I envy your weather, but I don't let winter stop me! 🙂 My second set of DIY speakers were cut and sanded on my back deck, on a subzero weekend in a snow squall. The wind was so intense I had no mess to clean up. 😀
I am very interested to hear how this goes, however in another thread the guys were saying that second-order would be better. One of our forum members has even designed a crossover for this purpose. I'll try to find the thread (still earlier here).
Chris, I have my finger on the trigger to buy a pair of CHR-70.3 (copper) from Bob.
I am curious about a quote that I found on teh interwebs:
Based on this, it seems like if I just pull out the front EL70 from my microTowers and replace them with CHR-70, the EL70 (top) will then be getting twice as much power as the CHRs.
Is this interpretation correct? I know you said that you'd be inclided to just go ahead and try it, but if the above is true I figure I might as well plan on getting a couple of 4 ohm resistors to augment the impedance of the EL70s to ~8ohms and then rewire for parallel.
I am curious about a quote that I found on teh interwebs:
Based on this, it seems like if I just pull out the front EL70 from my microTowers and replace them with CHR-70, the EL70 (top) will then be getting twice as much power as the CHRs.
Is this interpretation correct? I know you said that you'd be inclided to just go ahead and try it, but if the above is true I figure I might as well plan on getting a couple of 4 ohm resistors to augment the impedance of the EL70s to ~8ohms and then rewire for parallel.
1/R1 + 1/R2 .... 1/Rn = 1/Rsystem
I hate the idea of adding a resistor to a woofer. Yuck. If experimenting though, sure. Give it a try.
Think about this. If you're an electron, and you approach a T in the road. Left is up and over a huge mountain and right is up and over a mole hill. Which way are you going to go? The easy way right.
Oh and the discussion about going second order on the tweeter needs some clarification. That was when considering a "low" crossover point.
I hate the idea of adding a resistor to a woofer. Yuck. If experimenting though, sure. Give it a try.
Think about this. If you're an electron, and you approach a T in the road. Left is up and over a huge mountain and right is up and over a mole hill. Which way are you going to go? The easy way right.
Oh and the discussion about going second order on the tweeter needs some clarification. That was when considering a "low" crossover point.
😕
Well, the EL70 isn't a woofer, per se, but I have to ask; why yuck?
I like experimenting, but only if there is a realistic expectation of success.
Makes sense, of course, but how is this reflected in the formula you wrote above? (and where is the "T" in the road in series wiring? 😉 )
Ah, I see, so if you were to cross higher (maybe around 6-8k) a 1st order works because you are far from the Fs? I do recal that from the discussion now...
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if you already have the drivers on hand, you could swap out the drivers and listen to the results* in less time than it takes to find a consensus among DIYers
then you'd be as expert on this particular question as any of us who haven't tried it
* hypothesis + test + observation = ?
then you'd be as expert on this particular question as any of us who haven't tried it
* hypothesis + test + observation = ?
Ok, I see my post was a little strange.
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That is the formula you use to calculate total resistance. Perhaps you already knew about it, but just wrote it in case you don't know it.
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No, it's not a woofer I suppose. To be more correct in what I'm saying then, I hate the idea of adding a resistor to any driver in the system, unless required to attenuate a driver. Particularly drivers that play below the baffle step cut off. 😎
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It won't be a failure. I just hate the thought of precious amplifier power being turned into heat. Worth trying.
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In series wiring, I suppose a new analogy is needed 😀 In series they see the same power I think?? That I'm wavering on. I think your quote was referring to parallel wiring when it said one driver gets more power. But you plan to wire in parallel anyways don't you? That's what I thought, hence the analogy. If going series, no need for any resistors.
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Even higher depending on the tweeter. I think the concensus was around 10khz or even more, with the fullranger run wide open.
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That is the formula you use to calculate total resistance. Perhaps you already knew about it, but just wrote it in case you don't know it.
