Causes of speaker distortion

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Vulcan00

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Causes of speaker distortion
« on: 5 Sep 2013, 09:45 pm »

Other than driving speaker harder thanthe drivers can take are there any other variables that cause a speaker to distort?

I would think an equalizer could be set to drive certain freq higher to distortion. Can a room influence distortion? Any other factors.

audiotom

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Re: Causes of speaker distortion
« Reply #1 on: 5 Sep 2013, 10:23 pm »
noisy pots in the volume controls
shorting out between two adjacent speaker cables
a spitting tube that is failing

Vulcan00

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Re: Causes of speaker distortion
« Reply #2 on: 6 Sep 2013, 04:00 am »
Can  playing too loud in a smaller area room cause distortion? Or may its the ears that distort?

Good points audiotom, the source, amps, etc. can be the initiation of distortion. I tend to play the same song over periods and have experienced perceived changes in sound quality. I am just trying to understand why my perception changes. i suppose its emotional.

jsalk

Re: Causes of speaker distortion
« Reply #3 on: 6 Sep 2013, 10:36 am »
Other than driving speaker harder than the drivers can take are there any other variables that cause a speaker to distort?

There are many sources of potential distortion in an audio system. From a speaker perspective, there are four main potential issues.

Every driver has an XMAX - the maximum cone excursion possible before the driver no longer performs within specs or actually bottoms out.  But this would only occur when you are "driving the speakers harder than the drivers can take."

Another possibility is debris lodged between the voice coil and the magnet.  This would produce a "scratching" sound as the driver moves in and out.

The other potential issues relate to a failure of the driver itself.  The spider that attaches the rear of the speaker cone to the frame is glued in place.  If the adhesive fails, the driver will tend to produce a "flapping" sound.  Other damage can be a surround that has failed or come loose.  You could normally see that with a visual inspection.

Finally, the gasket material between the driver and the cabinet can fail to make a seal.  This results in an air leak and produces a sound similar to someone passing gas when the system is driven hard.  This is usually associated with large woofers.  Pressing on the woofer frame to force the driver into the gasket material, or covering the mounting holes with your fingers can stop the sound of an air leak temporarily and is an indication the gasket material needs to be replaced and the driver re-mounted.

The latter three of these would produce significant issues that one would perceive as more severe than simple distortion. 

But providing these three situations did not exist and you are not driving the speaker drivers beyond their XMAX, the source of any distortion is almost always elsewhere in the system.  A speaker normally works or it does not and it merely reproduces what it is fed.  Distortion can be produced at all points from the source to the speaker.  And once it is introduced, it can't be removed.

We have investigated many distortion issues over the years.  The source is almost never with the speakers themselves and, if it is, it is usually a case of driver failure that results in sound that is so degraded, you would not mistake it for simple distortion.  You would definitely know the speaker is damaged. 

- Jim

Vulcan00

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Re: Causes of speaker distortion
« Reply #4 on: 6 Sep 2013, 11:12 am »
Thank You Jim for your very informative post. Just for clarification the questions on speaker distortion are not related to my Salk speakers :).

jsalk

Re: Causes of speaker distortion
« Reply #5 on: 6 Sep 2013, 03:13 pm »
Thank You Jim for your very informative post. Just for clarification the questions on speaker distortion are not related to my Salk speakers :).

Well, in that case, issues like cabinet resonance and a host of other catastrophic failures can enter the mix  :lol:

- Jim

undertow

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Re: Causes of speaker distortion
« Reply #6 on: 6 Sep 2013, 03:26 pm »
Nobody mentioned the most common or actually most realistic cause... Bad amplification. If you drive an amp out of its true range in current delivery this is how speakers break up if you just take it to the edge or sound bad, or blow. Specifically if a speaker is not that efficient at low frequency reproduction which many of the "Exotic" high end speakers today can take a serious toll on how well the low frequency will drive with more basic amplification not to mention dropping really low in the impedance taxing an amp to its limits.

Its due to the amplifier overheating the speaker as it no longer has thermal control being driven well out of its range.

