91 replies to this topic

[br85]

It's been a while since we had a broad thread in the sound quality section, so I thought I might kick start a bit of discussion.

I think it's vital to determine one thing before we even begin. Is the system purely for competition purposes (maxing those score sheets) or impressing friends and people in a parking lot? Or is the system supposed to sound great while driving? They're not mutually exclusive, but on any sort of reasonable budget, you'd have to sacrifice one to get more of the other.

If driving SQ is what you're chasing first and foremost, your priorities change from the SQ judging sheet criteria toward more noise reduction and increased dynamics. There's a million and one threads on sound deadening and (more importantly) noise prevention so I'll try to steer away from this for now for brevity. Let's have a look at increased dynamics.

*First, download http://www.linkwitzl...om/spl_max1.xls

*Also, open up http://farm3.static...._6b43d7b91f.jpg as well.

To be continued...

Edited by br85, 30 November 2011 - 03:03 AM.

[268669♫]

Well dynamics is easy. Big woofers with big xmax with high sensitivity. Little wooders/tweeters horn loaded. Big power amplifiers. The problem is finding a car where you can fit all this and has good shape that can become part of the speakers, not just a place to put them.

Ant

[br85]

Exactly what I was eluding to insofar as making sound quality work in a moving vehicle, the first trouble we run into is (and this is where system design is CRITICAL) making sure we've got ample dynamics at every audible frequency. JBL's target response curve is a useful tool (mine looks a tiny bit different, but for design purposes regarding dynamics, it's great) to make sure we reach that goal. Why this is SO critical is because there's no point in building something to sound really accurate and with pinpoint imaging etc etc if it's riddled with clipping by the time road & engine noise ceases to be a problem.

It is in undergoing the process of trying to keep maximum spl at full linear excursion up to 20db higher than the roadnoise we experience (that's not a number I pullled out of the air, by the way) that we realise JUST how fultile our task is, and why noise control is SUCH an important factor in SQ, and (hopefully) why dynamat alone is never gonna cut it.

Edited by br85, 01 December 2011 - 12:03 AM.

[simplesq]

Geoff, I think the real question is: "Achieving Sound Quality, are we involved or committed"?

After sound deadening and building everything as solid as a rock, I do believe that more time should be spent on speaker placement, getting the fundamentals correct from the get go thus giving yourself the best possible foundation to work from. Aim to get that midrange as far away from you as possible, minimilise the PLD's between your tweeters and midranges. Build in real time while listening trying to get the big 5 locations correct without T/A or EQ and in doing this actually taking reflections into account. Regarding enclosures, just remember a speaker is only as good as the enclosure it's in. While tonality is a huge part of SQ, it don't mean a thing if it aint accompanied by good imaging. Aim to have enough head room, but above all keep it simple (use the minimal of gear).

In regards to choosing a car, after comprising a list of the cars you don't mind driving. Choose the one where the dash is as flat as possible. Ensure that it can accomodate big mid bass drivers (8-9 inch) either in the doors or kicks, but above all don't be afraid to hack it up.

[Big_Valven]

• Path Length Differences (PLDs)
  
• Reflections
  
• Cabin Gain
  
• Resonances in the listening environment (ie the structure of the car)
  
• Noise floor.

They'd be the fundamentals before we think about their effect or their extent, but yes the flow on challenges are dynamics, linearity, positioning, surface treatments etc...

I think it's fantastic that you've put a focus on the noise floor and dynamic headroom as I don't believe this is discussed often enough. The time I enjoy my "SQ" system most is when I'm on the highway on (another) 5 hour drive, with the volume wound around the end of the dial Designing a good daily SQ system in my opinion has to take real-world enjoyment into account and the noise floor whilst driving and resultant dynamic challenges are perhaps the biggest contenders in this approach.

[br85]

We're getting a bit ahead of ourselves here, but all of your points are valid.

Low noise floor is a topic all of its own so I'll leave it out of this one, let's assume we're working on a car that's already pretty silent. the next thing we need to worry about is speakers. Note: I say speakers beacuse we're NOT talking about just drivers right now. A speaker is a baffle (box), drivers, crossovers, the works.

Ignoring the top 2 and bottom 2 octaves for now (they're not that hard to get right), let's focus on the midrange (80-5000hz). Here's where 98% of the population who put expensive speakers (drivers) in their cars need to listen REEEEEEEEAL careful because I'm going to try and make it abundantly clear. You have 2 front doors in your car. Typical midrange locations in a driver side door are:

a) About 1 meter away from your head, about 55 degrees off axis, or (VE commodore for instance)
b) About 1.2 meters away from your head, about 60 degrees off axis (VR-VZ commodore, for instance)

Typical midrange drivers in a passenger side door are:

a) About 1.6 meters away from your head, about 15 degrees off axis
b) About 1.7 meters away from your head, about 20 degrees off axis

What conclusions can we draw from this? Because let's face it, this is a REAL mess.

[simplesq]

br85, on 30 November 2011 - 04:17 PM, said:

We're getting a bit ahead of ourselves here, but all of your points are valid.

Ignoring the top 2 and bottom 2 octaves for now (they're not that hard to get right), let's focus on the midrange (80-5000hz). Here's where 98% of the population who put expensive speakers (drivers) in their cars need to listen REEEEEEEEAL careful

What conclusions can we draw from this? Because let's face it, this is a REAL mess.

