High vs low damping factor in amps (Bass "suspension")

[AJM1981]

I own the wharfedale 4.2 loudspeakers and have them placed in a well treated room.

This morning I decided to switch between my classic Sansui au505 and modern class d Yamaha wxa50 and play some jazz (Blue in Green by Miles Davis). With the Yamaha having a high damping factor and the sansui au505 a low one.

I will try to describe the "illusion" as well as possible. I will not make pro's and cons because those preferences are different from user to user.

High damping factor (modern Yamaha):

With the 3-way loudspeakers on stands, the bass seems to come right out of the woofer in front. It is tightly controlled, hefty and the idea that a subwoofer can seemlessly connect "sonically" is clear as it creates seperation in the bottom layers. I think this is probably the most accepted application as it is technical-philosophical more sound. And it adds space for selling subwoofers. Which Yamaha does as well. It also serves a modern market.

Low damping factor (classic Sansui):

It seems to utilize more potential from the woofer of the same standmount loudspeakers. The bass blooms in bottom end territories that it seems to get take more advantage in what the loudspeakers are capable of by themselves. The bass sounds like it expands to where the stands of the 3-way system are as well. Resulting in what some might describe as more of a "holographic sound" due to more movement of the voice coil. But at the same time I would never have bought a subwoofer having an amp with a lower damping factor as it is difficult finding the extension line.

As much I get the modern technical idea behind high damping factors I think that especially for Jazz or any accoustic types of music a lower damping factor seems to be more 'sound' to the natural reproduction as there are no device-factors as with electronic bass (amps) and synthetic ones.

But getting back to lower damping factors would trouble a more modern eco system of loudspeakers and subs as well as a majority of users preferring 'tight' bass.

Any takes on this topic?

 

[popej]

Electric damping of a speaker is regulated by total resistance of the circuit. The higher resistance, the less damping. Total resistance consist of:
- voice coil resistance, could be about 4 Ohm,
- speaker wire and connectors, could be about 0.1 Ohm,
- amplifier resistance, which is specified as "damping factor".

Sansui specifies damping factor 50 at 8 Ohm, which means 0.16 Ohm.
Wxa50 is measured as 62 at 4 Ohm, which means 0.06 Ohm.
So we have total resistance for Sansui 4.26 and for wxa 4.16. The difference is about 2%. Do you really believe, that it matters?

 

[Jim Taylor]

Your descriptions use non-scientific terms. Non-scientific terms are not verifiable. They are only subjective, and as such are valid only to you.

That's the advantage of scientific measurements; they can be checked and re-checked, and their validity can be confirmed or rejected by other people, based on instrumental (non-subjective) methods.

It is worthwhile to remember that once a person becomes convinced of subjective qualities, those subjective qualities become "real" to them, even to the point of mis-applying scientific processes to explain the subjective impression. This is a variation of "self-serving bias", one of the cognitive biases.

Here is a list of biases. Quite interesting. https://en.wikipedia.org/wiki/List_of_cognitive_biases

 

[AJM1981]

Electric damping of a speaker is regulated by total resistance of the circuit. The higher resistance, the less damping. Total resistance consist of:
- voice coil resistance, could be about 4 Ohm,
- speaker wire and connectors, could be about 0.1 Ohm,
- amplifier resistance, which is specified as "damping factor".

Sansui specifies damping factor 50 at 8 Ohm, which means 0.16 Ohm.
Wxa50 is measured as 62 at 4 Ohm, which means 0.06 Ohm.
So we have total resistance for Sansui 4.26 and for wxa 4.16. The difference is about 2%. Do you really believe, that it matters?

Thanks for the math. I would not like to hang on believing something. Prefer to be totally wrong and step out of any assumption. I am open to the explanation in why the bass profiles of these two seem so clearly different

 

[popej]

am open to the explanation in why the bass profiles of these two seem so clearly different.

You assume, that your hearing directly replicate physical sound. This is not true, what you hear depends on many factors, including your experience, expectations, believes, mood and so on.
Look for McGurk effect on YouTube. It is funny, it clearly shows, that what you hear can depend on what you see.

 

[mhardy6647]

Does the AU505 have capacitor coupled outputs? I am thinking that it might -- a quick Googlin' suggests that the amp's outputs are indeed cap-coupled.
If so... have the capacitors ever been tested and/or replaced?

The ESR of the output coupling caps may be high... that could explain everything.

Even if the capacitors are fine, there'll be some roll-off and phase shift from their presence in the output circuit that may well have audible consequences.

 

[DanielT]

Did you play at high volume when you did those subjective listening tests?

Your Wharfedale EVO 4.2 has 87 dB sensitivity according to the manufacturer. In reality, maybe an average of around 85 dB. That's based on what the manufacturer states vs what the test results show. In Wharfedale's case, they seem to be a few dB lower than stated. Check for example and compare the specs and test results for Wharfedale Diamond 220, Wharfedale EVO 4.1 and Wharfedale Linton 85th Heritage.

What does this matter? A few dB lower sensitivity than what the manufacturer states, so what. Normally it doesn't matter much BUT your Sansui AU-505 has 12 watts of power. IF you hear any difference between your amps when you listen, it may be because your Sansui AU-505 is driven into clipping, if you turn the volume up a bit with, say, a pair of 85 dB sensitive speakers. And an amp driven into clipping, you can hear that when it happens.
So that could be what makes you hear a difference between your amps.

https://www.hifiengine.com/manual_library/sansui/au-505.shtml

Your Yamaha wxa 50 is specified at 55 W into 8 Ohms.

