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Master_Scythe

Old 3 way speakers

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So while opshop hopping I found some floorstand speakers to use untill I can afford some modern day ones.

 

From google, all I can find is they started production in 1976, and went untill an unknown date (these look PRETTY new, so I'd guess mid 80's?)

 

Anywho, They're PYE Audio, a mainly NZ company, with Magnavox internals (and they all have 'made in australia' stickers on the speakers, so its well before magnavox was a chinese knockoff sold in target, lol)

 

Now, looking at the speakers, they dont need much wattage (aka, dont crank my amp, Im well aware), but they also seem to be very low Impedance (hence not connecting them up yet).

 

 

3 Individual speakers, (roughly: 1 X 6-8", 1 X 4", 1X 1"), each with an 8 OHM sticker on them, connected in paralel I believe

 

[amp] =speaker1=speaker2=speaker3 (the smaller speakers having filtering caps on them).

 

This would make them... 2 Ohm? I need them to be 6ohm or higher. Can I mix and match paralel and series to make that?

 

 

 

Here is where it gets odd, I was reading some audio forums, and they said, although innacurate, a DC multimeter can be used to ROUGHLY measure the Impedance of a speaker system (round the number up).

Setting my multimeter to 200 Ohm (the lowest it goes ><) I read 8.5Ohm across the speaker wire. This, to me, doesnt add up.

 

Can anyone shed some light on my issue and lend some help?

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I need them to be 6ohm or higher. Can I mix and match paralel and series to make that?

I don't believe that's a wise idea. I don't believe it's advisable to run speakers in series.

 

I would question the need to keep the speakers >6ohm though...

 

At the end of the day an amp can deliver a certain amount of power, connecting three speakers in parallel will just means it draws (roughly) three times as much current.

 

But then again, I don't fully understand the whole "impedance matching" thingo, so maybe that's where the >6ohm comes in.

 

Rob.

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Yes, I understand that side of it. and yes, thats where matching comes in.

 

lower resistance means more CURRENT, and if the amp cant supply it, it'll burn out. Hence impedance matching.

 

and from my googling I cant seem to find an issue with running in series, its a very common thing in multi-speaker devices to keep impedance within acceptable ranges.

 

 

From what I can figure:

 

I should have 2 in Paralel, and one in series, but im not quite sure how to wire that. Im looking into it. Also I dont know if the filtering caps on the smaller speakers make a difference to anything except sound when it comes to working this out.

 

Im still googling.

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Most speakers from back then were rated 8 or 4 ohms, with 8 being the most common.

 

Remember, impedance is usually measured at a nominal frequency as it varies with frequency.

 

Robzy, impedance matching is important for 'maximum power transfer' and 'damping'.

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yes, so each speaker has a sticker that says 8ohm and a wattage rating.

 

because these 3 are in parallel i believe I should have 2Ohm

 

However my innacurate DC multimeter shows 8.5 (and the audio forums all say to round UP) which is what I dont understand.

 

Could the filter caps be messing with the muiltimeter? Which of the two should i make into series? the two small speakers or the woofer and a speaker?

 

something isnt quite right here....

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lower resistance means more CURRENT, and if the amp cant supply it, it'll burn out. Hence impedance matching.

Not quite, impedance matching is for the reasons logicpr0be gave (even though I don't understand them).

 

logicpr0be: Can he just plug the paralleled-8-ohm-speakers straight into the amp?

 

Rob.

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no, no i cant ><

 

I may not be as informed as you guys on the math side, but I know from experience, low Ohm on speakers, and an amp that cant handle it = pop! Sure id have to 'crank them' slightly, but im not risking it.

 

http://www.bcae1.com/spkrmlti.htm

 

If my math is right, and I do have 3X 8Ohm speakers in paralel, I should have 2.6 (2 or 4) Ohm speakers.

 

If one is in series, and one is in paralel, it should work out to: 8+8=16, 16/2=8, unless I havent understood the math (which is likely, my math is terrible).

 

Where is Datafast when you need him? lol

 

The only bit that doesnt add up to me, is why EACH SPEAKER has its own model number, its own watt rating, and its own OHM rating printed on each speaker.

 

As i said, this should equal a very low Ohm, however, (as i said, although HIGHLY innacurate) why does my DC multimeter show 8.5?

 

EDIT: ah, it seems a DC multimeter will simply be measuring ONE speaker, or so someone on an audio forum suggests.... that would explain it... or is he wrong? I still think putting one of these speakers in series will fix my issue. Either that or the filtering caps are throwing off the multimeter readings?

Edited by Master_Scythe

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Impedance is different to resistance.

The crossovers cause all sorts of shit to happen.

 

Take them as 8 ohm and add up the wattages as I said.

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I thought a crossover was a dedicated piece of hardware, these are just filtering caps removing bass from the smaller speakers.

 

Or is that what a crossover is?

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Yes, but being reactive components, they combine with the resistive components to give the impedance which then varies with frequency.

 

The rating is usually done at 1 khz, by memory, hence, the DC multimeter is usually fairly close to the nominal impedance on the input terminal.

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The what? Sorry my brain isnt doing the thing its meant to do tonight, ive been sleeping terribly.

 

 

So the caps are reactive components.

 

the resistant components are... the speakers themselves?

 

and a multimeter should be (from other forums, 1.3X) close to the actual impedance of the speakers.

 

Did I understand correct?

 

 

 

The only problem Im having is understanding how basic capacitors are upping what should be a 2.6ohm load to 8.5ohm (well, more assuming the 1.3X rule).

