LouReed with new carbon cone speakers

This summer the shipment of our brand new carbon fiber speakers finally arrived.

The first listening test worked out quite promising, so we decided to upgrade our LouReed systems with these babies.

Nico is going to use a set of these speakers for some complicated acoustic performances during itgwo , so the design goal of the adjusted filters would have an emphasis  on producing a clear natural sound.

As opposed to rocking your guts with e.g. Rammstein, that is.

Probably Sebastiaan will call this boring (I guess) :)

By looking at the speaker you might expect a really full bottom-end with long excursion bangs of the speaker like 'car' hifi speakers do.

Not so!

Fortunately in this case 'cause that would bring also a lot of intermodulation distortion. Think thumping yourself on the chest while singing. Not looking for that in this case.

So why a rubber surround? 

As is the case with al stiff materials in speaker design, shurely they sound a lot better: stiffer cone -> stiffer piston movement -> less break up distortion.

But when they do breakup (and at at 'our' levels they always do): HORROR.

Remember the 2' titanium vs 2' aluminium driver diafragm 'upgrade' problems?

Or the special sound of that A brand line-array with yellow speakers for everything, when you hit it real hard?

Well here comes the genius of our Chinese friends: the rubber surround will absorb those hard breakup modi! Brilliant!

 

I also tested a other speaker in the same cabinet.

From the front the cone looks like your standard 12' (guitar) speaker.

Soundwise this gives you that nice zzhangg you are looking for in metal guitar a la Rammstein.

Not that pak-pak from a modern plastic coated speaker (think 'french' PA's).

So what's the Chinese ingenuity here? Back Coating! 

Al the advantages of a stiffer cone by coating without the ugly breakup. Again brilliant!

So in fact we now have two recipes for our LouReed systems

Does this mean a different magnitude/phase slopes of the overall response?

No, certainly not, actually the final results show quite simular curves.

Does this mean different EQ needed to match or linearise the responses?

No, also certainly not, actually in both designs zero EQ was applied.

(to the speaker that is)

Shurely, different program material makes me want to apply different micro EQ (no more then 3 dB, Q<2, that is), but I always end up in bypassing them again.

Which will have to bring me to the next topic:

Distortion matching as a design goal in loudspeaker tuning

oh, euh, yes, by the way: all the time we are talking distortion here I mean that very-fine-grained-hardly-noticeble but still quite -important-emotion-wise effect for which I don't know how to quantify else then by using my ears...

Valid dual FFT measurement

On several instances last week I have been talking to people how to acquire valid  dual FFT measurements.
It really stroke my how much miss understanding there still floats about, so here we go:
Crash course measurements in KBLsystems-style:

First::
Dual FFT means we can finally get rid of that annoying pink/white noise at terrorising levels.
Just use your favorite music!
As long as it contains enough spectral content it will be a perfect source and you can use both eye and ear in your system tuning.
Keep a keen eye on your coherence tracer to see if your program material works.

Second:
Surely you can use the 'delay finder' function to find the overall time difference between the reference signal and the measurement signal, but be aware that all software will make this snap to the maximum of the impulse response which can be
a) quite challenging when the IR is smeared over time e.a. in a filtered sub respons
b)  will yield the 'wrong' phase response

Let me elaborate the latter:

 

This represents a close mic measurement of mid speaker. Clearly one can see the low end magnitude roll-off and it's associated phase behavior of a small speaker in a closed cabinet.

In the following picture the above graph shows  the IR with the delay finder nicely snapped to the maximum of the IR:

We will now show you why this is wrong.

The high end roll-off in magnitude which is (partly) due to the inductance of the voice coil should also find its counterpart in phase behavior. But in above graph one is to believed that this would not be the case.

Next picture is a simulation I made:

 

The black ine is the imported measurement and the red line is a constructed model based on this measurement.

The thin red line show the associated (min.) phase behavior.

So the measured phase should look like this. In fact the thin black line all ready shows the 'correct' trend.

Now how do we acquire this?

Simple! 

Adjust the delay finder by hand to the ONSET of the impulse response:

Tada!

Valid measurement!

Now bust your heads on what I 'm actually doing here <grin> ;)

LouReed rises again..

More over one and half year ago one of our 'LouReed' sound systems was stolen from a parked van.
Surprise, surprise  a attentive civilian found this in the woods recently:

Shock and horror, our meticulously crafted cabinets tossed away!
Probably not useful for the people who stole them as they need to be operated with a separate (FIR-filtered) X-over to get anything like alone a decent sound.

Today I have been refurbishing them and to my really big astonishment: the 12" speakers are still full-spec functional. Hooray for mr Simon Leung (A&Daudio) for the excellent manufacturing quality!
The 1' drivers were less fortunate, not that they would be of lesser build quality but of course these are a lot more vulnerable.

So here comes LouReed Phoenix..
While we are at it we will also update the FIR filtering for these cabinets.
For those interested in FIR: Thomas Drugeon (AKA pos) made this excellent utility:

rePhase

And, oh, yes, I also made a quad amplifier using Hypex UCD400 blocks and a switchmode PSU.
If now we could find some decent DSP modules (with FIR!!) we then finally could make our powered cabinets.. (nah, sorry no minidsp, nice but not stable enough for our "pro-audio-abuse").
Might have an other idea though..will get back to ye.