Active Crossover Measurement Technique

[Dan Waleke]

I've done some searching and I looked through the help file and I didn't really see much specific information on this topic.

What is the best way to perform measurements when using Audiolense XO for active crossovers?

I've seen a lot of people take nearfield measurements for the active crossover part and then measurements at the main listening position to correct the room.

I have a 5.2 surround sound system and I am considering removing the passive crossovers from my speakers and just let Audiolense handle everything active.

Is there documentation that I can read specific to how measurements should be done with Audiolense?

[Bernt Ronningsbakk]

The best way is to measure everything from the sweet spot.

 

The filtering in Audiolense is capable of removing reflections that should not be accounted for.

 

I recommend that you protect your tweeters with a capacitor if you decide to go all digital. Use one that cuts the signal high enough to save the tweeter in case of a full range signal.

 

Going all digital leaves more work and judgment to you. You will be doing the speaker design work yourself. But it is worth doing if you want the best possible sound quality.

 

A lot of nonlinear distortion will be eliminated when the power amp is connected directly to the drivers. But how and where you set the crossovers will  have a substantial influence on the sound quality too. I recommend a systematic, experimental approach, but you should do your homework and get the specs on those drivers. Find out their ideal working range, when the drivers start to break up at high frequencies, and how low you can use each driver before the capacity becomes an issue.  Also, although not quite as important, it is a good idea to address dispersion pattern of each driver and the speaker as a whole. Aim for a smooth change of dispersion through the crossover. But to me the dispersion is 3^rd priority. It is much more important to limit the drivers from operating outside their low distortion frequency range.

 

There is room for a vast improvement in sound quality compared to a passive crossover. Even if your passive and corrected speakers sound totally undistorted, you should achieve a significant improvement in purity and clarity when you go digital. It will sound more dynamic and detailed, yet more organic. When you start off with a passive speaker, provided you know the crossover frequencies, you should expect to achieve improvements pretty fast too.

 

Kind regards,

 

Bernt

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[Bernt Ronningsbakk]

We can do a discussion on it when you get there – if you decide to do this, Dan

 

Kind regards,

 

Bernt

[Dan Waleke]

Thank you.  

The speakers that I have are JTR 212HT for my L/R and a custom JTR 228HT w/212HT coaxial compression driver (to match L/R), but 8" woofers instead of 12" for a smaller cabinet.

The Tweeter/Mid is a coaxial compression driver - BMS 4593ND mounted to an 18Sound XR1464 60x40 pattern horn with 1.4" throat.  BMS recommends a 6.3Khz between tweeter/mid (300hz->22khz) and the speakers have a ~400hz crossover to the woofers (MTM design).  I have attached some graphs that I was able to find on the BMS driver.   I do not have any data on the woofers unfortunately.   I plan on using midbass modules for the left/right speakers between 60-180hz.  So the MTM woofers will only play between ~180-400hz.

It seems as long as I stick to similar crossover points I should be able to achieve pretty good results to start.  At least that is my hope.

Based on what I have posted can you recommend the right capacitor to protect the tweeter?

[Mitch Global]

Re: protecting compression drivers and selecting the right capacitor value.  Have a look at the guidance from JBL attached to figure out the proper values..  I use Solen Fastcap:  https://www.solen.ca/pdf/solen/fastcap.pdf and have measured and listened to them in and out of the circuit and could not measure or hear a difference.  Based on the price of the BMS drivers, well worth the protection.

The BMS compression drivers are very nice.  I use a BMS 4540 with a QSC constant directivity waveguide and very happy with the sound quality and coverage.

Good luck with your project!

[Bernt Ronningsbakk]

5uF will give a 1^st order cutoff around 3 kHz. 10 uF will cut around 1.5kHz.  I would go for the 1.5kHz if the driver can handle it. The capacitor will then interfere less (close to none) with  operating range you’re getting at. The specs on the driver does not tell give a good indication of what it can handle of “low” frequency short term power. I recommend that you ask the manufacturer about that.

