My reverse engineering of a Dynaudio Audience 52

[mr_push_pull]

for those interested in only the DIY part of it skip the italic section

a fortunate (IMO) coincidence made me take a look on the local audio forum's advertisement section and that ended up in my buying a pair of used Dynaudio Audience 52 speakers the next day. they have been optically damaged. most likely they have been dropped during transportation to my previous owner which resulted in cracked edges and also both tweeter domes have dents. which is kind of weird considering that the material is some kind of rubber treated fabric - not rigid that is - and it should restore itself to original shape. any idea what might have caused the permanent dents?
considering that they used to cost EUR 800 new (now out of production) and that I couldn't find anything wrong with them sonically I think I paid a good price - EUR 300. maybe many would think that's too high considering the physical issues they have, but the sound is rewarding, detailed yet not forward, exceptionally good soundstage (wide and deep), decent bass and overall very musical and neutral IMO. I know that there are many decent bookshelves that sell for even less than that price but in my town there isn't any dealer so the occasions for listening tests are scarce so I preferred to buy these which I was acquainted to. and I'm satisfied with my decision and I get to DIY on them a bit too...


now... for the DIY part. they sound waaaay superior to my DIY Morels (see thread here http://www.diyaudio.com/forums/mult...parts-zaph-seas-l18-seas-27tbfcg-speaker.html).
but I'm going to experiment a bit.
first I'll reverse engineer everything and post everything unless the mods think I shouldn't meaning box params, filters, drivers and box measruremets (now why did I sell my ECM 8000?).
then I'll restore them, re-veneer and cover the baffle with leather imitation.
but first... I'll just replace the tweeters with my MDT32S Morels just out of curiosity, maybe they work. I haven't measured the Dynaudio tweeters (only Re which is nearly identical) but who knows?
fortunately the face place diameter is nearly identical (less than 1 mm difference). I just need to drill 3 more holes (the offset of the mounting holes is slightly larger on the Morels) and that's it.
in the end this will be my reference for tweaking the Morels and getting them to sound better. I want to understand how Dynaudio did it. after all Vance Dickason himself says that one needs to have a reference.
will get back with more pics and reports on the replacement later.

 

[bzfcocon]

first I'll reverse engineer everything and post everything unless the mods think I shouldn't meaning box params, filters, drivers and box measruremets (now why did I sell my ECM 8000?)

What exactly is the purpose of the reverse engineering ? Just to know how Dynaudio did it or do you want to make a clone ?

then I'll restore them, re-veneer and cover the baffle with leather imitation.
but first... I'll just replace the tweeters with my MDT32S Morels just out of curiosity, maybe they work. I haven't measured the Dynaudio tweeters (only Re which is nearly identical) but who knows?

Replacing the tweeters in the hope that "maybe they work" is always a bad idea IMHO. First, the chances to get a good "blind" match with the new tweeters are nearly 0. Second, the tweeters in the Audience 52 are excellent ones anyway, I bet they sound very good even with the minor defects. So what's the point of putting in new tweeters ?

I want to understand how Dynaudio did it. after all Vance Dickason himself says that one needs to have a reference.
will get back with more pics and reports on the replacement later.

If you change the tweeters, your reference will be gone, right ? As to how Dynaudio did it: you should think about buying back that ECM8000

 

[ashok]

I think you will need to stick to the same Dynaudio tweeters.I'm quite sure the Morel's will not sound the same. It isn't just a matter of impedance. Look it up, there are lots of parameters involved .

You could possibly ignore small dents as it shouldn't make too much of an audible difference.
How do I know ? Well two friends bought the same Dynaudio's a few years ago and one guy had both tweeters very badly dented ( pushed in !) on two different ocassions. We pulled out the dent very gently using a masked vacuum cleaner. There was still a visible dent but it sounded fine. The dent is still there today ! Maybe measurement will reveal some differences but it does sound OK to the ear.

