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CRXIZM
20-08-2004, 08:26 PM
I just bought a pair of cadence splits :) and when i try to crank it they start to distort befor it reaches max volume :mad: . Seeing as their new and that i got the guys at JB HIFI to install it i can't think of what has gone wrong. Any ideas guys?

BlakTegra
20-08-2004, 11:46 PM
Are you running an amp for those splits?

SIKCVC
21-08-2004, 12:24 AM
Are you serious?

All speakers are gonna do that!!! I have 250RMS running through my subs and 65RMS through my splits and I cant run them up to full volume... theyre tuned to a max of 72 (out of 80). Purly because my splits are rated at 75RMS which exceads the max of the amps output.

You can only run speakers so hard before your no longer increasing volume, your increasing gain. Or something along those lines, its been a long time since I've done physics...

The only way you can turn it up to max volume is if your power out exceeds your power in. as in, the power from the HU or amp exceeds the power handling of the speakers(its best to have it this way as its best for the whole set up). But at the same time you cant exceed it by too much otherwise it'll overpower and blow.

poid
21-08-2004, 10:05 AM
The deck may clip before it reaches full volume and introduce distortion. Or, the gains on the amp may be set so that it clips before you get to max volume on the deck.


Purly because my splits are rated at 75RMS which exceads the max of the amps output.

No, its because there is clipping either from the amp or the headunit. It has nothing to do with the speakers having a higher power handling than the amp can produce.

toE
21-08-2004, 01:43 PM
how far before max volume we talkn bout CRXIZM? half way/30%/80%??
If it is less than half of the total volume...sumfin isn't rite.
If the speakers are wired thru your HU, there's your problem.
If it's wired thru an amp, and it distorts before half-way....try swapping the speaker wires on the amps.
If all else fails....wait for Mighty Mouse to come and save the day :p

CRXIZM
21-08-2004, 02:18 PM
hey guys heres an update. i got it looked at and it was that i don't have an amp so he turned it to low amp power or somethin and adjusted the head unit so it knew it is only runnin fronts and nothin in the back. This has made my max volume about 15% lower but the distortion is gone. thanx for the tips boys

Javed
21-08-2004, 08:28 PM
It is the signal clipping from the source unit that causes this. Also premature clipping occurs when not using an external amplifier as seen in this example.

tangcla
14-09-2004, 03:58 PM
Get an amp. You'll be able to turn your speakers up louder, you'll have better bass, better treble... less clipping, too, if your headunit doesn't have (or you haven't set) built-in hihg-pass crossovers.

noodleman27
20-09-2004, 12:38 AM
turn down mid bass to reduce distortion

Fhrx
21-09-2004, 08:31 AM
Guys, with all due respect (and I mean that) some of you are on the right track but others are not even close and some advice given could actually do more damage than good. :(

Remember your headunit has an internal amplifier as well, just like those massive externals one, just smalled. It is too be treated no different to any other amplifier in the way it works. Now distortion and clipping are to different things. This text is taken from the FAQ section on my website, please read:

What is clipping?

Underpowering the sub can easily damage it if the person running the stereo doesn't realise the amplifier is beginning to struggle. This resulting damage is usually casued by the amplifier being overworked and 'clipping'.

The more technical minded explanation on clipping is that when a woofer is driven with a high powered amplifier to high levels, there will be a significant amount of current flowing through the voice coil. Since the voice coil has resistance, there is a voltage drop across the speaker's voice coil. This means that there may be a great amount of power being dissipated (in the form of heat) in the voice coil. When a speaker is driven with lots of clean power, the cone moves a great deal (in proportion to the output voltage from the amplifier). For speakers with vented pole pieces (or other types of venting), this movement forces a lot of air to flow in the magnetic gap (area where the voice coil rides). When the woofer moves out of the basket, the chamber that's under the dust cap and around the voice coil expands (increases in volume) which pulls cool air into the magnetic gap. When the woofer moves the other direction, the chamber size is reduced and the hot air is forced out of the vent in the pole piece. This air flow cools the voice coil. If a relatively low powered amplifier is driven into clipping (to a full square wave for a lot of people), a relatively large portion of the time, the voltage delivered to the voice coil no longer resembles a sine wave as it would with an unclipped signal. While the amplifier's output is clipped, the voice coil is not being motivated to move as far as it should for the power that's being delivered to it and therefore is likely not being cooled sufficiently (since the speaker is driven by a linear motor, the voltage applied to the voice coil determines how far the voice coil moves from its point of rest). At points a, b, d, e, f and h the voltage is changing causing the voice coil to move in the gap and therefore pull in fresh cool air. At points c and g, the voice coil may still be moving a little due to momentum but may not be moving enough to cool properly. Remember that during the clipped portion of the waveform current is still flowing through the voice coil. Since the displacement of the voice coil (and therefore the airflow around the voice coil) is no longer proportional to the heat being generated, the voice coil can overheat. This excess heat may cause the voice coil former to be physically distorted and/or melt the insulation off of the voice coil wire and/or cause the adhesives to fail (especially if the speaker is rated to handle no more than the power that the amp can produce cleanly). If your speakers are rated (honestly) to handle the maximum 'clean' power that your amplifier can produce, slight clipping isn't generally a problem. Severe clipping is more likely to cause a problem.

