Are there FIR filters on the flex8? Or is there more advantages to having more dsp channels instead of fir?
I will have to build a pair of diffusers to place behind the speakers aswell before I try experimenting with rear tweeter levels.
So are you running the speakers 3 way including back tweeter or 3+1 with the back tweeter as a separate channel?
I haven't read much about the flex8 but are there FIR filtering?
That is fantastic! Thank you for telling that story.
Yes at apartment SPLs these will go down to 20Hz. I would love to hear more details about your tube amp.
The MiniDSP 2x4HD has an FIR bank on each of the 4 output channels. I created a separate FIR filter for each of the woofers and tweeters.
The MiniDSP Flex8 has FIR on each of the 2 input channels, so it is more restricted. In the Flex8 version, I aligned the standard IIR filters so that the drivers are in correct time alignment. Then I added the FIR DSP as a final step. In the Eclipse FIR tool it looks like this:
This is one channel, the other channel has a slightly different amplitude curve because it is customized to each individual tweeter.
I have attached the Flex8 FIR correction file that generates the curve you see above and it should work on the Flex8. The Flex8 is better - the noise is at least 10dB lower, and the sound is clearer and more refined.
The 2x4HD configuration files are already included in the other documentation I've already posted online.
I don't remember for sure, but I'm pretty sure the 2x4HD FIR files only correct phase for the woofers (and not magnitude at all), and for the tweeters they correct both phase and 1/48th octave EQ for the top 1-2 octaves for the tweeters. Without FIR you are at minimum going to need to play with both phase and time delay of the channels. Having correct alignment of everything will make a pretty big difference in the sound.
As for triamp instead of biamp, I expect that should sound better. The top of this thread shows the drive signals reaching the 15OB350s and the 15CXN88s through the passive crossover, which is very interesting:
https://www.diyaudio.com/community/...over-vs-parallel-for-subs-open-baffle.404680/
As you can see, even though the crossover is "only 6dB" it still protects the 15CXN88 from low frequencies very effectively. In the FIR settings above you see that I added a phase rotation to compensate for the phase shift of this filter.
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The woofer amp drives: [2x 15OB350 + 1x 15CXN88 woofer with passive LC crossover.]
The tweeter amp drives [15CXN88 tweeter + 44CD-T tweeter with passive RLC notch filter]
I have also added Zobel networks which, if you are using tubes, will help by flattening the impedance.
I think diffusers on the rear wall are a GREAT idea.
I have also added the zovel network. I would love to use the flex8 but I am using the speakers in my cinema aswell so analog inputs is necessary.
My tube amp is a line magnetic lm845ia with linlai elite power tubes. Probably the best sounding amplifier I have used if you don't need a lot of power.
My tube amp is a line magnetic lm845ia with linlai elite power tubes. Probably the best sounding amplifier I have used if you don't need a lot of power.
Very sophisticated filter. I was testing a little bit In vituixCAD about going with only one of the 15ob350 with the 15cxn and running the bottom woofer active to be able to put more power to it. But a new coil is almost as expensive as two new woofers and run them as pure subs.
I checked.
The 2021 Bitches Brew 2x4HD FIR files do a little amplitude correction and a lot of phase correction for the woofers, like this:
The Bitches Brew tweeter 2x4HD FIR files do mostly phase correction, and amplitude correction only in the top 3 octaves as you see here:
If you are not using any of the FIR filters then the design can still work fairly well, but you will have to 1) re-align the delay between the bass and treble sections, and 2) You may have to switch the tweeter polarity as well, I'm not sure; and 3) There will probably be some EQ you need to do.
It won't be linear phase without FIR.
I believe the system will image better and have more transparency with the FIR filters in place. I personally believe that linear phase and excellent impulse + step response is very important, it affects imaging, clarity and definition. Especially for percussion. This is the step response I measured in April 2023:
These curves were taken using the April 2023 configuration file attached, on the 2x4HD. The FIR files are embedded in this configuration file.
