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Posted by on Nov 8, 2014 in Featured | 0 comments

Replacing Bowers & Wilkins DM2a Subwoofer Drivers

Replacing Bowers & Wilkins DM2a Subwoofer Drivers

Why bother to repair your 40 year old Bowers &Wilkins DM2a speakers? Because they can still be a very good alternative to paying a lot of cash for a new pair floor standing speakers.

Personally I prefer the wider DM2a cabinets with appropriate stands and the black speaker grills that blend in nicely with my 50 inch Samsung plasma TV.

Purchasing a used B&W replacement isn’t the best solution because the open circuit issue is likely a common problem. This is not a case of over powering the driver more likely related to flux not being fully removed from the coil wire solder connections to the stranded wire going to the terminals having over time it has degraded the connection

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Anechoic

Since I don’t have access to an anechoic chamber and test tools my DW 200/2 subwoofer replacement driver is based on careful selection using the available specifications.

Proof of success is measured by the quality of sound reproduction using various music examples at different volume levels. Note that even the highest quality speakers are limited by room acoustics and the quality of the audio content.
 

Why Choose Bowers & Wilkins speakers?

 

Before choosing my DM2a speakers I researched and listened to many other speakers. This was back in 1975 when I was young and living at home with my parents.

None of the other speakers had the sound qualities that I was looking for.

One day my father mentioned that perhaps he should take me to the Worthing west Sussex Bowers & Wilkins shop. In those days Roy Wilkins ran the shop and John Bowers ran their east Worthing factory.

My father had been a member or the Worthing amateur radio club where he met John Bowers and had worked for John Bowers and Roy Wilkins for a short while.

After a couple of hours with Roy listening to DM1’s, DM2’s and DM5’s I decided on the DM2a’s.

Reading current DM2a reviews some say that both top and bottom end performance is not comparable with the today’s technology. They are however still considered to be very good speakers. For my taste my new subwoofer driver provides slightly better performance. If I had opted for buying the new B&W CM9’s or 10’s it’s likely that I would have also have needed the additional subwoofer.
 

Replacement DM2a DW 200/2 Subwoofer Selection

 

My B&W DW 200/2 replacement choice is the Visaton TIW 200 XS 8 inch 8 ohm high end woofer.

The cone looks fairly similar to the DW 200/2 with the elastic ring. However technology wise it has many advantages over the DW 200/2.tiw200xs

The TIW 200 XS has a larger magnet arrangement which improves the cones sensitivity over longer excursions. Current design technology, cone materials, manufacturing and quality control processes make this a superior driver while still being similar to the DW 200/2 in terms of frequency and impedance response.

Of concern was the TIW 200 XS 120 watt rated power twice that of the DW 200/2 and that there could be cross over filter related issues. This didn’t turn out to be the case. I noticed better performance at lower volume levels where before with the DW 200/2’s I used to press the loudness button to achieve satisfactory base.

I also found that the subwoofer, midrange and tweeter combination seemed to work well over all volume levels.
 

Replacement DM2a DW 200/2 Subwoofer Installation

 

Driver replacement is a simple 20 minute exercise per speaker cabinet.

First place the cabinet on its back. Unbolt the DW 200/2 from the front baffle, lift it out and place it on the baffle.

Next unsolder the brown and green wire connections. Note that the brown wire is soldered to the terminal with the red dot. The connection polarity is important for correct cross channel phasing. A battery can be used to check the polarity of the new speakers. However, the brown wire is soldered to the large terminal and the two green wires are soldered to the smaller terminal.

The terminal arrangement being different I found it necessary to extend a wire on one of the cabinets.

The gauze on back of the DW 200/2 can be re-used on the new speakers using some sticky tape to keep it in place while pushing the new terminals through the gauze. It keeps unwanted particles from getting into the back of the cone.

The new driver is an exact fit for the baffle cutout but doesn’t use the same four bolt pattern. Six 5/8th black Philips countersink wood screws can be used to keep the new speaker snugly attached to the front baffle. Pilot holes are needed and vacuum cleaner used to remove wood particles.

This is a minimally invasive retrofit and any movement of the internal cabinet acoustic dampening material is unnecessary and should be avoided.
 

Replacement DM2a Visaton TIW 200 XS Subwoofer setup and testing

 

Initially I only swapped out the open circuit driver just in case there was an obvious issue with the cross over filter compatibility. It also provides an opportunity to compare the two subwoofer drivers.

My cost for the new sub-woofers was just over $200 can each with tax and shipping. I also decided to purchase a Sony STR-DN1040 AV receiver which is rated a 100 watt stereo per channel with a 6 ohm load. I already have a Panasonic Blu-ray player and Technics SL110 direct drive record deck with an SME arm and Shure V15 Type III cartridge.

I used the Shure cartridge test record to verify my initial setup and since I have a number of LP/CD duplicate recordings it was interesting to compare performances. In most cases the dated re-mastered performances do not compare favorably with modern recordings and Blue-ray technology.

John Bowers and Roy Wilkins were very selective about the music that he used for demonstrating the qualities of their speakers. The Sony STR-DN1040 calibration microphone makes room calibration easy and provides a measurement for the positioning of left and right speakers.

Philips, Deutsche Gramophone recordings of The Nutcracker, George Gershwin Rhapsody in Blue, Elgar’s Pomp and Circumstance and Igor Stravinsky’s Firebird were used for audio assessment. The Walt Disney 2000 fantasia was found to be very good with enjoyable performances of the firebird and Rhapsody in blue.
 

A B&W DM2a Visaton TIW 200 XS Subwoofer retrofit assessment

 

As previously mentioned not having a professional test environment and having a pair of none usable Bowers & Wilkins DM2a’s. The decision to find and retrofit a reasonably priced replacement subwoofers myself was a little risky. However proved to be a good choice.

I found that the new sub woofer performance was beyond my expectations and was satisfying at low, medium and high volume levels. I found clarity without distortion for base mid-range and tweeters at all power levels. A concern that the existing mid-range and tweeter would be over powered at high volumes was not found to be an issue. No flatness was perceived in the mid-range frequencies during my audio assessment.

Contrary to what I have read about the DM2a tweeter imperfections I found for example that the Nutcracker triangles and piccolos were bright and clean.

The Fantasia Rhapsody in Blue DVD recording provided a very good work out for all three drivers. The piano is rich and true for all frequencies. The recording quality is good, there is clarity in the individual instruments, upping the volume brings the performance closer and does not result in harshness.
 

B&W DM2a Visaton TIW 200 XS Subwoofer retrofit conclusions

 

B&W-DM2a

Having a driver go open circuit need not consign these B&W DM2a speakers to a dusty basement corner. New costly replacements need not be the solution.

Today’s slim stylish home theater configurations with 5 or more speakers do not necessarily provide the best audio experience. B&W DM2a speakers with Visaton 200 XS subwoofers don’t need an additional subwoofer. The base is more than adequate for recreating the home theater experience.

I’m very happy with my retrofitted DM2a’s.

Best wishes,

Mark. 

 

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