I hate you all

Quick question for ya Phil....

I agree with everything you said, I actually said it in the last thread, just not as extensively as you have. So if you state that a 60hz tone need X amount of room to reach its correct done, and 30hz tone need XX amount of room, based on that....isnt the cabin the WORST possible place to have a sub....

Its like having a tweeter as headphones, no note will be accurate.

I believe sound has to dissipate...hatchbacks may "hit harder" but I dont think they hit accurately to your ear. Keep this thread goin...

 

well -- given that you'll never be far enough to really 'hear' the accurate tone for bass with very low tones afterall 37' is pretty long for a car, and even 50 hz is 22.5 ft, the interior or trunk really doesn't matter since mostly it will be feel. but the more distance the better, and one reason hatchbacks can hit harder is b/c you can get reinforcing relections that allow the wave to fully form.

oh -- and correction above - 60 hz is not 2 feet, but is 18.9 feet, as i read the scientific notation wrong when i made the calc. (i rounded to 2) i'm going to correct it above too.

at the same time though, a hatchback can actually hit worse for some notes because the primary and reflection waves can actually cancel if their wavelengths work out right. but, that's true for any room, car, etc.

one very serious way to deal with the wavelength limitation is to use something like a folded horn design... which will also amplify the sound as well (due to the horn aspect). here's a interesting little writeup on folded horns (look for the Folded Horn Tech. section)

still - i'd rather choose an in cabin solution for bass over a trunk for one reason... the trunk is going to muffle the sound, and it requires the midbass to fill in the blanks for accuracy. an in cabin sub won't have that problem.

still - i would never put a sub in the cabin of my S. too much trouble and too little benefit.

 

[QUOTE=PJK3,Jan 3 2005, 04:02 PM]well -- given that you'll never be far enough to really 'hear' the accurate tone for bass with very low tones afterall 37' is pretty long for a car, and even 50 hz is 22.5 ft, the

 

umm... you know you could have saved a lot of time w/ the emote.



while i'm itching to address your challenges/questions, i really don't have the time to do it right at this moment. so, it will have to be done later.

quickly though,

there's a lot of layman's terms in my previous statements because i didn't think Dave wanted this turned into a classroom or technical briefing...

yes the amplitude will be reduced with distance, however without the full length of the wavelength between source and listener, you may not develop all the harmonics, which prevents the tone from sounding truly musical, and instead can make it sound mechanical or dull. especially when produced by a speaker versus an instrument. it also reduces the distance in which the wave can be affected by other notes/harmonics, and reduces the distance for reinforcing waves to build... all of these factors affect how the note sounds... and it makes the difference between a 'alive' or 'natural' sound, and sounding like a speaker reproducing the sound. that is roughly explanation of what i meant by 'fully propagate'.

i am very familiar w/ the concepts of time correction. and it has nothing to do w/ the distance i'm talking about. what i'm referring to is different and it is specific to reproducing the sound properly and not just the source alone. but since we were talking about subwoofers, i thought that point was understood.

the horn will do 2 things (which i mentioned above) -- it will improve efficiency massively by the design purpose of the horn, but will also increase transmission distance for the wave too. while their little writeup is marketing, i can assure you based upon my experience and the experience of others -- folded horn designs are jaw droppingly astounding both for volume and sound when you deal with well designed ones. of course, you can have enclosures the size of small vans when building, but...
in fact the loudest sub setup i've ever heard in my life was 2 12" subs in a large folded horn design. it was used by a guy i met once (but heard the subs all the time), and he moved them on the back of a full sized pickup truck as part of a setup to play dance music during Mardi Gras parades (for various marching/dance school/performing groups). the sub enclosure was so wide it hung off both sides of the truck by at least 6 feet, and was deep enough that it almost took up the entire length of the truck bed. but you heard him coming blocks and blocks away. he was only using about 100 Wrms / sub. but when you stood about 20 feet from it in the crowd, the bass made your chest hurt and would take your breath away. (humorously enough, he was very fond of "Your So Fine" and "Egypt Egypt" by Egyptian Lover and "Fantasy Girl" by Johnny O... i guess that dates this reference... )

correct -- you don't hear about it because generally it's useless to the average consumer since they don't have 40' or whatever for positioning room... so, it isn't really mentioned... 1-3 are critical for the average install. but for large stage type performances (where i mentioned i have used it), it can be critical component to good sound. i have 10+ years experience in large stage sound both professionally and on a volunteer basis.

my main point in mentioning it at all, is that the distance Dave is referring to is really irrelevant on the scale of a car. that was it...

*shrug*

 

so much for not having the time.... oh well, this is really only a partial of what i want to do, but my dinner is getting cold.

 

Please continue to elaborate. This is fascinating.

