General Help, Suggestions, Advice, Discussion

Posted by: CLo

General Help, Suggestions, Advice, Discussion - 02/17/15 10:26 AM

Hi all,

I've been reading posts around the web lately, trying to gather information on possibilities for my home system. It has sort of morphed into an unorthodox set up so am trying to find some creative solutions.

Back in 2006 I ventured into the Axiom world with a nice treat for myself. 4 M80v2s, 1 VP-150, and an EP-350. They are running off a Denon AVR-4306 right now and I have been extremely happy with the purchase since. In the back of my mind I have always been curious about the side effects of running 4 ohm speakers on a receiver specified for 8 ohms, but have seen no issues yet, and I have cranked it quite a few times over the years.

This is where it gets more interesting. I recently came across someone who inherited an Axiom set and just wanted to get rid of it quite cheaply. So I now additionally own more Axiom equipment: 2 M80Tis, 4 QS-8s, and another VP-150. The speakers are in fantastic condition but the grills are a little banged up but not enough to pass on them.

So, this is where I am trying to gather information. One problem I have is placement of all these speakers. I live in a NYC apartment, so space is limited but it's not a shoebox. I think over time I will figure out where to mount and place these speakers. But the larger issue I am trying to sort out is how to power these speakers. One Denon AVR-4306 obviously won't cut it so am now considering dedicated amplifiers, but have never been down that road before. Having these speakers that can handle up to 400 watts each, what kind of powering options should I be considering? I notice that Axiom offers an amplifier. Are these good, other brands to consider? Even the Denon claims 130 watts x 7 into 8 ohms, but what am I really supplying to my speakers now by comparision. Boiled down, what power options should I be thinking about, considering, weighing, reading about?

Any suggestions, thoughts, ideas, and general discussion points are warmly welcomed. Thanks in advance even if you have read this far. :-)

Summary:
M80 v2 4x
M80Ti 2x
QS-8 4x
VP-150 2x

Frank
Posted by: J. B.

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 11:56 AM

one option for amps that will give you the same quality you're enjoying now but at a much more interesting price (than audiophile amps) might be pro-amps from Crown Audio or QSC or others.

to get an idea about that, pls see "My HT room" in my sig.

total power in my system is about 8000 Watts (same as my winter baseboard heaters' total).
it means it just loafs along and is ready to reproduce the highest instantaneous peaks without a hint of distortion.

pro-amps usually don't need flat fr.resp. below about 32 Hz, so some of them filter it off. if you need an amp to reproduce those, check closely on the specs before you buy.

in closing, my qsc amps carry a 6 year warranty. :-)

hope this helps.
Posted by: CLo

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 12:32 PM

J.B. - Thanks for the response.

Quick first question. You have the QSC PLX3602 running your 2 M80s, correct. The specification for that amp states 1250W per channel @ 4 ohms if I am reading that correctly. And the M80s max power is 400W. What am I missing? Shouldn't this blow out your speakers?
Posted by: J. B.

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 12:53 PM

at first, i wanted to buy a third QSC-GX5, but saw the PLX-3602 at half price, so i bought it.

too much power is "spare power"; mainly for peaks.
as long as you don't hear distortion from the speakers, then all's right.

a better and much faster way to blow out M80's is by using a 50 Watt amp and turning the vol. control to the max.

most of the time, i use less than 10 Watts total,
but i've also used around 2000 Watts a few times when playing high peaks in a very loud passage.
it never sounds like 2000 Watts, because it lasts for such a short moment in time that you don't notice it. this ability for fast peaks is what makes for a very realistic reproduction.
i always listen to music and most movies at "live level"; this demands another type of audio system compared to someone who only wants "background music".

spare power is like a car: you might only need 50 hp to cruise on the highway, but what about passing? this is when you need spare power.


hope it helps. others should be able to give you a better answer.
Posted by: CLo

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 01:09 PM

The analogy sort of makes sense to me but when I compare 400 watt max on the M80 and 1250 watt on the QSC PLX3602, some part of my brain says, "that's not good". :-)

I'll keep reading. I'd like to understand why/how that much spare power is okay.

