Why Processing is ESSENTIAL To Sound Quality

[TOOSTUBBORN2FAIL]

I didn't want to clutter any of the OEM+ threads, and this really deserves its own thread. I got permission to repost this.

This is what happens to a near perfect speaker, when it is placed in a car. This is why you can NEVER have true sound quality without a highly adjustable DSP to correct the signal for what the car is doing to the sound. AT LEAST time alignment, and 16 bands of eq per side, and that's the MINIMUM to start to approach good sound.

Originally Posted by Hanatsu

Still there is arguments floating around that EQ is not needed. That EQ should be used as little as possible etc.

Well, take a look at these measurements...



I measured a bookshelf speaker outside, 3m from ground and 10m from any other boundary. Mic position; 0,5m directly on-axis in front of speaker, 4V input@1kHz. Placed a graph offset of -6dB on this response to represent a 1m distance equivalent volume, this is "Raw Response" in graphs below.

I then placed the same speaker, with the same input volume in the car. Microphone location; 4 inch in front of headrest.


Driver Side FR:



Passenger Side FR:




This is the difference with a 0dB reference, this is the actual transfer function:

Kick-panel location:



Dash-height location:




Rear doors and Center






L/R Differences of Kick/Dash location









Conclusion:

The measured car response got response deviations of 40dB (!!) compared to the raw response. That's how the car's transfer function affect the response in this car. It's different for each car, depending on cabin size, speaker location and listening position. Some of the issues (nulls) can't be processed away. However, in order to attain proper tonal balance and staging in a car you absolutely need equalization. NOT "as little as possible", rather "adequate" amounts, to correct the deviations introduced.

[sly]

Generally speaking, you also need a variable Q equalizer. Not only is it important to have enough bands to shape the sound of the speakers in the car, you also need to be able to vary the bandwidth of those bands.


Use broad low Q settings to shape the highs while using somewhat narrower Q bands, as needed, for the mids to low mids. I cut the peaks in a response first. Then I run pink noise and monitor the response with a spectrum analyzer. I boost some of the low spots with wide EQ bands and monitor the analyzer. If a band doesn't respond to a boost in that area, I put the band back to where it was. This indicates that the drop in the band is caused by a cancellation and can't be corrected with EQ.


Time alignment is essential. Without it, your speakers will be out of phase and will cause frequency dropouts. No amount of EQ will fix an out of phase system.


Set your levels. Time align the speakers to the listening position. Take some measurements. Drop the peaks. Gently boost the low spots while monitoring in real time on an RTA. Be cautious about boosting low spots and back off on EQing those bands if the EQ settings are having no effect.


Cars have the second worst sound on Earth. Caves are the first. You can get by without an EQ in a home theater that has had proper acoustic treatments, speaker placement and bass traps. You will never have good sound in a car without an EQ and you will never get a good EQ without time aligning first. Speakers are never in the right location. Hard surfaces reflect everything. Road noise destroys your signal to noise ratio.

[PandaSPUR]

So what options do we 86 owners have other than the OEM+?

Until I can hear that system in person, I can't see myself spending 1k on it + losing trunk space.

[TOOSTUBBORN2FAIL]

Originally Posted by sly

Generally speaking, you also need a variable Q equalizer. Not only is it important to have enough bands to shape the sound of the speakers in the car, you also need to be able to vary the bandwidth of those bands.


Use broad low Q settings to shape the highs while using somewhat narrower Q bands, as needed, for the mids to low mids. I cut the peaks in a response first. Then I run pink noise and monitor the response with a spectrum analyzer. I boost some of the low spots with wide EQ bands and monitor the analyzer. If a band doesn't respond to a boost in that area, I put the band back to where it was. This indicates that the drop in the band is caused by a cancellation and can't be corrected with EQ.


Time alignment is essential. Without it, your speakers will be out of phase and will cause frequency dropouts. No amount of EQ will fix an out of phase system.


Set your levels. Time align the speakers to the listening position. Take some measurements. Drop the peaks. Gently boost the low spots while monitoring in real time on an RTA. Be cautious about boosting low spots and back off on EQing those bands if the EQ settings are having no effect.


Cars have the second worst sound on Earth. Caves are the first. You can get by without an EQ in a home theater that has had proper acoustic treatments, speaker placement and bass traps. You will never have good sound in a car without an EQ and you will never get a good EQ without time aligning first. Speakers are never in the right location. Hard surfaces reflect everything. Road noise destroys your signal to noise ratio.

Absolutely agreed on all the above. That's why I said dead minimum to approach good sound was 16 bands per side and time alignment. But yep, completely agreed.

[TOOSTUBBORN2FAIL]

Originally Posted by PandaSPUR

So what options do we 86 owners have other than the OEM+?

Until I can hear that system in person, I can't see myself spending 1k on it + losing trunk space.

Unfortunately there aren't really options below 1k, especially if you want a double din head unit. The mini-dsp C-DSP costs about $275. Add in a decent 5 channel amp, decent raw drivers, and wiring/deadening/install equipment and your over 1k. And you still have to learn to tune.

