Bass leaves after amp warms up?

I've been following this post from the beginning but do not remember if the following has been asked. Do you know anyone else that has a similar system that you could spend some time listening to? I'm wondering if the problem is tied to a form of listener fatigue. I do not mean to offend. I ask only because somedays I can listen for hours on end with no perception difference and on others it goes quicker. Especially if I have had to mix sound for a band the day before. The patterns of the sound quality coming and going do not overtly suggest this but I thought I would throw in on the "grasping at straws".

Just re read all of the Fishing716 posts to find a pattern. Please correct me if I am wrong but it seems that there is rarely a time that the bass sounds bad when first turning the system on for that day and also you have had marginal success by often fiddling with the cables. You also have mentioned that the bass leaves quickest with video sources.

Another "grasping at straws" would be to dermine if something in your speakers are getting so warm that the "Q" of the speaker increases enough that the bass no longer has punch, impact or definition to it. You could try losely filling your ports with spongy foam before you turn on your system to see if you can recreate the "flat" bass sound for us. It does not hurt anything to try.

Yet another "grasp" would be some kind of capacitance build up in your cables that can be dissipated with enough fooling with them, not that I know how that could happen.

I know that these are some pretty out there ideas but it is all I could come up with as the other posters have done an excellent job of covering the subject.

It seems that you have spent a considerable amount of time trying to regain the good sound after it is lost but have you spent anytime trying to lose the good sound. IOW have you done the mute/unmute or switching inputs etc repeatedly before you have lost the good sound to try and create the problem?

If you have some success on causing the problem on purpose it would give us another clue.

Why don't you pick up a couple of very quiet "whisper" fans to keep the amp cool to see if it is truly a warm up thing.

Are you using the "plugs" on the bottom woofer ports? If not you should try them. You may find that with the plugs the bass is lean at first but fills out after the amp is fully warmed up.

IMO, It sounds like you have about the same bass energy in both good and bad recordings. It seems to be the character or quality of the bass that is changing. Tight and defined when amp cool, loser and woolier when warmed up. The Bryston amps I've used in the past had this quality to them. If you do not have the plugs installed in the lower vents I suggest you try them. The speaker will have an overly tight or lean bass until the amp gets warm upon which the bass should take on a more normal "Q".

Have you tried the speakers without the plugs? If so and it is even worse than I'd say we are on the right track. When you add the plugs you are lowering the "Q" of the speaker. Some speaker companies included different lengths of plugs so that the owner could tailor the speaker for the "Q" that works best for his room/amp combination.

The only other possibility is using a whisper fan on the amp so that it never warms up.

Have you tried any type of fan to keep the amp as cool as possible to rule out warm up issues?

You could try any fan you have laying around and if that works you could install a very quite fan later.

Glad to hear that you will be able to try some other equipment. It will hopefully give us some new clues.

I'm not suggesting that your amp is running hot. I know it's a long shot but I am trying to deduce if the sound of the amp when it is "cold" has the good bass. There is a reason that most reviewers will go to great lengths to fully warm up the equipment before they listen because the sound will usually change some from dead cold to fully warm.

Fishing, when you left the amp on did you stop the music or leave it playing? Some amps do not get warmed up or stay warm unless they are playing music.

Just trying to totally eliminate "warmed up" as the cause.

IMO the amp should not dictate what speakers you own. It's the other way around. I refuse to believe that there is not an amp out there that will do a great job of driving the PSB's without losing some bass control as it warms up. In reviews that I've read the Musical Fidelity's are an excellent product but they are not known to have the best bass control. Each of us have a different set of priorities when we put together our systems. After listening to both of the "good and bad" recorded tracks, IMO, "Fishing" needs an amp that maintains very tight control of the bass. Hopefully the larger Musical Fidelity will keep all of the sonic properties of the smaller but maintain better control of the bass by virtue of it's higher cuurent capability and bigger probably "stiffer" power supply. Only time will tell.

to "Drubin". IME designing and building custom speakers I have found that excessive heat (in the voice coil, inductors and resistors) will not affect woofer phase nearly as much as the total Qts of a ported speaker. It can change enough to make the bass port tuning looser. However I have been exploring that possibility with the OP and his responces do not suggest that he is getting the speakers nearly hot enough plus he is using the tuning plugs in the lower woofer ports which would minimize any changes in the speakers Qts.

The OP'r has a post in another section asking about headphones. Maybe he has decided to take another approach to enjoying his music.

Either way I hope that he can get back to enjoying the music instead of wrestling with his system.

Certainly any help is appreciated but recordings of the sound differences were sent out and I noticed a difference. I still believe it is somehow related to heat. Either in the amp or the speakers or both. The "bad" sound reminds of an amp that is underpowered or does not have tight control of the bass. My hunch is it is a combination of issues since it never could be replicated consistently.

I apologize if this has been asked already but how loud do you listen? Some speakers Qts (how tight or loose the bass is) can change when the voice coils get hot from playing loud, especially with music that has a lot of deep bass.

Which AQ speaker cables are you using? IIUC, they would have to be a thinner gauge for the treble than they have for the bass before a miss wire would mess up the bass.

If the treble wire was thin enough it would conceivably get worse as the cable got hot.

JJ offered a clever theory, but looking at the description and photos of the Comet at the AQ site I don't see anything suggesting that the gauge of the treble wiring is extremely thin,

Don't know how clever it was but after 454 posts from lots of experts I can only come up with what are obviously long "reachs" for a possible explanation for the bass issue. I agree with Al that the wire that "biased towards high frequency finesse" does not look thin enough to be a problem however I am not well versed in the AQ wire topology or how the battery bias may be working if hooked up wrong. Also I came to the same conclusion, now that I know the cable, is that the only miswire that should still work should effect the bass from the start, not change with playing time.

Also there has been some discussion of the PSB's having a low impedance. I have not seen a graph but if that dip is in the bass range it would, IIUC, not take to much of an increase in wire resistance to effect the damping factor. IMO, from the recordings that were sent out, it is not a quantity of bass issue it is the quality of the bass that changes.

Again, a way out theory, but without physically seeing the internal construction of the speaker wire it's all I got at the moment.