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No, it's not a woofer I suppose. To be more correct in what I'm saying then, I hate the idea of adding a resistor to any driver in the system, unless required to attenuate a driver. Particularly drivers that play below the baffle step cut off. 😎
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It won't be a failure. I just hate the thought of precious amplifier power being turned into heat. Worth trying.
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In series wiring, I suppose a new analogy is needed 😀 In series they see the same power I think?? That I'm wavering on. I think your quote was referring to parallel wiring when it said one driver gets more power. But you plan to wire in parallel anyways don't you? That's what I thought, hence the analogy. If going series, no need for any resistors.
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Even higher depending on the tweeter. I think the concensus was around 10khz or even more, with the fullranger run wide open.
Except that he doesn't own the drivers yet, and is looking for advice on the proposed plan to make an informed decision about the purchase. At least that's what I'm getting from it.
Indeed. I hear you. I just wondered if you had an knowledge of the theory behind all this.
Yes, but like I said earlier, the worst case scenario is that I hate the results and I have a shiny new pair of CHR-70.3 for my next project. I really have very little to lose...
This is the thing; I am under the impression that I will need to attenuate the EL70 because it has half the impedance of the CHR-70.
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My amp is 50w/chan and I typically use 1 watt or less, so I can afford to sacrifice a bit of efficiency.
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I should clarify: The microTowers currently have 2x EL70 (4ohm each) wired in series for an 8ohm load. If I remove the front EL70 and repace it (maintaining series wiring) with the 8ohm CHR-70, then I have a series load of 12ohms (shouldn't be an issue) but most importantly will the 4ohm EL70 be playing twice as loud as the 8ohm CHR-70 in this configuration?
If I wire 8ohms and 4ohms in parallel, I have a load of 2.6ohms, which my amp cannot handle.
My only other option is to increase the impedance of the 4ohm EL70 to 8ohms by adding a resistor and then wiring it parellel to the 8ohm CHR-70 for a total load of 4ohms (which my amp can handle). I suspect that the power I am throwing away with the resistor in this scenario would result in the opposite problem; the CHR would now be playing louder than the EL70.
The bold question above is the clincher. If the series wiring load of 12ohms means the power would be distributed evenly to both drivers, then I can ignore the resistor(s) and parallel wiring.
Perhaps chris' approach really is the best. I am just very curious about the theory behind power output of series wiring of drivers with different impedance...
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I really don't think the EL70 will play twice as loud in series. Someone can correct me if I'm wrong, but a volt is a volt.
Your amp probably can handle 2.6ohms if you only use 1watt and it's a 50watt amp. The minimum impedance is likely more like 2 ohms though. Still probably ok. Just don't crank it 😱
Adding a resistor does more than just burn up power. Sorry if I simplified it that much.
Just try it then. If you have little lose, just give 'er. I really don't think it'll work out, but give it a whirl.
Your amp probably can handle 2.6ohms if you only use 1watt and it's a 50watt amp. The minimum impedance is likely more like 2 ohms though. Still probably ok. Just don't crank it 😱
Adding a resistor does more than just burn up power. Sorry if I simplified it that much.
Just try it then. If you have little lose, just give 'er. I really don't think it'll work out, but give it a whirl.
What I meant was "twice as loud as the CHR-70." I guess I have still not been clear enough. Right now, the 2x EL70 (in series) have identical output "volume" at any given input voltage (in other words, the front driver is just as "loud" as the top driver. I assume (perhaps incorrectly) that this is because they have the same impedance and efficiency. If I simply replace one of the 4ohm EL70 with an 8ohm CHR-70 (maintaining the series wiring) it seems logical that at any given input voltage the EL70 will be playing twice as loud as the CHR-70 (because the CHR-70 has 2x the impedance of the EL70).
Perhaps I will try this, however I am still concerned that the EL70 will be twice as loud as the CHR-70 in this scenario (if I was an electron and came to a T in the road...).
I figured that's what you meant by "yuck". I do not want to introduce something that reduces sound quality.
