Speaker FAQ

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Not bad, overall.

Just curious... What about equal wavelengths? IB vs Sealed vs Ported? Beaming? etc....

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crossover points, crossover slopes, tweeter attenuation, tweeter protection, impedence compensation [zobel network]

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Im sure there are a lot of people who dont know what some of those mean. including myself.

what would also help is how an active setup works

There are speakers that play full range quite well, maybe you can't fit a set of Weems or Voight pipes in a vehicle, but they do exist and are in common usage //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Thanx for the Info Squek You rock man...

crossover points, crossover slopes, tweeter attenuation, tweeter protection, impedence compensation [zobel network]

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Im sure there are a lot of people who dont know what some of those mean. including myself.

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I have lurked here for a while. I figure the least I can do is toss out some info. Most of this is pretty basic, but for the sake of completeness I will try and provide some info about each of those terms.

Crossover Points I am sure you have heard the term 20 to 20 in refering to audio. Sound is just pulses of air pressure our ears can pick up. Frequencies are measured in cycles per second (Hz) which is just the number of pulses which happen each second. If your speaker moves back and forth 80 times in a second it is playing an 80Hz tone. It is generally acepted that the range of human hearing is 20Hz to 20KHz. KHZ is KiloHertz or 1000Hz. If you know piano, the fundamental tone for middle C on a Piano is about 263 Hz. You will not find any speaker anywhere which can produce 20Hz all the way up to 20KHz (that will fit in your car or that you can afford). That is why you use some combination of tweeters and woofers to reproduce sound. A typical 2 way component set will have the tweets covering notes from 3KHz-20KHz and the midbass covering from 80Hz-3KHz. The sub covers 20Hz-80Hz. In the system I just described the crossover points would be 80Hz (where the sub gives way to the midbass) and 3KHz ( where the midbass gives way to the tweeters)

Crossover Slopes In the above example I listed a midbass/tweeter crossover point of 3KHz. If I were to unplug my midbass speaker and play a 1.5 KHz tone I should not hear anything, right? Wrong. The hand off between two speakers is very gradual. If you take two speakers playing the exact same note at the exact same db, the result would be 3db higher than one speaker. Since the falloff of a speaker is gradual, the crossover point is the tone where both speakers are down 3db. There are a few common crossover slopes: 6db, 12db, 18db and 24db. These are know respectively as 1st order, 2nd order, 3rd order and 4th order. What does this mean? In my example from above, if the crossover slope was 3rd order (18db) it means that for every octave below the crossover frequency the sound fades off at 18db. So if we were to unplug our midbass and play a 1500Hz tone (one octave below 3KHz) it would be 18db below a 3KHz tone played into the tweeter.

tweeter attenuation In most car audio environments the tweeters end up very close to your ears while the mids end up further away. Since the tweeters and mids are playing at the same level it would make the tweeters sound louder than the mids since they are closer. This is why many crossovers will have tweeter connections for 0db, -3db, -6db etc... This allows you to lower the power to your tweets so you can match them to the volume of your mids. This is known as tweeter attenuation. FYI since every 3db drop is half power if you have your tweets set to -6db and running off a 100watt RMS amplifier you are actually only sending 25watts to your tweeters.

tweeter protection Like any speaker, if you stress them too much they will break. Some crossovers will have fuses installed between your amp and tweeters that will blow at a predetermined wattage to prevent you from blowing a tweeter.

impedence compensation [zobel network] This one is a bit harder to explain without getting into crossover design theory. Basically in order to design a crossover you need to know what the impedance of the speaker is. The components for a 3Khz, 6db slope crossover are totally different if you are using a 4ohm speaker rather than an 8ohm speaker. The problem comes into play near the resonant frequency of the speaker. As a speaker aproaches it's resonant frequency it tend to resist electricity more. For example, in a common 6ohm tweeter with a resonant frequency of 1Khz, the amplifier may see a 12 ohm load at 1Khz rather than a 6ohm load. This REALLY messes with crossovers because they suddenly see a 12ohm load and their crossoover point changes for that moment!!! A zobel network is normally used when you are driving tweeters down to a point near their resonant frequency. It is a set of components which divert power through a resistor near a particualr frequency (normally tuned to the resonant frequency of the tweeter) so as to show the crossover and amplifier a more consistant resistance.

good stuff as always squeak. and thank you mr bill, that all seems on the mark.

but people (even myself sometimes //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif ) wont understand what a 'crossover slope' is, unless they SEE a graph of both points, with the rolloffs. this is how they will understand, so this is my contribution.

