Has anyone used the Onkyo 875 with their M80's? I know it has an impedance switch (current limiting) for 4 ohms but I would rather run it in 8 ohm mode to utilize full current. I can get one for a great price but I am concerned about it cutting out.

Sound and vision did a bench test with this unit and found that it produced 320 watts per channel into a 4 ohm load with the impedance switch set to 6 ohms, not 8 or 4. With the switch set to 4 ohms the receiver only put out 55 watts, hence the reason why I would not want to buy this receiver if it had to run in this mode.

http://www.soundandvisionmag.com/receivers/2463/test-bench-onkyo-tx-sr875-av-receiver.html

I don't think we've heard of anyone having problems with M80s and an 875, but I'm not sur we've heard of anyone using one, either. I'd definitely leave it in 8 ohm mode (whatever standard operating mode is) to prevent that sort of current limiting.

But you don't have to run it in that mode, so don't worry about it.

No I don't have to run it in 4 ohm mode, but will it cut out or overheat if I run it in 6 ohm or 8 ohm mode?

Not unless you'd like to play it loud enough and long enough to permanently damage your hearing.

Fair point.

leave the switch on 8 ohm.

Someone had the 875 around here, because we were comparing it to the 806. As I recall they were really happy with it (and the specs seem to support that impression) but I don't recall the speaker - but odds are it was the M80. Search the forum for 875 and you should find some comments that ease your concern. I was looking at the 806 and 875 and came away satisfied the 875 would handle my PSB's which, like the M80, run down to 4 ohms sometimes.

Hope that helps.

I had the 875 for 1.5 years with M80s and never once had any issue whatsoever with driving a 4 ohms. I now have the 876 and it continues to work flawlessly. I have a 7.1 system. There is no way that I can set the volume to the max without killing my ears (I have a rather small room though: 20'x15').

Thanks for the reassurance ibmack. I have just pulled the trigger and bought the 875. I expected to see it tomorrow and can't wait to set it up!! Have you set your receiver impedance to 4, 6 or 8 Ohms? Your room size is about the same as mine. Now all I need to buy is a projector(most likely pana ae-3000) and a sub(thinking about SVS PB-13Ultra).

Always leave your receiver set to 8 Ohms. The other settings are there to make sure it passes the requirements for the Underwriter's Laboratory listing.

They basically say that a receiver designed for household use can not have an instantaneous current draw of more than some number of amps, and in theory running a less than 8 Ohm load could produce a draw that high.

Setting the receiver to 6 or 4, places an artificial limit on the receiver's current draw (a lower limit anyway, most amps are current limited even at their 8 Ohm setting, but to a more reasonable level). In the real world, sometimes you want to pull a little more amperage to provide that bass kick. Nothing bad will happen with a few loud thumps a minute, though a continuous draw that high will shut down the amp.

If you do happen to shut down an amp, just make a note not to play it that loud again (make sure it is a written note, not a voice annotation, because you're likely making yourself deaf playing that loud anyway).

This is a timely thread...

I'm shopping for a new AVR and the 876 has appeared on my radar. Really good to hear of at least one person running their M80's with it without incident.

Looks like a fantastic receiver. The specs are amazing.

For those with the 875/876, have you been happy with it? The "Official" TX-SR876 thread over on AVS has me given me slightly cold feet over it, as there seem to be a fair number of 'quirky' complaints.

Drewy1, I am no expert and so wouldn't argue with anyone here, but I have my receiver set at 4 ohms as per what the manual says. I get all the power I need so I don't intend to change it. Enjoy the unit!

Peter, I followed the 875 AVS thread from start to finish and inspite of all the negative comments (there were also many positive ones), I never had any issues with the 875 - no overheating or anything. I sold my 875 and bought the 876 because it had Audyssey dynamic EQ in addition to the MultEQ on the 875 and that feature alone was worth the upgrade for me. Other improvements have made the 876 a little better than the 875 but they are essentially the same unit.

Oh well I plan to run the receiver in the 6 ohm setting as the power is limited to only 55 watts per channel in 4 ohm mode. It will be interesting to see if the receiver shuts down as I give it a decent workout.

Do be sure to share your findings! Inquiring minds want to know the outcome!

D1, the object shouldn't be to give the receiver a "workout", but rather to see if it does the job at normally loud listening levels which don't cause permanent hearing loss. At those levels the 875 will certainly be fine, but if you keep increasing the volume level for a better "workout", the 875 or any other unit will eventually shut down to protect itself from such abuse.

