Bass leaves after amp warms up?

All amps are no perfectly efficient and produce heat as a result. If the heat produced is not dissipated and temperatures rise to much accordingly, I would expect sound quality can be affected.

CAn't say why this might be occurring in the OPs case, but better ventilation around the amp, maybe even use of external fans, might help.

Based on specs the amp should be largely up to the task of driving the PSBs, but driving most speakers to very high volumes might tax most any smaller integrated amp I have seen to some extent.

I had a Musical Fidelity A3CR power amp that I believe was heavily biased to Class A and was of modest size yet quite heavy and tended to run quite hot accordingly. Might be a similar case here. I moved to a very efficient Class D amp that never breaks a sweat regardless of volume with my lesser efficient OHM speakers. Bass and dynamics is never an issue these days at any volume.

One red flag I see that might help account for what the OP hears is that his PSB speakers show 4 ohm nominal impedance and the MF amp specs indicate power into 8 ohms only. Together, that might account for what the OP hears. Amp specs or bench measurements in a case involving a 4 ohm nominal impedance load would be more informative.

BTW those PSBs are one of my favorite speakers.

I have heard them run quite nicely in a smaller room and at fulfilling volume off of 80-100 W Rogue tube amp or slightly higher powered Rowland Class D amp.

I did not notice any dynamic compression at the time I heard, however audition was limited.

I would be wary of most any smaller integrated to match this performance though. Tight physical proximity of power amp and pre-amp in the same box creates real limits on what can be achieved compared to separates.

I would want to run those PSBs of the best and beefiest standalone amp I could find if it were me, to help assure OPTIMAL, not just good performance.

Hmm, why could it not be both amps tried are being overdriven driving the 4 ohm PSBs to the user's satisfaction, especially if listening at very high volumes, and performance deteriorates over time accordingly?

Which Bryston amp was used specifically? Were the limitations over time as pronounced as with the MF integrated? Does the problem mostly occur when listening at higher volume?

Good call. Bad connections happen and could easily produce the effects observed.

If the problem occurs at lower volumes as well as high, that would better indicate that temperature inside amp over time when driving speaker load is not a factor as well.

I am finding my Icepower Class D amps by far are less subject to dynamic compression at high volumes than any other SS amp I have used in recent years, including 360 w/ch Carver, 180 w/ch Tube Audio Design (I still own and use this and have a/b compared to Class D Bel CAnto), and 120 w/ch Musical FIdelity A3CR.

Only with the BC ref1000m Class D amps (500w/ch) does the volume continue to go up proportionally to raising the volume and the music continue to expand without compressing at some point prior to target lifelike volume levels.

The Class D amps seem to perform more like tube amps in their ability to go louder and louder without compression and fatigue, an attribute often attributed mainly to tube amps otherwise.

The 180w/ch TAD Hibachis (same ballpark power-wise as OPS MF I would sy) are lovely sounding amps even at fairly decent volume, but they do run out of gas sooner and at a point that some who like to listen loud and clear might find deficient.

Fishing, also I am still wondering if volume of listening is a factor. How loud do/can you listen? Does the problem occur mostly at lower volume or high, or does volume not matter, same results?

If associated with lower volumes as well as high, a connection issue becomes more likely. COuld be a power cord conenction even as Kijanki suggests.

As you describe it, I would expect teh problem to be most noticeable at higher volumes where bass "pressurizes" the room more normally, but if clearly noticeable at lower volumes still, amps ability to drive the speakers optimally may not be the prime issue to address first and then see.

" I never ever listen to music loud"

Good to know. Its probably not the amp then.

I have seen cases where old switches in pre-amps or other gear cause a very significant loss of power over time as they oxidize, etc., and good contacts are lost. Same true with volume controls, balance controls, etc.

If there are any manual switches in play with your gear, next time you hear it, try twidling with controls and switches and listen for any differences. THe twidlling alone might help but if so a good cleaning is probably in order.

This happens with my old NAD 7020 receiver from 30 years ago that I still use. A few twiddles with the input switch on occasion when I notice things have faded out sets things right again until thenext cleaning of switches and controls. Not an uncommon thing...

If changing source impfoves thingx temporarily, its possible the source
selector switch on the amp has a problem. Could be dirty or defective.

