Upgrading my B&W's

[jimbones]

I am upgrading my DM 640's and because they are "old" some are saying that they are dated. What would you say is the speaker systems weakest link? Bass driver, Mid, tweeter? I am going to upgrade the XO parts. I have my idea of where to make some mods and I wanted to see if your opinions were similar to mine. Thanks

[5th element]

Driver technology hasn't exactly changed in the past few years, but it entirely depends where and what price point these were originally put at and what kind of performance B&W were wanting them to have.

The drivers are probably decent but nothing amazing and the crossover is probably a design of minimal component count to cut costs, but probably not cost cutting to the point of degrading the performance to an unacceptable level. Then there's the designers own personal philosophies, these sometimes clash with what others would consider optimal and might push the design towards sounding something like you would not prefer. Of course it could work the other way around too.

According to the B&W service manual all of the capacitors used in the design are of the electrolytic variety. These are perfectly acceptable but do not stand the test of time particularly well. The DM640s design is 20 years old. I would recommend you change the electrolytics for either new electrolytics or go for film caps.

The service manuals can be found here.

Service Manuals

As a recommendation I'd keep C1 and the C2 that is paired with R3 as electrolytics, but replace C4, C5 and the C2 that goes before R1 with decent film caps.

If the price of C2, as an 85uF film cap, is a bit much (and I agree it is expensive) I'd buy a 70-80uF electrolytic cap and parallel it with a film cap to make up the remainder.

Solens basic series of film cap are fine.

Solen Capacitors: Madisound Speaker Store

As are Bennics lytic caps.

Bennic Capacitors: Madisound Speaker Store

You can parallel up any combination of capacitors to arrive at the required capacitance.

[abraxalito]

Originally Posted by jimbones

What would you say is the speaker systems weakest link?

Ferrite-cored inductors. Resistive pad used to bring down the sensitivity of the mid. Non-polar electrolytics.

Go active.

[jimbones]

Right on. I am doing the XO ordering parts today. Thats funny how you picked up the mid being a little lod abraxalito. I was thinking it but was not planning to do anything. I'll now have to consider that. I think the high end tweeter sounds good. I'll follow up with results. Just a thought, as far as drivers I would keep the mid and tweeter but the 8 in woofers are probably the weakerst link there. They are a bit slow and do not have a ton of detail? Are there any good 8in drivers I could try? Seas?

[jimbones]

he C2 that goes before R1 with decent film caps" Don't you mean C3?

[5th element]

Hmm C3 doesn't exist for me at all in the service manual for the DM640. The manual for the DM640i however does list C3.

I'll do this the easy way.

DM640.



DM640i.



The 640i lists C3.

There's nothing inherently bad about a good quality electrolytic although most will claim that foil sound better. Foil certainly have the advantage of stability vs time, but can end up costing a lot for large values. C5 in both designs is quite large in value and would represent a decent cost. You could go lytic here for the majority of the capacitance and parallel in a foil for the remainder.

As abraxalito states, there is nothing wrong with going active, but to do it properly will require certain expertise and most likely certain hardware upgrade too.

The bass qualities you speak of could be due to a lot of things and are unlikely to be caused by the bass drivers them selves. The subjective description of slow bass could be caused by room interactions with the loudspeakers or could stem from poor room integration because of the alignment the boxes are tuned to. The loudspeakers are ported, I take it you've tried stuffing the ports with a sock or moving the loudspeakers around a bit?

[abraxalito]

Originally Posted by jimbones

the 8 in woofers are probably the weakerst link there. They are a bit slow and do not have a ton of detail?

Don't blame those drivers so fast. Certainly not before you've chucked that 5mH ferrite-cored fount of distortion for something a tad more transparent

[5th element]

Originally Posted by abraxalito

Don't blame those drivers so fast. Certainly not before you've chucked that 5mH ferrite-cored fount of distortion for something a tad more transparent

I think your probably over emphasising the effect that the inductor could be having on the sound. There is nothing wrong with using cored inductors providing they are of decent design and aren't over driven.

[jerome69]

I will not tweak the B&W DM640. According to your feeling, you could have a problem with your electronic, amplifier, source ? Your amplifier can't supply correctly the 2x8inch ! A 8 inch is fast in the bass !
Try a better amplifier first and after if necessary a better CD player ?
Note for me a good amplifier looks like this :
Sugden A21ai Series 2 integrated amplifier | Stereophile.com
Accuphase Laboratory, Inc.?E-250
etc.
You can do it yourself or test...

Or
Change the speaker, go to a 8 ohms, one with a 10" ?
Make a proven design :
Jenzen CA
You can wait for a "better" version with high end drivers.
There are other design on his website ...

Originally Posted by jimbones

Right on. I am doing the XO ordering parts today. Thats funny how you picked up the mid being a little lod abraxalito. I was thinking it but was not planning to do anything. I'll now have to consider that. I think the high end tweeter sounds good. I'll follow up with results. Just a thought, as far as drivers I would keep the mid and tweeter but the 8 in woofers are probably the weakerst link there. They are a bit slow and do not have a ton of detail? Are there any good 8in drivers I could try? Seas?

[abraxalito]

Originally Posted by 5th element

I think your probably over emphasising the effect that the inductor could be having on the sound. There is nothing wrong with using cored inductors providing they are of decent design and aren't over driven.

Well I didn't say anything about whether its 'wrong' to use cored inductors. As you pointed out those designs are over 20 years old, they even pre-date my time at the company. They're just not very transparent, having easily measurable distortion (so I'm led to believe, not having passive speakers with ferrite cored inductors around to test myself). More recent B&W designs tend to use air-cored inductors where possible (like my own CM1s) or at least a core material appreciably more linear than ferrite.