First thing to do if you do use the original tweeters is to change the crossover to a biwireable scheme. So track cutting on the board will be required and you need a biwireable speaker connector panel. We found it sounded better biwired. If anyone objects , please refrain from comments till you try this out on these speakers yourself. I've done this to my Mission701's and it made an audible difference.

You could also upgrade by using better capacitors on the crossover ( change all bipolar types also) and change any ferrite cored coils to air cored coils. Maybe you can do it in stages to see how each change affects the sound. Unfortunately I don't have a record of what parts we actually used. It was about 10 years ago.

 

[bzfcocon]

You could also upgrade by using better capacitors on the crossover ( change all bipolar types also) and change any ferrite cored coils to air cored coils. Maybe you can do it in stages to see how each change affects the sound. Unfortunately I don't have a record of what parts we actually used. It was about 10 years ago.

While I would (partially) agree with changing capacitors for better ones, I would be much more careful about changing the coils, as this can influence the speaker's voicing significantly (air coils usually have higher series resistance that ferrite coils). But you have to try and see (I mean hear).

Again, if what you need is a reference, then doing any changes to that reference will obviously bias it.

 

[mr_push_pull]

guys, I would say you're over-reacting and I really can't understand your views.
it's not like I said "I'm going to throw the Dynaudio tweeters and stick with the Morels even if they sound horrible". this is just an experiment and while I agree that there is a very slight chance that this will work (tweeter Fs, L, SPL, overall response, response roll-off etc) I don't think I have anything to lose. I think I'm able to drill 6 holes in the Dynaudio enclosure without destroying it. I can revert back in 5 minutes and that wouldn't affect it in any way, esthetically or sonically.
you may look at this whichever way you want, maybe I'm wasting my time but hell, building the Morel speakers was a waste of time considering the results.

quoting Vance Dickason again (I actually read his book, at least the portions I was interested in) he says that it's hard to tell whether going for flat response or minimum phase affects sounds most. maybe one thing I want to find out was if Dynaudio aimed for both or only only one of them. I have a pre-built speaker that sounds good and I'm using it to try to understand why it sounds good. and part of that is understanding what makes it sound worse most.

my DIY speakers with Morel drivers measure almost flat with the ECM 8000 ( I'll post the measurements as soon as I install ARTA again) but they sound mediocre compared to the A52. also, overall impedance was equalized.

PS: of course I'll use a mic to measure response but this time it won't be the ECM8000. I kind of distrust its advertised flatness. I'll be better off with a cheap Panasonic capsule. after all even Siegfried Linkwitz uses it.

 

[sreten]

Hi,

You should thoroughly analyse the design process of the Morels
and find out what went wrong, there will be good reasons.

FRD Consortium tools guide

rgds, sreten.

undefinition
Zaph|Audio
RJB Audio Projects
Speaker Design Works
HTGuide Forum - A Guide to HTguide.com Completed Speaker Designs.
Humble Homemade Hifi
DIY Loudspeaker Projects Troels Gravesen
Quarter Wavelength Loudspeaker Design
The Frugal-Horns Site -- High Performance, Low Cost DIY Horn Designs
Linkwitz Lab - Loudspeaker Design
Music and Design

 

[speakerdoctor]

Hi,

You should thoroughly analyse the design process of the Morels
and find out what went wrong, there will be good reasons.

FRD Consortium tools guide

rgds, sreten.

/QUOTE]

Here's another link on speaker building that may be of help.
The Speaker Building Bible - Techtalk Speaker Building, Audio, Video, and Electronics Customer Discussion Forum From Parts-Express.com

 

[mr_push_pull]

surgery succeeded.
I'm planning to do some more listening tomorrow but initial impressions are that something definately changed.
soundstage is still very good but I get the impression that some frequencies are smeared over the stereo image. also, I think, that I can hear some something that sounds like resonances.
if the tweeters prove to be similar in parameters and response it would mean that I understand what the renowned sweetness of the Esotec tweeter means. most seems to be lost in the sound of cymbals that now sound somehow like synthesized ones.

