reading frequency response graphs

[jaygeorge1979 10+ year member]

http://www.partsexpress.com/pdf/296-165.pdf

i was checking out some different drivers and i was looking at the two dimensional graph and noticed that there are two plots on there....one of em ascends slowly and stays straight for awhile then gets messy where it cant handle the high frequencies...i understand that one, but the other one, what does that represent?

Click to read more...

 

[PV Audio 5,000+ posts]

waterfall decay plot = ok

the other one? dunno

 

[Moe Lester 10+ year member]

looks like impendence me.

 

[PV Audio 5,000+ posts]

looks like impendence me.

indeed, but the y axis is not in ohms, it's in decibels. and if indeed it is, he's ****ed from the start lol, unless i am missing something.

 

[PV Audio 5,000+ posts]

let's just assume it isn't labeled correctly and it indeed is impedance. it is very similar as it starts flat, peaks, flattens then rises sharply. however, the graph does not line up with znom at all....

 

[jaygeorge1979 10+ year member]

ok now i have another problem...i am finding multiple drivers that do not even offer these frequency response graphs...

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=297-076

all i could find is "Frequency: 20-5000 Hz"....is my only option here to play with my DCX and figure out where to cross it over? or would i be safe doing like an 8th order L-R bandpass from 20-5000?

 

[thylantyr 10+ year member]

ok now i have another problem...i am finding multiple drivers that do not even offer these frequency response graphs...

My favorite sounding midranges had no published response graphs, yet

I was able to determine that they sounded better than other high end drivers

by doing in depth auditions. Later, I found some graphs on some of them

and they aren't pretty - but they are top notch in SQ.

all i could find is "Frequency: 20-5000 Hz"

Doesn't tell you much. Doesn't tell you it's SQ.

...is my only option here to play with my DCX and figure out where to cross it over?

Run the driver full range to hear what it does 'naturally' out of the box.

Compare it to other drivers playing full range, you will figure out what it's

able to do.

or would i be safe doing like an 8th order L-R bandpass from 20-5000?

Don't use that method.

One step at a time.

 

[PV Audio 5,000+ posts]

ok now i have another problem...i am finding multiple drivers that do not even offer these frequency response graphs...
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=297-076

all i could find is "Frequency: 20-5000 Hz"....is my only option here to play with my DCX and figure out where to cross it over? or would i be safe doing like an 8th order L-R bandpass from 20-5000?

who in the mother of god told you that was a good idea?

 

[jaygeorge1979 10+ year member]

i dont like your tone dave //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

well, i ASSUMED that since i cant see the graph, that something really REALLY ugly could be happening outside of that frequency range...my solution? have a slope so steep that virtually all frequencies outside of its recommended range wouldnt see the light of day...maybe i am wrong in my logic? please tell me

 

[thylantyr 10+ year member]

i dont like your tone dave //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
well, i ASSUMED that since i cant see the graph, that something really REALLY ugly could be happening outside of that frequency range...my solution? have a slope so steep that virtually all frequencies outside of its recommended range wouldnt see the light of day...maybe i am wrong in my logic? please tell me

When you see a tweeter spec, not chart, that says 2000hz - 20khz frequency

range, that really doesn't tell you much. You don't know how it behaves betweeen 2000hz and 20,000 Hz. What if it has a steep roll off at 12khz? You'd

never know by that spec. You can look at the 2000Hz number and say "hmmm, perhaps it might work that low ? let me try it".

If you need a tweeter that plays low, down to 2000Hz and you find one

that says "5Khz - 20Khz", then it might be safe to say it won't do it well.

Same applies to midranges.

For woofers it's crazier. A subwoofer may have a 20hz - 1000Hz spec, but it

most likely will only perform well from 80Hz on down. Above that it probably

sounds like azz for many reasons.

 

[jaygeorge1979 10+ year member]

you make good points...i am confused tho...what do you mean be steep rolloff at 12khz? how would you go about fixing a problem right in the middle of the drivers intended freq?

 

[PV Audio 5,000+ posts]

you make good points...i am confused tho...what do you mean be steep rolloff at 12khz? how would you go about fixing a problem right in the middle of the drivers intended freq?

rolloff = drop in response //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[jaygeorge1979 10+ year member]

ahh...good call...but what do you do about it? is there some way to filter out a very narrow band of frequencies, say: 12k-13k Hz?

 

[thylantyr 10+ year member]

ahh...good call...but what do you do about it?

What I do is not use that driver and pick a better designed one. Makes life easier

even if I have to pay more for quality drivers. Why try to fix a turd ?

 

[jaygeorge1979 10+ year member]

even turds deserve a chance to shine...