N.O.D.
18 posts
Jul 10, 2010
5:54 AM
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Hi i have a Fender BJ with extensive mods with a multi tap trany 4 8 16 ohms,I fitted with a 35 watt 8 ohms GB-10 Celestion
i have 2x8'inch 16ohms 15 watt 1960 Magnavox speakers
with the wizzer cone in the middle
i can wire these up to run at 8,ohms or i can wire them to run at 16,ohms
if i wire them up for 8,ohms or run at there true 16ohms capacity does this effect tone,
i allso have 2x8 vintage magnavox 4,ohms 20 watt speakers speakers will this allso effect tone,
so what im realy trying to say i guess is if i fitted
2x8 inch speakers in the amp,
whats the difference of running 4 8 or 16,ohms speakers
is it a tone thing or and output thing
will the amp perform better with the differnt Ohm speakers?
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Yup im confused
& scratching my arse :/
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Greg Heumann
642 posts
Jul 10, 2010
8:28 AM
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NOD - I don't know the answer to your question - I'm told it doesn't make much difference but others will know better.
You can also just try it - shouldn't be too hard - and use your ears. I'd like to know what you learn.
One thing though, you said you have two 16 ohm speakers - and you can wire them as 8 ohms or 16. I only know of two ways to connect 2 speakers: parallel, which will give you 8 ohms, or series, which will get you 32 ohms. How can you wire them for 16 ohms?
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/Greg
Last Edited by on Jul 10, 2010 8:29 AM
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rharley5652
199 posts
Jul 10, 2010
2:15 PM
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NOD / hope this helps,.like Greg says best is to wire them and use your ears <> AN there is a section that talks about wirin series an parallel ,.
Say's Gerald, connecting two speakers in parallel is an old trick to smooth out speaker response and enhance the damping of either speaker.
@ Greg,.. There is a lotta good readin here I'm sure ya like ,.Ya a Kalamazoo big time builder ,.Might find some tricks for em ?/
Copy link below <>
http://www.webervst.com/sptalk.html
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Simply Unique Kustom Mic's By Rharley
Last Edited by on Jul 10, 2010 3:10 PM
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N.O.D.
20 posts
Jul 10, 2010
8:35 PM
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Yo Greg ya Right i had a tinker out in my Kennal 2x16 ohms can be wired to run 8 or 32 ohms only:(
But i was made to adapt and over come situations:)
my speakers rated at 16,Ohms but reads 12 ohms on my multi meter,readings vary on all speakers within there Ohms rateing they may be above or below by a few points
we both understand wireing the 2 speakers in parallel
2 x 16 ohms gives us 32 ohms,
i wired 2 x 8 inch speakers parallel
1 x 16ohms 1 x 4ohms this = 16ohms
them i did the same but
i wired 2 x 8 inch speakers parallel
1 x 16ohms 1 x 8ohms this = 19ohms
so it looks like i can use a 16 x 8 or 4 ohms speaker to achieve my gole on that aspect:)
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Cheers Big EarsL:)
Last Edited by on Jul 11, 2010 1:13 AM
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Greg Heumann
646 posts
Jul 11, 2010
8:06 AM
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@NOD - I'm afraid you still don't have it quite right.
"we both understand wireing the 2 speakers in parallel 2 x 16 ohms gives us 32 ohms"
No -resistance is added together when wiring IN SERIES.
"i wired 2 x 8 inch speakers parallel 1 x 16ohms 1 x 4ohms this = 16ohms"
This isn't correct. The formula for two resistors in parallel is (R1*R2)/(R1+R2) - in this case (16*4)/(16+4) = 3.2 ohms. Moreover, I would NOT mix a 16 and 4 - a lot more current will flow through the 4 than the 16 and might blow it.
i wired 2 x 8 inch speakers parallel 1 x 16ohms 1 x 8ohms this = 19ohms
No, a 16 and an 8 in parallel yield 5.33 ohms.
Note when you wire two resistors in parallel, current is free to flow through either resistor without going through the other. Plus some more can go through the other one. Therefore, resistance of a circuit with parallel resistors is always LESS than the value of the resistor with the LEAST resistance.
Also -when 2 resistors of the SAME VALUE are wired in parallel, the result is always half the value - 2x 16 ohm speakers in parallel = 8 ohms. 2x 8 ohm speakers = 4 ohms, etc.
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/Greg
Last Edited by on Jul 11, 2010 8:15 AM
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N.O.D.
23 posts
Jul 11, 2010
6:22 PM
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Hi Greg iv'e lead you a stray mate
i did the experiment i should have said i wired the speakers in SERIES Not Parellel as i mention OOPS!!
we both understand wireing the 2 speakers in Series
2 x 16 ohms gives us 32 ohms,
i wired 2 x 8 inch speakers in Series
1 x 16ohms 1 x 4ohms this = 16ohms
them i did the same but
i wired 2 x 8 inch speakers in Series
1 x 16ohms 1 x 8ohms this = 19ohms
But i hear what you are saying about over loading the 4ohms speaker if wired with a 8 ohms,
Im going to play it safe just run my 2 by 16ohms in Parellel thanks mate you are a great help an Benfit to the MBH Forum:)
this is the link i used to find out the info on speaker wireing:)
http://www.usspeaker.com/speaker%20wiring-1.htm
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Ya Bloods worth Bottleing mate!!!!
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Jim Rumbaugh
261 posts
Jul 11, 2010
9:27 PM
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Amp out put is best when the speaker's ohms equals the amps ohms.
The resistance of the coil measured with an ohm meter is not the true "ohms" of a voice coil. Go by the manufacurer's specifications.