Many times its not the speaker causing the distortion its the deteriorating signal feeding it. Many reasons why in fact as much as many like to save a buck on the amps, they are not all equal. Not a huge Krell Fan for example, or other mamoth designed amps, but pure class A and other factors do in fact make these amps capable of power and current deliver at full gain unlike many you can buy used in the market for under 1000 dollars.

Trust me if you have ever actually experienced a very large solid state amp playing metallica at full tilt it could be shocking how much power your speakers actually do take without coming un-glued.

But again there are several factors getting to that point, quality, size of true power supply etc... All come into play. A good point here is why many end up going to Tube amps as they clip with full power at a different smooth rate.

Lots of high efficiency speakers for live pro studio gear etc... are designed for this and many use tube amps as well.

First hand unfortunately the absolute best amps I have heard, and driven to insanity are ones that weigh over 100 lbs or close to 50 lbs per channel, this is possibly just circumstance in some cases, but class A and really costly power amps exist for a reason, not just because they can charge way more, they cost a lot more to build.

Yes I built the Hypex Class D Ncore amps as well believe it or not. No way it can compare. By the way not taking a swipe at the Ncore, its a great little amp for 190 watts and in many cases just what you need. It just did not handle as nicely if you really abuse it like a 400 or 600 watt premium amp from Pass, or Mcintosh, Krell etc... But again it comes down to matching and absolute efficiency of the system in general.

jsalk

Re: Causes of speaker distortion
« Reply #7 on: 6 Sep 2013, 03:46 pm »
undertow -

Good points.  When there are problems with speakers, the results are generally more severe than what most people would regard as distortion.  Distortion issues are usually not related to the speakers performance unless the drivers are exceeding their XMAX. The problems are usually upstream.

- Jim

Big Red Machine

Re: Causes of speaker distortion
« Reply #8 on: 6 Sep 2013, 06:25 pm »
Gee, we never experienced amp distortion at an important speaker demo!
 :lol:

audiotom

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Re: Causes of speaker distortion
« Reply #9 on: 6 Sep 2013, 07:11 pm »
amp distortion

Do you want to see if your amp can handle an extremely dynamic passage?

Take the Lark amp test

King Crimson
Larks' Tongue in Aspec I  test

the opening cut
about 4 minutes in and also near the end

it completely overwhelmed one of my amps

undertow

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Re: Causes of speaker distortion
« Reply #10 on: 6 Sep 2013, 07:15 pm »
Most likely due to the amps "Input" gain capability was overdriven due to the recording being made way too high from the master in the first place in turn "Overloading it"... Many recordings are just weak and you need to turn up amps all the way, and many you can't turn up past 15% and your just killing the input due to the recording being too loud in the first place.

Some of the best amps can take a hit of 8 volts or above, most max out around 2 volts to drive amp to full power. Physical volume position in this case has zero to do with it.

By the way this theory applies to the preamp as well and could do this compression well before it even makes it to your amp from the CD or Phono stage overloading. Then of course amplifying this over even more voltage from a preamp will definitely kill the amp well before hand.

#1 thing that sucks in my book of audio... Why do recording engineers suck so bad sometimes?

Just as an idea.... Not arguing.

JeffB

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Re: Causes of speaker distortion
« Reply #11 on: 6 Sep 2013, 09:30 pm »
I am definitely no expert.  The following is based upon things I have read and things I have heard in various speakers.  The things I have read could certainly be wrong.

The need for baffle step correction -- to compensate for the power loss at low frequencies as the radiation pattern transitions from 2pi steradians to 4pi steradians. The frequency at which this occurs is a function of the baffle size.  I believe this to be a very big problem, because it depends upon both the baffle width and the distance to wall behind the speakers.  There is generally a cross-over in this frequency range also.  It seems to me that many speakers do not have a flat sounding response in a room.  It would seem that on-axis, off-axis, room power response, and speaker positioning in room all have to hit the perfect combination to sound right.  I frequently get the sensation of too much energy around the 1k to 4k frequency range.  Any type of horn loading usually makes this even worse to my ears, although it would seem that in theory it should make it better.

