Testing 70/ 100 volt Speakers | Audio Impedance Meter
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- เผยแพร่เมื่อ 6 ก.พ. 2025
- This video shows why an audio impedance meter is needed to test the total load of a 70/ 100 volt speaker system. Basic impedance meter: amzn.to/2XGAoMW
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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.
Thanks Jason, I haven't used those ones but I am glad you shared the info. They can be hard to come by. I appreciate it.
*It's totally great and briliant explanation Gary, thanks for bringing up this video.*
Thanks for letting me know. I appreciate the feedback.
Thank you! Although I am still curious to know why the DC meter read a different impedance.
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.
@@GaryDmedia Inductive reactance is what I’ve been used to hearing it as opposed to electric resistance.
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 ?
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!
Yes the Allosun EM 480B is the correct meter to test 70/100v speaker lines. This is the Amazon link: amzn.to/3ts4BwB
Hi mr gary can you make a circuit for recording from PA 100v to an iphone
How much does RMM51 cost, Mr Gary ?
Great meter,shame you can't get them anymore!
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.
Thanks Gary. Very clear and concise.
Peter Buchta I'm happy to hear that. Trying to keep it as simple as possible without distorting the principle is difficult. Thanks for your comment.
Thanks Gary, Where to buy the " AUDIO IMPEDANCE METER " in Indonesia
I am not sure of where in India you could buy this meter but this one may be available from a supplier near you: amzn.to/3iEUjnR
Is there a book or various books to introduce me into audio electronics? Thanks a lot, I´ll check your channel man :)
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.
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?
Would you please be able to let me know what brand and model amplifier you have? That would help me make a comment.
@@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.
My email is contact@garydmedia.com
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
thanks
No worries, it's a difficult subject to get your mind around. I thought it would be best to just show it in practice.