A history of Time Aligned Loudspeakers

[Thomas_A]

I couldn't tell you. That's a great question and it gets complicated. We are in the modal region of the room so if you did Anechoic test would it hold up in a typical room? Are you sealed or a reflex box? Obviously it will be higher at box tuning but how audible at say 25Hz? That would be 40 msec to meet the 1 cycle "rule" depending on how much GD there is in the box and crossover.

When I set up subs I go for a null as it is much easier to hear and measure. Then reverse polarity under the best conditions you might see a 6db rise from mutual coupling more typically 3db. With a null it can go down 10db easy and deeper depending on how close the phase match is through the crossover. I don't worry about the GD as long I get good summation through the crossover.

The other issue is obviously wavelength. At 80 Hz it's 14ft. So with placement are your subs 14ft away or one cycle? I doubt it. That's why a variable phase control is better than simple polarity switch.

Rob

It is audible in room below 1 cycle, done my ABX both with music and signals. Threads exists already about this. But I don't claim its importance or what is preferred since we do not know phase shifts that already are in the mix.

This is very audible for me headphones or speakers in room. Which is a test signal ok, but it works on music as well. 123 Hz saw tooth 1 s followed by the same but all pass 150 Hz Q 0.7

Dropbox

www.dropbox.com

 

[Trifonov Audio]

I was merely pointing to the effects of distortion and the use of passive components. Active solutions seldom take that into the equation.

Low Distortion Filter for PTT6.5X04-NAA

purifi-audio.com

Good peak smoothing from Purifi! But why doesn't anyone (or almost anyone) develop and non publish (subsequently) good summary Step Responses? Surely it's not "important" or very difficult to achieve without DSP?

 

[Paul7777x]

KEF are not time aligned? Look at the Blades impulse response,

Rob

Hard to get better without taking pains with an active set up and very well sorted DSP.

 

[Thomas_A]

Good peak smoothing from Purifi! But why doesn't anyone (or almost anyone) develop and non publish (subsequently) good summary Step Responses? Surely it's not "important" or very difficult to achieve without DSP?

There are more examples here at ASR.

Purify / Low Distortion Filter for (Rigid Cone) Mid-Woofers

Here you might find some info on how to prevent to emboss the distortion profile of rigid cone woofers by the common resonant peaks. See article "Low Distortion Filter ... " at https://purifi-audio.com/tech/ I never thought that would be possible, often told people otherwise, but here you are...

www.audiosciencereview.com

Regarding step response, I am not sure what you are asking. GD limits vs. frequency or?

 

[Cbdb2]

Thank you, @LSPhil, perhaps (rarely seen or used or available) consider the Avantgarde CPC circuit....

• 2nd order behaves like 1st order/In Phase, Eliminates Crossover Distortion, etc....

View attachment 535035 View attachment 535043

When I searched the web for this I could find no info. Capacitor distortion is relatively easy to make inaudable. If you look at the electrical equivalent for this CPC I cant see how it inverts phase. Am I missing something? And even if it did how will that change the phase shift when using it in a filter, you just invert the signal.

 

[robh36062]

Hard to get better without taking pains with an active set up and very well sorted DSP.

I agree

Rob

 

[gnarly]

O-oo, I personally know the chief designer of BMS. A brave, ultra-innovative inventor!
The idea with many drivers to one horn is awesome!!
Bravo, congratulations!!

Thank You! Yes, BMS products are plain excellent aren't they. The many drivers in one horn idea is all Tom Danley...I just plagiarize

Thank you, @gnarly, what are the Box Dimensions....

You bet. Box is 46"W x 27"H x 26" deep.
I should say was. I ended up trashing the pair of the big guys, and putting their drivers in a smaller syn-horn setup.
Who says all DIYers think their designs are nothing but the best haha.

The pair of 18"s simply weren't producing the SPL and extension I wanted, and made the box internally awkward. I think a pair of 15"s are what the design needed, and will be my next 5-way attempt in one box effort.

(I had to go look up the old build thread on DIY to find the dimensions ......here's the page from the thread with them https://www.diyaudio.com/community/threads/syn-11-a-one-horn-5-way.393087/page-5#post-7378487

 

[gnarly]

Oh, don't cry so much — just tilt your speakers back a few degrees and you'll have time alignment

Lol...who's crying, and about what?
And oh, my DIY speakers don't need tilting

 

[kimmosto]

Below one cycle at 150 Hz but how low?

LR24 is audible below ca. 350 Hz so the answer is "less than 0.45 cycles below 350 Hz". I can try to search the highest audible XO frequency with LR12. That produces delay peak of 0.16 cycles which is also audible in some point. Months ago I tested LR12 with 100 Hz XO which was audible, but not bad such as LR24 at the same point.

 

[Thomas_A]

LR24 is audible below ca. 350 Hz so the answer is "less than 0.45 cycles below 350 Hz". I can try to search the highest audible XO frequency with LR12. That produces delay peak of 0.16 cycles which is also audible in some point. Months ago I tested LR12 with 100 Hz XO which was audible, but not bad such as LR24 at the same point.

