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  1. #1
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    Replacing TV speakers

    I just bought a new TV that has two small oval 10 watt 8 ohm speakers. It uses a intergrated amp ic TDA8932t rated at 2x15 watts.In the data sheet for this chip it mentions if proper cooling via the printed circuit board is implemented continuous 2x15 watts is feasable. WHAT DOES THAT MEAN? Add some type of cooling media onto the chip?

    I want to connect two Klipsch 2.1 promedia satelite speakers rated at 8 ohms 35 watts and remove the existing factory speakers. I measured the actual resistance in the Klipsch speakers with the crosover circuitry etc and get like 6.5 ohms.

    I don't plan on blasting the TV loud i just can't deal with the terrible sound from these small speakers.

    Any advice or experience would be greatly appreciated. TY

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    dont get hung up on the wattage, you will never use the max in continuous, only for short blasts.

    Kinda sounds like you may need a simple receiver and using the TV out to Input on receiver.

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    Oh i have that setup, but i want to be able to juast listen to the tv sometimes normally.

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    then what is wrong with using the tv speakers for that?

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    The sound that comes out of those speakers is horrible! The speaker are installed so they point straight down, sounds like the tv is in a can. Also one speaker is installed properly the other is installed reverse phase......they do this to stop the ic amp from "PUMPING EFFECT" what ever that means. That has to effect the quality of the sound.

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    What television is this, and where did you dig up all this tech info?

    Does it have external speaker outputs?

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    3LB
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    With all your info and ability to source technical data, what is it you need from one of us?

    for one thing, that 6.5 ohm (DC rating) is typical of a speaker with 8ohm impedence

    does the technical data say whether that chip is stereo or mono? phase inversion would accout for a lack of bass and that canned effect you mention, if we're talkin stereo that is.

    Do a cost benefit analysis - whats the worst that could happen if you "correct" the phase issue? whats the worst that could happen if you hook 8ohm speakers through that chip? if you blow the chip, do you consider it a loss?
    Repost this on your wall if you love Jesus.

  8. #8
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    Thumbs up

    Quote Originally Posted by Barb1
    The sound that comes out of those speakers is horrible! The speaker are installed so they point straight down, sounds like the tv is in a can. Also one speaker is installed properly the other is installed reverse phase......they do this to stop the ic amp from "PUMPING EFFECT" what ever that means. That has to effect the quality of the sound.
    Theres a reason for that.
    nobody with a decent TV will waste it with the crap speakers that come with the set.
    The speaker setup on my TV is actually not bad, but most are lousey, intended for
    casual use only.
    Get a decent set of computer speakers and plug them into the ext speaker plug,
    dont waste your time with the onboard amp.
    Phillips makes a great sat/sub system for fifty bucks, I use it at work, and am always getting complimented on it, plays pretty loud, too.
    Got it at Walmart.
    Bose makes a series called MEDIA-MATE if you want to go upscale a bit.
    Compact and sound really great, Bose sucks, but they know compact speaker systems.
    Replacing the onboard speakers is a waste of time, and will void whatever warranty
    you have, and I CAN GUAREENTEE YA that that chip amp wont last as long as a fruit fly.
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  9. #9
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    Why a speaker system is wired "out of phase" beats the hell out of me. I also believe that the sound (like mentioned in a previous post) would not be centered between the two speakers and could be a very contributing factor to the sound quality. If possible and you are sure of that phasey thingy, I would if possbile reverse one of the connections on that speaker system and listen to what you get. Dialogue should come from the center of the speakers from a mono source.

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    Yes i pulled the sound board, the right speaker is out of phase as the schematic clearly shows. For now i'm using the audio out jacks to a Technics SA-EX510 and some older bose 500 series speakers. I found what i think is the big problem with the onboard audio, TOO much noise in the sound. I compared it to another tv and for some reason this new tv has much more distortion in the onboard sound circuit. The sound through the external jacks sounds much cleaner. If i toggle the onboard and external sound you can hear the distortion even at low sound levels with the onboard.