All kinds of refraction, from the speaker cone itself to the baffle.  There are not many speakers shaped like nOrh or Orb Audio.
The cross-over itself.  Possible phase issues here, although some people don't think phase matters much.
The box the speaker is in will affect the cone movement.  As the cone pushes into the box the box pressure increases and thus affects the linearity of the driver moving into the box.
Air inside the box, reflecting back through the speaker cone.
Box vibration and floor vibration.
Speaker basket vibration.
Speaker cone material.  Metal cones ring and have bad breakup distortion in upper frequencies that must be filtered out.  Metal often have lower distortion than paper though before this breakup level.  I personally prefer treated paper.
Speaker magnetic gap may not be consistent strength through the range of cone movement.
Inductance and impedance change with frequency and volume.  The more stable these values, the easier for the amplifier to deal with.
Box porting.  I think bass-reflex speakers exhibit an un-natural tendency to boom at a certain frequency.  This can sound like good deep bass to the untrained ear.
Cone shape effects disbursement of frequencies.  I believe flat would be the ideal, but this design is too weak and prone to flexing, and thus they are curved.

Vulcan00

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Re: Causes of speaker distortion
« Reply #12 on: 7 Sep 2013, 01:44 pm »
JeffB:

I am intrigued on your statement:

"I think bass-reflex speakers exhibit an un-natural tendency to boom at a certain frequency.  This can sound like good deep bass to the untrained ear."

Would you mind elaborating some why bass-reflex behave this way at certain frequency?

Thanks

JeffB

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Re: Causes of speaker distortion
« Reply #13 on: 7 Sep 2013, 11:26 pm »
Its just an observation of mine after auditioning some bass-reflex bookshelf speakers.  I think they tend to boom near the bottom of their range.  Some will claim this is due to room modes, but I think it is something else.  You won't hear it all the time.  It first really caught my attention when listening to some Dynaudio Audience model and I only noticed it on particular drum hit on one song.  It sounds a bit like pressure being built up in the speaker and then suddenly released through the port.  It just adds a little extra to the bass.  When I first noticed it I thought the speakers were doing something special that I hadn't noticed before.  I have since decided that it really is an error in bass reproduction.  Upon coming to this realization, I thought back upon an old Canton bookshelf I had heard.  It seemed to have incredibly deep bass for a bookshelf and yet the bass seemed ever so slightly different from what one would hear with a tower.  I am now certain it exhibited this same boom effect.  I then auditioned some Dynaudio towers.  I believe they still have this boom, but it is much lower in frequency and room modes definitely start to get involved.  I don't know if its truly an inherit flaw in bass-reflex, perhaps the right design would eliminate or mitigate this effect.  Every speaker design is about compromises, if you try to avoid bass-reflex because you notice this problem, then surely there will just be a different problem with some other type of box or open-baffle.  I bet most people won't even notice this.  I certainly don't always notice it with every bass-reflex design.  Really the whole point of my above post was simply that there are lots of areas where speakers can distort.  There is plenty with just the raw driver, but if you start talking boxes and cross-overs there are a lot more.   There is no substitute for listening to something yourself, preferably in your own home, with an extended period of listening.

Here is a couple of forum threads about bass-reflex and boom.
http://www.pinkfishmedia.net/forum/archive/index.php/t-106824.html
http://www.avsforum.com/t/1049144/acoustic-suspension-or-bass-reflex-ported

Google a bit for bass reflex transient response.  I found a pretty good description of the problem, but it was on another manufacturers web site, so I won't post the link.
Actually, I hadn't realized all this was in SalkSound until after I posted.  There is probably a better forum circle for this discussion.  Maybe the "The Lab".

Vulcan00

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Re: Causes of speaker distortion
« Reply #14 on: 11 Sep 2013, 04:32 pm »
Thank you JeffB !

I have wondered about my Ultra pre, even with the use of the lower gain button engaged, I still can not turn it up much over 1/3. This wonderful sounding pre amp sounds great with my amp but it push way too much for my amp (parasound), I'm sure it would match up much better with VA amp.

 warning: always consider synergy between equipment.