Can this forum stand yet another receiver shut-off question? (long post)

Discussion in 'Archived Threads 2001-2004' started by Angel Pagan, Aug 18, 2002.

  1. Angel Pagan

    Angel Pagan Second Unit

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    ***I really couldn't decide where to post this since it involves both a receiver and speakers.***
    I’ve also posted this on the AVS Forum because I’m really scratching my head over this. I’ve done searches on both forums and have come across answers to some questions. Let me start off by saying that I have a Pioneer 26TX receiver. I recently upgraded from Bose Acoustimass 5 speakers (they’re about 5 years old so they were probably Series 1) to Definitive Technology ProMonitor 80 speakers.
    With the Bose speakers, I was able to play movies loud without any problems. Movies always sounded well especially after I replaced the Bose bass module with a Definitive Technology ProSub 80. But now, I’m having the same problem others have had with their receiver shutting down during high volume/heavy bass scenes. I can only go as high as -15 db when using a DTS track (-10 with DD).
    Upon searching both forums, here’s what I came up with:
    1-check speaker wires for short
    I was using Monster flat speaker wires with the Bose (bare because of the spring clips) and initially used them when I purchased the Def Techs. When the problem first started, I switched to Home Depot 12 gauge speaker wire attached to Radio Shack Gold Series banana plugs (duals on the ProMonitors, singles on the receiver). Problem still occured so I don’t think it’s the wire.
    2-make sure there is enough ventilation around receiver
    I have my gear on a Standesign open-air rack. My receiver is on the top shelf and there is nothing sitting on top. That being said, my receiver runs hot and coupled with the fact that I don’t have a/c in my living room and it’s been an unbelievably hot summer in NY, it’s probably running hotter than normal. But, since I’ve never had a/c in the living room and the receiver never shut off with the Bose, I doubt that’s the problem. I should get a small electrical fan for the receiver, though.
    3-low impedance loads
    Here’s one which has me totally clueless. When checking the specs on the receiver’s manual, here’s what it says: “Continuous average power output of 100 watts per channel, min., at 8 ohms, from 20 Hz to 20,000 Hz with no more than 0.09% total harmonic distortion (front).” Huh?
    The specs on the speaker’s manual read:
    Frequency Response: 60 Hz-30 kHz
    Efficiency: 89 dB
    Nominal Impedance: Compatible with 4-8 ohm outputs
    Driver Complement: A 4.5” cast basket bass-midrange driver and a 1” pure aluminum dome tweeter are perfectly blended by a complex, phase coherent Linkwitz-Riley crossover
    Recommended Associated Amplification: 10-150 watts/channel
    When I check the “Preparation” section of the manual, it states: “You can change the speaker impedance to suit the kind of speakers you have in your home system but we recommend using speakers with an impedance of 8-16 (the default setting). If you are using 6- less than 8 impedance speakers, you need to change the impedance setting. In general, use speakers with a nominal impedance between 6-16.”
    So, I’ve tried changing the receiver to 6 ohms but still have the same results.
    Now what?
    Do I get a receiver that can go down to 4 ohms? Is there such a receiver?
    or
    Do I replace my speakers? I can always go back to the Bose as fronts and keep the Def Techs as rears. I’d rather not go with the Bose because of the bare wire/spring clip aspect. Then again, there’s no assurance that the same thing won’t happen with the Def Techs as rears. [​IMG]
    I’ve read where some members have recommended an external amp. Would this solve my problem? If so, how much for an average-priced one? My budget won’t allow for an expensive receiver/amp, so I’ll have to go budget on this one if need be.
    Sorry for the rant. :b
    Thanks,
    Angel
     
  2. Angel Pagan

    Angel Pagan Second Unit

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    Anyone?
     
  3. Wayne A. Pflughaupt

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    Angel,

    There are a few missing piece to your explanation:
    • Are you trying to fill an overly-large room?
    • Are your mains set to “large?”

      • The bottom line is that you are overdriving your receiver. I don’t know about yours, but mine is a little above half-way up at the –15dB setting. For most receivers/speaker combinations, you can’t get much higher than that without the danger of driving the amp into clipping. In other words, you probably have it pretty much maxed out.

