i have drivers what can i do with them ?

lolojr1

Member
2004-10-03 5:20 am
i want to try to build some tqwtl or a horn of some sort i have been reading about them for a while and now that it is summer i would like to get out and build them .
i will list the t/s parameters i have from the woofertester2 and hopefully some one can come up with a good idea on what to do with these speakers

i have 2 radioshack 4" woffers drivers from the old linaeum speakers and 4 polk 4" drivers from the old ls/fx dipole bipole surround speakers with matching tweeters.

i have built sealed and ported boxes and have had good results so far but i think it is time to try something a little harder.

i am wonering if it is at all possible to use the 4 polk woffers and the tweeters that came along in those speakers to build the 4 main channels of my home theater, and possibly using the rat shack drivers as a center speaker just adding a tweeter

another question i have is instead of building 4 speakers can i build 2 with 2 woffers each because of the small size of the polk woofers like a sealed or ported box by adding more drivers you get more output ???

i am trying to build something that i can set on the floor and not use a stand and if that means adding extra height in the form of a empty sealed box of the same size to make them taller i will

here are the ts specs

polk

fs 63hz
revc 6.35ohm
zmax 26.34ohm
qes 1.1332
qms 3.5631
qts .8598
le .4512mh
vas .2076cuft
bl 3.8183tm
mms 6.5544g
cms 970.6567uM/N
kms 1030.2303 N/M
rms .7293 r mechanical
efficency .1256%
82.9913 db @1w/1m
83.9891 [email protected]/1m
the piston area from half of surround to half of surround is roughly 3.6"


and here are the rat shack

fs 54.14
qms 3.906
vas .365 cuft
cms 1.376 mm/n
mms 6.28g
rms .547 kg/s
qes .574
re 4.718 ohm
le .437 mh
zmax 6.558 ohm
bl 4.19 tm
qts .5
efficency 0276%
86.41 db1w/1m
88.7 2.83vrms/1m

size is 3.8" from surround to surround

any other details i forgot to add or things i have missed ?
 

lolojr1

Member
2004-10-03 5:20 am
i really want to build them im just not sure what design to go with .
i want to use the polk mids and tweeters as the 4 main channels of my home theatre and possibly use the rat shack mids with a nice tweeter from partsexpress for my center channel.

i just would like a nudge in the right direction .

so do i do a voight ? labaryinth? back loaded horn ? i just cant decide

i saw these today and i am intrested can anyone give me more details ?
http://www.pmillett.com/tqwp.htm

does adding a second driver change the desgn a lot? if so how do i account for it ?

i like the design and look of those are they a good choice for these drivers?

if all else fails i can just build a set of really nice computer speakers right ?
 
Originally posted by lolojr1
i really want to build them im just not sure what design to go with .


i just cant decide
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
not to decide, is to decide

~~~~~~~~~~~~~~~~~~~~~


if all else fails i can just build a set of really nice computer speakers right
````````````````````````````````````````````````````
heck yes -
better maybe to build somthin than nutn
 

lolojr1

Member
2004-10-03 5:20 am
not to decide is to decide .....

funny i do that alot

i dont want to just jump in head first and not know what i am getting in to

i like this idea
http://www.seas.no/thor.htm
and this idea
http://www.pmillett.com/tqwp.htm
but i dont know how to design a t line with 2 woofers?

do all the traditional rules still apply ?
doi just design it to act as if there was only 1 driver and just add a second

what about this
http://www.t-linespeakers.org/FALL/bipolar/index.html
the polk surround speakers i have are a dipole /bipole design with a switch that changes the di/bi setting and a crossover and tweeters all included

can anyone tell me if there is a different design to use 2 woofers or do i design it like a single woofer speaker ?

if so how much of a difference does the location of the woofers play a part in the sound that they produce?
 
Greets!

At a glance, the Polk drivers are best suited for either sealed, aperiodic, or TL while the RS drivers could also be used in a ML-TL or BLH.

BTW, for my records, which model drivers are these?

WRT to using all these in a HT app, the mains/CC should be the same and you can probably get away with mixing them in side, rear surround channels. Not being familiar with these drivers AFAIK, I don't know which have the best SQ overall, so that's a choice you'll have to make as you want the best ones for the mains/CC.

Since none of these will probably go very low at any decent SPL, I assume you'll have a sub for the LFE channel and set the mains/CC/surrounds to 'small'.

Adding a second driver increases the speaker's output 6 dB if wired in parallel and your amp can handle the lower impedance/provide the necessary current, which typical HT receivers can't do so figure 3-4 dB gain. Still, it's usually enough to compensate for baffle step loss, so IMO worth the effort/space with such low efficiency drivers. Unfortunately you don't have enough drivers to do HT with bipoles though. :(

WRT to designing for two drivers, just design for one, then double the Vb and add a second vent. Or if using a box program that allows multiple drivers, then design one big vent. If doing a pipe design, then only change the cross sectional area (CSA), leaving the height the same. The easiest way to figure the new size whether straight or tapered is to multiply the width and length dims by the SQRT(2), or ~1.4142 and round it off to the next higher fraction or whatever scale you use.