Ops comment tnat hs is not listening at hign volume would seem to work
against the amp not being abl to drive the speakers well theory, as well as
swirching sources making a temporary difference. Having tne same
problem with two different amps could point to both being underpowered
and heating up over time and negatively affecting sound.

Acoustic reflex seems like a natural defense system against what I have read where 80-85 db is the general limit for safe listening without causing damage to hearing.

It is very possible that when sound seems to change systematically over time, at least part of it is due to our hearing senses adapting or changing as needed.

We tend to think of many things like this as a constant, but no doubt people react differently to things at different times. WHy would hearing be any different?

Thanks to the PSB owner for chiming in. I do not doubt both amps used are underpowered to drive the nominal 4 ohm load. Whether that accounts for all that is being heard is a different story.

One might think any 200 w/ch amp is up to the task of driving most any speaker optimally (not just well). One would be wrong. I've had 360 w/ch and 180 w/ch amps that cannot.

The current delivery and ability to double down at 4 ohms matters. If the OPs MF amp could do that, it would likely warrant being in the published specs. That and being a conventional Class A/B type integrated, which most always has physical constraints that limit what can be done with power supply in close proximity to pre-amp circuitry, I am very confident that it does not.

I'm not sure that an issue with eletrical power supply would be consistent with the pattern OP describes for sound deteriorating over time.

The amp would appear to NOT be up to the task of driver the PSBs OPTIMALLY given its bench measurements Al identified. That is a clear issue that would account for deficiencies in bass and dynamics.

Find an amp to try that doubles down mostly from 8 to 4 ohms. You might not even need more than 100-200 w/ch to do a good job assuming you do not listen at high volumes. If you do, then throw the kitchen sink at those puppies. Modern Class D amps make it more practical than ever to do this when needed.

Check power rating into 4 ohms to see if double or close to double from 8 ohm. That is a good indicator. Published bench measurements in reviews to confirm is best to be sure.

I could recommend some to try as could others I am sure if a price point were known?

"I just got off the phone with Musical Fidelity..
I was assured the M6i is more than capable of handling PSB Synchrony one speakers."

This is a subjective statement. Most listeners out there might be more than satisfied. There is no reason for MF to say otherwise. But there are doubts based on published specs and bench measurements that should matter to a very discriminating listener, which OP appears to be. So there is a CLEAR red flag worth consideration.

I've heard the PSBs sound very good off 100w/ch Rowland Class D switching amp. That would be a good place to start as a reference. I truly believe a good modern Class D amp with good power supply that can mostly double down to 4 ohms can solve OPs problem in a relatively inexpensive and very compact package.

Rowland 100 w amp for reference.

There are many well received integrateds out there these days that use CLass D amplifiers, even inexpensive Japanese ones from companies like Onkyo. Quality of power supply, which matters might vary widely with an integrated more so than separates. If the specs indicate mostly doubling down to 4 ohm, it is probably worth consideration. There are still limitations with amp and pre-amp in close proximity in same box with Class D, but technical aspects relating to noise and shielding are different. I have not used Class D integrateds so cannot vouch, but many have received good reviews and acceptance. To be safe, I'd say separates are better (and with Class D amps smaller as well). But why not try a well reviewed integrated for reasonable cost first and see? If it does not work out then move on eot separates. I think there is a decent chance the right integrated could work for OP.

Amp could be defective.

Not likely though that two amps would have the same inherent defect though.

Switching source has an effect I recall. COuld be defective source control switch. COuld be defective volume control if volume is adjusted at all in test cases.

Fishing,

Any difference at all in when the problem occurs between old amp and new? If so, equating the two to produce exactly the same problem may be confusing the issue.

My guess at this point is it is some combination of these that is causing the problem.

1) defect in the amp that affects performance over time
2) amp is having problem with speaker load
3) patterns of human hearing as identified above.

Trying a different amp that is up to the task on paper or better as measured on the bench would address both 1 and 2.

Not much one can do about 3 except be aware when doing listening tests.

You might also try a different pair of easy to drive speakers as a test and see what happens there.

Do you have any other speakers around? What happens with them? Results would help determine if speaker/amp match or defect in amp is an issue.

FIsh,

It is what it is but for future reference, its not a bad idea to always keep a spare component around to switch in as needed to help diagnose a problem or even to pinch hit when a starter piece goes down.