That said, 86 owners are rediculously lucky that OEM+ exists. No other brand of car has an option for a plug and play optimized system.

[sly]

Originally Posted by PandaSPUR

So what options do we 86 owners have other than the OEM+?

OEM is the only plug and play system I believe we have. But it's expensive and you're letting someone else tune your system. Maybe what they like is not what you'd like... I always recommend doing the install yourself.


I use miniDSP processors. Their car DSP: https://www.minidsp.com/products/min...-box/c-dsp-6x8 is $275. It can take the head unit's 2 speaker level outputs and convert them to 8 RCA outputs for connecting aftermarket amps. This could give you a stereo 4 way active crossover system. It features time alignment, compression, parametric EQ on the inputs and outputs and crossover function.


I would look for an aftermarket DSP whether it's from miniDSP or someone else. Then I would demo speakers in person. Go find the speakers you like at a stereo shop and listen to them before you buy. Look at Crutchfield for any adapter rings you may need or make your own out of PVC board from Lowe's and a jigsaw. Then buy some amps that are in the correct power range for the speakers you found. I'd recommend Class D amps because they are small, lightweight and generally cheaper.


Then take your door panels off and install the speakers yourself. Crutchfield and youtube have guides on how to do this. I personally like homebrewed audio. There's nothing more satisfying than installing something yourself. No one can do it better than you can because you can take the time to do it right. As for OEM, they are really the only plug and play system I know of. The only other option is to do it yourself. At least when you install it yourself, you know what you are buying and can tune it to your liking.

[sly]

Originally Posted by TOOSTUBBORN2FAIL

The mini-dsp C-DSP costs about $275.

Funny we recommended the same thing...

[TOOSTUBBORN2FAIL]

It really is the best option out there when your budget minded. There are better units, but nothing near that price, and there are several more expensive units that either haven't been proven reliable or just aren't any better than the c-dsp. I actually need to order one of their 2x4 modules to fix the subwoofer response in my house.

[PandaSPUR]

I'll probably just save up for the OEM+ system eventually, i feel like that'd be more rewarding and less headaches than trying to piece together my own system.

Low priority for now though. Gotta change my exhaust to something less droney, add some basic sound deadening/proofing, and upgrade my headunit to something with Android Auto (mmm).

[sly]

Originally Posted by PandaSPUR

...add some basic sound deadening/proofing, and upgrade my headunit to something with Android Auto (mmm).

You can't go wrong here. Adding sound deadening will make your current system sound better and when you eventually do upgrade, you'll already have that out of the way.

[Chimera]

I am interested in learning these things.
I have been toying around with the idea of picking up a minidsp.


I need a more educated mentor, I have been learning all this stuff on my own.
(goes to find I need an adult meme)


What's funny is I actually have an undergraduate electrical engineering degree but wasn't interested in speakers like at all until I had money to buy them. The ironies of life...


edit:
addon thought
I have easily spent well away and above what an OEM+ would have cost, and would gamble that the OEM+ sounds better than my current setup too.. but I have fun learning and trying things.. so there's value in that. That and my setup is all my own.

[Chimera]

Originally Posted by PandaSPUR

I'll probably just save up for the OEM+ system eventually, i feel like that'd be more rewarding and less headaches than trying to piece together my own system.

Low priority for now though. Gotta change my exhaust to something less droney, add some basic sound deadening/proofing, and upgrade my headunit to something with Android Auto (mmm).

Not derailing here, but android auto is awesome.
Now, if only poweramp worked with it.. someday hopefully.

[PandaSPUR]

Originally Posted by Chimera

Not derailing here, but android auto is awesome.
Now, if only poweramp worked with it.. someday hopefully.

Im waiting for the JBL Legend CP100 to come out. $400 with capacitive screen. Basic unit, no flashy bells and whistles.

I switched to Spotify Premium a while ago, so I should be good. Got tired of managing and syncing my own library across all devices.

[TOOSTUBBORN2FAIL]

Originally Posted by Chimera

I am interested in learning these things.
I have been toying around with the idea of picking up a minidsp.


I need a more educated mentor, I have been learning all this stuff on my own.
(goes to find I need an adult meme)


What's funny is I actually have an undergraduate electrical engineering degree but wasn't interested in speakers like at all until I had money to buy them. The ironies of life...


edit:
addon thought
I have easily spent well away and above what an OEM+ would have cost, and would gamble that the OEM+ sounds better than my current setup too.. but I have fun learning and trying things.. so there's value in that. That and my setup is all my own.

The way I learned was lurking on the car audio specific forums, specifically DIYMA, and going to sound quality competitions and gtgs. My first build I jumped into before I really should have, but I learned a lot from it. Had I known what I know now, the car would have been competitive at the national level. That said, between my first build, and my deadening testing, it seems I'll always be known as the deadening guy or the concrete guy (my kick panels were fabricated from fiberglass, concrete, and steel).

That said, anything you want help with, I'll do my best. A lot of people helped me out when I got into it, only fair that I help back.