Hifi sound quality with PA SPL |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5174 |
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I have measured amplifiers in addition to loudspeakers and what you are saying I have not encountered. I have measured home audio amplifiers in addition to pro audio amplifiers above 100 kHz and both will faithfully deliver the exact waveform providing neither is driven beyond their limits. Once a loudspeaker begins to vibrate anything pertaining to linear will be subjected to TS Parameters calculated results, how the loudspeaker is reacting in the enclosure at the given SPL in addition to, its surroundings. Xmax does not play a factor on the calculated TS Parameters of a loudspeaker. Home Audio speakers are not designed for high SPL use and are subjected to greater non-linear characteristics if driven under high SPL conditions than Sound Reinforcement Speakers. Best Regards, |
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Elliot Thompson
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cooky1257
Registered User Joined: 16 February 2011 Location: Wirral Status: Offline Points: 241 |
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Sound Reproduction, Loudspeakers and rooms by Floyd Toole is well worth a read
Stereophile the US hifi mag accompanies its speaker reviews with measurements-though they do tend towards the flowery prose in the subjective review part. Harman(Olive/Toole) have conducted extensive research that has established some correlation between measurement and subjective preference/quality. I think that if you just dropped a hi end hifi speaker system into any room it isnt going to do its best-I've heard too man shite dems in hotel rooms over the years-and this is the nub with PA- a PA has to deliver in 'any' room to an acceptable level of fidelity at high SPL. It is possible to get all your ducks in a row in terms of room/set-up and get a top notch PA to sound hifi-all too often though the operators hammer the system to within an inch of its life-power compression/excessive SPL, room effects and temporary threshold shift on the part of the listener fucks it up 90% of the time. I saw Laura Mvula at Brecon Jazz and the (Logic?) system was extraordinarily good-Frequency range, dynamic range and headroom in spades, it was by any definition 'hifi'. Personally I favour the honesty and over engineering of Pro drivers-note Pro isnt necessarily PA though there are components good enough to straddle both fields that will crop up in studio monitors for example. |
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MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7816 |
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One of these days i am going to my friends hi-fi show room to measure everything there is there.
There are some 8-9 pairs of boxes well over 10K per piece. I am really determined to make a pair of boxes and just leave it there so i can check customers reaction on the kind of sound i have on my mind. All those expensive boxes there sound really lifeless to me.
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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70,s hero
Young Croc Joined: 14 December 2014 Location: bristol Status: Offline Points: 637 |
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The importance of all that you say is correct however, sound reinforcement and Hi Fi (of a higher order) are slightly differing applications. I do think that the xmax is a very important engineering measurement with regards to non linearity, when we deal with high end Hi Fi, there are various factors that are known to contribute to distortion and the same can be said for sound reinforcement. as I said in my earlier post, the high currents and mechanical forces at play at high SPL contribute to a high order of distortion. The idea of high SPL in sound reinforcement and its engineering principles and how that relates to output is that given a sub driver for example, the claim of its output and efficiency is directly related to its cone travel and at a given force dependable upon many factors. the engineering principles to manufacturer say an 18 inch driver that has the preferred parameters of high end Hi Fi drivers simply do not exist. As you are aware, it is far better to employ multiple drivers using 300 watts each than one at 1200 watts. The application of Hi Fi quality sound reinforcement is a very expensive and exacting engineering challenge. Even then, we can safely say that the SPL will be limited in relation to distortion, the OP is quite open to interpretation but to my mind, I base it upon my own HiFi from a world leading manufacturer of such systems. That said there are many who can argue that the sound is not to thier taste and will dismiss what I say which is fair based upon thier experiences.
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Top banana
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
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One of the problems here is there are several definitions of linearity depending on who you talk to. The classic engineering definition is that if I put a combination of sinusoidal waveforms into an amplifying system I expect to get them out again, shifted only in amplitude and phase. Drivers don't always do a great job of this re. adding harmonics and distortion when the voice coil is driven harder. Then room effects make it worse again.
Other people tend to talk of linearity as meaning a flat frequency response. Which isn't a good use of the term in my opinion. |
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70,s hero
Young Croc Joined: 14 December 2014 Location: bristol Status: Offline Points: 637 |
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I can not explain why equipment selected at random will provide exactly the same results upon the bench however a simple scoping of any amplifier and speaker in my experience will provide evidence that a signal is present corresponding to the produced waveform.
