Bass leaves after amp warms up?

Ralph, Al, and Mr. Fishing..., just trying to be a detective, if this problem has occurred with other integrateds/amps, do we know if they use mosfets. If not, and all the amps pucker out with bass, what else is left to check.

I've been harping about the PSB's low impedance specs affecting the MF and whether Zeros might help. The only practical way to check is for Mr. Fishing to borrow, if at all possible, another set of "normal" speakers and see what happens. If all is good, the culpret has been identified -- it's the PSB speakers. I highly recommend this reality check.

If not, it's either the amp, notwithstanding that Mr. Fishing thinks its ok, then the cables, and if cables are ok, then lastly, he should rule out para-normal poltergiest activities. By any chance do we know if Mr. Fishing ever visited Amityville, CT (??). I understand that modern day ghosts are quite mobil.

:>')

BIF

Beating my own dead horse here, but I suggested it 200 or so postings ago and it could still be a piece of the puzzle. It goes with what Jjrenman said above about listening fatigue. This problem (especially if the OP's system sounds at all fatiguing) could be entirely explained by the acoustic reflex--the natural reflex our bodies have to surprising, loud, or unpleasant sounds that mechanically diminishes the conduction of sound to our inner ear. I'll quote from Tyll's "Loud Music Sucks" article on Innerfidelity:

"Your listening system has built in protection from loud noise called the acoustic reflex (also called the stapedius reflex). When you are exposed to loud sounds, small muscles (stapedius and tensor tympani) in your middle ear tense to increase the mechanical impedance of the system of small bones (oscicles) that move vibrations from your eardrum to your inner ear. The net result is a reduction in amplitude of sound being transmitted into the inner ear of up to 20dB at low frequencies, with less attenuation as frequency rises up to about 2kHz where no attenuation is seen."

Please note that he also hypothesizes that the acoustic reflex is why so many people describe show systems as bright--their bodies are mechanically filtering the bass out of the (too loud) sound.

http://www.innerfidelity.com/content/loud-music-sucks

20 dB is a HUGE difference in the bass and having this happen would absolutely result in a perceived loss of bass impact but would NOT mean anything is wrong with your hearing. On the contrary, this would mean your body is responding as it should to loud sounds. Apart from measuring LF test tones, this is also where an SPL meter comes in handy. You say you listen at low volumes, but low for me is 50-60 dB with 80-85 dB my max. For others 80 dB might feel like a starting point. As I said before, I can feel and hear my own acoustic reflex kick in at volumes as low as 60 dB if I find the sound of the system (or natural sounds around me) unpleasant. If your SPL meter shows an objective reduction in bass output, I will gladly cheer on an appropriate resolution to your problem. However, if the SPL meter shows the bass is still there but you're not hearing it, the acoustic reflex is on the table.

You have great equipment which I'm sure sounds very good, but certain components have been accused of brightness and in combination (at whatever volume) could be making you subconsciously cringe as this reflex kicks in. Again, Fishing716, I'm not saying it's all in your head or that there's anything wrong with your hearing--just that there is a possible explanation outside of swapping gear. And if it IS the acoustic reflex, you might start looking for gear that sounds less fatiguing.

One more idea: your hearing might be exceptionally good. The PSB Synchrony models have an unusually low spike at the tweeter's resonant frequency, around 16-18 kHz (or maybe this is simply a spike in the treble apart from the resonant frequency). It's possible that (like me) you're still young enough that your hearing extends up this high and you're bothered by the spike, finding the sound fatiguing. From JA's review of the Synchrony One:

"The top octaves sounded smooth to me on this Telarc SACD—the delicately brushed triangle at the end of the final variation before the fugue was beautifully resolved, without sounding spotlit—but Erick Lichte was less tolerant than I of the PSB's performance in this region. However, in the "Measurements" sidebar accompanying this review, I wonder if he was reacting instead to the small response peak between 16 and 18kHz, which, unlike me, he could hear."

http://www.stereophile.com/content/psb-synchrony-one-loudspeaker-measurements

This could create listening fatigue for you and possibly (my dead horse takes a further beating) trigger the acoustic reflex--further creating a perceived tipped-up tonal balance.

Amityville Is in NY not CT
I've been there

Hah. Problem solved!! I was right. Mr. Fishing.. confirmed it -- ghosts. Your system needs an exorcism. I'm running a 2 for 1 special this week. Send me an e mail and we'll discuss the pricing. So is Amityville on Long Island?