What is your opinion of the efficiency of a speaker and how it relates to sound quality. As most speakers are about 5% efficient, meaning only 5% of electrical energy sent to a speaker is converted to acoustical energy that we hear. The rest is dissapated as heat in the coil . Wouldn't it be desirable to have the highest efficiency so as to reduce amount of power needed, thus preventing excessive heating of the voic coil, and producing better sound quality. Maybe in subs its not as critical, as low efficient subs are needed to create low frequences. But wouldn't a higher efficient sub produce a better sound???

If speakers are only 5% efficient, wouldn't 95% we wasted not converted?

Phil

sorry just edited!!!!

I knew what you meant anyhow.

phil

Speakers aren't even that efficient.
Your average 12" driver is lucky to be even 1% efficient!

Many people claim that high efficiency drivers (~95+ db) produce better dynamics.

it's not only heat, but the mechanical losses in the suspension and friction, impedance mismatch, etc...

a fair bit is lost in distortion also (even at non-distorted levels, due to resonance modes of the cone/suspension).



edit: by impedance mismatch, I was referring to both amplifier/speaker and speaker/air... both are mismatched points...

It is always a trade off.



Pro-audio drivers GENERALLY have a flatter apex (cone angle), and therefore the cone breakup modes occur earlier in the frequency bandwidth. They normally use light cones and motors and are therefore more efficient than car audio or home drivers.



The difference is, pro audio driver are meant to play through the cone mode breakup, but because they are less rigid, the distortion is less severe. Car audio drivers use a more rigid cone (steeper apex) and therefore suffer cone breakup later in the frequency bandwidth. To help with this, most cones are doped to lower the FS (added mass), they can be reasonably efficient, but are not meant to play through the breakup modes, although they often do.



Home audio drivers have the most rigid cones and usually a small xmax. These have a limited bandwidth and spl, however are the most accurate.



Please remember these are generalisations there are many drivers that cross over these "boundaries".



Your best efficiency gains can be had by using a proper baffle (separate/delay the back wave from the front) and a wave guide as Pulse-r alluded to (impedance mismatch)

Exactly. Guys on here should be looking at the many Pro 8inch and 10inch drivers on the market. Instead of making pods for multiple smaller car woofers a single larger woofer will do a better job.

Its funny how people like DD Phil always say its better to to run fewer woofers for example 1 expensive sub than two cheaper subs. Yet he then says he installed half a dozen 6.5inch drivers in the doors for extra volume!! Cant get any more hypocritical than that, considering the wavelengths at higher frequencies are much shorter you'll fill the car with nodes and anti nodes.

Though its in DD Phils best interest to tell people a single high end woofer is better, as he sells high end woofers. Its a shame that so many people believe this rubbish.

I am VERY sure DD Phil doesn't require (or probably want) my help, however this is false.



Nodes and anti nodes are a direct relationship to frequency versus cone diameter.



If you have multiple drivers playing the same frequency they are called an array.



Two 6.5 drivers close together simply represent a "oval speaker cone". Therefore they can be used to control directivity, because at a certain frequency range they produce a "barrel shape" dispersion versus a cone of a hemi-spherical dispersion.



By orientation of the array you can achieve MUCH less node and anti node (lobing) in the preferred dispersion.

Err someone failed year 12 physics?

Nodes and anti-nodes are when two wavelengths are added or subtracted ontop of eachother. Unless every driver has the exact pathlength to the listens ears then you will get nodes and antinodes.

As the frequencies become lower the wavelength becomes longer. A 30hz test tone has a wavelength of over 10 metres. So if you placed one woofer 5metres further away than the other woofer then even if both woofers were in phase the listener would hear nothing as if the speakers were out of phase. If you placed the second sub woofer 5cm further away than the first woofer the bass would increase as the cancelation would be less than 1% and the increase due to the extra woofer would far outweigh this.

For example say you had two drivers in one door. One driver would be slightly further away from the listener. Lets say it is 5cm difference between the two drivers in the single door.