I saw posted "i have 2x8'inch 16ohms 15 watt ...speakers ... i can wire these up to run at 8,ohms or i can wire them to run at 16,ohms"
I am cofused. 2 "16 ohm" speakers can be ran as:
1) 8 ohms in parallel
2) 32 ohms in series
3) 16 ohms if you use just one speaker
4) or you have a rare speaker with 3 lugs that can be tapped at either 8 or 16 ohms.
=====================================
my recomendation
====================================
1)wire the 2 16 ohms in parrellel for an 8 ohm cabinet with 30 wats of speakers
2)wire the 2 4 ohms in series for another 8 ohm cabinet with 40 watts of speaker
if you want to use either 8 ohm cabinet with your "35 watt 8 ohms GB-10 Celestion", set the tap at 4 ohms. (assuming you will be running the 2 cabinets in parrallel)
BY THE WAY. are you aware of speaker phasing??? making sure they are all pushing out at the same time.
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intermediate level (+) player per the Adam Gussow Scale, Started playing 2001
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5F6H
239 posts
Jul 12, 2010
4:30 AM
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Jim Rumbaugh - "my recomendation
====================================
1)wire the 2 16 ohms in parrellel for an 8 ohm cabinet with 30 wats of speakers
2)wire the 2 4 ohms in series for another 8 ohm cabinet with 40 watts of speaker"
What Jim says...not that you have much option with the speakers in question. I have found that for harp, parallel speakers with the lowest matched OT load gives best efficiency before feedback (more current over voltage supplied to the speakers) but that was with using the same speakers in different examples...as your pairs of speakers are different, you are better off just sucking & seeing & going with what your ears tell you.
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Tuckster
654 posts
Jul 12, 2010
6:01 AM
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5F6H- So you're saying I should leave my 4X10 @ 2 ohms (yes,the amp has a 2 ohm tap),rather than rewire it 8 ohm? It will sound best pushing more current? Things get warm,but I haven't blown anything up yet. Have blown a fuse occasionally,but always found half a triode had gone bad,too.
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5F6H
240 posts
Jul 12, 2010
6:48 AM
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Tuckster - yes, that would be my preference. If loads are matched then nothing in the circuitry should be getting any hotter than it would with the speakers wired either way, the extra current pushing the speakers is ony apparent at the OT secondary/speaker wires.
Power tube plate current will be the biggest cause of heat in the chassis & can sometimes prematurely blow fuses if set too high. Fuses sometimes blow if you throw the standby too quickly (like instantly) after throwing the power switch...or if you leave the amp in standby for very long periods of time prior to putting into play mode (like >tens of minutes).
With a 6L6 amp, 30 seconds to a minute is typically good from power up to play mode, 6550/KT88/KT90 might need 3 or 4 minutes to warm up before throwing the standby to play.
...assuming no shorts in the power tubes, bloown screen grid resistors, or blown rectifier that is - It's always a good idea to pull out the rectifier tube & power tube(s) after a fuse blows, replace fuse & rectifier & power up, if OK power down fit power tubes (one by one in a fixed bias amp, or all at the same time in a cathode biased amp) just to eliminate the rectifier or power tubes as the cause of the fuse blowing in the first place.
Last Edited by on Jul 12, 2010 6:49 AM
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Greg Heumann
655 posts
Jul 12, 2010
4:45 PM
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NOD, You're making me crazy!!!
"i wired 2 x 8 inch speakers in Series
1 x 16ohms 1 x 4ohms this = 16ohms
them i did the same but
i wired 2 x 8 inch speakers in Series
1 x 16ohms 1 x 8ohms this = 19ohms"
OK, first you wired them in series, then you wired them in series. I have no idea what you're talking about. But I can tell you that 16+4 = 20 and 16+8 = 24. When you're doing impedance calcs, use the speaker's rating, NOT any actual measurement with an ohm meter.
Impedance is related to, but not the same as resistance. It is resistance to an A/C signal, which in something like a speaker changes with the frequency and power of the signal going in. Measuring impedance properly requires a more sophisticated instrument called an impedance bridge.
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/Greg
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N.O.D.
28 posts
Jul 12, 2010
11:41 PM
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NOD, You're making me crazy!!!
Me to Bro:)
i did this hands on not in my head i used a normal Multi meter,
what im saying is i have to sets,or Pair of 8 inch speakers,
one pair is 16 ohms.
the other pair is 8 ohms.
Im now aware what parallel wireing and Series wiring is i wired these speakers in SERIES,,
i split the Pair of speakers one 16 ohms speaker and one 8 ohms speaker,
i wired these speakers in series
1 x 16ohms + 1 x 8ohms the multi meter reading = 19ohms
then i did the same test
takeing one 16ohms and one 4ohms speaker
wireing them in series again
1 x 16ohms + 1 x 4ohms this = 16ohms,on my multi meter
With the info i have so far Bro it seems wireing Speakers in series is no good for harp amps this tends to produce more Gain or Feedback
Wireing Speakers in Parallel is the way to go for Harp amps from what i read on the net and the info provided in this thread:)
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Good Onya Bro's!!!
Last Edited by on Jul 12, 2010 11:45 PM
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5F6H
242 posts
Jul 13, 2010
1:36 AM
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NOD I wouldn't mix the speaker impedances in the same array (e.g. 1x 16ohm & 1x 8ohm) one speaker will end up doing much more work than the other, irrespective of series or parallel.
A speaker's dc resistace as measured with a ohmmeter is always less than its rated impedance, an 8ohm speaker might read as low as 5.5ohms for instance. Impedance is determined with an AC signal and is a nominal rating (it actually varies with frequency/Hz) - as Greg states.
Parallel (2x16ohms for 8ohms total) would be my preference...ONLY as long as the 16ohm speaker sound better than the 8ohm speakers. As they are different brands/models the only way to know this is to test by ear.
Last Edited by on Jul 13, 2010 1:37 AM
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