Potential performance loss using a manufacturer specified 8Ω only amp, with 4Ω speakers (Dunlavy SC-IIs)

[neph]

I have been using a 100W Yamaha RN303D amp with my Dunlavy SC-IIs. The amp is the entry-level model, which the manual and on-device marking specify to use only with 8Ω speakers, although the manual provides power figures for 4Ωs. Its well-known bigger brother, the RN803D, does not have such limitations.

The Dunlavys are specified at a nominal impedance of 4Ω, with a minimal of 3Ω and max 7.5Ω. I couldn't find the impedance graph for SC II's but the graphs for the slightly smaller SC-Is is as follows:

I haven't felt any amp overheating or sighs of clipping. The is sometimes a hardness in the low mids, but this may have to do with the combination of placing the speakers close to the side walls and 1st order quirky polars. I feel that in some cases, low and mid-bass may be a bit underwhelming but this is not universal for all tracks.

Is it possible that there is performance loss especially in the bass, given this impedance mismatch? Will a quality class D amp provide any noticeable improvement in quality?

 

[DonH56]

I have been using a 100W Yamaha RN303D amp with my Dunlavy SC-IIs. The amp is the entry-level model, which the manual and on-device marking specify to use only with 8Ω speakers, although the manual provides power figures for 4Ωs. Its well-known bigger brother, the RN803D, does not have such limitations.

The Dunlavys are specified at a nominal impedance of 4Ω, with a minimal of 3Ω and max 7.5Ω. I couldn't find the impedance graph for SC II's but the graphs for the slightly smaller SC-Is is as follows:

I haven't felt any amp overheating or sighs of clipping. The is sometimes a hardness in the low mids, but this may have to do with the combination of placing the speakers close to the side walls and 1st order quirky polars. I feel that in some cases, low and mid-bass may be a bit underwhelming but this is not universal for all tracks.

Is it possible that there is performance loss especially in the bass, given this impedance mismatch? Will a quality class D amp provide any noticeable improvement in quality?

There is no "impedance mismatch" in the sense you are thinking. Most "8-ohm" amplifiers will drive 4 ohms with little to no problems as long as they do not have to deliver too much power, exceeding their current or thermal (heat) capability. If the amp is not overheating and you do not hear clipping consistently (usually creates a harsh high-end sound) then you are fine. The harshness and "underwhelming" bass is likely from the source recording since it is not present on everything.

You can check on online SPL calculator to estimate how much power you might be using: http://myhometheater.homestead.com/splcalculator.html

Human perception is very easily fooled into thinking there is improvement when there really is none. A new amp (or whatever) often sounds better because we expect it to, and because we tend to turn it up and listen with more focus. A tiny increase in volume will make it sound better, and by focusing more on the music (movie, etc.) we will often notice new things even though they were there all along. Many times I have noticed profound differences when adding a new component, only to discover level-matching made the differences go away, and the "new" things I heard were there all along (new amp or old).

And, of course, there are times when a new component really does make a difference. Marketing thrives on that, and exaggerating the differences ("night and day" change is very rare IME/IMO), so it pays to be cautious.

HTH - Don

 

[Head_Unit]

Yeah everything @DonH56 said agrees this speaker engineer. Does your amp get hot?
- You can check if it's clipping-you need to find/download a 300-400 Hz "0 dB" tone and you need a good AC voltmeter. If you have/get those reply and I can go into more detail.
- For more decibels of power than 100W/8Ω you'd need 300+ watts into FOUR ohms, that is the important rating even if the speakers were 8Ω.
- More power will not help bass response one iota. A different amp might interact differently with the speaker impedance and give a different tonal character but I don't believe in "night and day" massive changes aside from swapping speakers.
- Measure your in-room response. REW + UMIK-1 or to start with a phone spectrum analyzer app. I feel many "speaker" or "amp" etc problems are more likely room/placement problems.

 

[JSmith]

Dunlavy SC-IIs

Some fine speakers you have there.


JSmith

 

[neph]

Thank you for the replies

@DonH56 I agree with you. I am not searching for any magic solutions and I am aware that the most noticeable improvement will come from subs. I just got extra cautious due to the manual explicitly mentioning 8Ω only.

@Head_Unit I have a Fluke 289 that measures RMS of AC voltage and current. I suppose this is to measure power consumption and see if we get close to the amplifier's maximum output.

@JSmith Thank you. I am a fan too and I haven't heard anything that comes close in terms of natural sounding, to put it objectively.
However, I think that in terms of design philosophy (1st order crossovers to achieve perfect impulse and time coherence), they are considered anachronistic since polars get messy and ears supposedly can not discern minor timing delays of a few ms.

I have a gut feeling that if Amir was to test some Dunlavys, a headless panther would appear. I would pay good money to crowdfund a Dunlavy shipped to Amir for testing...