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Upgrading from NAP135

Julf said:
Yes, it is a logarithmic relationship. Every extra 3 dB requires a doubling of the power.
Click to expand...

Thanks, I think I read that elsewhere sometime, but I hadn't retained it. This is still coming together for me, so it's useful to have it pointed out.

I may post again this evening - questions on the Sanders paper in my head, and in relation to my situation re the Crown calculator.

All useful stuff.
 
nicetone said:
...

If the figures are okay, and we really did want 102dB peaks in a domestic setting - which I would have thought would be unrealistic (certainly in my setting!), but let’s say we did - then a higher margin of safety than the minimum 3db for avoidance of clipping, say 5dB, would mean 839 watts!!

... I should add, belatedly, that I appreciate that by entering 72dB and 102dB separately in the Crown calculator, you were making the same observations about the increase in power needed, in illustration of DV’s points. From merely 1 watt for 72dB to 529 watts for 102dB.
Click to expand...

Exactly. That why Roger Sanders says most of us are - at least occasionally - listening to amplifiers that are clipping.
 
From nicetone post #77

" Hi Naim2 - interesting. As you may have picked up from my posts on this thread, I’ve been having similar thoughts and been doing some reading around the subject. Two questions if I may.Firstly, just out of interest, what was your seating position at the concert? "

I sat at row 15, right at the middle of the row.

"Secondly, using the Crown calculator (thanks for the link) I’m wondering whether another way of approaching the figure to be entered in the amplifier headroom box would be to enter the allowance for peaks? I may be barking up the wrong tree, but if that were so, then using your first set of figures showing 72dB, and entering a 30dB headroom figure for the 102db peaks, the ’Required amplifier power’ calculation comes out at 265 watts. What is then interesting (to me at least) is that increasing the headroom figure to 33dB which is effectively your second set of figures, produces the 529 watts figure which you also obtained. So that an the additional 3dB equates to an extra 264 watts!? (Unless I'm missing something?)
If the figures are okay, and we really did want 102dB peaks in a domestic setting - which I would have thought would be unrealistic (certainly in my setting!), but let’s say we did - then a higher margin of safety than the minimum 3db for avoidance of clipping, say 5dB, would mean 839 watts!! "

Yes exactly, I have been thinking about this and I think the result of the calculator is 839 watts total for both channel so 1 channel is approximately 420 watts peak.

I think this is one of the reason why Naim recommends active olive system because say DBL active is driven by 3 x NAP135 then total watts is 405 watts per side (805 watts total) which is more than enough to cover the 102 db peaks with +3 db headroom.

Read on below of my little experiment last week (caveat my assumptions and method may not be the right ones )
Over last weekend I tried a small experiment in my listening room and this is the result (listening position @3.25m):
I played music @72 db then I disconnect the 8 inch driver from my SBL so effectively only the tweeter is running. Then looking at my RTA the tweeter is only producing 52db so there is a 20b difference to the woofer (woofer alone Is 72db). I think this is important because when I plugged in the number from the calculator (assuming the tweeter is 88db efficient) then for the tweeter to run 52db it requires <1 watt of amplification. When we add the 30 db peak power requirement the tweeter then we need only 3 watts on amplification. Is another Woofer is another ballgame: @88db efficient running 72db we need 1 watt of amplification but @102db we need 529 watt of amplification (3 db headroom) or 265 watts (0 db headroom).

So in summary according to the calculator:
@ 72db SPL (woofer + tweeter running) – listening position 3.25m away – 88 db 1w/1m efficient
Tweeter is producing 52 db SPL, woofer 72db SPL
Tweeter calculation
@52db SPL Tweeter power required <1 watt
@82db SPL (30db peak + 3db headroom) tweeter power required is 5 watts
Woofer calculation
@72db SPL Tweeter power required 1 watt
@102db SPL (30db peak + 3db headroom) tweeter power required is 529 watts

So total power required:
5 watts for tweeter + 529 watts for woofer (both channel) or 2.5 watts for tweeter/channel + 265 watts for woofer/channel

So potentially we can go with 1 powerful amplifier or we can go bi-amping with 1 amp for mid+tweeter plus 1 amp for woofer/sub woofer ala troelsgravesen.

http://www.troelsgravesen.dk/bi-amping.htm

what are your opinions?
 
Naim2 said:
From nicetone post #77

what are your opinions?
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Hi Naim2 - thanks for posting.

