impedance mismatch

[rob2]

Can anyone tell me what the audible effects of an impedance mismatch between amp and speakers would be?

I'm beginning to think there may be a mismatch with my gear.

(is this question in the right forum?)

The amp is a Sugden A21a Class A, S/S, 25w.

The speakers are an older Australian brand - AMW Studio Monitor 4100, 4 way, 8 ohm 'nominally', and seem to have a reputation for being difficult to drive. I have no idea what the impedance curve of the speakers is and I don't have the means to find out.

My listening problem isn't distortion, but a certain lack of 'flow' of sound - its sometimes feels a little restricted, and its more noticeable at lower volumes not higher. In general there's enough grunt but at certain times the sound lacks some freedom, if that makes sense.

I don't listen at disco levels, usually around 9 on the volume dial.

 

 

Edited May 1, 2017 by rob2

[Nigel]

All I know, and about electronics that ain't alot, but what I have learned is that the expression "impedance mismatch", as though it is a problem, is not appropriate to audio components. I think it is relevant for radio transmission or microwave links or something.

With audio, it seems that the lower the output impedance of a preamp, dac, tuner, the better. The higher the input impedance of preamp, amp,  the better.

Ideally (and impossibly) 0ohms output impedance into infinite ohms input impedance.

 As always, I could be wrong, or overly simplistic.....

  You quote the amp in Watts which is different again.

 

[Zaphod Beeblebrox]

52 minutes ago, rob2 said:

Can anyone tell me what the audible effects of an impedance mismatch between amp and speakers would be?

I'm beginning to think there may be a mismatch with my gear.

(is this question in the right forum?)

The amp is a Class A, S/S, 25w.

The speakers are a 4 way, 8 ohm 'nominally' and seem to have a reputation for being difficult to drive.

 

There's no, one, artefact that can be described. MUCH more information is required. 

 

Amplifier?

Speakers?

Impedance curve of speakers?

Specs of amplifier? 

Room size?

 

With 25 Watts, I'd be far more concerned about speaker efficiency. For most high quality speakers, 25 Watts is a bit on the light side. 

 

IF there is a problem with impedance, then audible issues can range from gross distortion, even at low levels, to moderate distortion, or just a general 'running out of puff'. 

[VanArn]

A  Class ' A' amplifier is normally specified to supply its power into a nominal   load impedance.  This is  to make sure that the biasing point is halfway between the clipping and cut-off points of the output devices. There are many multiway speakers that offer difficult loads to amplifiers and often this is the reason that a certain amplifier may be preferred over another on an  amplifier comparison test. You would have to find  an impedance curve for your speakers or have it measured to know if there is a serious  mismatch problem.  

[rob2]

I've updated my initial post with more detail now.

Thanks for your input fellas.

[VanArn]

The extra information is helpful. I barely remember the AMW brand. If yours are the model with a KEF B139, then the efficiency is on the low side  ( approx. 84.5 dB SPL for 1w input) for a Sugden A21 a  amplifier.

[Zaphod Beeblebrox]

11 minutes ago, rob2 said:

I've updated my initial post with more detail now.

Thanks for your input fellas.

 

AMW 4100 speakers need A LOT more power than 25 Watts. Give them at least 100 Watts and they will surprise and delight. The 4100 was not a particularly difficult load. 

Edited May 1, 2017 by Zaphod Beeblebrox

[rob2]

Yes they have the B139. 

I assumed that Class A watts were not ordinary watts.

It seems I'm now in a quandary - I love the speakers and I love the amp !?! and don't want to part with either. 

[Zaphod Beeblebrox]

17 minutes ago, rob2 said:

Yes they have the B139. 

I assumed that Class A watts were not ordinary watts.

It seems I'm now in a quandary - I love the speakers and I love the amp !?! and don't want to part with either. 

 

Class A Watts are the same as Class A/B Watts. NEVER assume the following:

 

* That an amplifier which is claimed to be Class A, is actually Class A.

* That A Class A amplifier is, somehow, superior to, or more powerful than, a Class A/B amplifier of the same power rating. It's all in the power supply and output stage SOA. NOT the Class A bias current.

