Protector mode?? - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 09-25-15, 10:48 AM Thread Starter
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Rudy

Join Date: Jun 2012
Location: Great State of TEXAS!!
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Re: Protector mode??

how about some good....reasonably priced amps for my system? thx.
Legendary70 is offline

Old 09-25-15, 10:06 PM
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Not knowing your budget,I'd suggest starting with emotiva. Bang for the buck is really high. I've been watching eBay for some, and also on eBay, I've watched some nice adcom 555's. They're a little older but measure off the charts. For about 300 bucks to the door, I say good value. Also a lot of the guys here use pro amps by Yamaha, peavey, and behringer, etc. tons of options. Pawn shops are usually full of used pro gear. Might be worth a trip.
willis7469 is offline
Old 09-26-15, 12:57 AM
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Re: Protector mode??

Some quick math that will explain why you're hitting the Protect Mode on your receiver:

The unit dB is a logarithmic scale that measures changes in levels that are too large to track linearly. What that means is where deciBels ADD, watts MULTIPLY. Here's the simplest version...

+10dB = 10X Watts (conveniently, +3dB = ~2X watts, and +6dB = ~4X watts)

If we apply that idea to the specs on your speakers, namely the Sensitivity, we get the following figures:
92dB @ 1W
102dB @ 10W
112dB @ 100W
122dB @ 1000W

Your speakers have a Max Power rating of 250W, meaning that the will produce a peak dB SPL of ~116
(92+10+10+3+~1 = ~116). But if you're watching a movie and the SPL in your vieweing area is around 103dB, a loud sound effect in the movie could theoretically generate an SPL of 123dB, which would mean your speakers need 1000W+ to reproduce that signal.

Your receiver's specs are a little vague... the most optimistic reading of them suggests that the front channels can deliver 110W into 6 Ω (at 1kHz, 1%THD)... but in terms of dB SPL, that's ~112dB. That's respectably loud, but consider that 115dB in this case would require 200W, and 118dB would require 400W... suddenly bouncing off the protection circuitry doesn't seem that far-fetched.

The main reason the protect mode clamps down so fast is that while the amp might be able to dissipate the heat, and the power supply might be able to deliver the current, you'll be clipping the signal and sending massive amounts of distortion to the speakers. This is has very serious consequences, as clipped signals have the potential to overheat voice coils much faster than clean signals at higher power. Sony has opted to shut the outputs off when certain levels of clipping are detected rather than field all the angry phone calls about a 110W amp destroying 250W speakers. (Good move, Sony)

The good news is that you're not going to harm your speakers any time soon... the bad news is that under seemingly normal circumstances, that receiver can't drive those speakers at the desired level while watching movies. The worse news is that after looking up your receiver, it doesn't appear that you have any pre-outs other than the two for the subs. What this means is that you basically need a new receiver with a much beefier amp section, OR you need a pre-amp/processor with line level outs and an outboard amp.

The Emotivas are pretty well-known in these forums but they can be pricey. I'm running an Outlaw 975 (extremely flexible connectivity, REALLY low price considering the feature set, but very stripped down in terms of menu options and user-editable settings), and I'm quite happy. The downside to this approach is that it requires an amplifier channel for each output channel as the pre/proc is incapable of driving speakers by itself. Obviously, this gets expensive pretty fast.

My old Yamaha had pre-outs in addition to amplified outs, so that might be a viable solution for you as well.

As for an amp that would drive those speakers adequately, the Crown XLS1000 is a good match at 215W @ 8 Ω.
DqMcClain is offline
Old 09-26-15, 04:40 AM
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Wayne Myers

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Location: Lincoln, NE
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Very nice analysis, very detailed. It is worth noting that the original speakers, the JBL e90, were less efficient, and he did not run into protection problems with them. Thus the suggestion that impedance curve might be a factor, if it dipped below 8 ohms, which is not uncommon even with a speaker rated nominally at 8 ohms. Just a thing worth mentioning. Thanks again for the nice analysis though, it is very helpful.
AudiocRaver is offline
Old 09-27-15, 12:05 AM
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Yeah, that was a good read. Thanks.
willis7469 is offline
Old 09-27-15, 03:18 PM
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Re: Protector mode??

