DiyMobileAudio.com Car Stereo Forum banner

1 - 5 of 5 Posts

·
Registered
2013 VW CC
Joined
·
111 Posts
Discussion Starter #1
I’m full of questions today. Reading many posts and I have read some say it’s ok to use asymmetrical electrical crossovers to reach the desired acoustical response...
Would this mean I could use 2900hz for left tweeter and 3200 for right to make them match when taking measurements? This could save some eq work.
I might have understood it wrong but I tried this and made the tweets match l. They were almost identical when measuring but when listening it was way off. I could definitely tell the left had the lower frequency setting. Even though REW measurements showed them to be exact.
My question is if they measured the same how could I hear it. I ended up going to 3000 on both. I was just hoping to save a few eq slots in case needed for when I figure out using 31 bands to tweak the center focus
 

·
Registered
Joined
·
491 Posts
I’m full of questions today. Reading many posts and I have read some say it’s ok to use asymmetrical electrical crossovers to reach the desired acoustical response...
Would this mean I could use 2900hz for left tweeter and 3200 for right to make them match when taking measurements? This could save some eq work.
I might have understood it wrong but I tried this and made the tweets match l. They were almost identical when measuring but when listening it was way off. I could definitely tell the left had the lower frequency setting. Even though REW measurements showed them to be exact.
My question is if they measured the same how could I hear it. I ended up going to 3000 on both. I was just hoping to save a few eq slots in case needed for when I figure out using 31 bands to tweak the center focus
Yes, you can yes different electrical frequencies, different slopes and even different "types" of crossovers for left/right crossovers. You want to use whatever you need to electrically in order to get the left and right match the best acoustically. All that matters is the end result - not how you got there. The closer they match before EQ, the better (as it requires less EQ).

Not sure how they could sound so different if the measurements match almost perfectly - that makes no sense. Something is wrong if that is the case.
 

·
Registered
Joined
·
3,444 Posts
Apologies in advance for the extremely long post. :p

Yes, it is perfectly resonable to implement asymmetrical crossovers to achieve the desired acoustical response. However, IME there are some caveats.

Before we begin, were your measurements done with a single fixed point microphone location, or multiple points with a spatial average (or similar moving microphone method)?

Also, I will assume that you have a 2-way front stage with tweeters up high and 6.5" midwoofers low and forward in the OEM door locations?

IME, using asymmetrical electrical crossovers to achieve a balanced acoustical response will result in a more coherent and balanced L/R sound moreso when using a 3-way front stage where the midrange and tweeters are close together with minimal ¢-to-¢ spacing and in a vertical orientation.

This results in the perception of hearing the majority of the important vocal range, or essentially ALL of the frequencies in the non-modal range, as a single point source. And limiting the negative effects of beaming are much easier for each of the drivers.

In all setups, but especially a typical 2-way front stage, you will have to pay more attention to the effects of beaming, and work harder to mitigate L/R side bias. It's just [email protected] difficult for just two, widely-separated drivers to produce the majority of the localizable frequency spectrum, coherently!

And crikey! Our auditory system is a complex mechanism. It has evolved over millennia predominantly in "wide open space" environments in order to localize sound sources for survival and identification.

In the natural world, if we do encounter reflections (mountains/canyons, etc.) the bulk of those reflections are most typically experienced with a much larger delta in time compared to the original source. This means that there are FAR fewer mid-to-high frequency comb filtering distortions and our ITD, IPD, and ILD mechanisms can work as intended.

Insert yourself into a tiny box with highly-reflective surfaces all around you, and, well, you are fuc'd! :p

Another potential issue that typical microphone measurements do not account for is our Head Shadowing effects, especially in the proximity of very close, reflective side surfaces from the near- and far-side window glass. A significant number of these side reflections will be at extreme azimuths to our ears in relation to the direct sound...or at least different enough to cause some additional comb filtering, confuse IPD, and affect coherency. Spatial averaging can account for most of this effect, but I'm not entirely convinced that it accurately replicates the Head Shadowing effects of when you are actually sitting in the listening environment.

