Dynaudio Focus 110 and 140 Crossover Comparison Details

[johnmath]

Yes, that's correct. The basic principle is described in the Canare document linked below. I think the original patent on star-quad wiring dates back to the 1880s before the invention of coaxial cable; patented by Marconi or Nicola Tesla and used by Marconi to couple his antennas. Oddly enough a certain Michael Wollitzer has recently applied for patents on the principle, even though it has been in common usage for over 100 years!

Canare omit to mention that 2 conductor loudspeaker cables can make air coupled transformers, although that is implied. I've had professional multi-driver steered arrays, like those used in Parliament House Canberra, have their directional patterns completely screwed up by magnetic coupling due to incorrectly constructed speaker looms.

http://www.canare.com/UploadedDocuments/Star Quad - Speaker Cable.pdf

 

[stephen00]

Great info, John!

 

[oloppolo]

Stephen, I popped open the Focus 110s today to see what I had done. I generally can’t fault Dynaudio crossover designs so all I did was the standard upgrades I do to Dynaudio loudspeakers of the Audience, DM and Focus series. For the Excite series I do change the crossover configuration back to traditional Dynaudio first order topology for its superior time domain response and in-room power response.

The bass driver low pass inductor was replaced with one that has a DCR of <1/20 of the DCR of the bass driver, which in this case is 3 ohms, so the target for the inductor is less than 0.15 ohms. The original is 0.41 ohms. I usually would use an air-cored inductor, but I doubt if the ones I used for my Focus 220s would fit through the opening of the F110 bass driver. I used a Jantzen P-core part number 000-5144 1.2mH / 0.14 ohms inductor.

Electrolytic capacitors should be replaced with audio grade film capacitors. It’s a misnomer to think capacitors in bypass locations don’t need to be audio grade; after all it is audio they are bypassing and if they fail to do that well it will be audible! I can’t remember if I replaced the capacitor in the bass driver Zobel network (R1 and the 15uF capacitor) but it has a Solen metalised polypropylene in there, the same as other capacitors Dynaudio have used.

I didn’t change the 27uF electrolytic because when I did these years ago. I mistakenly thought it was an out of band equalisation network to make the load impedance seen by an amplifier benign above 20kHz. It isn’t; it’s a frequency shaping network so it needs to be changed and I have ordered Dayton DMPC polypropylene capacitors for that (they’re a little smaller and it’s a tight fit).

The tweeter rear chamber is resonant at ~2kHz and needs damping, so I plugged the dimple and covered the rear with a stick-on constrained damping material, like that used in cars behind speakers. Leave the tiny vent hole in the back uncovered so the tweeter diaphragm can adjust to changes in barometric pressure.

I don’t change the other small inductors in the tweeter circuit as their series resistance is already factored into the crossover tuning and to change them would upset it.

In the larger cabinets it is beneficial to add damping to any resonant areas of the cabinet, but there’s not much untreated cabinet wall surface left to damp in these little boxes, so I didn’t add any.

Nor did I upgrade the internal wiring as it is quite substantial anyway. For the F220s I replaced the internal wiring with Canare 4S11 (for input) and 4S8 (for drivers) star-quad speaker cable wired for inductance cancelling, as this prevents the leads becoming loosely coupled transformers with each other or anything else, and significantly reduces any microphonic contribution from the cables.

Now that I think about it, when the capacitors arrive, I will replace the woofer and tweeter leads with Canare 4S8.

The final tuning that Dynaudios benefit from is seriously good leads to the amplifier, and good amplification. My preference is Canare 4S11 for leads up to 4 metres or so. That gives 4mm2 of oxygen free long crystal copper per side, PE insulated in a mechanically constrained construction. Properly wired in star-quad configuration it has minimal external magnetic field, and low microphonic interaction. And it’s not expensive, but hard to beat.

Thanks Johnmath for your advice. My Dynaudio Foccus (Dynacar woofer and D28) have a similar crossover design as the Focus. L1 is 0.9 mH. I will make the changes.

 

[angulon]

Hello to all,

I have been reading this very exciting thread for a few days now. I too own the Dynaudio Focus 110 - with which I am basically very satisfied - and in addition to the internal wiring and the replacement of the speaker connections, I would also like to replace a resistor and a capacitor. I am convinced that the speaker will improve even more in terms of sound.

For the internal wiring I will use 3 to 4 copper strands each from my old Audioquest Midnight 3. I will remove the outer sheathing of the cable. The new connections will be made of copper.

Afterwards I want to change some things on the capacitors and on a resistor. As far as I can see, C3 and C5 each have 6.8 uF capacity, C1 has 15 uF and C2 has 4.7 uF.

However, I am not sure which capacitor sits directly in front of the HT, which I either replace completely or solder a small but noble capacitor in parallel.

Maybe one of the experienced forum members can help me out. I can't see the wood for the trees. The same goes for the resistors R1 to R5. Which resistor sits directly in front of the HT?

Thank you very much for your support and best regards from Germany.

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