 

Perhaps some of the users here have experience with similar drivers?

[Bernt Ronningsbakk]

Excellent info, Mitch!

 

Kind regards,

 

Bernt

 

From: audio...@googlegroups.com [mailto:audio...@googlegroups.com] On Behalf Of Mitch Global
Sent: Wednesday, March 04, 2015 5:04 AM
To: Audiolense User Forum
Subject: Re: [audiolense] Active Crossover Measurement Technique

 

Re: protecting compression drivers and selecting the right capacitor value.  Have a look at the guidance from JBL attached to figure out the proper values..  I use Solen Fastcap:  VIPRE Anti-phishing removed a known bad URL from your email message. It was deleted or quarantined and replaced with this message. and have measured and listened to them in and out of the circuit and could not measure or hear a difference.  Based on the price of the BMS drivers, well worth the protection.

 

The BMS compression drivers are very nice.  I use a BMS 4540 with a QSC constant directivity waveguide and very happy with the sound quality and coverage.

 

Good luck with your project!

On Tue, Mar 3, 2015 at 4:20 PM, Dan Waleke <d...@nowkw.com> wrote:

Thank you.  

 

The speakers that I have are JTR 212HT for my L/R and a custom JTR 228HT w/212HT coaxial compression driver (to match L/R), but 8" woofers instead of 12" for a smaller cabinet.

 

The Tweeter/Mid is a coaxial compression driver - BMS 4593ND mounted to an 18Sound XR1464 60x40 pattern horn with 1.4" throat.  BMS recommends a 6.3Khz between tweeter/mid (300hz->22khz) and the speakers have a ~400hz crossover to the woofers (MTM design).  I have attached some graphs that I was able to find on the BMS driver.   I do not have any data on the woofers unfortunately.   I plan on using midbass modules for the left/right speakers between 60-180hz.  So the MTM woofers will only play between ~180-400hz.

 

It seems as long as I stick to similar crossover points I should be able to achieve pretty good results to start.  At least that is my hope.

 

Based on what I have posted can you recommend the right capacitor to protect the tweeter?

 

 

On Tuesday, March 3, 2015 at 12:41:17 PM UTC-5, BerntR wrote:

The best way is to measure everything from the sweet spot.

 

The filtering in Audiolense is capable of removing reflections that should not be accounted for.

 

I recommend that you protect your tweeters with a capacitor if you decide to go all digital. Use one that cuts the signal high enough to save the tweeter in case of a full range signal.

 

Going all digital leaves more work and judgment to you. You will be doing the speaker design work yourself. But it is worth doing if you want the best possible sound quality.

 

A lot of nonlinear distortion will be eliminated when the power amp is connected directly to the drivers. But how and where you set the crossovers will  have a substantial influence on the sound quality too. I recommend a systematic, experimental approach, but you should do your homework and get the specs on those drivers. Find out their ideal working range, when the drivers start to break up at high frequencies, and how low you can use each driver before the capacity becomes an issue.  Also, although not quite as important, it is a good idea to address dispersion pattern of each driver and the speaker as a whole. Aim for a smooth change of dispersion through the crossover. But to me the dispersion is 3^rd priority. It is much more important to limit the drivers from operating outside their low distortion frequency range.

 

There is room for a vast improvement in sound quality compared to a passive crossover. Even if your passive and corrected speakers sound totally undistorted, you should achieve a significant improvement in purity and clarity when you go digital. It will sound more dynamic and detailed, yet more organic. When you start off with a passive speaker, provided you know the crossover frequencies, you should expect to achieve improvements pretty fast too.

 

Kind regards,

 

Bernt

 

From: audio...@googlegroups.com [mailto:audio...@googlegroups.com] On Behalf Of Dan Waleke
Sent: Tuesday, March 03, 2015 5:02 PM
To: audio...@googlegroups.com
Subject: [audiolense] Active Crossover Measurement Technique

 

I've done some searching and I looked through the help file and I didn't really see much specific information on this topic.