WRT dual driver placement, mounting them either as close as practical on the front or on the same plane in a front/rear layout is the norm, though if you know what you're doing you can use different locations to achieve various responses. In a pipe design you ideally want to suppress the 3rd harmonic, but this often places the driver too low, so either the pipe needs to be spaced up or make do with a non-optimum location. Since most designs posted don't have optimum driver placement and sound fine (I assume due primarily to the fact that damping required is done by ear), positioning it (them) where needed and try different vent locations to smooth it out as best you can before using any damping in the sim.

I haven't had time to 'run the numbers', so don't know how well suited your drivers are for the designs listed, but since you have measured specs why not do some designs of your own using MJK's worksheets?

GM
 

lolojr1

Member
2004-10-03 5:20 am
i would like to use the same speakers for center and main l and r
i dont really have the budget right now so i will probably stay with the one that i have althought i know it would be optimal

of course i have to use a sub what self respecting diyer hasent built a sub or two i have 2 in use now and i think i have a new angle on the 1/4 wave if you are intrested ill send you a few pics and how i did it i havent found anything like them out there

so if i do a tl keep the length the same and double the CSA?
is SQRT squareroot?

how do i supress the 3rd harmonic i havent heard of that and dont know what you are telling me to do can you lead me in the direction to do some reading about this


i just dl the mjk worksheets and havent really figured them out yet
any help would be greatly appericated

thanks a bunch
 
Greets!

>i would like to use the same speakers for center and main l and r
i dont really have the budget right now so i will probably stay with the one that i have althought i know it would be optimal
====
OK.
====
>of course i have to use a sub what self respecting diyer hasent built a sub or two i have 2 in use now and i think i have a new angle on the 1/4 wave if you are intrested ill send you a few pics and how i did it i havent found anything like them out there
====
A new 'angle', eh? Please do.
====
>so if i do a tl keep the length the same and double the CSA?
is SQRT squareroot?
====
Correct, right.
====
>how do i supress the 3rd harmonic i havent heard of that and dont know what you are telling me to do can you lead me in the direction to do some reading about this
====
Probably because it's apparently not considered a design consideration by anyone but me, and since I've never compared any of my designs with the more popular driver at top layout, it may only be in theory so just locate it either wherever you need it to be or what yields the flattest sim.
====
>i just dl the mjk worksheets and havent really figured them out yet
any help would be greatly appericated

thanks a bunch
====
You're welcome! Well, you haven't come back with any Qs, so I assume you've figured them out. ;)

GM
 

lolojr1

Member
2004-10-03 5:20 am
well lets see on the new angle on a t line ....
it might be but i will probably have someone tell me its more of a ported box

first what i did was found a 12" piece of pvc pipe about 10' so i could cut it to length and have a left over to build 2 stereo bass!!
then i got out my old cerwin vega 12" xl the ones with the red surround

i built a box that is about 40 " long by 12.5" square and slipped a pice of pipe 28" long inside it leaving one end closed and one open with a speaker mounted in the end of the pipe

so it gives me 4 small rounded triangle ports and a wavelength of the tuning frequency from the speaker to the end of the port

this gives me a verry nice sounding box tuned to arround 35-40
and if my calcs are right and 1/4 of that is the length of the box times two from the speaker to the back of the box and from the back of the box to the end of the port


well if its not right it could be that i havent really measured them in a few years and i was just starting to learn about transmission lines when i built them


i dont have a pic if you want ill take one and email it to you

and last but not least what file do i use to model a transmission line on mr kings spreadsheet ?
the mltqwtl? the closed end tl?......
im not really sure what style to go with ?
 
Greets!

Hmm, I can visualize this more than one way, so not sure what you did, but if you have a long line with a terminus whose cross sectional area (CSA) is <the pipe's, then you have a ML-TL, a cab style that I've used since the late '60s and which has gained popularity with the advent of MJK's work. I would like a sketch of the design if you don't mind so I'll know for sure what you built.

If you want to do a ML-TL (TL with vent), then use the ML-TQWT WS if bottom firing, otherwise use the PORTED WS for all other vented designs. For TL, I just use the 'offset driver in an open ended TL' WS. It doesn't calc the terminus's end correction, but the extra pipe length is inaudible and the 'SECTIONS' WS required to complete the calc is more trouble than it's worth unless you want to calc a multi-folded or flared/tapered design like he designed it for. He also has a WS for a true end loaded pipe, but few folks actually build them and anyway, his 'offset' WS creates the same plots if you input the driver's location at 0.001.

WRT what 'style' to go with, that's a personal choice based on your performance goals, the driver's specs, available space, etc..

GM
 

lolojr1

Member
2004-10-03 5:20 am
here are some pics
 

Attachments

  • test3.jpg
    test3.jpg
    95.1 KB · Views: 122
Greets!

OK, you have a pipe that has a bit more CSA than the driver 'dumping' into an acoustic 'chamber' which terminates into four long, smaller CSA vents. If we ignore the chamber, it's technically somewhere between a BR and ML-TL since its aspect ratio is too long to be a true BR, yet not long enough to have any TL properties in its tuning BW, but the chamber creates an acoustic low pass filter, so in audio parlance you built a bandpass box of 'x' BW tuned with multiple vents, AKA a muffler with multiple exhaust pipes.

For narrow BW apps such as a sub, a good performing, space efficient design actually, but then you already learned this by doing, rather than just theorizing. ;) Since BPs literally go back to the earliest days of sound reproduction and your basic layout has been used before, no new 'angle' unfortunately. As the designer/inventer Tom Danley has opined on several occasions, "the ancients keep stealing all my inventions."

GM