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Old 9th October 2010, 03:08 AM   #1
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Default Speaker Wiring Impedance Question

Alright fellars, so I just bought a KMD cabinet, with with four 16ohm Celestion speakers. Everything is working well, but the owner told me that the speakers were wired for a 16 ohm load. I have an impedance switch on my amp(4,8 and 16ohms), and don't want to blow anything up.

Seems to me like two speakers were run in series, and 1 speaker was run off of each of the two, in parallel. The wiring is a little hard to explain, maybe this is called a series-parallel, so I am posting a picture. One other thing, if I plug into one, or both of the amp input jacks, does that change the load? Any help, as always is appreciated!!y
P.S. even though the pics say 4 ohms, the speakers are actually 16 ohms.

http://i803.photobucket.com/albums/y...ngdiagram2.jpg

Last edited by Rotus623; 9th October 2010 at 03:35 AM.
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Old 9th October 2010, 03:15 AM   #2
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Here is the ACTUAL picture if it helps.
http://i803.photobucket.com/albums/y.../kmgwiring.jpg
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Old 9th October 2010, 03:47 AM   #3
Davey is offline Davey  United States
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Yep, those are wired in a series-parallel arrangement. The two on the left are wired in parallel with each other....likewise the two on the right. The two pairs are then wired in series with each other. Total impedance of the four is the same as single driver would be (16 ohms in your case.)

Cheers,

Dave.
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Old 9th October 2010, 04:12 AM   #4
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Cool thanks Dave. One little thing though. I thought for it to actually be run in series-parallel, it had to tie in the bottom two speakers as well. Also, the amp can in fact push 4 ohms (since it is switchable) so do you think there is a point to run the circuit in parallel to make it 4 ohms(maybe for some more wattage). Last thing, is it possible to run this load in 8 ohms? (Just curious)
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Old 9th October 2010, 04:47 AM   #5
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Quote:
Originally Posted by Rotus623 View Post
Cool thanks Dave. One little thing though. I thought for it to actually be run in series-parallel, it had to tie in the bottom two speakers as well. Also, the amp can in fact push 4 ohms (since it is switchable) so do you think there is a point to run the circuit in parallel to make it 4 ohms(maybe for some more wattage). Last thing, is it possible to run this load in 8 ohms? (Just curious)
You could run them all in parallel and get 4 ohms but your amp won't put out any more power at 4 vs 16 ohms and at 4 ohms you'll have more power lost in the wiring from speaker to amp. I*R and R is a constant. Doubling the current quadruples the loss and you're quadrupling the current from 16 to 4 ohms so 16 times more loss.

A solid state amp that puts out constant voltage (most are) _will_ deliver more power at lower impedances, a 'trick' some speaker manufacturers have used to make sensitivity seem better. Your transformer coupled amp (presumably tubes since transformers are easily avoided with solid state) changes the voltage/current relationship so that the power doesn't change with impedance - except for already mentioned cabling losses at lower impedances.

G
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Old 9th October 2010, 05:14 AM   #6
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"Your transformer coupled amp (presumably tubes since transformers are easily avoided with solid state) changes the voltage/current relationship so that the power doesn't change with impedance - except for already mentioned cabling losses at lower impedances."

Yes sir, it is a 100W valveking head. Thanks for the great answer. I still am wondering though, if my speaker configuration is in fact run in series-parallel. I thought in order for this to be the case, the bottom two speakers had to be run together. (And mine are not) And does it change anything or make a difference if I fun my amp into one of the cabinet inputs or both?
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Old 9th October 2010, 05:50 AM   #7
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Quote:
Originally Posted by Rotus623 View Post
"Your transformer coupled amp (presumably tubes since transformers are easily avoided with solid state) changes the voltage/current relationship so that the power doesn't change with impedance - except for already mentioned cabling losses at lower impedances."

Yes sir, it is a 100W valveking head. Thanks for the great answer. I still am wondering though, if my speaker configuration is in fact run in series-parallel. I thought in order for this to be the case, the bottom two speakers had to be run together. (And mine are not) And does it change anything or make a difference if I fun my amp into one of the cabinet inputs or both?
If your rotated the group 90 degrees the sides would be in parallel rather than the bottom/top. It's all perspective. To prove it to yourself, disconnect one speaker and measure the DC resistance which will likely be less than 16. Reconnect it into the network with the other 3 in series/parallel and measure the group. It should be very nearly identical to the single driver. Reasons for a difference is possible variations between the drivers plus the wiring.

G
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Old 9th October 2010, 02:04 PM   #8
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Cool. That sounds like a great idea. That way if I ever get confused about it again I can just check it myself. (I didn't realize that I could do that)
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Old 9th October 2010, 02:29 PM   #9
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When I check the impedance of this setup, I am getting 4 ohms. Strange. I really do believe that in order to run it in series-parallel, the other two speakers have to be run together as well.
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Old 10th October 2010, 03:22 PM   #10
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Originally Posted by stratus46 View Post
If your rotated the group 90 degrees the sides would be in parallel rather than the bottom/top. It's all perspective. To prove it to yourself, disconnect one speaker and measure the DC resistance which will likely be less than 16. Reconnect it into the network with the other 3 in series/parallel and measure the group. It should be very nearly identical to the single driver. Reasons for a difference is possible variations between the drivers plus the wiring.

G
So why am I measuring 4 ohms if the speakers are in fact 16 ohms? The resistance is measuring as if the whole setup is being run in parallel. Are you guys sure that the wiring is in series-parallel?
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