23 replies to this topic

[Shreknos]

hi guys this thread is not only to help me, but im hoping it will become a genuine go to guide for small cheap ways to maximise sq,

im going to run through some small things iv learned or heard of along the way, with hopes that some of the super nerd sq nutts can describe the reasons and effects while adding tips of there own...

- the big three, earthing through engine bay to engine, from alternator to battery, and from chassis to bettery

- running positive AND negative power cables from the battery to the amps, to avoid any noise problems, and maximise power delivery

- use sufficient size speaker cabling for speakers, spesh subs and mibass'

- use qulity built rugged RCA's

- sound deaden floor and kick panel area for road noise rejection

- sound deaden firewall for engine noise rejection

- brace door cavities properly when employing high impact midbass', not just sound deaden

- cover the bottom of the dash and any under dash exposed areas to stop notch filtering and resonances or something - supposed to be important, tho i dont no why exactly

- ensure both sides of the front stage are mirror images for equal freq responce, angles heights etc

- instead of tuning for a perfect flat responce, try for equal responces from both sides as priority

- allow head room for dynamic transients while chosing amps, and allow more power then needed

- keep gains down for reduced noise floor

- cover any feesable surfaces with foam or absorbtive material such as dashmatts etc

- make sub enclosures as solid as possible to stop resonance and loss due to weakness, through bracing

- have solid baffles for all speakers

- dont cover speakers with door trims ect



again, very brief, but important things that most sq noobs may not know,

please feel free to throw in your own, as ill be starting my own install soon, and am looking to maximise a simple stereo for once instead of having a expensive complex stereo running low on efficiency...

thank you
shrek

[Pulse-R]

I'll add a few comments in here

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- the big three, earthing through engine bay to engine, from alternator to battery, and from chassis to bettery

Alternator to battery shouldn't be necessary unless you run a lot of power, often. i.e. >2kW RMS worth of amplifiers. This is simple physics, at 'normal listening levels, you're only drawing a maximum of 30A continuous with the stereo. as long as the factory wiring is done properly, the factory earthing of the alternator should be more than adequate. Of course for the small amount extra, you can do it if you want.

Definitely 'upgrade' the factory battery wiring to chassis and engine. Other additions are inlet manifold, head and gearbox/transmission. Remeber to properly clean all paint and oil away from the connections prior to bolting them up.
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- running positive AND negative power cables from the battery to the amps, to avoid any noise problems, and maximise power delivery

Once again, it really depends on your system power. The chassis/body has enough metal in it to happily supply over 4000W continuous power to your car audio system, even if it's in the back of a commo wagon. Use the 'baby seat' bolt holes as earthing points - they have plenty of metal around them due to reinforcing requirements. Up the front, or right down the back, the bumper bar bolts are a good point to get a chassis connection. you need at least the equivalent of 2x 0ga copper to get better circuit than the chassis from the back to the front of the car.
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- use sufficient size speaker cabling for speakers, spesh subs and mibass'

From experience, I recommend a minimum of 14ga for up to 500W RMS, and bigger for more... 8ga is plenty for 3000W RMS power to the speakers.
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- use qulity built rugged RCA's

excellent!
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- sound deaden floor and kick panel area for road noise rejection
- sound deaden firewall for engine noise rejection

also deadening the roof helps to reduce traffic noise, and gives the whole car a more solid 'feel'
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Edited by Pulse-R, 05 August 2008 - 11:23 PM.