Now with the midbass drivers in the door which have a 5cm pathlength difference if you played a 3500hz test tone on one channel you would hear NOTHING!!! Yep even though you've added a second woofer expecting it to be louder you have lost ALL of the sound at that frequency. With three or even four drivers in the one door with all different pathlengths you'll have nodes and antinodes at all kinds of frequencies. That combined with having two doors will be a disaster. If the listener moved their head a couple inchs forward all the frequencies of the nodes and anti-nodes would change so it would be impossible to use an equaliser. Not to mention it would colour the original sound.

With bass frequencies though the problem does not exist you could run multiple subs and even if they are a few inchs difference in path length it would make no difference if you moved your head or not.

Basic physics



A radiating driver can simply be thought of as many single points. When the frequency length becomes the same or smaller than the distance between the two most distant points, it starts to create nodes and anti nodes. An example might be a 8" cone would start form these at around 1.7 kHz and up (beaming)



Now if we were to have two of these 8" cones adjacent to each other, it would beam around 1.7 kHz across the width, but across the height it would beam at 860 Hz.



A 6.5 driver has a cone diameter of 0.132 m so the beaming frequency (nodes and anti nodes) would be 2.6 kHz. now two of these in an array would be around 1 kHz (because of the flange diameter, the cones would be about an inch apart). Neither of these frequencies present a problem in the 60 -250 Hz (mid bass) range.



Sure if your trying to use 1 kHz, but even then it can be used to your advantage by controlling the floor to roof reflections.

Have a good look at all the serious SQ cars in IASCA competition. 1 pair of midbass drivers, 1 pair of tweeters or horns, 1 or 2 subs. Very rarely will you see 4 pairs of midbass drivers in an SQ car and for good reason, they generally make things worse. Its easier to make one pair of speakers sound good than it is to make 3 pairs of speakers sound good. However, more money can be made from selling midbass drivers and most car audio systems have little do with sound quality.

Next time you go to a live outdoor concert, (which most people are trying to emulate..IE SQ) take your eyes off the stage and look at the speakers.



Yep arrays..do me a favour and count the midbass drivers.





But live concerts don't count as Sq???????????????



When I see these competitions being held in car audio (IE a moving vehicle test) then I might pay attention. Until then they are "home stereo's" stuck in a car. I am sure they sound great ...parked.

So how does the nodes and anti nodes affect the sound that you hear, is it cancellation or do certain frequences drop off at certain db

Nodes and anti-nodes is simply combing (summing and cancellation)



They are the prime precursor to off axis response.(or lack thereof)



Personally there are "bigger fish to fry" in a car, however as mentioned, you can use them to your advantage (directivity control)

and I used to have 2x 10" drivers in the hatch, and had problems which could only be overcome by changing to a single driver, placed in the centre of the car. The problem was PLD and IID related. now with a single 12 in the centre of the car - problem solved.

Which is why most concerts sound average unless you are dead centre in the middle.


God no!!

They only sound decent as the speakers are worth $500,000 running off amps with 0.0001% distortion.


Spot on!!

You can however add extra subs while still retaining excellent sound quality. Of course if i was selling expensive subs that most people could only afford a single woofer, I too would be spinning crap saying that a single subwoofer is superior!

Actually no.



They maybe more visually pleasing and have better atmosphere (crowd), however all amplified concerts are in monophonic, (OK Roger Waters use quadraphonic) so the seated position is far less relevant for the sound.



(Goes on and on about the duplicity of using stereo to recreate a monophonic image )

I'm not sure how bringing me into this is anywhere near relevant to this topic.

However as you did, here's a list of a few of the top SQ competition cars I've built and what they used:

Alfa GTV - built 1993
2x Polk MM 4" sets
4x Infinity 6.5 midbass
2x JBL 1500Gti - isobarik, ported
Soundstream Class A 6.0 and 3.0s

Lancer GSR - built 1995
Boston 6,4,1 custom passives
3x JL 10W6
Audio Control - EQ, X/O
Soundstream amps

Walkinshaw Commodore - built 1995
USD Horns
4x Boston Pro as midbass
4x JL 10W6
Soundstream amps

EF XR8 - built 1995
Boston Pro 5" set
4x Boston Pro 6.5 as midbass
3x JL 12W6
Alessis EQ
Adcom x/o line drivers
Adcom amps

Mazda 323 - 1996
MTX Black Gold 6/4/1
3x MTX Black Gold 10"
1x MTX Black Gold 2 channel
massive custom passive network.