Thanks again.
Posted by: CLo

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 01:20 PM

Another quick question about using pro-amplifiers. How do you handle the inputs to the amplifier? I see most of them have XLR inputs.
Posted by: J. B.

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 01:31 PM

Originally Posted By: CLo
Another quick question about using pro-amplifiers. How do you handle the inputs to the amplifier? I see most of them have XLR inputs.


i bought cables with RCA on one end and XLR at the other end.
Posted by: CLo

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 04:13 PM

Any experience with ground loop issues? I notice posts complaining about humming and buzzing noises.
Posted by: J. B.

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 05:22 PM

the only noise i hear, with 3 amp fans running, is when everything is quiet then i hear them quite weakly, but the instant there's a sound through the speakers, the noise disappears.

i consider myself lucky because since the 70s when i got an audio system, i never had any hum problem (and no buzzes).
Posted by: MatManhasgone

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 09:04 PM

Originally Posted By: CLo
Having these speakers that can handle up to 400 watts each, what kind of powering options should I be considering? I notice that Axiom offers an amplifier. Are these good, other brands to consider? Even the Denon claims 130 watts x 7 into 8 ohms, but what am I really supplying to my speakers now by comparision. Boiled down, what power options should I be thinking about, considering, weighing, reading about?


The sad side to Wattage in relation to speakers is that it's not all equal. Ohms law says that W = V * A. So on many of the lower end systems they can juice up the Voltage and get away with close to no Amps to give a very nice Watt's number. Will the speakers work well? No.

I have an Anthem MCA5 that tips the scales at 57lbs and does a reasonable job at powering my speakers. (150w x 5 channels) and all it does it amplify. Your Denon tips the scales at 40lbs and says it can do 130w x 7 channels and has all the other DAC's and components inside. Something doesn't balance out here?

Your question however is what does it need to drive these speakers well? I'd say about 45w of true clean power each channel. The challenge however is to figure out who is selling you smoke, and who is actually delivering you the real thing.

I was shown that numbers don't matter when I first got into audio and went to the big audio shop in Toronto, and they had a 30w Cambridge Audio receiver setup beside a 200w Sony. The Cambridge sounded way better and actually felt louder than the Sony. It also weighed 3 times as much.

You really need to look into the actual spec's of anything that you buy. What is the size of the main capacitor? How much headroom does it have? What is the current pull on the unit?

Now your receiver does at least have Pre-Out's so you can hook up an external amp to the unit. If I were you, I'd skip trying to buy new as your just paying upfront for the depreciation for the next person who owns it. I'd look as to what is availible on the used market at http://www.usaudiomart.com/ and save yourself some coin in the process.
Posted by: CLo

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 10:38 PM

Thanks Matt.

I'm sure the answer is not a short one but how do I sort through these endless amplifier choices and find "true clean power". I figure there has to be method to comparing amps. For starters, like the suggestion above, how do I assess the "cleanness" of the QSC-GX5. The stats look pretty impressive to me but what am I missing? I'm a very scientific person so I'm convinced there is a way to get make a better comparison.
Posted by: JohnK

Re: General Help, Suggestions, Advice, Discussion - 02/17/15 11:11 PM

Frank, my thought is that you have to determine the setup for all those speakers(which you now say that you'll do "over time")before you can intelligently analyze powering them. The 4306 may or may not be fully capable of the job.

Keep in mind that regardless of the maximum power capability of an amplifier, with speakers of average sensitivity such as the Axioms about 1 watt per speaker is used at a comfortably loud average level at the listening position in the mid 80s of decibels. Brief peaks use much more, of course, but at safe(to your hearing)levels receivers anywhere in the 100-150 watt area are capable of handling such brief peaks. Unused amplifier headroom is simply that: unused.
Posted by: J. B.

Re: General Help, Suggestions, Advice, Discussion - 02/19/15 07:29 AM

mistake...
Posted by: chesseroo

Re: General Help, Suggestions, Advice, Discussion - 02/19/15 05:26 PM

Originally Posted By: CLo
Thanks Matt.

