Monday, July 1, 2013

B&W 802 Series 3N

Recently assisted a professional musician recap his B&W speakers (for home use) as the mid reproduction had a "behind the veil" effect and the HF was not as open as it could be. Bass was nice in general but boomy.

I suggested an initial recap before performing any major changes since capacitors are normally the cause of tonal issues.

After inspecting the speaker cabinet, manage to locate the crossover boards at the (internal) base of the speakers. The following pix is taken of the lower compartment in the cabinet after removing the speaker connector panel.

Original crossovers inside bottom component of speaker

Access to the lower compartment of the cabinet was via an opening secured by 8-screws at the base of the cabinet - see below.

Base of speaker

Unfortunately I then discover the internal cabling linking the crossovers to the drivers were extremely short ... extending just 1cm out of the box!!!

After much trouble, finally managed to extract them troublesome critters out!!! You can see from the pix how short the cables are!

Original crossovers in speaker with base cover removed

Here's a close-up of the original crossovers. The crossover on the left is for HF and mid. The other crossover is for LF.  The yellow capacitors are Benings. No idea of the EC origin as these have been rebadged.

Close-up of original crossovers

Crossovers after recap except for the 26uF EC

Could not locate a single component replacement for the 26uF EC as it is a non-standard value, and, there was not enough space to install the larger polypropylene equivalents in-parallel (to achieve the required capacitance). Since the 26uF EC seems to be in good condition, left it in-place for the time being.

Checking via multimeter before and after recapping shows no diffrence in the impedence with the LHS/RHS of the HF and LF wired together - should be the case.

Hooking up the recapped speakers reveal initial improvements in the HF and mid clearity. Bass was now firmer as well.

2Weeks later

The owner reported all was fine expect the mid seem to be out-of-synch with the HF and LF. Hence the 26uF had to be replaced after all.

Since I was not able to locate a replacement 26uF capacitor, I decided to fashion a suitable replacement using available values. Had to mount the non-EC caps onto a DIY PCB board to provide a solid platform for the replacement caps.

Resultant replacement for the 26uF
Rear view of the 26uF replacement

When I (finally) manage to test the extracted 26uF EC caps, both showed approximately 28uF though they were label as 26uF. Values of the other original capacitors were within tolerance of the specified values (with larger variations).
Test for actual value of the 26uF EC

The following shows the crossover boards after the 26uF EC has been replaced.
Total recap of the crossover boards

After the 26uF EC was replaced, the mid reproduction now in-synch with the HF and LF. Previous recap without replacement of the 26uF resulted in the mid being out-of-synch with the HF and LF as the polyproplene caps were quicker than than the EC.

The happy owner reports the sound is still evolving as the caps are being run-in but a definite worthwhile improvement over the original!

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