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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Fri Sep 07, 2012 2:16 pm
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And there you have it! The only time I use series is if it is a single speaker (if it gets quiet real fast, I pull the plug!) Other than that, it is for impedance matching as in a 4x10 cabinet.

While some people have it in their heads that Series wiring gives a different tone, I have to agree that I have never been able to hear any difference.

Art


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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Fri Sep 07, 2012 5:47 pm
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Art1 wrote:
And there you have it! The only time I use series is if it is a single speaker (if it gets quiet real fast, I pull the plug!) Other than that, it is for impedance matching as in a 4x10 cabinet. While some people have it in their heads that Series wiring gives a different tone, I have to agree that I have never been able to hear any difference. Art


Too funny - one in serial :lol:
Probably the tone sound differences will be hard to discern.
Parallel it is.
On my end, equally matched ohms between speakers.
None of this mix and match stuff.
Very good thread.

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Fri Sep 07, 2012 6:33 pm
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Really, a good output tranny in a tube amp with wattage of 5 to 50 watts, is pretty forgiving. I've seen ppl redo Harmon-Kardon Citations with humongous OPT's, not even put a load onto the OPT when measuring bias. I would NOT recommend this, but no damage was done to those OPT's.

From what I've seen in more damaged direct coupled solid-state amps. Prolly why many have output fuses in them.

Remember, the impedance is only value at 1kHz, 1 watt load. The actual range of impedance can vary from speaker to speaker. Even if they are nominally rated at a set ohms. So. like the graph below, You run a risk of damage, if you play a lot around 400Hz ---- even though it's nominal value is 4-ohms (at 1KHz). Esp, if the dip at 300Hz is closer to zero.


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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Fri Sep 07, 2012 7:49 pm
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BMW,

We don't want to confuse the non-technical people who may be reading this thread with too many facts. :wink: :lol:

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Fri Sep 07, 2012 8:06 pm
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Exactly. Keep it user friendly. Thanks.
But, love reading the info and charts. Good stuff.
Appreciate it very much.
After time, more and more makes sense.
Just gotta keep plugging away
and avoid the slights. Right, Bluesy?

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Fri Sep 07, 2012 8:31 pm
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The main thing when speakers fail and the amp gets quiet is to shut it down and not keep banging away trying to figure it out....I've blown both speakers in a 2x10 Vibrolux Reverb and was in the middle of a song at a gig,...with all the volume of the rest of the band I didn't know it for about 30 seconds....then I shut it off and got another amp....a check with a volt meter the next day told the tale....like BMW said the OT in the amp was fine and forgiving....thank goodness.


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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 12:46 am
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Just to revisit the series-parallel spkr configuration, this is a subtle difference. Tone is not the right word, sound stage would be more accurate. Given the same amp, cab, and spkrs, the best discription I can give you folks: Parallel yields a balanced hi-fi production. Series yields a less controlled and more raw production. Not all folks will hear the difference, but musicians with dog-ears can hear the difference. Bill, I can't give you charts & graphs, but this is a reality. This is very akin to changing the NFB ratio in a BF Fender or earlier Marshall amp. Again, it's a subtle difference. Art

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 5:16 am
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This from DIY audio:

How do you run speakers in series?
It is not suggested that you run speakers in series. No two speakers will be exactly identical, even if they are the same model from the same manufacturer. This means that they will act slightly different from each other when presented with the same input signal. When wired in series, these differences will cause distortion in the form of back EMF.

There is a mountain of info on the net with mathematical formulas, graphs and charts about series vs parallel wiring but I found this to be the simplest explanation to help out the technically challenged amongst us. :wink:

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 5:21 am
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BMW
I was going to bring that up before but thought better of it. But now that you brought it up... looking below at the C12N Jensen, it appears that either Impedance or resistance changes with amplitude and frequency as well. Even though this is an 8 ohm Nominal impedance, this one appears to be 15 or 16. (not all manufactures show the scale on the right side of the graph.)

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 8:22 am
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Art1 wrote:
BMW
I was going to bring that up before but thought better of it. But now that you brought it up... looking below at the C12N Jensen, it appears that either Impedance or resistance changes with amplitude and frequency as well. Even though this is an 8 ohm Nominal impedance, this one appears to be 15 or 16. (not all manufactures show the scale on the right side of the graph.)

Image Art


Art. I have some of each 1960s Jensen C12N C12P C12Q C12R speakers for my project.
Given the above specs and graph, how would the brighter C12P C12Q C12R speakers compare.
Say from the larger to smaller voice coil speakers
or the darker to brighter speakers, etc.