PKJ3:
So, does that mean that in a small room (or space in the case of a vehicle) it is not possible to generate an audible bass note whose wavelength is longer than the longest dimension or what? I am "pretty" sure I've heard bass notes in a vehicle with wavelengths longer than the vehicle interior length but then again, maybe not. Maybe it's just the doubled frequency which would take half the wavelength.

When a driver is moving at say, 30 Hz in a space where no dimension is as great as the 30 Hz wavelength, what happens? Does the wave "generate" but adds more nodes (nulls and peaks) than it would in a larger space? Do you only hear harmonics of the frequency but not the fundamental?

 

[QUOTE=SheDrivesIt,Jan 5 2005, 12:59 PM]Please continue to elaborate.

 

no... you'll hear the sound, and you'll hear it just fine -- because the air is still moving from the compression waves created by the speakers. and you can hear it adequately and with a reasonably accurate tone. it just might sound flat. the wavelength won't respond to the room's size though. it's a mindless creation of physics.

but what happens is that in the smaller volume (than the wavelength) reflections and standing waves, and other various accoustic effects will interfere with the primary wave. so the sound is changed tonally... it's not massive or dramatic, but it is definitely audible. and within close proximity to the speaker, somehow these affects are greater. but a doubled frequency would sound 2 times as high (which is actually 1 octave higher), so that isn't happening...

another way you can probably make an easy demonstration of this effect by getting a nice deep test tone, something in the 40 hz range
get it going on repeat, then w/ your ear pretty near the sub (couple inches - just don't hurt yourself or the sub), turn it up to a lowish moderate level (again, don't injure yourself -- just make sure it has some substance to the note). you will probably hear some mechanical sub noise and wind noise, but only some actual note. as you move away from the speaker, and you'll hear that noise take the form of a tone. this works much better if you're not in an enclosed area but are out in the open where you don't get reflection waves from a garage or such.
again, i'm pointing out that this is a subtle difference in the sound tonal quality, and i'm suggesting such a small range because it allows you to work w/ lower volumes (less ear damage) and less amplitude loss over distance.

in some ways it's a hard concept to for me to explain because while i've got a semi grasp of the mathematics involved, i have never researched it in depth and haven't done any personal calcs. but it was explained to me as a concept at a pro audio (soundman) seminar i attended 10 years ago (long time ago to remember lots of details), and it was also demonstrated in several ways at the same seminar.

i've also used the practice to solve many stage related problems. problems where a bassist was within 5 feet of his amp and was constantly turning it up to hear himself... at the same time though, he was washing out most of the stage so the various other performers couldn't hear themselves. the drummer even had trouble keeping a solid rhythm because the bass was so loud (he was on the far side of the stage from the bassist). and he was saturating the audience with bass, to where i couldn't get the house monitors loud enough to balance the sound, without resorting to bleeding ears. we'd tell him to turn it down, he'd turn it back up because he couldn't hear himself.
after battling this affect through rehearsals and some early performances, it suddenly hit me like a freight train and i remembered the course.
i got on the stage between sets, gave him a long guitar cable, and moved the bass amp to behind the drummer. suddenly, the drummer wasn't complaining anymore (he loved it, he never heard the bass and didn't get thrown off rhythm), the bassist dialed down amp and guitar, and suddenly, balancing the stage and room monitors was easy.
while i'm sure the room wasn't helping in this particular case -- the distance made a universe of difference.


so sure, someone may throw up the flag here, and may authentically shoot me down... i'm just working based upon a decade of personal experience and the concepts as i understand them and as i was taught them.

 

and so while i wrote, someone threw it up...

either or
i never said this anyway...

and sound waves travelling in a room from multiple sources (don't forget tweeters, midranges, midbass, and subs) are MULTIPLE sources, not the same. they do need distance in which to have harmonics become generated.

and a piano really is a terrible example... it generates so many various harmonics both by structure, design, sympathetic vibrations, and countless harmonics from the rest of the piano strings - you'll never get a pure 40hz tone out of it.

 

Just so you know, I am not doubting your personal experience. There are many, many factors that affect how sound, well, sounds. Especially reproduced sound. I would guess that the effects you were correcting had more to do with phase, cancellation, reflection, etc.

I'm just disputing that there is an inability to hear a note (or that the note sounds less good) at a distance less than its wavelength. I don't think there is anything in the world of physics to back that up.

I know from personal experience that (with my home theater sub in the corner) if I walk around the living room with my SPL meter, the needle floats all over the place. It is not related to distance, it is related to cancellations, additions and resonances.

Besides, I think the absolute lowest bass note is over 40 Hz. Isn't the bass typically played a little higher than the frequencies we are talking about?

I thought they were up around/above 66 hz, or so. I remember reading somewhere that chest thump resonance was somewhere around 80 Hz, and kick drums were 80-100 Hz.

30 Hz is pretty low...