    I'll need to pick up a good set of used speakers for the 510. Any suggestions? Thanks for all the replies.

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    Quote Originally Posted by 3LB
    With all your info and ability to source technical data, what is it you need from one of us?

    for one thing, that 6.5 ohm (DC rating) is typical of a speaker with 8ohm impedence

    does the technical data say whether that chip is stereo or mono? phase inversion would accout for a lack of bass and that canned effect you mention, if we're talkin stereo that is.

    Do a cost benefit analysis - whats the worst that could happen if you "correct" the phase issue? whats the worst that could happen if you hook 8ohm speakers through that chip? if you blow the chip, do you consider it a loss?
    LOL not really...just don't want to take it out completely. I'm not a audio tech and am asking for your experience. I'm smart but not experienced in audio circuits. TY

    ps anyone into tv circuits? I want to power some dc fans to cool the power supply board so it lives for longer than the one year warranty.
    Last edited by Barb1; 05-15-2010 at 02:29 AM.

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    If there is a warranty on this set, you might be better off using that warranty to call in a tech to check this board out. They might replace it. Make sure that when you put back everything together that it looks like nothing has been fooled with.

    As far as external speakers go for your Technics, you need to figure first what size woofer you want and that speaker system that you will end up choosing should be shielded. I looked at this receiver on Google Images and could not determine if it was a Dolby Digital or only a Dolby Pro-Logic receiver though you certainly could use this receiver in stereo.

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    Parts Express to the rescue.

  14. #14
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    Cool

    Quote Originally Posted by Barb1
    LOL not really...just don't want to take it out completely. I'm not a audio tech and am asking for your experience. I'm smart but not experienced in audio circuits. TY

    ps anyone into tv circuits? I want to power some dc fans to cool the power supply board so it lives for longer than the one year warranty.
    Lordy, please dont try to second guess the engineers that built this thing.
    That power supply will probably outlive you, only way heat will kill it is if your house burns down.
    I have seen 30,000 volt power supplies in ten year old sets still going strong, its not a
    difficult tech.
    As for the speakers being "out of phase", might have something to do with their close proximity to each other, so that a lot of sound wont disapear or become mono,
    but that is just a guess.
    If you have already taken the back off, congrats, you have a very bulky paperweight
    if something breaks, so be very carefull concerning what you mess with,
    because you have no warrenty if they find out.
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  15. #15
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    NO Sir, if the TV is under warranty one should not as much as wave a screwdriver at the damned thing for fear of losing warranty rights, and that is regardless of having an electronic background. Unless you got it over the internet or canīt return the TV, what you did must be a last resort solution.
    The speakers that come with the TV are usually suffer able, leaving us the choice of hooking up the AV receiver or a Home Cinema system. Not wishing to connect up to the aforementioned really leaves you with using the headphones jack out to connect up to a set of computer speakers with a sub unit.....

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    Ok here goes.........1st of all there was CONSTANT noise in the audio out pre amp circuit. 2nd constant noise in the amp out circuit .

    I phased the speakers properly and now the noise is gone....audio is clean and quiet!

    Sorry for bothing you all.................

    won't happen again!

    I was hoping there was a another PE that would give me some valid reason that i can't find for the one speaker PURPOSELY put out of phase to STOP PUMPING EFFECT
    The sound is excellent now.

    I solved my problem but i still want an explaination.

    If you're not a PE don't bother posting up..i don't need criticism. I'm a engineer but not in this field.
    Last edited by Barb1; 05-17-2010 at 07:57 PM.

  17. #17
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    Quote Originally Posted by Barb1
    If you're not a PE don't bother posting up..i don't need criticism. I'm a engineer but not in this field.
    Well, if that ain't an arrogant statement...........

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    Cool

    Quote Originally Posted by Barb1
    Ok here goes.........1st of all there was CONSTANT noise in the audio out pre amp circuit. 2nd constant noise in the amp out circuit .