I’m intending to go to a classical concert in October, so may try a similar seating position!

I had been giving some thought as to whether there might be caveats in applying the pro audio Crown calculator to domestic hifi, but no more than that! Within my limited technical knowledge, I think you’ve correctly identified that for pro audio it would be concerned with the total wattage to achieve 102dB. So, I think you must be right in stating that the 529 watts from the calculator must equate to 265 watts per channel.

As to bi-amping, one amp per tweeter/woofer, as opposed to one amp per speaker like you have with the 135s, once again, my knowledge is limited, but, without researching it, I was under the impression that this didn’t increase the total wattage to drive the speakers. Therefore, two 80 watt amps, one for the tweeter and one for the midrange/bass driver is still only 80 watts to drive the speaker (??). I may be completely wrong on that, so if someone wants to come along and correct me, then please do.

That would mean, as I see it, that we would need either a more powerful stereo amp, or, more powerful monoblocks.

I’ve been demonstrating such a level of ignorance here that I might have just put myself off posting any further on PFM! I don’t have the time now, and may not over the next couple of days, but when I do, I’ll try to find out how right or wrong I am over the bi-amping situation.

Cheers.
 
The power amp to my woofers can deliver 1200 Watts, it also has clipping meters - I’ve never seen it clip :).
 
nicetone said:
I may be completely wrong on that, so if someone wants to come along and correct me, then please do.
Click to expand...

No need to correct you as you are quite right. Any advantage of bi-amping is down to reduced load on the power supply as the wattage available remains the same.
 
The power amp to my woofers can deliver 1200 Watts, it also has clipping meters - I’ve never seen it clip :).

@YNWOAN
What is your amplifier?
 
Had a minute and was able to track down the specs for my amplifier. The purpose is to continue (for those interested) the exploration of alternatives to the Naim 135s. Here's some info on the Innersound Electrostatic amplifier:
"The InnerSound Electrostatic Amplifier ("ESL amp") solves this problem by using a massive output stage. Each output transistor is capable of delivering 250 watts -- and there are eighteen of these per channel. As a result, it can deliver a staggering 135 amps of current with a combined power rating of 4,500 watts per channel! The output impedance of an amplifier must be lower than the impedance of the speaker, or current clipping will result. With so many output devices, the output impedance of the ESL amplifier is virtually zero. Current clipping simply is no longer an issue."
BTW, the cost of these amplifiers is very reasonable, considering the performance, not just in power, but with respect to the quality of the sound.

Markus
 
Using the Crown calculator (see link and context in post 75) for my own situation.

Seating distance of 2.4 metres.
Same same peak* level of 102dB as used by Naim2.
Minimum recommended amplifier headroom (by Crown) of 3dB.
Speakers rated at 89dB sensitivity would mean a suggested amplifier wattage of 229 watts (115 watts per channel).
Speakers rated at 86dB sensitivity would mean a suggested amplifier wattage of 458 watts (230 watts per channel).

*This peak is for transients, as observed by Naim2 at an orchestral concert and is not a continuous SPL. Even so, I’m not sure how likely this would be in my own domestic situation, though best maybe to still allow for the possibility.

The aim in using amps this powerful is to ensure that the amp won’t ever be clipping, by having sufficient headroom (power in reserve). Crown recommends a minimum of 3dB above the maximum required SPL. To go above this recommended minimum of 3dB headroom:
4dB would need 289 watts (145 per channel)/576 watts (290 per channel)
5dB would need 363 watts (180 per channel)/725 watts (360 per channel)

With the amps mentioned further back in this thread (Cambridge, Rotel, Meridian - the latter used) and 6 ohm speakers, such power ratings are achievable at significantly lower prices than premium brands.

On the Roger Sanders technical paper Tubes vs. Transistors referred to by naimnut in post 76, I accept his general thrust, and had already read much of what he covers elsewhere. However, I’m left wondering about the reference to protective circuitry in transistor amps being detrimental to sound quality. Is that likely, or is it about Roger differentiating his brand from others? Is it that his amps have so much power they are unlikely to ever clip, so don’t have protection circuitry?

Interesting stuff.
 
I don't know since I've never owned SL2's, but I thought they were a bit off the wall by design anyway relative to SBL's so it might be one of the things they supposedly do better.

I went on to NBL's and didn't feel I'd lost anything (but did gain quite a lot). I also have them off the walls bay about 4 inches though that doesn't seem much given the size of them.
 
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