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I thikn its a very good idea to be promoting the fact the dynamat will probbaly not prevent rattles. But absorb vibrations? Im retty sure most of dynamat if not all is the type that merely raises panel resonance to prevent ULF (ultra low frequency) waves from causing resonance issues. regardless, a tip thread should be unimpeachable.

but lets not forget ALL the applications if we are going to say it cleans bass and makes bass louder! we use it to eliminate road noise, engine noise, raise bass efficiency, seal doors better than stock, etc, etc, etc! It might be better to leave the rest of the practical apps of dynamat entirely out of the tip thread, a tip thread is to give practical advice on how to act in a certain way as a reference.

thus "dynamat is not designed to prevent rattles" is probably a sufficient tip.

but heres the ultimate in offensive results of dynamat use. Ever install dynamat extreeme behind your door speakers? reflections off the aluminum plate often causes cone interferrence and make your sound FAR worse! But those who were willing to spend $40 or more on those small pieces of mat and then thought their performance increased would be offended if we insulted that use of money.

 
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I wish bass were omnidirectional, but its not. its a simple test though. put your HT subwoofer on the righ tside of your room. when something explodes on screen, does it explode on the screen, or does it explode off to the right?

same thing in the car. all my sub-bass comes from behind me. I wish bass were omni directional, I could put subwoofers in the trunk and they would sound like they are on my hood! But I have to live with bass coming from behind me.

some guys here have already addressed some issues of subwoofer box alignments and facings, but the original stement is still in there. its gotta go!

 
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well you sure are educated about car audio lol

 
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two bullets down: its just two ways to face a box. we can load the subwoofers off the rear deck, we can downfire, sidefire, put them into the cabin, even mold them into the dash! its redundant and unneccsary information to discuss rear and forward firing exclusively here, especially when its incomplete just discussing those two topics, much less including all others. eddie runner spent more time discussing box facings than I have in this thread all together. its a complex subject!

I would include it in the above bullet: diffferent subwoofers, boxes, and firing positions will provide different bass performance results. not better, not worse. different for different desired effects/applications.

 
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one thing I read once was "if you want bass to sound like it is coming from up front, put your subwoofers up front". just thought I woudl throw that in

 
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I can't wait till rabbit gets to capacitors... Course I posted a thread about it a couple of days ago located here: http://www.7thgencivic.com/forums/sh...d.php?t=208812 but it turned into bickering because no one could support their opinion with fact disputing the truths I posted.

BTW, where the hell has Ludlam been at? I'd have loved him to chime in as well, as I sometimes have trouble articulating ****.

 
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he hasnt been here for about a month

 
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Its not totaly accurate. If you corssover your subs around 50hz or less it gets pretty hard to tell they aren't up front. The lower you go the harder it is to locate them.

You will need some decent speakers to produce the midbass up front though.

 
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now im super unhappy you are in chicago rather than california. id love for you to sit in my car and experiment with me.

luds been super busy lately, between work and school and post whoring on eca (I dont think he even does that anymore) he hasnt had time to drop in here. I'm sure he will eventually, post a sentence or two in here.

 
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as a general rule best sq/spl mix is factory spec box? I wish I came up with this statement. A functional and useful tip for someone who is an audio beginner, or perhaps a honda enthusiast first and an audio enthusiast second. Its the perfect tip.

some of these tips have been 7th genners here on the war horse trying ot combat common myths about car stereo; some of these myths are even perpetrated by young enthusiasts on the audio boards! others are not myths but rather features that should not be used at all; I personally belive bass boost is one of them.

So I would reword the tip to say "bass boost should not be used at all, tune with the gain instead" or something of that nature.

also might be more politic to use less definitive terms when describing the effect clipping has on a stereo. its easy for a scrub to pick out the statement and say "but I heard that subwoofers in cars play like 10% distortion anyways, why shoudl I care baout bass boost?" so I might say something like "clipping may damage a speaker" rather than "clipping will kill a speaker", or of that nature. just using a terminology to help make the tips watertight...

this might be a good point in the tips to suggest that power doesnt blow speakers, people blow speakers.

If I were writing this tip line, I might combine the bullets in this general area into something like this:

there are 3 basic ways to kill a speaker: mechanical overload, thermal overload, thermal fatigue. power will not blow a speaker, whether too much or too little. you may feed a subwoofer any amount of power you wish. As a general rule, if you can't hear distortion, you will not blow the speaker.

unfortunately, even this is a misleading and fallacious statement. the bandpass box user will be delighted and crank the volume, hearing no distortion and thinking himself set. No relationship is made between the three methods of speaker destruction and power handling, such a discussion would most likely be too long and drawn out for a general bulleted tip list.

I dunno, I guess if I had to compress it down to a bullet, I would say something like: "power doesnt kill speakers, whether too much or too little. overuse of the gain know plus overuse of the volume **** kills speakers"

and again, its still not enough, it doesnt call for how much gain or volume! its a tricky one to bullet, I dont think I can come up with anything thatll be good.