 

What is the best way to perform measurements when using Audiolense XO for active crossovers?

 

I've seen a lot of people take nearfield measurements for the active crossover part and then measurements at the main listening position to correct the room.

 

I have a 5.2 surround sound system and I am considering removing the passive crossovers from my speakers and just let Audiolense handle everything active.

 

h;te ÜðÒ’ô

[Dan Waleke]

Thank you both! Very good information.

I ordered some Solen caps and they should be here so I can start testing this weekend.

[Dan Waleke]

I was able to get 10uF Solen caps from Parts Express for the tweeters then I find out my coaxial compression drivers are actually 8Ohm/8Ohm instead of 16/16.  But I went forward with them after looking at the doc that Mitch posted and they seem to be working.

I converted my L/C/R to full active.    First impressions are wow they sound really good.   I've played with active speakers before with Minidsp products, but could never get them to sound this good.  Something always sounded off.   Not now.

I dug up some information on my 18 Sound horns.   Turns out they operate 800hz-18khz.  Not sure how JTR says horn loading down to 400hz because they won't do that.

I landed on these crossovers so far:

12" Woofers (MTM) - 80hz HPF / 600hz LPF

BMS Midrange (CD) - 600hz HPF / 6300hz LPF

BMS Tweeter (CD) - 6300hz

I am losing some headroom compared to when these were passive.   I'm not sure where though.  Also the passive crossover did a much better job producing a flatter frequency response to 20khz.   With the active setup you can see the top end rolling off before 18khz.   However with that said I still prefer how the active sound compared to the passive (can't hear much over 18khz - if anything).  It was just something I noticed.   I tried to raise the gain on the tweeter which works to raise the volume >15khz, but then I started seeing dips at the XO @ 6300hz so I lowered it back down.

So I'm not sure what I can do to optimize things at this point.   My knowledge of crossovers (active or passive) is very limited.

I've added the measurements to my Google Drive:

https://drive.google.com/open?id=0B9rv4aH0CmWcfkI1N1drR0djRDZyb0NHaFE4dk5VQXV2YzQxWnlMUjVuWUd5VzR6bmt5YTg&authuser=0

Dan

[Dan Waleke]

I kept at it and made a bit more progress.

I found "prevent trouble boost" in the correction designer.  I unchecked this and now the top end is corrected closer to the target.  Which matches more closely with the passive crossover.

I also changed the gains on the midrange (increased them) at that seems to have produced a bit better result.

So far I'm happy with the results.

[mojave]

You should hook up the CD portion of the crossover and take a measurement and do the same to the woofers to see the passive crossover slopes and frequencies. 400 Hz is only an octave below 800 Hz, so if the rolloff starts at 800 Hz it may be down 12 dB by 400 Hz depending on how steep of slopes Jeff (JTR) used. I'll see Jeff in a couple of weeks and can ask him to clarify.

To check attenuation, look at the correction filter chart. It will show exactly where the attenuation is taking place. Sometimes a little change to the target can make a big difference.

Remember that you are correcting for the listening position. If you were to use the passive crossover and correct for the listening position you might have less headroom.

[Dan Waleke]

Thank you mojave.    I was planning on doing exactly what you suggested with the passive crossovers but I was limited on time.   I imagine the passive crossover is lower than 800.  Probably in the 550-650 range if I had to guess based on how the individual drivers are measuring.   If Jeff is willing to share information about his design that would be great to know.    I don't know if those proprietary details (and the why) are meant to remain proprietary or not.   Although anyone can measure the result of the passive.

I see a couple spots where there are big dips in the frequency response and the correction goes up to 0db (420hz for example).   I need to figure out what is causing that and address the room.  