Note, as I've posted multiple configuration files at different times you need to pay close attention. The file here for example has the gain turned up on the tweeters (channels 3 & 4) because the woofer and tweeter amps had different gain settings. You should measure everything and make sure it's working in a way that makes sense to you.
The 2021 Bitches Brew 2x4HD FIR files do a little amplitude correction and a lot of phase correction for the woofers, like this:
The Bitches Brew tweeter 2x4HD FIR files do mostly phase correction, and amplitude correction only in the top 3 octaves as you see here:
If you are not using any of the FIR filters then the design can still work fairly well, but you will have to 1) re-align the delay between the bass and treble sections, and 2) You may have to switch the tweeter polarity as well, I'm not sure; and 3) There will probably be some EQ you need to do.
It won't be linear phase without FIR.
I believe the system will image better and have more transparency with the FIR filters in place. I personally believe that linear phase and excellent impulse + step response is very important, it affects imaging, clarity and definition. Especially for percussion. This is the step response I measured in April 2023:
These curves were taken using the April 2023 configuration file attached, on the 2x4HD. The FIR files are embedded in this configuration file.
Note, as I've posted multiple configuration files at different times you need to pay close attention. The file here for example has the gain turned up on the tweeters (channels 3 & 4) because the woofer and tweeter amps had different gain settings. You should measure everything and make sure it's working in a way that makes sense to you.
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This is so amazing news about a "hobby project" that turn out so successfully - just sitting here finally with money on my account to order parts - Though I must say the build quality looks so pristine and professionally that it sets very high standard. Also the design is very cool and totally live up to the phrase "Clean nordic design"
Thank you for sharing...
Hello Balthazarp and also Perry,
First I will thank you Perry because of your generous sharing of ideas and thought about speakers- mainly these high end quality build, like The Bitches Brew Live Edge speakers. The fact that Balthazarp can get these perfomance out off his build - that in quality exceeds a 300K usd speaker is so much to your credit, Perry. Perry you have said this yourself before - and I actully believed you by my intuition. But now it's confirmed.
Next thing is that I have ordered the following:
4 X SB Bianco 150B350 - Woofers
2 X SB Acoustic H250 - Horn plus 44cd cCompression driver
2 X B&C 15CXN88 - Coaxial Tweeters (is waiting on purchase, bc its out of stock many places - and expensive too..)
Then I ordered this internal cable
8 terminal
10m 1,5 cable plus 10m 2,5 cable.
Now I wish very humble from one off you guys advise and please a list off the rest off the electronic parts I need1??
Bear over with me as I am by no means an electronic ingeneuir or alike. I am only a skilled craftsman/plummer/blacksmith that can put things together...
My plan is to make a tentor steel forced concrete build... Proberly it will to hew - but I have some tricks in the sleeve - LOL
The list off electronics components may please be the simple and most easy way - even just kind of simple wired model without these MiniDSP 2x4 HD digital signal processor - please forgive me if it sounds like a stupid idea. Im just a little bit scared off these download of ram files etc...
I have a old Mission Cyrus 3i Amp with 50w per channel - don't know really what that means - surely I will properly go shopping for new and better...
Thanks in helping.
Congratulations on starting your build!!!
You need:
2 x 6mH inductors, I recommend the Goertz copper coil air core inductors:
https://www.madisoundspeakerstore.com/goertz-14-awg/goertz-cf6.0-14-awg-copper-foil-inductor/
Any kind is fine as long as it's air core and DC resistance is less than 0.75 ohm. I do not recommend iron core - not in a speaker design that's this uncompromising.
2 x 360uF capacitors, I recommend putting film and electrolytic capacitors in parallel to add up to 360uF. At least 100uF of the 360 should be film.
2 x 80uF film capacitors
2 x 2.7uF film capacitors
2 x 0.5mH inductors, any air core units are fine
2 x 5 ohm resistors 10 watt
2 x 6 ohm resistors 25 watt
~
Optional components for Zobel (circled in green):
2 x 7mH iron core inductors
2 x 10 ohm 25 watt resistors
2 x 7 ohm 10 watt resistors
2 x 22uF electrolytic capacitors
These flatten the impedance, which makes amplifiers behave better, especially tubes.
