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Topic: Amp to speakers ? Matching Ohms ?? |
Eddie Cunningham
From:
Massachusetts, USA
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Posted 23 Oct 2007 9:52 am |
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| Tech. Questions = Can you run a 4 ohm speaker off an amp 8 ohm mono output ?? And can you run an 8 ohm spkr. off a 4 ohm output ?? And on a stereo amp double 4 ohm outputs can you mismatch 4 ohm and 8 ohm spkrs ?? = without blowing spkrs. and/or power amp ?? I generally play at moderate loudness levels . Would appreciate any help and info !! Thanks !! Eddie "C" |
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John McGuire
From:
Swansea,Illinois, USA
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Posted 23 Oct 2007 11:04 am
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| I hope I get this right. 2 8 ohm speakers connected together "Daisy Chained" would equal a 4 ohm load. take the ohm per speaker and divide. 2 8 ohm equal 4 ohm, 2 4ohm equal 2 ohm. etc. You should avoid connecting speakers of different ohms because of strange impendeiance sp? problems. I am sure someone will correct me and add to this. It depends on what your amp output is rated at so many watts at so many ohms. The bottom line is yes you can damage your componets by mis- matching |
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Eddie Cunningham
From:
Massachusetts, USA
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Posted 23 Oct 2007 11:29 am Amp rated =
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| The amp is rated at 4 ohms at 75 watts each channel stereo and mono = 150 watts at 8 ohms !!! Hope this helps !! ?? Eddie "C" |
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Jack Stoner
From:
Kansas City, MO
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Posted 23 Oct 2007 12:26 pm
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"2 8 ohm speakers connected together "Daisy Chained" would equal a 4 ohm load"
If by "daisy chained" you mean connected in Series that is incorrect. Speakers in series add (e.g. two 4 ohm speakers connected in series would equal 8 ohms).
Speakers connected in Parallel will have a lower ohmage than one speaker. If the two speakers are equal, e.g. 8 ohms each then the total load would be 4 ohms. On the other hand if one was 16 ohms and the other 8 ohms the load would be approximately 5.33 ohms. |
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Larry Scott
From:
Virginia, USA
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Posted 23 Oct 2007 1:38 pm
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| Jack Stoner wrote: |
"2 8 ohm speakers connected together "Daisy Chained" would equal a 4 ohm load"
If by "daisy chained" you mean connected in Series that is incorrect. Speakers in series add (e.g. two 4 ohm speakers connected in series would equal 8 ohms).
Speakers connected in Parallel will have a lower ohmage than one speaker. If the two speakers are equal, e.g. 8 ohms each then the total load would be 4 ohms. On the other hand if one was 16 ohms and the other 8 ohms the load would be approximately 5.33 ohms. |
You are correct Mr.Stoner
Basic Electricity
http://www.asisvcs.com/publications/pdf/710041.pdf |
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Eddie Cunningham
From:
Massachusetts, USA
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Posted 23 Oct 2007 4:29 pm Only one spkr. used per output
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| I am not using "daisy chain" , only one speaker per output jack. My question is , can I drive an 8 ohm spkr. with 4 ohms output and can I drive a 4 ohm spkr. with 8 ohms output power ?? and on the stereo output can I use a 4 ohm spkr. on one side and an 8 ohm spkr. on the other side ?? The amp output is 8 ohms mono and 4 ohms each side stereo. Thanks for the input !! Eddie "C" |
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 23 Oct 2007 6:01 pm
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Eddie, we can't give specific answers for generalized questions. We need to know what kind of amp you're using, the reason being that the "rules" for solid-state and tube amps are different, and also, some amps (like the old tube Fenders) were designed for a mismatch.
