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Old 3rd January 2013, 02:04 AM   #1
WILD1 is offline WILD1  United States
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Default Altec 604 C

Hi everyone
Haven't posted in a while but there is a local man wanting to sell an Altec 604C coaxial. I have a question about the impedance's that I want to check. What is the individual impedance for each of the drivers low and high. All the literature that I can find says 16 nominal. They do not say whether that is for each driver or a combination at the crossover . It would seem to me that each driver would have an impedance of 16 ohms which makes sense to me because in parallel they would draw 8 ohms. 16 ohms at each driver terminal and 8 ohms at the input to the crossover divider. Now I realize that those readings are nominal over a wide range of frequencies. Why I ask is because I want to check the drivers when I go look at it. On Ebay there is a guy listing two 604Cs and saying the impedance of the drivers are 8 ohms and he is showing a reading of the cone driver of one at 10.5 ohms and calling it an 8ohm driver. On the other speaker he is showing an impedance of 7.5 ohms at the cone driver and 7.6 at the horn driver which would be more normal for an 8 ohm driver. In another ad a lady is showing one and saying the impedance at the crossover or divider input is 16 ohms. This doesn't make sense unless they are driving the two drivers in series. If someone can clarify this for me I would appreciate it. I just want to be able to walk in check the drivers and know what he has.
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Tom Wild
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Old 3rd January 2013, 11:47 PM   #2
Ron E is online now Ron E  United States
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I measured what the owner said were 604C's - the woofers measured 8.1 ohms DC and the tweeters 7.5 ohms. YMMV as I am not an "altec expert".

The crossover does not change the impedance in the way you are thinking - there is no series or parallel effect on impedance from a crossover.
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Old 3rd January 2013, 11:53 PM   #3
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Hi Wild1, They are nominal 16 ohms and often have a DC resistance of 8-10 ohms. That is if they are original comes and diaphragms.
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Old 3rd January 2013, 11:55 PM   #4
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Old 3rd January 2013, 11:57 PM   #5
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Wow, that derailed quickly
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Old 4th January 2013, 12:02 AM   #6
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Old 4th January 2013, 12:05 AM   #7
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we luv ya , Big Cal ........ and you know that ......

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Old 4th January 2013, 05:52 PM   #8
WILD1 is offline WILD1  United States
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Default Got It!

Well I just got back from the bg H [Houston] . Saw some old friends from college and saw the speaker. The impedance of each driver was 12.4 which I would think a 16 ohm driver would be. This thing looks new other than two tears to the original cone which I think can be fixed. He tore it getting it out of the cab. Cost me $200. Now all I need to do is find another one for $200 LOL. The crossover was not hooked up to it but I'm thinking that impedance at the input of the crossover with the two drivers hooked up is going to be 8ohms. I just can't see how you can not have a cumulative effect from combining two impedance sources In parallel a decrease and in series an increase. Although I have been wrong before. Will post result.

Tickled pink,
Tom Wild
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Old 4th January 2013, 07:43 PM   #9
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Hi Tom, glad to hear you are now the proud owner of a 604. I know I felt the same way when I got mine.

On to the XO and impedances. If you were dividing the entire frequency spectrum between two drivers then yes you would divide the impedance in two - but you're not doing that. You have divided what each speaker gets via the crossover so each part of the spectrum only sees one driver so the rated impedance stays the same. The woofer is offering 16 ohms nominal to the amp as it and only it are delivering the bass notes. Same with the tweeters.
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Old 4th January 2013, 11:36 PM   #10
WILD1 is offline WILD1  United States
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Default I get it

Appreciate it Cal and I think I get it now. When I got them into the shop and measured the impedance it was also more like what you guys said it would be 7.9 to 8.1. It seems that you have a fancy for Tequila [Margaritaville]. Next time your in Texas give me a holler and we will spend a day eatin barbecue, drinking good mexican beer & siping some fine vintage tequila while listening to my 604s.

Thanks,
Tom Wild
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