[Masis Ingilizian]

I thought ill post under here as its connected to finding an appropriate protection for my compression driver tweeter. The JBL list didn't really provide the exact info I was looking for. 

My tweeter will be 8ohm and its lowest comfortable crossover frequency point will be around 1500 or 1600hz. 

What capacitor do I need to put infront to protect the tweeter?

And where do I put it, in between the tweeter and the terminal on the plus or minus side?

[Mitch Barnett]

Hi Masis,

 

I use compression drivers in my 3 way digital XO system using Audiolense.

 

You should be able to find the appropriate protection cap with wiring diagram here: https://www.markertek.com/attachments/ATS004711.pdf

 

Best practice is to select a capacitor that is active at approximately one octave below the crossover frequency, assuring minimal acoustic interference with crossover region performance while maintaining a good degree of protection.

 

So in your case, if 8 ohm driver and XO at 1600 Hz, then the protection cap should be active an octave lower, at 800 Hz and looking up in the chart says a value of 25 uf. I use Solen fast cap like this: https://solen.ca/products/capacitors/fast-capacitors-400v-pb-series-metallized-polypropylene/pb2400/

 

While Dan’s post is 5 years ago, (would love to know how it turned out J) wrt to measurements and digital XO. Have a look in the Audiolense help file re: digital XO.

 

“When digital crossovers are handled by Audiolense, the correction is made in two steps. First each driver is time frequency corrected individually, then the sum of the individual drivers are corrected as a combined unit.

 

When True Time Domain Correction is checked, the whole speaker will be time domain corrected as one single entity. This is the only TTD option for passive speakers. The option “TTD Correction per driver” will also be visible when digital crossovers are used. Checking this option will also time domain correct each driver individually before the speaker is assembled and corrected as a whole. The experience so far is that it varies from system to system whether this option is beneficial or not.”

 

Personally, I find it very beneficial. One does not need nearfield measurements in the case of Audiolense and digital XO. Lots of fun!

 

Kind regards,

Mitch

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[Dan Waleke]

Going 3-way active with my JTR mains worked out really well.   By far the most enjoyable listening experience I've had to date.

My room needed more correction than I bet most would have and I found I needed a lot more headroom than I liked to get the correction needed.   This resulted in a less than optimal noise floor as I had to up the gains my amplifiers a bit more since most of the audio band was attenuated digitally to accommodate the correction.

Ultimately I sold everything and went a different direction.  Not because Audiolense did not work well - it worked great.   But because I was limited to essentially only using JRiver as an audio/video source and I had many other sources of content that I wanted to use.   So I had to go back to running the speakers with the passive crossover and use a traditional AVR with less than stellar room correction.

[Mitch Barnett]

Hey Dan,

 

Thanks for the update!

 

Curious to know about the other sources?

 

Kind regards,

Mitch

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[Bernt Rønningsbakk]

Hi Dan,

 

FYI, it is quite easy to route anything through the jriver convolver, internal source or hooked up to the computer.

 

I hope you made the right choice.

 

Mvh,

Bernt

 

From: audio...@googlegroups.com [mailto:audio...@googlegroups.com] On Behalf Of Dan Waleke

Sent: tirsdag 25. august 2020 15:50
To: Audiolense User Forum

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[Dan Waleke]

I did this in my main AV system.   I use it primarily for TV/Videos/(and now gaming).   Things like Netflix, Amazon Prime Video, Disney+, Apple TV+, Xbox, Nintendo Switch, anything Dolby Vision / Dolby Atmos.     None of that works through Jriver.

At the time I was mostly only TV/Movies through JRiver.   But now there is so much content through streaming providers that this solution was just no longer compatible.

If I had an audio only setup I would consider this again.

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[Bernt Rønningsbakk]

I use Netflix, Amazon Prime etc.

 

But you’re probably right about Dolby Atmos. Anything that is encrypted and protected is difficult to manage.

 

Mvh,

Bernt

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