http://www.fastfoursforumscarclub.com/temp/fhrxstudios/images/amp_clipping.jpg

Then there is severe clipping (aka square wave). It always amazes me when I hear some idiot driving down the road and the audio is clearly distorted (you know what I mean). Many people drive their amplifiers into what could be called a square wave output (white line below). When an amplifier is pushed that hard, it is actually possible to drive the speaker with twice as much power as the amplifier can cleanly produce into the speaker. As you can see below, the yellow sine wave is the maximum 'clean' output that the amp can produce. When an amplifier is pushed way too hard, the signal will eventually look like the white line. The effective voltage of the white line is ~1.414 x the yellow line. This means the the total power driven into the speaker by the clipped (square wave) signal is double the power delivered by the 'clean' signal (yellow line). This means that the power is double but the cooling of the voice coil will not increase in proportion with the power increase (since the voice coil isn't moving as much as it needs to be for the given power dissipation). This will lead to the voice coil overheating. If we compared the output of a 100 watt amp (the one that's clipping) to a 200 watt amp, the 200 watt amplifier would be able to push the speaker as much as 40% farther than the 100 watt amp (depending on the frequency of the signal). This extra travel (in each direction from its point of rest) would result in added airflow around the voice coil.

http://www.fastfoursforumscarclub.com/temp/fhrxstudios/images/amp_extreme_clipping.jpg

Note: The RMS voltage of a pure sine wave is equal to the peak voltage multiplied by 0.707. The RMS voltage of a pure square wave it equal to the peak voltage. For 2 waveforms with equal amplitude (as shown above), the RMS voltage of the square wave is 1.414 times the voltage of the sine wave. If we use the example of the 100 watt amp which can produce a sine wave of 20 volts RMS, we can see that the output power at hard clipping is double the power it can produce cleanly.

The next post will be about distortion.

Fhrx
21-09-2004, 08:32 AM
Now we've done clipping, lets look at distortion.

What is distortion?

Well, to get a little more complicated, distortion is any departure from a true and accurate reproduction of the original waveform. It can include Noise, Clipping Distortion, Harmonic, and Intermodulation Distortion. These last two forms are fairly common in loudspeaker reproduction and can be reduced but not entirely eliminated in the existing technology. It would be fair to say that modern amplifier design fairly eliminates nearly all forms of inherent perceived distortion, leaving only that caused by inappropriate user settings and overloading.

Distortion is the name given to anything that alters a pure input signal in any way other than changing its size. The most common forms of distortion are unwanted components or artifacts added to the original signal, including random and hum-related noise. Distortion measures a system's linearity - or nonlinearity. Anything unwanted added to the input signal changes its shape (skews, flattens, spikes, alters symmetry or asymmetry). A spectral analysis of the output shows these unwanted components. If a circuit is perfect, it does not add distortion of any kind. The spectrum of the output shows only the original signal - nothing else - no added components, no added noise - nothing but the original signal.

It's rather amusing to see amplifier manufacturers making great claims about the advantage of the extra .001 % Distortion they've wrung out of their products, while most speakers are considered very good if they can keep such distortions below 5 %. It's true that the reduction of any distortion anywhere is a positive contribution to the goal of high fidelity, but the disparity between the two technologies in this regard points up the largely subjective nature of many such claimed advantages.

Here are some of the definitions:

Noise is perceived sounds not in the original soundtrack. Such things as hiss, crackle, pops, hum, and buzz, are typical of the types of extraneous signals described as noise. Inherent noise in the electronic processing in any sytem is measured in decibels relative to the amplitude of the original signal. Sounds perceived as noise are heard in contrast to the sound that is the object of attention. Thus, a noise signal measured at 15 deciBels below the output of Tchaikovski's 1812 Overture finale would probably not even be heard; while a slight hiss at 55 dB below the level of a soft piano passage would be annoyingly obvious.

Harmonic Distortion is a type of Distortion in which resonance or sympathetic ringing vibrations are added to the original sound to produce second and third harmonics of a fundamental tone in a way that was not present in the original signal. Choosing good Drivers and a well-made enclosure design is essential in overcoming this tendency in speakers.

Last but not least (well maybe) is Intermodulation Distortion. This is the Distortion that results when one set of frequencies is superimposed on, or is modified by, another to produce a third frequency not present in the original signal. Quantifies the distortion products of nonlinearities in the unit under test that causes complex waves to produce beat frequencies, i.e., sum and difference products not harmonically related to the fundamentals.

Fhrx
21-09-2004, 08:34 AM
Now the important bit (sorry I know it's been a lot of reading but it is important)...