Well I have just fired up the 875 with the M80's and I am reasonably happy. I need more time to test with good source material to make a more rounded view. I had the impedance set to 6 ohms and no probs with the reciever cutting out. I ran it pretty hard and it did get a bit hot but I understand that this is normal for this receiver. I did expect that I would have unbearably loud sound coming out at high volumes but this is not the case. I measured sound level at peaks of 108 db coming out of the M80's from 1 metre. From my calculations this means I am only putting less than 50 watts into the speakers at this spl.
Axiom M80 SPL in room = 95 db /1 w/1 m
= 98 db /2 w/1 m
= 101db /4 w/1 m
= 104db /8 w/1 m
= 107db /16w/1 m
= 110db /32w/1 m
= 113db /64w/1 m
= 116db /128w/1 m
= 119db /256w/1 m
= 122db /512w/1 m

I can hear the M80's start to distort at around 110db which only equates to an input power of 32watts. The 875 has plenty of headroom and I am sure that there could be no clipping at 32 watts. Interestingly when I set the impedance to 4 ohms on the 875 I still got about 110db out of the M80's before distortion occurred. In 4 ohm mode the 875 is limited to 55 watts per channel.

Does anyone know why the M80's don't seem to be handling much power? I am sure it is not my ears distorting as it sounds like the woofer cones are breaking up at around 110db. The excursion of the woofers at 110db seems large. With the 875 I should be getting peaks around 119db = 256 watts.

Was this in stereo..i.e., the two M80s only?

If not, there was just a recent thread showing some receivers are actually putting out closer to 30 w/c when all the channels were driven...

The M80s have been tested with (I believe) 1,000 watts....

Drew, the m80's have been driven in lab tests at 700 watts continuous for 2 weeks, 24hr/day, and peaks upto 1,000 watts. I think the problem, and you seem to ignore others above that have a wealth of audio/engineering experience, is that your limiting the current of your receiver. To little power is a lot worse on a speaker than to much.

i.e. Set the speaker impedance switch to 8 Ohms.

If you still hear distortion it more than likely means you've pushed the amps in the receiver too far and they are clipping--turn it down. The M80s can take peaks of 1000 Watts, they just don't like DC.

The one meter SPL test is interesting...I guess. But is your seating position at one meter? (I get the spec sheet comparison, but don't think you are using this info correctly.) Test the SPL at the seating position. My Denon 3300 begins to clip at 0.035 distortion at 84 watts (if I recall the test sheet right). My PSB towers are 4 ohms, and I can get clean sound at 105dB. Not at one meter, but at 12 ft. In short, your in depth tests are hard to compare to real world use.

The problem, if any, is not the M80s. There is far too much written on them, and users here, based on well over 150 watts (the real kind, not the advertised kind) in normal use to blame the M80 for the lack of output.

It's well known that M80s can be driven for long periods of time at 800+ watts, the limiting factor would be providing clean sustained power to them.

Ok, so can the 875/876 (876 since it's the same amp, I think) be added to the list of AVR's that can't effectively power M80's? If so, I need to know because if I go with an 876 and still will need my LPA-1 to power my M80's, I'm going to have to buy a whole new AV rack.

That clipping & distortion is exactly what my Pioneer Elite VSX-43TX does when I crank up my M80's (at about that same volume) and is the reason I bought my LPA-1 to power them.

I will readily admit that don't understand as much as some of this as others do about the relationship between the output db and wattage.... I am not an electrical engineer.

So if he flipped the switch to 4-ohms, where it's known that the 875/876 limits the wattage to ~55, but yet it produced the same amount of volume before the woofer cones started bouncing against the stops, then what difference would and extra 100, 500, or 1000 watts make? That does not sound right to me.

Is Onkyo lying about their output? That would be contrary to all of the glowing reviews that I've read. Please correct me, but if the cones are moving as far as they can, isn't that he limit as to how much volume the speakers can physically produce?

I would suppose that the frequency being produced would play a big role too. Asking M80's to produce a 25hz tone, for example, and getting a low db reading before distortion sets in, wouldn't really be an accurate test because M80's are not designed to produce that low of a frequency - right?

Peter, I'm not the expert you are hoping for, but I'm pretty sure you are confusing clipping/distortion with the speaker actually bottoming out due to the speakers ability to handle power. What is being described here - and I don't think we have this story cleared up - is the M80 producing the exact sound it is getting from the amp - distortion. Why the 876 would be distorting/clipping is a more difficult question, and I could not tell you don't worry about it. In Denon I trust. But the build up to this point - and I mean no disrespect to the original poster - does not lead me to believe you are getting great info here. We have a gumbo of current limiting, EQs, and many unknowns. Don't jump off the ledge yet.

Thanks Zimm.

