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Old speakers sound harsh

brab

pfm Member
I have a pair of ancient Yamaha minisystem speakers I recently set up in a third system. They sound very high pitched and harsh. I don't remember them that way and my current hearing is far less sensitive to high frequencies than it used to be. Is this expected with old speakers- surrounds hardening or some other change?
 
They’re not Yamaha ‘AST’ speakers by any chance, are they? If so, they will sound weedy as they require the correct matching amplifier to give the right bass response.
 
No- they're YST-7 but thanks for the quick reply! I did have a quick look online and there is an AST system where the speakers look a little like mine, though.
 
Same thing. Yamaha had to stop using "AST" (which stood for Active Servo Technology) due to a copyright by another company, so they changed to YST (Yamaha Active Servo Technology).

Either way, it means the speakers are electrically matched to the amplifier they are supposed to be used with and will sound poor/odd with a conventional amplifier.
 
Same thing. Yamaha had to stop using "AST" (which stood for Active Servo Technology) due to a copyright by another company, so they changed to YST (Yamaha Active Servo Technology).

Either way, it means the speakers are electrically matched to the amplifier they are supposed to be used with and will sound poor/odd with a conventional amplifier.
I take it they need some EQ correction, similar to many Bose models then?
 
More to do with "seen" resistance?

"The Yamaha AST unlike any existing amplifier, is an amplifier that can have a negative resistance figure in its output impedance.


The voice coil impedance of a conventional speaker is approximately 6 ohms, and the AST can apply a negative resistance to eliminate this voice coil resistance portion.


As a result, with the combination of the AST-Amifier and the AST System exclusive speakers, the resistance between the amplifier and speakers will become approximately 0 ohms and the electrical current will be able to run infinitely (condition close to superconductivity).


In other words, the amplifier output voltage will directly drive the speakers, hence making it possible to provide a powerful driving force and damping power of steady speed operation."
 
A strange thing to do. Remove most of the DC resistance, which only varies with temperature, and the current and hence the coil motor force is going to become much more non-linear with coil position in the gap and many other variables
 
Negative output resistance is well documented. It lowers the electrical Q value of the speaker. The well liked Audio Pro subs with ACE bass used a development of this where the complex output impedance of the amplifier was varied, and made rarher small bass drivers behave like much latger ones while still needing only a small cabinet. For example, it made a driver behave like the moving mass was much larger tha in reality, useful when you are designing a sub.

Nobody ever acused Audio Pro subs of having anything but for their size very low distorsion.

I think it was Audio Pro's patent that Yamaha infringed.
 
I reviewed the Yamaha AST speaker/amp system for What Hi-Fi back in 1989. Impressive stereo imagery and scale but some sameness about the bass and a need to really drive the system hard to get the best. The matching amplifier had a specific plug-in module for the speakers in use. I suspect the AST-S1/A-10 combination was the only one sold in the UK and possible the only one made at all. I can do a pdf if anyone is very keen to read my musings. PM as usual.
DGP
 
I reviewed the Yamaha AST speaker/amp system for What Hi-Fi back in 1989. Impressive stereo imagery and scale but some sameness about the bass and a need to really drive the system hard to get the best. The matching amplifier had a specific plug-in module for the speakers in use. I suspect the AST-S1/A-10 combination was the only one sold in the UK and possible the only one made at all. I can do a pdf if anyone is very keen to read my musings. PM as usual.
DGP

There was a surprisingly large range of AST amplifiers and speakers, many of which were never offered for sale in the UK.

I have two sets of the AST-S1s and one ASt-A10, and the setup is actually very capable but i agree with you that the bass is a little one-note. It's impressively deep, though, and the scale of soundstage that can be achieved from such dinky speakers is quite surprising. I'm not convinced that the AST-A10 is the greatest amplifier in the world as its output stage is based on hybrid chips. There are other Yamaha models that accept the plug-in cartridges that look to be better but very few of these were imported into the UK, although I might grab one for my second set of AST-S1s once i refurbish them.

I recently obtained a copy of New Hi-Fi Sound's original feature on them and their suggestion was that the setup performed best with the AST-A10 used effectively just as a processor on the output of another power amplifier (as it has speaker-level inputs as well as line level) so I must give that a try. Would be interested to read your review as well, though.

As an aside, whenever the world allows the next Hi-Fi Wigwam Kegworth show to happen, I'm planning to bring my AST-A10/AST-S1s along if anyone would like to hear them.
 
What would the advantages be over conventional amplifier plus equaliser? The power requirement will be the same
 
I'm not entirely sure - I'm just reporting what the reviewer said and, as it's a configuration I haven't tried yet, I figure it's worth giving it a go! So far, I've only used the AST-A10 as a conventional power amplifier.
 
My thought is that equalisation is likely to have less non linearity and at least it would be possible to correct the group delay
 
I recently obtained a copy of New Hi-Fi Sound's original feature on them and their suggestion was that the setup performed best with the AST-A10 used effectively just as a processor on the output of another power amplifier (as it has speaker-level inputs as well as line level) so I must give that a try. Would be interested to read your review as well, though.

Just PM me with an email address if you want a pdf copy.
DGP
 
Reading the article, I am wondering if there was a translation problem and that this is actually a current drive circuit, the sense resistor tends to raise output impedance.
Current drive does tend to have the property of being more linear at high cone excursions and is often used in sub-woofers.

The article notes a tendency to harshness
 
MFB was a different thing, direct feedback of cone motion. Obviously only useful when the cone is pistonic so mainly for sub-woofers
 


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