2.5-way DSP crossover - help

2234rew

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Hi @juicehifi Bernt

Can you help with setting up DSP crossover for this 2.5-way speakers.

It is only 2-channel full-range, and no subs - which simplifies things !

Wiring to only 3 drivers in total, as per photo below. There are 2 passive radiators

There is coaxial midrange (LMF) and tweeter (HF).

You can see what it looks like below but someone's description of how to setup the crossover (which i want to replicate in Audiolense) is:

The way this speaker works is that the LF has a 1st order low pass at around 300Hz (from memory) and at the same frequency you have a shelf filter on the LMF driver to raise it by ~6dB.
If you do this carefully you will end up with LMF and LF both working below 300Hz, LMF only working above 300Hz, and a flattish frequency response from the summation.
Then you need to do the crossover to the HF at around 2kHz. Apply the 2kHz low pass filter to both LMF and LF too. Can use a 2nd order but in active I'd recommend you go 4th order.

I'm confused how to do these shelf filter?
And how to apply both low pass and shelf to the midrange (LMF)?
And 2kHz low pass for both LMF (midrange) and LF (woofer)?

52230


52232
 
Last edited:

kevinzoe

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The way someone has told you how to construct the XO shows that the LF has 2 low-pass filters applied to it - one at 300Hz and another at 2Khz. This seems odd to me . . . If it were me, I'd ignore the low-pass filter at 2KHz for the LF bass driver as it's already been taken care of by the 300Hz one. If a second low-pass filter is needed by the LF driver then try reducing the width of the XO instead.

Regarding the shelf filter, I would think that the correction filter will boost the LMF automatically to try and match it to your target curve. Alternatively, if your speaker is tri-ampable and you are using 3 amps then turn up the LMF volume or turn down the vol of the other two amps.
 

2234rew

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The way someone has told you how to construct the XO shows that the LF has 2 low-pass filters applied to it - one at 300Hz and another at 2Khz. This seems odd to me . . . If it were me, I'd ignore the low-pass filter at 2KHz for the LF bass driver as it's already been taken care of by the 300Hz one. If a second low-pass filter is needed by the LF driver then try reducing the width of the XO instead.

Hi, this is the advice from one of the best speaker designers on the planet and how the speaker was designed with passive components.

He gave me this great starting point on how to approach DSP crossover but I don't want to bother him too much.

It was private message, so I've kept it anonymous out of respect for him helping me.

And at the end of the day, he doesn't use Audiolense anyway so I need some help from Audiolense community

Yes the 2 low pass filters which is why it is considered 2.5-way I believe

Any advice on how to achieve what I have quoted above, would be appreciated

I am happy to experiment after first trying the designers advice
 

brombo

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What are you using for a DSP crossover (hardware/software)?
 

2234rew

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What are you using for a DSP crossover (hardware/software)?

I have 10 channel Focusrite and Audiolense XO and Audiolense Convolver, so that is covered. I already have 3-way DSP DIY speakers.

I just need some assistance with:

1. how to do these shelf filter?
2. And how to apply both low pass and shelf to the midrange (LMF)?
3. And 2kHz low pass for both LMF (midrange) and LF (woofer)?

In Audiolense XO obviously.

It's a bit more complex than I'm used to.
 

brombo

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I am afraid I am only familiar with programming a mindsp openDRC-DA8 or Camilla software using a sound card (ASUS Xonar Essense STX ii 7.1) on a linux pc. I also use REM to measure the speaker response. I abandoned Windows long ago although these days Apple has taken its place as the Evil Empire. I guess you would call my system a 2.3 system configured as stereo with each speaker having a 3-way dsp crossover. The tower speakers are CBT36K's designed by Don Keele for Part-Express (no longer in production). Here is a link to Don Keele's web site for the theory - Don Keele - Constant Beamwidth Transducers

hometheater.jpg
 

juicehifi

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You can either do this with very wide crossovers ... or you could do it with driver overlap enabled ... where you can lowpass at at a high frequency and high pass at a lower. I believe a combination of the two should get you there. Audiolense will level it out no matter what.

Me personally I prefer regular crossovers where high pass and low pass have the same properties. They match up perfectly in the time domain. You will get a perfect global result also with driver overlap and different slopes on high pass and low pass, but the drivers will not work as perfect together as with a regular xo. This scenario is the same with analog crossovers, btw, but the time domain behavior is rarely emphasised as much there as it is here. And it is NOT a big deal, but big enough to give it a chance.

