bass blockers for my db570s?

nadams · December 2005

I'm wondering if I should get some bass blockers for my db570s... I've never heard them distort, but they are starting to buzz my door panels, and I thought maybe getting rid of some of the way low frequencies that they can't easily reproduce anyway might help? I know I should tackle the door buzzing issue separately, but right now I don't have the money for dynamat...

hellohello · December 2005

all you need is something soft to stop the panel itself from hitting the metal, a lil gasket tape or something of that nature could be a quick fix, as for bass blockers, they already have a cossover on them, so a bass blocker might make things messy

nadams · December 2005

Oh, they do already have a crossover? Go Polk!

I have some foam window sealer tape... I'll try some of that. One of the harder things is that on the passenger side, the spinny part of the window crank buzzes and rattles. I can actually see it spinning itself around from the vibrations. Need to figure out how to isolate that, or just get a new one that wouldn't do it. Driver's side doesn't have that problem...

hellohello · December 2005

theres most likely a loose bolt or screw on that one, probably needs a tightening

nadams · December 2005

Nope... the spinny part of the crank is just held on by some smooshed plastic on the back... no screw. The screw holding the entire crank to the metal bit inside the door is as tight as I can get it without binding. Right now, I have it taped so it won't rattle, but that makes it hard to roll the window up and down. Not that I'll need much of that this winter

hellohello · December 2005

oh, that thing... that doesnt really need to spin to get the window down... glue it tight so it doesnt move, then when you open the window, keep a loose grip on the knob, or better yet if the knob is smooth itll just slide on your hand... that sounds wrong, but whatever

PoweredByDodge · December 2005

i believe the 570's only have a high pass 6 db / octave cap on there for the tweeter and maybe a low pass 6 db cap for the woofer... i HIGHLY doubt / am 99.999% sure they are NOT high passed at all.

i have not seen a full range coaxial with a built in high pass for the woofer in my life.

go to **** shack (radio shack) and get two 400 uf (microfarad) electrolytic capacitors. it doesn't matter if they're axial or radial - doesn't even matter if they're polarized for the low power those speakers will be handling. make sure they caps are rated for 20 volts or better... (that'll give you a rating of 100w rms that the caps can handle) --- 25 V caps would give you a 150 watt rms rating.

if you get non-polarized caps then you can just hook them up in line with the positive lead of each speaker.. cut the + ... put one end of the cap toward the amp, the other end toward the speaker. if you get polarized caps then DO IT THE SAME WAY ON BOTH SIDES. one lead of a polarized cap is longer than the other... put both SHORT ends toward the amp, and both long toward the speakers.... or the other way around... doesn't matter as long as its the same for both sides.... if you don't do that, then you can end up with some "why doesnt the left sound exactly like the right" -- gets annoying real quick.

that'll cross you over at 100 hz with a 6 db slope - should kill most if not all of your rattle.

nadams · December 2005

From Crutchfield's description-

"Instead of the simple high-pass filter found in most car speakers, a built-in 2-way crossover network sends the appropriate frequencies to each driver for cleaner sound and better imaging."

So do I have a crossover or not?

PoweredByDodge · December 2005

2 way hoss -- the sends the stuff over 4k (or around there - the voice stuff) the the tweet -- and the stuff under that to the woofer.

that's 2 way -- one going the cut the lows out the tweet.... other cuts high out of woofer...

so no, you do not have a highpass crossover on the woofer / the unit as a whole.

nadams · December 2005

Okay... I'll look into doing my own bass blocker

Thanks

cam5860 · December 2005

I would not go to all that damn trouble when you could buy a decent cd player with built in high and low pass crossovers.

PoweredByDodge · December 2005

um -- all that trouble -- cam, he can get two capacitors for $3 ... a cd player would cost him 200 or more -- probably a lot more for a nice one.

My kenferd Excelon has built in crossovers... I don't use them. They suck. They're 6 db in the deck and the amplitude of the preout signal is affected. In general - they suck. I've never been one to like on deck crossovers... they always bothered me. Integrated chips drive me crazy.

IMHO VLSI should never have been invented.

neomagus00 · December 2005

vlsi?