Even with proper T/A, the delta in time of the combined REFLECTED sound between the L & R side speakers to our listening position is significant in relation to the direct sound. This makes it hard for the speakers in combination with the environment to provide a coherent soundstange in the first place. AND it makes it difficult for our auditory system to decipher or process the resulting localization cues.

How we localize sound sources is frequency-dependent. The Interaural Time Difference, Interaural Phase Difference, and Interaural Level Difference are the key determining factors. But the boundaries and limits of each of these are somewhat affected by the Azimuth of the direct sound source in relation to our ears, and is compounded by the azimuth of the Reflected sound.

In nature, most sounds we experience are limited in bandwidth. i.e. a bird and a goat will produce a distinct, separate range of limited-bandwidth frequencies. Same for running water in a stream or creek, unless when also near a large waterfall. And elephants can create an enormous range of high to low frequencies when trumpeting.

But for the most part, these limited-bandwidth natural sounds originate from a single point source, and also not from two separate L & R sources separated by some x distance.

However, most of these natural sources, especially those that create both high AND low frequencies at the same time, are all experienced at greater distances in which our ears/brain can process & distinguish them more accurately.

When you have two or more speakers that are separated by distance (i.e. not a point source), with each located in somewhat different reflective areas of the vehicle, and each are producing a distinct and separate range of the frequency spectrum within the reflective near-field environment of a vehicle cabin, our auditory system can more easily determine that there are multiple and completely separate sources.

Again, IME, using considerably different electronic XOs between L & R side speakers in a 2-way front stage can provide mixed results.

If you'd like to learn more about how complex our auditory system is in regards to localization of sound sources, here is just one good article. It also has reference links to MANY excellent studies on the subject which are IMO fascinating.

Anatomical Limits of ITD: An Ecological Perspective
 

·
Registered
Joined
·
491 Posts
Interesting info... I'm curious how all of that relates to my specific setup. Technically, I guess it's considered a 2-way setup, but in reality, it's really a 3-way setup. :)

I have 6x9 midbass speakers in the lower-front of the doors and 3.5" coaxial speakers in the dash. So my "up high" dash speakers produce everything from 400hz and up (acoustically and electrically - at least currently) via the 2-way 3.5" coaxial dash speakers. I do use different crossover frequencies for my midbass speakers though (helps work around a huge car-induced dip around the crossover area on both sides, but especially on the right side).

To me, having these 3.5" coaxial speakers in the dash really makes crossovers easy since the dash speakers can handle such a wide range of frequencies so well. Having just a small tweeter in the dash like most 2-ways seems like it would be a huge step backwards. I'm kind of surprised nobody makes "higher end" 3.5" coaxial speakers for this type of setup. I know that coaxials are kind of "frowned upon" in the high-end audio world, but it just seems like such a better solution that a traditional 2-way where you only have a small tweeter "up high"...
 

·
Registered
2013 VW CC
Joined
·
111 Posts
Discussion Starter #5
I have seas prestige in the sail panels,
Audison voce 3.0 in middle of door card angled upwards because that’s how the door is there. And audison 6.5” midbass. Doors are heavily treated with cld or whatever it’s called on the outer most skin of the door. Then 1” of Owens Corning in 1 mil plastic. More cld on inner door and the door is sealed. Layer of open cell foam between door and the door card. The door card is then heavily treated with foam, cld and spray foam in any crevices that could be filled. Lol. Kind of over did it probably.
Kenwood excelon reference 9905s with 2tb hard drive with HD videos and flac files. Helix dsp.3 to B2 audio 2500.1 and two B2 rage subs in ported box. B2 1200.6 for the door speakers.
Maybe I’ll try it again and see how it turns out.
 
1 - 5 of 5 Posts
Top