 

IMO. Keep the speakers and dump the amp. Look for a very high quality 100+ Watt amp. I know the speakers well. They were great old speakers, designed by Colin Waite and Reg Mahoney. Two guys who fostered Peter Stein to build the early ME power amps. As I recall, they purchased the first one Peter built and ran it with their speakers for many years. 

[VanArn]

That is the choice ,that has to be made. Keep the speakers and sell or trade in the amplifier for a more powerful one, which also should be  the cheaper option as your Sugden is virtually new. Offer your speakers on the S/H market  and find a high efficiency  quality speaker that suits your tastes, which inevitably leads to a higher  cost depending on how many drivers are used to cover the spectrum.  

[rob2]

This is real dilemma - buying anything audio is such a long painful process. It took about 18 months to find the amp!

Anyway, thanks for your input guys. Its food for thought and something that had crossed my mind, that I didn't want to think about.

Your comments are appreciated.

[Tasebass]

quoted speaker impedance is normally at 1000Hz at the speaker terminals which to me suggests they are next to useless as the ohms value can vary hugely with frequency...let alone the current/volts/cable/crossover etc..

 

A system will show whether its happy or not through the SQ your hearing and whether its running slightly hot for example...or hotter than it should...

 

All from personnel experience of course...

 

Tase.

[Tasebass]

11 minutes ago, rob2 said:

This is real dilemma - buying anything audio is such a long painful process. It took about 18 months to find the amp!

Anyway, thanks for your input guys. Its food for thought and something that had crossed my mind, that I didn't want to think about.

Your comments are appreciated.

 HUH!!

 

buying audio should be a whole lot of fun.....go out and have fun with it..taken me over 6 years to build mine ( aint finished yet ) had a blast along the way...( plus other issues non hifi related )

 

Tase

Edited May 1, 2017 by Tasebass

[rob2]

Its fun if you have the cash.  I've just retired, so I'm not earning, and I thought I'd got myself a system to see me through a goodly amount of years without needing to worry about it - but that's the audio journey! Maybe I'll have to come out of retirement!

[rob2]

In the classifieds recently I saw a device for making the amp 'see' the speakers as having a different impedance (made by the same guy that invented anticables) and wondered if that could work - the amp sees the speakers as 16 ohm instead of 8 ohm dipping to 2 and therefore easier to drive. I don't know about this stuff, hence this topic question.

[Tasebass]

45 minutes ago, rob2 said:

Its fun if you have the cash. 

 

can be fun with not a lot of dosh too....your retired means plenty of playtime...enjoy!!!

[Zaphod Beeblebrox]

25 minutes ago, rob2 said:

In the classifieds recently I saw a device for making the amp 'see' the speakers as having a different impedance (made by the same guy that invented anticables) and wondered if that could work - the amp sees the speakers as 16 ohm instead of 8 ohm dipping to 2 and therefore easier to drive. I don't know about this stuff, hence this topic question.

 

It is bogus (of course). In this universe, there is no such thing as a free lunch. The device is just an 'autoformer'. Essentially, a non-isolated transformer. And, like all transformers it will:

 

* Halve the impedance (not really, but more on that later).

* Halve the available power at 8 Ohms.

* Increase the current available.

 

The catch with any transformer is that there are always winding losses. In the case of the type of transformer suggested, those losses would typically amount to between 0.5 Ohms and 2 Ohms. That's wasted power. Taking the worst case, that means if you are driving a 2 Ohm load, with a 2 Ohm secondary resistance, 50% of the power is wasted in the windings. Your 25 Watts now becomes 12.5 Watts available for the speakers.

 

Buy a bigger amp. In the real world, 25 Watts is just too small for modern, high quality speakers.  

[Krispy Audio]

7 minutes ago, Zaphod Beeblebrox said:

Buy a bigger amp. In the real world, 25 Watts is just too small for modern, high quality speakers.  

 

Not sure if this is an appropriate closing comment for someone deciding on an amplifier... There are plenty of modern, high quality speakers requiring no more than 25w.

[georgehifi]

 

Nick Barofsky of Riverina HIFI Brookvale, sold must be close to 100 pairs of Collin Wait's AMW-4100's, and around 70% were with the Sugden A48 48watts per channel, then the later A48 MkII which was 60watts, the rest were split up with Naim 160's or 250's and the ME100.

Your Sugden A21 won't have enough for the 4100's, as the A48's were just enough.