Why did my speaker distort / blow?

In most systems when you hears the speakers 'distorting' it's not the speaker that is struggling, it' the amp. Speakers are quite simple devices, all they do is reproduce the sound given to them regardless of what that sound may be.

When you ask an amp to do it's job, it takes a relatively small sound wave and amplifies it before sending that bigger signal to the speakers. If you ask it to do more than it's capable of (by turning the volume up full blast), it still tries to do what you have asked, but the new amplified sound wave becomes rough and sketchy due to the amp having to clip the top and bottom of the musical wave in order to produce the amplitude you have asked it for.

Imagine for a second a weight lifter. He is on the bench doing bench presses. With 100 pounds his movement will be nice and smooth and he'll be almost faultless in his technique. Now you throw on another 300 pounds. He may still just be able to do it, but his arms and legs shake, his breathing becomes irregular and it looks woeful to watch.

You amp does the same, it still attempts to do what you have asked of it, but it sounds dreadful and you get that 'distortion' everyone talks about. And here lies the biggest problem - most people assume the speakers are dying, so they go and get a SMALLER amp and as you can imagine from reading above, the problem is just amplified (sorry, couldn't resist throwing that pun in! :p ). Anyway, it gets worse. The resulting nasty wave is then transferred straight to the speaker which tends to knock the speaker itself around a fair bit. It also causes the speaker voice coil to heat up significantly as the stays are full power for longer periods during the sound wave during clipping.

Now don't get me wrong, you can fry your speakers with too much power, but there are only two main ways to destroy a speaker. One is thermal (where the voice coil and/or the former melts because of too much current flowing through it) and overdriving (where the voice coil and former hit the bump plate on the bottom or tear the surround and/or spider(s) and pop the cone out the top).

Usually the volume is somewhat louder than one would be comfortable with before failure occurs.

Like I said, sorry about the long rant but it is important to get these things out for better understanding all round. :)

tangcla
21-09-2004, 08:49 AM
Good read fhrx :) I sure learnt something!

Fhrx
21-09-2004, 09:01 AM
Yeah sorry about going on for so long, I just thought it was important to point out dude. :D

tangcla
21-09-2004, 09:11 AM
Yeah sorry about going on for so long, I just thought it was important to point out dude. :D
no, it's good :)

Just a question. My Boston Pros clip when I hit near-full volume (for obvious reasons, duh :P) The clipping sounds as if it's got an earth leak somewhere, ie. high pitched squeal. Is that a normal sound for clipping?

Fhrx
21-09-2004, 10:17 AM
The amplifier clips dude, not the Pro's.

You sure the speaker isn't bottoming out? Just how much grunt are you feeding them with? One of our demo cars runs it's Pro's with 200 continous and even that doesn't bottom out a full song...

When you say 'squeal' could you elaborate a little on that? Sounds very strange to me.

tangcla
21-09-2004, 04:38 PM
The amplifier clips dude, not the Pro's.

You sure the speaker isn't bottoming out? Just how much grunt are you feeding them with? One of our demo cars runs it's Pro's with 200 continous and even that doesn't bottom out a full song...

When you say 'squeal' could you elaborate a little on that? Sounds very strange to me.
I've got an Alpine MRV-T320 feeding 80-odd WRMS @14.4V to the Bostons.

I'm not sure whether they're bottoming out; I DO have it highpassed (very sharply) at 50hz at the amp, and a second, softer highpass at 63hz (at the headunit). The squealing noise is hard to explain. Just sounds like a shorted speaker I guess.

Wouldn't the more CLEAN power you run into it, the less likely it will clip?

Javed
21-09-2004, 08:26 PM
That is highpassed too low IMO.

tangcla
21-09-2004, 08:32 PM
That is highpassed too low IMO.
The specs say they go down to 50hz... and I'm more in it for quality, so I like my midbass ;)

Javed
21-09-2004, 09:24 PM
Fair enough. I high pass my focals at around 100 hz. They can go down to 60, but they bottom out too early.

Fhrx
22-09-2004, 09:42 AM
Ths issue of where to cross the speakers is more about power and sound deadening than anything else. In most systems we design we use powerful amps. This allows us to cross the front mids at 50.

If you have plenty of power to control this low frequency and plenty of sound deadening to enhance the bass, cross them quite low. That way the front speakers will reproduce the majority of the sound spectrum and all your sound will seem to emenate from the front where you are. :)

tangcla
22-09-2004, 09:53 AM
Ths issue of where to cross the speakers is more about power and sound deadening than anything else. In most systems we design we use powerful amps. This allows us to cross the front mids at 50.

If you have plenty of power to control this low frequency and plenty of sound deadening to enhance the bass, cross them quite low. That way the front speakers will reproduce the majority of the sound spectrum and all your sound will seem to emenate from the front where you are. :)
yeah, trying to do that ;) more SQ than SPL.

Although 80-odd WRMS isn't exactly 'high' powered... :p