Replace Speaker Surrounds

[Neil WyattModerator @neilwyatt]

Posted by Circlip on 15/01/2022 11:13:42:

World of difference between Hi-Fi and Performance speakers, home use, quality sound is paramount, "Performance" speakers, LOUD IS KING.

Things are changing. These days, PA is usually both insanely loud and of exception clarity and quality.

Bass players tend to split between those who feel the speaker should (more or less) contribute to their sound, and those who go for FRFR ('full range flat response&#39 powered monitor speakers that are definitely hifi spec or in ear monitors (IEM) and use DI boxes or emulators to get their sound.

Even those of us who use a cab will normally DI, typically post-preamp.

On the other hand, guitarists remain obsessive about how their cab/speaker combination colours their sound (they like speaker ';break up&#39 and tend to mike up rather than use DI.

Back in the 90s we used backline for everything, no drum amplification for pub-sized gigs and very basic PA at a couple of hundred watts for vocals. Now we all turn down, mike up the kit and everything goes through 4kW of PA – even if the end result is no louder than the old days. My biggest issue when sound checking is turning down enough so the PA can determine volume.

So the loud in/out takes about twice as long now, and it's not just being older! But the sound quality, even for 'pub' bands is way beyond what we used to get.

Neil

[SillyOldDufferModerator @sillyoldduffer]

In my youth, hi fi was a hot topic at Radio Club. Had a good mix of technically astute professionals and interested rather than expert members from all walks of life. We were all under 35. Having access to various decent speakers, amps and test kit allowed us to do a couple of experiments which convinced me that much audio loveliness is perceived rather than technically justified.

We found blindfolded listeners have difficulty identifying which pair of speakers out of five or six possible choices is providing the sound. Also that audiophiles are easily fooled into voting for speakers they disdain! For example, allowing them to glimpse the misleadingly labelled control panel whilst being blindfolded, they would believe what the switch setting said rather than what they heard.

The second experiment tested listener sensitivity to one type of distortion. A tape deck played an orchestral piece in a loop, while a second looped on an artificial concoction of noise and random tones at the same level. A hidden operator used a mixer to gradually combine the two, and randomly added more and more distortion.  About 12 of us were asked to say when we first heard distortion in a fancy pair of headphones. One audio enthusiast detected distortion before any was applied! The rest of us were less gullible. A few noticed distortion when it reached about 4%. The worst was me, who was happy all was well until more than 10% was added. The majority couldn't detect less than 6% distortion, and this group included all the audiophiles. It seems distortion doesn't reduce pleasure in music, and I like it!

Other observations:

• No-one liked music that went straight from source to speaker through a flat response amplifier. They all adjusted the graphic equaliser. There was no common setting that everyone liked. Basically we were telling the artists, musicians and recording engineer that they were all wrong! It means personal preference matters more than purity.
• Everyone was annoyed by low-level hum, hiss, cracks and pops.
• We all preferred valve to transistorised amps. Transistor amp output sounded and looked OK on a scope when reproducing single tones from an oscillator, but real music had a sort of mushy quality.
• Mush effect may have been due to early transistors being low impedance devices. I think modern high impedance amplifiers sound much better. But could that be more to do with my ageing brain and ears? Aged 12 in the science museum I could just detect a 25kHz tone. Not now! I also used to be effortlessly good at picking conversations out in noisy pubs. That skill has deserted me too. I have to concentrate really hard to get anything. Chatting in noisy places is exhausting!

Dave

Edited By SillyOldDuffer on 15/01/2022 15:11:41

[Mike PooleParticipant @mikepoole82104]

I would think most people who are the wrong side of 60 will have noticed a significant impairment of their hearing compared to their youth. Having been a fan of Motörhead and Ted Nugent as well as noisy motorcycles I am surprised I can still hear at all. I have mild high pitched note type tinnitus and I hunted high and low for the machinery hum but it seems to be only me that can hear it. I also find conversation in a noisy environment challenging now. I still enjoy noisy cars and bikes though.

Mike

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by SillyOldDuffer on 15/01/2022 15:08:06:

In my youth, Cut

Other observations:

• No-one liked music that went straight from source to speaker through a flat response amplifier. They all adjusted the graphic equaliser. There was no common setting that everyone liked. Basically we were telling the artists, musicians and recording engineer that they were all wrong! It means personal preference matters more than purity.
• Cut

Hi, Dave, never did like graphic equalisers, bass and treble always better in my opinion, but as you say no common setting as everyone's hearing and taste is different. I did a repair on a workmate's brother's Yamaha natural sound amp once, that only had a volume control and it's sound didn't suite my taste at all, but he of course thought it was the best you could get and was over the moon when I fixed it.

Regards Nick.

[John OlsenParticipant @johnolsen79199]

I wonder if the problem with the early transistor amps that SOD mentions was actually due to residual crossover distortion? Most transistor amps were class B or at best class AB, to make the most of limited power ratings. There was a lot of work done on this about 40 years ago as MOSFETS started to emerge. Wireless World around that time described a transistor class A amplifier which was claimed to give excellent results, but at relatively low power.. If a Class B or AB amplifier is not set up quite ideally, there can be a little glitch in the waveform as it crosses over from one output device to the other, and this is a particularly harsh kind of distortion.

One problem with the transistor stuff was transient intermodulation distortion, where the early stages of an amplifier can go into overload until the slower power stages catch up. The solution is to try to reduce the reliance on large amounts of negative feedback around the whole amp and instead to try to get low distortion in each stage, as well as trying to have good high frequency performance in the output stage

The way they measured transient intermodulation distortion was to apply a fairly large square wave (but not enough to clip) along with a lower level higher frequency sine wave. At the output, the sine wave would be liable to disappear for a bit after each transition of the square wave. An ordinary distortion test with a sine wave input will not show up this sort of problem.

The first place I worked was the Civil Aviation part of the local Ministry of Transport. They used to say to us trainees that 5% distortion was perfectly acceptable, and so of course I made myself unpopular by pointing out that they were applying this to every item in quite a long chain, the mike in the aircraft, the amplifier in the transmitter there, the same in the receiver on the ground, then any amplifiers needed to drive the landline to where the controller was sitting, and his amplifier and speaker. To me the end result has always sounded like Donald Duck, and I have never been able to understand what he was trying to say either. Just as well I never tried to be a pilot! Of course this sort of thing was probably a factor in the Teneriffe accident.

John

[Michael GilliganParticipant @michaelgilligan61133]

Lots of excellent points there, John

I would just add, if I may, that there are two ‘generic’ advantages to valve amplifiers:

1. The distortion comprises mostly even harmonics
2. In overload the waveform is ‘softened’ rather than clipped.

The best-sounding transistor amplifiers are, I would suggest, the ones which best-approximate those characteristics.

MichaelG.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, I think I read something very much the same as you say about valve amp distortion, several years ago, but it was a fair while after I built my stereo valve amp that I used doing my Discos, the design was from a Babani Press No. 12 paperback and it was a design based on the "G.E.C. 912-PLUS" B.P. No 12 (Worldradiohistory.com) ( Chapter 3, page 23) It could be driven very loudly without any significant noticeable distortion and had a good overall sound. At the time I built it, I couldn't get a transformer with the power requirements for the HT and the valve filaments, so settled on a transformer for the HT through a semiconductor bridge rectifier with a non split phase output, and a separate transformer for the filaments. It got stood out it the garage after I was no longer doing Discos and suffered a bit of damp which got into the speaker output transformers and corroded some of the fine wire coils, had no reason to repair it by then and the wooden cabinet was also shoot by then.

Regards Nick.

[Author]

Posts