VL Walkinshaw - built 1996
Boston Pro 6/4/1
4x Soundstream 10s
Adcom processor
Adcom amps

Integra - 1999
Veritas Horns
Dyn 9" midbass in enclosure in front floor
3x JL 12W6
MTX amps

Mazda Astina - 2000
Dyn 1/5 in kick
Dyn 7 in door
2x MTX 15
MTX amps

WRX - 2001
Veritas Horns
Focal 6.5 midbass
2x Focal 13"
4x MTX 2300 amps

Pajero
Front
2pr Focal Audio tweeters
4x Focal Audio 6W mids
4x Focal Uptopia midbass
Rear door - Dyn 220
Cargo area - Dyn 220
3x rack mount EQs
Rack mount X/O
8x MTX amps

I've built hundreds of other cars without the intention of winning SQ comps, one I really liked used:

BMW coupe
Veritas horns
6x Dyn 7" midbass
8x MTX 10s
8x Signat amps

I also put sixteen 15s in an Excel, twelve 15s in my Swift, ten 10s in an Excel, five 15s in an Excel, four focal 13s in a Bluebird, the list goes on.

None of this changes that fact that a single $800 woofer is normally a better option than two $400 woofers.

Nor does it change the fact that one $800pr of mids is normally better than two $400 pairs.

Or that if you are chasing a tonne of midbass, you probably need more than one pair.

Phil

I maintain that using multiple subs in an open cabin (hatch or ute) will induce PLD distortion related to the difference in distance from each woofer to the listener.

unless you time-align each woofer separately.

even as low as 60Hz, two woofers 30cm difference from you can be heard as two wavefronts - can be annoying in SQ installations.


if the woofers are in the boot, then that will form a band-pass situation, and the waves are averaged at the back seat.

I wonder if you are assuming an opposing standpoint merely to defend your position or whether you really believe this pseudo scientific claptrap.



Last time I looked the interior of my car was at best 5 feet wide and about 10 feet long. Quite a bit smaller than the average concert venue which I imagine would be in the order of several thousand times larger. I guess this is why they use multiple drivers, in order that the patrons can hear the music,but perhaps your idea that they sound superior regardless of enviroment could be true also.



I don't recall talking about live concerts relative sound quality, I was talking about car audio, you know, reproducing music inside cars. But, I guess taking my comments totally out of context to make yourself into an 'expert' is fair enough.



Your last comment has me a little confused, due to its somewhat ambiguous grammar, but I think the point youo are making is that car stereo sounds bad when you are driving down the road, and that car audio competitions have no validity because the car isn't moving. I can only speak for myself but my system is tuned so it sounds just right when driving along at 60 odd k's an hour, my normal metropolitan speed. To suggest that car audio systems are home audio systems in cars is a statement of such breathtaking ignorance that I will leave it unchallenged. You last comment regarding car audio sound offs being held in moving vehicles has some validity, but I think anyone with a few funtioning brain cells can see several dozen fairly serious impediments to running a competitive sound quality competition using your format.



Nonetheless, I am always amused by your posts and your grasp of techical audio related matters so please don't let my small dose of reality stop you from entertaining us all.

mate, clearly your a beginner, so i will go easy, but dont insult the man because you dont understand.



little hint, everything we do in audio can be explained by math in some form or other. if we cant explain it with math, its likely that its a limitation of ourselves, not the math.



and i do believe you have taken his last comment the wrong way. he is simply saying that car audio is the same as home audio, its all based upon the same principles

The logic clearly escaped you.



The sound you are trying to emulate is a live concert in your car?



Multiple drivers must be bad for SQ?



Yet the very thing your trying to emulate is using multiple drivers.







This "holy ground" on limited point sources has got to stop.



I will take the "high ground".



Monophonic is king, especially with a full range driver.

It must be right?