I'm sure the answer is not a short one but how do I sort through these endless amplifier choices and find "true clean power". I figure there has to be method to comparing amps. For starters, like the suggestion above, how do I assess the "cleanness" of the QSC-GX5. The stats look pretty impressive to me but what am I missing? I'm a very scientific person so I'm convinced there is a way to get make a better comparison.

Clo, being a scientist myself, i tried some instantaneous A/B switching comparisons between a few receivers and amps (including a tube amp) years ago. This was the most objective way to hear for myself any significant differences among these amp units.
Final conclusion was that if any audible differences exist, they could not be reliably detected.

Specs will certainly help with some comparisons such as max. power output, ohm rating, etc., however as JohnK often points out, an amp should not impart any sound quality that differs from the source. They should only reproduce and amplify the sound signal exactly as it is received. Most competently built amps will do just that.

The concept of 'clean' sound relates more to the subjective reasoning provided by those who judge with their eyes (whether they know it or not).
Posted by: AAAA

Re: General Help, Suggestions, Advice, Discussion - 02/19/15 08:16 PM

I'm with Matt. Use preouts and buy some decent amplification. right now is not the best time to pull the trigger on a new AVR. Unless you dont obsess over the minute details that some of us do..... wink

The whole Watts spec and quoting Ohms law is not meaningful. These equations are theoretical and are only valid into purely resistive loads. Ie. Voltage and current are in phase. The exact opposite of a loudspeaker over its range.

The best explanation to sum it up in plain language came from a podcast with Laurie Fincham. To parhrase: "We concern ourselves with watts but this is not important at all. Amplifiers are a voltage supply device. We need to find out if a given amplifier is stable into a variable load at the required voltage. Then we must confirm there is no sag in voltage or current during impedance swings during program material." There is no one spec that determines this in a user manual. The best specs are checking for double down and if the manufacturer gives an all ch driven 20-20 output figure at 1% distortion. Most dont and cant deliver respectable numbers if so.

I also agree that Cambridge units sound fantastic, but I found out their reliability and firmware is problematic. I was so close to buying a 650R. I own another quirky British unit and it was a major upgrade over my previous Pioneer. Even at a quoted 50wpc less.....
Posted by: MatManhasgone

Re: General Help, Suggestions, Advice, Discussion - 02/19/15 11:16 PM

Originally Posted By: Serenity_Now
The whole Watts spec and quoting Ohms law is not meaningful. These equations are theoretical and are only valid into purely resistive loads. Ie. Voltage and current are in phase. The exact opposite of a loudspeaker over its range.


I will disagree based on my experience of how speakers work. They are basically a set of electromagnets with a cone attached to one end. Your speaker driver uses the coil inside to either attract or repel from the fixed magnet at the base of the speaker. The effectiveness of the speaker to reproduce the sounds you want is controlled by how well the coil can react to the changes in direction to overcome it's own velocity to reproduce the sound wave.

I personally found that a high current amp seems to produce a more pleasing sound for my listening than one that is based on high voltage (with similar wattage output)

For whatever reason, my 15 year old Nakamichi AV1 sounds far better and reproduces music acoustically cleaner than my new Pioneer Elite SC1227 that is a higher wattage and supposedly high current, but is a D-class amp. The pioneer seems to give music an empty feeling to me depending on the passage of music at a given time.

Your receiver does have pre-out's so you can hook up an external amp if you find your receiver isn't giving you the sound quality that you are wanting. I'd try using a different amp to improve the sound as the speakers are very capable to reproduce music.
Posted by: AAAA

Re: General Help, Suggestions, Advice, Discussion - 02/20/15 04:56 AM

Yeah, thats how a speaker physically works, but not the circuit of a speaker. You forgot the crossover network. Load impedance varies with frequency. Speakers are a reactive load, like a motor. Higher voltage by default means higher current. Its if the Amp is up to the task or not. Some units have current limiting power supplies.

I think we agree, and are just using different terms. smile