Axiom Home Page Forums General Discussion Technical Questions ARGH!!! Impedance question....

My first post.
First thing, I bought a pair of M50ti's a couple months back, and simply love them more than anything right now!
Axiom, you are the best sounding speakers I have personally ever heard in my 33 years on this earth!!!

Ok, now to the question.

I have a brand new Harmon Kardon AVR-330 Home Theater amplifier.
I have the Axiom M50Ti's as my front left and right speakers.
Now, I want to get the VP150 and QS8's for my center and surrounds respectively...but... the AVR330 is rated for only 8ohms...
I emailed Harmon Kardon and explained that I would be using 6ohm rated speakers from Axiom.
They responded with:
"The AVR330 us rated for 8 ohm speaker operation only. It is not recommended to use speakers with an impedance lower than 8 ohms. It is possible that you may be able to use the Axiom speakers but I cannot guarantee that the receiver will be able to handle this without protecting itself."

So what should I do now???
Should I now go with a Pre/Post amp setup before getting the speakers??

I would appreciate any information on this...

Thank you for your help!

-seven

I'm running 6 ohm speakers on my H/K 525 right now, and I've had no problems. I don't tend to listen to them extremely loud (I think -20 to -15 is the highest I've gotten them), but I've never hit the temperature protection or had the fan turn on.

Thanks for the reply kcarlile,

I read of others using lower than 8ohm rated speakers on their H/K recievers without any problems.
I also only go up to -20 on my volume. I dont really need to go any higher as I live in an apartment.
I was hoping that when I emailed H/K they would give me a little more information to go with... rather than the one they emailed me.

Anyhow, thank you for the information.

-seven

Hi seven,

In a general way, any A/V receiver designed for operation with 8-ohm speakers will always drive 6-ohm loads without any trouble. It is 4-ohm loads with the big increase in current flow that cause many receivers to go into protection mode or impose current-limiting circuits, which severely limit the output power of the receivers.

All manufacturers of receivers will be very conservative on this issue, as they don't want consumers driving pairs of speakers in parallel or very difficult impedances that might cause overheating and/or shutdown, although I'm surprised that H/K suggested caution with a 6-ohm load.

My experience with H/K (the AVR 525) is the same as kcarlile's. Despite the warning on the back panel (Use 8-ohm speakers), the 525 and other current H/K models will drive lower impedances--even 4-ohm loads--without overheating problems or protection-circuits kicking in.

The 525 will even drive the 4-ohm M80s with no problems, albeit in a modest-size living room (19 x 13 x 9 ft). On the basis of my own tests and those of several colleagues, H/K and Denon are the only brands of A/V receivers I currently recommend for the Axiom M80s. An engineer friend also tells me that the new NAD A/V receivers will drive a 4-ohm load without current-limiting or problems, though I don't have direct experience with those units.

Regards,

In reply to:

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the new NAD A/V receivers will drive a 4-ohm load without current-limiting or problems, though I don't have direct experience with those units.

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Are you kidding me? you can arc weld with them! lol. But really, i beieve on the recievers that they deliver whatever the rated power is, into 8 or 4 ohms. At least thats the way it is with their other amps (370,270 etc) and they have the rated clipping power in 8,4, and 2 ohms.

Alan,

Thank you very much for the information and clearing up my confusion on the issue.
I was also suprised that H/K warned me about using 6ohm strength speakers as well.

Again, thank you. I am excited to finally get rid of my Bose system and move to an all Axiom setup.

-Seven

Wow, a lot of people switching from Bose these days.

I sense we are entering a new period of enlightenment...

Such a relief after reading in a sales blurb that "some reviewers even thought [the sound from the Bose Wave Radio tm r c etc.] was live!"

Of course, when recordings were introduced in the early 20th century, people thought those were live, too. We all know what those sounded like...

Haoleb,

Not to disagree with you, but the NAD models you mention are 2-channel stereo amps. The NAD stereo models have always been good into lower impedances. It's 5-channel and 7-channel receivers where amplifier cooling becomes a huge issue with lower impedances.

And it's the continuous power output with five channels driven that separates well-designed power supplies in receivers from cheaply engineered units. "Clipping" power can be measured in a short-term instantaneous burst (and the manufacturer will make those claims, sometimes calling it "dyamic peak power" into loads as low as 2 ohms) but after a few seconds, the receiver will go into current limiting or shut down. (Naturally, that is never mentioned in specifications!)

By the way, lots of old stereo amplifiers and receivers had no problem driving lower impedances.

Regards,

So nice to hear I made the right decision when I got the 525... :-)

In reply to:

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It's 5-channel and 7-channel receivers where amplifier cooling becomes a huge issue with lower impedances.

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Hey if im wrong about something dont be afraid to say so.

