More speaker questions

[jgcable]

QUESTION 1: I checked the specs between the Eminence MOD12 and the Eminence M12 and I see very little difference. The MOD12 is stock in many modeling amps and the M12 is what they claim to be very similar to a GB12 (Celestion Vintage 30).
What are the important specs that I should be looking at. I want to try my MOD12's in a 2x12 cabinet with my Soldano Astroverb and although the website says they are designed for modeling amps, I can't see much of a difference in specs.

QUESTION 2:
Can different speakers be mixed in a 4x12 cabinet? I have 4 4 ohm Peavey 25watt Peavey Scorpions and 2 4 ohm Altec Lansing 300watt white frames. Would I cause a problem if I ripped 2 of the Scorpions out of my bottom of my 4x12 cabinet and replaced them with the Altec Lansings?

QUESTION 3:
My Altec Lansing speakers measure 6.5 ohms per the Altec Lansing website but when I measure them I get 4.6 ohms. It I paired one of them up to one of my Eminence MOD12's which measures 8.2 ohms in series I would get either 12.8 ohms or 14.7 ohms (if you use Altec Lansings figures.
Would this combination work for a tube amp that requires a 16 ohm load?

[zeegler]

Re: More speaker questions

Answer 1: I don't know. I can't see why modelling amps would require different speakers in the first place.

Answer 2: Mixing speakers, as long as the required load is the same, won't harm anything.

Answer 3: 14.7 would be fine, because as I understand it, measured impedance is usually a little lower anyway, but I'm not sure why you're getting 12.8. Have you checked the calibration of your meter?

[jgcable]

Re: More speaker questions

I am using a Fluke 12. I have tested it on known caps and resistors and it is dead nuts accurate. The Altec Lansings thing is really blowing my mind. The speakers are clearly marked 417-8c. They also are clearly marked 8 ohms. I talked to the guy I bought them from many years ago and he told me that they were never reconed and as far as he knew they are completely original and 8 ohms each. They certainly look orginal. He was using them with a solid state Randall RG100ES-SS so impedance wasn't that critical to him. When I measure them with my Fluke 12 meter they read a tiny bit over 4 ohms each. I just don't get it.

[fuel0707]

Re: More speaker questions

Take this for what it's worth (which probably isn't much) but here's my two cents on your questions.

1) I could see that a speaker for a modelling amp might be a flatter and/or wider response speaker whereas a speaker designed for a traditional amp might be voiced differently to bring out unique characteristics of that amp. After all, no one wants a full-range high-fidelty speaker setup to use with a blazing Marshall.

2) As long as the impedances match, I can't see why there would be a problem. Ohm's law still applies, after all. [img]images/icons/smile.gif[/img]

3) From reading some articles from Gerald Weber, it sounds like measuring speaker is techincally difficult - depending on what the input signal is can effect the impedance reading. Therefore, a speaker rated at "8 ohms" is nominally 8 ohms depending on a specific measurement condition. That said, I've read it in several places that tubes amps are generally more tolerant of impedance mismatches than solid staters.

[zeegler]

Re: More speaker questions

Originally posted by John D.:
That said, I've read it in several places that tubes amps are generally more tolerant of impedance mismatches than solid staters.

<font size="2" face="Verdana, Helvetica, sans-serif">[img]graemlins/scratchhead.gif[/img] That's very odd. I've heard exactly the opposite. From what I understand, if you underload a tube amp too severely, you will find yourself looking to replace a rather expensive output transformer.

[jgcable]

Re: More speaker questions

I called Altec Lansing and spoke to their tech support guy. He has been there forever. He told me how to check the actual impedance of the speakers and it is a nightmare that I do not want to handle. It involves audio occilators, volume pots, 400hz 3 volt amplifiers. etc...
He told me that when using a standard multimeter set to DC resistance:
4 ohm speakers read just about 4 ohms
8 ohm speakers read around 6.5 ohms
16 ohm speakers read around 12.5-13.5 ohms
Because my Altec Lansing speakers are measuring 4 ohms he guessed that they must have been reconed at one point and 4 ohm coils were used. He did confirm that they are very high end speakers and gave me a company called Great Planes Audio who specializes in working on Altec Lansing speakers if I want to return them to 8 ohms. He uses all original Altec Lansing parts.

[CZSER]

Re: More speaker questions

It's widely known that 2 Greenback + 2 Vintage 30 are a grat sounding couple, so... Try out yours!(and let us konw)

[fuel0707]

Re: More speaker questions

Originally posted by zeegler:
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by John D.:
That said, I've read it in several places that tubes amps are generally more tolerant of impedance mismatches than solid staters.

<font size="2" face="Verdana, Helvetica, sans-serif">[img]graemlins/scratchhead.gif[/img] That's very odd. I've heard exactly the opposite. From what I understand, if you underload a tube amp too severely, you will find yourself looking to replace a rather expensive output transformer. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I just did a quick search and found this link about mismatched output/speaker impedances and tube amps: link

Scroll down the left side to find "Match speakers to output impedance?". The short answer is that the tube amp will run less efficiently with a mismatched impedance, but isn't too likely to burn up an amp. That said, I don't think I'll try it personally. [img]images/icons/grin.gif[/img]

[zeegler]

Re: More speaker questions

Yeah, I wouldn't try it with either of my tube amps. I'm not a gambling man.

[OnlineStageGear]

Re: More speaker questions

Originally posted by jgcable:
I called Altec Lansing and spoke to their tech support guy. He has been there forever. He told me how to check the actual impedance of the speakers and it is a nightmare that I do not want to handle. It involves audio occilators, volume pots, 400hz 3 volt amplifiers. etc...
He told me that when using a standard multimeter set to DC resistance:
4 ohm speakers read just about 4 ohms
8 ohm speakers read around 6.5 ohms
16 ohm speakers read around 12.5-13.5 ohms
Because my Altec Lansing speakers are measuring 4 ohms he guessed that they must have been reconed at one point and 4 ohm coils were used. He did confirm that they are very high end speakers and gave me a company called Great Planes Audio who specializes in working on Altec Lansing speakers if I want to return them to 8 ohms. He uses all original Altec Lansing parts.

<font size="2" face="Verdana, Helvetica, sans-serif">Measuring a speaker with an Ohm meter is actually measuring Resistance, not Impedance. A speakers Impedance is close to the same as it's resistance, so that is why a lot of people will measure it that way, but you are supposed to multiply the resistance of a speaker buy either 1.2 or 1.3 (I forget) to get it's Impedance.

Matt