I guess the problem is that I don't have a good understanding the relationship between the speakers, the wattage/power/signal produced by the amp, and the amount of distortion heard. At least, I don't understand it as well as I ought to.

In my case, I did some of this testing when I first got my LPA, and if I remember correctly:

From my couch, ~12ft away from my M80's, running with a 50hz cutoff (the only DSP), and my SVS sub switched *off*, 2-channel audio, my VSX43-TX could drive my M80's to about 97-98db (using the de-facto Rat Shack SPL meter) and then the sound would start to distort. Highs got weird, bass got flabby, just not pleasant. And pushed any harder and SQ went downhill very quickly without any increase in db. I didn't keep it there for more than a second because I know that can damage speakers. That's loud, but not loud enough for 'reference' material, IMHO.

With the LPA and the same test, I can get to 105-106db. At that point there was just a hint of strain from the system, but that may have been my hearing, as that was more than adequate for 'reference' tests. And therefore, I am happy with the LPA.

How do I equate those db figures with the actual wattage that the amps are producing?

No ledge yet!

I don't think you'll hear the M80s physically bottom out either. What happens is as you push into higher volume levels is you reach the soft limits of the woofers excursion and you get a compression-like effect, dynamics diminish, but no physical stoppage until you push much harder.

On the other hand, squaring off the tops of the waveform causes a very harsh sound.

Peter, that is the very question I have been begging for an answer to. Your experience is basically what I was trying to explain. With a real (or closer to real) 125 watts you system works cleanly because you get those watts without distortion. With BS watts, as on most AVRs, you only get a fraction of those watts cleanly, and you are capped at 90 db.

But how you read a spec sheet to know which amp section will give you clean watts, I can't get an answer to. Too many dismiss the question with "all modern well designed amps sound exactly the same." Yet, in Onkyo's line a mode increase by one add 10 watts, but doubles the high current capability from 36 to 72A. That tells me the amp section of the more expensive model has some gizmo (tech term) that allows it to fuel more of the 140 promised watts before distorting the sound.

But...I have been told that is not a key indicator, and that figure is damn hard to find on most amps, so it is of limited value. All this brings me back to the dirty place - I must put some faith in the professional reviews. Few of us have a Denon and a B&K and an Onkyo to A/B test. Hopefully they give us a grain of truth to work with.

Otherwise, I just have to trust Denon, because I have been impressed with every listen for 10 years, and I can't say that about any other product I own - well, the PS3 is damn impressive too, it does everything but prepare diner.

Hi Peter,

I'd point out that in past years, I've generally avoided recommending Pioneer and Onkyo AV receivers to drive the 4-ohm M80s because of current-limiting/shut-down experiences reported by Axiom customers. It seems the Onkyo's some years ago had overly touch protection circuitry, and Dan Kumin's bench tests confirmed that. At that time, and even now, we have not had any problems of current limiting or shut-down driving the M80s with Denon or Sherwood Newcastle AV receivers.

It is encouraging that the newer ONkyo's--the 875, 876--seem to have more robust amplifiers. On the other hand, I'd point out that Dan Kumin's bench tests of power output are at a single fixed frequency--1 kHz--and you cannot extrapolate from that to music signals, which represent a very complex load across the audible bandwidth of 20 Hz to 20 kHz. Moreover, there are other factors going on that are not easily predictable. When loudspeaker voice coils have wide excursions at higher power levels, they actually generate current and send a spurious signal back to the amplifier. It's called back EMF (electro-motive force) and that will increase the complexity of the load that the amplifier "sees".

I tend to be the cautious sort and recommend the brands of AV receivers that I know--from testing at Axiom--and from customer feedback, will not have problems of early current limiting or shut-down when driven within their output limits. Obviously, if you are in a big room and/or listen at extremely loud SPL levels (quite common among many of my Axiom colleagues), then all AV receivers will run out of power and clip, which is why we recommend an auxiliary power amplifier (Axiom's A1400) to achieve clean, ultra-loud SPL levels, which the M80s will do. It is also why Axiom developed the A1400. Ian was weary of his five Denon mono-blocks shutting down, and those put out 350 watts into 4 ohms. At parties, typically two or three of them would shut down. I, of course, would retreat to the deck outside or wear earplugs!

Personally, I find peak playback levels of greater than 103 to 105 dB SPL insane, because it's louder than any real-life music save for some rock concerts. And those that I've attended I made certain I was far enough away to avoid deafening levels or damaging my ears.

All this is to try and point out that AV receiver and amplifier power output levels are very complex. In times past, amplifier power output was always measured over the full audio bandwidth, 20 Hz to 20 kHz, because it more closely echoed a real-world music signal. Single frequency power output tests at 1 kHz were reserved for the car audio business and were mostly ridiculed by those of us into home audio, because those measurements misrepresented what the amplifier would likely do with broadband music signals and gave abnormally high power output specs that car audio makers could trumpet in their ads.

