heisthl wrote:dave g wrote:
Actually, you have it exactly backwards, heisthl...draw the equivalent Thevenin circuits and you will see. A load impedance smaller than a source impedance results in more energy being dissipated in the source, while a load impedance larger than the source impedance simply results in less current draw and less total energy dissipated.
And no, you can't "store" energy as heat because it cannot be reclaimed or injected back into the circuit...heat is nothing but the energy dissipated by the real component of the impedance of a device. Like I said above, running a lower impedance load will result in more energy dissipated in the source, e.g. by the resistance of the transformer windings which can result in overheating and damage.
Please tell me more - I was going under the assumption that transformers were designed so the secondary absorbed whatever energy the primary wanted to impart and that energy needed a path to ground equal to or less than the taps impedance and if it doesn't get it there is heat buildup in the transformer generated because the primary can't transfer it. Are you saying that a transformer will run cooler than normal if the speaker is of a higher impedance than the tap? Any chance you overlooked the heat build up of the primary in your calculations? What happens if you connect a really high impedance load like no speaker connected at all?
Hi Guys,
because of my lack of technological knowledge I cannot chime in in your discussion, but perhaps it could be of interest for you, what an Electrovoice technican once has told me concerning this:
I asked him concerning an ODS-Combo with 4Ohms OT and 8 Ohms EVM 12-L, if - from a technical point of view - he would recommend to use a 8Ohms extension speaker in order to "heal" the "impedance mismatch".
He said surprisingly (for me): "No, no need to do so, better use it wih only one 8 Ohms speaker!!" and explained:
- There is not something like a fixed speaker impedance, it changes with ferquency. An EVM12L in working condition is more often near 6Ohms than near 8 Ohms.
- If you use an extension cab it has to be positioned with some care in order to avoid phase cancellation.
- I you use (he said) just one 8 Ohms speaker in the 4Ohms OT output you will:
a) loose some percent of maximum wattage but that this I would not perceive as a disturbing loss of loudness.
b) but gain less distortion in the power amp, because the power amp is under less stress, if you use only one 8OHms speaker with the 4 Ohms OT.
In the end he recommended not to use an extension cab if I can live with the small drop in loudness
I compared both combinations and - indeed- for my taste the "mismatched" Combo with only one EVM 12L was the one I liked better: More "musical" in my ears.
Cheers
Max
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