Vandersteen 5a battery biased crossovers

Dead batteries in the crossover/filters make a difference. The bass response sheds some "body" or shall I say become somewhat anemic.

In my case, I bought a pair of the Vandersteen 5A's used and immediately placed them in storage for almost 3 years. I recently installed them about 3 weeks ago for the first time and my local dealer mentioned the batteries possibly needed replacement by now. He sold the pair to the original buyer.

Anyways the speakers sounded great from the start so i did not mess with batteries. However, I was chasing down a troublesome grounding hum in my system when I swapped my power conditioners around including power cords. When I finally isolated the culprit, I noticed that my 5As, sounded like the "soul or body" was just not there. I kept checking the bottom to feel if the subs were working. Mind you the bass was still there but just lacked WEIGHT.

Well Lo and behold, I picked up a brand new pair of filters yesterday evening (because I thought the original filters were lost after all these years in storage and I had to order a new set from my dealer) I installed the filters with all settings in the off position in my haste and frankly it just did not feel right. Luckily I was listening to the 2ce's at my dealer that afternoon paired with a GRAAF OTL so I knew this 5A was just MIA.

So I opened the filter, adjusted for my amp and VOILA, the 5A delivered. That was an eye opener. The batteries barely had enough juice after all these years and eventually shut off the filters, hence the anemic sound

The batteries are your typical 9V batteries and did not look difficult to change. I will watch my dealer change the batteries in the filters next week before I put them up for sale here.

I have thought a bit more about it and since a battery typically has about 1.7 ohms of internal resistance and since it must be part of the circuit somehow then you may need to worry about it. A leaky or corroded battery or a change in the battery internal resistance over time might affect the sound. If you think about it - a chemical battery will likely change properties over time quite a bit more than a stable polypropylene capacitor - so it might be advisable to replace/check this regularly....

It makes sense to keep them operational. I just wanted to see if anyone has crossed this bridge before me. Is there anyone here that has actually changed them already and can confirm that it requires no special ability or precautions?

I did some digging around. JBL use this Vandersteen idea in their K2 speaker. As you are probably aware capacitors vary in quality and linearity. If you bias a polypropylene cap then the distortion products (due to non-linearity) will still be there but they will all be even harmonics (more benign to our ears). Also the circuit should be such that it won't matter about the battery aging (normally connected to a 1 K or more resistor). It does mean that the circuit requires two much larger (more expensive) capacitors in series of twice the value of what you would need if you used one capacitor. Since capacitor non-linearities tend to increase with size, a lot will depend on a the careful choice of components if it is to be an improvement over a single capacitor.

It also opens the door to using polarized capacitors in a crossover although I don't think Vandersteen does this (he uses polypropylene)

Anyway - interesting stuff - I hope this helps. I have found an AES paper on this subject if you are interested.

Ask Boobtube he had a pair of 5's that needed batteries, he pulled the units out and sent them to Vandersteen.