I do hope current Onkyo receivers have more robust power output into lower impedances than in the past, because I'd like to be able to unequivocally recommend them, as I do with Denon, Sherwood Newcastle, H/K, Rotel and a few others.

But right now, I'm still cautious.

Regards,

Alan

Alan, thanks for the informative post, as always. Is there a place we can learn what Axiom included in the A-1400 that makes it superior (if that is the right word) to other amps that Ian worked to better? The A-1400 is out of my price range (for now?) but I'd love to know what elements make it so dependable, or what specs point out its robust nature. I hate just trusting name brands, but it seems like that is the smart play in the AVR market.

Thanks again.

Wow. Thank you very much Alan! Great info, as usual.

Oh yes, 105+db is crazy loud. I'd never actually watch an entire movie or listen to music at that volume. But I want my system to be able to peak at that cleanly if I need it to. Everyone enjoys cranking up a demo scene, every now and then.

I didn't realize that Onkyo's (of the past) were on the 'iffy' list for receivers. Of course, it doesn't technically matter for me because I can continue to use my LPA to drive the M80's, if I were to get an 'iffy' receiver.

Peter, I just logged on and saw the interesting debate continue so I thought I'd do a quick experiment. I measured the room level from 12 feet from my m80s (all 7.1 channels; Q8s, VP150, EP500) with the 876 driving into 4 ohms - and measured a little over 91 db with some Vivaldi - and measured over 95 db driving at 6 ohms (the 876 does not have an 8 ohm setting), with the same music. No clipping or distortion whatsoever. These were both max settings, but I could only tolerate it for about 20 seconds - my ears are still ringing.

Drew, your results should leave you even more than just, in your words, "reasonably happy". You established that your 875 can drive your M80s to beyond safe listening levels with ease. The distortion in the speakers at 110dB with some particular program material shouldn't be a cause for concern. All speakers distort at very high sound levels(note the NRC tests on SoundStage showing significant distortion beginning at their 95dB level)and you shouldn't confuse the fact that the M80s can "handle" over a 1000 watts without being permanently damaged with the entirely different matter of playing at those levels with low distortion.

The point about permanent hearing loss that I briefly mentioned earlier in the thread may need a little more emphasis. For a table of recommended sound level limits compiled from EPA and World Health Organisation studies see the third set here . Note that the first two sets of longer limits are for workplace situations where some long term hearing loss is considered acceptable by some. This doesn't apply at home. So, enjoy great sound with your M80s and 875, but hopefully when you're listening for enjoyment rather than running a test you'll keep those 100db+ levels just for split-second peaks.

More good stuff guys. Thanks to everyone once again. Glad to hear that you've got your M80's screamin' with the 876 without issue.

ibmack, do you have any heat issues with your 876? And how is the delay in switching HD resolutions? It seems that the two biggest problems that people report with it are high temps and 8+ second delays for video sync-ups via HDMI. Any comment on that?

The more I read about the 876, the more impressed I am with its specs. For the prices I'm finding (<$1,000), it really appears to be a fantastic receiver. Has all the bells and whistles that I'm after for a good price. It's a hard choice between it, the 3808, and the Pioneer Elite SC-05.

Or to just sit on my wallet and wait for the UMC....

Decisions, decisions.

Hi Peter, you might also consider the new Denon 2809ci, it has all the latest HD decoding, 8 position Audyssey MultEQ XT, Dynamic volume, and Dynamic EQ, and its a Denon.

Peter, as I had no heat issue with the 875, nor do I have heat issues with the 876. But since it seemed like something to do I mounted two temperature activated scythe S-flex fans on the top.

Switching between HD channels is faster (~1-2 sec.) than between digital and HD channels (maybe 2-3 sec). Sometimes it is longer although I don't know that it is attributable to the 876. I know the original 875 had some very poor switching times but that was improved with subsequent FW updates (incidentally Onkyo is very poor for supporting FW updates, but nevertheless they do distribute updates - or perhaps more accurately put, they allow them to become available to the community at large. Once you have done it once (RS 232 cable and optical image burning), it is easy).

Buy this unit you will not be sorry.

'Quack & 'Mack, thanks for that info.

The 2809 looks interesting. Thanks for bringing that to my attention. After being more-or-less out of the AVR market for the past 7 years, I'm trying to reacquaint myself with all the relevant model numbers.

