BM15A

BASICS

The DynAudio BM15A is a VERY powerful self powered studio monitor. I looked around quite a bit before buying a set of these. With an impressive 10 inch woofer that can handle a punchy response down to 30HZ and a silk dome tweeter,both speakers powered by two amplifiers (100w tweeter/200w woofer) the BM15A is a powerhouse!
They sound great while handling some very low frequencies,and most of the time can shake my studio so bad that things fall on the floor. My main gripe with these speakers is that the power switch is on the rear of the speakers making it difficult to get at.

NOISE ISSUE

Over time with use, I started to notice a weird fluttering noise out of one of the speakers intermittantly. At first I didnt think much about it and thought that I just had a loose connection on my patchbay somewhere. One day I decided to remove the patchbay and install a new set of speaker cables as I thought they may have been the issue. Come to find out,the problem was still there. The noise can be described as a scratchy type of noise when playing anything with a very low frequency. I even replaced one of the woofers thinking it was a speaker issue since i tried everything in the audio path up to that point. Even replacing the woofer the noise was still there. A Pretty costly repair to not fix anything! After some tinkering,I found that a relay on the circuit board that can cause a poor connection. There seems to be corrosion on the relay contacts that cause the bad connection. This results in a scratchy static type noise out of your woofer or tweeker speakers.

My TEMP Fix

The relay is a bit tricky to find sourced from electronic parts supply stores. They want you to buy a $50 minimum of parts or other places just wont have it in stock. The relay is usually around $5 each if you happen to find it. I ordered parts for many other electronic projects I had going on and bought a dozen of these relays for future repairs,so i exceeded the $50 minimum. Parts delivery was going to take a week or two and I couldnt do any studio work without my monitors,so my 'Temporary fix" was just to solder the contacts together on the relay (as shown in the picture). The only issue with doing this is that you will get a loud 'POP' noise each time you turn on the speaker. I only had this for a very short time and it didnt seem to hurt the speaker,but if you are unsure of any potential damage then i wouldnt solder the relay contacts together. The relay can be opened-up and the relay contacts easily soldered together. Replacing the relay is quite a different story since the circuit board is dual sided. To replace the relay you will need a de-soldering iron to remove the solder from the holes that hold the relay in. I never had good luck with solder wick and for this i wouldnt suggest it. A good de-soldering type iron is the best for this. I bought a cheapo one at Radio Shack and it worked very good.

The Power of the MS20

One thing I had learned about speaker monitors is NEVER to send unregulated audio to them. I got a Frostwave Resonator MS-20 clone filter and decided to try it out though one of the BM15a speakers. BAD mistake! The MS20 filter can make some frequencies well above and below what the BM15a can handle,especially in self oscillation. To make a long story short,we smelled something burning and then noticed smoke coming out of the front port of the monitor. We sizzled the amplifier drivers on the circuit board and the monitor was inop after that. I opened up the monitor and replaced all of the drivers for the amp section of the board. Parts were fairly inexpensive and still obtainable,but the repair was very very difficult!

My best advice is to never plug anything into the speakers without going though some type of audio interface that can truely limit the sound. Never play a keyboard or drum machine though them! I learned the hard way. Since all of the repairs,I have not had any issues with them.