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#6273 - 10/12/02 12:54 PM Re: M80ti: Problem with Harman / Kardon AVR520
chesseroo Offline
connoisseur

Registered: 05/13/02
Posts: 4849
Loc: western canada
Murphy,
your post is rather inflammatory by essentially blaming the people on these forums for the obvious fault of the H/K receiver.
I don't believe the 4ohm M80s need massive amounts of power to get them to work properly. People have driven the m80s with receivers that had far less power specs and some were not even rated for 4ohm speakers (look around some other forums for this info or pose your question about it to Alan or Ian). If the H/K IS rated for 4ohms, then the fault lies with H/K, not Axiom.
It is quite apparent that the annoying protection circuitry of the H/K AVR520 is more sensitive than people realize. But how do you expect the forum posters to know that unless they actually owned this receiver? If they are giving someone advice about whether a receiver should be able to handle a certain set of speakers, the most information they have to provide advice comes from the spec sheets on the product.
There is no reason (after looking at the H/K tech specs) that the AVR520 should have any issues whatsoever.

Take up your beef with the person who sold you the H/K or Harmon Kardon the company. Don't get angry at the forum posters who understand the specs required and the specs given. It was all i had to use in deciding and committing to my first receiver purchase and i don't have any complaints. Mind you , i also bought a receiver that DOESN'T have protection circuitry. My last Technics system did and i realized i NEVER wanted to see that cr@p again!
_________________________
"Those who preach the myths of audio are ignorant of truth."

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#6274 - 10/12/02 01:17 PM Re: M80ti: Problem with Harman / Kardon AVR520
murphyman Offline
buff

Registered: 05/09/02
Posts: 48
Loc: michigan
not just h/k but also onkyo and dennon I've see in posts that the m-80's were triping off the auto-protect and there was even one guy on this board who listened to me after trying the half dozen other suggestions and wrote back to say "YOU WERE RIGHT' but maybe you're on to something with looking for a receiver without the auto-protect....ever see an amp light up from pushing it to hard? It seems to me that alot of people on this board protect the m-80's from this topic when it is very clear to me that most a/v receivers of today don't do well with the m-80's.no big deal but people who do have problems with this issue seem to get more of the run around then help.its the power supply,the wall plug,you're cabels.etc.etc.etc.its simple trade up for a pair of m-60's or get more power. oh and sorry to hear about you're inflamation........

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#6275 - 10/12/02 02:25 PM Re: M80ti: Problem with Harman / Kardon AVR520
john_henderson Offline
veteran

Registered: 09/03/02
Posts: 186
Murphyman,
I think that you are over generalizing here, Even though many lower end receivers state that they are capable of driving 4 ohm loads the power supplies in them are just not up it. With many such amplifiers, you can drive a 4-ohm load safely, as long as you don't try to drive it too hard. If you drive a low-Z load to too high a volume, one of several things may happen: the amp may begin to "clip" (sounds very harsh and distorted, may damage the tweeters), or may overheat and shut itself down, or in the case of units without a protection circuit built in may overheat and burn up.
In your saying buy more power, you are overlooking the main problem that resides in the flaw of the receiver. I would challenge you to find anyone with the likes of the Denon 3802 the Yamaha RXV1000, or the one of the better Onkyo amps that has this problem. In your buying more power you have also bought yourself a much better power supply that can handle the 4 ohms at higher current levels. You DO NOT need all that power to make these speakers work. You do need a unit that can provide the current, I don’t care if the amp is 600 watts if the transformer cannot deliver the required current for a 4 ohm load you will have problems. A 50watt high current amplifier will do just as good a job driving these speakers as any. The bottom line it was the receiver not the speakers that were your problem.


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#6276 - 10/12/02 04:54 PM Re: M80ti: Problem with Harman / Kardon AVR520
murphyman Offline
buff

Registered: 05/09/02
Posts: 48
Loc: michigan
my receiver is an onkyo 787 HIGH CURRENT a/v receiver.new it listed close to a grand and was supreceded by the 797 for prologicII. what is the weak link in this receiver?is this a lower end receiver?I have had several people on this board tell me I should not have any problems with this receiver and I should have more than enough power to use m-80's but the receiver says no way.I even talked to onkyo and they said it was the speakers and not the receiver.so if you can please tell me what the problem is exactly and what I can do to fix it other than an outboard amp.I'm sorry I ticked a few people off but I see this stuff go on alot on this board about this subject and I would have been prety upset if I paid serious bucks for a pair of speakers that did'nt work with my system after getting the go ahead from the company and members of this board.come to think of it thats exactly what happened.

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#6277 - 10/12/02 10:06 PM Re: M80ti: Problem with Harman / Kardon AVR520
chesseroo Offline
connoisseur

Registered: 05/13/02
Posts: 4849
Loc: western canada
Murphy, unfortunately i cannot directly compare your problem with the Onkyo 787 and the M80s however i can at least tell you about my setup and present experience.
My Onkyo 797 is normally hooked up to M60s but i have had a friend come over and test out his Kef's which are 4ohm rated. The 797 drives them without any problems and this is without having changed the setup options from 6ohm to 4ohm.
I really do believe that 787 should be up the challenge. But maybe it simply is not.
_________________________
"Those who preach the myths of audio are ignorant of truth."