For testing purposes, an inexpensive receiver or integrated with preamp outputs and amp inputs can be used to replace another integrated, power amp, or pre-amp when needed. Cheap spare CD players are readily available these days, just check out the local Goodwill store. Cheap spare speakers can be had easily off Ebay, as can most home audio components.

This way you can do "regression tests" to help isolate a problem to a specific component when needed.

Subwoofer would be a band aid.

BEtter to get to the root of the problem and fix it. The PSBs should leave nothing to want if set up well.

IF either speaker alone sounds better, that would seem to indicate the problem is not in either speaker, like detached/loose voice coil or something like that.

Have amps always had this issue? DId any work good initially at least for some time before the pattern started? ANy nasty sound accidents prior, like loud feedback due to improper connection, or anything else similarly abnormal?

So with one speaker, it took twice as long to show the problem? I'd say that is consistent with the amp running too hot theory. That would assume the amp still got too hot inside but took a fair amount longer to do so due to approximately half the heat being generated as prior, assuming bogh channels running similarly.

I'd really like to know what happens with cover off and/or better ventilation.

If the problem occurs in both speakers at same time when it occurs and does not with one, that would tend to indicate that amp/switch/control defect is less likely, but still possible. Definitely supports the amp is overworked due to load and getting too hot theory.

BTW testing with just one speaker in lieu of others to test with was a good call! Gotta remember that one.

Can you take the cover off and test as Al suggested?

If that helps, a good external + quiet cooling fan might help. Or if you have any fan that could be applied, just try that. ANything to help lower the internal temperature and see what happens.

BTW, if you can prove via testing that cooling the amp helps the sound quality, that would add leverage for you with your dealer and MF to get them to perhaps offer a trade or other solution to help you get better results with the PSBs. Especially since MF has told you what you have should be fine.

Does the dealer you bought from still sell the PSBs?

Maybe go there, talk to the dealer, and listen to your speakers there off a few different amps if possible. Maybe even take yours in and see what happens there off various amps if possible. Maybe even take the amp in to test out. See if same thing happens there.

Here is the info on the Autoformer Zeros Devices

I agree that these appear to be a viable solution for providing your amp a load that it is more suited to drive. Resulting sound should be different, but assuming the amp/speaker load match is the issue, which seems the most likely still, this should resolve any issues with not enough gas for the bass at reasonable volumes.

Comparison with an amp well suited for the speakers, at least on paper, would seem to be the one thing to try with biggest upside. At a minimum, OP finds out if prime suspect, the amps ability to drive the speakers, is in fact an issue. At best, overall performance may well go up significantly and current problems would be but a memory.

I am hard pressed to imagine how power source would produce the pattern of sound deterioration over time described. Defective speaker wires might be a reasonable explanation. Replacing speaker wires with most anything else, even basic 12-14 gauge zip wire, should be enough to determine if current wires are defective in some way leading to deterioration of sound over time.

Mcintech,

Curious what your assessment of the MF amp into 4 ohms is based on?

I think we have seen where the OPs PSB speakers present a challenging load even lower than 4 ohms at some points but nothing that indicates the MF amp is up to the task of driving them well without running out of gas, which seems to be what is happening for some reason.

Thanks.

Fish,

Can't you get your dealer who sold you the amp and/or speakers to help you sort through things?

You have a nice published resource here in this thread for reference, with feedback from various knowledgeable members, to help them help you sort through things and cut to the chase, which in my opinion means as a next step being able to try an amp that is better suited to drive the speakers on paper WITHOUT ANY QUESTION BASED ON KNOWN/PUBLISHED AMP SPECS/MEASUREMENTS.

Atmas,

WHy rule out the amps when there is nothing indicating any of them are/were up to the task of driving the load of the PSBs without running out of gas.

RF from digital, malfunctioning or otherwise, might have an effect but my experience with that is effects are noticeable from the start and not cumulative over time. Not to say any listener might notice ANY negative effect more so over time in general.

Regardless, testing with a different source to see if same results if possible would be worthwhile.

Tell him the gang on A'gon does not think you are a kook and that we will boycott his store (wherever it is) unless good customer service is demonstrated! :^)

Good customer service including ability to audition gear when needed is pretty much the only reason to buy audio gear from a brick and mortar real store any more.