I will definitely take a look at it as I'm comparing AVR's. My only hesitation with it is that it's lacking a few features that the 876 has; THX Ultra certification (probably meaningless, but it has the sticker ), a GUI setup (sort of confused as to whether or not it has one), more power, and that Reon processor (I want a 'good' upscaler), and by just about every review I've read, the Reon is placed above the Faroujda in terms of absolute upscaling performance. But still, looks like a rather potent receiver.

Happy to hear from a real user on the 876's HDMI handshake speeds. One or two seconds is certainly tolerable. 8+ is a bit long. And yes, I've read through all of the AVS stuff about firmware updates. I'm an IT guy and so I'm not afraid of doing such things, and I have a couple of old PC's with serial ports so that's not a problem. So I'm reasonably confident that F/W updates will not be an issue.

Thanks again guys.

The addition of the Reon chip really does give the Onkyo an edge. Notice that the flagship Denon does not use the Faroujda, but a Silicon Optix chip.

Peter (et al)
Re the Silicon Optix Reon chip, I saw a very recent article comparing new projectors that said the Silicon Optix HQV chip was the best scaler of the group. Mitsu That's pretty impressive. I give this review a bit more credit on this topic considering it is not the budget-AVR review guy, but the video review guy. I'm sure the AVR guy knows his stuff, but for the same chip in the sub-$1000 Onkyo to meet the critical demands of a videophile is a useful point opinion.

Hope this helps your selection process.

By all accounts the Silicon Optix chips are a couple of the best out there. I see Anchor Bay is the next big thing and that Oppo uses them in their top line players. I also suspect that the next rendition of the 38XX series will have a better video processor in it, although with everything moving to HD will it even be needed.

With all the hub bub over the video processor in the AVR vs. maybe the TV or BD processor is superior anyway, so the AVR's processor might be mute... I have NOT been able get reports on specifically if my Mitsub. WD-73734 DLP OR my Panasonic BD55 has a 'better video processor' than the Faroudja OR the Reon.

Combing the manual's spec sheet(s), I cannot see where a video processor is listed on eihter. It may well be, but I can not pick it out of the tech/spec nomenclature. So how in the heck can we 'on paper' wise compare video processor specs AVR vs. TV vs. BD player ? ? ? ? I always get the comment: " Just try them to see which you like best." Well I have read the differences may only be noticed by a videophile who knows what to look for. If I knew the lingo, could know I was making the proper menu changes (which I do not), then maybe I'd consider trying to see only what the experts can discern.

The question we all want to know from the specs or 'expert opinions' what devices video processor does the job better. So many of the aspects of audio and video we buy on 'expert recommendations' not having the know how to discern THE differences, BUT WE WANT THE BEST (spec and real world) BANG FOR BUCK OUR BUCK that our budget allows. If the answer is not easy to devine, it does not make the question inappropriate to ask, IMHO.
[...steps of soap box and prays for answers that the big guy upstairs may only hold...]

Edit: The only mention ( I can tell) in my TV manual is this.
Image Technology: DLP. 0.65" chip, 1920 x 1080 pixels with Smooth Picture™. Also says in another place: Supports DeepColor, a new standard that incorporates 10-bit color depth.
This all sounds like 'marketing speak' for "the video is the best. Trust us. Move along, no Specs. to see here..."
BD55 manual has NO video reference that I can tell. :o(

Edit #2 But I did find a ton of info on BD55's video here, though it is Greek to me)
Specs on BD55 (third party)

This is the kind of comment that brings my questioning in the post above. With MY WD-73734 DLP (HD1080P24) and BD 55, do I need to care if my AVR has a Faroudja, Reon or Silicon Optix chip in it. Does the Deaf Monk have an answer to (this apparent unanswerable) question?
{... goes off to contemplate navel in hopes to get this answer from 'higher sources'...}

Edit: Oh, I guess you mean the video sources (cable, over air, satellite) changing eventually to all HD (not just digital) signals. Would this be a way down the road thing until technology creates huge increases in bandwidth capacity than is currently available?

"way down the road" ?

I'm way behind the HD curve and I'm pretty much at the point of 'all HD' already. There's only one TV show that I watch that *isn't* in HD, and that's only because Dish Network and F/X can't agree on a price for DN to be able to carry F/X HD.

But I have sort of come to the conclusion that AVR upconversion *might* be an overrated feature. I have very, very little experience with various upconversion techniques and results, so I am hardly an expert.

But I think it just depends on what you watch. AFAIK, there are only two scenarios where you'd want to upconvert a signal. 1) SD TV and 2) DVD. The case of SD TV doesn't matter to me because as I said, almost all of my TV viewing is in HD. With DVD's, my DVD player has a Faraoudja chip in it, and it does a pretty good job. Perhaps ignorance is bliss in that department.

