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Advice on reconditioning pair of B&W DM 110.


DdDesign

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Hi

I have an old pair of B&W DM110 speakers that I am reconditioning. I am relatively new to this type of thing and would love some advice from those with more experience.

 

The speakers have been in storage for about 15 yrs, apart from the odd bit of playing here and there.

 

One of the tweeters was broken and I have managed to find a genuine replacement on gumtree. I have put that in and they are actually sounding great!! - at least to my ears. I have also removed the drivers and checked out all the foam inside which also seems fine apart from where a mouse ate some of it, but not too much. I have cleaned them out and reset the foam in the cabinet.

 

I am wondering if there are any other parts that would be worth replacing or at least checking, given the age of the speakers and the long storage time? I don't really know too much about cross overs or capacitors etc. I assume if they are sounding good there are no issues there?

 

Anyway if anyone has any suggestions on other aspects of the speakers to check I would appreciate your thoughts.

 

Also the grills need recovering and I am wondering what the best material to use is? I was going to head down to spotlight and see whats available.

 

Cheers Doug 

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That is great about the replacement tweeter!

 

The dust cap (centre) of the bass driver is pushed in. It is usually easy to suck this out with a vacuum cleaner, but be very gentle! It is best to use a variable suction vacuum on the lowest setting and even then with the vacuum relief vent open (if there is one). Sometimes a bit of warmth from a hair drier will help soften the dust cap to good effect. Watch out - two much suction and you could suck the dust cap right off into the vacuum cleaner! The dust cap will affect the smoothness and dispersion of the upper range of the bass driver, which is right across the vocal range. The affect may be subtle, or not. They will also look better, of course.

 

The tweeters on these old B&Ws are smoother and give less "ear fatigue" than the newer laminated aluminium domes.

 

If the rubber surround is separating from the paper cone, you can use a bit of acrylic adhesive to fix it. Otherwise you might get some buzzing noises on bass beats. You can buy the right glue from Speakerbits: http://www.speakerbits.com/index.php?page=shop.product_details&flypage=vmj_estore.tpl&product_id=780&category_id=1028&option=com_virtuemart

Edited by Guest
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Hey Johnmath, I agree I also have pair of B&w 601 s2 with the aluminium tweeter and I have spent a bit of time setting them up so they don't sound too bright. They are good for detail but these DM110's are much smoother and with bigger drivers I can fill up my large room nicely. 

 

Cheers on the advice regarding the covers I will try it

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I am not familiar wight the internals of the DM110s. Post some pictures of the crossover and the inside of the cabinet and I might be able to make some suggestions :)

Edited by Guest
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You might find that the crossovers are on the rear of the speaker terminal inserts, there may be three electrolytic caps in each, replace these with equivalent capacitance polypropylene caps.

Edited by ortofun
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The service manual for DM110s is available here: (no title)

 

 

As ortofun said, there are three electrolytic capacitors. There is a tendency for electrolytics to drift lower in value and become increasingly lossy with age, which will shift the tweeter crossover upwards in frequency and down in level.

 

The chances are that B&W actually got the crossover alignment correct in terms of the component values, even if the implementation left a bit to be desired, it is a good bet to stay with the original values, 10, 8 and 7 uF. Unfortunately the 8 and 7 values are not readily available, so use 6.8 in place of 7, and 8.2 in place of 8. These minor differences are of no consequence.

 

Suitable replacement crossover capacitors are available here: http://www.wagneronline.com.au/scr-mkp-metalized-poly-caps/scr/9-909090909xx0-usersearch/1-3332/fl/

 

The capacitors should be hot glued to a rigid substrate so that they cannot vibrate.

 

There are two inductors. The black one is air cored and across the tweeter. That one is OK'ish. If you wanted to replace it, you could use this one: http://www.wagneronline.com.au/xla0.18/inductors-crossover/xla0.18/9-909-9xx0-usersearch/1-111/2-1528/pd/

 

The green one is ferrite cored and in series with the bass driver. That one is not good because ferrite cored inductors are non-linear, which will cause compression and even order harmonic distortion. It is relatively high resistance which will limit the amplifier's ability to control the movement of the bass driver potentially causing "ringy" bass and coloured mid-bass.

 

A suitable inductor is here: http://www.wagneronline.com.au/sol2.2/solen-crossover-inductors/s142.2/9-90909-9xx0-usersearch/1-3337/2-1311/pd/

 

Note that the above two inductors are slightly lower in value than the originals, but the difference is not significant in this implementation.

 

A second problem exists with the placement of the two inductors, which will form a loosely coupled transformer. This is a completely unintended consequence of sloppy layout that will colour the midrange. It is important that the magnetic field lines of one inductor are not parallel with the magnetic field lines of the other inductor. The way to achieve this is to ensure that the axes of the two inductors are perpendicular, i.e. mount one inductor horizontally and the other on its side.

 

There is one resistor in the crossover, and I would expect it to be just fine.

