Great video Gary! The two most popular speaker impedance meters that I've used over the last few decades (I'm from the AV industry), are the TOA ZM-104 and the GOLDLINE ZM1P.
It is a little perplexing Evan, it is simply the way DC and AC react through a transformer coil. A standard multimeter only applies a single direction current through the coil. It does not get affected by any collapsing magnetic fields that are produced with alternating current.
Does this Allosun meter provide the AC current as you mentioned? I understand to by a really good meter is hundreds of dollars. I need to stay under $100. Great demonstration!
There are an abundance of books on electronics. It depends on what you want to specialize in. Many electronic project shops have beginners books and even your local library is a great start.
Hello i have stupid question - Can I measure impedance of unknown output transformer in tube amp. It will be connected on speaker, but disconnected from anode of output tube ?
hi, I have an older bogen dma 80 mixer amp with 70 volt output which is 80 watts it does not tell me the recommended impedance for 70 volt can someone help me please
Yes, some amplifiers don't have listed the impedance. Using the 70v speaker terminals on this unit and with 80watt capacity the impedance limit would be around 60 ohms. So keep your impedance above that. I have included a link to a simple chart under installation basics: sound.whsites.net/articles/line-amps.html#ref
My local made pa amplifier output volts are 95v @ 8ohms. (450 watt @ 8 ohms) it has no output transformer. The dc supply rail is 95+95. Can i drive 100v line speakers on it? how many speakers i can drive on it?
I am not sure what amplifier you have. The short answer is no. The output of this amplifier is 8 ohms. A constant voltage amp that drives 70/100v speakers has a much higher output impedance.
@@GaryDmedia I have toa column speakers. Each have 330 ohm imp 30 watt . If i connect 40 speakers in parallel it imp will 8 ohm & 1200 watt. My amp out on 8 ohm is 100. volts. What is your opinion?
@@GaryDmedia my self made amp 24 transistors 2sc5200. Dc rail is ± 95vdc. No out put transformer direct out 8 ohm 100v. there is not allow photo comment therefore i cannot send you photo. Kindly can you give me watsaap or e mail.
Thanks, Gary. One question: some "professional" replaced speakers in our church last year; since then the amp sometimes cuts out. I measured the 100V line impedance at 38 ohms - should, of course, be over 80 ohms for our 120W amp - he must have used tappings far too high for the 13 speakers. Rather than risk a fall from a very high ladder while changing tappings, I should be able to switch the line to the 70V setting and crank the mixer and master vol controls up a bit, shouldn't I? Most settings are well under 50% at the moment.
+Michael Duffy Yes that is a very simple fix. With a lower output voltage the speaker system won't draw as much current from the amplifier. I hope that the impedance lifts enough for you. Hopefully the amplifier is only cutting out because of the overload protection. Many of the installations I work on have the speakers set a 2.5 - 5 watts and this is ample for most seminar type applications where ceiling speakers are employed. Thanks for asking such a good question.
Thanks again BUT I expected impedance to stay the same while with the lower voltage, current and consequently wattage, reduced. Is this wrong? Michael D
+Michael Duffy My mistake, yes you are right. the impedance or resistance of the speaker system will not change. The load on the amplifier will be reduced. Not good if you have to change all of the transformer taps on the speakers. May be better to replace the amp with a more powerful one. Hope the simple fix corrects the problem.
