How much does a Zobel network and its components affect the sound of speakers?

A few thoughts about the Merlin RC Networks (or Zobels).

Merlin made two types of RC’s. The “Standard RC” was made with the Hovland cap and the Caddock resistor. The “Master RC” was made with a custom spec Duelund VSF type cap and the same Caddock resistor. The caps used in both networks were the same value (0.01uF as mentioned above), but the Duelund cap costs about 10 times more than the Hovland cap (I know this because I have Duelund make me the exact same parts today as I make new Merlin Master RC networks, exactly as Merlin made them, for customers who want them today). While this makes the Master RC’s much more expensive than the Standard RCs  (which I also can make for folks), the Master RC’s do sound better.

The Merlin Zobel, interestingly, basically comes into play around 1.0Mhz (at 20KHz its impedance is around 800 ohms) and it is basically providing a way for RFI frequencies that appear at the speaker terminals to be dissipated.

IMO, since I find later/last version of Merlins made to have less coloration or noise due to improvements they have in the crossover caps, and internal wiring used - I think the effect/benefit of the Master RCs is more audible.

Duke is correct that the speakers (TSM and VSM models) have a quite flat on axis frequency response, though due to the characteristics of the soft dome tweeters Bobby used the on axis response in the treble is a little rougher on axis. The speakers were recommended/designed to be used as noted in their user manuals At around 10 to 15 degrees off axis as there is where the frequency response was the most smooth/flat. Yes, the speakers have fairly wide dispersion and some attention is generally needed if they are placed near reflective sidewalls for best mid-top frequency performance.  IMO/experience, often any edginess can be corrected with some basic room treatment or proper speaker placement (as discussed in the speaker manual). I do notice in the later models/version (i.e. “Black Magic” edition versions) of the speakers, that the speaker’s upper mid/treble performance is very clean/even/smooth. Clearly better than in older models. I don’t know if the speakers have the exact issue Duke refers to (it is possible), I think I have some off axis frequency response curves somewhere which would give a idea if that is the case or not.

Happy listening,
Rich

@pmboyd  - Sorry, hard for me to comment on something I have not tried (trial/error listening of RC Networks with various different part types/designs) as my experience is limited to the Merlin Standard RC network, the Merlin Master RC's. BUT there are other folks making RC network (Zobel) devices. One example I can think of off the top of my head is the Walker Audio High Definition links - these are a Zobel network (which I have heard, but I can't accurately recall the sonic effects they had as it was more than 15 years ago that I encountered them). So, there are other things out there to compare (the Merlin RCs) them to (if you can't DIY your own)... I will say I think that their effect DOES vary from system to system, but generally when you are damping/squashing RF that is at the speaker terminals, you are removing a layer of fuzz/haze from the sound. My thinking (2 cents) is that the resistor type plays some role (as you want something that is non-inductive and acts as a good resistor at RF frequencies) to the sound of the Zobel. The capacitor IMO is the item that has the most impact on the "sound" of the RC network. Apparently a good sounding cap for audio (coupling/bypass) use makes a good cap for a Zobel based on what I hear between the Hovland cap based RC and the Duelund cap based RC (which has a bit more cleaner/natural/organic character in my experience). - Hope that helps some.

@cal3713 The resistor value is 10 ohms (its written right on the part if you look at a pair of Merlin RCs) :-) FWIW, I use old Merlin Std RCs Networks on various speakers from time to time. The magnitude of the effect they have varies (can be very subtle to more obvious), but these days with the amount of RF floating around every home from wireless devices and switching power supplies some amount of that is bound to make its way to one's speaker terminals and it can't hurt to try a Zobel/RC to see if it can help mitigate those effects to some so nice benefit. This does assume the speaker and/or amplifier design you are using does not already have them incorporated into their designs. In my experience, most amplifiers do not have Zobels on their outputs, a few do however which is why Bobby P left the RC networks external to the speakers (doubling up RC/Zobel networks in the amp and at the speakers may make things worse, not necessarily better).

Happy listening,Rich