 
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If thats sarcasm, i will fix the other stuff later but this statement got to me...keep in mind this is aimed at people who know little to nothing. so why have them out making custom boxes that will sound like crap when they can get a nice tuned rockford or JL box that will bring out the best in the sub?

 
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*make* a nice JL or rockford tuned box, not get . no sarcasm here, I think its the best tip on the list! I've been advocating using factory spec boxes for less motivated enthusiasts for years, and the way you wrote the tip was so clear, concise, and watertight. I hope people will read that and realize that factory spec is not the same as "pre-fab". That its a fantastic solution to a low motivation problem!

every tip list a 7th genner tries to fabricate should have this one included.

 
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batteries are to be vented due to acid contents, not gaseous emissions. to my knowledge, batteries only emit hydrogen. even if they did emit some toxic gas, I think the main advantage to sealed boxes are stability in the car rather than gas containment.

 
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Very informative post, good job

 
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actually they do release toxic gases, especially when being charged but they do it all the time also. they have to be vented in some way or bad things will emerge, plus the car will start to get a disgusting smell of battery rot its so gross . its better to vent than to contain the gases also.

 
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Rabbit, what is your opinion on the following quote regarding bass being omnidirectional? Just curious as this issue has come up in several discussions I've been in. This seems like a logical statement, but I'm still wavering on what research to believe on bass being omnidirectional. There are logical arguements on both sides.

[quote]"The way your brain figures direction and distance is through
Stereo. Both with your eyes, and ears. I'm sure you've heard
that someone who only has one eye, has no depth perception.

This is because your brain, being the amazing computer that it is computes the difference in the image one eye sees compared to the other and calculates depth.

Same thing with your ears.

If you close your eyes and someone to your right claps, the wave passes your right ear first, then your left ear. Your brain calculates the time it takes to pass and says "hey, that's to the right and a little bit forward". Makes sense right?

Well here is were true Sub-woofer comes in. The distance between the ears
on a typical human head is about 6.5" (funny how 6.5" drivers are said to produce the most natural reproduction, huh?). Now as the frequency of the sound, whatever it is, gets lower, the vibrations get WIDER. If you were to see a high pitched squeal on a scope, it would be a really tight wiggle of a wave. As you go lower, those waves get larger and larger. Once those waves get larger then the 6.5" (average) distance between your ears, your brain can no longer sense which side of your head the wave originated from because the wave is now bigger then your head!!

This wave that gets bigger then your head is right around 80Hz. Right about where our subs should start working and our mid drivers should be rolling off.

EVERYTHING below 80Hz is BELOW the range that our ears can sense direction. As you get closer to 20Hz "limit" of the typical human ear, the waves are 40 feet long!! So unless your head is 40 feet wide, your brain CAN NOT hear the direction of BASS at those SUB frequencies!

If you can point out where the sub is in any setup, it's because of audio cues or higher frequency (harmonics) of the note resonating from things around the sub, the wooshing of air through a port, or even resonation of the sub-box itself if it's not built very well (long unbraced panels)...or a bad (high) crossover point. If your subs are extending over 80Hz then yeah, you'll hear where they are. "

[/quote}

 
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diskreet:

I put some objection here if you can read, and let other people to read it.

1. Human ear limits to 20Hz-20kHz. True, but the real problem is that you not only feel bass below 20Hz, you also feel a presense of space by having frequency playing beyond 20kHz, up to an infinite point (can you remember those days that are pretty normal and nothing weired around, but you "feel" something's there that makes your head very uncomfortable? Those are the high SPL ultra-high frequencies that gets into your ear.). All amps that says have a freq response of 20-20k doesn't mean the reproduction stops at 20kHz. Good designed amps are capable to amplify indefinite frequency range, which, in nature is the second and third order harmonics that you will hear (ie. playing 1kHz wave will also produce 2k, 4k, 8k, 16k, 32k, and so on, in a lower sound pressure). If a speaker can't produce anything beyond 16kHz (a lot of cheap speakers cannot), you don't feel the presense of space. That's why some speakers have freq response up to 35kHz, without a huge drop in dB.

2. Bass is omni-directional. True, but in a car, facing the subwoofer to the rear very close to the trunk lid will produce much better bass response, especially if you have a separate trunk space (sedan/coupe). It was done by experiment by a lot of people, so I am not going through the result in here. Basically it has to do with wave length and amplitude, and the reflection creates a sum in amplitude (because of very long wavelength, they just add up). Very interesting thing is, in home audio, a lot of speaker manufacturers recommmend to put the sub at the corners of the wall.

 
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One more thing to mention about. It's about phase alignment and frequency distribution of speakers.

WhiteRabbit, have you set up your sound stage yet? Did you X your midbass/sub below 80Hz? The following is for you, just my experimental results you may NOT or will NEVER agree on.