[Pulse-R]

Quote

- cover the bottom of the dash and any under dash exposed areas to stop notch filtering and resonances or something - supposed to be important, tho i dont no why exactly

not as important I think, as most of the 'problems' in car audio reproduction are associated with the foot well, console and shape of the dashboard and windscreen. If you've got nothing else to do, then try it out.
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Quote

- ensure both sides of the front stage are mirror images for equal freq responce, angles heights etc

the biggest hindrance to this important point is the steering wheel, and the fact that very few modern cars are symmetrical in the front area.
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- instead of tuning for a perfect flat responce, try for equal responces from both sides as priority

definitely! A smooth response is more important than a flat response, and even as little as 0.5dB difference from left to right can be audible in a critically tuned system.
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- allow head room for dynamic transients while chosing amps, and allow more power then needed

not the cheapest advice, but certainly good to note. Also to note is that all amps aren't created equal, and some amps will only deliver high power into low impedance (ohms) load.. A good amplifier should be able to deliver its rated power into 4 ohms, at 12V supply (or lower), and with less than 0.1% distortion. any amp that lists a 'peak power' should be avoided.
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- keep gains down for reduced noise floor

any decent amp will not have noise - even with the gains wound flat out.
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- cover any feesable surfaces with foam or absorbtive material such as dashmatts etc

In general, this is a good idea, although some reflected sound can have a positive effect on the SQ - such as stage width and height. The biggest reflector in the car is the windscreen, and you can't really cover that with padding. Also to note is that 'overuse' of padding, etc, will make the car sound too 'dead' - there should be some ambience in the sound.
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- make sub enclosures as solid as possible to stop resonance and loss due to weakness, through bracing
- have solid baffles for all speakers
- dont cover speakers with door trims ect

I totally agree!
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[Damon]

My first submission:

If you want a speaker to sound like it is coming from somewhere - put it there!

In other words, no amount of time correction, angling or other trickery can truly fool you into thinking a speakers is somewhere it is not.


Second submission:

Sub bass IS directional!

In other words, sure, with a constant sub 80Hz tone you'll have a hard time discerning the point source of a subwoofer, but music does not work like that. To prove this, simply replace your boot mounted subwoofer a small subwoofer in the passenger's foot well running from the same amplifier and crossover. You'll note immediately that the bass is now up front. - see submission one.

[br85]

Damon, on Aug 6 2008, 07:49 AM, said:

My first submission:

If you want a speaker to sound like it is coming from somewhere - put it there!

In other words, no amount of time correction, angling or other trickery can truly fool you into thinking a speakers is somewhere it is not.

Certain playback methods are supposed to do exactly that! Stereo can (but we cannot achieve stereo in a car), ambiophonics can (we can achieve it in a car, but i'll be stuffed if i'm gonna rip up my dash to try it), mono can (but I think mono makes modern music with no natural revereb sound "dead").

But in essence, you're right. out of the millions of people with car stereos, probably only a small handful have achieved a sound where the speakers cannot be located by ear.

Quote

Second submission:

Sub bass IS directional!

In other words, sure, with a constant sub 80Hz tone you'll have a hard time discerning the point source of a subwoofer, but music does not work like that. To prove this, simply replace your boot mounted subwoofer a small subwoofer in the passenger's foot well running from the same amplifier and crossover. You'll note immediately that the bass is now up front. - see submission one.

This is not entirely accurate, it is not the sub frequencies that are locatable, it is the resonances in your car. anything below ~350hz is not locatable by ear. What your brain is doing is hearing that the resonance (higher order harmonics btw, above 350hz) from "panel X" or "seat y" or "whatever z" is louder than some other resonance, and your brain locates the sub at the point where the panel vibration is strongest. This doesn't mean you deadened you car poorly, it would take INCREDIBLE amounts of deadenin to fully hide a sub's location, but I assure you that sub bass itself is not directional.

[Pulse-R]

Getting the time, phase and polarity of the sub correct in relation to the midbass is the key to 'up-front' sub bass. Of course, the best way to solve this problem is by putting the speaker in front of you.

br85, on Aug 6 2008, 09:57 AM, said:

anything below ~350hz is not locatable by ear.

I have to disagree here on a technical point.

The ears are sensitive to phase differences up to about 1kHz (ref: Rumsey, F., Orchestrating Automotive Audio, J. Audio Eng. Soc., Vol. 56, No. 4, 2008 April).