I'll be able to add more to this conversation in a few days. I've got an TX-SR876 on order that should be here on Tuesday. I'll be putting it up against my just-purchased SC-05 to see if the upconversion & features really make a difference to me.

Well I can confirm that the Onkyo 875 does shutdown at high volume levels when powering the M80's. Last night I managed to have it shutdown several times. The volume level at amp shutdown was pretty high at around 100db from my seating position however I would like to run at this level and up to 105db only for demo purposes(short periods of time). I am currently running the M80's full range with no sub.
Would the receiver draw less current if I was using a sub and have the M80's crossed over at 80hz thereby enabling me to run the receiver at volumes greater than 100db?
Does the receiver cut out due to overheating or just being overloaded? Would cooling fans enable the receiver to run at higher volumes? If the receiver is rated for 140 watts at 8 ohms, does this mean that the equivalent load on the amp into 4 ohms would be 70 watts?
Will running the receiver at volumes causing it to shutdown cause any damage to the receiver if done frequently?

My professional opinion: it aint good. That pretty much does it for my Onkyo shopping. Never had a problem with Denon so I guess I'll just skip the fretting and get another Denon.

Thanks for reporting your experience.

I think some cooling fans and a higher crossover should help, as this would take quite a load of the Onkyo, how much longer you could run at this level would be unknown. Better yet would be to get an outboard 2 channel amp to driv ethe M80s for this high volume levels. I am looking at the Pro PA amps out there like the Crown XTI1000 or Behringer2500, quite cheap for the power output. There are some reviews of owners running these amps like this and they are all very positive.

That would certainly help the AVR. I can't imagine it having a problem running 3.1.

The AVR did cut out while running 3.1. I must point out that the AVR sits in a cabinet and it does not have a lot of room on the sides for ventilation, maybe 15mm each side. It has about 200mm of clearance at the back, 500mm clearance on top and the front cabinet door was left open and the AVR still cut out.
Does anyone know whether the AVR cutting out is caused purely by overheating, drawing too much current or a combination of both?

To quote the manual for the 876 (which I in handy PDF format)...

"Leave 20 cm (8") of free space at the top and sides
and 10 cm (4") at the rear. The rear edge of the shelf
or board above the apparatus shall be set 10 cm (4")
away from the rear panel or wall, creating a fluelike
gap for warm air to escape."

Going by the book, you're space is too confined.

See the first section "Important Safety Instructions" in the 875's manual to see if it differs.

Thanks Peter. Looks like I need a new hifi rack!

I believe 3.1 was refering to the surround channels and center plus sub in a 5.1 system. not 3.1 as in front 3 plus sub. I should think if it cuts out running 2 surrounds and the center then it must be getting very hot.

Drew, as you describe the situation, the problem is almost certainly overheating alone. You didn't describe exactly how you measured the 100dB level, but assuming that your number is reasonably accurate for the max level, your M80s were using only around 20 watts for that peak. The 875 has been measured to be capable of more than 200 watts in such a situation. The protective circuits wouldn't have shut down because of excessive power/current being used.

As others have suggested, more ventilation room and/or a cooling fan would be advisable.

No problem drewy1!

Was the 875 in the 4-ohm or 6+ ohm mode when it shut down?

Here's a simple test....

If you can, pull the 875 out of the AV rack so that it's not confined. See if you can then get it to shut down at the volume levels that you wish to drive. Don't overdo it, but get it back to the volume level you want.

If it doesn't shut down, then it was the confined space. Get a new AV rack or explore the many DIY fan options that Onkyo users have come up with over on AVS.

If it does still shut down, then it isn't due to the confined space. If that's the case, then you may need to either get a different AVR or go whole-hog and buy an amp.

And another tip...

I know that with the 876 there was actually a "secret" set of key presses (on the front panel) that would display the AVR's internal temperature. A lot of people with heat issues would use this to see how close they were to having thermal problems. And to monitor how their DIY fan solutions were working. I don't know what it was, but if you peruse the AVS forums you might find something similar on the 875. Since they're so closely related, I'd be surprised if the 875 lacked this feature.

One thing I noticed in studying receivers lately, is how much heavier the Onkyo's are compared to Denon. They must have beefier guts or something, which can't be a bad thing.

The 876 (51 lbs) and 906 (59 lbs) compared to the Denon 3808 (39 lbs) and 4808 (41.6 lbs) has be thinking if I get a new receiver to give Onkyo a shot. That is a lot of difference.

Or Onkyo is gluing lead weights inside.