Stereo is total crap because it has multiple sources.



There is NOTHING wrong with using multiple mid bass in a car (Infact there is a lot of good points)



The further you move away from the same space as the recording was made, increasing the amount of sources becomes necessary.



IE

monophonic is king of live concerts

Stereo can cope with a close replica of that space

3.1 can cope with less of a replica

5.1 etc



I could go into ambiphonic, quadraphonics, ambisonics and VBAP.







I will try to keep this to monosyllabic words.



A car moves.

This makes noise.

The "sounds" need to be loud to hear it.

70 dB is a BMW at 100 Km

Your car is much noise than BMW

You need 100 dB plus at 100 Hz to hear it.

One 6.5 driver is too quiet.



Got it?



Arrays have their place, especially in a car.



This is meant to be about efficiency, using multiple drivers CAN be more efficient if the circumstances warrant it. An example might be the use of kicks as a wave guide to decrease the acoustic impedance mismatch, where arrays might make use of this, and a single radiating driver may be too cumbersome to install.



In a door it may be better to use multiple 6.5 " drivers, over say a single 8", if the 8" could not be installed properly.



One thing I do know,(install pictures) is very few people make a proper baffle for their mid basses,

DD Phil at least demonstrates that he understands this principle, and gained around 12 dB, compared to the 3 dB I note most people obtain. A suitable flat baffle is the simplest form of a wave guide.

If the drivers in the door were at similar path lengths and were limited to below 1000hz then cancelation would not be a problem.

Notice the installs DD phil listed has dedicated midrange drivers and only a single driver per side? Thats because there would be HUGE cancelation issues if you had multiple drivers playing up to 3000hz.



A single 8inch driver will be MUCH eaiser to install than two 6.5inch drivers. In fact in my situation my 10inchers are easier to install than a pair of 6.5inchers. You cant keep mounting the drivers further along the door as the pathlengths would be different.



Or if you are chasing a tonne of subbass, you probably need more than one woofer.

Your preaching to the converted (Me)



However not everyone can (or will) cut their doors.



Actually you can keep mounting mid basses along the door, infact you can mount them in the rear doors, because of the "zone of confusion" (Assuming up to 250 Hz)



A 250 Hz wave is approx 4 feet long. For you to locate this, requires an audible time difference from one ear to the other. Directly in front (or behind) of you this is no real problem. At 500 Hz you can pick 1 degree with ease. (1 Milli second) However perpendicular to your sight, the wave must be short enough for your head to diffract it to create a time difference. So the mid bass is at your side, and at 4 feet your head diameter is simply too small to cause a 1 millisecond difference. (Unless your me, and as most of my opponents would suggest I am too "big headed" )



The "secret" to this technique is to use an accelerometer to find and reduce resonance which normally betrays the mid basses true location.

I must thank all who have replied, the information supplied here is very detailed and its good to see people treat the physics of car sound with a great deal of respect. Its just sound quality is i suppose subjective. What you like or have experienced can be quite different to another person, and no mathmatics in the world is going to tell which system sounds better than another. Thats not to say it won't point you in the right direction.
The thing with forums is the capacity to learn on an informative basis, and the ability of having constructive criticism, which creates great discussion. Occasionally the original discussion changes into other issues.

Please read the original post. I basically wanted your opinion on efficiency of a sound system to improve quality. I believe more signal voltage to amps is critical, because the amp does not run to its full potential so as to run more efficient. i.e less heat, more sound quality. more efficient speakers. less power to achieve loudness, less power means less heat. Efficiency in a speaker is also related to the mismatch in air, and is regarded as the weakest link. More technology in improving rigidity with lighter materials will be interesting to see in the coming years.

Please feel free to say that i am wrong as i am TRYING TO LEARN. But please back up your statements with some form of example or justification. Cheers!!!!!!

Apologies proaudio,



It does get annoying with some poor information.



I guess inefficiency is simply converting energy into something other than it intended purpose. Normally this is heat. Losses on cable resistance etc are often unavoidable, so the first place I went for (the jugular) is the speakers were 95 % of the energy is converted into heat.



