Why drivers sound differently?

celef

Member
2012-11-26 7:40 pm
I have played some with sb17 drivers, pp and paper and alu and satori and s-s’s, why do they all sound very differently even with matched freq responses and at low to moderat sound levels. some sounds upfront, some sounds layed back, some sounds big and round, some sounds pointy and edgy, why is that? Is the the cone material, is it the cone shape, or the small freq response differencies because i can not get a response that is 100% identical?
 
Good that you have taken the time to experiment and listen.
Could it be mechanical resonance at the bass end and higher frequency out of band resonances in the kHz range. Even out of the crossover range sounds can be audible at many DBs below the ref level, hence people using notches at 3,4,5,7 kHz as required on the bass/midrange.
I imagine the impulse response for all look different for starters.
Just my first thoughts regarding your question
 
Every particular affects the sound (100%)
Other than material, also the shape determines how the waves are formed and conveyed. It acts like a waveguide.
I prefer new materials, the paper cones look sooooo old !
Aluminum, carbon fiber, polypropilene ftalate and others ( Audax's aerogel ?!) present different grade of sound transmission ( the standing waves, the transversal ones, that form inside the cone) and the most important: the barrier from the sound coming ( well, that's not properly a sound) from the back, i.e. soundproofness
 

TMM

Member
2007-09-01 8:37 am
Australia
Frequency response is a type of linear distortion, but speaker drivers also produce non-linear distortion. Linear distortion means that when one or more of tones are played, the same number of tones are present at the original frequencies but have been altered in amplitude and/or phase. Non-linear distortion implies that extra tones have been created at multiples (harmonics) of the original tones and/or sum/difference frequencies where multiple tones are played simultaneously.

Looking at a harmonic distortion measurement is the simplest way of gauging the non-linear performance of a driver.

A driver that has perfect linear distortion can have terrible non-linear distortion and vice versa, therefore two different drivers which have been equalised to have the same frequency response will sound subtly different because their non-linear distortion performance is not necessarily the same. This is why, for instance, bass from a 4" woofer will never sound as clean as a 10" woofer even if you equalised the 4" driver to have the same low frequency extension - the non-linear distortion will be much higher when the 4" produces a loud bass note.
The lower the non-linear distortion, the more similar they will sound when equalised to the same frequency response.

It should also be pointed out that a difference of even 0.5dB over a wide frequency range is audible, so I would be extremely careful in declaring that two different drivers have been EQ'd to have 'the same frequency response' unless you have done so by very careful measurement in conjunction with a multi-band parametric EQ and listening to the speakers in exactly the same listening space with the drivers moved to exactly the same positions.

If you had two different drivers which you had perfectly normalised (using a DSP) to have both the linear AND non-linear distortion to match, they would sound the same. This is difficult/impossible to achieve in practice because you can only equalise a driver to a target frequency response on one listening axis (e.g. on axis, but not off-axis) and normalising or cancelling non-linear distortion of a speaker driver by DSP seldom if ever attempted.
 
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lowmass

Member
2016-01-26 12:46 am
different materials make unique sounds. While much can and has been done to suppress it, the "color" of each still comes through. I supose there are a number of other factors as well but I suspect this is the biggest one. If it wasnt then why such a push to achieve tru " piston"

BTW what TMM says about 0.5 db over wide enough range is audible is more true than most realize. This is easily heard using wide bandwidth drivers such as ribbons or planers where you can easily tailor the FR without crossing between drivers. My last experience with this showed less than 1 db changes from 1k to 5 k would make wood block go from artificial to convincing. It was surprisingly obvious to even those who have no interest
 
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In addition to what has been mentioned already, the decay characteristics of a driver can have a huge impact but isn't apparent on simple frequency response charts. I wouldn't even consider a driver without seeing its waterfall chart first.



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AllenB

Moderator
Paid Member
2008-10-18 11:31 am
a driver without seeing its waterfall chart
This is a waterfall of a pressure response at a mic location. I don't want to sound pedantic but I think it makes a difference. It would be different at another location. Some breakup region issues can remain unexposed.

celef, as a result of issues like this the drivers could sound more similar when suitably band limited.
 

celef

Member
2012-11-26 7:40 pm
Thanks for all info.

I have done some more testing and it seems that the small Freq response differencies in the low pass function makes all the difference (and the low freq output ofcourse)
I also tried using a fixed tweeter, and adjusted each woofer to get a good phase match to the fixed tweeter, the results where suprising to me

And yes It would be a very interesting test to use a very steep high and low pass filter so the there is only a clean bandpassed range to listen to, i think i need to get a minidsp
 
I think a lot of people put more weight on decay/waterfall measurements than is actually audible. Practical musical instruments have extremely long decays by comparison, so some mild ringing from driver itself is unnoticeable. It's easy to fall into the trap of putting more weight on types of measurements which seem like they are easy to subjectively evaluate (frequency response, decay) and ignore the ones that are more difficult to describe in words (harmonic distortion, intermodulation distortion).

A lot of people also find it very difficult not to have some expectation bias - e.g. no matter how well a metal cone driver is implemented into a multi-way system, making the breakup region completely and objectively inaudible by low-passing and notching it out, some people will swear black and blue that it still imparts a quality to the sound like metal bells or banging on a metal trash can lid. If you avoid the breakup region, the driver behaves completely pistonic so there should be very linear distortion (flat frequency response, very little decay), therefore the type of cone material used no longer imparts an audible difference in the sound*

As the OP found out, it's also very difficult to evaluate a single driver in a multi-way system because for e.g. how the mid/treble is implemented will subjectively impart a different quality on the bass. The best way is to learn how to measure and interpret the data, because ears are easily fooled.

*to avoid the breakup region completely, you may also need to avoid producing audible non linear distortion components at those frequencies. Cone breakup tends to 'amplify' non linear distortion produced by the motor, therefore a driver which breaks up at say 5kHz may only be usable up to ~1kHz (5th order harmonic at 1kHz = 5kHz).
 
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Breakup not only has time domain consequences but also spatial effects. The cone or dome will invariably stop moving pistonic and as a result the polar pattern will change. Together with that: ringing comes with level increases that will be audible. EQ-ing brings down level but the resulting power response also has changed.
Not that I reject metal cones btw. The advantage of pistonic motion in the passband could outweigh the resonance trouble. With a well executed Xover.