Ok. I've done any systematic tests so I do not know the lower limit, and don't remember if I've seen any published at these fr either.

 

[KL....]

When I searched the web for this I could find no info. Capacitor distortion is relatively easy to make inaudable. If you look at the electrical equivalent for this CPC I cant see how it inverts phase. Am I missing something? And even if it did how will that change the phase shift when using it in a filter, you just invert the signal.

Thank you @Cbdb2, it (definitely) works but let me have look for a good/better Technical explanation (if I can find one better than already shown?). Reasoning thus far is that the (single) Capacitor (with CPC circuit) acts as a DC block, HPF, without inverting the Phase (in Phase), while eliminateing Capacitor (Dielectric Chargeing) XO Distortion (ie Signal transfer is (Truely) Transparent)....

It could be suggested that they do not desire to show the construction....

 

[Trifonov Audio]

There are more examples here at ASR.

Purify / Low Distortion Filter for (Rigid Cone) Mid-Woofers

Here you might find some info on how to prevent to emboss the distortion profile of rigid cone woofers by the common resonant peaks. See article "Low Distortion Filter ... " at https://purifi-audio.com/tech/ I never thought that would be possible, often told people otherwise, but here you are...

www.audiosciencereview.com

Regarding step response, I am not sure what you are asking. GD limits vs. frequency or?

In modern parameter measurements, they are all directly interdependent.
But if we observe only the frequency response and the phase, there may be a miscalculation! For the first derivative of the phase - GD, also may be different interpretations. For this, it is safest and calmest to work with Impulse (Step Response)!

 

[prerich]

I used to own Bag End M6 speakers that were Coaxial and Time Aligned. They were beautiful, finished in an automotive Mercedez black. Those were over $1000 each with the paint job. I had 3 and sold the set for $500 plus shipping. They were wonderful, but when required to do heavy lifting in a bigger room...there's nothing like a floorstander.

 

[Salt]

If the basically impulse is a clean one, GD and FR should follow this, not?

 

[Trifonov Audio]

Hard to get better without taking pains with an active set up and very well sorted DSP.

Let someone else tell you - is this a good time alignment?
To robh36062 is the question.....

KEF Blade Two, step response

 

[robh36062]

LR24 is audible below ca. 350 Hz so the answer is "less than 0.45 cycles below 350 Hz".

Hello is this in headphones? Also I don't understand why the numbers you have are well below the numbers in the peer reviewed studies? The sensitivity to group delay goes down with frequency not up. WRT L/R 12 and .16 cycles at 350Hz is approximately 60 usec ? The most sensitive region is 1-4k and that is well below the thresholds there.

Rob

 

[KL....]

Let someone else tell you - is this a good time alignment?
To robh36062 is the question.....
View attachment 535111
KEF Blade Two, step response

Apologys, not @robh36062, although....

Audio Perfectionist Journal

 

[robh36062]

Apologys, not @robh36062, although....

No issues for a passive speaker it's not perfect. Decide for yourself. Edited not Time Coherent.

Rob

KEF Blade Two loudspeaker Measurements | Stereophile.com

Sidebar 3: Measurements I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the KEF Blade Two's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield and spatially averaged room responses. The Blade Two's voltage sensitivity is specified as...

www.stereophile.com

 

[KL....]

No issues for a passive speaker it's not perfect but it's time coherent. Decide for yourself.

Rob

KEF Blade Two loudspeaker Measurements | Stereophile.com

Sidebar 3: Measurements I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the KEF Blade Two's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield and spatially averaged room responses. The Blade Two's voltage sensitivity is specified as...

www.stereophile.com

Thank you, @robh36062, John Atkinson suggests that the KEF's Blade Two offers superb measured performance that is close to the state of the art....
Are you are also suggesting this for the same reasons as John Atkinson....

In the time domain, the Blade Two's step response on its tweeter axis (fig.9) indicates that the tweeter is connected in inverted acoustic polarity, the midrange and woofers in positive acoustic polarity. More important, the decay of the tweeter's step smoothly blends with the rise of the midrange unit's step, and the decay of that unit's step smoothly blends with the rise of the woofers' step. This suggests optimal crossover design. Finally, the KEF's cumulative spectral-decay plot on the tweeter axis (fig.10) demonstrates superbly clean decay from the midrange upward.

 

[robh36062]

Let someone else tell you - is this a good time alignment?
To robh36062 is the question.....

I think you are forgetting how this thread has progressed. The OP said that KEF's are time aligned. I posted the Theil and the Blade as well as another KEF in a later post where the UniQ was not time aligned to show the difference to the Thiel. So I know it's not optimal compared to the Thiel. It is however a perfect example of a Time Coherent system where the time offsets in the STEP are below the audibility threshold.

Rob