Here are some sub problems:

-If sub is playing higher than 125Hz, it will always be noticible (unless midbass and sub are in correct relative phase and absolutely time aligned) no matter what the roll-off rate(xo slope) is.

-If you hear sub hitting on one side but not another, the side you can't hear is out-of-phase. ie. you hear sub playing on driver's side but not the passenger side, then the passenger side is out of phase. To correct it, either rewire the passenger side speaker (phase alignment) or use time correction (time alignment). Sometimes you will have to use both to get the sub playing in the middle.

-If you hear some bass up front in the center, and some bass in the rear, it is caused by the resonance of trunk lid or rear deck. Turn all your speakers off, and hear how much rattle it is in the rear.

-If the bass QUALITY (not level) is better in one side than the other, it is caused by a boost somewhere. Lower your sub crossover point. I will say there's a boost below 80Hz in our Civic, and is more noticible in the driver's side. I use Dyns which "naturally" rolls off starting at 100 (-3dB at 80Hz, so is -6dB/oct roll off naturally) and X both the midbass and sub at 56Hz@24dB/oct, I don't have this problem. Look at your speaker's freq response curve to figure out.

-If the sub has weak output, reverse sub polarity.

Here are some speaker set problems:

-If one set of speaker is louder than the other, use balance.

-If female higher "AHH" sound gets pull all the way to one side, reverse both midrange polarity and delay the midrange that the "AHH" doesn't pull into. ie. the AHH pulls all the way to the passenger side, then reverse both midrange polarity and delay the driver's side, for approximately 0.3ms. *works on 3-way set only.

-If you hear lower "HUM"s on one set of speaker, lower the level at 250Hz, Q=0.5.

-If you hear tweeter emitting from both sides, ie. "s" sound emitting from both tweeter while the vocalist is in the absolute center, reverse one tweeter's polarity. If the tweeter becomes inconsistent with the midrage, reverse the tweeter into opposite configuration.

-If your human voice is separated into two side, ie. you hear some human vocal in the left but some in the right, use time alignment if you like, or do phase alignment on the woofer. It works extremely well in 3-way set, especially 3-way active setup with individual time alignment and gain adjustment (I use PXA-H701 with digital input from head unit, for a total of 6 independent channels for my speakers). Remember to lower the output level of the WOOFER that seems louder after adjustment.

Because of all these adjustments, I prefer a 3-way rather than 2-way setup. Because at some point in a 2-way setup, the wavelength will essentually become out of phase (1/2 the wavelength of some lower notes) which will cause problem in cars.

 
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pop, my opinion is that bass IS directional. the quote is well written, but noone in this forum has to take anything I or that person said at face value. simply grab 20 feet of speaker wire and head out to your home theater subwoofer and start playing around! The results will speak for themselves, one way or the other

 
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m.....I would say bass is NOT directional. The only thing is if it is in phase with which speaker. If the sub is out of phase will all speaker, of courses it will sound coming from somewhere because the continuous freq fuction has broken. It will cause the cancellation for the out of phase part and the in phase part will play WITH both speaker, while anything in between will be somewhere. What are your high pass and low pass settings?

 
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between 40 and 60 Hz for the midbass drivers in kicks, and 20-25 Hz for the subwoofer. depends on the day of the week, really.....

interesting idea about the potential phase issues. Its certainly got a following, members who say through TA a subwoofer can match back up to the stage.

but youll find just as many people who prefer the "bass up front" theory, and strive to get the lowest FR possible up front, hate putting subwoofers behind the listening position if they can help it.

But I dont think there is anythign I can say against the idea that the subwoofer is locatable simply due to phase or pathlength differences. Its probably true.

 
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bass may be directional, but in a perfect room you shouldnt be able to tell.
in a car or a room that isnt perfectly set up and balanced then the little reflections of waves and distortions and such will give you an idea where its coming from.

 
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What? between 40 and 60 for midbass? I am thinking how big your kick sealed enclosure is and what driver you are using.....BTW, why you HP the sub?

 
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in a perfect froom, the subwoofer is between the towers in front of you

 
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WhiteRabbit, I have ALL bass up front ONLY when I do several types of tuning to make me fall into certain requirement.....

 
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thats 20-25 low passed, and I dont like sealed kickpanels. Ive always gotten better results with AP or vented kicks.

 
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so ur saying i should mount a sub on my dash? ALL OVER IT, i need duct tape, popsickle stick and fiberglass

 
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20-25LP? on what? Please let me know your xo settings more specific, thanks

 
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Sub on dash won't work, even if you can install it.

 
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I gravitate between 40-60 Hz highpass either third or fouth order filters for the midbass drivers, and between 350-500 Hz lowpass third order to transition to the highs.

the subwoofer has only a lowpass filter with a cutoff of 20-25 Hz either third or fourth order (whatever its set to for the midbasses) with 20 Hz boosted six to ten dB with a very very narrow passband (almost a notch filter).

my highs are around 400-600 Hz highpassed with a 3rd order filter.