Axiom Home Page Forums General Discussion Home Theater NAD T752 clipped - Is There A Problem?

My NAD T752 clipped a few days ago while watching a DVD at high volume (+5). It clipped right as an explosion began on the Attack of the Clones DVD. I suppose I don't find this too surprising considering the volume level but I can't help but wonder if this should not have happened at all.

My friend mentioned something about the resistance of cable and asked what gauge I was using. I don't know much about cabling and know little about how it can affect a system, all I can do is tell you what I am using.

The mains are wired with 8' runs of 14 gauge Kimber 4PR. The center is a 5'run of 12 gauge Monster Z1. The surrounds are 25' runs of Kimber Kwik-16. I am not using spades or bannana connectors....just using the bare wire at both ends.

From my understanding, the cables for the mains and center should be fine. However, I am not so sure about the surrounds. Should I have used a 14 or 12 gauge cable for a 25' run? Could the fact I am using 16 gauge cable for 25' runs to my surrounds actually cause my receiver to clip?

Any other ideas on possible things to check or eliminate?

Certain persons are going to laugh, but I don't think you've got enough power! The cable should be fine.

That receiver is designed to handle 8 and 4 ohm loads and it actually bench tests at 88w/channel with all channels driven through the entire frequency range. Who knows, maybe that is still not enough...maybe not at that volume level when a demanding dynamic (such as an explosion on a DVD) is encountered.

I can't help but wonder if the power supply is faulty or maybe there is a bad transistor.

Any T752 owners out there?

Are you running the speakers as large? Where's the cross to the sub?

Sorry, in real life I troubleshoot computers. It's instinct to ask stupid questions...

Did you try rebooting? Sorry, had to do it...like Ken I worked on a corporate help desk as an esculation for a very large financial/insurance company Have I missed what speakers you are using in your system? +5 Wow, with my Denon I would go deaf watching that movie, or my sub would knock me into the next room.

Yes, I am running all speakers as large and am not crossing anything over because I don't have a sub yet. Oh wow, I just realized I am sending everything to the center and surrounds. No wonder there wasn't enough dynamic headroom in the receiver to handle the afforementioned peak (explosion in the DVD).

Dunce Disclaimer:
I just got my Axioms last Friday and before that didn't even have a center channel. It's kind of funny as it is all coming back now. I did all the research about small/large and crossover settings when researching receivers 2 years ago. I guess I had forgotten all that until I read your second reply. (End dunce disclaimer)

I am going to set the center and surrounds to 'Small' and then set the crossover to 60hz. I will keep the mains set to 'Large' for the time being and will play with that setting once I get a sub. I imagine that will do the trick. If not, I will cross the receiver at 80hz and see what happens.

Thanks for your help.

Do you know which channel clipped ? My guess is that it's more likely the mains clipped not the center or surrounds.

If you don't have a sub you're probably better off with the current configuration, just turn the volume down a tich until you get a sub...

Hmmm..was just playing with the receivers settings. I thought I could set the mains to 'Large', the center and surrounds to 'Small' and the subwoofer to 'On' (even though there isn't one yet) and set the crossover to 60hz. I thought what this would in turn do is send everything to the mains, but only information above 60hz to the center and surrounds.

It seems that is not the case because I just tried that and there was a major lack of bass. The only way to get the missing bass back was to set the subwoofer back to 'Off'.
That just doesn't make any sense? Does a sub actually need to be plugged into the LFE of the receiver for it to work accordingly?

What about when the subwoofer option is set to 'Off' but yet the center and surrounds are set to 'Small'. What then controls the frequency at which the center and surrounds will be crossed at? Does the receiver have some sort of fixed setting it uses in that scenario?

I guess I still need some enlightenment.

Yes, the LFE is a discreet channel. If the receiver is told there is no LFE speaker (sub) to feed, it will (apparently) distribute the LFE signal to whatever speakers there are present (and probably set to large). I'm not sure exactly how this plays out, but that's what's going on. I agree with Bridgeman; turn it down a bit until you get the sub.

Mike, when you set sub "on" without a sub it sent bass out the sub output to the non-existent sub, the bass therefore being lost. This may or may not do anything with respect to the clipping you mentioned, but since the VP150 and QS8s roll off below 80-90Hz, they shouldn't be run "large". Set them "small", the crossover at 80Hz(the crossover doesn't apply only to the use of a sub; it can send bass to the mains) ; set M60s "large" and sub "off". The 752 will then redirect the VP150 and QS8 bass below 80Hz to the M60s, which can handle it much better, although not as well as a good sub.

do you use the soft clipping mode on your nad?im not sure exactly how it works but it is supposed to help(and i stress the word HELP) protect your speakers from damage when you run it at higher levels,especially the tweeters

Yes, it makes sense that if I turn the sub on and set the crossover to 40z that I will lose all bass below 40hz since I am not using a sub.

What puzzles me is what is supposed to happen when the sub is set to 'Off' and a speaker (whether it be mains, center, surrounds, a combination thereof, or all) is set to small. In this scenario what dictates the crossover point for any speaker set to small? I am guessing most lower to mid-range receivers use a fixed crossover point? Perhaps if I had a more expensiver receiver/sound processor, I would be able to individually control the point at which my center and surrounds are crossed when they are set to small? I am only guessing at this point.

In any event, I tried the same DVD explosion scene at +5 with the mains set to large and the center and surrounds set to small (subwoofer off) and it did not clip.

To be honest, I prefer the sound of everything set to large (more bass sent to center and surrounds) and may use this setting for normal listening. I suppose if I ever want to show off my system by cranking some reference scene, I should probably set the center and surrounds back to small while I do that. Ummm...not that I ever plan on showing off at all...um...er..(clears throat).

I am having two guys over from work sometime next week. One owns a PSB Image series system and the other is saving up for a Def Tech system. Both are rather curious to hear Axioms. Even though they sound amazing right now, I will be sure to get them exactly dialed in with a sound meter....I have yet to do that.

>>What puzzles me is what is supposed to happen when the sub is set to 'Off' and a speaker (whether it be mains, center, surrounds, a combination thereof, or all) is set to small. In this scenario what dictates the crossover point for any speaker set to small?

If Sub is set to Off, Mains are set to Large, and anything else is set to Small the bass from the Small speakers will normally be fed to the mains. HK is the exception here, it only feeds bass from center & surrounds to Sub.

If Sub is set to On, of course, all the bass gets sent to the sub instead.

Most receivers let you set the crossover frequency from a short list of preset values (eg. 60, 80, 100, 120, 160, 200) but you have to use the same crossover frequency for mains, center and surrounds. Again the HK is an exception, it lets you pick different crossover frequencies for each speaker set.

>>To be honest, I prefer the sound of everything set to large (more bass sent to center and surrounds) and may use this setting for normal listening. I suppose if I ever want to show off my system by cranking some reference scene, I should probably set the center and surrounds back to small while I do that. Ummm...not that I ever plan on showing off at all...um...er..(clears throat).

I think we all strongly recommend setting everything to large and turning the volume down a bit if needed. If you want to show off, have your buddy with the PSB system bring his sub and you buy the beer.