Crossover Points Cont'd - now you all know that a crossover point is meant to limit each speakers 'bandwidth' so that each speaker can only play that certain range of frequencies, and retain a higher volume and better clarity. this is the reason we use components with passive corssovers, or an active crossover that we can select the exact points.

you should also understand that a crossover WILL NOT act as a 'brick wall' and stop the speaker from playing that frequency. a crossover is meant to limit the extenstion of the speaker so that it will not play frequencies it was not designed to play at loud volumes. this means that there will be an 'overlap' of frequencies.

for example (and this is ONLY for example, i highly doubt you will see this kind of crossover and respose curves... ever) this is a subwoofer (a GREAT subwoofer mind you //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif ) and a midbass speaker, lets say an 8" speaker.



as you can see, the point where they 'dip' together is the crossover point (please correct me if im wrong). this point (by looking at the graph) is 80hz. this is normally where people set thier subwoofers and midrange - its practically a 'rule of thumb' to try about 80hz on your frist try, and go up or down from there depending on if YOU LIKE IT OR NOT. because noone can tell you what you like and what you dont like. this is 100% subjective.

now, as the speakers 'roll off', or start to play the frequencies below\above their crossover points, that frequency will get lower. here is the tricky part. since the other speaker is picking up that frequency as its companion drops it, the music wont sound like there is a giant hole (or it shouldnt if the points are set well).

Refrence Level - this is somthing that people usually dont comprehend eaither. a 'refrence level' stereo system- is a system that can FULLY REPRODUCE, at any volume level that it is capable of, 20hz->20khz with no distortion. now, it may sound easy by reading all this stuff we are teaching you, but its not qute that simple. the '0db' setting most of you see on your home theatre recievers, or stereos, refers to the *CURRENT* volume, or the standard volume, or whatever volume it will produce with how many watts the amplifiers are producing, if you turn the knob down from 0db, you will be ATTENUATING the signal through the amplifier - and thus, your system will more than not, be below 0db. for example, we have a single 10" speaker playing a 50hz tone (in and out 50 times per second), about the middle of the 'sub bass' frequencies. we are feeding it 500 watts of power in whatever box, and whatever car. when we put a microphone in the car, the car reads 100db. that is the pressure level of the air as the speaker moves in and out, its a way to measure volume (as most of you SHOULD know). now, REFRENCE LEVEL, means that EVERY FREQUENCY (or **** near it) should be able to play 100db. so our tweeters playing a tone of 5631.245hz should be able to play 100db, and likewise, the midrange should be able to play 235.654hz at 100db. this is the '0db' mark. say the system is at a volume of 20, and its hitting 96db, ALL FREQUENCIES should be able to play a 96db note. this is refrence level - all your frequencies have a 'FLAT' response curve. and this is what that looks like;

flat response (good)



versus a peaky and valley response curve (not good)



now, some people LIKE peaks and valleys in certain spots. this is fine. this is why stereos are subjective. some people cant hear distortion (sure //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif ) - and thats fine too. but 0db means at whatever volume that knob is at, an entire 20hz-20khz sweep should mic evenly. it wont be exact. but you get the point.

please feel free to add anything that i might have missed. hope it helps.

Round Speakers VS Oval Speakers

The subject goes as follows: A 5.25" speaker can fit in a stock 5x7" location, and a 6"-6.5" speaker can fit in a stock 6x9" location. So which should you use? It's quite simple. A round speaker is more likely to have weight evenly distributed against the Voice Coil and VC Former. This means that you can achieve clearer sound with a round speaker that with an oval speaker. On the flipside, an oval speaker will obviously have more cone area. With the same excursion as the round speaker, the larger oval cone produces more sound. An oval speaker is capable of getting louder and usually producing more mibbass than a round speaker.

