Ultra high end speaker manufacturers that rely heavily on measurements?

[thewas]

Ok reading quickly it appears that the DSP is indeed capable of creating the same filter as you can passively.

Of course it can but that is not the topic here, please read also the Purifi paper.

 

[mwmkravchenko]

The Purifi paper doesn't use or specify any MiniDSP, the reduction of the distortion (or lack of such) has nothing to do with it as it was replicated from few members here already.

We use this technique when we have to do passive crossovers to.

One is different from the other in that an active filter is driver temperature invariant. And the other passive filter network is dependent on driver temperature.

Mark

 

[thewas]

We use this technique when we have to do passive crossovers to.

One is different from the other in that an active filter is driver temperature invariant. And the other passive filter network is dependent on driver temperature.

Mark

These are two different topics, by the way the thermal increase of the resistance of the voice coil is is also an issue on an active crossover unless compensated with a special circuit like for example this one. Best of the world can be combing an active crossover with a passive notch filter.

 

[mwmkravchenko]

Ok looked through the thread more. No where yet have I seen the smoking gun of SPL, Phase and Impedance all on the same graph. With this we could start to see what is actually going on with this driver. Even if we had this to look at we do not know the electrical and phase response of the passive notch circuit in comparison with the active notch circuit.

So we are stuck with an anecdotal discussion of sound. Warmth from Fir bracing makes me cringe. Why would someone go through all this work and be looking to colour the output of a loudspeaker from the design stage on up? Oh well. Only my opinion. And it is as valid as this gentleman's opinion. He is listening to the loudspeakers right?

Mark

 

[thewas]

Ok looked through the thread more. No where yet have I seen the smoking gun of SPL, Phase and Impedance all on the same graph. With this we could start to see what is actually going on with this driver. Even if we had this to look at we do not know the electrical and phase response of the passive notch circuit in comparison with the active notch circuit.

So we are stuck with an anecdotal discussion of sound. Warmth from Fir bracing makes me cringe. Why would someone go through all this work and be looking to colour the output of a loudspeaker from the design stage on up? Oh well. Only my opinion. And it is as valid as this gentleman's opinion. He is listening to the loudspeakers right?

To which exact post are you referring to? I don't see any anecdotal discussion of FIR warmth of sound but objective comparison of distortion measurements in the links I had posted?

 

[mwmkravchenko]

Fir brace. Fir as in conifer tree, Fir wood.

I use PVA wood glue for the cabinet joints, but I like the polyurethane glue for braces since it expands, especially if you lightly wet the wood surface before gluing. The braces are kiln-dried Douglass Fir which should add warmth to the midrange. I’m not sure how long the front face of the cabinet is going to last since it will expand and contract much differently than the plywood cabinet.

2/3 the way down in post one under the cabinet photo. Maybe he is joking?

Mark

 

[fpitas]

Fur is certainly warm. Fir only differs by one letter.

/I'll let myself out

 

[fpitas]

Fir brace. Fir as in conifer tree, Fir wood.


2/3 the way down in post one under the cabinet photo. Maybe he is joking?

Mark

There is a conspicuous winky, so I'd say: yes.

 

[Keith_W]

I have read a bit of this. Now I am wondering how limited this MiniDSP crossover is. I don't use their products as I have not been impressed with them for a long time.

May I ask why?

 

[mwmkravchenko]

May I ask why?

For years they were so limited in what you could do with them. This may be changing!

 

[mwmkravchenko]

Of course it can but that is not the topic here, please read also the Purifi paper.

Nice paper! Well thought out filter.

I have a Purifi story.

In 2019 I was at the Loudspeaker Sourcing Show in Nansha. Philip Richardson introduces me to Karsten. I had given a presentation on using Open Source Software to model loudspeakers. We are an international team. Nimble, but not well funded like the big boys. So we use Open Source Software and do a lot of custom interface programming. I was able to help Karsten figure out how to do the vibration analysis for their woofer. The Purifi woofer!

Then I had a private client that wanted custom drivers. I generally do Aluminum cones as I have found them to be a good go to type of cone when you put the engineering time into making them work well. I designed an underhung driver for one of my OEM clients and he wanted something similar. From what he has told me he puts a bug in their ear how you can use an aluminum cone via this, that and the other. I told him a little to much I think What do you see next? Aluminum cone Purifi drivers.

I hope they work out well for them. To many times aluminum cones get a bad reputation because of poor implementation, and poor engineering.

Mark

 

[test1223]

The passive notch filter can reduce the corresponding peak related HD while the active doesn't, see

https://purifi-audio.com/wp-content/uploads/2022/03/220211_R05-Notchfilter.pdf

and

Active DSP DIY speakers, for testing a few ideas

FFLOTSAM (Fabricated From LeftOver Things Studio Active Monitor) Active DSP speakers, for testing a few ideas I had some stuff lying around; a few random Baltic Birch-ply panels, some countertop material, a few cans of partially used brown spray paint, and some not-too clumpy spar varnish (that...

www.audiosciencereview.com

Yes that is one main advantage.

One is different from the other in that an active filter is driver temperature invariant. And the other passive filter network is dependent on driver temperature.

Yes this is one of the main disadvantages since the whole filter curve can be altered by voice coil temperature changes. With an active system you "only" have a volume reduction and no filter slope changes.

 

[mwmkravchenko]

Yes that is one main advantage.

Yes this is one of the main disadvantages since the whole filter curve can be altered by voice coil temperature changes. With an active system you "only" have a volume reduction and no filter slope changes.

That is a unique set up they had there. They are sampling the impedance I believe and incorporating a sliding filter section. All this can be done via DSP, but it is possible that they are conserving DSP horsepower for other uses. I do not know all the complexities of this loudspeaker. I will save this post as I love the easy to see differences in the impedance versus temperature curves. Saves a lot of typing!

As for volume reduction and filter slope changes, that is entirely possible depending on what you have for a DSP. You can indeed have alternate filter slopes if you require. Limiters that are voltage variable as are filters that can be adjusted in similar ways. They track the impedance and then incorporate corrections on a prepared look up table. Not MiniDSP stuff obviously.

Mark

 

[pseudoid]

It's impedance increases and we are really only interested in Impedance because your amplifier is sending the loudspeakers an Alternating voltage signal.

Thank you for the very informative reply.
May I trouble you to also detail (graphs/xls/etc.) the effects of temperature-related impedance changes to the voice coil? Especially to the delivered sound.
...if, somehow the data can keep the cross-over thermal effects as a constant (even if it means cryo-cooling those passive components).

 

[mwmkravchenko]

Thank you for the very informative reply.
May I trouble you to also detail (graphs/xls/etc.) the effects of temperature-related impedance changes to the voice coil? Especially to the delivered sound.
...if, somehow the data can keep the cross-over thermal effects as a constant (even if it means cryo-cooling those passive components).

B&O Tech: Thermal Compression Compensation

#9 in a series of articles about the technology behind Bang & Olufsen loudspeakers Recipe for`Befuddled Speaker Enthusiast´ Makes: One individual with reduced faith in louds…

www.tonmeister.ca

I couldn't do better.

Cooling the crossover components will do nothing to stop this.

I think I am beating a dead horse here. I hope you figure this out after looking at the reference.

Mark