 

3X 8ohm speakers in paralel should be 2.6ohm. This is how they are connected. 2 filtering caps are taking that all the way to 8.5 or more? this is honestly possible?

 

EDIT: sorry for the doubting, but I just spent a great deal of money on my amp and wanna be sure.

Edited by Master_Scythe

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The speakers are reactive as well because they are coils but the copper has a resistance.

 

Being old speakers, they won't be under 4 ohms.

 

Even 4 was pretty rare back then as most of them were 8 or 16 ohms.

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Yes but EACH driver in the 3 way speaker is 8Ohm, labeled individually with their own part number.

 

and 3 in parallel = 2.6Ohm. Which is why im concerned.

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I realize that, but the reactive components work with ac.

Applying DC to speakers is usually fatal.

 

I'd be 99% certain that they are an 8 ohm rated box.

 

All these under 4 ohm things came out after they perfected power mosfets that could drive such loads.

 

That speaker is way too old to be anything under 4.

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agreed that with the age of them 8ohm makes perfect sense, but the math relying on the labels shits all over that. And they are original labels too.

 

Where would i need to go to get them professionally tested? They dont have a model number. It seems.

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If there are no shorts showing...........obviously there's not cause you put the meter on them.........plug them in and fire them up!

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Unplugging each speaker, the multimeter shows exactly 8ohm on each one (so the labels are correct).

 

 

the resistance across those 2 capacitors (being used for bass filtering) is showing about 22Ohm and 16Ohm respectively.... that could be accounting for the extra resistance.

 

I trust you Logicprobe, but im on a pension atm and im paranoid; my $350 amp relies on these being correct, so if anyone else could shed some light I'd GREATLY appreciate it.

 

 

 

In other news, i spent the morning running Liquid nails over all the joins in the speaker box, so it should now be air tight and very strong. Its drying on the veranda as we speak. One of the things that originally made me risk buying these was (besides the stupid cheap price) was the fact that the ONLY 3 way speaker I could find that PYE ever made, was being spoken VERY highly of, and a comment similar to "so much bass and the box isnt even ported".

Sure enough, its not. I hate ported speakers I find them very sloppy sounding. Cant wait to try these; someone else with a lot of audio knowledge tell me:

 

I read 8.5OHM on the speaker cable, with a DC multimeter, which im 90% certain im using correctly... (to be honest ive never had to measure resistance with one before), is this likely to be correct, or only measuring one speaker? or do the capacitors add resistance and make up for whats lost in the parallel configuration?

 

Multimeter doesnt make sense, each speaker is 8ohm. 3 parallel, why is it still measuring 8.

Im not connecting them up untill im ceetain. that 99% isnt quite enough.

 

once again, thanks logicprobe, im just paranoid :)

Edited by Master_Scythe

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Im not connecting them up untill im ceetain. that 99% isnt quite enough.

I think that the only way you're going to be certain is if you take it to a lab where they have the necessary equipment to measure impedance.

 

A lesser extreme would be to desolder the filters, use a DC multimeter to approximate individual speakers, and then use some maths I haven't seen before to calculate their impedance over the 20Hz-20KHz it's likely to see.

 

Rob.

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I think the logic part of my brain just kicked in:

 

a multimeter tests Impedance\Resistance by measuring how easy it is for a charge to pass between each of its probes, correct?

 

This suggests some form of current travelling.

 

Current will always take the path of least resistance.

 

these speakers are 8Ohm each (tested individually)

 

even when ALL are connected, due to being parallel

 

the Multimeter is only reading the first speaker in the chain (as its the least resistant).

 

 

 

Does this make sense? If so, im going to have to series-parallel the 3 speakers to get them to an acceptable level.

 

as i said before, where is Datafast when you need him, I have a feeling he could tell me in a second.

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I think the logic part of my brain just kicked in:

 

a multimeter tests Impedance\Resistance by measuring how easy it is for a charge to pass between each of its probes, correct?

 

This suggests some form of current travelling.

 

Current will always take the path of least resistance.

 

these speakers are 8Ohm each (tested individually)

 

even when ALL are connected, due to being parallel

 

the Multimeter is only reading the first speaker in the chain (as its the least resistant).

Heh, nah, not correct.

 

If you put a 1ohm, 2ohm and 3ohm resistor in parallel your multimeter will measure 0.54ohms.

 

You're getting funny readings because speaker impedance, to put it simply, is measured in AC - while you're measuring it in DC. (Any electronics man would likely kick my arse for saying it that way, though)

 

Rob.

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OK so my logic is incorrect, lol, fair enough.

 

Mathematically, unless we can be sure the capacitors alone are changing the impedance, there is no way it should be much higher than 2.6.

 

also disconnecting speakers is NOT changing what my multimeter is reading. so something is up.

 

Im gonna assume my multimeter simply isnt working at all because the Ohm should change at least a little when i connect\disconnect speakers.

 

Im gonna go series-parallel. Going up in Ohms is fine, better safe than sorry.

Edited by Master_Scythe

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df69 will just tell you what I did.

Plug the fuckers in!

 

They won't blow your amp unless you overload them and cause a short.

 

You still have said how many watts they are rated as.

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The smallest tweeter says 3-5w, the next says 5-8w, and the big ass woofer is only labeled for OHM not watts.

 

My amp can do up to 125w @ 6Ohm, so I wont be cranking these things anywhere past 1/4

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That big ass woofer will be 20w max!

 

They probably had a 25 or 30 watt rating when they came out being pushed by a 20w per channel amp.

 

I wouldn't push them at all!

 

What's that 125 rated into?

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