PA powered desk speaker ohm mismatch

Discussion in 'Recording/Live Sound' started by effectsman, Feb 16, 2012.

  1. effectsman

    effectsman Supporting Member

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    We have a an old powered desk which we use for our PA and we want to run some passive wedges as monitors. Trouble is the desk we use has 6 ohm outputs which is really odd and unusual ohmage.

    Can you run 8 ohm speakers from this desk safely? This is the safer direction to go right with the speaker having a higher ohmage than the desk?

    Or do you go lower ohmage speaker say 4 ohms? But this may draw more power from the desk and make it overheat right?
     
  2. GCDEF

    GCDEF Supporting Member

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    Assuming it's a solid state amp, the 6 ohms would be a minimum impedance, not a recommended one, so 8 ohm speakers would be fine.
     
  3. rokpunk

    rokpunk Member

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    you want to power your mains as well as your monitors with this powered console? what make/model mixer/amp is it?
     
  4. effectsman

    effectsman Supporting Member

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    Thanks for the reply. Yes it is solid state.
     
  5. effectsman

    effectsman Supporting Member

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    Yes. It has 8 channels and currently we run the electronic drum kit and the vocals through it. The guitars (2) and bass just run through their amps. We would like to run everything through the PA however we don't have enough channels, and at the moment on our limited budget we really feel that we need some FOH monitors so we can hear ourselves better.Buying a new desk is on our list to do, but we need more paying gigs before we make this investment.



    It is an old (late 1970's) Mackie that was an ex-high school PA system. I don't know the exact model etc as the drummer looks after the system. I could find out within 24 hours and post back if you feel it's worth knowing before making a recommendation.
     
  6. rokpunk

    rokpunk Member

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    are you sure it's that old? mackie didn't switch names from tapco to mackie until the late '80's and then became popular in the early '90's with their 16xx series. in any case, my suggestion would be to add a 2 channel amp to your system if you are going to add 2 wedges. the less power you have to pull from the powered mixer, the better. powered mixers, in general, don't mix or amplify very well. the less you have to rely on them, the better off you are (imnsfho). is you mixer a box head type mixer/amp, or is it like a traditional mixer with faders?
     
  7. effectsman

    effectsman Supporting Member

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    It's a traditional mixer type with faders. And your right about the branding. It doesn't have a Mackie label on it but the last time we had it to a tech he said they were made by Mackie so that might be what he meant.
     
  8. rokpunk

    rokpunk Member

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    if i had to guess, i'd say it's an old tapco mixer/amp. don't overdrive it unless you want some ugly sounding distortion. maybe find yourselves some used powered monitors so that the mixer/amp is doing any more work than it has to.
     
  9. effectsman

    effectsman Supporting Member

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    Spoke to our drummer and got more details, and your right. It's an old Tapco 100W per side powered desk. However we don't use the amp in the desk. He runs out of the desk into a Yamaha 400W per side amplifier and then to two FOH speakers

    What he was thinking we would do is run a cable out of the Tapco into another amp we have which is a Fostex 300W side at 6 ohms amp. So this is the one we are trying to buy speakers for.
     
  10. mixwiz

    mixwiz Member

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    I didn't know fostex made power amps. Here are the specs I think: http://www.fostexinternational.com/docs/downloads/pdfs/a300-a600_owners_manual.pdf

    Looks like it's from the late 70's. Makes decent power and should run down to 4 ohms so you could even run two 8 ohm boxes per channel.

    As for the Tapco, I know you're on a budget but you should think about a different mixer. Though they aren't the worlds finest, even a used B*&$#inger 12 channel euro desk would be a substantial upgrade. You can usually find one one the bay for around $100. More channels, basic effects, a couple auxes (you could run two monitor mixes if you like) and some basic grouping buses.

    Just a thought, Hope this helps.
     
  11. effectsman

    effectsman Supporting Member

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    Thanks for the info. We've certainly talked about upgrading the PA, but most PA desks are passive now with powered speakers, and our drummer who owns the PA is keen not to have to replace the passive speakers he already has.

    But for sure it is something we will have to tackle, and I appreciate your recommendation.
     
  12. mixwiz

    mixwiz Member

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    Tucky, I think you're missing some fundamental stuff here. While the Tapco is powered, you are using it in a traditional way. Line out to power amp to speaker. Higher quality mixers have always been non-powered. The desk of the day in the era your tapco was made was probably the Kelsey pro series.

    You could upgrade your board, use one amp for mains and the other for monitors and your drummer gets to keep his passive tops.

    Not trying to sound snarky, just trying to help.
     
  13. effectsman

    effectsman Supporting Member

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    It's all good, and I appreciate your help. To elaborate a bit it's not just that the drummer wants only to keep the speakers he's got, it's that we all are trying to spend as little money as possible while trying to best utilise the current components we have. That approach may be false economy in the long run I know.

    So...we are figuring for a few hundred dollars we can get some monitors which will allow us to bring the FOH speakers forward to the front. Currently we run them at the back of the stage so they give the drummer fold back, but it interferes with the mikes badly sometimes.

    We've looked at replacement desks and they are around $500-900 here. So we figure we'll start with some monitors and see if we can still manage to get by with the rest of the PA as it currently is.

    We are only currently gigging 6-8 times a year at parties, so we are trying to build as we get more work.
     

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