 

[AJM1981]

You assume, that your hearing directly replicate physical sound. This is not true, what you hear depends on many factors, including your experience, expectations, believes, mood and so on.
Look for McGurk effect on YouTube. It is funny, it clearly shows, that what you hear can depend on what you see.

Get your point. But that would pull 'everything' to a psychological level and assume that this 70s amp and a recent one have identical output overall and there would not be any differences between amps. But that is not really the case either. I would be surprised if to some double blind degree there are no "little" audible differences at all.

 

[popej]

Does the AU505 have capacitor coupled outputs?

Yes. And it is 1.5mF, it can influence low bass.

 

[mhardy6647]

Yes. And it is 1.5mF, it can influence low bass.

Yeah, I kept digging and found this.

Vintage Audio - Sansui AU-505

Restoration of a Sansui AU-505 audio amplifier.

alexandrugroza.ro

1500 uF at 63V -- a priori, I'd posit that is very likely to be the root cause of any warm, tubey, bloozy, boozy bass from that little Sansui amplifier. Especially if the capacitors are 50-plus year old originals.

 

[popej]

But that would pull 'everything' to a psychological level

Actual consequence is, that we don't trust in audio tests, which do not cover for this effect.

 

[AJM1981]

Yes. And it is 1.5mF, it can influence low bass.

Does the coupling create some interaction with the damping factor? Or should it not be viewed as such?

 

[mhardy6647]

Does the coupling create some interaction with the damping factor? Or should it not be viewed as such?

Yes by definition. The presence of the output capacitor alters the output impedance of the circuit in a frequency-dependent way. The output capacitor is being used as a filter -- specifically to remove DC from the amplifier's output signal. Passing the DC to the loudspeaker would likely cook the woofer voice coil.

Damping factor is no more and no less than the ratio of a nominal load impedance to the amplifier output impedance. An amplifier with an output impedance of exactly 0.1 ohm across the audio frequency band, connected to a purely resistive 8 ohm load (constant and frequency-independent impedance of 8 ohms) would have a calculated damping factor of 80. It's just a number, with very little relevance to reality.

The problem is that virtually no loudspeaker has a frequency-invariant impedance. Many amplifiers don't (or, historically, didn't) have frequency-independent output impedance, either, so the damping factor is, at best, an index meant to indicate how the amplifier interacts with a load. Damping factor has long struck me as one of the most useless values attached to amplifier performance -- but that's not exactly in sync with topic of this thread.

 

[mhardy6647]

@AJM1981: If your AU-505 has 55 year old output coupling capacitors, the low frequency performance into a loudspeaker will probably be mushy relative to brand new coupling caps. Raising the value of the coupling capacitors when replacing would likely improve bass extension and quality even further -- 1500 uF is a fairly low value.

By comparison, the HH Scott 342C receiver, with a quasi-complementary circuit (which still requires output coupling capacitors to alleviate a DC offset) and output power capability of roughly 20 'continuous' watts per channel, used 2200 uF coupling caps.

 

[DSJR]

I have to add something in at least a subjective confirmation of the OPs findings as I've heard this myself in the dark old days!

Amplifiers have become so much better sorted these days, the excesses of the past now well into the distance, unless it's a high-end confection with these shortcomings engineered in as a selling point!

P.S. We're so spoiled these days with inexpensive audio electronics performing so much better now than half a century ago

 

[popej]

Damping factor has long struck me as one of the most useless values attached to amplifier performance

Damping factor is a relic from tube era. It had some meaning, when it was a single digit value.

 

[DVDdoug]

Does the older receiver had a "loudness" switch? That will boost the bass at lower volumes.

 

[DanielT]

@AJM1981: If your AU-505 has 55 year old output coupling capacitors, the low frequency performance into a loudspeaker will probably be mushy relative to brand new coupling caps. Raising the value of the coupling capacitors when replacing would likely improve bass extension and quality even further -- 1500 uF is a fairly low value.

By comparison, the HH Scott 342C receiver, with a quasi-complementary circuit (which still requires output coupling capacitors to alleviate a DC offset) and output power capability of roughly 20 'continuous' watts per channel, used 2200 uF coupling caps.

That could be an explanation. Plus tone controls that are a bit off and/or 12 watts driven into clipping.

 

[AJM1981]

@AJM1981: If your AU-505 has 55 year old output coupling capacitors, the low frequency performance into a loudspeaker will probably be mushy relative to brand new coupling caps. Raising the value of the coupling capacitors when replacing would likely improve bass extension and quality even further -- 1500 uF is a fairly low value.

By comparison, the HH Scott 342C receiver, with a quasi-complementary circuit (which still requires output coupling capacitors to alleviate a DC offset) and output power capability of roughly 20 'continuous' watts per channel, used 2200 uF coupling caps.

Nice one and thanks for the explanation and tip! I got my au505 in a pretty good condition (have no reference to how a new one sounded back then) Will keep it in mind for a qualified service technician I know. The headphone jack gives some friction, so there is at least one excuse for servicing this year. This might be a plus

 

[antcollinet]

Your Sansui amp has 12W power output. Your Yamaha has around 80W available.

Why on earth would you assume your perceptions of the sound (even if they are real differences, and not just perceptive bias) are due the trivial difference in damping factor, rather than the much more significant difference in power output?

Or even more likely - a failure to level match the output level sufficiently well (I am assuming you didn't do this using a test tone and volt meter on the speaker terminals?)

Or any of perhaps a dozen or so other differences - some of which have also been mentioned up thread.