Help: Why Did Sony 4ES Sound Shut Off ?

Tom Beski · 03-25-2003, 10:02 AM

Please explain what happened....

Last night I added 2 rear surrounds and changed over from 5.1 to 7.1 --- When I was finished I put in my Gladiator DVD to enjoy the new set-up and it sounded great. Then during a loud battle scene when a catapult shoots a fire-ball, my Sony 4ES completely shut off the sound and gave me the following warning in the display:

"Protecting...Turn Off Power"

I turned off the receiver power, waited 30 seconds, and turned it on again and it played fine...although I didn't go as loud this time.

Does the fact that I added 2 more speakers spread my available power even thinner so that I overloaded the receiver?? I never had this problem before using the 5.1 set-up and it has been played very loud. (Also never had this happen with my older Sony STR-DE945)

I have heard the term "Clipping"....is this what happened and how can I prevent it??

Also, whats the best setting on the 4ES to get the most out of movies with my 7.1 Set-Up ??

Thanks in advance,
Tom

Recv: Sony 4ES
Fronts: Polk RT800i
Center: Polk CS400i
Sides: Polk F/X 500i
Rears: Polk RT35i
Sub: SVS 25-31PCi

AaronBatiuk · 03-25-2003, 12:04 PM

Polk speakers are infamous for impedance drops. Although they are specified as "8 Ohms nominal" or sometimes even "Compatible with 8 Ohm outputs", they often are not so compatible, with impedance that can drop to below 4 ohms at some frequencies.

I would suspect that the problem is with driving your very difficult polk speakers. Seven may be just too many.

Try flipping the impedance switch on the back panel of the receiver to 4 Ohm instead of 8 Ohm. This will enable the 4ES to drive your array of Polks more easily. You will (theoretically) get a very slight drop in peak power output (less than 1 dB), but the amp will heat up a lot less, and you will probably never get the protection message again.

Tom Beski · 03-25-2003, 12:22 PM

Aaron,

Thanks for the reply....

Are you saying it's OK to flip my switch over to 4-Ohms and leave it there "permanently" even though all of my speakers say 8 Ohms ?? Does this also hold true if I am listening to 2 Channel Music?

Also, based on your response, it sounds like my speakers were more of the culprit and not the Sony Receiver....is that correct ??

Tom

AaronBatiuk · 03-25-2003, 12:52 PM

Yes, you can leave it at 4 Ohms safely. The only real drawback is a small reduction in the maximum output power of the amplifier. A positive side effect is much cooler operation. What actually happens when you switch to 4 Ohm mode is that the amplifier operates with a lower voltage power supply (the main power transformer has two sets of outputs, and the switch selects which to use).

Due to the slightly reduced power output, you may be able to push the amplifier into clipping during loud passages. This happens when the amplifier runs out of headroom trying to track the signal as it gets higher in amplitude (the voltage it wants to output exceeds the voltage of the power supply), and maxes out as some point, effectively clipping the top off of what would have been a smooth waveform. If you hear the amplifier clipping during very loud passages (and you almost certainly will hear it if it happens; it sounds outright nasty), then you are pushing the receiver beyond its limits. You will clip the amp at a lower volume in 4 Ohm mode than in 8 Ohm mode, but as you have seen, in 8 Ohm mode, the overload protection circuitry can trip even before the amp(s) clips. It is somewhat of a trade-off.

If, after switching to 4 Ohm mode, you notice clipping or the protection circuit still trips, you have a few options:

1. Turn down the volume!

2. You have a subwoofer, so you can relieve the power requirements on the other 7 speakers by increasing the crossover frequencies for them. This redirects more of the power-hungry bass from the smaller speakers and sends it to the subwoofer. The result is more of a demand on the subwoofer, but less strain on the receiver's 7 amps. The 4ES' high-pass crossovers have a measly 6 dB/octave slope, so setting the crossovers relatively high would be advisable in any case. With 6 dB/octave crossovers, I would recommend setting the crossover point to 2x to 3x the lower frequency limit of the speakers (e.g. small surround speaker rated for 50Hz to 20000 Hz... set crossover to somewhere between 100 and 150 Hz.).

3. Switch back to 8 ohms. This will increase the instantaneous power capability of the amplifier, but opens the possibility of tripping the protection circuitry during very loud passages, due to drawing too much current through the amps.

4. Invest in some external amplification, for some or all channels.

terence · 03-25-2003, 01:15 PM

Before you do what AaronBatiuk suggested, look to see if there are any wires touching behind your 4ES or yiur Polks at high volumes touching wires will send AVR's into protect mode.

