Advice needed: low volumes & power to drive

DrPo posted:

Around xMas I had on home loan a 282 + HC + 250 (non DR versions) set substituting my resident integrated amp. What impressed me was the additional detail I could perceive in almost every track I was trying combined with (or perhaps, due to?) a much tighter bass which I absolutely loved - in fact I posted somewhere that if this is what people mean with "NAIM timing" I finally "get" it.

At the same time I had the distinct impression that I needed to crank the volume slightly higher than my normal levels (< 90dB) to achieve a "homogeneous" (across  frequencies) result.

I was yesterday discussing this topic with a dealer friend who insisted that this is a sign of lack of driving ability of the NAP250 of my speakers (nominally 4 Ohm going down to 3 Ohms and with side woofers which some people claim pose significant demands on current delivery, on the other hand with a theoretically benign 89dB sensitivity) and that a beefy (of the Bryston/Krell school) power amp would be the right solution for a "full" sound at low listening levels.

I was a bit surprised as I would normally associate power ratings with ability to drive speakers at high listening levels without distortion - not low ones.

Any informed opinions on  this topic would be highly appreciated!

 

 

 

 

 

I found the 250dr quite remarkable in my system at low volume, just upgraded to a 300dr and that's even better obviously the rest of the system and room play their part.

My understanding is that a higher power amp would provide more detail when listening at lower levels. 

Low level detail is related to amp and power supply design and not correlated to nominal output power.

A 250DR is likely to give better results at low level than a 250.2 (and the 300DR does even better due to the improved PSU and dual mono design).

It's unlikely that a 250 is struggling to drive your speakers at normal listening levels (unless they're a very poor design - which I firmly believe to not be the case) as the 250 was designed to cope with 2Ω loads.  However there might be an issue with the speaker, a 250 and the Nordost cables (i.e. they're not providing enough inductance to fully stabilise the amp, or giving too high a capacitance when used with a speaker that has a very low impedance or high phase angle at HF).

This info comes from my (albeit limited) experience of actually designing audio power amps.

My 250DR is definitely better to listen too at lower levels than when I had the SN2 bare . 

thanks all for your replies

@Huge:  It's not that the amp cannot power the speakers, far from it it was the best sound i got out of them at home - i only note that compared to my current amp (which is a bit more powerful) I had to listen to slightly higher levels to enjoy a "full" sound. I will try to do the cables experiment at my dealer's. I do however have a close friend with a 252/SC/300 set up and basically same speakers who got in written from NAIM a confirmation it would be pretty much OK to run with Nordost cables

I think your dealer is talking out of a proverbial backside  is he a Naim dealer or a Krell dealer by any chance?

As [@mention:36201736971392588] wrote: Naim NAPs need special, low inductance and capacitance cables to stablisie them and make them work properly. NAP 250 provides sufficient current to drive even the Quad ESLS and they mad-swing imedance changes (anywhere between 2 and 20 ohms in reality).

What you must also realise that music is not 'designed' to be played quietly and that low, bass frequencies require more power to be audible.

Adam

Dr Po,

Could it be that the integrated has a greater perceived bass level (i.e. a 'warmer' sound) than the more neutral separates?  In this case the effect of the Fletcher-Munson response curves would lead you to increase the volume to achieve the same perceived bass level to which you have become accustomed.

In practice I don't think that, as humans, we're any good at judging relative sound levels in absolute terms, as the response varies so much across a 3D pattern of frequency and loudness.

@Huge; i really think this is the most logical explanation and was myself "suspecting" something similar but deep down hoped someone with better theoretical understanding would propose it, so thanks :-)

@Adam: couple of points here:

  (a) there are two dealers involved: my dealer who very proudly carries NAIM (among other brands including the one i currently use) and the dealer friend who carries Bryston and game me the opinion which triggered this thread.

  (b) I find the cable compatibility story fascinating. Both inductance and capacitance figures are per meter. My cables have about x2 capacitance (10.3pF/ft vs 16pF/m) and 0.4x the inductance (0.135hH/ft vs 1mH/m)  of NACA5. Given that NAIM optimum length is between 5 and 10 meters and that my speaker cable length is 2.5m i would infer that my speaker cables have both  low inductance and low capacitance overall ... Am i missing something ?

NACA5 specs are:

C = 15pF/m

L = 1.0uH/m

R = 10mR/m

DrPo,  re your cables;  with a Naim amp the important factor is inductance, it needs to be reasonably high to load the amps output stages & stabilize any ringing caused by capacitive reactance.   Hence the Naim recommendation for 3.5m of NACA5 which is really saying 3.5uH of inductance (minimum).    Capacitance is not so important, lower the better but it will only start to become a problem using  multi-conductor woven/plaited cables

Do I understand correctly that your existing Nordost cable length is 2.5m.   Its not ideal even using NACA5,  but with NACA5 its not a real problem other than it'll probably sound better with double to 5m.  

2.5m of Nordost Frey 2 is something I would be concerned about.    Its 0.44uH/m ... 2.5m = 1.11uH & that is aprx the same as only 1m of NACA5.   

@Adam: yes, these are the figures I have had in mind in my quick comparison as well.

@Mike-B: thanks a lot, this clarifies the point; if we need the minimum inductance equivalent to 5m NACA5 then my cables (and most Nordost cables for that matter) would fall short by a factor of 4-5 (which in Nordost prices is a factor to reckon with...) for the lengths I need in my room ; I surmised from Adam's post that we need low inductance but in reality there appears to be a lower threshold. If that is the case I definitely need to recheck before proceeding with a NAIM amplification solution. What I do know from experience with home demos with my amp is that the Nordost cables model hierarchy does lead to very perceptible sound quality improvements as you go up the ladder (low of diminishing returns applying though, which should not come as a surprise) - and this I write as a long term "cables denier".

DrPo posted:

................  I surmised from Adam's post that we need low inductance but in reality there appears to be a lower threshold. If that is the case I definitely need to recheck before proceeding with a NAIM amplification solution. 

To make it simple,  Naim amps need high inductance speaker cables,  thats what the wide spacing does.

Dr Po, you've said it had to be set louder with the Naim amplification compared to your existing integrated, and you mention <90dB. I take it that you have measured SPL with both - for clarity, would you say are the levels you found to be ideal with each? Also it might be of interest to know if the microphone is true full range, as opposed to just the one in a phone or similar? And is that reading plain dB or A-weighted? 

@IB: nothing fancy I am afraid, just using an app on my iPhone to quantify what I already "feel", I would say roughly 3-4 dB delta. I am content with Huge's explanation and will look further into the speaker cables topic before proceeding with any change.