From the midbass and subbass at the crossover frequency, the difference in arrival time, or phase, of the lower frequencies is what determines the 'apparent source' of the subwoofer

Resonances are important cues, and the only resonances should come from the music. i.e. if the sub is playing 40Hz on a double bass, then there will be natural harmonics at 80, 120, 160, 200 Hz... and beyond. If the peaks and troughs of the subbass is not aligned correctly in time with the midbass, then you will hear that the sub is not in front of you with the other speakers. You need to have all the speakers aligned acoustically to get true imaging across the audio spectrum.

[~thematt~]

If you can replace 'Sound deaden' with 'Acoustically treat', I would very much appreciate it. I just dont have the energy at the moment to drum up my speech on why Sound Deadener is such a waste of money when using to eliminate road noise, but just note that it pretty much is.

As to Damon's comment on localizable subbass, I agree. I'll add to that though that ALL speakers NEVER just play the information fed to it. If you send 20-80Hz to your sub, your sub will still play (audibly) tones right up to ~300hertz. Its called harmonic distortion, and is very localisable (especially when combined with resonance).

There is a study out there, cant remember the name, that actually demonstrates frequencies down to around 100Hz can be localizable too. Might have to dig that up.

This is the only one I disagree with:

Quote

In other words, no amount of time correction, angling or other trickery can truly fool you into thinking a speakers is somewhere it is not.

This simply is not true. Proper Stereo reproduction does this, and does it well. Its called Phantom Center, and its what we try to aim for in our cars (albeit we fail..)

Keep in mind the ultimate aim is to remove the speaker from the reproduction altogether, so you never know where it is (audibly).

[Shreknos]

please do take the time if you dont mind Matt to expand on ur statement on sound deadener, and alternatives i may employ before i order mountains of it...


cheers charlie

[Damon]

Oh no, can open, worms spilling out everywhere...

LOL

Regardless, my own personal experience in all the cars I've built has left me with the opinion that placing a speaker where you want it to sound like its coming from is the first step of getting things right - hence it fits the theme of this thread's original purpose.

Edited by Damon, 06 August 2008 - 06:40 PM.

[~thematt~]

Damon, on Aug 6 2008, 04:37 PM, said:

Oh no, can open, worms spilling out everywhere...

LOL

Regardless, my own personal experience in all the cars I've built has left me with the opinion that placing a speaker where you want it to sound like its coming from is the first step of getting things right - hence it fits the theme of this thread's original purpose.

I can full understand the intent of this statement, but I still disagree. Here's why. Anyone who asks where should they mount their speakers, doesnt have the knowledge to pull off kick panel installs, so you'll never get proper height, hence with that, I agree.

However, I dont think its practical to put a center channel in the middle of my bonnet, and a left/right channel both around 3-4 foot outside the boundaries of my vehicle. Thus my disagreement. I put the speakers where they should go, and utilise physics with driver/enclosure/environmental interactions to give me what I need.

Shreknos, on Aug 6 2008, 03:49 PM, said:

please do take the time if you dont mind Matt to expand on ur statement on sound deadener, and alternatives i may employ before i order mountains of it...


cheers charlie

Just a quick one Charlie, 'cause god only knows most people will skim over it when its too long!! (I've typed it up before, so a quick search will give you more details).

Sound deadener is a Mass Loaded material that is purely designed to move the resonant frequency of the structure it is attached to, in order to limit sympathetic vibrations (resonance). Add that mass with anything (including wet sponges, or dirty laundry) to the same structure, and you will achieve the same result. Sound Deadener, like Dynamat, is fit-for-task in that it is well designed for the Car environment (heat, longevity, sticky backing...), but you need to remember, that task is damping vibrations, not acting as an acoustic barrier.

If you want to lower outside noise inside, you need to employ different methods. One is to block the incoming sound, the other is to absorb it. Sound Deadener is useless as both. Jump onto google and look up 'Acoustic Absorption Coefficient' to get a list of materials that absorb well. Type in "Acoustic Reflection Coefficient" to find materials that reflect well. Using a combination of both will benefit you the most. Just remember to seperate the material from your car chassis (using something like foam) in order to prevent vibration transfer through the medium (which will negate its effectiveness).