So if I were you , I would try to just get in the ball park of the speaker designer's idea by using a wide crossover.... at least as a starting point. If that doesn't turn out as planned ... opt for a driver overlap solution.
 

jjazdk

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It is not odd, but a common way to construct a 2.5 way passive loudspeaker. Often a shelving filter is not neccessary, as the lowpass filter for the bottom woofer (with the lowest frequency range) is chosen such that it accounts for the baffle step of he enclosure.

The way someone has told you how to construct the XO shows that the LF has 2 low-pass filters applied to it - one at 300Hz and another at 2Khz. This seems odd to me . . . If it were me, I'd ignore the low-pass filter at 2KHz for the LF bass driver as it's already been taken care of by the 300Hz one. If a second low-pass filter is needed by the LF driver then try reducing the width of the XO instead.

Regarding the shelf filter, I would think that the correction filter will boost the LMF automatically to try and match it to your target curve. Alternatively, if your speaker is tri-ampable and you are using 3 amps then turn up the LMF volume or turn down the vol of the other two amps.
 

brombo

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If you are still interested in understanding shelf filters here is a good reference -
Shelf Filters
One of the confusing things about shelf filters is you can specify a Q or a slope to define the filter. The highest Q you want to use is 0.707. Any higher and you get peaks in the filter response instead of a shelf.
 

juicehifi

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If you are still interested in understanding shelf filters here is a good reference -
Shelf Filters
One of the confusing things about shelf filters is you can specify a Q or a slope to define the filter. The highest Q you want to use is 0.707. Any higher and you get peaks in the filter response instead of a shelf.
Thank you but not so interested ( no pun intended) All those public eq filters are special versions ov biquads, which are IIR filters with four coefficients. Some 10 years ago I coded a gui where I could make peaking filters, dipping filters, XO-s and anything inbetween, below, over, left or right. There is a lot of possibilities outsude what is surfacing in even advanced GUIs, but I found absolutely nothing there that extended the opportunities to do something interesting.
I am confident that your speaker designer will agree with me if or when (s)he takes the time to get on top with FIR based correction.

Audiolense is not designed to mimic biquad behaviour in any shape. Life is too short.
 

brombo

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Ofer

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Thank you but not so interested ( no pun intended) All those public eq filters are special versions ov biquads, which are IIR filters with four coefficients. Some 10 years ago I coded a gui where I could make peaking filters, dipping filters, XO-s and anything inbetween, below, over, left or right. There is a lot of possibilities outsude what is surfacing in even advanced GUIs, but I found absolutely nothing there that extended the opportunities to do something interesting.
I am confident that your speaker designer will agree with me if or when (s)he takes the time to get on top with FIR based correction.

Audiolense is not designed to mimic biquad behaviour in any shape. Life is too short.
If you could eloborate on the xover filter design it would be greatly appreciated. A lot of "common" xover filters are likwithz reihly (or others) Xdb/octave (12db, 24db etc). In the help file the AL filters are designated just as x_octave. 1octave, 0.5octave, 3octave and so on. How is that translated to the slope of the octave. For example how many db/octave slope is a 1octave slope in AL?
Thanks
 

brombo

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Camilladsp does implement FIR filters but you would need a separate program to calculate the coefficients -

Camilladsp Filters
 

juicehifi

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If you could eloborate on the xover filter design it would be greatly appreciated. A lot of "common" xover filters are likwithz reihly (or others) Xdb/octave (12db, 24db etc). In the help file the AL filters are designated just as x_octave. 1octave, 0.5octave, 3octave and so on. How is that translated to the slope of the octave. For example how many db/octave slope is a 1octave slope in AL?
Thanks
The al filter does not have constant slope. They are very shallow towards 0 dB and very steep towards silence. Therefore, they are described by width instead of slope.
 

2234rew

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You can either do this with very wide crossovers ... or you could do it with driver overlap enabled ... where you can lowpass at at a high frequency and high pass at a lower. I believe a combination of the two should get you there. Audiolense will level it out no matter what.

Me personally I prefer regular crossovers where high pass and low pass have the same properties. They match up perfectly in the time domain. You will get a perfect global result also with driver overlap and different slopes on high pass and low pass, but the drivers will not work as perfect together as with a regular xo. This scenario is the same with analog crossovers, btw, but the time domain behavior is rarely emphasised as much there as it is here. And it is NOT a big deal, but big enough to give it a chance.

So if I were you , I would try to just get in the ball park of the speaker designer's idea by using a wide crossover.... at least as a starting point. If that doesn't turn out as planned ... opt for a driver overlap solution.

Hi @juicehifi

Will I essentially need to use 5 channels per speaker to do this?

And parallel wire drivers to amps?

For example the LMF driver needs both: shelf filter + 2kHz low pass filter applied.

And LF needs both: 300Hz 1st order low pass filter + 2kHZ low pass filter and

If you could help with showing me how a setup in AL could achieve this standard 2.5-way config, would be greatly appreciated, because I'm struggling.