PoweredByDodge · December 2005

VLSI: "Very large-scale integration, the process of placing thousands (or hundreds of thousands) of electronic components on a single chip. Nearly all modern chips employ VLSI architectures, or ULSI (ultra large scale integration). "

most of the **** now a days is integrated chips (multiple discrete components on a single chip).... which is all fine and well to a limited degree (totally opinion - almost no one agrees with me). **** like that new Triad "class T" (class D with a higher rate switching 'distributor' transistor) amplifier are built into these tiny postage stamp size chips that then get stuck in panasonic head units that boast (and rightfully so) 40 w rms output x 4 channels --- with an integrated crossover, bass shaper, and coffee maker.

neomagus00 · December 2005

why is smaller bad?

PoweredByDodge · December 2005

its not -- i just don't like it.

neomagus00 · December 2005

oh, okay then

why?

PoweredByDodge · December 2005

eh... i like things that are simple - not necessarily in their overall joined form, but when you break them down you get individual pieces. gives you a better ability to understand the circuit just by looking at the board and indiviual discrete pieces rather than having to analyze a damn data sheet that's usually poorly written and almost never syncs up to the actual layout -- often datasheets that are even "ok" written are done so in a manner thats from "start to finish" of the signal path rather than how it's actually laid out on the board.... if you're going to build one yourself, then sure that's great, but if you're trying to fix something, you really don't give a **** about signal path over the whole device, you'd rather jsut focus on the 1/5th of hte board you're working with... but that can often be scattered throughout a datasheet.

and lastly - in my opinion, discrete semiconductors are, in general, of higher build quality than some of these integrated chipsets that have come out lately. national semiconductor has made some dog **** cascaded D flip flops, whereas a similar DIP with just a bunch of Nor gates on it by the same company usually turns out to be a whole lot better... ya you have to wire it yourself on a board with your own jumpers where there's not a direct trace, but they tend to hold up better. i don't believe it's a matter of "what" they're doing but how they're doing it -- mfg's are putting 20 pounds of **** in a 5 pound bag and they're trying to do it really cheaply. that leads to errors and poor build quality --- international rectifier and fairchild do it cheap but not as cheap as nat semi -- they're about 20% more money - but that's not really bad when you consider that the **** actually works the way its supposed to. i had a bag of nat semi op amps (while they're not exactly 10 lbs of **** in a five pound bag, they were the micro size ones -- not normal dips but rather the tiny itty bitty **** size of stuff you'd see inside a blackberry) that i swear to god if 3 out of 5 of them outa the bag weren't bad i'd be a crossdressing hooker with a bad thyroid. and i'm supposed to trust companies like that to build VLSI / ULSI chipsets? they can't get ONE thing right inside a hunk of plastic, how are they supposed to get 100 or 1000 or more?

neomagus00 · December 2005

ah, point well-taken... so it's not the tech you distrust, it's the misuse of said tech... this i grasp...

PoweredByDodge · December 2005

on a side note - have any experience with TI stuff? it seems like their catalog has decreased the last year or two. they used to offer just about everything, and if you gut open a lotta older equipment, its chock fulla Texas Instruments stuff. now when I go to look up replacement parts I just get cross references to IR or NSC stuff. wacky.

hellohello · December 2005

I think i agree with ya, esp the 20 lbs of crap in a 5 pound bag comment, in my mind smaller things wont last as long, just because you cant fix them without a microscope. Now if youll excuse me, I have some point-to-point wiring to do...seriously

PoweredByDodge · December 2005

Ha Ha Ha Ha Ha !!!!!!!!!!

neomagus00 · December 2005

nah, i'm not too up on current electronics stuff, i'm just interested in the theory and application, not so much the actual doing it

cam5860 · December 2005

what cd player you talking about with 6db crossover slope in them must be the cheap models, cause the alpine's have 6,12,18 and 24 db slopes you select your own slope.

MacLeod · December 2005

Not necessarily. Most head units dont have crossovers at all!

cam5860 · December 2005

yeah true but you are starting to see a lot more middle end cd players with crossovers built in.

PoweredByDodge · December 2005

most built in crossovers in decks are 6 db / octave slopes --- all the kenwood excelons, 6 db/ octave. alpine the last time i knew (say 1 - 2 model years ago) was 6 db/octave.

350 to 650 dollar decks.

and even if they were higher order, they're inferior quality.

neomagus00 · December 2005

what's an inferior quality digital xover?

