Axioms in Place - Question About Hiss in Surrounds

Hey guys..

Well everything is placed and switched out but have a problem I need addressing..

I originally purchased an Onkyo HTS-760 HTIB last November. Once I got my new Axioms in (M60's,VP150 and QS8's) I went back to my 3 year old Onkyo TX-DS747 5.1 receiver since I was going to sell the HTIB just like I bought it.

Here are the output specs on the older Onkyo:

Front/Center 80 watts/per channel and Surrounds 40 watts/channel

My concern before I bought the Axioms was that the old Onkyo's surround output was not going to be enough to drive the rears. I think I was right.

With the volume at 13db under reference (this is approx. the level I watch a DVD) I am getting a audible "hiss" coming from both of the QS8's during quiet scenes. I can hear it sitting in my normal listening area about 10 feet away.

The Onkyo states on the back a 6 ohm minimum speaker so I don't think that's the problem.

My question is in your opinion is the hiss coming from not having enough power supplied to the rears?

Looks like I may have to get a newer Onkyo unit with more wattage for the rears..

Thanks for any info you can supply regarding this..

Loving my Axioms so far though!

Rick

Rick, i doubt power is a problem here. It certainly has nothing to do with "dirty power" like was suggested by sutter over at the Spot. That is all marketing jargon reiterated.
When you balanced your speakers for SPL, were the surround signals jacked up at all?
How far away are the speaker runs and what gauge cable are you using?
Have you tried swapping out for your other receiver unit to see if that also produces the sound?
Have tried different cds, dvds?
Hopefully someone else can chime in. I'm short on time today.

Someone posted a link here not too long ago where refurbed Onkyo 2 channel receivers were sold at $99 each. I believe they were 100 wpc (model 211???). Would certainly be a cheap remedy (assuming your connections and settings are currently correct and the problem is your receiver's lack of power).
BTW, how long are the wires running to your surrounds and what gauge is that wire?

Chesseroo,

I am glad to hear you don't think it's a power problem. I really can't afford a new receiver right now.
I am at work right now so I can't remember the exact numbers regarding what level adjustment I had to do on the surrounds when calibrating but will check once I get home and report in.

The Onkyo receiver that came with the HTIB setup is listed as 100 watts/channel but states a minimum of 8 ohm speakers so I was was afraid to even try it since the VP150 and QS8's are 6 ohms. I don't really understand the ohm thing enough so I wasn't going to chance it.

I am using 12 gauge wire for all my hookups. Wiring is screwed under the post connections on both ends - no banana plugs yet but am considering it for ease of connecting/disconnecting. The run to the left surround is 30 feet and the run to the right one is 50 feet.

It was late last night when I got everything finally connected and didn't have a lot of time to try other sources or discs. I will do that later tonight.

Thanks guys and will report back tonight with further info..

Rick

It could be a ground loop problem. Try using a "cheater plug" on your receiver's power cord.

Wouldn't a ground-loop problem cause a hum? And wouldn't it be coming from all his speakers - not just the surrounds?

Rick, I'd try that other receiver in there, too.

Hiss and not hum? I've got a B&K Ref 31 - a nice preamp - and I have a low hiss that you can only hear when you move up close to the speaker. Some of what you are hearing may be the noise floor of the Onkyo receiver - although hearing it from 10 feet away is not right.

I read recently that "hum" is a ground loop situation where "hiss" is an EMI/RFI problem. Do you have a power cable running parallel to your surround speaker wire at any point? Someone else may want to chime in as to the causes and solutions of EMI/RFI in a system. Like I said, some of what you're hearing is noise floor, and some of it is the inherent nature of the rats nest of audio interconnects, speaker cable and power cable running behind your system.

Hi Rick and all,

Ground loops produce low-frequency hum at 60 Hz or 120 Hz. Hiss sounds like pink noise at low levels. I think you may have a level adjustment problem with the surrounds, although I should point out that on older surround receivers, many manufacturers used to use lower-quality amps for the surround channels as a cost-cutting measure. Some of those could be noisy. This was true in the early days of analog Pro Logic receivers, before Dolby Digital 5.1 became a standard. It has nothing to do with the impedance of the speakers.

In a well designed preamp/amp, thermal transistor noise (hiss) should not be audible unless the volume control is set very high and you are standing fairly close to the speakers.

Preamps with extra stages of amplfication (magnetic phono, or moving-coil phono) may have audible background hiss at normal listening levels if it's a cheaply designed phono stage.

Regards,

Is your receiver a Dolby Pro Logic or PLII? I had the same problem with my 1991 Vintage Technics SA-G710. The surround channels were actually 60W instead of the 130W/C for the mains. I noticed that the sound quality in the surround channels was not the same as the mains and there was hiss when no input source was selected. In contrast, I could turn the volume all the way up and hear nothing but silence from the mains.

Sean

In reply to:
Wouldn't a ground-loop problem cause a hum?

Hiss, hum, some of the speakers, all of the speakers....whatever. I don't know and frankly wouldn't care as long as it fixed the problem. The point is that it couldn't hurt to try. If it works it would be a cheap fix and if it doesn't work he is only out the 59 cents it cost to try.

ground loop would cause a 60hz hum. 60hz is the rate that AC "switches" so thats why its that.

The hiss your experiencing sounds like just plain fact that your reciever isint a top of the line model and its got some hiss noise. As alan stated, most good amps and preamps wont have this, unless you put your ear literally right up to a tweeter for example. I had a hiss which was audible in my old cheap reciever, its a way of life.

I dont see any reason whatsoever why your cables and their lengths etc would be causing this, but i would also think that you would be hearing the hiss from all of the channels if it were as bad as it sounds. Good speakers will reveal lesser equipment upstream, lesser media for that matter too. Ive been noticing distortion in movie soundtracks which is somewhat annoying.

In reply to:
I've been noticing distortion in movie soundtracks which is somewhat annoying.

We watched a movie last night and I noticed distortion in the center speaker. This was a scene where a lot of police cars came in with the sirens wailing. My wife didn't notice it but I sure did.

The only level adjustment I made during calibration on my speakers were Front Right +2db, Left Rear -4db and the sub I dropped to -6db per instructions that came with my SVS.

I do remember when I was calibrating and had my master volume at +13db on the readout (this was 75db on my SPL using DVE) I had a very bad hissing noise in the rears that sounded like a VERY large snake. I mean it was almost overbearing which I know affected the calibration levels of the other speakers since it was so loud.

I think I just have a noisy/underpowered amp that needs to be replaced.

Thanks guys for all your suggestions and help. Guess it's time to spend another $500 for a newer Onkyo 601.

Rick