Oh Impedance gurus....Question?

[jgcable]

I have a 2 x 12 cab with Altec Lansing 300w Whiteframes in it. The impedance is not marked so I checked them with my Fluke meter. They measure 6 ohms each. I consider them 4 ohm speakers and have been using them as such with no problems at all.
The cabinet is currently wired in stereo 4 (6) ohms per side.
I want to try this cab with my Mark III. It has 2 x 4 ohm and 1 x 8 ohm speaker outputs on the back of it.
According to my manual, I need to use a series box which is basically a box with 3 jacks on it. One jack gets plugged into the Mesa Boogie 8 ohm speaker jack. The other 2 jacks go to the left and right jacks on my speaker cabinet.
I am assuming that a "series" box is basically 1 jack going to the amp wired into the other 2 jacks wired in series + to - to + to -.
Is this correct?
I have never seen a series box before but if this is what it is I can certainly make one in a few minutes.

[markD]

Re: Oh Impedance gurus....Question?

i am good with ohm-age, and i have NEVER heard of that.

[Deneb]

Re: Oh Impedance gurus....Question?

I know of what you're talking about, but I've never seen one.

This would be my guess,

You've got an 8 ohm 4, and whatever else on your amp. You want to go into an 8 ohm load, but you do not have 2 8 ohm outs.

I would imagine, what it would do, is take the impedance, from the SPEAKERS (saying in this instance, two 16 ohm cabinets) and make it paralell, then to the amp.

I don't know that there are any dummy loads in it or anything of that nature. As long as the impedance coming from the box, matches the value you want, and it's GOING to a load, everything is fine.



Also, You can safely mismatch a few loads, in "theory" it's harder on the transformer or the tubes, but in reality (safe mismatches SHOULD BE placed in your boogie book, I know mine has them) are fine, and are not harming anything (again CHECK YOUR MANUAL AND SEE IF IT SAYS THIS.) You can DL a triples manual from the Mesa site (this is saying if you're seaker section isn't the same as mine) and see what I'm talking about.

[jgcable]

Re: Oh Impedance gurus....Question?

Altec Lansing told me that their older speakers like the 300w Whiteframes usually fell between the 4 and 8 ohm range. They told me that if its under 6 ohms they consider it a 4 ohm speaker, if its under 12 ohms they consider it an 8 ohm speaker and if it is over 12 ohms they consider it a 16 ohm speaker. Have you ever heard such a thing?

[Deneb]

Re: Oh Impedance gurus....Question?

It tells me that they really need to work on their QC :P

However, think about it this way. You've had to have heard of a safe mismatch before, just think of it that way.

[siggy14]

Re: Oh Impedance gurus....Question?

Technically those speakers are probaly both 8 Ohm Speakers, being that your meter could be slightly off and not to mention speakers are not always what they read on a meter, for example most marshall cabinets actually read 15 Ohms.

If the cab does not have a mono input then you can use a series box. If it is like most mesa's it probaly allready has two 4 ohm outputs and you can just plug into each of those. If not a series box can be made.

[jgcable]

Re: Oh Impedance gurus....Question?

If I assume the speakers are 8 ohms then I can take your suggestion and plug them into the two 4 ohm outputs which is basically a series box built into the amp. I'll try it tonight. Thanks..

[OnlineStageGear]

Re: Oh Impedance gurus....Question?

[ QUOTE ]
Technically those speakers are probaly both 8 Ohm Speakers, being that your meter could be slightly off and not to mention speakers are not always what they read on a meter, for example most marshall cabinets actually read 15 Ohms.

[/ QUOTE ]

They are 8 ohm. Your meter is measuring resistance and speakers are rated in Impedence which is both reactance and resistance.

[ QUOTE ]
If I assume the speakers are 8 ohms then I can take your suggestion and plug them into the two 4 ohm outputs which is basically a series box built into the amp. I'll try it tonight. Thanks..


[/ QUOTE ]

Plugging the 2 speakers into the 2 4 ohm labeled outputs should be fine. The back of an amp usualy is not series if it has 2 speaker outs, it is probably parallel.

Matt

[Cleveland Metal]

Re: Oh Impedance gurus....Question?

I've noticed that most speakers read under what they are rated at. 8 at 6, 16 at 13 etc...

[Shawn Lutz]

Re: Oh Impedance gurus....Question?

kind off topice jc but do you like those speakers?

[jgcable]

Re: Oh Impedance gurus....Question?

The speakers are awesome. I will tell you one thing though. If you like your speakers to break up then look elsewhere. These can be pushed beyond belief with no farting, popping or loss in clarity. They remind me alot of the old EV's and JBL's that we used to put in our Marshall cabs. We would remove the Celestions and chuck them. In the early 80's Celestions were just plain old stock speakers.

