Dynaudio BM6 monitors crossover

[gilwe]

I want to turn a pair of active BM6a into passive monitors, at least temporarily.

It's easy to just remove the back assembly with the amp, which leaves a connector that goes to both tweeter and woofer.

The BM6a (active) specs say the crossover point is at 2.2Khz, with the amp being 100W:
Dynaudio BM6A. User manual. English. Technical Specifications

Would I achieve good results using a cheap 2.2Khz crossover such as this one?

Or does it need anything special?

SHEVCHENKO Pure Tweeter Speaker Crossover 2.2KHz Treble Frequency Divider For 4 8 Ohm Home Audio Tweeter Unit 2pcs|Amplifier| - AliExpress

Here are the specs of the passive model:

Dynaudio Acoustics BM6 - 2-way passive monitor system

 

[Galu]

Or does it need anything special?

From the passive BM6 specs:

Crossover frequency: 3100 Hz

Crossover Slope: Woofer 6 dB/octave; Tweeter 12 dB/octave

The Shevchenko crossover only gives the tweeter crossover, you need one which filters both tweeter and woofer in the way described by the above specifications,

 

[Galu]

Having said that, and seeing as you are considering a temporary setup, you could use the Shevchenko crossover and just let the woofer run unfiltered.

Not optimum, but you won't damage anything!

 

[GeoffMillar]

The spec sheet for those says that the woofer has a first order filter - i.e an inductor - and a second order tweeter filter: a cap and inductor and most likely a resistor or L-pad.


I'd try and find out what the parts values are and build a clone of that, rather than use a generic crossover. They don't sound good in almost any application and I would think this would be the case if using the speakers as monitors.



Or, if you can't find the parts values, if you know the drivers' specs you could have a go at designing and simming a crossover.

Geoff

 

[woody]

Might want to look at the specification sheet again. I believe it says it's using a 4th order phase corrected crossover.

 

[GeoffMillar]

I took it from this page:

Dynaudio Acoustics BM6 - 2-way passive monitor system


"Crossover Frequencies:3100 HzCrossover Slope:Woofer 6 dB/oct; Tweeter 12 dB/oct"

Although that's for the BM6, not the active version, so I may well be wrong - thanks for the correction


Geoff

 

[woody]

But the speaker he has the BM6a uses the 4th order active xover. Dynaudio BM6A. User manual. English. Technical Specifications

 

[Galu]

But, his aim is to convert it to the passive version.

 

[gilwe]

Thanks, that's exactly what I want to do. Remove the amps and convert the monitors to BM6P (passive).

The following thread has some closeup pictures of the BM6P crossovers, can this help in any way?

Dynaudio BM6 Passive Schematic

 

[Galu]

I've copied the crossover board image over to this thread for ease of reference.

 

[system7]

That one caught fire didn't it? Overdriven.

4 ohm woofer it seems. Loads of ways to do it.

Lojzek came up with this;

This filter should do reasonably well for the 17W75xl-4 and D28/2.
woofer 2nd order electrical lp filter: 1mH; 15uF
tweeter 3rd order electrical with padding before x/o: 4R7; 6.8uF; 0.22mH; 10uF

Modify padding resistor to better suit your taste.

https://www.diyaudio.com/forums/multi-way/368990-dynaudio-17w75-xl-d28-2-crossover-bass-reflex-help-2.html#post6640112

 

[gilwe]

Is there any aliexpress or ebay shelf product that could fit exactly to those BM6's so it matches the specs?

 

[GeoffMillar]

I doubt it, as the 'off the shelf' crossovers from PE or anywhere tend to use the same parts values for tweeter and woofer, although their positions in the circuits are reversed of course.

I did a lot of research on this when looking to build my first speakers as I couldn't solder, but it was impossible to find a ready-made crossover with the right parts.

The suggested circuit seems pretty straightforward and would sound heaps better than a generic one. Do you know anyone who could help you put it together?

Geoff

 

[system7]

The AliExpress crossover isn't ideal IMO.

You can use a Zobel on the bass, 4.7R and 15uF:

That's a first order tweeter with a small 6.8R/1.2uF zobel thrown in. I would guess Rs is 4.7R. Won't be hard to build on a piece of timber. Use hot glue or zip ties and solder the joints. Might as well buy aircoils for the inductors.

The two circuits on the right won't be needed. They are for valve amps I reckon. But I'd trust Lojzek. He's good. He builds this stuff.

Use 10W resistor on the bass. 5W will probably do for the tweeter circuit. Parts Express or Madisound.

 

[Galu]

Is there any aliexpress or ebay shelf product that could fit exactly to those BM6's so it matches the specs?

Until such times as you are confident about building your own crossovers you could get your project up and running with these inexpensive two-way crossovers from AliExpress: AIYIMA 2Pcs Bass Treble 2 Way Crossover Audio Board Fever Speaker Frequency Divider Crossover Filters For KASUN Home Theater|filter sticker|filter anthracitefilter foam - AliExpress

However, it must be stressed that the crossover design that was suggested earlier is fairly simple to build.

Here's a reminder of the suggested crossover as attributed to Lojzek:

Woofer 2nd order low pass filter: 1mH; 15uF
Tweeter 3rd order filter: 6.8uF; 0.22mH; 10uF (An attenuating resistor is required in front of the tweeter crossover components - suggested value 4.7 ohm)

Schematics attached.

 

[system7]

You forgot the resistor to adjust tweeter level, Galu...

See that 3.3R in red on this creation of mine?

Looks a bit like this:

Many interesting skills were acquired in building it. Soldering, wiring and all that. Here's that Dynaudio circuit I looked at pictured below.

 

[plasnu]

Have you measured the woofer and tweeter? I think that all Dynaudio woofer has a dip between 1-2K, and you may want to deal with it if you still want to use it as a rather accurate studio monitor.

 

[Galu]

You forgot the resistor to adjust tweeter level, Galu...

(An attenuating resistor is required in front of the tweeter crossover components - suggested value 4.7 ohm)

Your statement is demonstrably untrue!

This all must be very confusing for gilwe. He obviously has no experience in building crossovers and is being presented with a confusing number of options.

I tried to keep it simple for him, but I doubt that we'll hear from him again.

 

[system7]

I hope we don't drive anyone away. Just some folks give up because it all looks too difficult.

But is it. Here's what was originally in my Monitor Audio R300-MD.

Circuit like this:

Below is one of my similar experiments. But really you might fit one of those larger 4 terminal biwire speaker sockets. There's more room on them for bigger circuits.

Speaker Cup, Gold Plated Bi Wire Terminals | HIFICollective

 

[gilwe]

hey guy, thanks for your assistance!

I'm highly experienced with building circuits, no worries

Only that as you said, you came up with different component values and options. What would be closest to the original BM6 (passive) crossover?

I you give me a diagram and component values that would be the best fit, then I can build this easily

But if the suggested design isn't close enough to true BM6 (passive), then maybe I should just go for a passive pair of monitors...