Dynaudio identification help required.

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Hi Guys.

I've been handed a pair of active floorstanding Dynaudios to refurbish.
The new owner and I have no idea what model they are.
He says there 2002 vintage, but I'm not sure if they aren't older than that.
If someone here knows what they are or has any info on them, and would like to share, that would be fantastic.

Bass driver is 24w75
Tweeter D28 / 2

Other than the Dynaudio label on the heatsink, there are no other markings at all.

List of jobs to do.

Tweeters.
Measure and sound very different from each other, so new diaphragms have been ordered.

Bass drivers.
New surrounds have been ordered. Current ones are way past use by date (gooey and lots of tears), and were very poorly installed to start with.

Electronics.
Power supply and amplifiers need rebuilding.
Fix someone's previous repair work. Fix the faults (no power up, burnt boards and resistors). Full recap.
The one I've shown here is in better shape than the other one.

Finally, a full rewire of the cabinets.
 

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I've got the old Dynaudio catalogue. Significant is that the Qts of the bass is around 0.8. The rest is self-explanatory. Usual well-controlled natural rolloff.

The D28-2 is about 89dB efficient, IIRC. Plenty of well-documented tweeter circuits around. I have no idea what the electronic circuitry is for. Protection or active drive or both?
 

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Ouch. Nice burned resistors on the amp. Look up that circuit board and the PS as well, otherwise it's depopulate, repair and replace time. Doesn't look too complicated. If the owner doesn't care about originality, you could go passive or dsp w/modern amps, with modern measurements.
 
I've got the old Dynaudio catalogue. Significant is that the Qts of the bass is around 0.8. The rest is self-explanatory. Usual well-controlled natural rolloff.

The D28-2 is about 89dB efficient, IIRC. Plenty of well-documented tweeter circuits around. I have no idea what the electronic circuitry is for. Protection or active drive or both?

Thanks Steve. Thought you'd have some info.
The circuit is two amps and active crossover.


Ouch. Nice burned resistors on the amp. Look up that circuit board and the PS as well, otherwise it's depopulate, repair and replace time. Doesn't look too complicated. If the owner doesn't care about originality, you could go passive or dsp w/modern amps, with modern measurements.

Yes. lots of damage to both sides.
I did discuss converting them to passive crossovers, but he'd like to stay active.
So it will be strip, repair, rebuild, with a few minor mods.
Mainly uprating the burnt or heat affected parts.
The burn on the power supply is a bleed resistor. So obviously a minor re engineer of the power supply is also going to happen.

I'm going to do a post in the solid state forum to see what info they can give me for possible improvements to the amp modules.
 

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One of the things that drew my customer to these was being able to plug his pre into them and no setting up needed.

I did see a 2 channel dsp amp, but i think the cost and set up would exceed what hes after.

So far the combined parts list is substantially below what a single dsp setup costs.
 
For those playing at home.........

In my thread in the solid state section regarding the amplifiers.
Well, the amps are history.
The boards won't allow repair or rework, they just fall apart at the touch of a soldering iron.
Currently in discussion with the owner as to what he wants to do in that regards.
I.E. passive conversion or an ice/mini dsp plate amp swap.


I sent Dynaudio an email asking if they had any info about these.
They got back to me today.

They passed the photos around and no one knows these speakers.

Their best guess is they were one of their very first active speakers built around late 70's early 80's.
They can still supply drivers, which is pretty awesome in it's self, but that's the end of what they can do.

Otherwise the owner and I are still in discussion as to the next step.....
 
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Too nice to throw away, for sure.

Looking at the scorch marks, the electronics was insufficiently ventilated. Sort of issue you'd run into with a near prototype.

With the low price of second-hand amplifiers in junk shops, I'd think that going passive is a very real possibility. My own view, is that if you design for easy impedance, you really don't need any exotic amplifier for a very good sound.