    I phased the speakers properly and now the noise is gone....audio is clean and quiet!

    Sorry for bothing you all.................

    won't happen again!

    I was hoping there was a another PE that would give me some valid reason that i can't find for the one speaker PURPOSELY put out of phase to STOP PUMPING EFFECT
    The sound is excellent now.

    I solved my problem but i still want an explaination.

    If you're not a PE don't bother posting up..i don't need criticism. I'm a engineer but not in this field.
    Its called a mistake.

    Kinda funny that a TV with that problem would go to the one outta a thousand customer
    who would prefer to torture their ears with OEM speakers.
    I miss when you could just buy a monitor and not have to pay for cheapjack amps and chintzy speakers from a clock radio that you will never use.
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  19. #19
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    The noise was on the line out also....so using an external sound source just amplified the noise.

    Going way beyond your undterstanding I contacted a friend of mine who does electrical engineering work and got info i needed. The ACTUAL problem was the wiring for the speakers was NOT shielded in any way. It was inducing electrical noise into the sound board. After using a twisted pair to supply the speakers power all the noise was gone and i was able to use the reverse phasing as called out on the ic engineering sheet.

  20. #20
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    Hello.
    Well, here, one gets advice as well as criticism, the constructive type.....
    And, I do admire the time and effort you expended to solve a problem, but the majority of people would return the product without tampering with it purely for warranty reasons( myself included). Good for you, and do lighten up, all that about brandishing a screwdriver was meant to be taken lightheartedly.

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    Section 14.8, Figure 12 of the datasheet. TDA8932T IC which is a class-D amp proposes the inverted phase connection of the second speaker to minimize the pumping effect, so the problem as you went on to explain was caused by the absence of shielding. Am I with you now?

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    Oh, by the way, the 2nd speaker is meant to be connected out of phase, the reason is that its signal is inverted before being presented to the input of the amp!!! So at the output end everything is back IN phase and the pumping effect is minimized (provided the speaker IS wired out of phase). This is one of the solutions provided by the 3rd site below. Prone to cause EMI ( Electromagnetic Interference) courtesy of the first site.
    For more detailed electronic explanations:
    http://www.irf.com/product-info/audi...sdtutorial.pdf ( Slide show )

    sound.westhost.com/articles/pwm.htm ( Theory and design Class-D amp Sergio Sanchez Moreno)

    www.maxim-ic.com/app-notes/index.mvp/id/4260 ( Pumping explained and solutions Marshall Chiu)

    The reading gets heavier from top to bottom. For the fainthearted but eager to know what pumping is, I will try to present an amusing analogy of this phenomena over the weekend.

  23. #23
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    Perhaps I should start with amplifier clipping, which should be a familiar subject and then go on to PUMPING. I will use half a bottle of wine, which is my limit, to depict the positive half of the amplifier power supply ( PS from now on ).
    So after a couple of small glasses of wine, I am my jovial self and so is the power supply since it has not been called on to deliver more than itīs limit. Whatever little that is still left in the bottle ( and the PS ) is the headroom at this stage. If one turns on the volume a bit more, like me emptying the bottle, the PS runs out of juice and clipping happens, sounding a bit like me shouting at everybody : " Who finished my wine ? " NOT a pretty audio-visual sight!!
    Pumping of the PS happens in Class-D amplifiers where current flows from the PS to the load ( like from the wine bottle to the glass ), but unlike Class-A and B, the current also flows back from the load to the PS effectively raising its Voltage!! Suddenly, my half a bottle is made more full and being the sucker I am, I will attempt to drink it resulting in a hangover!! I will be OK next morning, but the extra voltage of the PS can irreversibly damage the electronic components. Pumping is more prominent at the low audio frequencies, and there are ways to minimize this. Since these low audio frequencies are present in almost equal levels in both Left and Right channels, the 2nd input to amp is inverted, thereby reducing the excess voltages on the positive and negative PS. Finally to get the audio signal back in phase, the 2nd speaker also has to be connected up INVERSELY!!!

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