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#6278 - 10/12/02 10:16 PM Re: M80ti: Problem with Harman / Kardon AVR520
john_henderson Offline
veteran

Registered: 09/03/02
Posts: 186
The weak link in the receiver is the power supply. And yes for 4 ohm loads that is a lower end receiver. Why don't you connect the M80's to your receiver, and hook them up so as to present them to your receiver as an 8 ohm load. Then see if you can get it to shut down?

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#6279 - 10/12/02 11:41 PM Re: M80ti: Problem with Harman / Kardon AVR520
murphyman Offline
buff

Registered: 05/09/02
Posts: 48
Loc: michigan
my 787 has no switch to go from 4 to 80ohm so no go there also it states the 787 is rated at 6 ohm.I have used other 4 ohm speakers with this receiver with no problems at all.what are some good 4 ohm load receivers that are comparable with the onkyo 787?and why is this a lower end receiver? same amp and power supply as the 797.who knows maybe Onkyo makes junk.as far as kef speakers go they may have a 4 ohm rateing but it's a diffrent speaker all together so you can't compare

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#6280 - 10/13/02 12:24 AM Re: M80ti: Problem with Harman / Kardon AVR520
john_henderson Offline
veteran

Registered: 09/03/02
Posts: 186
Murphyman,

Having a 4, 8 ohm switch would not help you in hooking up the speakers as an 8 ohm load. There are 2 ways you could do this.

1. use 4 ohm 15-20 watt resistor in line to make the amp see the load as 8 ohms, you will have to be careful with this as the resistor will eat up a lot of power which is dissipated as heat so it will get warm it may get very warm depending on how high you drive it. Also the resistor will change the response of the speaker but it is not sound you are testing.

2. Hook up the speakers in series; this will also present the load to the amp as 8 ohms.

I would not say that Onkyo makes junk they make some very fine products, but you also have to realize that the 787 is targeted at a certain market, and for the most part people who buy this receiver also will buy speakers within a given price range. And for the most part these speakers are 8 ohm. One of the areas that manufacturers cut costs, is in some of the most expensive components. Amplifiers capable of delivering high current for low impedances requires discrete output transistors to carry the current, large heat sinks to dissipate heat, big filter capacitors, and massive power supplies all of which are expensive components. To make the receiver in that price range some this is sacrificed.

When a speaker impedance rating is given the value stated is a nominal value a 4 ohm speaker could be anywhere from say 5.5 down to 3 ohms. For the most part it is the flagship receivers of these companies Denon, HK, Onkyo, that are capable of driving these loads without any problems. Any receiver that is THX Ultra Certified is supposed to be capable of driving speakers down to 2 ohm loads. The power supplies in these units have to be capable of delivering the high currents required to do this, so a 4ohm load is not much of a problem for them. To your model of receiver that 2 ohm load is like a dead short it will go into protection mode immediately. When you connect to a 4 ohm load the unit can drive this at low volumes, the minute you begin to push this the unit heats up and will very quickly into protection mode. I think that your confusion lay’s in the current vs power thinking you have. High current does not mean high power. You can have 400 watt amplifier that can drive 8 ohms very well but the unit does not have the capability to deliver enough current to drive a 4 ohm load. On the other side of this you can have 50 watt high current amp that will be happy to drive 4 ohms all day long if the power supply was designed to do so.


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#6281 - 10/13/02 01:11 AM Re: M80ti: Problem with Harman / Kardon AVR520
murphyman Offline
buff

Registered: 05/09/02
Posts: 48
Loc: michigan
so basicly you are saying that my 80's are drawing too much power from my thx select tx-ds787 receiver and setting off the auto protect.right?you also stated that my receiver is marketed for a cheaper or less performance speaker other than the m-80's,is this also correct.so for these reasons my onkyo cannot handle the m80's.this I all agree with and have stated in the past posts is what should be told to people right off the bat.in basic the m80's require more power than what my receiver can handle,a thousand dollar receiver can't handle these speakers? its not the power output required but the power consumption. so in you're opinion what would have been a better choice for this type of receiver and why?

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#6282 - 10/13/02 01:39 AM Re: M80ti: Problem with Harman / Kardon AVR520
john_henderson Offline
veteran

Registered: 09/03/02
Posts: 186
No, again you are confusing power and current. Simply stated speakers do not draw power from a receiver. The speaker functions simply as a result of the voltage and current supplied to them. The 4 ohm load of the M80 requires your amp to deliver more current to them then does the 8 ohm load of the 60 for the same power. From what you are telling me is happening I would surmise that the Power Supply of this unit is not capable of delivering the current load required without overheating. I would say that looking at the specs on the Onkyo web site that this unit should be capable of running the 80’s without too much trouble, and looking at the published specs, my only concern is that it would run a bit hot with the 80's 4 ohm load. I feel that the problem lays with Onkyo not Axiom on this. If you can get the specs of the power supply from Onkyo you should be able to calculate roughly what this unit is really capable of. Obviously there are some short comings in the design of this unit, you cannot blame the speakers for this, nor can you expect that Axiom test their speakers on every receiver made. They like I do, would look at the specs given to them for the unit and from this deduce whether or not it should work with a given speaker.


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