The signal voltage to the power amplifier is important, however probably not for the reasons you have suggested. The power amplifiers mission in life is to multiple the signal by the gain you specified. (OK it was also designed to create long forum arguments over which one sounds better ) If you multiplier is a higher factor,(gains set higher) it will draw more power and create heat (loss). But this needs to be balanced against a higher input voltage (lower gain setting) and the head source creating that voltage with more loss (heat)



IE which power amplifier is more efficient: the head source versus the power amplifier. I recommend a higher signal voltage, to reduce gain block multiplication of signal noise. But not for efficiency reasons. So SQ wise, higher signal voltage is an advantage.



Can I rant about how inefficient:

passive crossovers are compared to active?

How about high resistance power supplies?

Arguing on the INTERNET with people who are closed loop?





Back to drivers (groan?)



A larger mass is less efficient, and is not able to follow the transient curves with the accuracy a lower mass would allow. From an SQ position, it is better to use dedicated drivers to handle various frequency blocks, than to use a "one driver" covers all.

On what basis do you deduce that?











Thanks for keeping things simple for me, it really does help. Just a few things, how is it you decided that my car isn't a BMW?



Secondly, you are again completely right in your deduction that any car other than a BMW needs at least 100db and multiple midbass drivers to make the audio system audible at 100kmh. I guess I have been a victim of hallucinations all these years when I was driving along thinking I was listening to my music when in actual fact it is an impossibility to hear it at 100khm. Do I feel stupid or what!



Imagine all those poor saps in their Falcons with the factory system driving along thinking they are listening to the radio when in actual fact they can hear nothing but road noise. I hope this doesn't get leaked to the wider community, it will be a scandal!



Keep those revelations coming abmolech.

The BMW I mentioned has double glassing, sandwich decoupled firewall etc.



Since a 6 mm thick glass attenuates 22 dB at 125 Hz, it isn't rocket science to deduce the main limiting factor in the vast majority of road vehicles is going to be their windows.



At 70 dB noise floor your would require a level of 80 dB to cope with it, and enough headroom. It is entirely possible you have such a car and listen to modern music with 3 dB dynamic range. I would not consider such a person as SQ.



The primary noise from a moving vehicle is in the 50 to 250 Hz range, this mainly effects mid bass.











I suspect that question is better answered by someone more qualified.



Unless we are willing to exchange our glass windows, most of us have to deal with a high noise floor, efficient speakers are going to be a must, and generally these will have a lowest mass possible, and therefore follow the input with better results.

The caveat is they will have a limited bandwidth, so three way fronts would be mandatory.

I openly admit to being a bass-head. I love it loud.That said, I've done some cars in the last few years that have had more than enough bass from one woofer. Andrew's Prelude did 149dB at 42Hz. That's more than enough output.

Phil

My car's on-road SQ is quite good - although as Abmolech stated, suffers losses in the 50-250Hz region due to road noises. Imaging and staging is still quite good, from the midrange and up.

efficiency and performance often are opposites in audio. No point having a 90% efficient system if it sounds like poo.

How dare you post that on an SQ forum, shame on you.



Next you will have people saying they prefer to hear bass.



If you take time to observe the Gothic cathedrals, you might note their outstanding acoustic properties in a VERY important field. Yes you guessed it, to get men into the churches they had one purpose in mind, BASS. Funny how they realised males love bass.



The reason males love car audio? The transfer function in a car, gives them the bass hit they desire. By all means built a front stage to go with it, Guarantee you will love it.

I've assembled some of the biggest front ends around, don't worry about that. A system needs to be balanced to be truly awesome.

Phil

Im running 4 midranges with only SQ in mind...



Running 4 legatias in an MTM setup. I offset the tweet (supremo) and still run it fairly low to avoid lobing. As the frequencies get lower, lobing is less of an issue at small distances.