     
  4. Angel Pagan

    Angel Pagan Second Unit

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    Thanks for the reply Wayne.
    My room is roughly 16.5' x 12.5'. My mains are set to small.
    ------------------------------------------------------------------------
    But, since I’ve never had a/c in the living room and the receiver never shut off with the Bose, I doubt that’s the problem.
    ------------------------------------------------------------------------
    This would only be relevant if you could say, ”My first set of ProMonitors did not have any problems with this receiver.”
    What I meant by this was that the heat wasn't a factor in shutting the receiver down until I connected the ProMonitors but I agree with you.
    I'll be buying an electrical fan today at Radio Shack. Thankfully, the temperature has fallen and the end of summer is right around the corner. [​IMG]
    I purchased an ohm meter yesterday and will use it on the speakers today to see what the deal is.
    Thanks again
    -Angel
     
  5. ThomasL

    ThomasL Supporting Actor

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    Angel, is this only happening when watching movies? If your Pioneer has the same relative volume scale then -15db is pretty high. I have a 811S and our room is 13.5 x 12.5 and the volume never gets above -36db or so for movies. Are you listening at reference levels (i.e. 85db calibrated with Avia or VE)?
    Do you notice any distortion before it shuts down? i.e. any clipping? If it just shuts off then I would suspect heat is the problem. Is the receiver almost too hot to touch when it shuts off? If the air outside is 85-90 and the air inside your room is 85 then you're not getting any air circulation whatsoever even with the windows open so while the receiver may be open to the air, it's not getting fresh new cool air to transfer its heat to, if you know what I mean. [​IMG]
    The reason it did not do this with the Bose speakers is probably simply that they did not drive the amp as hard. This is probably due to their not handling much in the way of bass. Even with your new speakers set to S, they are probably handling mid-level bass and driving the amp a little harder.
    And yes, if this problem persists even after the room is cooled, getting a two channel amp to handle the fronts will take that load off of the receiver and should clear up the problem - assuming that the receiver has pre-outs.
    good luck,
    --tom
     
  6. Wayne A. Pflughaupt

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  7. IraSWeiss

    IraSWeiss Stunt Coordinator

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    I'm using a Pro Cinema 80 setup with a Sony STR-DB830 (also a 100/100/100/100/100 watt rated receiver) with the back panel impedance switch set for 4 Ohms and have had not shutdown problem whatsoever.
     
  8. IraSWeiss

    IraSWeiss Stunt Coordinator

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    I'm using a Pro Cinema 80 setup with a Sony STR-DB830 (also a 100/100/100/100/100 watt rated receiver) with the back panel impedance switch set for 4 Ohms and have had no shutdown problem whatsoever.
     
  9. Angel Pagan

    Angel Pagan Second Unit

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    Tom, thanks for the reply.
     
  10. Earl Simpson

    Earl Simpson Supporting Actor

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    Read my 3802 post on this subject. You may have a defective rcvr, if it does it with two speakers in stereo. Amps do not like 4 ohm loads at high volume. Also speakers will flux in ohms with the power and signal. They could easily be 2 ohms at times in the play back scenario. I guess all your speakers are perfect????[​IMG] Usually it is a speaker crossover bad/too low of an impedance )or amp problem ( defect in rcvr) when the happens.
     
  11. Earl Simpson

    Earl Simpson Supporting Actor

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    PS/ Set your meter to the lowest ohms setting on the dial and touch the leads together(if it is analog) to adjust your meter hand to 0 as in zero. Then put the probes on the speaker terminals. You should get a hand or digit advance to .2 to .6 ohms TIMES 10. This will not tell you how your speaker is working at 3/4 power and at all the audio spectrum. All speaker ohms are rated as active state , not passive (nominal). They are lower in impedance at lower frequencies except where the speaker has a resonance. My 8 ohm speakers read .5 ohms/ 5 Ohms. So, I tried the active check when I was younger and remember it was around 2-30 ohms as the power and frequency fluxed. I can't remember how to do it anymore (39 years ago).
    Speakers do produce volts as they move (back emf).
    However, I do remember that 8 ohm speakers would read lower than the actual speaker value. Also, I read in a speaker cabinet custom building book, that you can not measure true speaker impedance in the static position and that they usually read 75% of the actual value.
     
