The reviewer's reviewing system.

[Robh3606]

Just to throw another wrench in this thread, how is the above statement any different than anyone in the blind listening/measurement crowd saying those of us who choose components subjectively have an expectation bias. For every yin there is a yang and if all you do is correlate something to a measurement then you most likely will expect it to sound like that. I bring this up not to denigrate but to show that this isn't as simple as many would like it to be. In fact I consider that lack of simplicity a "fun" part of this hobby. I am also one who hasn't heard a true hi-end system lately that wasn't good unless there was something wrong ie, a cartridge misaligned, tube bad or wires crossed.

Hello Beaur

That is a great point there is no difference. There will be expectation bias that said they are not my reference system. My reference system are JBL Array 1400's which by the way also measure along the same lines. They are also a CD design except using horns for Mid and tweeter and measure very flat with falling power response. I knew what I was getting. When put up next to the Arrays they still sound just fine. When I build my own I use a very similar target curve. So yes I did expect them to sound the way they do based on past and present experience of owning or having owned previous systems of similar design and did expect to like them. Not to hard to see what speaker camp I am in.

Rob

 

[Robh3606]

Exactly - the point is which number you pick. If we do not have an unique firm reference maximum level for stereo where do you start?

Hello Micro

Why are you nit picking?? Does it really matter?? Pick 110db as long as you don't under power ideally it's simply not going to matter.

Exactly - size also means area and this means reflexion, diffusion and absorption coefficients at various frequencies - room gain. Amplifiers can put their power in 8 ohm loads - but most will not be able to put it all in real speakers!

Please explain what is going to change driving the same speaker in 2 different size rooms at the same listening distance. What is going to be different enough to change the amps output at the same measured SPL level??? Why is the amplifier going to care what size room it is in as long as it is not over driven into clipping??

Unfortunately you were not able to teach us these famous correct technical methods, just a few flawed examples that need corrections. And yes, again, the typical consumers are not as knowledgeable as "professional installers".

And we still have the problem of inconsistency of the little available data - see for example for the Revel Ultima Salon the manufacturer says 2 86.4 dB SPL with 2.83 V @ 1m ; Stereophile states 86 db and Soundstage NRC measurements says : Sensitivity: 84.25dB (averaged 300Hz-3kHz, 2.83V/1m).

What is the figure we shall pick?

How about using a little common sense and use the lowest number so if you are "wrong" all you end up with is a little extra clean headroom?? Really a 1.75db difference what do you think that is critical?? It's not significant.

Rob

 

[microstrip]

Hello Micro

Why are you nit picking?? Does it really matter?? (...)

It is really strange that someone wanting to use measurements to choose components asks why I am "nit picking"! Yes, it does matter. Anyone knowing about error propagation will understand why.

Using the "lowest" for values with a large error margin is meaningless and will lead you to an irrational and wrong choice most of the time.

We also can not ignore the price and implications of the "dB" logarithmic unit. A few dBs can mean a very different price, technology and subjective sound quality.

Concerning rooms it is all properly explained in the Linkwitz pages - it is a little more complicated than you assume, but surely can be done. For interested people I write down the link. http://www.linkwitzlab.com/rooms.htm C5 - Amplifier power to obtain Reference Level

Again, I do not expect audiophiles buying systems to spend nights carrying research and calculus to buy an amplifier "using measurements".

 

[Purite Audio]

No one needs to spend nights researching , but it is advisable to look at how the amps output varies with impedence ,and how the loudspeakers impedence varies with frequency.
They are really the only two parameters.
Keith.

 

[Groucho]

e.g. low input impedance - a problem not because of "impedance matching" so much as insufficiently large AC coupling capacitor at the output of my pre-amp or source, causing low end roll off

This happens less than 1% of the time. And curiously it is the mostly referred to example in preamplifiers.

This seems like a strange way of regarding a straightforward engineering issue i.e. turn it into a probability. Why? And where did you get your figure from? If the supposed 'probability' is low enough does that make the issue go away? And what is the significance of it being "the mostly referred to example"? Does this also invalidate it?

 

[Robh3606]

Concerning rooms it is all properly explained in the Linkwitz pages - it is a little more complicated than you assume, but surely can be done. For interested people I write down the link. http://www.linkwitzlab.com/rooms.htm C5 - Amplifier power to obtain Reference Level

Hello Micro

I hope you realize that the reference you posted is almost identical to the on line calculator I posted. Uses all the same formulas just you cant see them like you can on the Linkwitz pages. The main difference is he is changing the power requirement from the 1 watt and lowering it to value to adjust for the speakers sensitivity needed to give you an 85db output at the listening distance using the reverberate field like Toole and then adding 20db of headroom to get you up to the 105db reference level. Very straight forward of of course, right in line with well known and accepted engineering practices in the industry. No Voodoo just sound engineering. No unnecessary complications or imaginary error factors.

Thanks for helping me prove my point.

Rob

 

[FrantzM]

Hello Micro

I hope you realize that the reference you posted is almost identical to the on line calculator I posted. Uses all the same formulas just you cant see them like you can on the Linkwitz pages. The main difference is he is changing the power requirement from the 1 watt and lowering it to value to adjust for the speakers sensitivity needed to give you an 85db output at the listening distance using the reverberate field like Toole and then adding 20db of headroom to get you up to the 105db reference level. Very straight forward of of course, right in line with well known and accepted engineering practices in the industry. No Voodoo just sound engineering. No unnecessary complications or imaginary error factors.

Thanks for helping me prove my point.

Rob

lol