I think I'll just go ahead and see what happens with stright-up series wiring...
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No I did understood that time. I really don't think the EL70 will play twice as loud as the CHR-70. 😎
Send Planet10 an email. He's surprisingly quite on this thread. Changing the T/S parameters and wiring drivers differently totally changes enclosure design. That's more my fear of adding the series resistor than anything. Maybe Dave has something to say about it. I can't help but think it'll totally change the cab alignment.
well there's also the question of difference in sensitivity between the two drivers ( actually very small in this case = nominal .6bB at 1 watt) - when you combine that with the algebra soup of calculating actual "power" delivered to/consumed by individual drivers of different impedances in series you can see why some of our eyes (i.e. mine) just glaze over and say - "try it"
If you have plenty of power to spare, I'd probably suggest balancing the load with a resistor, but perhaps with the 4R in parallel with the CHR and the two drivers in series. Whichever topology used for power balancing you'll be wasting some as heat (use at least a 10W rated part), but then you should have only the above noted nominal net difference in sensitivities at "1 watt" of .6dB
well yes, a volt is a volt, but there's those pesky other variables in Ohm's Law calculations P=V^2/R , inductive reactance component of "impedance" varying with frequency all that stuff - clearly I'm no math genius, hence the simplistic "try it and see, it's not my money"
sorry about the disjointed reply - distractions at work - multitasking gets exponentially harder as you..
what were we talking about?
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T/S parameters are very similar between the two types of drivers, and technically I would only be changing the T/S parameters on 1 of 2 drivers in the box, so I cannot imagine that tuning will change all that dramatically. Also, the bottom panel of my microTowers is easily removed for port tuning. To be sure, I have already played with this quite a bit and arrived at a custom tuning that I find best for me. If I need to do adjustments after this mod, it is a no-brainer.
Ideally, I will not be changing the wiring, either. Fingers crossed that series wiring works out and I don't need any added resistance on the EL70.
Yes, I considered sensitivity, but dismissed it since it is negligable.
Perhaps the straight-up series wiring solution will result in the EL70 being "louder" but not "twice" as loud. The fact that the EL70 will be on top (non-directional) and the CHR-70 will be on the front might mitigate/balance this output difference enough that it might just sound fine. Different, but fine. If this is the case, I guess I can expect crisper highs from the front CHR-70s and even more vertical and horizontal dispersion and "ambiance" from the harder-working EL70s up top.
Time will tell. 🙂
here's the danged spreadsheet I was looking for to calculate the power dissipation at various nodes in series / parallel and balanced load configurations
http://www.duncanamps.com/zips/speaker5.xls
model as 3 s+p (a) with a ballast resistor of 7.2R in parallel with the CHR70
otherwise I think you're quite right in that without balancing the EL70 will play louder whether in series or parallel- to what sonic effect is of course yet another question
edit: Dave will be able to pop in for a visit later this afternoon with his thoughts on the effect of any of these approaches on "tuning"
http://www.duncanamps.com/zips/speaker5.xls
model as 3 s+p (a) with a ballast resistor of 7.2R in parallel with the CHR70
otherwise I think you're quite right in that without balancing the EL70 will play louder whether in series or parallel- to what sonic effect is of course yet another question
edit: Dave will be able to pop in for a visit later this afternoon with his thoughts on the effect of any of these approaches on "tuning"
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Awesome! Thank you!
I am not sure how you used the 3 s+p (A) page to come up with 7.2R in parallel with the CHR-70.
I did, however, model it this way:
Speaker A (CHR-70) = 8 ohms
Speaker B (resistor) = 19 ohms
Speaker C (EL70) = 4 ohms
The result is that speakers A and C end up with (roughly) equal watts and the total impedance is 9.62 ohms. If I go with 20 ohms for "speaker" B, then the CHR-70 ends up getting slightly more power (to compensate for minor lack in sensitivity).
Am I doing this wrong?
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