Beefier guts or thicker skin? Denon runs 4ohm loads(loudly) no issues, Onkyo appears to overheat, something seems wrong with the equation.

Awww, can't they use gold?

The new Onkyo's have issues? Now looking at the ventilation requirements, I wonder if that could be related. Being THX+ rated they should be fine with 4ohm loads, like the 80's.

Well the 875/876s, we are seeing reports of some shutting down, albeit at extreme levels, but still shutting down.

It does appear that the Onkyo's are shutting down due to heat issues from driving the lower loads and that better ventilation is required, maybe they need to be 70lbs, this would be with better heat sinks and some fans But for your purposes Randy, you have those Odyssey's so a major part of the load would be taken off the amps anyway.

My 876 sat on the top of an open AV stand, so ventilation wasn't an issue.

It did not shut down while driving my M80's up to ~100db (6+ ohm mode), but it did start to sound more stressed beyond that point. And by stressed, I mean that the bass lost definition, the highs became a bit screechy, and the whole soundstage became less coherent. Distortion without much added volume. Unimpressive.

At least when compared to how my LPA-1 handles the same situation, with SQ remaining clean and composed well past 100db.

That would be how I would describe the 3808 vs the A1400. The 3808 was good to about 103-105 on the meter but the A1400, well, I couldn't get it to sound stressed, I ran out of gain in the 3808 before the amp ran out of room. Then again the 3808 and the A1400 sound different at lower volumes as well.

Peter, did you notice much difference at lower volumes between the Onkyo and the LPA, anything similar to my 3808/A1400 comparison?

I measured the 100db sound level at a distance of 5 metres from the M80's. The AVR was running rather hot probably around 60 degrees C or 140 degrees F. I think I will try what Peter suggested and run the AVR out of the cabinet for maximum ventilation.

hmmm, thanks guys. I guess if I get closer to getting a new receiver, I may just stick with Denon, my 2805 has been great, even at high levels.

Hey Jay, I may not always have extra amps, so I'm looking for a receiver that can do well alone. My company just cut everyone's pay from 2-10% depending on your current status. I got 7%, plus no bonus this year. I need a new receiver bad, and am considering parting ways with my Odyssey's. This is going to be a difficult decision, since I love them so.

Maybe. I'm reasonably sure that the SQ of my LPA+VSX43TX combo is at least slightly better than the VSX43TX alone at all volume levels. I become more sure as the volume levels increase. But at low levels, it's not really enough that I'd feel comfortable shouting it from the rooftops here. I've switched back to the VSX43TX alone a few times (as my AV rack would look much cleaner if I could get rid of the LPA), and the SQ always leaves me wanting a bit. It's hard to describe, but with the LPA back up, I have a sense of, "ahhhh, there it is" with the SQ. I know, purely subjective BS. But it's how I feeel.

Compared to the SC-05 and 876, things are different. The 876's SQ did not impress me at any volume level, with the sound generally feeling thin and lifeless. Cold & processed. I didn't even bother trying the 876+LPA combo. The SC-05, on the other hand, was very impressive on its own. In fact, it alone sounded every bit as good as my VSX-43TX+LPA combo, even up to very loud volume levels. Maybe even better in terms of absolute dynamics and soundstage, as when doing LPA+SC-05 test, I actually preferred the SC-05 alone. Very lovely sound; with controlled bass, full & lush midrange, and clean & clear hights without a hint of brightness. Very pleasant to listen to, for me anyway. The only reason I didn't keep it was that its feature set was a bit disappointing compared to the competition. From a purely SQ standpoint though, it was magnificent.

If the UMC doesn't work out for me (or when I get to demo my buddy's 3808), then it's very likely I'll go back and buy another SC-05 or SC-07. If you do a little digging, you can find killer deals on those; SC-05's for less than $700, SC-07's for less than $1k. At least I could a couple of weeks ago....

Ouch Quack. That's no fun. Sorry to hear that bit of news, especially since you might end up selling the Odyssey's.

That's a serious bummer, Randy. Just this weekend I was getting the feeling that things might start turning around soon. Judging by all the people who were out shopping this weekend, you certainly couldn't tell there was something wrong with the economy in northern Virginia.

I think there are rumblings that things are bottoming out. At least, that seems to be the cautiously optimistic sentiment that some of the talking heads are saying. Of course, it could just be a dead cat bounce. I've got a realtor-friend that says that he thinks that home sales are actually starting to improve a bit - locally anyway.

Of course, nothing's just suddenly going to get better tomorrow. It's going to take months and months.

I agree with ya, Peter (so weird to type, agreeing with myself)... I was at the local mega-shopping area this weekend (The Mall, Best Buy, Barnes & Noble, etc) and it seemed as crowded as ever. Hard to park, lines at the checkouts. It sure seemed like people were spending!

