posted
I built a 48db/oct 2 way crossover (only on the breadboard at the moment) what would be the ideal freq's.. ie do you want to cross the mid over pretty low (50-60hz) to try and get the best "upfront" bass? or ?? also do you want to cross the tweet over fairly low aswell? since there will be virtually no lower freq information getting through??
right now I chose 100hz (for simplicty of the calculations for the first try) and set it up on my test bench which consists of a Dex-P1 for the source, then the crossover, then a Pioneer Elite receiver providing power to my bookshelf speakers (8" + 1" soft dome) aswell as an ADS RS12.. the midbass impact is odd.. it hits VERY hard, and seems to come from upfront.. (I placed the sub behind me to simulate a car) this wasn't what I was expecting with a crossover freq which is fairly high. any insight or thoughts? thanks
-------------------- Beyond Audio Inhuman 12 (x2) -- US Amps 2000x -- Pioneer DEH-P9300 -- MB Quart components -- Orion xtr 500.4 -- RW Audio LD6.24MS"burp" -- 151.3 & climbing -- Member of Team Hertz Canada -- robin@rwaudio.com
Posts: 735 | From: Calgary AB | Registered: Oct 1999
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posted
A good bit of the crossover point has to do with how far away the woofers (midbass) are and how they are aimed, and the frequency played.
Because "bass up front" illusion comes from at least the upper harmonics of a note forming in at least some amount in front of you, your distance to your bookshelf speakers (which, when crossed over, probably have a decent amt of output in the 65-75hz region) and the output of your sub will form the substantial amount of the illusion- The 65-75hz portion of the sound is predominantly in front of you, and the other output (65-75hz from the SUB) is significantly lower than it would be in a car.
I would follow a simple rule of thumb- play the driver into its linear limit of xmax at 1/3 octave above the -3db point of the crossover. This will allow you to get roughly the best low frequency extension out of the midbass, while causing no real compromise in the sound quality of the driver. And, isn't the xmax of the midbass driver the real limiting factor? You want them to go as low as possible, for a real SQ oriented system.
ShadowStar
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Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
As for playing the tweeter as low as possible.. I might agree, to a point.. But, I find the power handling and dynamics of a system to generally improve as each speaker is played into a more specific range: Most midrange devices can handle well into the 2-4k range with decent ability, and while remaining roughly pistonic (for newer, stiffer drivers), whereas a tweeter played very low will inherently be less linear. Also, playing the tweeter very low will worsen your ability to manipulate the stage, as more information is present on the lesser directional driver (in the critical 1.5-4k region), however, playing a midrange to a higher frequency will allow you to manipulate the stage more, as more information will be present in the directional region of the driver response (1.5-5khz for 4,5,6 and 8" drivers generally.)
ShadowStar
ShadowStar
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Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
thanks for the insight shadowstar, but the odd thing is with this crossover there is next to no output in the freqency range your talking about from the bookshelf speakers (with a linkwitz riley crossover it is 6db down at the crossover freq of 100hz) so in theory it would be 54db down at 50hz and 102db down at 25hz and the highpass is 6db down at 100hz, 54db down at 200hz, 102db down at 400hz in comparison, to a 12db/oct butterworth @ 100hz, which is fairly common. it would be 3db down at 100hz, 15db down at 50hz, 27db down at 25hz, 39db @ 12.5hz, 51db @ 6.25hz so in comparison the butterworth has more "unwanted" output at 6hz, then mine will at 50hz... so I'm not sure if standard crossover points will perform the same, in theory you'd be able to cross the mid over far lower without exceding it's limits. as for the highpass.. 3db @ 100hz, 15db @ 200hz, 27db @ 400hz, 39db @ 800hz, 51db at 1600hz very different from the 48db/oct filter. so each driver in the system will be more confined to the freqency range you want it to reproduce.. but more care will have to be taken in matching the high/lowpass frequency's since there is so little overlap in comparison.
-------------------- Beyond Audio Inhuman 12 (x2) -- US Amps 2000x -- Pioneer DEH-P9300 -- MB Quart components -- Orion xtr 500.4 -- RW Audio LD6.24MS"burp" -- 151.3 & climbing -- Member of Team Hertz Canada -- robin@rwaudio.com Posts: 735 | From: Calgary AB | Registered: Oct 1999
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posted
RW, how'd that turn out on a scope and signal generator? I know when you do a what, four stage? Crossover like that, the Q's of the last stage get a little difficult to obtain. You must have used really good caps and resistors. I always used the Sallen-key circuit or the one version of them thats good for high Q's. I think it was called the Sallen-key? I dont know, I built probably a 48dB/oct crossover for a anti-aliasing filter for a dsp.If I remember right, the 48dB/oct is the best you can do with the available precision caps and resistors.. cool that you did though. Someday, Im gonna build a bass and treble control. I cant stand the way all the bass boosts are like these steep slopes or bumps around 100hz that make your bass all boomy. I want to turn up the bass not change the way it sounds.
Posts: 1259 | From: Fullerton. CA ,USA | Registered: Oct 1999
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posted
Is there a 4, 5 or 6" driver that really can't play up to 4K very comfortably? Just because the frequency goes up doesn't mean that the driver is incapable. Remember, an octave is only 8 piano keys.
As far as playing the tweeter down lower than 4k, why? Seemless midrange is most easily attained by using 1 speaker. Any midrange worth it's weight in paper should be able to play from about 100Hz to 4K. It might be better to split off the midrange driver at about 200-250Hz on the bottom end.
I'd keep my tweeter limited to higher frequencies like 4K & higher. That's what they do best.
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posted
I don't know how all tweeters behave, but personally I've had better experience with the tweeter crossed over lower.. I went from a stock quart crossover, to a reference 3 way (those plexi ones) and the tweet crossover was 1k lower, at first I was worried the tweeter wouldn't live, but it sounded alot better, maybe part of this was the better quality components in the crossover, I'm not sure.. maybe the direction the tweet was facing was better at that freq than the mid, I don't know. but it sounded better, imaging was a little better, but the stage was alot higher (well 6-8" as what it seemed) mid/tweet were in kicks.. this is just what I've found in the past, it may not be the same for all drivers, some mids are probably better then others as are some tweeters.. so some sets may sound better crossed over at 4k.. some at 2k or 1k, this crossover is just another tool, to help people make the most out of their system.. but it's all on how you use it and adapt it to your system.. not to follow a generic criteria that say's 2k is the best mid tweet crossover, and 65hz is the best mid woofer crossover, every car and every speaker is different.. and MrDank, I didn't use the sallen-key allignment, I just went on the basics, a linkwitz riley crossover alignment is simply two cascaded butterworth filters, so I just needed to design a 4th order butterworth, which is far simpler (simpler to get perfect anyways) I had a designed a sallen-key filter at first, only a 4th order and the hi/low pass filters never seemed to match properly, maybe it was component tolerances, I'm not sure.. so I started over, since I have alot more background in the theory of butterworth filters, and how to make them work.
-------------------- Beyond Audio Inhuman 12 (x2) -- US Amps 2000x -- Pioneer DEH-P9300 -- MB Quart components -- Orion xtr 500.4 -- RW Audio LD6.24MS"burp" -- 151.3 & climbing -- Member of Team Hertz Canada -- robin@rwaudio.com Posts: 735 | From: Calgary AB | Registered: Oct 1999
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