Theoretical question - differences between speaker systems

[bshorey]

I think that if you review the previous posts in this thread that you may change your mind (or opinion) on what is the purpose of frequency response measurements, and if done with care, what they can tell you about the sound that will be produced from the speaker in question. They can, and do, provide a great deal more information than you're aware of, based on your post.

Your example of the Bass Reflex and Acoustic Suspension enclosures sharing the same frequency response and yet would have different "volume curves" across the bass spectrum is just plain wrong. If the frequency response is the same, then both will share the same "volume curve." In fact, in very simple terms, that's what a frequency response is, the "volume curve" of the speaker across the entire designated frequency span (often shown as 20Hz to 20kHz, but can go lower and higher).

<snip>

I disagree.

Frequency response, by every definition I've encountered, means exactly that - the range of frequencies over which a device can reproduce sound. Nothing more. Now, it's generally followed by a min/max volume over that range, but taken by itself it implies none of the above.

So, if you want to qualify your original question that the frequency response will have +/- 0 db over said frequency response, and that it will be measured at every point on every axis, then I'll change my response to "I don't know".

But just because you made some assumptions in your original question doesn't mean I made the same assumptions!

I'm just picking nits here, there are some very good responses to the question, and I think that the question, which your assumptions, is a very interesting one.

bs

 

[ron-c]

I know how McIntosh and others measure it. They use a calibrated echoic chamber. This is the inverse of an anechoic chamber. You measure power response off axis of the speaker in a room that absorbs no sound. Room dimensions, temperature and humidity must all be accounted for for repeatable results.
Almost all serious pro sound speaker manufacturers use this technique as well as many consumer speaker manufacturers. Without this data accounted for in the speaker design you will not know how a speaker will perform in many unknown rooms.

Thanks,
Ron-C

 

[Zilch]

Power response is calculated from frequency response measurements taken using a loudspeaker tilt-a-whirl under anechoic or quasi-anechoic conditions....

 

[ron-c]

The speaker turntable in an anechoic chamber measures off axis frequency response at one point. Power Response is total radiated energy. Sound waves do follow the cabinet and are radiated out into the room off the speaker surfaces. If you do not have an echoic chamber you will have to calculate but the actual measurement will tell all.

Thanks,
Ron-c

 

[Zilch]

Almost all serious pro sound speaker manufacturers use this technique as well as many consumer speaker manufacturers. Without this data accounted for in the speaker design you will not know how a speaker will perform in many unknown rooms.

"Paging ..."

"Paging Ken Kantor...."

 

[TerryO]

I know of several very good speakers that were designed without a "special chamber." In fact, they were hoisted up on a forklift and measured with the microphone elevated to match. High tech? No it's not, but on a quiet night (pretty late at that!) well away from any boundaries, it does give reasonable results. By marking out the area beneath the speaker in a semicircle, with intervals at a predetermined number of degrees, off axis measurements can be done with fairly reasonable results.

There are, of course, many other techniques as well.

An automated, high tech facility is great if it's available and is almost certainly faster, but it's not the only possible way.

Best Regards,
TerryO

 

[RayW]

Frequency response, by every definition I've encountered, means exactly that - the range of frequencies over which a device can reproduce sound. Nothing more.

Not exactly. The frequency response is the response of the speaker at each frequency. Manufacturers, or more correctly marketing departments, distill this down to the numbers you're talking about...37Hz - 22kHz +/-3dB for example. The frequency response is actually better represented by the graph showing what's going on at each frequency within the realm of human hearing...and a bit beyond.

What hasn't been defined by the OP in his original query is whether he meant a single on-axis frequency response or the summation of on- and off-axis measurements (power response).

 

[TerryO]

Not exactly. The frequency response is the response of the speaker at each frequency. Manufacturers, or more correctly marketing departments, distill this down to the numbers you're talking about...37Hz - 22kHz +/-3dB for example. The frequency response is actually better represented by the graph showing what's going on at each frequency within the realm of human hearing...and a bit beyond.

What hasn't been defined by the OP in his original query is whether he meant a single on-axis frequency response or the summation of on- and off-axis measurements (power response).

Ray,

Another thing that hasn't been brought up about the amazing results of these Hi-Tech, well funded manufacturers (B*se?), is when they take their "Super Tech" speakers and advertise them with that elegant (1/2 octave smoothing) frequency graph or change the ratio on the x-y axis.

"Holy Helmholtz, Batman! That's one good speaker!"

Best Regards,
TerryO

 

[ken kantor]

Col. Sanders?

edit: Note, that's a joke. I know who they are, but that guy on the left looks a bit shifty to me.

"thiele and short"?

-k

 

[ken kantor]

Power response is calculated from frequency response measurements taken using a loudspeaker tilt-a-whirl under anechoic or quasi-anechoic conditions....

This is true in the modern world. Way back when response curves were chart-recorded or plotted point-by-point, averaging several was no mean feat...

AR used to have a concrete reverberant chamber. It was designed to integrate the radiated power of the speaker while introducing as little signature as possible. Once computers entered the picture, it quickly became obsolete.

http://www.kenkantor.com/publications/frequency_response/frequency_response.pdf

-k

 

[ken kantor]

Ken thanks again for posting here.

As a brief OT may I ask what you are working on these days? NHT is now under different ownership, correct?

Thanks to you, and several here. It's a good discussion.

Chris/Ken > Jensen > Recoton > Rockford > Vinci > Chris/Employees

More or less. I left early into the Recoton epoch, and so might be missing some of the later transitions.

These days, I am happily and completely absorbed making guitar amps.

-k