Much of the recent activity on the Markets, was short covering. There are, finally some positive signs here and there, namely in the US home sales and mortgage lending. It'll be a slow recovery esp with the soap opera starring the car companies and the unions who seem intent on holding the economies hostage untill they get lots of your $$.

Whoop!! Whooop!! Off-topic Alert!

Onkyo has a diluted earnings per share of -85.72....::trying to bring topic back to 'Onkyo'::

That alarm's going to get some use around here.

Peter, You make a very good argument for you to bring in a 3808 to complete your very good AVR comparisons!

Charles,
So much so we'd need to create a keystroke 'shortcut' or add an emoticon for it.

(Peter, though off topic usually adds comic relief, etc, OT on the economy could easily take on it's own life in that there are few who, if not affected directly, have friends or relatives who are much so affected.... D'OH, I just added to the OT! )

Why it makes so much heat, and why it shuts down from heat are for the tech guys to explain, but even my Denon 3300 will cook a pot-roast in a closed cabinet with tons of space around it. I bought a fan for a computer CPU and spliced the wire to a 110 plug and connected to triggered output on Amp. Cut a hole in the back of the cabinet, or just aim it out the back of an open rack, and the amp will stay cool (at least my Denon did).

After moving my Denon to an open rack, I removed the fan, thinking it would be fine with open sides and back. Not so fast. After a few hours of pumping the other day, it started spiking the volume knob on its own and would not stop. I did a hard CPU reset, etc, no luck until it cooled. First time that has ever happened, and this is a 10 year old AVR, so this could be the result of years of hot work. But heat will stop an AVR no matter how heavy its guts. So the fan is back.

My advise: spend the extra cash on a good quite fan. I saved $ and I hate the sound the fan makes. Looking to upgrade now actually, so any computer pros in here that know a good fan that runs on 110 volts please let me know.

Thanks guys, at least in my situation I did get a small lump sum raise this year, followed by the 7% cut. At least I have a job, knock on wood.

I really do need a new AVR, my 2805 is just getting outdated. I want to get a bluray player as well some day to accompany a new receiver.

At least the Odysseys have a 20yr warranty that is tranferrable to 2 additional buyers.

If it makes you feel better, I'm still using an "ancient" Onkyo TX-DS575. You'll live.

get some 80's and burn that baby up.

LOL ! Ask Jay, he knows a special way to 'need' a new amp...

This is where I cannot make sense. If the 3808 is good for 103-105 db on the meter then it is only putting out:
95 db/1w/m
98 db/2w/m
101db/4w/m
104db/8w/1m
This means that the 3808 is putting out about 9 watts before it no longer sounds good. What am I missing here. This receiver should sound good up to 115db and above. Perhaps the readings were taken at a distance from the source. If the reading of 105 db was taken at 4 metres then this would equate to 111 db at 2 metres and 117 db at 1 metre. These readings would then make sense.

Drew, listening impressions not resulting from controlled double blind sessions with all variables held constant shouldn't be used as if they were established fact. The numbers in your post aren't realistic for listening to M80s at a typical distance in a typical listening room. For a 105dB peak level something on the order of 50-100 watts would be used. Also note than a 6dB difference per doubling of listening distance can't be accurately applied in a live room rather than an anechoic chamber. The difference would be far less, depending on room characteristics, but 3dB rather than 6dB would be closer as an estimate.

Like you said the distance are off, I am not measuring at 1M away, I am measuring at my listening position nearly 3M away, big difference as you noted.

A receiver being able to sound good upto its' limits has a lot more to do with the source than the amp itself. I find many CD's start to sound bad in that 95-100 db range in my room. I think I've been able to get Dire Straights-Brothers in Arms up to 106-107 before it starts to degrade, all this measured at my listening position ~9ft away.

I'm not sure what your results mean, but sitting 12ft from my speakers, my Denon 3300 can run in the low 100db range all day. Peaks can hit 107 or so, but it will run smooth vocals at 102 for hours. I don't know if that is 9 watts, or 99, but it is all you could need, aside from the benefits of additional headroom.

Similarly for the 1909 (90w), it should hit it's 90w at about 112 dB. From the 12' equivalence shown above, the 1909 should sound good up to maybe 102 dB? Just thought I'd chime in while dB/watt ratios were discussed (again ;o).

According to my calculations at 90w a pair of M80's would produce a maximum of about 117 db from 1 metre and a maximum of about 105 db from 12'.

I guess your calculations are wrong. I guess. Perhaps you didn't calcuate the room effect adding db to your calculation.