And you do that by using an old BBC BW3 design like the LS5/9:
Rogers Loudspeakers › LS5/9

This speaker is still made, and still sounds good. It uses passive RL bafflestep and impedance correction: mh-audio.nl - Home

Just calculate for BW3 and 10R bass and 6R tweeter and 3500Hz, and the values drop out: 2-Way Crossover Calculator / Designer

But it's down to your friend really. FWIW, I believe the D28-2 is a ferrofluid design, so an oil-change might be in order.
 

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Looks like your client is stuck between a rock and a hard place, and Steve is right that the enclosures are too pretty to throw away. The amps appear to have suffered the same fate as many plate amps on commercial powered subs over the years - inadequate thermal dissipation - and there's often no affordable option other than to replace. This is certainly the type of failure mode that makes outboard amplification very appealing. It may well be too early to conclude that the higher efficiency class D amps that are currently in vogue are categorically immune to the same system design oversight.

MiniDSP offers a couple of models of ICE powered plate amps with full DSP functionality, and Parts Express' Dayton brand have lower cost - but far less flexible - options as well.

Full-Range Plate Amplifiers in the Speaker Components Department at Parts Express | 333
 
Lojzek, to clarify, do you mean internal passive XOs with a single outboard stereo power amp, or something else?

OnC - I'm not sure it's been made clear yet, but was the lower section housing the amp a completely isolated enclosure? If not, and if those are vario-vents for porting of woofer section seen above the heat sinks, completely removing the amp modules could have an impact on the net volume for which the system was tuned. Perhaps not a huge factor, but worth keeping in mind.
 
AFAIK, the woofer is high Qts around 0.8. So you really can't give it a box that is too big. Almost a car parcel-shelf woofer.

I am sure Lojzek means a stereo amplifier and a passive crossover. TBH, that design (attached) looks a knockout! :D

What is special about it Lojzek? TBH, I prefer to leave these things to Rotel and Sony and such. The main problem with Class AB is that everytime it switches from plus to minus, you have to pass through the power transistor switching, which introduces a little discontinuity and a blip of noise. It's quite easy to design an average amplifier with lots of compensation on the feedback, but hard to design one that is fast but stable.

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This is the 20wpc output stage of my competent Rotel RA-931 amplifier. A Class AB design from about 20 years ago and still going strong. It's the switches that get a bit vague over time, and need a clean with an aerosol switch cleaner.
 

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Yep. Way too pretty to let die in a dump or corner.
Of that both the owner and I agree.

I've redone the tweeters. Didn't touch the fluid. Looked ok.
On DATS sweeps they now measure within spitting distance of each other and sound identical. As far as I can tell anyway :)
Could be placebo but I'm sure they sound smoother and a little more extended.
One tweeter originally sounded low and distorted.
I'd imagine damage to the voice coil when the amp died.

If he decides to go passive, I was going to do it right.
Mic'd sweeps and go from there.

If he goes for the active dsp plate option.
Well, I'll still have to do mic sweeps and listening tests.
But then I can play with settings through a pc...
Should (HA) be a faster process.

EDIT.
sorry, the vario vents...

three chamber cabinet.
very bottom of cabinet is a sealed enclosure purely for the electronics.
next section up has two vario vents through the back wall to the outside world.
This section also has three vario vents into the main upper cabinet that houses the bass and tweeter.
 
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What is special about it Lojzek? TBH, I prefer to leave these things to Rotel and Sony and such.


What's special is that it performs better than Rotel 931 and I happened to own one, it has built in automatic current limit while output short circuited or heavily overloaded, DC voltage protection and turn on delay, current mirrors below differential amp, electronic input switch and I get to feel good that I managed to put together some electronics.

I agree it's not essential if you can live with any decently built commercial amp and Rotel counts for sure. I even have the same tuner 935 AX.

@chrisb: Sure, I meant stand alone stereo amp and internal passive crossover filter as usually found in passive speakers.
 
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