 

[MarkT]

It might be interesting to see how the crossover design differs from the old dynaudio 'foccus' kit, which used similar drivers: see Dynaudio archive (and scroll to the bottom of the page!)

 

[mr_push_pull]

here's some more details.

total box volume is 9.9 liters. subtracting drivers, crossover and port volumes let's approximate it to 9 liters. port is 120 mm long with an ID of 45 mm and flared at both ends. it's made of 19 mm MDF without any internal bracing whatsoever. there's bitumen lining on both side walls and a generous (and I do mean it) amount of foam and artificial wool lining.

the woofer looks pretty modest and the basket is not cast as I had expected at this shelf price (EUR 800, remember). the woofer section of the XO uses a ferrite core inductor. there's a bipolar Bennic cap on the woofer zobel (see pic). cabling is nothing special. no gold plated connectors, even my Morel drivers have them.
overall it looks like Dynaudio is taking all possible cost reduction measures. I did not expect this considering the price level. except the drivers which I have no idea how much cost to make (not much I would guess), the box plus XO looks to cost around EUR 50 or less to manufacture. it looks like with Dynaudio you're actually paying the research, marketing and the actual result, not the costs involved in production. nevertheless I think they make great speakers.
OTOH, considering the sound quality alone and disregarding the price, one could say that they make very down to earth decisions as to what to spend money on. if they used the Bennic and generic MKT caps maybe it means that the drivers are only revealing so much.

I'll measure the woofer T/S parameters when I get the chance.

I'm attaching a drawing of the XO (excuse the quality, I held the paper on my lap while drawing it) and a few other pics.

 

[mr_push_pull]

some more progress, FWIW.
I decided not to wait till I won't have time to do it - going back to work soon - and I took apart an old cassette player just to take out the electret mic. some 3 hours later I had a measurement gig ready to fire.
now, I had no reason to expect that capsule to be flat and so it wasn't. comparing the far field measurements of the Morels to the ones from the days when I still owned the ECM8000 it looks like there are some nasty rises and drops above 2k. but at low frequencies it looks to be pretty much flat and even at high frequencies its useful if just a relative measurement is needed (like in my case).
both speakers are closer than I expected but still there are notable differences. I'll list the differences which I think to be most important:
- the Dynaudios use BSC (like I expected)
- the Dynas don't have the large 3dB drop at 1k that the MW144 has (clearly visible in the datasheet here http://www.morelhifi.com/products/pdf/mw144.pdf and also in my measurements)
- the Dynas have the treble rolled off some 2dB
- the Morel MDT32S tweeter has a large peak (almost 5dB) at 14kHz; audability is questionable though
- the crossover point is almost identical on both speakers - around 4k (based on reversed tweeter polarity measurements)
- the tuning frequency of the Dynas is identical to my speakers, ~50Hz (calculations give ~60Hz) although mine seems to have a larger Q
and most important and somehow surprising: unfiltered responses of the Morel and Dyna woofers is almost identical and I think the Morels would be happy with first order filtering on woofer too; the only major difference is the dip I mentioned earlier

I already attenuated the treble on the Morels a bit to get closer to the Dynas and the next step would be to add BSC. who knows, maybe I'll do it tomorrow? impedance plots will follow soon too.

 

[mr_push_pull]

T/S parameters of the Dynaudio woofer (measured with LIMP):

Fs = 46.70 Hz
Re = 3 ohms
Le = 435.1 uH
Qt = 0.40
Qes = 0.48
Qms = 2.28
Mms = 11.99 grams
Rms = 1.545565 kg/s
Cms = 0.000969 m/N
Vas = 19.22 liters
Sd = 118.82 cm^2
Bl = 4.679587 Tm
ETA = 0.39 %
Lp(2.83V/1m) = 92.28 dB

overall impedance of the Audience 52.