Or if this is something that could be improved in AL's UI to allow for such XO cases.

The 2.5-way config:

The way this speaker works is that the LF has a 1st order low pass at around 300Hz (from memory) and at the same frequency you have a shelf filter on the LMF driver to raise it by ~6dB.

If you do this carefully you will end up with LMF and LF both working below 300Hz, LMF only working above 300Hz, and a flattish frequency response from the summation.

Then you need to do the crossover to the HF at around 2kHz.

Apply the 2kHz low pass filter to both LMF and LF too. Can use a 2nd order but in active I'd recommend you go 4th order.
 
Last edited:

juicehifi

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You can send me the measurement and I can show you how you can deal with this in Audiolense.
 

2234rew

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You can send me the measurement and I can show you how you can deal with this in Audiolense.

Hi Bernt

I have these passive speakers.

I don't want to make them active until I have an idea that it will be possible to get the speaker setup reasonably correct in Audiolense.

Once speaker setup in AL is closely matching what the designer has described above, I will then send AL's XO plot to the speaker designer for him to look.

If he says that's a good enough point, then I can be confident to open the speak and by-pass the passive crossover

And then do the measurements in AL.

So for now, I just want to setup the XO in AL so I can forward to the designer.

If you can help me with this speaker setup, I can do all the next steps.
 

juicehifi

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52992


With this configuration, driver 1 and 2 will share the load below 200 Hz and driver 2 will work alone between 200 and 3.5 kHz. Driver 1 will play 6 dB louder above 200 Hz than below, where two drivers will share the load.
 

2234rew

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View attachment 52992

With this configuration, driver 1 and 2 will share the load below 200 Hz and driver 2 will work alone between 200 and 3.5 kHz. Driver 1 will play 6 dB louder above 200 Hz than below, where two drivers will share the load.

Thanks so much Bernt, this is exactly the help I was looking for.

I had tried Variable XO width as you initially suggested (without driver overlap) but struggled.

The last part of the advice was applying 4th order low pass filter , for both driver 2+ 3 .

4th order recommended or otherwise 2nd order low pass filter.

How would I do that in the setup screen?

Something close enough

As @jjazdk mentioned above, this is pretty standard 2.5-way config but is new to me. And hard for me to setup in AL.

Maybe this thread can be used as a general guidance for future 2.5-way setup in Audiolense, and can help others.

The 2.5-way config:

The way this speaker works is that the LF has a 1st order low pass at around 300Hz (from memory) and at the same frequency you have a shelf filter on the LMF driver to raise it by ~6dB.

If you do this carefully you will end up with LMF and LF both working below 300Hz, LMF only working above 300Hz, and a flattish frequency response from the summation.

Then you need to do the crossover to the HF at around 2kHz.

Apply the 2kHz low pass filter to both LMF and LF too. Can use a 2nd order but in active I'd recommend you go 4th order.
 
Last edited:

NiToNi

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Hi, which speaker is this? What’s the baffle width (guessing 8”/20cm), size of drivers (guessing 6.5”) and current passive crossover frequencies and slopes (if different from those recommended to you by this designer)? And importantly, what’s the center-to-center distance between the LMF and the LF drivers?
 

2234rew

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Thanks so much Bernt, this is exactly the help I was looking for.

I had tried Variable XO width as you initially suggested (without driver overlap) but struggled.

The last part of the advice was applying 4th order low pass filter , for both driver 2+ 3 .

4th order recommended or otherwise 2nd order low pass filter.

How would I do that in the setup screen?

Something close enough

As @jjazdk mentioned above, this is pretty standard 2.5-way config but is new to me. And hard for me to setup in AL.

Maybe this thread can be used as a general guidance for future 2.5-way setup in Audiolense, and can help others.

The 2.5-way config:

Hi @juicehifi

Are you able to assist with this above?

Your proposed setup didn't account for: 4th order low pass filter , for both driver 2 & 3 (at 3.5kHz in your setup screen).

What would be the best way to add this?

This is the final piece.

Many thanks

As jjazdk mentioned in earlier post here, this is pretty standard 2.5-way config but is new to me. And hard for me to setup in AL. Maybe this thread can be used as a general guidance for future 2.5-way setup in Audiolense, and can help others.
 

2234rew

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Hi @juicehifi

Can you please help

How to do this "shelf filter @ 300Hz to raise it by 6dB"

I can't ask the speaker designer because this is completely Audiolense specific and he doesn't know Audiolense

53320
 
Last edited:

juicehifi

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It will happen when the correction is made. Everything you combine in a speaker ... including subwoofers... will be levelled.
 
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