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Tone Controls: A topic about tone controls

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    Posted: 09 Sep 2010 at 10:55pm
Tone Controls: A topic about tone controls

Yes, tone controls! Bass and treble tone controls.

That's bound to stir up controversy but never mind...

Some people like tone controls - some people hate tone controls.

I will begin this topic about tone controls with my experiences of tone controls - that's bass and treble tone controls (but I may make mention of a midrange tone control).

My findings could be summed up as "you only need tone controls if the equipment you're using is boring to listen to" - but is that really the case?

I have heard it said that tone controls are essential for room equalization and after setting up a number of public address systems I agree.

Now, the public address systems I refer to are the equivalent of high fidelity systems but for hearing by large audiences, and not the sort for factory/shop announcements or the bingo caller, although I have done some in my time.

After installing a new system in a lecture theatre (see pic)...



...using the JBL passive Eon loudspeakers as the main stereo pair, even equipped with 18" bass drivers, and powered by a quality 400 Watt amp (40V/uS slew rate and highly stable), the sound balance was quite lightweight in the bass region. The only solution was to turn up the bass on the Soundcraft mixer until it sounded right. Yes, it would have been better to install some large bass bins but the installation didn't allow - see the chair-lift on the left of the stage? Even by installing bass bins it means there would have still been EQ in the system by placing the emphasis on bass amplification to drive them. So, to balance the room acoustics required bass EQ.



Around the age of 17 and at the beginning of my journey into audio (and electronics in general), I didn't have much of a clue about hi-fi. I bought an Amstrad IC2000 Mk4 amp. In those days any amp sold by Comet was called hi-fi. The Amstrad had bass, mid and treble controls and with them set flat it was a very boring amp indeed. Put a "smile" on the tone control "faders" and it sounded half decent but emphasized record clicks and pops to such an extreme that the off-switch became the most important control it had.

Deciding to take it (and some Marsden-Hall speakers) to my local where I was meddling with trying to make a decrepit twin deck system work, I found what happens when the tone controls are up full as well as the volume...

The speaker voice coils pop out!

I had learned about "clipping".

I suppose it was inevitable that I would later join in with the "all tone controls are bad" brigade.

But after a number of PA installs/procurements, and the one mentioned earlier, I found myself in two minds about tone controls. Using headphones a lot I would definitely not use tone controls, but after auditioning speakers in different locations, I know they can sound quite considerably different, and believe that tone controls would help. The proviso has to be that the tone controls are used sensibly and never with full boost unless the room is completely unhelpful.

To be continued...



Edited by Graham Slee - 09 Sep 2010 at 10:57pm
Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonclancy Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2010 at 7:25pm
Interesting topic, Chaps.

Let me just throw this in the ring:  "Tone Controls are a very crude form of EQ - only just above changing speaker position etc."

I'm not sure if I actually believe that myself.  I can see how a tone control might help tailor sound to the location, or indeed to the listener and individual preference.  This preference  might also be tailoring to the differences we must all have in our generic, but varying, hearing response and perceptions.

Are DSP and room correction the same thing on a more advanced scale?

Discuss! Wink



PS I don't use tone controls, room correction or room acoustic treatment.  In fact, we have an acoustic piano in the same room that is probably singing along to everything played!  Would tone controls make some love the AKG K701 if they already find it bass shy?


Edited by jonclancy - 10 Sep 2010 at 7:28pm
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Fatmangolf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2010 at 11:12pm
Good points and I agree with you about the differences between speaker repositioning and EQ.
 
In general do we want our personally preferred timbre or an idealised flat response in a real room? Most acoustic problems I've heard in venues and rooms are time related (i.e. the room resonates or rings and sustains certain frequencies and/or sucks out others which die off quickly) which are only covered up by adjusting the amp/speaker output with EQ. It depends how you feel about changing your room decor and about using EQ.
 
In guitar amps tone controls are crucial to sound shaping (if you're into valve amps think of a cathode follower driving a passive tone stack and gain make up), in other words the tone is being shaped with some distortion even at low gain. But no amount of EQ can make a small open backed speaker sound like a closed back 4x12" at high volume. Which is akin to Graham's point about trying to fill a large venue with bass when the speakers or amplifier lack the headroom. Luckily real life is about compromise and a little bass boost helps to make small speakers sound bigger, too much and it's obvious there's a problem. More so when the system is running at high volume with amps are clipping and speakers flapping.
 
Anyway back to hi-fi land. I would like to hear exactly what's on the record and have as little as possible in the signal path. That's easier with headphones and no EQ is needed. Choose carefully when you buy your headphones as you've hard wired your tone controls and more. Discuss.
 
Meanwhile in my living room with the speakers and sofa, I have bookshelves, racks of LP's and CD's, musical instruments like guitars and a TV.  And a cat which definitely can't be acoustically treated with tone controls. And some surround speakers and a subwoofer for watching DVD's, which could be used to add low bass. So I should expand Jon's room correction with bass management Wacko as an option for the topic! [Lets agree to not discuss surround sound processing of stereo, please!]
 