My understanding of the idea that a quality sound can only come from my own experience which is of course going to be tilting towards what I use and own. My decision upon purchasing the equipment (my HIFI) was based upon the equipment having been used by numerous professional institutions and people and after having a demo. Adding to that, what HI FI have awarded them for the last 5 years I think thier top award and so I am reassured that the system is not based upon mumbo jumbo. Having met the founder/owner of the company I decided to look in to the engineering principles of the basic components which are the drive units and how the engineering differences would effect sound performance. From this and the 50 years or so of research and my own understanding of what has been developed, I came to the following conclusions. The overriding factors that will provide the highest quality reproduction with a bass driver in its design are as I have said before quite straight forward. The idea that the entire voice coil remains within the highest magnetic flux at all times is of paramount importance as this will provide the highest value of mechanical control and the most linear load upon the amplifier. If we look at the idea of the xmax then it becomes apparent that as a coil starts to leave the (most intense) part of the field upon a single cycle basis, the amplifier will see a reducing load due to the decrease in electromagnetism at this point. It just so happens that this part of the cycle coincides with the switching of the output devices where the coil is them subjected to a reverse in polarity. at this point within the cycle again the load that the amplifier sees is not uniform and increases as the coil re enters the full effect of the field.In addition, taken over multiple cycles, the combined effect is to concentrate the electromagnetic induced load towards the central part of the voice coil leading to localized heating and power compression, which the further complicates the load per cyle that the amplifier sees. The idea in its simplest form is to provide the highest amount of magnetic flux with the VC remaining within that flux at all times. This engineering design principle makes sense to me, aside from anything else. A voice coil that is subject to a uniform and constant high magnetic flux throughout its depth is subjected to a higher degree of control from the amplifier that one that partially occupies a lower magnetic flux. Xmax is a defining measurement of nonlinearity. The consideration is that any portion of the VC that is not subject to the full magnetic flux will effect both efficiency and linearity as at those times, the electromagnetic inductance is significantly reduced within and around the xmax measurement.
Edited by 70,s hero - 12 November 2016 at 10:41pm |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5174 |
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I've read so many Hi Fidelity fanatics focus on every formality and, cannot answer one simple question... "What is the measured frequency response of your loudspeaker?" Assuming excursion can rectify a speaker that is -3 dB, -6 dB and/or, greater at the given frequency/frequencies while remaining linear is a marketing ploy that many are brainwashed into. If a loudspeaker's frequency response in free air offers a consistent dB level (No deviation greater than +/- 1 dB) from 100 Hz - 30 Hz, comparing a driver with a high excursion figure versus a low excursion figure will hold no relevance. Only when the frequency response of the loudspeaker declines to the point there is an imbalance (Deviation ranging from +/- 10 dB from 100 Hz - 30 Hz), having a driver with a high xmax is relevant. The problem that many seem to overlook is there are lots of loudspeakers that offer a high degree of dips within the midrange to high frequency range in which, a driver that offers a high degree of xmax, will have no impact on the loudspeaker's performance at the given frequencies. Equalising the problem areas may rectify the issue. However, boosting such frequencies will bring forth non-linear behaviour patterns due to forcing the loudspeaker to amplify frequencies the loudspeaker has difficulty producing. Best Regards, Edited by Elliot Thompson - 16 November 2016 at 2:41pm |
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Elliot Thompson
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Crashpc
Registered User Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 465 |
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Well, bigger cinemas with HI-FI THX certified sound use PA speakers. Sometimes Precision Devices I found. Go figure... :-)
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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70,s hero
Young Croc Joined: 14 December 2014 Location: bristol Status: Offline Points: 637 |
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There is Hi fi and then there is Hi fi, any speaker and amp system could be considered HI fI ,its a matter of opinion, personally I have yet to be impressed by any cineama sound.
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Top banana
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B_Bender
Registered User Joined: 28 October 2016 Location: Surrey Status: Offline Points: 118 |
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It's unfair to make that original comparison really, I guarantee that if you put any 'HIFI' system into a large space not a nice warm listening room, it'd sound lost. Half of the challenge with PA setups is the space they're deployed into
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odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
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True, and a cinema is a very challenging space acoustically.
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MattStolton
Old Croc Joined: 04 September 2010 Location: Walthamstow Status: Offline Points: 4234 |
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I love doing events in cinema rooms! USUALLY (/caveat) very well treated rooms, lots of heavy drapes, and carpet often extends up wall too, well padded chairs, with plenty of bodies further absorbing room acoustic. Intelligibility is key! Some of the most acoustically dead spaces outside of studios, in my experience. Another surprisingly good big space, is the Panarama Room at Alexandra Palace. Basically a fixed marquee, with some weird domes to roof, but black wool serge drapes throughout, makes a large space very acoustically pleasant for a big rig, be it 800 peeps conference or dance mode deployment. Plenty of power too! |
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Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains" |
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