 

The replacement components are much larger than the originals, so you will need to make a new crossover board and put it inside the cabinet. My suggestion is to use a piece of MDF and tagstrips or nails as connection points. Hot glue or cable tie all of the components to the MDF so they cannot vibrate, once you have tested the circuit. Build the crossover as two separate parts (can be on the same piece of board): the low pass for the woofer, and the high pass for the tweeter, and use separate input wires to each of your crossover sections from the (+) and (-) terminals. This will reduce intermodulation artefacts between the two sections.

 

The cabinets are foam lined, but devoid of bulk absorption material. This means that rear radiation (= noise and distortion) from the bass driver cone will "leak" out of the reflex port. Loosely fill the void behind the bass driver and above with polyester wadding (an old pillow or cushion is a good, low cost source of material). Make sure that the wadding is kept clear of the bass reflex port so that it does not impede air flow or introduce turbulence or buzzing. If you have a stethoscope you can listen to the sound coming out of the port before and after and you will be shocked by the difference this simple modification makes.

 

Edited by Guest
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To select a suitable material for speaker grille cloth is relatively straight forward.

 

1. You want a light weight two-way stretch jersey to make it easy to stretch the covers for neatness. Two-way stretch means it will stretch lengthways as well as width ways.

 

2. To determine the relative acoustic transparency, hold a stretched sample of the material up to the light. The more open "holes" you can see, the better. If you can't see holes, there will be too much treble attenuation.

 

3. A second test for suitable acoustic transparency is to hold some stretched material and blow at it. With your hand about 5 cm behind the stretched material you should be able to feel the puff of breath on your hand. If you can't feel the puff, the material will vibrate and buzz when playing bass notes.

 

Depending on the frame material, you can use a staple gun to attach the material, or you can use an acrylic adhesive which has "tack" like Speakerbits repair glue. This glue will allow you to reposition the cloth as it sets over a few tens of minutes so that you can get all of the thread lines straight. http://www.speakerbits.com/index.php?page=shop.product_details&flypage=vmj_estore.tpl&product_id=780&category_id=1028&option=com_virtuemart

 

Speakerbits is another supplier of capacitors and inductors to the Wagner links I provided earlier and may have better pricing: http://www.speakerbits.com/index.php?option=com_virtuemart&page=shop.browse&category_id=1139&Treeid=32&Itemid=146

 

Of course, Speakerbits also have grille cloth: http://www.speakerbits.com/index.php?option=com_virtuemart&page=shop.browse&category_id=1051&Itemid=146

 

As do Wagner: http://www.wagneronline.com.au/spgc151/speaker-grille-cloth/grille-cloth/909-90909-9xx0-usersearch/1-3002/2-6868/pd/

Edited by Guest
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No problems! let us know how you get on.

 

I found Speakerbits inductors are much cheaper than Wagner: http://www.speakerbits.com/index.php?page=shop.product_details&flypage=vmj_estore.tpl&product_id=236&category_id=1043&option=com_virtuemart

 

You should also check Jaycar and Altronics for components if you are on a budget. For the bass driver inductor, aim for a DC resistance R value of around 0.4 ohm (Ω) or less.

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No problems! let us know how you get on.

 

I found Speakerbits inductors are much cheaper than Wagner: http://www.speakerbits.com/index.php?page=shop.product_details&flypage=vmj_estore.tpl&product_id=236&category_id=1043&option=com_virtuemart

 

You should also check Jaycar and Altronics for components if you are on a budget. For the bass driver inductor, aim for a DC resistance R value of around 0.4 ohm (Ω) or less.

speakerbug.com.au have better inductors and Nigel is a great guy to deal with :)

Edited by henry218
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speakerbug.com.au have better inductors and Nigel is a great guy to deal with :)

 

Thanks for the tip! I've bookmarked his website for future reference.

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Hi

I have an old pair of B&W DM110 speakers that I am reconditioning. I am relatively new to this type of thing and would love some advice from those with more experience.

 

The speakers have been in storage for about 15 yrs, apart from the odd bit of playing here and there.

 

One of the tweeters was broken and I have managed to find a genuine replacement on gumtree. I have put that in and they are actually sounding great!! - at least to my ears. I have also removed the drivers and checked out all the foam inside which also seems fine apart from where a mouse ate some of it, but not too much. I have cleaned them out and reset the foam in the cabinet.

 

I am wondering if there are any other parts that would be worth replacing or at least checking, given the age of the speakers and the long storage time? I don't really know too much about cross overs or capacitors etc. I assume if they are sounding good there are no issues there?

 

Anyway if anyone has any suggestions on other aspects of the speakers to check I would appreciate your thoughts.

 

Also the grills need recovering and I am wondering what the best material to use is? I was going to head down to spotlight and see whats available.

 

Cheers Doug 

the company i work for may be able to repair woofer tweeter will have to has a good replacement  try Music Box and Speaker Hospital in Ashfiled Sydney 

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