for selection of drivers , important criterias that should be adressed

[hunter audio]

from a transducer design engineer (in india)

a driver cannot be defined by ,

to consider its t/s parameters , never actually suggests how it will play

or the materials it may be constructed with , ofcourse if it was to be used by the police force - kevlar is very important

but when it is to ultimately convert source to analougus sound , what are on line is its realism , accuracy , depth , tone / timbre , nature etc in hi fi

in pro audio - directivity , effective spl , accuracy , decay etc

it cannot be defined by a mechanical formula

what has all this got to do with diy ?

when one has to choose a drive unit or units for ones amp / speaker enclosure in mind etc

what are the factors worth considering ?

any qs in this subject will be answeared by me - a diy audio electronics audio enthusiast constructed upto 1000 w rms at 8 ohms amp

and a transducer design engineer in india

[Timn8ter]

Using T/S parameters and creating models are the best tools we have available to get us on the path to our goal. The actual result will vary from the model and it's only through experience that we discover tonality and how to fine tune the system to our liking. That's why this forum exists. We share our experience and results of building different systems using different materials with the hope of reducing the guesswork. Every so often someone will do something that shouldn't work but does. We just don't know how to explain it. Ultimately, our ears decide if we were successful or not.

[sreten]

So the important criteria is your opinion ?

sreten.

[Timn8ter]

I'm thinking that if the ultimate goal was based on measurements all speakers systems would sound the same. Measurements are a means to an end but not an end in itself, or at least, shouldn't be. And yes, the most important criteria is the opinion of the listener. If you're a manufacturer, the most important criteria is the opinion of the masses. Hmmmm...that must be why I got into this.

[sreten]

sorry Mr. T,

my post was aimed at the original post, not yours.

sreten.

[Timn8ter]

Originally posted by sreten
sorry Mr. T,

my post was aimed at the original post, not yours.

sreten.

That's ok, it gave me an excuse to spout off a little more.

[VEC7OR]

I personally think that T/S parameters can quickly and accurately specify what driver we are speaking of(and how we can use it), but actually sound of 2 drivers with same paramters will differ a bit here or there. T/S parameters dont describe the sound itself.

[hunter audio]

I am replying with the previous post in mind ,

considering a purchase of a loudspeaker unit

ts parameters defines this unit mechanically , through these mechanical parameters one can proceed to use / utilise the unit to its best , including efficiency , and is of utmost importance to its enclosure design enclosure

but one has also paid for the materials used in the construction of the drive unit ,

this will decide its longetivity , compression at peak power , overall accuracy - not to mention the tonal quality or the nature of sound produced

where am i heading , - the internal volume of a cone may be same as that made of ordinary hard pressed paper or for eg a kevlar woofer

1 set of compliance figures can be easily duplicated between

a rubber surround cone / and a foam surround cone

all the manufacturer needs to do is control the hardness factor of the rubber surround material (ie the rubber)
and
the density of the foam material _ of the foam surround

with this surround material differance the sound quality of both the drive units will be entirely different

- along with the materials used the construction process is of importance

so is the x- max the voice coil inductance , the cooling efficiency

distortion - can be reduced by a symmetrical field magnet structure , shorting rings for eddys , shorting rings built into the coil to limit the coil from leaving the magnetic gap during extreme excursions

these important issues relating the drive unit is not reflected very much in the t/s matters

where am i going ?

i can copy a standard 100 $s subwoofer unit' s t/s parameter using

ordinary components for eg a pressed paper instead of a non press one , same coil dia , wire winding etc but with a poor insulation

and it will never play , last , sound as the original 100 $ s one

this is of utmost importance to diy constructors , along with t/s parameters

[hunter audio]

To cut down to basics - In a complete speaker construction procedure there are three stages :

1.determine the T/S parameters of the driver
2.run it through box design calculations / software with the cut off frequency size and type _ bandpass / bassreflex etc in mind
3.construct the box solidly assemble the speakers

then perform final measurements with a microphone plus software analysis of the speaker

upon this test result and personal taste
the crossover can be tweaked , notch filters and impedance correction put in and phase tuned

the above is nirvana but it does not include power handling , the sweetness required from hi fi speakers or the accuracy factor in professional audio / monitors
(this topic would go into realms if I have to put down all that comes instantly to my mind)

Reverting to important issues governing diy and speaker design

1 . The speaker matching with the amplifier ,

I can provide a double magnet (155 to 230 mm) subwoofer in a lambada extended pole underhung sfg topology magnet structure with a kapton voice coil with imported aluminum wire voice coil lengths in excess of 60 mm with a xmax of 25 mm at 4 ohms , a imported non-press paper rubber surround cone (which totally absorbs all mid + hi frequency due to the cone design)
and
if the user constructs the most powerful IC amp it will not match
infact it won’t match a 150 w rms transistorized design using latest Toshiba ets transistors
the reason – the magnet structure is over damped
now if it was the crescendo mosfet amp then we are going somewhere ,

Two

the type of the transducer , its power handling , has the voice coil size been increased blindly to increase power handling without magnetic efficiency and x – max in mind ?

the type of cone used , pressed paper , semi press paper , non press paper , felted composite , reinforced ets ( this decides how the speaker will sound )

the motor structure , sfg (symmetrical field geometry magnet structure) , for full range and pro drivers if there are eddy current shorting rings , other shorting rings employed to extend frequency response , linearise impedance , improve transience

the vc material and wire , the vc inductance – 2 layer , 4 layer , dual vc type etc

the suspension system and compliance
surround material , eg rubber then type natural or synthetic ets , the extent of the roll of the surround and its match with the spiders

the construction – at the end all parts of a speaker is held together by adhesives , the quality of adhesives used / and the process of manufacturing , for eg if I repair a toy with a epoxy hardener type adhesive and do not allow for the correct drying time …

at the end all manufacturers are increasing production speeds

[Timn8ter]

That must be why a Fostex FE103 sounds better than a RS 40-1197
But, there could be a reason I paid the price of one Fostex for 4 RS drivers, then damped the frame and dammared the cone. In almost every case, you get what you pay for and T/S parameters don't define tonality.