Go out and buy a DMM with inductance and capacitance capability. You can get them for less than $100 new and will get a very handy piece of equipment to have around anyway. Be sure you disconnect at least one lead of whatever you propose to measure.
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The Q isn't going to vary that much if you stay at around the same DC resistance, which the DMM should be able to measure as well. It's certainly going to be more than close enough for any cheap speaker.
My other comment is that replacing the capacitors (use Solen/Chateauroux at the very least) is going to make an even bigger difference than the inductors.
I don't know where you planned on buying the parts from, but you can always send the coils into Madisound, they can measure them and then sell you the "most correct" Goertz coil for your specific application.
Personally, i would tend to agree with Karls. This is, i would worry about the capacitors and internal wiring first and then take a look at the coils. If the speakers really are THAT "cheap", it might not be worth the investment that you are talking about making. Four inductors, decent capacitors, wiring, etc... will set you back over $100. If you've got an unbraced box that resonates and leaks like mad, has nothing to minimize diffraction and makes use of drivers that are low grade, putting that much money into the crossovers isn't going to help that much. In a case like that, you'd be FAR better of starting from scratch and building your own speakers. Sean
A lot of people like to do what your planning on doing but it is not as simple as one is lead to believe. The crossover in a given speaker is designed to operate correctly with the given components in the crossover. When you change components, the crossover is being changed as for frequecy of the crossover point, impedence and the like. I have spoken with numerous speaker manufactures on this and they have ALL said without fail that you have changed the design and the speaker will not measure the same. The drivers and crossover are matched to operate together as they are. Without proper test equipment, you are tuning in the dark. Yes, the speaker could sound better to you but is it still accurate? You tune to an unknown parameter. It could sound worse. Of course, if you don't care about accurate, tune away!
My experience is that changing / upgrading speaker components almost always improves transparency and dynamics as compared to mass produced items. While Bigtee does bring up some very valid points, the key here is to use parts that are identical in specific electrical characteristics to those supplied by the manufacturer. Some variables are bound to change, but they typically change for the better. That is, IF you've done your homework and selected good quality parts to replace those that were factory installed.
Lowering series resistance, reducing thermal and dielectric losses, reducing saturation / increasing headroom, etc... are all good things. The key here is NOT to change the crossover points or rate of slope. Driver blending should have already been taken care of at the factory and you haven't changed that since the electrical characteristics of the "filter" have been preserved. As such, the critical areas of crossover performance should remain consistent. You haven't really changed the glass, you've only cleaned it so that more light can come through.
As to what wire to use, that is a matter of personal preference. Personally, i normally like solid core copper with the lowest amount of dielectric absorption possible. This means air, teflon, enamel or cloth insulation. It is not as flexible or easy to work with, but once you put the speaker back together, it probably won't be coming apart anyhow. While i do use stranded wire in some places within my various systems, i typically resort to this when the wires themselves will be moved or are in a traffic pattern. Solid wire IS a better conductor but it is also more brittle.
If in doubt, use whatever wire that you're already using to feed the speakers from the amp with. Just make sure that ALL of your connections are properly prepped and secure prior to soldering. A rugged mechanical connection is prefered over relying on the solder to hold things together by itself. Try not to think of solder as "glue", but rather as a sealant to what was already a good electrical connection. Sean
Thanks Sean, I have already written down all the values of the current capacitors used, and I plan on purchasing a higher quality (such as hovland musicap) capacitor to put in its place. The current caps are Hanlan, and I am unfamilar with these. There are four different values of these in each speaker, and my estimated costs to upgrade to the musicaps will be almost 150.00. The current wire is a light weight stranded wire that is clipped to the drivers (not solderd). If you could reccomend what guage of solid wire would be best I would consider checking to that.
Strictly ballpark suggestions here on wire:
18 - 20 gauge for the tweeter
12 - 16 gauge for the two mid-woofers
You can start off by using some simple solid core copper wire from your hardware store and see what gauge gives you good results for just a few bucks each. Most stores will allow you to buy this from a spool for pennies per foot. Once you find the right combo, you can then experiment with different brands / types of cable that come in those specific gauges. Who knows, you might be happy with the "generic" wire and leave it at that.
As to the caps, i would look at using Auricaps if possible. Don't know if they come in the values that you need, but it's worth checking into.
If you have large resistors in the circuit, try replacing them with some non-inductive Mills . As mentioned, keep the leads on the components ( resistors & caps ) as short as possible and make secure connections prior to soldering.
While you're doing all of this, you should take steps to "damp" both the crossover AND the actual baskets of the drivers themselves from external vibration. You might be amazed at how much sound a ringing speaker basket contributes to the overall output of a speaker. Many different approaches to this, so have at it. If you want suggestions, email me directly. Sean
Sean, good advice there!
I agree that I have just about never come across a crossover upgrade that didn't yield very nice dividends. Bigtee, you must be speaking to paranoid loudspeaker manufacturers. Anyone telling you that you are changing the design of the loudspeaker is fearful that you will find happiness in the upgrade, and therefore will delay the purchase of your next pair of speakers.
Based on a recent thread, the Mills resistors were suggested to me over the Ohmite or North Creek I have always went with. I did give them a try this past fall, and I could not feel more strongly. The Mills resistors, while certainly superior to the norm which one comes across, were much flatter and more lifeless.
The Ohmite resistors are the best I have worked with. I consider them the single biggest, cost effective improvement one can make to a loudspeaker. Almost always a less than $10 upgrade. They get rid of so much harshness, grain, and glare from the high frequencies, without dulling detail or the music itself, that it almost(yes, almost) feels like a better tweeter was installed.
Also, while I normally go too far in parts upgrades(guess it's the hobby), I think we should scale back capacitor/coil recommendations for this project. Reason being chez stated this was an inexpensive pair of speakers. I think that Axon or SCR caps will provide a great improvement, at very low cost. Instead of the $150 he quoted for the Musicaps, he would be looking at less than $25. And, I would go with 14 gauge coils as opposed to 8, from either North Creek or Alpha Core Goertz.
I think that for an inexpensive pair of loudspeakers, one will find the limiting factors to be the cabinet and drivers. In my opinion, even if these two areas are improved down the road, the limits of the Ohmite resistor/SCR cap/North Creek 14 gauge coil will still not be exceeded. While I am a huge fan of MIT and REL film and foil caps and coils as big as a dinner plate, in order to see their improvements, the rest of the speaker must be on quite a high level themselves. This should keep the price of the upgrade at probably $60 - $75, while taking the speaker's crossovers farther than one would expect, including a sizable cushion for down the road tweaks.
Chez, when I used to buy Ohmite resistors, Mouser was normally my source. I understand that North Creek sells their own version now, although the price will be a bit higher. On the plus side, North Creek could be your source for caps and coils as well, so you would get a break on shipping by buying from a single merchant.
I think they have a very reasonably priced capacitor you could look at in lieu of Axon/SCR. Basically, everything they sell is at least very good, so I wouldn't hesitate to buy from them. I would highly recommend you go with their 14 gauge coils for your little project here.
As far as the values of your resistor, your logic seems good, but you should measure them anyway.