I've got a screw loose, have you?

I feel foolish because I have been missing out on the music that my system is capable of providing. I only found out yesterday, and the fix was remarkably simple. Many of the screws holding the drivers in my loudspeakers were loose and needed to be tightened.

I have a CD2, 82, HiCap, 250 and Bariks. The first 3 are on an IKEA wall unit, the 250 on the carpet in front, and the Bariks on Linn stands (using the original CD2 interconnect, new black SNAIC, and new NACA5) - not ideal placement, but I am moving yet again soon. (Now, do I start with zero or negative FEPs?)

I remember when I first heard the CD2 at my Naim dealer four years ago, it was astounding. On one track, I felt as if I could tell who had tuned the piano being played. To me, hearing the sound of an instrument presented so well was wonderful and was a significant part of what I was looking for. I had a sense of hearing an actual, individual piano, and not some piano-like sound. (Am I losing more FEPs?) It put a big grin on my face and was such a huge difference to my usual experience of going into a HiFi shop and grimacing my way through a demo. Finally, I was ready to accept CD.

I bought a CD2, got it home and set it up myself. I had my Bariks, and my original older Naim amps – the NAC 12 and NAP 120 with an LP12 all bought new in the 70’s. This was later, with different equipment than the demo and a very hard sounding room. I was pleased, but it was not quite as I remembered it. However, I was happy to be able to listen to CDs. This year I have upgraded the amplification with secondhand purchases. Thanks to this forum for guidance on choices and on sources for secondhand gear.

The older secondhand gear went to Naim for recapping and, while better, it seemed to me that the system was still not sounding its best. At this point, I figured I needed to work on the electric hookup, buy a HiFi stand, move the furniture, move the TV, move my wife’s system, move my speakers, install screws in the hardwood floor, and put sound absorbing panels around the room. (Can I borrow FEPs from someone?)

Then I read James Jong’s thread on PRaT (“Crazy Little Thing Called PRaT”) earlier this week. Thanks to him for the thread, and to Rob Doorack for the reference to the excellent Martin Colloms article on the Stereophile web site.

Martin’s article mentioned that the drivers in a loudspeaker are subject to strong forces, and mounting screws can be shaken loose. I picked up a cross-head screwdriver and pulled the velcro-ed grills off my 20 year old Linn DMS Isobariks. I found that most of the driver mounting screws were loose.

I had not attempted to tighten them before, and many had a coating holding them from turning. I decided that loosening the screws by a quarter turn would free any binding to this coating. Also, when I tightened them, I would be able to determine when the screws were snug and avoid striping the threads from the wood holes. Sure enough, I was able to tighten until I felt some resistance, and this was usually more than the quarter turn of slack I had given them.

I think that over time the vibration of the drivers has resulted in the screws deforming the wood in the holes, so that they became loose without turning, or, alternatively, the coating may have allowed gradual rotation of the screws. Irrespective of the cause, it is clear that the drivers were free to move, preventing the cones from accurately following the amplifiers signal, allowing them to vibrate independent of the signal and allowing air to enter and leave the loudspeaker cabinet around the edges of the drivers.

Today I heard a guitar in my room, and I understand what PRaT is about.

I suggest that as part of your tuning or tuneup efforts that you check this out. However, if you do, please be gentle with your speakers and remember that if you tear the wood out of the screw holes the drivers will be much looser than before (and you will lose many FEPs)!

Simon