AudioCircle
Industry Circles => Hollis Audio Labs => Topic started by: HAL on 19 Jul 2016, 04:55 pm
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Since Linkwitz Labs has issued a challenge for a DSP crossover for the LX521 speakers and the dspMusik meets the criteria, this is the place to discuss interest.
His specifications say it needs a 3-way speaker crossover and a passive 1-pole between the two mids at 1KHz. It can be done as a 3-way or 4-way with the dspMusik for a total DSP solution, as long as the user has eight amplifier channels. The crossover electrical spec is a 4th Order Linkwitz-Reilly HP and LP at 120Hz and 7KHz which is also easily done and a 1 pole HP at 1KHz for the two mids.
I have a demo HAL MS-3 and dspMusik system that can be tried for this application if there is interest. It will come with the block diagram for the LX521 crossover for the user to load and then can use the MS-3 to playback music files from either USB or Ethernet accessible drives.
If there is no interest, will not bother with the crossover design, so this is where to post interest.
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Ok, 53 views and no response.
Looks like no one is interested in a LX521 dspMusik digital crossover. Hope whatever they come up with sounds this good.
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You realize "the challenge" is like three years old, right?
Perhaps you should accept it and validate that your DSP is up to the challenge. All you need to do is buy the LX521 plans, build the speaker and program your DSP to match the official transfer curves supplied with your plans.
There are currently several viable DSP's in use that have been "approved" for use with the LX521 and are supported by the Linkwitz Lab community.
p.s. The current iteration of the LX521 is LX521.4 and it requires an 8-channel DSP (or 8-channels of DSP processing power using daisy-chained units).
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I have no doubt it is old.
I can replicate the response curves need without the speakers as I can use the specs to do the design. He has put it all on his website.
The dspMusik has 8 channels of HiRez DAC outputs, so easily done. Probably about 30 minutes of design time to replicate it and then measure it with CLIO.
I have no intention of building the speakers. That is why I asked if someone were interested in a trial with their system.
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I can evaluate it if you like.
I've already used four different (ASP and DSP) signal processor solutions with the LX521 and am intimately familiar with the requirements.
If your unit works well I will recommend it to the community.
Dave.
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Dave,
Since you are interested, I will build the software.
Where are you located? I have to send a MS-3 Music Server with the dspMusik to use to program the dspMusik.
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The LX521 crossover block diagram for the LX521 is complete. This is using the high performance Linkwitz-Riley crossover block setup for a 3 way, 4th order L-R crossover. Have added the single pole filter after the lower midrange for the upper midrange.
This is based off the electrical crossover parameters Linkwitz Labs has on the website for the LX521's.
Will be testing it with CLIO shortly to make sure I have the 3 way L-R and single pole crossover working as expected.
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Here is the best info I can find to the LX521 crossover design besides the specification description on the LL website. I have no access to the crossover website, since I am not an owner. It shows the different gains needed to get the correct acoustic summation for flat response.
If this is what it really implemented from the electrical network side, it is possible the specs that are being quoted are the acoustic crossover points. If so will have to find a way to verify if these are the most recent design.
Also the 1KHz spec is for a single pole filter, and the graph shows a L-R 2 pole.
The design I have is based on the specs on the website, but this shows the difference. Will see if I can find the correct version for the latest design.
Removed the image as for some reason Google is finding proprietary info.
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There are two current versions of the LX521 system. Both versions are four-way, but the earlier version utilized a passive crossover between the two midrange drivers.
The later version is fully active for all four branches and also incorporates a different crossover/equalization/delay scheme.
You can start to see the challenge of the "Challenge" now eh?
As "lowtech" noted, you're way late to the party on this. But if you feel your solution brings something to the table that others don't, then the community/me would certainly be interested.
Dave.
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Not really that hard with Audio Weaver and the dspMusik. The challenge is finding the data needed, not in implementing it.
Last piece is the biquad coefficients for the woofer EQ. Then it should be ready for CLIO measurements.
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This is not a minimum-phase implementation. You are aware of that, yes?
Dave.
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The crossover filter system will be the digital equivalent of what LL has posted.
The DAC's are minimum phase filters for reconstruction.
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What SL has posted on his public pages does not fully characterize the design.
And I'm not talking about the DAC's. :)
It would probably be better if you just let me do the specific programming and you could just provide the general support regards the hardware implementation.
Dave.
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Davey,
The version one of the Audio Weaver crossover block diagram is done as far as I can go. The only thing I did not add so far is the peak filter at 230Hz. Easy enough to do, but not sure after trying that here with very poor results, why you would do it.
