hanging by a thread

[ArjenShenzhen]

Dear DIY'ers,

Since i have now made a nice Granite speaker that does not sound nice :-((( i would like to ask some one, who ever has the time, interest and experiance, to help me out.

i have a basic design, made with the help of an online Java applet to calculate the TML length, but i am using 2 woofers.

I did ofcource calculate using the conus surface of those 2 woofers added together.

These are made by T&T in shanghai, and have a recommended crossover of 3,5 Khz. i also found tweeters from T&T and i want to combine 2 woofers, 6.5" and one tweeter in one housing.

since this costs quite some space, about 45 CM on the front side, there is no longer just one point of beginning in the TML line.
Does this cause trouble for the function of the TML, as the length of the duct is effectivly not the same for the 2 drivers.

who could help me and do the math with MLK's mathcad sheets? im a disaster with mathematics, and can't get the hang of it.

the one willing to help me will ofcource be rewarded and with what we will have to discuss... a TA2022 amp for instance....

Thanks for your time.

Arjen Helder

[ArjenShenzhen]

The small one sounds great, probably due to the fact that it uses only one driver. but it could still be better, its response could be more flat.

The Big one kinda went wrong, speakers do not sound so nice, driver quality is not good enough and i made a mistake with the crossover... this one is glued shut.. noting i can do about it now

[Colin]

Given the wok involved in the cabinets, it might be better to go with an established design derived from the MathCad worksheets, one tested by members of the forum.

[ArjenShenzhen]

Hi Colin, this would be relativly safe, but the problem is that i want to use cheaper drivers.

ive heard these drivers play and love there sound and at about 250 RMB per one, there a real bargain. i want to use 2X 6.5" because then the cabinet is nice and slender, it looks Very sexy in that black granite !

i know calculating it is allot of work, but its the only way to do this right, and i dont wanna mess it up... Again.




Greetings,

Arjen

[GM]

Originally posted by ArjenShenzhen

since this costs quite some space, about 45 CM on the front side, there is no longer just one point of beginning in the TML line.
Does this cause trouble for the function of the TML, as the length of the duct is effectivly not the same for the 2 drivers.

The TL only 'feel's pressure change, so it 'feels' the two drivers as one oblong one, ergo the midpoint between the two is its acoustic center, i.e. its mean pressure point and the distance from the top you would input the driver's location in a simming program.

GM

[ArjenShenzhen]

Thanks for that advice,

how do you think about those online Java based calculators, what is the reliability with those programs?
Any personal expariances out here?


Thanks in advance

[GM]

You're welcome!

They're useless IMO. Better to extrapolate from a reflex box designer's calcs for a given Fb (Fp) IMO. Set tuning to the desired TL Fp and find the cab Vb that yields a ~3 dB peak at Fp and divide the line length into it find its cross sectional area (CSA) or you can try the old DOS program on this site which is much better than the JAVA scripts I've tried: http://www.hal-pc.org/~bwhitejr/

If more than one driver is used, then double CSA for two, triple for three, etc..

GM

[rjbond3rd]

Hi GM, pardon the dumb question here, but are you saying that a TL is basically just a ordinary bass reflex box, simply stretched in one dimension until it meets the required line length? (I'd love to think I could grasp this...)

[Bluto]

Arjen -

I experiment alot with unknowns/maybe's and therefore use OSB as it's cheap .

Real shame here .... beautiful cabs.

Perhaps you could find a proven design quite close to box size and use a supra baffle ?

Bluto

[ArjenShenzhen]

Hi There Pluto,

Yeah i am actually using Glass quite often and have made good results using it, but i want to step up my accuracy, fins some better tools for designing. it will alwais be trial and error, even when all the math is done, but still, per one granite housing i need about 400 USD so yeah....... too bad.

Also getting reliable data on speakers, especially on the made in China ones is hard sometimes getting any data at all is hard already.

Today i was on the phone to get some info... if i could not speak Chinese, no way i can get what i need, now im waiting for a mail from there engineers just for some standard data as Xmax and VAS and so on.

Whell see where this go's, good drivers, especially imported ones are cheaper in the states, there are good sounding made in China drivers, but it just needs some more tinkering, as they do not supply those nice housing drawings as Fostex does.

Anyway, thanks for your input, prehaps there is some around with some more math advice!

Greetings from sticky sweaty hot Shenzhen ;-)