[jgcable]

Re: Oh Impedance gurus....Question?

[ QUOTE ]
[ QUOTE ]
Technically those speakers are probaly both 8 Ohm Speakers, being that your meter could be slightly off and not to mention speakers are not always what they read on a meter, for example most marshall cabinets actually read 15 Ohms.

[/ QUOTE ]

They are 8 ohm. Your meter is measuring resistance and speakers are rated in Impedence which is both reactance and resistance.

[ QUOTE ]
If I assume the speakers are 8 ohms then I can take your suggestion and plug them into the two 4 ohm outputs which is basically a series box built into the amp. I'll try it tonight. Thanks..


[/ QUOTE ]

Plugging the 2 speakers into the 2 4 ohm labeled outputs should be fine. The back of an amp usualy is not series if it has 2 speaker outs, it is probably parallel.

Matt

[/ QUOTE ]

Matt, that brings up another question though. I have a Fluke 12 multimeter. When I check my other speakers they read:

My 4 ohm Peavey Scorpions read 4.1 ohms on my meter
My 8 ohm 90w Black Shadows read 8.2 ohms on my meter
My Celestion V30 8 ohm speakers read 8.1 ohms on my meter
My Eminence Patriot 16 ohm speaker reads 16.3 ohms.
With that said... why do the Altec Lansings read 6.12 ohms if they are actually 8 ohms?

Thanks in advance.. JG

[Deneb]

Re: Oh Impedance gurus....Question?

I would motion to say your meter is reading correctly.

Okay, this is a little something about Impedance (Z) from one of my beginning electronic books. I would get my advance shit, but frankly, they are packed away in the garage.

Anyway,

Resistance has a phase angle of 0 degrees, and Reactance has a phase angle of +/- 90 degrees. Therefore, when R and X are cominged, the phase angle of the ac circuit is between 0 and + 90 degrees. Futher, the ohms of resistance, and reactance must be combined by phasor addition, because of the 90 degree phade angle between the two. The sultant sum is called Impedance, with the symbol Z, which is the total opposition of resistance, and reactance to a sine-wave alternating current.

Here is a link from some college site on Z.

http://hyperphysics.phy-astr.gsu.edu...ric/imped.html

[jgcable]

Re: Oh Impedance gurus....Question?

[ QUOTE ]
I would motion to say your meter is reading correctly.

Okay, this is a little something about Impedance (Z) from one of my beginning electronic books. I would get my advance shit, but frankly, they are packed away in the garage.

Anyway,

Resistance has a phase angle of 0 degrees, and Reactance has a phase angle of +/- 90 degrees. Therefore, when R and X are cominged, the phase angle of the ac circuit is between 0 and + 90 degrees. Futher, the ohms of resistance, and reactance must be combined by phasor addition, because of the 90 degree phade angle between the two. The sultant sum is called Impedance, with the symbol Z, which is the total opposition of resistance, and reactance to a sine-wave alternating current.

Here is a link from some college site on Z.

http://hyperphysics.phy-astr.gsu.edu...ric/imped.html

[/ QUOTE ]

I understand that the reading I am getting with my meter is resistance. My question is... why do all my other speakers measure extremely close to their advertised and labeled impedance yet my Altec Lansings don't? What could be different?

[siggy14]

Re: Oh Impedance gurus....Question?

[ QUOTE ]
[ QUOTE ]
I would motion to say your meter is reading correctly.

Okay, this is a little something about Impedance (Z) from one of my beginning electronic books. I would get my advance shit, but frankly, they are packed away in the garage.

Anyway,

Resistance has a phase angle of 0 degrees, and Reactance has a phase angle of +/- 90 degrees. Therefore, when R and X are cominged, the phase angle of the ac circuit is between 0 and + 90 degrees. Futher, the ohms of resistance, and reactance must be combined by phasor addition, because of the 90 degree phade angle between the two. The sultant sum is called Impedance, with the symbol Z, which is the total opposition of resistance, and reactance to a sine-wave alternating current.

Here is a link from some college site on Z.

http://hyperphysics.phy-astr.gsu.edu...ric/imped.html

[/ QUOTE ]

I understand that the reading I am getting with my meter is resistance. My question is... why do all my other speakers measure extremely close to their advertised and labeled impedance yet my Altec Lansings don't? What could be different?

[/ QUOTE ]

Most speakers in marshall cabs dont read close either, like i said i have yet to find a marshall cab that isnt 1 ohm off. My mesa boogie cab also reads 8ohms so i know what you mean, maybe mesa just looks for higher rated so it does not have to answer a million questions from customers, who knows.