Good point Wayne... and after you mentioned it, I do recall reading that earlier in the thread. Can't believe I missed that... but I have another theory:

Maybe the lower power handling capacity of the S312ii's causes them to distort at lower power levels than the e90's (440W vs the s312ii's 250W) and it's the distortion that triggers the protection mode. It wouldn't be that difficult for the amp to detect some level of distortion in the signal and call that the trigger for a shut-down...

I thought about a resonance (air column, port, or driver) causing the impedance to get weird at some frequency, but those usually drive impedance up which would NOT cause the amp to try and deliver more power... though I suppose that resonance could cause the aforementioned distortion and trigger the shutdown that way.

I could be wrong. I'm just some guy.
DqMcClain is offline
Old 09-27-15, 04:13 PM
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Wayne Myers

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Re: Protector mode??

You are being very thorough. I like that.

You could be right. I don't normally think of the max power specs on speakers being points where anything particular happens, just power levels to watch out for, lest damage possibly occur. In this case, though, the spec difference is very large, 440:250, or 1.76:1, and I agree that it is conceivable that the Sony could be receiving some back-emf from driver non-linearity, pushing it into protection mode. If that was the case, naturally the distortion would not be heard, as all sound would come to a screeching halt in a fraction of a second. Interesting theory.

And, as you say, all the more reason to consider a beefier amp.

I wonder if the OP has considered an outboard power amp? Even just for the mains, let the Sony handle all the surround power, which should be easy duty for it.
AudiocRaver is offline
Old 09-27-15, 04:38 PM
Senior Shackster

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Re: Protector mode??

I think an outboard amp was the conclusion OP reached... but that model doesn't have pre-outs that I saw, so he may be up a creek without a new AVR or pre/proc.
DqMcClain is offline
Old 09-28-15, 10:30 AM Thread Starter
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Rudy

Join Date: Jun 2012
Location: Great State of TEXAS!!
Posts: 142
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Re: Protector mode??

Thank you all for the advice. Mclain great explanation. I am going to hit the pawn shops.

BUT good news is:

Everything is fine now. I disconnected everything and started from scratch. I put on new plugs on all 7 speakers. Wiped all dust off. Reconnected everything and crossed my fingers. I blasted songs like the hills, love me, bounce it, etc. And of course some of my rock songs like from can to cant, staind, metallica, etc. Bass was awesome and no protector mode. So I moved on to movies. Still crossing my fingers. I started with Jurassic Park (the trex part), Battle LA, Star Wars, etc. Happy to say it jammed and no protector mode. Before playing the songs and movies I went through the settings to make sure all was well. I noticed the front speakers were on large. I can swear I had them on small before the move. Either way I fixed it and everything is working great. I guess it was a messed up speaker cable or plug. So does this mean my poor Sony AVR is better than we thought? I will never buy sony again thats for sure. I will stick to yamaha and onkyo. Thank you all!!

I do have one last question:

If I was to put the front speakers on Large. Would that just give me more bass sound? I have both my subs on 100 crossover. thx.
Legendary70 is offline
Old 09-29-15, 04:23 PM
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Re: Protector mode??

Sounds like it just needed some attention. That's always the cheapest solution. Sometimes NASA Mission Control will recommend you tap the gauge with a pen before you start doing stupid stuff.

Typically, if your Front L/R are set to Large the AVR will send the LFE channel to those channels, and disengage any HPF it might have. Conversely, if you're set to Small the AVR will separate the LFE channel and engage the HPF for the front channels.

Generally speaking, having your front speakers and your subwoofer reproducing the same frequency range is not desirable. What tends to happen is you'll get phase cancellation at various places in the room, and at various frequencies depending on the location. (Known in the live-sound world as comb filtering). At high frequencies, these effects can be tolerable... but at low frequencies it can be anywhere from noticeable to nauseating. (LF Comb Filtering is the subject of huge amounts of debate and research).

So, no... don't set your front speakers to Large if you're happy with the sub. It might be worth digging into the manual and seeing if you can find a cutoff frequency for the HPF when Front L/R is set to Small, and matching the crossover on your sub to that number. That might well keep your amp section happier and operating more efficiently.

One final thought: If you DO set your fronts to Large and you find you LIKE the sound, ignore everything I said and do what you think sounds good. It's your house, and they're your ears.
DqMcClain is offline

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