In Sound Deadener's, the ONLY part of the material that actually attempts to limit the incoming sound is the aluminium backing, and thats only a few mil (thou' inches) thick. Want to do better for cheaper? Buy 1mm thick aluminium, and put it in your car. Costs a fraction of the amount.

Sure if you put 8 layers of deadener on there, it will be effective. But its about as effective (and costly) as putting 1000 tweeters in your boot to recreate subbass. Right tool for the job, first time. Personally, I'm going to be adding Lead throughout my vehicle. And I aint paying more then $200-odd dollars for it.

Edited by ~thematt~, 07 August 2008 - 10:51 AM.

[Luke352]

~thematt~, on Aug 7 2008, 10:48 AM, said:

If you want to lower outside noise inside, you need to employ different methods. One is to block the incoming sound, the other is to absorb it. Sound Deadener is useless as both. Jump onto google and look up 'Acoustic Absorption Coefficient' to get a list of materials that absorb well. Type in "Acoustic Reflection Coefficient" to find materials that reflect well. Using a combination of both will benefit you the most. Just remember to seperate the material from your car chassis (using something like foam) in order to prevent vibration transfer through the medium (which will negate its effectiveness).

Some previously found links for those lazy people.

http://www.signal-pr..._data_solid.htm

http://interactivesonicspaces.interfaculty.../reflection.htm

[2LOUD2OLD]

~thematt~, on Aug 7 2008, 10:48 AM, said:

Personally, I'm going to be adding Lead throughout my vehicle. And I aint paying more then $200-odd dollars for it.

lead, me thinks your car is going to be rather heavy

[~thematt~]

Car's are for stereos.

I spent 90% of my time listening in the driveway. Plus, fuel is expensive.

Therefore weight doesnt matter

[br85]

~thematt~, on Aug 7 2008, 11:05 PM, said:

Car's are for stereos.

I spent 90% of my time listening in the driveway. Plus, fuel is expensive.

Therefore weight doesnt matter

One must ask, then, why you would bother to use all that lead to block out road noise when 90% of the time, you won't have it?

Edited by br85, 08 August 2008 - 12:22 AM.

[br85]

Pulse-R, on Aug 6 2008, 10:29 AM, said:

I have to disagree here on a technical point.

The ears are sensitive to phase differences up to about 1kHz (ref: Rumsey, F., Orchestrating Automotive Audio, J. Audio Eng. Soc., Vol. 56, No. 4, 2008 April).

From the midbass and subbass at the crossover frequency, the difference in arrival time, or phase, of the lower frequencies is what determines the 'apparent source' of the subwoofer

Resonances are important cues, and the only resonances should come from the music. i.e. if the sub is playing 40Hz on a double bass, then there will be natural harmonics at 80, 120, 160, 200 Hz... and beyond. If the peaks and troughs of the subbass is not aligned correctly in time with the midbass, then you will hear that the sub is not in front of you with the other speakers. You need to have all the speakers aligned acoustically to get true imaging across the audio spectrum.

I understand exactly what is being said, and the point I made was that sub bass is not directional. Harmonics are, yes, resonances are, yes. I simply stated that sub bass is not directional. Maybe I shouldn't have said so since in a car, we DO have all the other factors to think about, and so we have:

"sound coming out of our subwoofers" is locatable.
"subbass itself (<100hz)" is not locatable.

also, properly implemented rear channels (20ms delay, bandlimited, Hacked up L-R, mono, ambio signal) or center channels WILL make a soundstage much wider than actual mounting positions allow. Much more so than time alignment can. Actually, I tend to find that the more focussed my phantom center is, the more narrow my staging seems using only L/R time alignment.

Edited by br85, 08 August 2008 - 12:30 AM.