~
MiniDSP 2x4HD OR MiniDSP Flex Eight
The schematic is in my previous posts above.
I want to encourage you that using a DSP is a LOT easier than you think. All you need to do is get the DSP unit (I recommend MiniDSP Flex Eight), load the DSP software into your computer, unzip my DSP files and load them into the software. Then hook a USB cable from your computer to the DSP and load in the configuration file.
That's it. The entire system will be working in just a few minutes.
Then play with it and see what it can do. It will only take an hour for you to become familiar with the DSP software and play with EQ settings. It's WAAAAAAAY easier than fumbling around with passive crossovers. Once you've tried it, you'll never go back. The only reason I build passive crossovers now is because I like the challenge.
Seriously, most of the hi fi / stereophile world is afraid of technology when they shouldn't be. Most of the high-end industry is working with one hand tied behind their back because either manufacturers won't sell DSP systems, or else the customers won't buy them. So they just live with inferior performance. Gary Galo in Speaker Builder magazine said 35 years ago: "compared to active crossovers, even the best passive crossovers are turkeys." He's right. It's even more true today especially since the active crossover is all digital and has virtually zero distortion and you can fix any problem very easily.
To put a finer point on it, some of the old analog active crossovers did have one serious problem: They added noise and distortion, much like you get if you inserted a 2nd preamp. It's just more gain stages, which degraded the signal sometimes more than the passive crossovers, unless you had really high quality op-amps.
But today's digital crossovers are vastly superior because the music comes from streaming or CD so is all digital to begin with (unless you only listen to LP's) and it never gets converted to analog until the output of the DSP just before the amp. All of the EQ occurs digitally and the signal quality is incredibly good. You can do all kinds of things with a digital crossover that are impossible with passive. (Like Jakob boosting the bass +24dB at 20Hz!!!!) That's why DSP crossovers really are the way to go.
This is also why the Bitches Brews can compete favorably with a highly regarded $300,000 commercial design. DSP is why even though they're dipoles, they can still reach down to 20Hz.
In order to not use a DSP, I would have to design a passive crossover for the Bitches Brew. It would be complex; the additional parts would be more expensive than a MiniDSP 2x4HD, and not nearly as good. They would only go down to about 35Hz.
I could simulate the crossover on VituixCad, and that would work OK, but I'm still not willing to physically build and test it, so you would be building an un-tested design.
It would be like buying a brand new Ferrari without tires, then going to a local used tire store and grabbing any old tire that would fit and sticking them on. Will it drive like a Ferrari? Absolutely not.
The Bitches Brew design as published needs DSP and needs to be biamped. If you want a good budget 4 channel amp, use the Adcom GFA-2535. You can buy them for $200-$300 plus shipping and they sound great. Or you can buy a 2nd amp of any brand you like.
Again, don't be intimidated by DSP. If you find it confusing, a local friend can come by and help you set it up, or someone on this forum can zoom with you and show you how. You will be VERY happy you did.
You need:
2 x 6mH inductors, I recommend the Goertz copper coil air core inductors:
https://www.madisoundspeakerstore.com/goertz-14-awg/goertz-cf6.0-14-awg-copper-foil-inductor/
Any kind is fine as long as it's air core and DC resistance is less than 0.75 ohm. I do not recommend iron core - not in a speaker design that's this uncompromising.
2 x 360uF capacitors, I recommend putting film and electrolytic capacitors in parallel to add up to 360uF. At least 100uF of the 360 should be film.
2 x 80uF film capacitors
2 x 2.7uF film capacitors
2 x 0.5mH inductors, any air core units are fine
2 x 5 ohm resistors 10 watt
2 x 6 ohm resistors 25 watt
~
Optional components for Zobel (circled in green):
2 x 7mH iron core inductors
2 x 10 ohm 25 watt resistors
2 x 7 ohm 10 watt resistors
2 x 22uF electrolytic capacitors
These flatten the impedance, which makes amplifiers behave better, especially tubes.