Multiple drivers can make things simpler or can make things very complex, i did mine the way i did to get as many frequencies point sourced... Which means now 300 hz -> 20khz is all point sourced as the midranges which are playing the exact same frequency at the same time will form a 'virtual' sound source in between the two drivers. If you look in between the two drivers you'll find the tweet. I offset this to avoid phase/node problems at the tweet/mid crossover point.

yeah, me too,

i cant hear anything at all when im driving, no subbass or midbass,

i could swear my stereo i on though...


i love how you dodge all the important rebuttlas ablomech with more maths and more useless facts about thickness of glass...





answer the question, why can i clearly hear my midbass at 100km in a rather noisy car???

i thought it was impossible, or are you just leaving out facts in order to stun us with more usless ones??







p.s, i think you are probly the most knowledgable person on this forum mate, and i do resect you greatly, its just the way you express yourself is so cloak and dagger, that i understand none of it,

put it in laymans terms for those of us that dont have degrees

What about a speakers attack and decay qualities when playing notes . I just learned those words too.........cors

I believe what he's getting at is this:

In a house the noise floor is low, maybe 45dB (completely made up, really not sure exactly) so when playing music with a dynamic range of say, 20dB, you need to be able to produce 65dB from your system. In a car with noise floor of 80dB, you then need 100dB produced for full dynamics. Which is what we as SQ lovers want right?

Since we love SQ so much we also want our speakers to be in their linear range, hence the cone area/xmax equation. Any more than linear xmax range and we're producing loads of distortion. Not SQ.


So in the car on the freeway with masses of road noise you can hear your midbass, sure. But do you hear the full dynamic range or just a bunch of distortion?

Hey guess what cors, these can be measured and shown in a graph too... It's called Impulse Response.

Thanks Gordo!



Pretty well summed it up.



On a sound car that has been “properly” sound deadened.

Blockers on the floor pan, quarter panels and roof.

Lowering resonance on the quarter panels and roof (sound decouplers)

Attention to internal panel resonance, and volume reduction.

Main vibration and noise decouplers replaced or in good condition (suspension bushes, engine mounts and exhaust supports)

Tires replaced with lower noise output.

Outer panel gaps and fitment checked, and aligned accordingly.

Windscreen wiper either factory fitted below hood line, or aftermarket windage reduction.

Side view mirrors main pivot gap (small) filled.

Even with this most cars exhibit a 50 to 250 frequency at 105 –120 dB external noise. (100 km per hour)

With 22 dB attenuation this equates to 83- 98 dB noise floor. If you replace the glass with double glassing, expect around 70 dB to 80 dB.

My point is the glass becomes the limiting factor, (You will of grasped this with various people “sharing” their music (?) at the traffic lights)

As previously reiterated this noise floor becomes part of your music, (Noise is simply a indiscernible message) perhaps an easy test is to play music at a suitable level parked, and then accelerate to 100 kph, you should notice a drop in dynamics of your music. (If the volume is not increased) Logically the quietist passage must be able to “overcome” the noise floor, this is suggested to be at least 10 dB by most acoustic recommendations. (See Crown etc)



This is why I have little time for car audio competitions as a useful gauge for my car. (I have no reason to knock them they are a great hobby) I contemplate minute advantage to listening to a car in a driveway, when I have an adequate listening source not 20 metres away. I would “fail” a single 6.5 driver as a mid bass for any car audio application: it cannot produce levels of sound pressure I desire in a moving vehicle.

fair enough,

you said you need to 100 db of midbass to hear my midbass at all...


you didnt say to hear it fully dynamically...

slightly over dramatised,

but ii get it now..

What good is an arguement without the use of hyperbole?



Nodes and anti nodes are best explained in practice.

our noisy Hilx utes are 78 to 80 dBA road/wind noise. In linear (non-weighted) terms, about 90dB. A late model Commodore is about 75dB unweighted.

just some observations to help....

this isnt the gra ph thread........cors

u should come to the comps just for the social aspect, more installmonkeys like u are well liked........cors

The efficiency of drivers are typically limited by how low you expect them to play and how large you are willing to make the enclosure. Regardless of the size/mass of the cone etc, this physical relationship holds.

Car speakers (with the exception of a significant number of subwoofers) can often be (reasonably) efficient. But it does not matter much as you can easily compensate and achieve sufficient (listenable) volume by simply using more power - the only downside is cost, but that is not a big deal these days.