I will send the block diagram. If you do not feel it is worth continuing, I will just bag the project. If you do, will ship the MS-3 and dspMusik demo system for trials. Everything uses the latest high performance filter designs from Danville for Audio Weaver.
PM me your email address to send the file.
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Do you have remote volume capability on these units??
Dave.
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If you are running Audio Weaver for the dspMusik, the PC can do remote volume on any unit. I use a wireless keyboard on the MS-3 to do the volume with the DAC 8 channel control.
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I want to voice support for this. Im planning to build an LXmini first for a smaller room and then if that goes well, a LX521 for a larger room. I imagine if you get this working for the LX521, then it should work for the mini?
Thanks for working on this.
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Would have to get the data needed for the LX-Mini as well to do the digital crossover.
All depends on how things go with the conversation about this version.
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Yes, it will need a different filter set, but it's great to see these two technologies coming together.
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How is volume controlled if the companion MS-3 PC is not connected? The dspMusik (standalone) has no volume control capability??
Dave.
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I want to voice support for this. Im planning to build an LXmini first for a smaller room and then if that goes well, a LX521 for a larger room. I imagine if you get this working for the LX521, then it should work for the mini?
Thanks for working on this.
John,
The LXmini is designed as an extreme value system.
You can purchase a complete LXmini kit (sans miniDSP unit) from Madisound for $440.00. The MS-3/dspMusik setup will set you back $2800.
You can purchase a complete LX521 kit (sans miniDSP unit) from Madisound for $1740.00. The MS-3/dspMusik setup will set you back $2800.
I'm having trouble justifying the cost in an LX521 system, let alone an LXmini system. :)
Dave.
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How is volume controlled if the companion MS-3 PC is not connected? The dspMusik (standalone) has no volume control capability??
Dave.
The dspMusik RevD will have a front panel volume control and display for all 8 DAC channels. It is not remote controlled, but it will also do mute and input selection once that version is finished.
You need the MS-3 for remote control of parameters and volume. There is no plan to add IR or Bluetooth to the uC running in the dspMusik.
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I've been chatting with Al Clark a bit. Apparently they are cogitating on dspMusik remote control possibilities via Bluetooth smartphone and/or similar schemes.
A remote control feature is mandatory IMO. Having to put my beer down and walk across the listening room all the time to fine-adjust the volume is unacceptable.
If the dspMusik unit can't implement this standalone, it forces the user to implement it elsewhere. As you know, from a gain structure standpoint, the placing and scheme of this system volume control is important. Inside the dspMusik unit is most likely the optimum location.
A wireless keyboard scheme wouldn't bother me since I don't have a problem with having an operating PC tethered to my system all the time.....but some folks would.
This seems an oversight on the basic dspMusik design....in my opinion.
Dave.
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Dave,
Have been working with Al for about 6 years to get it this far. Other user inputs I get are fed to him as well.
I asked for the hardware DAC volume control capability awhile back. Phase one comes in RevD. The uC they are using is good for a lot of things, so now a possibility, like Bluetooth or IR as future upgrades. Now, it is convincing Al what capabilities to add.
Originally, this was an internal only product for speaker systems not DIY. Program it once and done forever, no controls and no USB for audio file replay. I asked for the external chassis version with those capabilities and got it 2 years ago that started with RevC.
I think of this product as a DEQX HDP-5 with more channel capability and less than 1/3 the price. Really like the more flexible PC interface, and that is why I build these for folks for their specific speaker. I support the ones I sell and preconfigure the MS-3 and dspMusik system to make sure the user is up and running with their system quickly. That is the part that just buying a dspMusik directly does not provide.
For folks that know DSP, it is pretty easy. For folks that do not, it can be very difficult. Then add on top knowing how to do the electrical and acoustic speaker measurements for designs that require a custom version.
Will be interesting to hear what happens with the RevD system when it is finished.
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Hi Rich, are there any changes planned for A/D converter used in the dspMusik, or will you be sticking with the current processor?
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The A/D's and D/A's in the RevD system are new, the DSP processor is the same. Both are minimum phase filtered devices selected for the design.
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Sounds like the hot ticket for vinyl replay with full room correction and xover capability.
Scotty
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The new capability will be having the A/D output via the USB interface. This way the unit can do measurements with recording programs like Audacity or Room EQ Wizard.
I plan to use it with my recording rig, besides audio replay. Possible to now archive vinyl to digital as well at 24bit/192KHz with the recording software.