~
MiniDSP 2x4HD OR MiniDSP Flex Eight
The schematic is in my previous posts above.
I want to encourage you that using a DSP is a LOT easier than you think. All you need to do is get the DSP unit (I recommend MiniDSP Flex Eight), load the DSP software into your computer, unzip my DSP files and load them into the software. Then hook a USB cable from your computer to the DSP and load in the configuration file.
That's it. The entire system will be working in just a few minutes.
Then play with it and see what it can do. It will only take an hour for you to become familiar with the DSP software and play with EQ settings. It's WAAAAAAAY easier than fumbling around with passive crossovers. Once you've tried it, you'll never go back. The only reason I build passive crossovers now is because I like the challenge.
Seriously, most of the hi fi / stereophile world is afraid of technology when they shouldn't be. Most of the high-end industry is working with one hand tied behind their back because either manufacturers won't sell DSP systems, or else the customers won't buy them. So they just live with inferior performance. Gary Galo in Speaker Builder magazine said 35 years ago: "compared to active crossovers, even the best passive crossovers are turkeys." He's right. It's even more true today especially since the active crossover is all digital and has virtually zero distortion and you can fix any problem very easily.
To put a finer point on it, some of the old analog active crossovers did have one serious problem: They added noise and distortion, much like you get if you inserted a 2nd preamp. It's just more gain stages, which degraded the signal sometimes more than the passive crossovers, unless you had really high quality op-amps.
But today's digital crossovers are vastly superior because the music comes from streaming or CD so is all digital to begin with (unless you only listen to LP's) and it never gets converted to analog until the output of the DSP just before the amp. All of the EQ occurs digitally and the signal quality is incredibly good. You can do all kinds of things with a digital crossover that are impossible with passive. (Like Jakob boosting the bass +24dB at 20Hz!!!!) That's why DSP crossovers really are the way to go.
This is also why the Bitches Brews can compete favorably with a highly regarded $300,000 commercial design. DSP is why even though they're dipoles, they can still reach down to 20Hz.
In order to not use a DSP, I would have to design a passive crossover for the Bitches Brew. It would be complex; the additional parts would be more expensive than a MiniDSP 2x4HD, and not nearly as good. They would only go down to about 35Hz.
I could simulate the crossover on VituixCad, and that would work OK, but I'm still not willing to physically build and test it, so you would be building an un-tested design.
It would be like buying a brand new Ferrari without tires, then going to a local used tire store and grabbing any old tire that would fit and sticking them on. Will it drive like a Ferrari? Absolutely not.
The Bitches Brew design as published needs DSP and needs to be biamped. If you want a good budget 4 channel amp, use the Adcom GFA-2535. You can buy them for $200-$300 plus shipping and they sound great. Or you can buy a 2nd amp of any brand you like.
Again, don't be intimidated by DSP. If you find it confusing, a local friend can come by and help you set it up, or someone on this forum can zoom with you and show you how. You will be VERY happy you did.
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Dear Perry ,
This thoroughly answer in the new age of internet that proff how wonderfull world also can be.
Your kind reply is much appreciated..
I will follow your advice and do as you suggest include the use of DSP.
Maybee before Cristmass there will be a result.
Also the digital Adcom amp sound like a good choise….!!
Thanks once more!
Regards Peter Thomsen
This thoroughly answer in the new age of internet that proff how wonderfull world also can be.
Your kind reply is much appreciated..
I will follow your advice and do as you suggest include the use of DSP.
Maybee before Cristmass there will be a result.
Also the digital Adcom amp sound like a good choise….!!
Thanks once more!
Regards Peter Thomsen
Hi!
I was meaning to respond a lot sooner to your post but I have been having fever all week and I'm still not back, but today I am at least standing up and walking around a little bit.
I was wondering a little why you are using the peq as lowpass/highpass instead of the traditional crossover section in the dsp software? Is it to have a little more control over the slopes or is there any other reason? I just think the woofer section looks wierd with response rising again in the woofer section.