 

Cheers George 

[georgehifi]

18 minutes ago, Zaphod Beeblebrox said:

Buy a bigger amp. In the real world, 25 Watts is just too small for modern, high quality speakers.

 

Not with these ML-2 monoblocks, 25watters pure A at 40kg each.

 

Cheers George

[Zaphod Beeblebrox]

40 minutes ago, Krispy Audio said:

 

Not sure if this is an appropriate closing comment for someone deciding on an amplifier... There are plenty of modern, high quality speakers requiring no more than 25w.

 

The poster already has the speakers he likes. As is ALWAYS the case, it is appropriate to choose speakers first, then the requisite amplification to suit those speakers. I reiterate: I have more than a passing familiarity with the 4100 speakers. They MUST be driven by at least 100 Watts. Therefore, it is appropriate to select a more powerful amplifier. 

[rob2]

Perhaps a bit more background about my journey.

Its very hard to audition anything - it requires audition in my home not a showroom, and speakers are too hard in that regard, plus I wanted to equal the quality of the AMWs (what would I have to pay?).

I wanted an integrated amp, as separates meant even more auditions, plus interconnects add another audition dimension and complicate things even more.

I wanted something that was well built, not Chinese-made with flimsy buttons and presumably flimsy electronics. I wanted it to last maybe 20 yrs (foolish? maybe).

So I went for an amp that came from a solid background. I also happen to like its sound. I had previously had a Lux 507U which had awesome bass but I felt the rest was veiled - I go to live concerts, so I know what live sounds like, and Lux didn't do it. Sugden did.

So after all this, maybe its the amp that should stay - but then it means replacing the speakers. Aarrggghh!

So if I was to change the amp, which? - I can't afford the likes of ME. (I did audition the Musical Fidelity M6i and was very disappointed).

Edited May 1, 2017 by rob2

[andyr]

54 minutes ago, georgehifi said:

 

Not with these ML-2 monoblocks, 25watters pure A at 40kg each.

 

Cheers George

 

Ummmm, George ... some speakers can't be driven well with a 25w Class A amp. 

 

Sure, 25w is the Class A power - and they then shift into Class AB - but they still won't deliver (rms) 500w into 4 ohms ... which, say, Maggies like.

 

 

Andy

 

Edited May 1, 2017 by andyr

[Wimbo]

You have a lot of conditions there mate.

Your the one setting the conditions, so you'll have to be the one with the answers.

I.E. your gonna have to get out and do some work.

[andyr]

A sad story, rob2.

 

My comments below - in blue.

 

Regards,

Andy

 

EDIT: In terms of "impedance mismatch" ... possibly the AMWs drop to a low impedance and the Sugden can't cope with this?

 

24 minutes ago, rob2 said:

Perhaps a bit more background about my journey.

Its very hard to audition anything - it requires audition in my home not a showroom, and speakers are too hard in that regard, plus I wanted to equal the quality of the AMWs (what would I have to pay?).

I suggest you keep the AMWs.

I wanted an integrated amp, as separates meant even more auditions, plus interconnects add another audition dimension and complicate things even more.

Sure, integrateds simplify things ... but, really, an extra IC is neither here nor there.

I wanted something that was well built, not Chinese-made with flimsy buttons and presumably flimsy electronics. I wanted it to last maybe 20 yrs (foolish? maybe).

Not foolish! 

So I went for an amp that came from a solid background. I also happen to like its sound. I had previously had a Lux 507U which had awesome bass but I felt the rest was veiled - I go to live concerts, so I know what live sounds like, and Lux didn't do it. Sugden did.

Do Sugden do a more powerful integrated?  Otherwise, I know Naim do an integrated (or two) - can you take your Sugden into a Naim dealer and compare it against the Naim integrated?

 

Do you actually need an 'integrated'?  (Do you have more than one source?)  If not, you can buy a power amp with a volume control.  There is an AKSA 55 (55w into 8 ohms, 100w into 4 ohms) with a volume control in the FS right this moment.  I used this on 3 ohm Magnepan mid panels with no problem for many years.

So after all this, maybe its the amp that should stay - but then it means replacing the speakers. Aarrggghh!

So if I was to change the amp, which? - I can't afford the likes of ME. (I did audition the Musical Fidelity M6i and was very disappointed).

 

Edited May 1, 2017 by andyr