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John,
The LXmini is designed as an extreme value system.
You can purchase a complete LXmini kit (sans miniDSP unit) from Madisound for $440.00. The MS-3/dspMusik setup will set you back $2800.
You can purchase a complete LX521 kit (sans miniDSP unit) from Madisound for $1740.00. The MS-3/dspMusik setup will set you back $2800.
I'm having trouble justifying the cost in an LX521 system, let alone an LXmini system. :)
Dave.
Thanks. I guess I was looking just at the dspMusik alone.
On the topic of volume adjustment, I thought you would want volume adjustment after the DAC, so that the digital processing and conversion to analog is using a full dynamic range and all the bits, instead of in the source.
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The DAC's have built in 32bit digital attenuators. They are controlled by the DSP software for all 8 channels.
Analog volume controls would not track well enough to work with 8 channels of DAC's to keep the crossover outputs at the same level for the drivers in a multi-way system.
I sell the dspMusik as a system with the MS-3 Music Server. Comes preloaded with all the software to run the dspMusik and playback HiRez music.
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There are quite a few (DIY and commercial) digitally-controlled analog volume controls that will easily achieve the necessary tracking. But, it's much easier to implement within the DSP/DAC structure so most units employ that scheme.
The newer Revision-D dspMusik mentioned by Al Clark seems to address some missing features, but it's still quite high in price compared to many alternatives.
Dave.
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Dave,
Then sounds like I will just not worry about doing dspMusik crossovers for the LX521 or LX-Mini, since they are low cost speaker kits. The prices is what it is for me to sell them and support them.
Good luck with the other digital products out there.
Off to another digital crossover project.
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Well, I'm not abandoning the effort. I'm always looking for alternatives that represent excellent value in these applications.
After a couple of minor bugs, I now have the Audio Weaver installation working fine and have added the required blocks to the basic configuration you supplied. That yielded something that (now) looks pretty close to the proper transfer functions for the LX521.
I will work directly with Al Clark should I decide to acquire a dspMusik box and put the setup into actual operation.
Cheers/Thanks,
Dave.
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Dave,
No problem. I already told Al you should deal directly with him from now on.
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Thanks for investigating this, Davey.
I had a feeling HAL would not be able to put together a suitable offering without having access to the actual transfer curves for the speakers since it's considered protected IP.
Looking forward to reading about Davey's experimentation with the unit, should he decide to acquire one.
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Dave has my block diagram I started for Audio Weaver for the LX521 crossover design.
Here is where I stopped, as there is no way to complete it to answer the challenge without the data LL does not post.
Good luck with the design.
(http://www.audiocircle.com/image.php?id=148133)
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Dave has my block diagram I started for Audio Weaver for the LX521 crossover design.
Here is where I stopped, as there is no way to complete it to answer the challenge without the data LL does not post.
Good luck with the design.
I'm sure if Davey feels this crossover platform exceeds the performance of what's already available (despite it costing more than it's worth based on your MSRP) he'll offer the programming to SL and it'll be added to the list of LX521.4 "supported DSP's". Having users deal directly with Danville Signal (https://www.danvillesignal.com/high-performance-audio/dspmusik-2-8-multichannel-dac) seems to be the way to go considering the LX521.4 is a not-for-profit design.
P.s. Same image as you posted earlier but "Removed the image as for some reason Google is finding proprietary info. (http://www.audiocircle.com/index.php?topic=144418.msg1545914#msg1545914)". :?
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No lowtech,
That is an actual set of measurements from the dspMusik using CLIO with my interpretation of the open data, not SL's post that is on the web for anyone to see. So my post stands as my work on the challenge. No need to go further.
Your interpretation of the cost is very interesting. You have not invested any time and effort to learn or get the product improvements to market, program it and support it for a customers and think my markup is to high and then have no issue with products like DEQX and their price.
Good luck whatever Davey does.
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No need to go further.
Agreed. Your final target is greater than 50% off.
Your interpretation of the cost is very interesting. You have not invested any time and effort to learn or get the product improvements to market, program it and support it for a customers and think my markup is to high and then have no issue with products like DEQX and their price.
Having had some past experience with DEQX products, I think you are mistaken about your assertion. Additionally, the dspMusik product and the DEQX do have some functionality overlap, but are fundamentally different. The DEQX is designed to eliminate the middleman (plug-and-play/no user or 3rd party programming required).
Good luck whatever Davey does.
We can agree on that. :)
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The fact I got to 50% of the digital crossover design with open data is a good sign to me. The system will do well with implementing this design.