"Are DSP and room correction the same thing on a more advanced scale?"
Probably not. It depends if you're fixing the frequency response with some EQ or phase/delay which is most room correction usually done with DSP (digital signal processing), or adding an ambience or reverb programme to simulate being in a large concert venue which is also done with DSP.
 
My EQ comment is that a slight cut can reduce irritating peaks or tame HF shrillness, it can't fix the source. And boosting the bass or treble brings the sound of that circuit in.
 
I guess it's how far you deviate from the "straight wire with gain."
 


Edited by Fatmangolf - 10 Sep 2010 at 11:13pm
Jon

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2010 at 11:18pm
I should add that I am not advocating the use of guitar amp tone stacks in hi-fi. The classic Baxendall bass and treble is good, but I have learned from Graham Slee's Genera design how critical the slew rate and op amp loading are in an active filter or EQ. So good EQ or no EQ!
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mrarroyo Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2010 at 12:51am
The closest I have come to using tone control was back in the 80's where I used an equalizer. First a pink or white noise was generated and a mic was placed in my listening chair and the room equalized. It was a pain to do and I do not even remember the process, since I leave the controls at zero.

My only exception is on cars where I lower the treble a notch since I find the higher frequencies overdone in most car situations.
Miguel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tg Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2010 at 9:36am
As someone of my acquaintance was wont to say, "there are more points to this than on a pineapple."
I may be incorrect, but I would suspect that tone controls were initially fitted as a sales gimmick and to cover the limitations of less than "hi fidelity" amplifiers and speakers.
Philosophically, any intentional, post production, source signal modification, could be seen to be contrary to the notion of "hi fidelity" reproduction.
Practically, there can be many valid reasons for such modification, particularly in the case of large venue sound reproduction where nowadays I believe it common to use sophisticated equipment that introduces time delay to closer speakers to synchronise them with more distant placements.
In a domestic situation, I would consider speaker placement to be of the first importance and any subsequent measures to be room treatments and finally EQ in that order, in the case of integrating a sub woofer the EQ might be considered before room treatment though even there treatment is preferable and subsequent to optimal positioning.
Many speaker manufacturers have and some still do, offer adjustment of individual drivers on the speaker itself.
The purpose of all these seems to be to achieve the most desirable balance at a particular "sweet spot" in the listening room.
I suppose that could also be considered to be "being faithful to the source" by presenting the best possible facsimile at the chosen listening position.
I know of systems using multiple amplifiers to drive different speakers and sophisticated DSP/EQ systems to produce reportedly stunning results at very high volumes in large rooms.
This is not my situation, I can not listen at very high volume very often out of consideration for my neighbours, living in a smallish apartment with neighbours either side and below.
I love my speakers for their portrayal of the recording venue and their soundstaging, something I cannot get from headphones, but being highly efficient BLH with 8" drivers they are never going to load the room to the degree other types will. I also use them in an almost nearfield configuration which obviates many room related issues, the drivers are at eye level when seated app 7' from them with some distance from my seating position to the not particularly reflective blinds behind.
The unkind might call such speakers "bass & treble filters".
Still, tone controls are not something I would consider introducing to my system, having regard to Graham's previous musings on the difficulty of implementing them without penalty and my own experience of improving the sound of my system by removing my preamp entirely.
That said, I am quite happy to try different I/Cs to adjust the sound and that might be considered a form of "tone control" although I see it as finding the best matching connector to provide the cleanest signal to the next stage.
I do not see that as being markedly different to replacing the fairly basic carbon track pot in my amplifier with a stepped attenuator using quality resistors which gave a marked lift in resolution and detail (and in fact showed my preamp up as a sonic bottleneck).
It could probably be argued that tube rolling, opamp swapping and capacitor changing are all forms of tone control.
Forgive me if I seem a little scattered here, I've been tinkering with a DAC I gave up on some time ago and the latest mods have been burning in for a week now and starting to sound like it might give my vinyl front end a run for the money, will have to put on some records later for a reality check, for now though it is sounding rather good and it keeps taking my attention from what I am waffling about.
Enjoy the music - I am ! Thumbs%20Up

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonclancy Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2010 at 10:51am
Originally posted by Fatmangolf Fatmangolf wrote:

In general do we want our personally preferred timbre or an idealised flat response in a real room?


Personally preferred timbre, of course! Big%20smile  It's what I enjoy listening to.  And that will be shaped by my hearing response, taste, mood and a million other things...

Originally posted by Fatmangolf Fatmangolf wrote:

Choose carefully when you buy your headphones as you've hard wired your tone controls and more. Discuss.


I refer you to the above.  But headphone choice can be a pretty blunt instrument and although it gets you in the right area, tastewise, the sound might need a little more tweaking...
 
Originally posted by Fatmangolf Fatmangolf wrote:

"Are DSP and room correction the same thing on a more advanced scale?"
Probably not. It depends if you're fixing the frequency response with some EQ or phase/delay which is most room correction usually done with DSP (digital signal processing), or adding an ambience or reverb programme to simulate being in a large concert venue which is also done with DSP.

Agreed.  And nicely put.

Cheers

jon

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