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jaygeorge1979
11-10-2005, 08:40 PM
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?

PV Audio
11-10-2005, 08:45 PM
waterfall decay plot = ok

the other one? dunno

Moe Lester
11-10-2005, 08:45 PM
looks like impendence me.

PV Audio
11-10-2005, 08:47 PM
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
11-10-2005, 08:52 PM
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
11-10-2005, 11:50 PM
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
11-11-2005, 03:12 AM
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
11-11-2005, 08:18 AM
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
11-11-2005, 02:25 PM
i dont like your tone dave :)

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
11-11-2005, 02:50 PM
i dont like your tone dave :)

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
11-11-2005, 03:20 PM
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
11-11-2005, 04:48 PM
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 :)

jaygeorge1979
11-11-2005, 05:46 PM
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
11-11-2005, 05:59 PM
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
11-11-2005, 06:29 PM
even turds deserve a chance to shine...:-p

thylantyr
11-11-2005, 07:02 PM
Some loudspeaker designers are forced into that position when they work
for manufacturers. They want the cheapest drivers and they make you design
a crossover to make it sound acceptable. You are talking drivers that cost a few bucks
in some store bought product.

For DIY, there are folks who thrive on this. Lets get a cheap driver and try to make it
sound acceptable by making a clever crossover to fix issues.

For me, I just want to find a well designed driver that I'm able to plug into the amp
and have it sound good ''' as is "" without having to 'fix it' .. I pay more but the loudspeaker
is easy to work with and fine tune later.

For example, the 49 cent NSB. It need 6 cone treatments to fix gremlins. Also, a steep
slope helped alot to smooth out the sound. For full range duty, a phase plug mod helped
the top end. That is alot of work and modding for a 49 cent driver to make it very cool.
I even did coolant tests to boost power handling from 5 watts to 400 watts.
Plus, I had to sand the frames and paint it. Looking back, I'd rather tell the customer
to buy a $25 midrange because there is less labor to fix issues and you can focus more
on construction than driver mods.

jaygeorge1979
11-13-2005, 09:49 PM
i respect your opinion on that one, but at the same time i think its kinda kool that with a little elbow grease you can turn a 49 cent driver into something acceptable...so now i ask how do you do:

-cone treatments?
-a phase plug mod?
-coolant tests?

thylantyr
11-13-2005, 10:30 PM
i respect your opinion on that one, but at the same time i think its kinda kool that with a little elbow grease you can turn a 49 cent driver into something acceptable...so now i ask how do you do:

-cone treatments?
-a phase plug mod?
-coolant tests?

For NSB;

It's a paper cone so you can use chemicals to coat the paper. Some people use
certain diluted glue, some used polyurethance, I prefer spray can lacquer cause
it's thinned and lacquer layers meld with each other. I used a 1" paint brush to
paint the cone and dust cap, but not surround as it was rubber. Four - six coats
worked, let dry between coats. I did progressive coats and listened to the driver
and did blind testing to find the sweet spot on how many coats were needed.

Phase plug in this case was cutting out the dust cap and getting a $1.5 rocket
nose cone that fix inside, but it's hard to get a cone perfect so I got one with
a slightly larger diameter and used the drill to behave like a lathe, using sand
paper the diameter was taked down in thickness. Balsa wood is soft, each to
work with. It's too soft, touching the cone would cause a depression, so
I used minwax wood hardener and soaked the wood a few times. After it dries,
I cut the cone base to desired length. Paint it if you wish. To attach the phase
plug to the driver, you insert a flat head wood screw on the base, countersink.
The magnetism will hold the lightweight plug in place. Ideally, a phase plug would
be nicer if machined out of metal so it can act as a heatsink for the driver to
boost power handling a bit.

Coolant tests were ferrofluid injections. But the Ferrofluid I snagged was the
wrong kind for $30 a bottle. I needed the oil base, not water base fluid, but
that stuff cost $100. So, I added motor oil to the fluid. Power handling is
amazing with this stuff. Oddly enough, when 16 NSB's were used in the array,
driven by the 1200w, they handled the torture well and no coolant mod was
needed. I could add coolant if I wanted to make a line array for the sole purpose
of torture by allowing more SPL driven by a bigger amp. I was able to generate
insane midrange SPL with one driver with coolant, at 10 feet away one driver
would kill the normal person, imagine an array with coolant and more watts.

I don't think I would be doing cone treatments, phase plug mods and coolant
mods on $150 drivers.. /hehe

jaygeorge1979
11-13-2005, 11:26 PM
i think the only thing i would attempt would be cone treatments....seems cheap and easy enough, but how exactly does it affect the way the speaker produces sound?

PS i think i found my first project...my dad wants a line array...he likes stuff loud, SQ isnt TOO big of an issue, he just wants some new speakers for his big screen TV....it is gonna be run off of a mini system type thing, wattage unknown as of now...ill post up a new thread when i am sure i am gonna get it going...

thylantyr
11-14-2005, 03:13 AM
i think the only thing i would attempt would be cone treatments....seems cheap and easy enough, but how exactly does it affect the way the speaker produces sound?

Manufacturers spend alot of time making cone material and/or treatments, so
there is aot of testing done I would imagine. You do something, measure,
listen during driver development. But sometimes I wonder if manufacturers
really listen because the exotic cone materials the marketing people brag about
don't sound as good as they claim. My favorite sounding midranges are treated
paper, not those esoteric materials that create worse sound gremlins that you
have to fix electrically.

When you do your own mods you do controlled tests. Do a mod, listen. Compare
to an unmodded driver. Ideally, a switch to allow blind testing with a friend or two.

thylantyr
11-14-2005, 03:23 AM
PS i think i found my first project...my dad wants a line array...he likes stuff loud, SQ isnt TOO big of an issue

Assuming two channel tower;
Define a driver only budget and cabinet height....

jaygeorge1979
11-14-2005, 11:07 AM
for drivers i am really hoping that partsexpress.com gets some more NSBs or at least a similary cheap driver, cuz i have heard good thigns about those projects....it is a two channel stereo....cabinet hieght isnt too important, but the TV is a big screen that stands about 5 ft high...so i would like em kinda tall...