There are a great many exceptions, more and more as the quality of your speakers goes up, but this is the general overview.

ok, so let me see if i understand this

i have my subwoofer set up at 75hz at a 12db slope, that means, that it plays a 75hz note loud, and anything deviating from that will get progressively quieter?? so if i want to here a broader range from my subwoofer, i will turn the slope down, and possible to 0db??

so if i have it set at 0db, then the point that i choose for the crossover wont matter?? or will it just cut off frequencies higher than 75hz??

thx for answering a noobs quesions

Patrick

ok, so let me see if i understand this
i have my subwoofer set up at 75hz at a 12db slope, that means, that it plays a 75hz note loud, and anything deviating from that will get progressively quieter??

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if this is a LOW PASS FILER (filters out EVERYTHING but the LOW frequencies), it will cut off everything ABOVE 75hz. and at that point, the volume of everything above that point will decline and 12db PER octave (octave = 1\2 lower, or 2x higher)

[see the black graph above, and look at the white line. this is a subwoofer with an 80hz low pass filter]

so if i want to here a broader range from my subwoofer, i will turn the slope down, and possible to 0db??

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as its a LOW PASS FILTER, and it will filter everything ABOVE that point out of the speaker. so in order to hear MORE and play HIGHER frequencies, you will need to turn it UP say to 80hz, or 85hz - not down.

but as said, it wont completly cut off at 75 or 80hz, it will decrease in volume after that at the rate of (as you said) 12db per octave. in this case, at 150~160hz, it will be 12 decibles lower - so you will still be able to hear it. this is how music 'blends' together via different speakers.

so if i have it set at 0db, then the point that i choose for the crossover wont matter?? or will it just cut off frequencies higher than 75hz??

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as stated above, it would filter out EVERYTHING above 0decibles - if its a LOW PASS FILTER.

thx for answering a noobs quesionsPatrick

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no problem patrick. hopefully your questions will help many more to come.

furthermore i feel that some people might take my whole article about refrence levels a little askew - there are two kinds of 'decibles' that we look at. we look at spectrum response and speaker frequecny response. both are listed as the same graph. HZ on one side, and DB on the other (as seen in the above graphs). spectrum response however, is meant to tell us how loud the entire spectrum of sound is in our current setup. this is done by an insturment called a RTA, or Real Time Anaylazer. it analyzes EACH frequecny, and it will show a graph (seen in the white graphs above, peaky vs flat) the loudness of each frequecny. this is useful so we know if our high frequencies are overpowering our low frequencies, or vice versa. most people will never use an RTA, but that is beside the point. our second kind of reading is speaker frequecny response. frequency response is the physical response a speaker can produce at whatever loudness (db). the speaker company will send the speaker 1 watt, and put a microphone 1 meter away from the speaker, and play a sweep of the entire frequency band. it will record how loud each individual note is, and we will see a graph like this;



this is an adire koda 8" midbass speaker, recorded as i described above. notice how it can ONLY PLAY 22-2300hz down to about 50hz - this is the PHYSICAL LIMIT of the speaker... and this is why our stereo's need multiple speakers to play every note. BUT - each speaker CAN NOT play EVERY note in theie PHYSICAL SPECTRUM at the same volume. this is why there are peaks and valleys. this graph is a real-world application. it is the actual measurements of that actual speaker. and to be honest, it is quite a flat response between 1000hz, even though 1000hz is -7db from 100hz.

i cant really think of anything else to put in here. so please post any and all questions for us to awnser. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

excellent information

//content.invisioncic.com/y282845/emoticons/wowflash.gif.89a61f4caede63a11dac36e97d61323e.gif thanks guys i never understood crossovers but now i get the jist of it. great read. leanred a **** load keep it comin guys!