On another note i can definetly see where heat would become a problem when drivnig 7 channels. My C370 gets fairly warm, especially over the area where the pre-amp "modules" are located. If i had 5 more channels in there that thing would get cookin!

They are tired of getting a headache after about 10 minutes of listening to the little buggers.

In response to:
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On the basis of my own tests and those of several colleagues, H/K and Denon are the only brands of A/V receivers I currently recommend for the Axiom M80s.
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So Alan, are you saying that I should re-think my decision to buy the Yamaha RXV1400 to drive my M80's with?

Shawn

You could always take advantage of the Yammi's pre-outs and buy an outboard amp...

Ah yes, I would love to, but I have to calculate in the costs of a vp150 & a set of qs8's. Where you live in the land of the free, I live in the home of the taxed! Until Ottawa quits taking so much of my disposable income, separates are out of the budget.

at what % are you taxed? If it's around 30%, you've no right to complain.

Hi Shawn,

If the Yamaha RX-V1400 has a switch on the rear panel for 4-ohm loads, it will likely impose a current-limiting circuit, so I'd suggest you either think about getting M60s (8 ohms), which any receiver will easily drive, or choose an H/K or Denon that will drive the M80s.

Regards,

OK...just out of curiosity, I checked my last pay stub. My average for the year? Just over 32%. Bleck...

Oh...and I'm "single" and don't own a home, so I'll be lucky if I see any of it back in the form of a refund in the Spring. Double bleck...

I just checked my last stub and 31.95% goes to Iraq -- I mean the gov't -- but I'm anticipating a return due to the baby. No child-related costs until November 15, but I get to claim him for the year. Ain't it great.

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I just checked my last stub and 31.95% goes to Iraq -- I mean the gov't -- but I'm anticipating a return due to the baby. No child-related costs until November 15, but I get to claim him for the year. Ain't it great.

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Now you know why i am a bit anarchist.

So your telling me that I WORK and then you take a percentage of my income? for nothing? just because this just so happens to be where i live?

ahem.. something is wrong with that.

Without taxes, there wouldn't be very many roads where you live. Or public schools. Or fire and police departments. Would you give those up to keep all your money?

Not a chance. I'd also pay more taxes for public health care. (oops, we're violating the No Politics rule!)

I'm curious. How much is a regular joe in Canada paying in income taxes?

33% here in Toronto. So its pretty much the same as in Cali. But the question is if the cost of living is higher than in Toronto. Toronto is the 104th most expensive city in the world. Ottawa is cheaper at 127th. I do not know how expensive Oakland is but Spiff is living the 22nd most expensive city in the world.
http://www.mercerhr.com/pressrelease/details.jhtml/dynamic/idContent/1096495

ps: It also depends obviously in the bracket you are in. I have a side business which I can claim lots of expenses and have a measly revenue.....umm..is this moderated by Revenue Canada.

Pretty Damn Expensive. However, I'm surprised at their conclusion that LA is more expensive than San Francisco. That's not been the way I've seen it...

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Without taxes, there wouldn't be very many roads where you live. Or public schools. Or fire and police departments. Would you give those up to keep all your money?

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Fair enough..

But think. just how much of that goes to those things. Our schools are run dry on money. our teachers paid a sweatshop salary our roads are a mess (here anyway). yet all the sudden weve got billions to spend on wars and fixin up other people broke a** countries..

alrighty then

Is housing cheaper in LA than in San Fran? I can't see Toronto as cheap either. A 800 sq foot condo in downtown Toronto can cost a median of $240,000 canadian $300/sq ft). Houses within Toronto is like 300,000-800,000. I'm taking median.

Spiff how much is rent in LA? for a place like 800 sq ft.

Yeah, median in the bay area is somewhere around $400K American right now. Peter might have a better idea.

Thats 524k cdn.. that might get you 1200 sq foot home with a 2 foot lot in downtown Toronto...if your lucky or a 1600 sq foot condo...and thats a generic condo. A nice condo/loft is $350+/sq foot

Of course, that's bay area overall. I don't know about downtown SF. Could be higher.

But damn, Toronto's expensive.

Greetings,

I can confirm to anyone interested in NAD that the T762 drives 6-ohm speakers without any problem. I have had the unit for over four months and with NHT 2.5Is (6 ohms, 3.6 minimum impedance), the VP150 and QS8s at loud volume levels for extended periods it never gets more than lukewarm to the touch or engages protective circuitry. The manual also states the unit is capable of driving 4 ohm speakers and I hope that is right because the M80s are in my near future. Anyhow, just wanted to confirm the NAD recievers have no trouble with 6ohm loads, and given the 3.6ohm low and 86db sensitivity of the NHTs, I doubt they will have any issues with a 4ohm load like the M80s. Regards,

Well... I'm somewhat lucky. I'm expecting money back (I have 4 kids)and my wife works part-time. However, most of it is going to pay my property tax, school tax, MUD tax and home owners insurance and any other tax that I may have for gotten, Oh well...

