Crossover Designs without Capacitors

[musicfirst1]

I fondly remember Franko Serblins Extremas which utilized a crossover without capacitors. Just a power resistor in series and an Inductor in parallel with the Dynaudio Esotar tweeter.

The speakers were amazing sounding, but notoriously inefficient, in no small part because of this crossover design.

Are there any other contemporary designs using this methodology?

 

[marmota]

This one from Troels:
http://www.troelsgravesen.dk/Ellipticor-3.htm

PS: However, more than a crossover without capacitors, I would like to see a crossover without resistors (Lampizator OB speakers don't use resistors btw, but I couldn't find more "resistorless speakers").

 

[Site7000]

Doesn't the Wilson-Benesch line of speakers, or at least the better ones, have their midrange drivers hooked up directly to the amp without crossover of any kind?

 

[Sablon Audio]

Doesn't the Wilson-Benesch line of speakers, or at least the better ones, have their midrange drivers hooked up directly to the amp without crossover of any kind?

Yes, that is correct. The midrange drivers on my ACT are driven directly with a mechanical frequency roll-off. Bass driver just has a simple inductor. Ref 3A and Diapason also use this approach, though this is different from the sine cap xo.

 

[DaveC]

This one from Troels:
http://www.troelsgravesen.dk/Ellipticor-3.htm

PS: However, more than a crossover without capacitors, I would like to see a crossover without resistors (Lampizator OB speakers don't use resistors btw, but I couldn't find more "resistorless speakers").

I agree, resistors in series are more of an issue as we have some pretty good caps these days. Since inductors and caps can act as frequency dependent resistors it is possible in some cases to use caps to attenuate, this is how I have implemented the xo for the tweeter in my speaker.

 

[shakey]

The crossover in my Bache Audio Tribeca's is a simple cap on the super tweeter and a coil for the woofers. The modified wide band driver is a direct connection to the amp. In the past I have had speakers with complicated crossovers and single-drivers with no crossover. These are my favorite speakers so simple does it for me.

 

[marmota]

I agree, resistors in series are more of an issue as we have some pretty good caps these days. Since inductors and caps can act as frequency dependent resistors it is possible in some cases to use caps to attenuate, this is how I have implemented the xo for the tweeter in my speaker.

Great approach!

Tony Gee's Plutone speaker also uses a similar, clever trick to tame the tweeter without resistors:
http://www.humblehomemadehifi.com/download/Humble Homemade Hifi_Plutone.pdf

"The series capacitor is smaller than usual and the parallel inductor is larger than usual. This means that the capacitor starts to work at very high frequencies but the inductor doesn't start until about 2kHz. The result is that the natural hump from 2-10kHz is flattened and then below 2kHz where the tweeter needs some protection it has a full second order network. The small capacitor value also increases overall power handling. "

I would love to see a 3 way resistorless speaker that is aperiodic (with multiple holes on the back) to achieve a flat impedance (and high, around 16 ohms). With the right (and high efficiency) drivers, 6-8 parts per speaker crossover may be doable. Something like that would be incredible if properly done and paired with a nice, well build tube amp.

 

[musicfirst1]

I guess it's just me but DC/capless amplifiers from stem to stern folllowed by a cap, often the size of a hand grenade, seems counter intuitive IMHO.
The Extrema was very resolving I'm sure in part to the 'sine-cap' crossover.

Conventional first-order high-pass crossover filter (top) vs "Sine-Cap" filter (bottom).
C Stereophile Extrema Review... Martin Collums review. Jun 7, 1992

For those interested to read further:

https://www.stereophile.com/standloudspeakers/915/index.html

 

[DaveC]

I guess it's just me but DC/capless amplifiers from stem to stern folllowed by a cap, often the size of a hand grenade, seems counter intuitive IMHO.
The Extrema was very resolving I'm sure in part to the 'sine-cap' crossover.

Conventional first-order high-pass crossover filter (top) vs "Sine-Cap" filter (bottom).
C Stereophile Extrema Review... Martin Collums review. Jun 7, 1992

For those interested to read further:

https://www.stereophile.com/standloudspeakers/915/index.html

Many folks often try to design their tube amps without any resistors (or caps) in the signal path. IME, it makes a larger difference for small signal vs speaker level.

In any case, both caps and resistors will add something to the sound, not sure one is that much more preferable vs another. For some tweeter applications that would typically use resistors to reduce output and caps to highpass, you can sometimes do both with a cap alone, in combination with an inductor in parallel or not depending on slope desired. I would not attribute the "very resolving" part to using a resistor vs a cap, that just isn't the case assuming both are of appropriate quality.

 

[analogsa]

couldn't find more "resistorless speakers".

Not sure if it qualifies, but the ancient Rogers Studio Monitor only used a single resistor for padding the supertweeter. The rest of the crossover contains chokes and caps and importantly, an autotransformer (the biggest piece of iron in the pic) instead of resistors.

 

[Robh3606]

I would be a little concerned not having a capacitor in series with a compression driver as an example. All it can take is an unexpected turn on thump from an amp and you have DC right into the driver. Could be a very expensive lesson especially if you are running Be diaphragms. I don't really see issues with modern film capacitors.

Looking at the schematic of the HF section you don't know what the DCR value is for the shunt inductor. It could easily be wound with a deliberately higher DCR value so it functions not unlike a conventional resistor pad.

Rob

 

[analogsa]

I don't really see issues with modern film capacitors.

Apart from the fact that they all sound different I agree, no issues

The automatic protection against DC granted by capacitors is indeed gone, but if it were a decisive factor it would also discourage the use of active sytems and dc coupling in general. And there is always the option of transformer coupling...

 

[Folsom]

I don't think capacitors are evil. But if your system has flaws then they may exemplify some of them. In otherwords sometimes "better" caps wash over problems better than others. Personally I find they can often stop problems as well by being inserted in series, in electronics.