In addition, "loudness levels" are often meaningless. Screaming treble requires very little actual power, and monster bass requires gobs of it. It helps if we know what kind of programming you're intending to push through the amp/speakers. |
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Eddie Cunningham
From:
Massachusetts, USA
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Posted 23 Oct 2007 7:41 pm Solid State amp
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| It's a new Crate solid state P.B. 150 power amp !! I play a Fender 1000 steel at average sound levels !! Hope this helps !! Thanks !! Eddie "C" |
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Jack Stoner
From:
Kansas City, MO
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Posted 24 Oct 2007 2:30 am
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I have one of those Crate amps.
I've run two 8 ohm speakers off of the rated 4 ohm outputs without problems. Just slightly less than the rated 75 watts per channel. In fact I used that setup with a POD XT as the preamp/effects and the Crate as the power amp into the two Peavey 8 ohm BW speakers New Years eve. Worked well for both steel and my Telecaster and I had plenty of volume. |
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Eddie Cunningham
From:
Massachusetts, USA
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Posted 24 Oct 2007 6:47 am Thanks for the input !!
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| Thanks, guys , for all the input and info !! I think I will be safe doing what I had planned. Looks like no big problems !! Maybe a slight loss of power !! > = No big deal !! Thanks !!! Eddie "C" ( the old geezer ) |
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Don Brown, Sr.
From:
New Jersey
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Posted 29 Oct 2007 1:37 pm
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Eddie, the only thing is, a tube amp is much more forgiving than a solid state divice on mismatch.
The impedance is the match between your amp's (final output transistors) and the speaker/s. Without the proper load the transistors will heat up, much more than with a normal load, which will eventually, take them out.
Just as in turning on a high power stereo and not having the speakers hooked up to it. Bingo. No final output.
You may well get away with it for a while, but it's not a good practice.
Hope that helps. |
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Dave Mudgett
From:
Central Pennsylvania and Gallatin, Tennessee
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Posted 29 Oct 2007 2:56 pm
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On a solid-state amp, you can generally run a speaker with higher impedance than the nominal impedance as stated on the amp, but not lower.
For example - if your power amp says "use 4 ohm load", running 8 ohms is not a problem, although you do lose some power. Most solid-state amps transfer maximum power when the load is the minimum allowed. But there is no inherent problem running such amps with a higher impedance load - in fact, the current will be lower and it generally is actually easier on the power transistors.
But - and this is a warning I would heed - if, for example, your power amp says "use 8 ohm load", you should not run it with a 4 ohm load. The problem is that the current increases, and you can indeed run the risk of frying your output transistors. So - on this question:
| Quote: |
| Can you run a 4 ohm speaker off an amp 8 ohm mono output ?? |
I would say emphatically no, unless the manufacturer tells you that it's OK to run with a load less than the rated impedance.
Many solid-state amps state "Minimum load: X ohms", where X is 2, 4, 8, or whatever. Any solid-state amp like this has a lower-limit, and this is probably the best way to communicate this idea.
Tube amps - and really, any amp that uses an output transformer to couple the output section to the load - are completely different. IMO, it's best to give the amp the correct load. The caveat there is that some amps - e.g., old Fenders - can often tolerate some, but not a lot of mismatch. But others can't. IMO - and this is just my opinion - you should know what you're dealing with before you mismatch the load on any tube amp. Either way - maximum power transfer is achieved when the load impedance matches the output section impedance as closely as possible in this case. |
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Jim Sliff
From:
Lawndale California, USA
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Posted 29 Oct 2007 3:35 pm
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Consult the manufacturer.
Jack has done it successfully, but it may be the particular speakers he uses, or something else in his setup. Don't take a chance. BF/SF Fenders are the only amps I know of that are normally capable of a 100% mismatch...and even that will result in tonal compromises and a loss of output power (no matter if you go higher OR lower, you will lose power).
_________________
No chops, but great tone
1930's/40's Rickenbacher/Rickenbacker 6&8 string lap steels
1921 Weissenborn Style 2; Hilo&Schireson hollownecks
Appalachian, Regal & Dobro squarenecks
1959 Fender 400 9+2 B6;1960's Fender 800 3+3+2; 1948 Fender Dual-8 Professional |
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