What's My Problem?


OK, here's the situation . . . . hoping some of you with more knowledge and experience than I have can help me out.

On 2-channel listening, my system sounds great at low levels -- say at 9 o'clock or less on my VPC-1 passive preamp volume. Lots of openness and air, good imaging, lots of space around instruments. Of course, dynamics and bass suffer, but that's to be expected.

Between 9 and 12, the sound starts to get harsher and the soundstage begins to close up -- orchestral stuff sounds much more confused and congested. Above 12 o'clock, it's really not worth listening to.

These aren't very high levels -- 9 o'clock is my "late night with the wife sleeping down the hall" listening level, and 12 o'clock doesn't get Verdi's "Requiem" to real-life SPLs.

My first assumption is that my amplifier just doesn't have enough juice. But the RB981 puts about 200 wpc into a 4 ohm load, and I would think that would be enough to get to at least decent levels, even with my admittedly power-hungry NHT 2.3As . . . .

Alternately, I thought that maybe the 9000ES/RB981 combo wasn't ideally suited for a passive preamp. I understand that component matching is critical here, but I'm not really clear on how it works . . . . the volume gets loud enough with no problem, it's just that the quality suffers.

Then again, it could simply be "louder=more annoyance from digital harshness," and I need to replace the 9000ES with a better Redbook CDP. But it seems to me that if the CDP was to blame, the soundstage and "airy-ness" wouldn't change much as the volume increased.

Suggestions would be greatly appreciated!

Thanks!

Pat
tsrart
Pat, It sounds to me that you have what's called plain ole amp clipping. Your amp is 200 watts per channel into 4 ohms. That's really not that much if your speakers crave power, as you say yours do. You realy want to consider the ratio of output powers when comparing amplifier power ratings. What you should be concerned about is your dBW level. Just because your 8 ohm amp (probably 100 watts per channel, right?) can give you 200 into 4, doesn't mean anything as far as your db level. You're probably getting less than you think db wise. I'm not familiar with your speakers, but I, too, have hungry speakers. (Revel M20s) Although I can go to 2 o'clock and I still don't clip. But then, again, I'm using a YBA Passion Integre, if that means anything. You probably will do better with 200 watts per channel into 8 ohms. Big decision: change the amp or the speakers. happy hunting. warren
believe it or not but it clips! don't pay too much attention to power ratings since measuring an accurate power ratings consumes too much time for the cheapo amp.
Two possibilities occur to me. The first, and I think the mostly likely, is that you simply are up against the limits of your speakers. My experience is that NHTs do get harsh and ugly as they get louder. Many less expensive (and some more expensive) speakers are like this, a notable exception on the inexpensive end being the Paradigm Reference range which usually sounds better as it gets cranking.

A second is that you are experiencing hearing loss, a sometime consequence of which is the development of rising levels of perceived distortion as SPLs increase. This would require evaluation by an audiologist but it is a very real and well documented phenomenon.

Let's hope it is the former, or one of the other possibilities identified above.

will
What is the output impedance and level of output of your source(probably not the problem, don't sweat it if it's not handy)? What type of cables are using and how long are they? What is the input impedance and sensitivity of your amp? What is the sensitivity of your speakers? What is the volume of space of your room and what is it's construction like? Is it "leaky"? It could be poor system synergy, inadequate system for your desires, or a faulty piece (volume pot?).
Hey Tsrart,

I agree, it is the amp that's coming up short. The Rotel RB-981 (130w @ 8ohms) is a fine amp but, most truly muscular amps will double their power at 4 ohms. You are only getting an additional 70wpc at 4 ohms, that's not enough. I had a similar situation when I owned a Krell KAV-500 and a pair of Revel M-20. The Krell, in its time, was considered a brawny amp at 100 wpc and a substantial toroidal transformer. The Revels are, as Warrenh mentioned above, a rather power hungry speaker, 86 db at 4 ohms. At moderate levels the sound was fine but, if I tried to crank it, the soundstage would begin to muddle and then collapse completely. I upgraded to a Plinius SA-250MkIV, a bit of overkill, but I did not want to have to upgrade my amp again and I believe, with this amp, I have accomplished my goal. For you, this may be a little more then you will want to get into but there are other excellent sounding amps with the power to handle your situation. It's also important to understand that not all 130 wpc amps are created equal. As I mentioned above, there are amps that will double down a 4 ohms. So you may want to look for an amp in that power range that will double down, that will should do the trick. I think you would be headed in the right direction if you were to consider an amp upgrade and it might not be as expensive as you might think. Good luck and happy hunting......John