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#1 of 7 OFFLINE   Kyle H

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Posted September 19 2004 - 07:25 PM

hi...
Can someone explain to me what's cross over?
Speakers with cross over sound better?
Thanks alot...
*Southern California*

#2 of 7 OFFLINE   Cees Alons

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Posted September 19 2004 - 08:11 PM

Kyle,

The 'cross-over point' is the frequency where a channel will drop it's output ("drop" if you go along the line of the audible spectrum from one frequency, say a high one, to a low frequency). Another channel then will typically have a frequency curve where it 'drops' the output at the same frequency, but coming from the other side (e.g. a lower frequency to a higher). Thus the first channel (e.g. connected to a main speaker) will only output sounds with a frequency higher than the cross-over frequency, while another channel (e.g. connected to a bass or subwoofer) will only output the frequencies below that point.

Typically, that change from one channel to another (hence "cross-over") is not abrupt - if you would slide the tone along the spectrum - but half for each at the exact cross-over point.

Because most speakers aren't good over the whole audio spectrum (approx. 30Hz - 22,000 Hz), they do indeed sound better if the load is distributed.

Another form of "cross-over" is not in the amplifier, but inside the speaker box: two or more speakers (with different characteristics: bass, mid-range and tweeter) and cross-over filters to distribute the sounds to the proper speakers. There are so-called two-way speaker boxes (having two drivers: one low and one high) and three-way boxes (as explained in the previous sentence).
These type of boxes are the ones you're referring to.


Cees

#3 of 7 OFFLINE   Kyle H

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Posted September 20 2004 - 03:40 AM

wow... Thank you so much for the detail explaination. I noticed people like to have coaxial rear speakers... What does coaxial mean? Can I have all 4 coaxial speakers? 2 mb quart cross over front...and AUDIOBAHN AS65Q end?
Thanks alot... I want to have a nice sound...not to have it real loud...Thanks for any suggestion...

kyle
*Southern California*

#4 of 7 OFFLINE   KenWong

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Posted September 20 2004 - 05:06 AM

Coaxial means it's one speaker, not a seperate tweeter and woofer, and most coaxial don't use a crossover. People use coaxials for rears cuz most of the time, the car most likely doesn't have a place for woofers and tweeters (seperately) unless you do some custom work. Also, the rear sound stage isn't necessary important and a lot of times, it's referred to as "fill music." You can use coaxials for all four speakers if you want, but generally, components sound better. I'm not sure which line of mb quarts that is, but i believe the premiums, and qsd has a coaxial/components type of speaker that has a removable tweeter and uses crossovers.

Also, if your buying speakers for fronts and rears, make sure your sensitivity is very close to each other.


#5 of 7 OFFLINE   Kyle H

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Posted September 20 2004 - 06:06 AM

Because I recently got a new car. I want to upgrade the speakers because the stock speakers aren't good enough.
1 big question...
when it says sensitivity(db) what does that mean?
is it the same sound intensity in physic? the greater the intensity (db) the louder the sound?
MB Quart RKC-113 has 86 db intensity... is it a good idea to have for the front? (5.25" Coaxial With Seperate Crossover ) http://cgi.ebay.com/....e=STRK:MEWA:IT
and 94 db in the back?
*Southern California*

#6 of 7 OFFLINE   David.G

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Posted September 21 2004 - 04:37 AM

well crossovers are a necessity to good SQ but people who just dabble in it don't ever reap the benefits. Don't get coaxials for your fronts at all. Get components sets up front to do a couple things. One) having tweets that are seperate from the woofer allow the woofer to play better and also allow you to bring the stage higher by mounting the tweets out of the door panels and up on the dash. 2) components come with passive crossovers which will automatically seperate frequencies for you that suit the speakers best. Coaxials are ok for rear fill but for a good frontstage, components will do much better, handle more power, and have less distortion. Rear are really not that important unless you go for a 5.1 setup. I used to use rear fill until i added a few things up front and got a very full front stage. i will be adding a small rear fill by means of a 4in component setup thats run off the HU power. Obviously you can tell that rear fill to me is just filler. Unless you go 5.1, having rear fill can cause a problem if done wrong because it'll confuse the soundstages. never make one stage louder than the other, try to blend it so that is a seamless blend from front to rear.

If you want a set of good SQ components i can give you an email for a CDT Audio dealer. He gives good deals and CDT is on the same plane as Focal. Also if you get a component set, i would suggest an LP-1 tweet remote. This acts like a volume knob just for the tweets, capable of cutting it by -10db so you have the ability to change the level of the tweets to match your volume ensuring that your highs won't blast your eardrums to puddy.

As far as db you have the right idea. The higher db the more efficient the speakers will be with the power and the louder they can get.

As far as crossing over, you probably won't get too deep into it unless you get a nice HU like Eclipse or Alpine high end models but a crossover point allows the speakers to perform in the "sweet" spots. Like someone else mentioned speakers can't handle a full spectrum so you need to be able to seperate what goes where. For me i use the crossover on my Eclipse 8443 to seperate the frequencies. Since i cross it at the HU, my RCAs are set to high, mid and lows instead of front, rear and sub. On my crossover it has highs, high/mid, low/mid, and lows.

Crossover points will depend much on what type of speakers you have. For me i have been able to cross my highs(tweets) at 3.15khz on a 18db scale. My mid RCA is mid/high crossed at 2.5khz on 24db, and mid/low crossed at 160hz on 12db scale. The lows(subs) is set to 80hz, 12db scale. When i mention the db scale with the crossover point, this displays the cutoff slope. A crossover doesn't cut a frequency at the selected frequency it slowly cutoffs of that frequency. I can't remember the equation but basically what i'm saying is that 80hz with 12db slope is slowly after the 80hz frequency its slowly cutoff from the sound meaning say by 200hz, the 80hz frequency is non-audible. If the slope was on a sharper one say 18db that say at 160hz, the 80hz is not audible. On an even sharper 24db slope you can figure it out yourself.

Crossovers are something that depend on you and your speakers. They take a while to use properly because say you have a crossover feature and an EQ feature on the HU, any change on the EQ may effect the crossover and the sound and any change on the crossover may effect the sound of the EQ, so you'll be flipping between both of these to find the right sound.
David is the car audio guy, Jason is the home audio so if you see a post in car audio thats David, if in Home thats more than likely Jason. Confusing isn't it!!! Also i hope i am allowed to put my sounddomain down on my equipment page. Its car audio but you guys might enjoy it.

http://members.sou...

#7 of 7 OFFLINE   Kyle H

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Posted September 21 2004 - 04:52 AM

Thanks alot david.
*Southern California*