Recently, we’ve run into some particularly “grievous” examples of drivers available to DIY’ers, that have very severe “Achilles Heels”, either in design, materials used, or assembly.  We are going to discuss a few, so that more of our visitors know what sorts of things we look for NOT to sell or use.  We won’t mention who’s selling these, but we will not try to hide pertinent information either.  Manufacturers, though, we are not afraid to “call out”.  So far, most of these are from one particular country of origin, which you can probably guess:  This is not meant by any means to damn all drivers from that country, but it does seem to indicate that one should be cautious with their purchases.

#1 is an unbranded, seemingly nice little 7″ “buyout” driver with dual 8 ohm coils and a rubber roll.   A moderate problem is that the leads are not well run, from the cone to the terminals, and are prone to slapping either the cone or spider.  In some cases they fatigue due to the excessive “roping”, and become intermittent.  (This was on a std. break-in signal just over Xmax.)  Far worse though, under the dust cap, many have the end of the tinsel lead wire, where the coil wire is soldered to it, glued onto the top of the aluminum coil bobbin.  Sometimes a lead is shorted to the bobbin right out of the box”, in other cases, after the driver is run a bit hard, heat from the coil travels up the bobbin, softens the glue, and THEN contact from one or more leads to the bobbin occurs.  At best you may blow a fuse in your amp, at worst, the amp blows.  If you are using the driver in true “dual coil” mode, you may even have the opportunity to blow TWO amplifier channels (by connecting the two “positives” together via the coil bobbin.) 

Here’s a great pic from one of these: 

 
                                 (Click picture for larger image)

#2 is a high end, underhung coil / long Xmax driver, from a VERY well known company, TangBand.  A moderate “bugaboo” with this driver is that it unnecessarily gets noisy at moderate to long excursions.  This is a real WOE (What On Earth)?  Why would someone pour lots of cost into a high Xmax driver, and then gift it with excessive noise / distortion once it gets going?  Well, read on:  It turns out that maybe the noise is to warn the user that bigger problems are about to occur:  We found in 4 samples of these that the leads on 3 were too long and slapped the cone too easily.  On #4, the leads were too short, and combined with an absolutely laughable attachment to the cone body (on all of them, actually), one of the leads fell right off the cone (broke off) when the driver was pushed to Xmax.  But wait!  It gets worse!  The flex leads themselves turn out to be of a construction that tends to fail “too easily” when flexed a lot.  This makes this one of the most disappointing drivers we’ve tested in a long while.  These problems would be discouraging in an inexpensive driver, but perhaps not surprising.  One does not expect to see them in a premium product.

#3 is a Beston “ribbon” tweeter we tried out recently (was on sale).  Initial measurements looked great:  Output was high and frequency response very good.  But… the LMS test tones sounded a little edgy, and when we investigated further, we found that even at levels of 1/2 watt or less, all four samples had “buzzes” at several frequencies in the 5 kHz - 15 kHz range.  This is not an uncommon problem with ribbon / planar magnetic / “leaf” tweeters.  Investigation showed it to be, as usual, due to “unthorough” design / execution.  It did not look particularly easy to fix, so…  they were returned to the vendor.

#4 is a Sammi 5 1/4″ (closeout) item we recently tried out.  We’ve been fairly happy with several Sammi products, and, again, it appears to be a nice driver, with a treated cone, rubber roll, and venting in the cone, under the dustcap.  It’s problem is that the voice coil is miscentered (too low.)  This creates excessive distortion, and knocks down output by a couple dB (in this particular case.)  There is no good way to fix this:  We are going to tear down the ones we bought and rebuild them into something better…

#5 is any driver we’ve tried, sold by Pyle, in the last few years.  A few of their drivers actually do have uses, but you’d better be able to run your own tests, or find someone who can, as Pyle’s specs are generally worse than useless.  It’s sad, to see what happens to some of these names, after they are sold.

#6 is a series of Aluminum cone woofers from a popular supplier.  These have a vented pole piece and a porous felt dust cap — that’s right, they have a huge leakage path right through the middle of the driver!! The 8″ version’s spider tore after a few hours break-in at about 1/2″ peak-to-peak.