realistic t/s parameters please!

[prickears]

g'day guy's n girl's, excuse the nevousness in my typos (first time ya see!). Anyhoo been playin this game for a few years, but i'm just about 2 attack my first project in anger!!!! So armed with a couple of vifa p22wp-01s (remember those ones that were apparantly dragged kickin' n' screamin' out of mackie hr 824 monitors?!), a pair of vifa pl11mh-09-08 and a pair of seas 27tff, figure i might take a stroll out into the shed, spear 'em all into a pair of box's and break up any fights that may insue!......................... Actually the idea is, well, about that simple! But lets hold the bus here for just a tick. Does anyone out there have the 'REAL' t/s parameters on these drivers?
WINISD tells me that if i throw the p22's into a forth order band pass box and throw the lil pl11 into a vented box, I should get a response that is as flat as a s**t carters hat with almost no electronic crossover. However this is using 'claimed' t/s, and this about where me and faith in theory part company (remind me 2 get my own testing gear, oh please! lol) Any help is good help! cheers.

[tresch]

I can't quite tell what exactly you're referring to in your post, but if you're talking about how winISD is plotting the high frequency response of your driver as flat, that's because winISD is, essentially, a woofer enclosure design tool, and is only really aware of the theoretical low-end frequency response of a driver within an enclosure based on the driver's thiel/small parameters and the dimensions of the box.

Thiel/small paramaters are, for the most part, merely exist as a means for designing an enclosure for a speaker to shape its low-frequency response. Little useful data can be derived about a drivers actual frequency response by any means other than measurement with a microphone, unfortunately.

What winISD is plotting is a "Transfer Function," not "Frequency Response." It merely says "This box will cause the low-end response of the speaker to fall off kinda like this"

[PeteMcK]

Re:'remind me 2 get my own testing gear' - OK,
Download ARTA and stop guessing:

ARTA http://www.fesb.hr/~mateljan/arta/download.htm
ARTA Jig - http://zobsky.blogspot.com/2008/01/s...t-jig-for.html

[prickears]

thanx for your post guys. Ah sorry.tresch. If i plot p22wp-01 according to manufacturers claims as a forth order bandpass and pl11mh-09-08 as a ported box. Where p22s roll off ABOVE peak frequency matches pl11s ported roll off, (Q.7) is the only point on the plot i'm interested in here. This crossover point is around 130 hZ and 1 dB down, and flat either side. Looks good in cyberland but in reality i realise it wont be this good, due to winisd asuming a constant resistive load, and so forth.
However, a far bigger concern to me is that i have read that these manufacturers (t/s) claims can vary by 40 (and sometimes more) percent!
Even in cyberland (winisd) these differences are enough to throw a big cyber spanner in the works.
In our world, this difference is easily enough to be the difference between instant listening fatigue and a pair of speakers that 'dissapear'!
Guess i figured someone else out there may have had the same problem and perhaps independantly tested these drivers in more real world conditions.
thanx for the link PeteMcK, will check that out, cheers!

[Inductor]

Originally posted by prickears
g'day guy's n girl's, excuse the nevousness in my typos (first time ya see!). Anyhoo been playin this game for a few years, but i'm just about 2 attack my first project in anger!!!! So armed with a couple of vifa p22wp-01s (remember those ones that were apparantly dragged kickin' n' screamin' out of mackie hr 824 monitors?!), a pair of vifa pl11mh-09-08 and a pair of seas 27tff, figure i might take a stroll out into the shed, spear 'em all into a pair of box's and break up any fights that may insue!......................... Actually the idea is, well, about that simple! But lets hold the bus here for just a tick. Does anyone out there have the 'REAL' t/s parameters on these drivers?
WINISD tells me that if i throw the p22's into a forth order band pass box and throw the lil pl11 into a vented box, I should get a response that is as flat as a s**t carters hat with almost no electronic crossover. However this is using 'claimed' t/s, and this about where me and faith in theory part company (remind me 2 get my own testing gear, oh please! lol) Any help is good help! cheers.

Nice concept. (I have a) Similar idea with different drivers (probably good 4 another thread). Should -1- the forth order band pass need 1 or two speakers depending on speaker models (size/type/designs). The next thing is -2- should the MID be in a BR or closed box(?).

Also look at fig.9 of stereophile (for ideas)

Fig.9 KEF R107/2, individual anechoic responses of head unit and bass bin at 44". The latter is plotted in the near field below 160Hz, with KUBE controls centered (extended trace) and out of circuit (less-extended trace).

http://www.stereophile.com/floorloud...50/index9.html

[Inductor]

So as a concept (for a start) I would probably consider a BR box with some BSC depending on the slope response of the woofer. In the limit no BSC would be needed, not in this case. I would leave to you, for the project to mature.

[prickears]

thanx inductor,

I think for this particular project, and with this bass driver, 1 driver should do the trick nicely. The p22wp-01 has 90 dB sens and the pl11 has 87 dB ( here goes those manufacturers figures again!), that 3 dB should be swallowed up by the BP box quite nicely.

The plot does seem to look at its best with the pl11 in a BR box.

Not sure if there will be alot of phase issues to deal with, maybe someone can shed some light on this?

Post #6
So as a concept (for a start) I would probably consider a BR box with some BSC depending on the slope response of the woofer. In the limit no BSC would be needed, not in this case. I would leave to you, for the project to mature.

BSC=? sorry mate not following this post!

Would love to read more on your project, let me know how it goes!

[Moondog55]

BSC
=
Baffle Step Correction

the low frequencies wrap around the box so you lose SPL to the sides and rear ( Quick and very dirty explanation ) so the woofer NEEDS extra SPL compared to the midrange.

The PL11 will work in a small sealed box for mid-range duty
130Hz is a good XO point if you are doing this electronically but will be very expensive if done passively, which is why most of us cross a good octave higher around 240/300Hz

[Inductor]

Originally posted by Moondog55

The PL11 will work in a small sealed box for mid-range duty

Yes, I guess I did a typo before (never tested). Not that people do not take both in consideration.

[prickears]

thanx moondog55,

BSC = Baffle step correction! Why, yes of coarse! (having a bad head day! would you like a strong cup of coffee as well while i'm there?!)lol!

Actually, the whole idea in the first place was to use no electronic x/o at all for this bit! If for no other reason, than because my know it all p/c said i can! Y'see my ferret headed p/c reckons all this can be done useing nothing but boxes and air (except mid to tweet x/o, of coarse)! Can you believe this garbage?

Trouble is, Ive been around a fair bit longer than my ferret headed p/c, and i, (like you i'm guessing) beg to differ! So I figure seeing as my p/c hasn't even grown it's own arms yet, I'VE gotta build the damned boxes just to prove it wrong, just so i can say, 'Don't say us humans didn't try to tell you Ferret head!

When evolution verses computer, there can be only one winner!
I 'guess' then we will 'know' just how much is art and how much is science!

Then if it doesn't work i shall roll up the sleeves again and try a new and more conventional, (read boring), way and put the p22 in a br box and the pl11 in a closed box, crossed over higher with more complicated and problematic electronic x/o's, (something i'm trying hard to avoid).

Either way, there is no way this damned p/c will get the better of me, "I STILL OWN YOU, DAMN YOU!"

Now about that strong coffee..................javascript:smilie(' ')