Thank you all for this. I do appreciate it. I'm new to this. I did have the connections to the actual speaker elements soldered and that made a nice improvement in the sound. Removed a kind of rizz or roughness I had not noticed until it was gone. These speakers have a wonderful top to bottom consistency or coherence I haven't heard before in a cone speaker. I have heard other speakers do certain things better but not overall. The bass quality is very accurate as well. Again, thanks for your input and if you have more data on this it would be welcome. This speaker is worth every minor improvement added to it. Jonathan
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Keep in mind that Dunlavy chose resistor values on a per-speaker basis, choosing slightly different values until the speaker measured just right. Therefore, you may not find a schematic with specific values and one person's set most likely has slightly different values than another set. Many of the sand resistors on the xover are glued one on top of another in parallel, so one would need to remove them to be able to read the values (they do not have color band indicators on them as Ge5556 suggests). Also, since many of them are connected in parallel, in-circuit measurements are not recommended. The best way to find the values would be to remove them and read the markings on the top of the package or measure them individually. I too faced this same dilemma with my pair of SC4a's and after much research and thought, decided not to monkey around with changing them out. If you do want to take the plunge, use 10W non-inductive resistors such as wire wound Mundorf's. Two tweeks that I made to the crossovers that made a nice improvement in sound quality was to replace the binding posts with Cardas CCGR-L type and coat the components with AVM (Anti Vibration Magic) available from AuDIYo. Finally, as an aside from your topic, placing the speakers on Star Sound Sistrum SP-101 stands makes a big difference in sound quality. That is what I did and love the stands (looks cool too). email me offline if you want to chat. |
Shadorne, why can't you just measure them in place at the shoulders without removing them? I didn't think it would throw it off that much. You can probably do that on the woofer. However, generally the resistor(s) on the tweeter may be in parallel with the voice coil or something else that conducts at DC. You can remove one end and measure it that way.... Your point about reading off the values is correct but most manufacturers will select parts to improve the precision of the crossover....certainly Dunlavy would have done probably done this and you want to stick as close as possible to the orgininal. FWIW - I'd not bother with the resistors or inductors (air core most likely) on DL's - if anything it is only the caps that might deteriorate after 10 to 20 years....unless there is a well known problem with one of his designs? |
Here is some recent research as why you might worry about capacitors rather than resistors (especially large caps and ones that carry higher voltages - so this affects passive speaker crossovers as well as tube coupling caps most) See this ClarityCap Research. Note that the measured resonance (from capacitor changing shape under load) is extremely small but it does cause IMD distortion, which tends to be much more audible than other forms. |
Again I want to thank all of your for your very helpful and intelligent comments and observations. I hope my questions and quest here will help you all in turn. My concern now is I note two of you did not elect to replace the resistors and I guarantee you that those who declined to do this are more capable of such a task than I will ever be. Without direct knowledge, and I stress that, I do not believe John Dunlavy had the time to hand pick his resistors or tweak them for each speaker other than to buy them in lots and stick them in the speaker. I am convinced that fine quality resistors (and capacitors) would make a major upgrade. I cannot back up this statement except it has been my experience in the past with other components (which my engineer soldered in for me). I know I recently made two minor adjustments with cardboard on top of the speakers and brass screws on the tweeters and I heard a noticeable improvement worth the $5.00 for the thick cardboard and the $2.50 for the eight screws. I also had the speaker elements soldered bypassing the cheap clip ons that are used to connect to each speaker element. That made a very nice improvement. I will next take off the Dunlavy basses and put cheap points under them and then in a week or so add the Star System points. Then once I have that settled and confirmed as better I'll somehow confront those xovers. From all of this I will also do a summary of what actions I took that improve a Dunlavy SC IVa and for how much money. I will include resistor values and whatever detail I can to help others. That way we all will have a complete record of this. I believe this speaker is worth the effort and whatever pain. I hope you all will keep giving me input and suggestions as you think of possible upgrades. I really want to hear more from you all. Like tonight. Jonathan |
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