Ok, let's cut to the chase, getting one driver to cover 80-5000hz to a plomb. It's aint not going to happen, you going to need a much lower cross over point to get great midbass & it's going to have to be a big driver. In saying this there are 6.5inch midbass drivers that sound great but they going to get thrashed going up against a big midbass driver. A true midbass driver will be controlled, detailed, articulate, snappy, exibiting punch and have low frequency extension. Then you going to need a smaller midrange driver for those midrange frequencies. So you looking at 3-way bubber gentlemen, as one driver aint going to cut it. Finding one driver covering the aforementioned frequencies, though it may do them well will fall short and you can get your bottom dollar on that.

Edited by simplesq, 30 November 2011 - 05:35 PM.

[Frankston Car Audio]

simplesq, on 30 November 2011 - 04:40 PM, said:

So you looking at 3-way bubber, as one driver aint going to cut it.

bubber? aint? ... ffs Lyndon, you are on an Australian forum, not some "ratchetjaw hick town near Alabamie, US of A"! Speak English!

Sorry for the rant..

back on topic..
Mark

[simplesq]

Frankston Car Audio, on 30 November 2011 - 05:23 PM, said:

bubber? aint? ... ffs Lyndon, you are on an Australian forum, not some "ratchetjaw hick town near Alabamie, US of A"! Speak English!

Sorry for the rant..

back on topic..
Mark

My profuse apologies to all, I fixed it SQ Wizard. I get so excited when it comes to SQ

[br85]

simplesq, on 30 November 2011 - 04:40 PM, said:

*snip* this there are 6.5inch midbass drivers that sound great...

Maybe so, but almost always garbage while driving unless you listen to top 40's with no real dynamic range (4-10dB)

Let's take a look at a MASSIVE excursion 6.5" driver (a large cone area for a 6.5" is about 145cm^2 and 6mm one way is about as much as you'll get unless it's a sub)
Plugging the values in from the spreadsheet I linked earlier, we get a MAXIMUM of 95dB @ 71hz, which is pathetic. Why? Because in a VERY quiet car, you're up against no less than 70dB of road noise in this frequency range. An acceptable recording has at least 10dB of dynamic range, which means that quieter sections of some songs will be a MAXIMUM of 85dB. Why this is a problem is that means road noise is making up about 4% distortion in your midbass region, and it's REALLY NASTY distortion because it's not harmonic in any way, shape or form. MUCH larger amounts of harmonic distortion (especially low order stuff) is acceptable because it's literally "harmonious" to what you're listening to (remember this is ALL about music, people). I haven't taken into account cabin gain because I also haven't taken into account the fact that a car door is not a true monopole, ever. For all intents and purposes these 2 cancel each other out, for now.

Why does this ~4% distortion bother me SO MUCH? Because it goes largely ignored while some poor audiophile (victim of advertising) goes and buys a very expensive amp because it has less than 0.01% THD, and chances are, he's running a MUCH lower excursion 6.5" driver in his door (most "audiophile" 6.5 inch speakers are very low to make sure upper midrange sounds good... goodness knows why in a car but w/e) and he's dealing with well over 10% of TERRRIBLE road noise distortion battling his midbass drivers (this is with the volume knob turned up as high as it goes without damaging the drivers, too)

So, at this point, before we even speak about imaging, tonal accuracy, less-than-ideal speaker baffles, sufficient power or the harsh, reflective environment and transfer function of a car, a typical "audiophile" system (let's say a brax amplifier and some high end dynaudio components in the doors) costing around $8k or more actually sounds certifiably worse than someone who has put in 2 X cheap 6.5" per door running off a $350 bread and butter amp, at least in the midbass region, ON THE ROAD.

/rant.

[simplesq]

There will always be some degree of road noise, in a competition environment cars are not judged on the road or with the engine running. Chances are that most competitors will have 2 tunes: one for competition and another for everyday driving which would be heavier in the lower region to compensate for the road noise without killing their highs.

[Damo95]

simplesq, on 01 December 2011 - 06:50 AM, said:

There will always be some degree of road noise, in a competition environment cars are not judged on the road or with the engine running. Chances are that most competitors will have 2 tunes: one for competition and another for everyday driving which would be heavier in the lower region to compensate for the road noise without killing their highs.

I have 2 tunes, 1 for comp and 1 for me.. they sound totally different!!

[Winno]

So why do we have multiple tunes then?
Why one for 'competition' and then one non-driving we actually like the sound of?
(I can understand why we might have the bottom end boosted for when the car is being driven, resulting in a third tune set)

Edited by Winno, 01 December 2011 - 06:31 PM.

[icacha]

wouldnt people go through the same issues in car audio as they do in home audio, the environment they are listening to the music? there are many variables in both to overcome before you can sit down and say "now thats good sound".

[Damo95]

Winno, on 01 December 2011 - 06:29 PM, said:

So why do we have multiple tunes then?
Why one for 'competition' and then one non-driving we actually like the sound of?
(I can understand why we might have the bottom end boosted for when the car is being driven, resulting in a third tune set)

I have 2 tunes for 1 reason... i highly dislike the "competition" setting, because of my hearing disability and its set up for 1 seat judging..
I drive a lot with my wife in the passenger seat and it sounds like arse to her with the sq setting...

and further to that, i have minimal T/A (just enough to bring sub up front) and absolutely no EQ or Level adjustment (my comp setting has speaker levels lowered in my processor to get everything blending better) so its a lot more dynamic... And with the music i listen to, dynamic is good..


If it wasnt for the 3 way front stage I'm happy with, i'd be running horns without a doubt.. For me (and my hearing), horns are best.. My disability is in the upper frequencies so need some major dynamics up there.. having the midrange and tweeter up high help with this, as the upper frequencies are up higher... Now that i've got the height side of it taken care of (or the right height for me), i'll be focusing more on the angles of the components to get the best out of them..