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Mark All · 03-25-2003, 05:48 PM

I'm pretty familiar with Polk speakers. I'd also suggest setting all of your speakers to small, even the RT-800is since you have an excellent subwoofer. If you want to run your mains as large for some reason, I'd suggest a separate two channel amplifier for the mains. You are likely to notice an improvement in two-channel music this way. It's probably not necessary to use a separate 5-channel amp for home theater though. The 4ES works pretty well as a pre-pro if you already like the Sony sound with your Polks.

Tom Beski · 03-26-2003, 09:24 AM

Thanks for the replies....

I have always set all speakers to "small" and the cross-over is at 90....

Should I consider changing my cross-over (Higher/Lower)??

I think Aaron has suggested changing it to 100 - 150...any other opinions out there ??

Tom

NickSP · 03-26-2003, 12:20 PM

Tom, I am using my 4ES as a prepro but when I initially got the receiver, I was amazed at how loud and clean the 4ES' amps drove my 89db efficient speakers and was surprised to know that your receiver went into the protect mode. However, with all power hungry speakers running at the same time it could be an issue on most receivers.
Try this out. In your speaker setup, don't select the "back" speakers i.e. Back speakers = "No". This will then result in a 5.1 setup. Change the crossover frequency for all your speakers to "STD" including the subwoofer. Then play something like LOTR and gradually increase the sound and see at what stage it goes into the protect mode, if at all. Once that is done, go back and select the "Back" speakers and set their crossover to "STD" and see if it goes into the protect mode.
I personally would not advise you to set the crossover of the speakers to more than "STD" as it will "localise" the bass output from your subwoofer. Good Luck

Aaron H · 03-27-2003, 10:45 AM

NickSP,

Your comments are very interesting to me. I had a 4ES, had to return it for financial reasons, but plan to buy it again in the next month.

Anyway, I have to admit that I really did not tweak the receiver or set up my speaker levels with a SPL meter, but one thing I noticed is that the bass seemed very localized with my B&W 5.1 setup with an SVS 25-31PC+. Is the STB crossover standard? i.e. if I did not change it, was it always set to STD? The localization of the bass always kinda bothered me, and I'm looking for any tips to minimize this when I get the receiver again.

Thanks for any tips you may have.

Aaron

NickSP · 03-27-2003, 11:51 AM

Aaron H, the bass tends to get localized when the crossover frequency of your speakers is set high. I think the DA4ES sets it's standard (STD) frequency at 120Hz. IMO, its quite high to begin with. I have set my speakers at 90Hz across the board. However, when I had my speakers set to STD, I never really felt the bass was localized. Try different placements with your sub. You don't want it too close to the wall or a corner as it adds to more boominess resulting in localization. I think your main speakers should go as low as 60Hz. and if they do, I'd set the main crossovers at 80Hz taking the bass rolloff into consideration. You should be fine then.

Tom Beski · 03-27-2003, 12:15 PM

Nick,
Thanks for the help and suggestions......Here is more information that may help:

1) I bought the RT35i brand new about a year ago....I had used them "Stacked" on top of my RT800i using the A+B switch since my old Sony STRDE945 Receiver set at 4ohms let me play the 800's on "A" and the 35's on "B" at the same time and STILL have all HT Surround modes. The new Sony will only play in 2 Channel using this method but since it has 7.1 I moved them to the back. (But all speakers have played fine over the past year at high volumes with both music and HT so I know it's not the speakers).

2) I have a 50 foot run of Monster cable to reach from my Receiver, down through the floor, across the basement and back up through the floor to the 35i rear speakers. That is the same 2 pieces of wire that I used for the F/X500's when they were in the rear before I moved them to the sides. Now I also have 2 more new 50 foot runs to get to my side surrounds.

QUESTION: (Should these lengths of wire be reason to switch over to 4ohms on the Receiver or will that make the receiver work more??)

3) Just before I added the two speakers, I forgot that I was playing around with my crossover and I had everything set to 80 which may have been too much for the receiver at that part of the movie with that big impact of bass. I have since switched back to the receiver's STD default setting of 120 and will do more testing tonight and over the weekend with the same Demo materials.

4) I just bought the Sony 4es Receiver brand new and it is only about 1 month old. I am still learning the settings and continue to experiment and test it's features and capabilities.

5) Last night I re-checked all speaker wire and connections, and then re-calibrated the system with AVIA set at 85db and also did the phase test. (Not sure if the 7.1 system was calibrated when I had my problem)

6) Played the Eagles-Hell Freezes Over last night very loud after calibration and it sounded great.

QUESTION: If my problem happened with the Crossover at 80, and the 4ES does consider 120 as "STD", should I find a happy middle and set them at "100" or is the STD 120 Still better?? (I Guess the answer will be to try 120, 110, 100, and 90 to see which works best for me !?!?)

Thanks,
Tom