  12. Greg Haynes

    Greg Haynes Supporting Actor

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    Angel,
    Congrats on the new amp purchase [​IMG]
    I know your going to love the Parasound 855A. I purchased recently purchased the 1205A to mate with my Denon 3802 and it has done wonders.
    Getting this amp should definitely fix your issue.
     
  13. Angel Pagan

    Angel Pagan Second Unit

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  14. ThomasL

    ThomasL Supporting Actor

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    Angel, that is quite odd that it is happening in two channel stereo.
    I forgot to ask, and maybe you mentioned it but how do you have your speakers and sub set up? Are the bookshelf/satellites set to small and the sub wired via an RCA coax cable via the receiver's sub pre-out? Also, I asked about Avia simply to see if you knew relatively how loud you were listening to things [​IMG] I'd recommend picking it up so you can get an idea where you are on the volume dial. I calibrate my setup so 60db is my "reference" level which I believe means that there can be peaks going upwards to 90db. This is quite loud for us [​IMG] Another important factor to remember is the relationship between your speakers sensitivity and increased amplification. A sensitivity rating of 89db means that when fed 1 watt of power, the speakers produced sound that measured 89db from 1 meter away. Now, for every doubling of distance (I think), subtract 6db approx. and for every increase of 3db in volume, double the wattage required. So, if you're sitting 4 meters away then your speakers may produce sound at around 77db given 1 watt. To get to 98db for example, you'll need 128 watts and to push it above 100db, you'll need 256 watts. So, as you can see, if you like things loud, the watts can be consumed rather quickly especially during peak passages (this example does not take into account room effects which are going to way heavily in the actual volume level produced since some sound waves will be amplified, others attenuated by what is in the room and where you are standing in relation to it all). In addition, your receiver has to work harder if the resistance (ohm level) is lessened. The upshot of this is that more watts are consumed in order to attain the same level output. Many higher end receivers will also give power and distortion readings across the entire frequency range for lower ohm loads such as 4. So, given all of this, it is possible that during really loud passages such as the Jurassic Park demo, the receiver could simply flip it's "circuit breaker" to off when asked to supply way more power than it can handle. I did this a long time ago with an old stereo amp - turned it up way too loud and gave it a 4 ohm load and click, it just shut off. Back then, there was nothing called "protective circuitry" - they were called fuses [​IMG]. Upon opening it up, it was obvious which fuse had blown and in fact, simply taking a piece of wire and reconnecting the connection brought the receiver back to life. I didn't use it in that condition though [​IMG]
    cheers,
    --tom
     
  15. Michael R Price

    Michael R Price Screenwriter

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    I don't think the speaker impedance changes much with power. It might increase from say 5 ohms to 6 ohms when the voice coils heat up.

    I don't know how you get a reading so low. My meter reads about 3 ohms, which is good given that I know the resistance of the speaker is 2.8 ohms. You need to disconnect the cables before you measure resistance, otherwise you will be measuring the amplifier's output impedance in parallel with the speaker.
     
  16. Angel Pagan

    Angel Pagan Second Unit

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    I just wanted to post a follow-up on how everything turned out. First, thanks to all that replied with opinions and suggestions. I called the store I purchased the speakers from (Park Avenue Audio in NY) and told them that there seemed to be a problem with them. Once in the store, I was told that the woofer seemed to be blown on both (?) speakers. While the speakers were in the shop awaiting their replacement parts, I purchased a Parasound 855A amp and a SPL meter. Once I had my speakers again, I immediately connected them to the amp and didn't check to see if they would still shut down with my receiver. I guess I don't want to know. [​IMG] Everything works perfectly and the speakers sound awesome.
    Anyway, thanks again. Now, to see why I get a humming sound when I hook up the laserdisc player to the receiver but only when the amp is on. Hmmm. If it isn't one thing...
    Angel
     

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