connecting speaker wire output from pro monitor to mixer

Discussion in 'Hi-Fi Stereo Systems & Separates' started by jimmyhutch, Mar 4, 2013.

  1. jimmyhutch

    jimmyhutch
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    hello, i have an edit room in which i am trying to take audio out of a panasonic TH-50BT300 (pro plasma monitor) into my mixing board. it only has speaker wire outputs (weird), so i have a cable that goes from speaker wire to rca then rca to 1/4". when i plug into the mixing board, the monitor forces itself off, like its shorting out. i don't know much about wiring, but i am very confused by this. anyone have any knowledge on the subject? thanks.
     
  2. BlueWizard

    BlueWizard
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    Speaker Wire Outputs, you can't be serious, at TV with no speakers and speaker wire connections. Not impossible but extremely unlikely.

    Actually, I just checked the product Brochure at this location -

    http://www.tnpbroadcast.co.uk/upload/documents/3349_TH-50BT300ER.pdf

    It seems it does have a single Mono set of speaker terminals set to drive 6 ohms speakers.

    I think we are going to need a little better explanation of what you have and what you are trying to accomplish?

    Is this for movie watching? Is it for business video presentations?

    The problem is that the volume levels from a speaker terminal are very high. The speaker terminals could be used to feed an external Pre-Amp (maybe), if the monitor has a volume control on it to control the output.

    Typically Line Level runs from a faction of a volt to perhaps 2 volts peak. The maximum output of most Audio Amp, even those with modest power can be as much as 10 volt. The Monitor claims an output of 8 watts per channel, even though it seems to have only one channel out. Though I confess the diagrams on the PDF file in the link are not very clear. Eight Watts continuous means a potential of ±10 volts or 20 volts peak to peak. That is substantial more voltage than standard Line Level.

    Next music is dynamic, modest average levels and still result in very high peak levels. To illustrate, even at relatively loud levels, most Stereo amp are only averaging about 1 watt, yet peaks in the music are jumping up very near the voltage limits of the amp.

    So, if you can control the voltage output of the Monitor, and if you can keep it down within the range of standard Line Levels, then you can probably connect the speaker out to the Line In. However, there is an element of danger should the input levels get excessively high.

    Which is why it is important to know all the related equipment you have and specifically what it is you are trying to accomplish. But 'trying to accomplish' I mean how is this system going to be used. What is the purpose and to what end do you need to make this connection? Perhaps there is an alternate method of getting the sound to the Mixer.

    While I offer no guarantees, it is likely that this can be made to work. Though the specifics will need a little more thought.

    Steve/bluewizard
     
  3. formbypc

    formbypc
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    Do you have the instruction manual for the monitor?

    If so, read page 4 under the heading - Warning

    "This Plasma Display is for use only with the following optional accessories. Use with any other type of optional accessories may cause instability which could result in the possibility of injury. (All of the following accessories are manufactured by Panasonic Corporation.)

    Speakers TY-SP42P8W-K (for TH-42BT300ER),
    TY-SP50P8W-K (for TH-50BT300ER)"


    Page 10 on Connections contains nothing to suggest the speaker outputs can be connected to a line-level device such as a mixing desk. Lastly,


    You MUST be feeding the audio TO the monitor from a line-level source. The monitor isn't a source component.

    Why aren't you feeding the audio from this source to the mixer? And, as Bluewizard says, what are trying to achieve?
     
  4. jimmyhutch

    jimmyhutch
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    thanks for your responses BlueWizard and formbypc,

    i'm using the monitor and mixer in an edit suite. i have 3 other suites in which the editor's console (which faces the client area) has its own video monitor and set of near field audio monitors being fed by the mixing board. in the other suites i have 50" elite monitors for client review. in these rooms, i am able to run line out from the elite (which is fed HDMI by a blackmagic i/o card). this way, if there are clients in the room, they can listen to audio coming from the elite, and the editor's near field monitors (genelec) will be in sync with the elite audio, without any annoying phasing.the editor's mixing board is also fed directly by the blackmagic card, but because the plasmas (elites as well as TH-50BT300) have a bit of latency, if i set up another set of monitors under the TH-50BT300 and feed them from the board which is getting audio from the blackmagic card, the client monitor will forever be 1-2 frames out of sync. if, on the other hand, i install a soundbar or add speakers to the TH-50BT300, it will be forever out of phase with the editor's genelecs.

    bottom line, i never should have bought the TH-50BT300. i got it because this new edit suite also doubles as a color correction suite and you cant find elite plasmas anymore, and i didn't imagine it wouldn't have line out. i know nothing about amps, ohms and volts, so ignorantly thought i could use the signal coming from the speaker terminals (it actually has stereo speaker terminals) once i discovered the TH-50BT300's shortcomings. its paid for and mounted, so unless i can figure out a way to "control the voltage output", i guess i'm toast.
     
