Peerless BC25TG15-04 Ferrofluid Issue


Peerless BC25TG15-04

The BC25TG15-04 is a budget tweeter by Peerless. I’ve never worked on a tweeter that cost $16.65 before, so it’ll be interesting to see how it fares against more expensive ones.

I did a quick audition of this BC25TG15, mating it with a HiVi L6-4R Kevlar Cone woofer. It was just to give me an idea of what the BC25TG15 sounds like. The system is bi-amped with a 24dB/oct crossover set at 2.2kHz.

After tuning the speaker with OmniMic, I proceeded to play some music. It was apparent immediately that something was not right. The tweeter sounded constipated. It’s like the highs were impeded. I don’t ever recall a fabric dome tweeter sounding this horrible before.

The following day, I decided to check the ferrofluid. I removed the four screws that connect the face plate to the magnet and gently lifted it up. I noticed the voice coil was not fully immersed in ferrofluid. Maybe that’s where the problem is. I decided to remove all the ferrofluid in the tweeter, from the voice coil to those in the gap and reassembled the tweeter. 

Lo and behold, the BC25TG15 came alive. This is what a fabric dome tweeter should sound like. That unmistakable airiness. More than that, the highs were coming out effortlessly. The sensitivity jumped to what I expect from a tweeter.

So, if you’re not happy with your BC25TG15, you may want to try this. The difference is night and day.There’s no harm in removing the ferrofluid. The only difference is in lower power handling.

If you’re uncomfortable using this tweeter without the ferrofluid, you can re-apply new ferrofluid to the BC25TG15. Remove all the old ferrofluid and squeeze in new one into the gap. Parts Express sells them. The 100ul size will fill up the gap completely. I can verify this because I did that with my Peerless H26TG45-06. 

PEERLESS BC25TG15 THIELE SMALL PARAMETERSImpedance sweep of BC25TG15 (without ferrofluid)
PEERLESS BC25TG15 DISTORTION 2K2Harmonic Distortion of BC25TG15 (without ferrofluid) with crossover at 2.2kHz (24dB/oct)
2nd and 3rd harmonics are 50dB below fundamental.

PEERLESS BC25TG15_RAW_2K2_2K6_24dBBC25TG15 (without ferrofluid) in 13L Box with Baffle Width=8.5″
Black=RAW, BLUE=2.2kHz (24dB/oct), RED=2.6kHz (24dB/oct)
Smoothing = 1/12th octave