com/forum/155-diy-speakers-subs/2084706-diy-driver-test-stand.html

After that last break-in I'm confident I'm good to go.
 
#10 ·
The UM series are built in China and shipped here. PE/Dayton receives them by the pallet and they pick orders and ship the same way. The shipping boxes are very sturdy. IMO, you would have to receive either a smashed box or be unlucky to receive a damaged unit. On any manufactured item from electronics to clothing there is an acceptable variance/standard of performance to meet. The manufacturer or designer sets the bar on what is acceptable or not. For (basic) example: "Each voice coil should be nominally 2 ohms. The acceptable range for each VC is 1.90 to 2.10 ohms. No more, no less." As long as the driver meets "the bar" for ALL parameters it is sent forward.

Whether or not they do a random QC and pull a box off a pallet here and there and run some tests is anyone's guess. But PE sells a lot of UM's in the 15" and 18" sizes, so it stands to reason that some percentage will be faulty. IMO what matters here is customer service. At any time during the normal business day you can get a real person on the phone at PE and within a few minutes, have a postage-paid UPS label in your inbox for the return of your faulty driver. That's one of the big reasons I still support PE. They "get it."
 
#12 ·
The magnet gap area is scraping at the coil, either inside or outside, and then it will eventually work itself through until it shorts the coil. Send it back and get a new one before that happens.
 
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