  5. BlueWizard

    BlueWizard
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    I'm still a little confused. When you say Editing suite, can we assume you mean a video editing suit which one assume exist inside a computer? Yes or No?

    Can we further assume that the blackmagic i/o card is just that, an I/O card and not a Sound Card?

    Typically monitor/TVs allow a slight adjustment of Latency should sound and audio get out of sync.

    Can we assume the source of sound is the assumed computer you are using for editing, and does it not have its own Audio Out?

    One possibility would be to add a Impedance Corrected Voltage Divider between the Monitor Audio Outs and the Mixer Input. I would make it about 600 ohms. That is higher than the output of the Monitor, but lower than the input of the of the mixer.

    Scroll down to the bottom of the page in this link -

    Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)

    You will see an L-Pad calculator, all you have to do is figure out how much attenuation you need to get the output of the TV down to something approximating line level.

    For example, if we assume 600 ohms and an attenuation of 12dB, the the values you need are -

    R1 = 449 ohms
    R2 = 201 ohms

    ...you would use the nearest standard values.

    I use 600 ohms because that is something of a standard value. You could do something similar with something in the roughly 8 to 16 ohms range. If for the moment we assume we need 12dB of attenuation, and we want it impedance stable at 8 ohms, the values we would use would be -

    R1 = 6 ohms
    R2 = 2.7 ohms

    However, I can't be sure about the output amps in the Monitor, and can't say how stable they would be when driving a 600 ohm load.

    If we look at this as a Voltage Divider, then the outgoing signal is a ratio of 2.7/8.7 of the incoming signal. For example if the input is 10 volts then (2.7/8.7 = .31) or 10v x .31 = 3.1 volts. If you drop the input down to 5 volts, then the output is going to be about 1.6 volts. Keeping in mind the absolute limit is rough 2 volts. You should be able to determine this from the specifications of our Mixer.

    There are also inline attenuators available. I know for sure these are available in the UK, but for quick reference I'm using a USA site -

    http://www.parts-express.com/pe/showdetl.cfm?partnumber=266-244

    http://www.parts-express.com/pe/showdetl.cfm?partnumber=240-412

    These are Impedance Matched, if at all, to the destination impedance which is high. That represent a high impedance to the Source Amp (the Monitor). The accuracy is going to be based on the Impedance of the Destination input. Most Stereo amps have 47k ohms input impedance, some PA mixers have 10k ohm impedance. That doesn't throw it completely off, it will just a few dB change in the actual attenuation.

    The alternative would be to use some type of Step-Down transformer that would present an acceptable load to the amp, and attenuate the Signal down to Line Level.

    However, I'm not sure why you don't drive sound in each location with the assumed Editing computer you are using. To what extent does the Monitor have the ability to adjust for latency?

    Steve/bluewizard
     
    Last edited: Mar 5, 2013
  6. BlueWizard

    BlueWizard
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    Actually, I think I may have found the solution. Search Google-UK Shopping for Speaker Level to Line Level Converter or Speaker Level to Line Level Adapter.

    That should give you several low cost solutions -

    [ame=http://www.google.co.uk/search?hl=en&tbm=shop&q=speaker+level+to+line+level+converter&oq=speaker+level+to+line+level+converter&gs_l=products-cc.12..0.2930.2930.0.4116.1.1.0.0.0.0.61.61.1.1.0...0.0...1ac.2.khh_wXXC44Y]speaker level to line level converter - Google Search[/ame]


    Apparently it is a more common problem than I thought.

    I'm guessing these are used in Automotive applications where you want to feed external Power Amps with the output of a Car Stereo amp.

    Steve/bluewizard
     
    Last edited: Mar 5, 2013

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