Digital speaker crossovers and room correction discussion

[HAL]

Is there any interest in digital crossovers for speakers and digital room correction discussions?

Been working with both for many years and will be happy to discuss ideas and equipment tried along the way.

[Nick B]

I'd welcome your insights and experience
Nick

[HAL]

So far the list of DSP based crossovers has been:

Behringer DCX2496 (own)
DEQX 2.6P (own) (and newer listening to demos)
MiniDSP (listening to demos)
Danville Signal Processing dspMusik LCD (own)
Perpetual Technologies P-1A for SOCS (own)

Room correction:

MathAudio RoomEQ (own)
Dirac (listening to demos)

Room measurements:

Room EQ Wizard (use)
CLIO (own)
CLIO Pocket (own)
MMK speaker measurement system (co-developed)

Presently the best sounding of the group to me with the Megalith speakers here and others tried is the dspMusik and RoomEQ.  Both have easy setup capabilities and very flexible.   

Only takes very simple measurements to get RoomEQ working and sounding very good in my room.

Not heard everything, but have heard other systems as well at shows.   

To me the most audible part of great DSP crossovers is the ability to capture the soundfield with very accurate channel to channel crossover matching that is extremely difficult with passive components due to their tolerances.  When accurate time delays are needed, it is very easy to add.

I use room correction as part of room tuning.  First are the acoustic treatments (absorption and diffusion) to correct for the normal room bounce problems and bass absorption.  Then use RoomEQ as the last step to integrate the speakers and room.  Done this way has given excellent results in my system.

Hope this starts a conversation.

[rollo]

Hey Hal glad to see you contributing. You are expert enough, thanks for the input.


charles

[dBe]

Great to see you posting. You have the Window applications wired!

Cool, let's see what drives this method.

You know that I tried for several years to get a Windows machine sounding the way I wanted.  Still have it.  Lead on Dartanian!!!

[Nick B]

So far the list of DSP based crossovers has been:

Behringer DCX2496 (own)
DEQX 2.6P (own) (and newer listening to demos)
MiniDSP (listening to demos)
Danville Signal Processing dspMusik LCD (own)
Perpetual Technologies P-1A for SOCS (own)

Room correction:

MathAudio RoomEQ (own)
Dirac (listening to demos)

Room measurements:

Room EQ Wizard (use)
CLIO (own)
CLIO Pocket (own)
MMK speaker measurement system (co-developed)

Presently the best sounding of the group to me with the Megalith speakers here and others tried is the dspMusik and RoomEQ.  Both have easy setup capabilities and very flexible.   

Only takes very simple measurements to get RoomEQ working and sounding very good in my room.

Not heard everything, but have heard other systems as well at shows.   

To me the most audible part of great DSP crossovers is the ability to capture the soundfield with very accurate channel to channel crossover matching that is extremely difficult with passive components due to their tolerances.  When accurate time delays are needed, it is very easy to add.

I use room correction as part of room tuning.  First are the acoustic treatments (absorption and diffusion) to correct for the normal room bounce problems and bass absorption.  Then use RoomEQ as the last step to integrate the speakers and room.  Done this way has given excellent results in my system.

Hope this starts a conversation.

Rich,
You mentioned using room eq as the last step. Wouldn't excellent software be able to correct for deficiencies without using acoustic treatments? Also, I was on the Amarra site tonight which is Windows compatible. It seems to be a Swiss army knife of sorts. Your thoughts on it?
Nick

[richidoo]

Room correction only fixes the spot where you measure. Treatments affect the whole room.

[HAL]

To me room correction with treatments helps to minimize the need to use software correction.   Have heard both methods with full room treatment only and systems like Tact/Lyngdorf without room treatment, but it sounds more natural to me with treatments and then correction.

The correction systems have a limit as to how long they can correct the response.  Any room artifact outside that will not be corrected.  This is another reason to minimize the room artifacts to begin the process.

I have not used Amarra, so cannot comment.  Others may have and would be good to see their comments.  I run Foobar2000 with RoomEQ as the player and room corrector.  Keeping the user interface as simple graphics is good from my experience. 

[Nick B]

Thanks, Rich(es),
As you are both of the room correction first method, that works for me. I'll order a mic and do the testing. 
Nick

[steve]

How fine of adjustment can be had with a digital crossover?

Cheers

Steve

[HAL]

Any of the crossover types can be adjusted for Fc in 1Hz increments.

[steve]

Any of the crossover types can be adjusted for Fc in 1Hz increments.

I would assume that amplitude adjustments are almost always continuous? Do they have something similar to a zobel network adjustment, but digital? If so, is there a digital correlation to capacitor and resistor adjustments?

Cheers

Steve

[HAL]

The equivalent is a peaking filter that has both gain and attenuation.  You set the gain(or attenuation in dB) center frequency and Q you want.  You can measure the original analog crossover and then adjust parameters in the software.

It does not simulate the crossover at the RCL level like SPICE. 

Amplitude adjustments in the scaling blocks are floating point math precision. 

[HAL]

If you are using a Zobel network to correct the impedance of a driver with a parallel network to work with the passive crossover, then it is not needed for the digital crossover.   If it is due to the driver impedance loading on the amp for feedback stability, then the Zobel network would still be required.

[steve]

If you are using a Zobel network to correct the impedance of a driver with a parallel network to work with the passive crossover, then it is not needed for the digital crossover.   If it is due to the driver impedance loading on the amp for feedback stability, then the Zobel network would still be required.

I may not have been clear with my question, which I apologize for. I have heard digital crossovers in systems (at shows etc) and still find the "sound" wanting. I am attempting to ascertain the reason.

My first comment is, I have never heard an amp directly connected to a driver have a flat response. The driver frequency response varies with frequency, is impedance related. A zobel attempts to flatten not only the impedance, but also the frequency response over a broad frequency range. This means extremely minute changes, not only in the analog realm, but in the digital realm as well.

For general information, the digital crossover would have to simulate a capacitor and resistor combination (simulate impedance change VS frequency) and be variable to extremely minute levels. I shall give you an example.

I am matching the amplitude level my full range driver to amplitude of the woofer in my test speakers, to 1 part in some 200,000. I am adjusting the full range driver zobel network resistance by less than 1 part in 20,000. Are the very best digital crossovers capable of such minute adjustments? Just asking.

Lastly, what about the need to AD as well as the DA when working with analog? Has those distortions been taken into account? (Distortion is anything that corrupts the music.)

Cheers

Steve