Given a perfect speaker with perfect crossover which gives a perfectly flat response when driven by one pair of wires it is fairly easy to show to anyone who understands electronics that true biwiring with real cable (i.e. with a little resistance) will cause a dip in response at the crossover frequency. Some real speakers with imperfect crossovers might benefit from an added crossover dip; others will not. The usual arguments for biwiring are pure bunkum; the real isue is whether a little dip will help or not.
Feeding via two wires from two different voltage sources is not really biwiring. It could only improve a poor speaker design which was unbalanced when fed from a single source. Is your speaker really that bad?
Feeding via two wires from two different voltage sources is not really biwiring. It could only improve a poor speaker design which was unbalanced when fed from a single source. Is your speaker really that bad?
The 'back EMF' argument only makes any sense at all when you have a very low amp output impedance (high DF) and high resistance speaker leads i.e. SS amp with thin cables. Only in those circumstances would biwiring reduce coupling between drivers. If you have higher output impedance then that will provide coupling, whatever cables you use. If you have low output impedance and low cable resistance then you have low coupling with single wiring, so biwiring changes nothing. So the issue only matters in circumstances which are rare.
Of course, high resistance cables is also the scenario which maximise the crossover dip caused by biwiring.
The speaker designer should have already taken rising impedance into account. If you want a treble boost then do what you suggest, but you are really implementing a fixed tone control rather than biwiring.
Of course, high resistance cables is also the scenario which maximise the crossover dip caused by biwiring.
The speaker designer should have already taken rising impedance into account. If you want a treble boost then do what you suggest, but you are really implementing a fixed tone control rather than biwiring.
That can be a useful trick. Let's say that you want to drive the woofer (and its crossover) with a larger voltage signal than the tweeter (and its crossover). You can hook the tweeter to a lower impedance tap than the woofer. In the last set of speakers I designed (an MTM array), I put the woofers in series, then drove their crossover from the 16 ohm tap. The tweeter and its crossover were driven from the 4 ohm tap to achieve a -6dB attenuation without using resistors in the crossover as attenuators. Worked like a charm.
This assumes that the differences in voltage levels are something you want for a particular design!
To start with, if you connect a speaker to a single tap, the loading becomes non-ideal anyway- most speakers have impedances which vary all over the place with frequency.
In the example I gave, I connected the woofers in series to get something closer to 16 ohms, then used a 4 ohm tweeter. So, non-ideal, but no more non-ideal than a conventional speaker connected conventionally.
In the example I gave, I connected the woofers in series to get something closer to 16 ohms, then used a 4 ohm tweeter. So, non-ideal, but no more non-ideal than a conventional speaker connected conventionally.
Ok that makes sense, as long as the proper load is on each tap i can connect multiple speakers on a single transformer reasonably safely. IE...4ohm on the 4ohm tap plus 8ohm on the 8ohm tap and a 16 ohm load on the 16 ohm tap and the output tube will still see the same impedance. This of course assumes each driver has linear resistance over the frequency range which doesn't happen. the drivers resistance changes with the frequency and the rated specs are just an average. Thank you for clearing that up for me.
It is true in case of only one load to only one amplifier, but if there are two or more loads to different taps in the same transformer, must take into account the interact between them in the secondary of the transformer, and reflected to the primary.
If cable resistance is very low, then yes biwiring makes almost no difference. What if cable resistance is low but not negligible - the usual case? Near the crossover frequency it is very likely that one half of the crossover presents an inductive impedance while the other half present a capacitive impedance. If the two halves of the crossover are connected at the speaker end then there is some reactive current sloshing back and forth between the two halves of the crossover, as well as the net current travelling to/from the amp. Separate the two halves there and join at the amp end instead - this is biwiring. The reactive current now has to travel along the cable, and will cause extra voltage drop. The result is a small dip in response at the crossover frequency. So in circumstances where biwiring could make a difference, the main difference is a crossover dip.sreten said:
Hi,
Your forgetting about the x/o. You have one loading regime in the
bass and another in the treble, they don't add together as loading.
rgds, sreten.
http://community.klipsch.com/forums/storage/58/1401434/McIntosh Autoformer Training Page.pdf
there's a couple reasons why you would want to do that. depending on the taps you have, say 4/8/16, you can compensate for room brightness, room darkness, etc, by seperating the HF and LF section onto different taps. If your room sounds too bright you can put the HF section on a low impedeance tap and the LF section on a higher impedeance tap. see the PDF. done it many times and it works well.
there's a couple reasons why you would want to do that. depending on the taps you have, say 4/8/16, you can compensate for room brightness, room darkness, etc, by seperating the HF and LF section onto different taps. If your room sounds too bright you can put the HF section on a low impedeance tap and the LF section on a higher impedeance tap. see the PDF. done it many times and it works well.
Thomas Meyer talks about it here:
Speaker impedance and amplifier output taps
I tried it briefly but it changed the tonal balance of my system too much for my liking, but it was interesting.
Speaker impedance and amplifier output taps
I tried it briefly but it changed the tonal balance of my system too much for my liking, but it was interesting.
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