What do you think? Toppscore
***Art, again. Thanks for the info. Toppscore :)

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 8:25 am
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aclempoppi wrote:
Just to revisit the series-parallel spkr configuration, this is a subtle difference. Tone is not the right word, sound stage would be more accurate. Given the same amp, cab, and spkrs, the best discription I can give you folks: Parallel yields a balanced hi-fi production. Series yields a less controlled and more raw production. Not all folks will hear the difference, but musicians with dog-ears can hear the difference. Bill, I can't give you charts & graphs, but this is a reality. This is very akin to changing the NFB ratio in a BF Fender or earlier Marshall amp. Again, it's a subtle difference. Art


Sorry. I disagree. It is irrelevant if you have two 4-ohm speakers connected in series or two 16 ohm speakers connected in parallel. The amp still sees 8 ohms. The NFB point is taken from one of the speaker taps on the output transformer. The NFB ratio depends on the design of the entire loop, not just where the signal is taken from.

"Soundstage" or dispersion is affected by speaker orientation as I described earlier. A two speaker system will have a different soundstage depending on whether it is oriented vertically or horizontally. Mounted vertically, a two speaker system will have a broad horizontal dispersion and a narrow vertical dispersion. Mounted horizontally, it is the opposite: broad vertical, narrow horizontal. This is due to acoustic comb filtering effects between the two speakers, which is an entirely different subject. The original THX certified speakers are mounted vertically for maximum horizontal dispersion inorder to cover a wide audience. You can learn more about this at http://www.thx.com.

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Last edited by bluesky636 on Sat Sep 08, 2012 8:57 am, edited 1 time in total.

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 8:49 am
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Art1 wrote:
BMW
I was going to bring that up before but thought better of it. But now that you brought it up... looking below at the C12N Jensen, it appears that either Impedance or resistance changes with amplitude and frequency as well. Even though this is an 8 ohm Nominal impedance, this one appears to be 15 or 16. (not all manufactures show the scale on the right side of the graph.)

Image

Art


Impedance changes with frequency. Signal amplitude has nothing to do with it. A loudspeaker is an LCR network, just like a guitar pickup with volume and tone controls. Manufacturers are very inconsistant in how they measure speaker impedance. Some use the minimum value (the lowest value after the resonant peak, while others use a "nominal" value. The nominal impedance is usually calculated to be 1.15 times the minimum value. But even that is not consistant. Nominal impedance is not necessarily measured at 1 KHZ. Based on that graph, the minimum impedance appears to be just slightly above 7 ohms. 7 ohms x 1.15 = 8.05 ohms. It is an 8 ohm speaker in Jensen's mind.

Note that in BMW2002Ti's impedance graph, the nominal impedance is 1.15 times the minimum impedance. It just happens to occur at 1KHZ. In Art's graph, nominal impedance occurs at 400HZ.

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Last edited by bluesky636 on Sat Sep 08, 2012 9:09 am, edited 2 times in total.

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 9:05 am
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Arc-n-spark wrote:
This from DIY audio:

How do you run speakers in series?
It is not suggested that you run speakers in series. No two speakers will be exactly identical, even if they are the same model from the same manufacturer. This means that they will act slightly different from each other when presented with the same input signal. When wired in series, these differences will cause distortion in the form of back EMF.

There is a mountain of info on the net with mathematical formulas, graphs and charts about series vs parallel wiring but I found this to be the simplest explanation to help out the technically challenged amongst us. :wink:


These are all general claims. The same holds true for parallel speakers. Back EMF exists regardless of how the speakers are wired. Back EMF depends on the speaker design. Total back EMF will include all speakers regardless of how they are wired. A GOOD loudspeaker designer knows how to account for these effects.

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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 3:29 pm
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Toppscore wrote:
Art1 wrote:
BMW
I was going to bring that up before but thought better of it. But now that you brought it up... looking below at the C12N Jensen, it appears that either Impedance or resistance changes with amplitude and frequency as well. Even though this is an 8 ohm Nominal impedance, this one appears to be 15 or 16. (not all manufactures show the scale on the right side of the graph.)

Image Art


Art. I have some of each 1960s Jensen C12N C12P C12Q C12R speakers for my project.
Given the above specs and graph, how would the brighter C12P C12Q C12R speakers compare.
Say from the larger to smaller voice coil speakers
or the darker to brighter speakers, etc.

What do you think? Toppscore
***Art, again. Thanks for the info. Toppscore :)


Technically, the only difference between those is the power rating (provided they are all the same impedance. N=50, P about 45, Q=35, R=25. If these are 60's 70's then the power handling is probably somewhat below that by now. As for comparison, let "your" ears be the judge. I can't do that for you.

So, build a cabinet, put the speakers in and let us know how they sound.

Art


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Post subject: Re: While we are on the subject of speaker cabs - Wattage
Posted: Sat Sep 08, 2012 7:38 pm
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There is a misunderstanding Bill, the point is not that the NFB and spkr hook-up are related. It's the sound of control and less control. It's just that the two are a similar change to the percieved sound. Again, it is a subtle difference. Art

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