PoweredByDodge · December 2005

who said digital?

nadams · January 2006

PbD- When you say that using those caps will give me a 100hz cutoff w/ a 6db slope, what exactly does that tell me? Does the slope start at 100hz, or is it already done at 100hz? Just wondering what I should set the subs to at the upper level to make these meld together well. I want a good sounding system with no holes in the range. I'm probably going to buy the caps tomorrow, but I don't know when I'll be able to get them in with it being cold and rain/snowy.

BTW- I now have the db104's, but feel like they hit hard and strong sometimes, then suddenly dive out of thin air and I get next to nothing at certain frequencies. I don't have any ports (sealed 2 chamber box, don't know the internal size of each chamber), so the only thing I really have to tune is the crossover. I'm still going to give the 104's some time to break in a little more before I start worrying about why I'm not getting what I'm expecting out of them...

PoweredByDodge · January 2006

k... here's how it goes dude...

minus 3 db's is "half volume". (half power actually)

so minus 6 db's is "quarter volume". (quarter power).

that means that every octave behind 100 hz, you're dropping to 1/4 of the volume of what its at @ 100 hz... so 2 octaves down from 100, you've dropped to 0.25 * 0.25 = 0.0625 = 1/16th of the "volume" (power in watts) at 100 hz.

so lets say you're putting 50 watts into your speakers... then from 100 hz up to "infinity" (20k Hz or whatever the upper limit of your speakers is) you've got 50 watts... but at 1 octave below 100 Hz, they only get 1/4 of that... so 12.5 watts.

at another octave down (2 octaves below 100 hz) you've got a quarter of 12.5 ... so 3.1 watts. go another octave down (3rd octave below 100) and you've got about 0.75 watts... get the idea? that allows you to cut out the lower frequencies because while they're still being played, they're being played at only 0.75 watts or 3.1 watts or 12 watts... something very small compared to the 50 watts you're juicing through the rest of the speakers.

now --- where exactly does the true crossover point occur?

well... a 1st order xover (which a single cap in line with the speaker is) has an equation that gives you the -3db point.

so when you say "i want to cross it at 100 Hz, and use first order (just a cap in line)" - you're actually saying, "what cap value do i need to use so that at 100 Hz, i will have a minus 3db point ?"

so --- without talking in circles --- at 100 Hz, you're dropped 3 db's. after 100 Hz, the slope is not linear, it curves very quickly to full power (0 db's) ... before 100 Hz (below 100 Hz) you have a nice linear line (on a logarithmic scale) that has a slow of minus 6 db per octave, all the way down to zero Hz.

so how would you tune this?

Well... if your speakers are crossed at 100, then you cross your sub at 100 because the subwoofer crossover works the same way --- it'll be minus 3db at 100 Hz... with an 18 db / octave slope (most amplifiers have 18 db/ octave sub crossovers) above 100 hz.

so at 100 Hz you've got the subs at "half volume" (-3db) and the spekaers at half volume (-3db).

half plus half = 1 full unit... which means you'll have a perfectly flat frequency response... the subs will blend with the highs just right.

if you cross the subs at say 120... then you will have a 3 db BOOST in frequency response from 100 Hz to 120 Hz.

it's not a big deal - you play with it until you're happy - least that's my opinion for your setup... but the ideal starting point is 100 Hz... you may want to go a little lower or a little higher... it's your taste... I would probably put it at 100 to start, then try it at 80 or 85 -- and while trying that, set the bass control on the deck to center at 90 hertz or 100 hertz and give it a little boost. then recompare it with how it sounds at 100 hz and no boost.

now... phase may be an issue.

I did not know you were blending these with subs.

because the subs have an 18 db/octave crossover (most likely - find out what the slope is on your amp and let me know)... if they have 18... then they will be +270 degrees out of phase with the regular speakers. (or -90 degrees outs phase)

you're highs will be 90 degrees (or -90) out because they have a 6 db/ octave cap on them from the caps you're adding to cross at 100 Hz.

sooooo...

if the subs are +270 out... and the caps make the speakers -90 (=270)... then you're **** is perfectly in phase.

but... if you're subs are +270 out and the caps makes the highs +90 out... then you have a 180 degree out of phase condition... but thats ok... because 180 degrees out is "exact opposite" --- so all you'd have to do is swap the positive and negative speaker wires going to your subs and you'd be 100 percent perfectly in phase.

so now matter what happens, you're allright.

just keep in mind that if it doesn't sound like you think it should, that you should flip flop your speaker wires going to the subs and then listen to it again and see if it sounds right.

follow?

bass blockers for my db570s?

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