I live in Oakland. A small 2 bed, 1 bath, house with a tiny yard down the steet (most likely sub 1000 sq/ft.) sold for over $425,000 earlier this year. And people were scrambling for that one.

There's no hope for me in the area. I plan to move before I buy. The secret is saving as if I were trying to buy here in the next 5 years, and then slapping a huge downpayment on a house somewhere land is cheap.

Craig, since I do tax and investment advice on another board, I have to give you the same verbal(only) spanking that I sometimes give there. The idea is not to get a "refund", but to owe a little bit with your 1040. Otherwise you're just giving the government an interest-free loan of your money.

Shawn, it's highly likely that the 1400 will drive the M80s with no problem.

I realize it is best not to get a refund. My point was more that 32% of my income has been withheld, and none of that 32% is coming back to me. It's a true 32%.

As far as housing goes...I'm actually in the market right now, so I've been looking. In my neighborhood, thing are REALLY bad.

I did a search on www.realtor.com in my zip code just last week. In the 90025 zip code, the least expensive single family home was $519,000. It was a small 2bed 1bath.

Rentals aren't very good either. My brother has been looking. A standard 2bedroom apartment. Nothing huge, or super nice goes for about $1000-1300. Anything less than that is a pretty old, well worn building.

In reply to:

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Our schools are run dry on money. our teachers paid a sweatshop salary our roads are a mess (here anyway). yet all the sudden weve got billions to spend on wars and fixin up other people broke a** countries..

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Right on brother!

In reply to:

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somewhere land is cheap

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Mississippi?

In reply to:

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The idea is not to get a "refund", but to owe a little bit with your 1040. Otherwise you're just giving the government an interest-free loan of your money

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Right on brother!

You guys need to move to Houston. Med price for new construction $135,000 for 3 bdrm 2 1/2 bath 2 car garage.

Some people attribute the higher cost of living in California to the "Weather Tax"

But it's so easy to trick yourself into believing you're getting free money with that refund.

I know it's unfair, but the current administration has left a very bad taste in my mouth for Texas.

If I were to leave LA it would probably be north to Portland, or Washington.

In reply to:

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the current administration has left a very bad taste in my mouth for Texas

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No argument here about that. But political climate aside, Fort Worth really is a great place to live.

I resemble that remark...Define cheap?

keep going north, you're getting more Canadian with each passing day

I started off in Maine, so I was really close to being Canadian already.

John,

The reason I nudge buyers away from Yamaha A/V receivers if they are considering the 4-0hm M80s is that we've had the occasional Axiom customer who has gotten the 4-ohm M80s and their Yamaha goes into an apparent current-limiting mode, with low power output and audible distortion.

Those symptoms suggest the protection circuitry is severely limiting power output into low impedances. I don't know the specifics of the Yamaha 1400, but the engineering of the unit would have to have changed, which I doubt.

Regards,

Alan,it appears that the engineering has in fact changed. Although it's fashionable in some circles to poo-poo the THX certification as a mere marketing move, some of those who've gone through it have reported on the technical changes that have had to be made, reportedly including the ability to drive a 3.6 ohm load. Also, Yamaha at least claims increased current handling capacity, etc. Only time will tell, I suppose.

Regarding y'all's discussion of the relative tax burdens we all face: yes we pay too much federal income tax, but that's not the half of it. Add to that: state income tax; property taxes; unsecured property taxes; sales tax; taxes on gasoline, liquor and smokes; estate taxes; windfall taxes; user fees, registration fees, fees for this, fees for that; medi-care; medi-cal; social security; and on and on and on...
What does the worker get in return?
The largest expenditure at every level of our gov't is "entitlement" programs - not military, fire, police, or anything else useful. Free money to people who are not contributing. If you pay money to people for NOT working, why would they ever get up and go to work?
I wouldn't mind paying the taxes I currently do if they were used in ways to benefit all of us who contribute.
I feel like I'm going in on a pizza with all my friends, but the box is empty when it gets to my door. It's empty because the pizzaman handed out slices to every bum on the way - like he's freakin' Santa Claus or something. I guess that's how you get re-elected.

I take it the moratorium on political threads is over, then?

The current political climate in the US tends to get people worked up. You don't even want to get me started. I'm biting myself to keep from really joining in this fray...

Arrrr...

you hit the nail on the head.
dan

Hi John,

Well, that's good news if Yamaha has changed the design.

And thanks to Chadmat for the feedback on the NAD T762 and its ability to drive 4-ohm loads, which confirms what I've been told by one of our engineers, who worked on amp design for a number of different manufacturers. He is thoroughly familiar with the circuit design of NAD amp sections.

Regards,