Does the dealer still have the PSBs set up?

If so, maybe listen to them there (or anywhere else/another dealer if possible) and see if you hear anything similar to what you hear at home. Take note of the amp being used and investigate its specs versus yours in terms of ability to drive loads of 4 ohm or less. See if there is any correlation between what you hear there and what you hear at home and use that as a reference point for deciding what to do from there.

Yes, maybe someone reading this in NYC area can help. If dealer is not local, it's hard to audition, for sure.

At this point, I just think the over-driven amp theory has the most evidence communicated to support it. Find one that will not break a sweat into 4 ohms or less and has plenty of gas to spare as a reference for comparison. That means on paper its specs indicate double the power into 4 ohms as eight. Its the only way to know for sure.

If there are any online sellers or vendors that offer money back satisfaction on amps that might be tried, that would provide a worthwhile option to pursue with little risk, other than shipping costs maybe. A good Class D amp might fit the bill and be practical to try due to small package and lighter weight for shipping.

Yes, SPL meter readings would help confirm that there is something truly going on physically with the setup as described. I do not doubt you hear what you hear, but it would be nice to be able to prove that what you hear is actually occurring and can be measured. Its much harder to get an obsective measure of what one hears as opposed to what the speakers are delivering.

Fish, if it were me, with those speakers i would not use any integrated if I had the option in any case. I think you would find the right dedicated power amp to be a clear improvement all the time. That's why I suggest the option of buying/trying one. My assumption is that you would keep it if it resolves your problem and sounds better. If not, then have the option to return it. That's a good and fair practice anytime one buys a product in good faith. If it does not work out, then you always should have the option to return within a reasonable time period. Nothing wrong or unethical about customer satisfaction.

Now what to do with teh current amp in that case? that would depend on if it is working as designed, which it may be, or defective in some way. Testing it with an easier pair of speakers to drive would be needed to determine. If it can't drive an easy speaker load, then it may be defective, as opposed to just not up to the task of driving the PSBs specifically to their full potential.

Should be different for the better.

I'm pretty sure the BRyston amp you would need to drive the PSB load effectively is not the same as what you would find in any typical integrated amp, but have not done the research on Bryston specs to say for sure. I would not equate any high power integrated to top notch similar powered separate amps without having the numbers in front of me that establish that.

I would not use any power conditioner on power amp or integrated (which includes power amp) unless it is rated to deliver enough power and current. Use it with source devices and pre-amp but not device that provides power (integrated in this case). Most power conditioners that are suitable for use with high power amps are somewhat expensive due to build quality and power delivery capability needed.

I would keep power conditioner out of the equation with the integrated for now. Once issue is resolved, then you might try it and see. IT could well be contributing to the problem. Wish I knew it was in use earlier......

"I would keep power conditioners out of the equation period. "

Agree. Once the issue with deteriorating bass/dynamics is resolved, then add it in gradually perhaps and see what might be had further from there. Power amp would be last thing to use with a conditioner and should be totally optional at that point.

"Plan to try cablepro revelation power strip with no filters "

I'd hold off on ANY power conditioning plans until current bass/dynamics issues are resolved. :^)

" in fact can come back without the system being messed with"

Not sure that is necessarily the case as I recall?

"Yes the optimal sound has left then returned an hour or day later but I usually fiddle the cables long before that happens."

Its possible that if the amp is on but not playing music that it might return to a more normal state when played again. What would work against the amp can't handle the load theory is if the sound ever improves after the suckout occurs while the music is still playing and without changing anything, not after sitting idle for some period of time.

"I'm more than beginning to suspect a curious "malfunction" in my processes if not hearing/interpertation."

Again, SPL meter would help establish if the effect is real/physical/measurable or not if in doubt. If it can be measured, then you know with confidence what you hear is for real and not an artifact of your hearing or how you listen.

IF nothing measures, then two options:

1) try an amp that is clearly better for the job
2) track down Mr. Freud and see if he is available. :^)

THird option would be to try speakers that are an easier load to drive with existing amp.

But I think you will practically attain very high levels of performance sooner by using a dedicated amp better suited to bring out the best in the PSBs. Use the current MF integrated as a pre-amp only then, as AL suggested.

Let's see what the SPL says. We'll all be waiting to hear.....