How do the companies measure and publish Freq. response graphs

[Naveenbnc]

Hi all ...

I am just curious to know how the driver companies measure the frequency response graphs.

Do they hang the driver in free air with some strings and measure?
Do they put it on a bench (driver facing upwards) and measure?

Or... do they mount the driver on a baffle and measure?
If they mount on a baffle, can we expect a "nearly similar" response (at least roll off points) when we make OB with that driver?

(OB design itself can be very meticulously done with lot of fine tuning, but I am just asking a very generic question)

 

[Naveenbnc]

thank you yogibear ..... the main reason for asking
I want to figure out how much low end extension a particular driver can give in an OB.

I did not learn OB simulation yet.
So if the frequency graph (in the driver specs) is drawn by mounting it on a baffle.....the graph can be some what near to OB
(this was my assumption .... I know its not ideal... but just an indirect way to guess the roll off in OB....)



The above is the FR graph given in a driver spec.
From the graph, it starts to roll off at around 160-170hz
If this is drawn (by the company) by mounting it on a baffle,.... the low end roll of in an OB can be in the same region.
As i said that was my guess... i could be wrong though ...

 

[Naveenbnc]

just to add... my interest was only to estimate the low end roll off in OB.
Not the performance over the entire spectrum ...

 

[diyaudio]

Some of the answers can be found at http://www.linkwitzlab.com/models.htm
Do take special note of response below Fequal

 

[diyaudio]

The difference between infinite baffle or OB becomes an issue below a certain frequency which is determined by the size of baffle in case if OB. Below this frequency the OB starts to roll of at rate if 6dB/octave. It needs more and more excursion from the driver.
Above a certain frquency determined by the size of the driver the OB becomes dipolar means it becomes too directional, the front and rear waves cannot meet and OB loses its not dipole nature. True dipole operation is about an octave or two atmost

 

[Naveenbnc]

thanks a lot yogibear and diyaudio for all the guidance ....

linkwitz scares me with too much depth in the subject .....
but reading multiple times gives more and more clarity .... im on it ...

 

[Naveenbnc]

Don't worry. I am working on an easy to understand OB package for you......

This will be a great help for me and many others

So the risks associated are yours !

this is absolutely fine

 

[kapvin]

If you mean speaker component manufacturers, Most use an IEC baffle in an anechoic chamber. (you can google IEC baffle) so ideally the mic would not pick up any reflected sound. In your own room you will also deal with reflected sound, so placement plays a pretty important role.

For manufacturers of finished speakers, its on their whim. Most specs include room response and room and boundary gain. And a healthy dose of optimism

 

[Naveenbnc]

Thank you Kapvin and yogibear...
Now I clearly understand how companies take the measurements.

 

[Naveenbnc]

Above is strictly a midrange driver with nice high end extension. Would work fine in OB if you intend to cross it above 200 hz and 8-9K hz.

That is none other than Sk12Frx Ahuja

Somehow I'm still clinging to that driver. I want to move over and try better drivers. But in that similar price bracket, looks like there are no drivers that can outperform Sk12Frx. Atleast I could not find one yet.

Many people in our WhatsApp group are already fedup with Ahuja topic

 

[Naveenbnc]

Ha ha ... But it explains why you complain about low end in OB. However from graph it will be surprising to know that it does not need tweeter support for the top end.

No....it doesn't need a tweeter. Gives decent highs. When hooked to a good dac, it shines even more. One serious drawback is that it needs a huge box to give low end.

I need a full range driver to build my 5.1 ht. It should cover all the highs, mids, and need to go down to 80hz in a compact box. Couldn't find anything like that yet. So this Ahuja is still laughing at me

 

[Naveenbnc]

Exactly.... And this one costs 14 to 1500 only