I was also thinking about adding clear acrylic to cover the sides of the speaker to make it more similar to the original bitches brew, but still keep the open design. But the bass extension is still excellent in my application and listening levels. I use the Fletcher Munson compensation in my RME ADI-2 pro (digital out to dsp) to add a bit of extra db bass boost in lower volumes and to avoid clipping in my weak amp if I want to play a bit louder.
I had some other questions but my brain is not fully working, and I dont know if what I'm asking makes any sense.. I dont know how much we should discuss in this thread. Maybe better to take questions in direct messages.
Also good luck with your build @Thomsen_build! If you want to save some money on amplification after a rather expensive speaker build i ran my speakers with cheap Fosi audio amp with good result. Plenty of power and very quiet. For technical questions it's probably better to ask Perry, but I will try to help with everything I can!
Regards Jakob
Attachments
Jakob @Balthazarp Yes there is a very specific reason why I use shelf filters instead of standard filters. I explain some of that reasoning here:
https://www.diyaudio.com/community/...-pass-xovers-with-notch-shelf-filters.404415/
A shelf filter introduces HALF as much phase shift as a low pass or high pass filter.
So you're crossing over the 15CXN88 tweeter and we're looking at the range from 2KHz down to 500Hz where the level drops 20dB. A standard 12dB/octave filter would result in 270-360 degrees of ACOUSTIC phase shift. 18 or 24 would introduce even more. But my shelf filters will level out below 500Hz and introduce only 135-180 degrees phase shift.
I can't remember, I think I may have a 6dB/octave digital high pass filter on the 15CXN88 tweeter. For sure I have an 80uF capacitor between it and the amp. That adds 6dB/octave more protection. So the 20dB of shelf filtering is enough to do the job.
This makes the time alignment of everything much easier. Then at the end with FIR filters I only have to apply 360 degrees of very mild, well-behaved all pass filtering to make the entire system linear phase. With great impulse and step response.
So yes it's very unconventional but I think it's one of the reasons the system is so seamless and well integrated. It's impossible to identify the transition at the 1100Hz xover frequency and the blend at 110Hz is also very smooth and blends well.
I don't know of any other speaker in the world that will fit in a living room which has 120 dynamic range, linear phase, constant directivity and wide bandwidth all at the same time.
https://www.diyaudio.com/community/...-pass-xovers-with-notch-shelf-filters.404415/
A shelf filter introduces HALF as much phase shift as a low pass or high pass filter.
So you're crossing over the 15CXN88 tweeter and we're looking at the range from 2KHz down to 500Hz where the level drops 20dB. A standard 12dB/octave filter would result in 270-360 degrees of ACOUSTIC phase shift. 18 or 24 would introduce even more. But my shelf filters will level out below 500Hz and introduce only 135-180 degrees phase shift.
I can't remember, I think I may have a 6dB/octave digital high pass filter on the 15CXN88 tweeter. For sure I have an 80uF capacitor between it and the amp. That adds 6dB/octave more protection. So the 20dB of shelf filtering is enough to do the job.
This makes the time alignment of everything much easier. Then at the end with FIR filters I only have to apply 360 degrees of very mild, well-behaved all pass filtering to make the entire system linear phase. With great impulse and step response.
So yes it's very unconventional but I think it's one of the reasons the system is so seamless and well integrated. It's impossible to identify the transition at the 1100Hz xover frequency and the blend at 110Hz is also very smooth and blends well.
I don't know of any other speaker in the world that will fit in a living room which has 120 dynamic range, linear phase, constant directivity and wide bandwidth all at the same time.
@perrymarshall
Thank you! Yes, that makes sense. It just made it a little bit harder to adjust the EQ curve without affecting the shelf at the crossover point. But compared to a passive system I should not complain! Just started to take some in room measurement now.
Thank you! Yes, that makes sense. It just made it a little bit harder to adjust the EQ curve without affecting the shelf at the crossover point. But compared to a passive system I should not complain! Just started to take some in room measurement now.
All, I posted a tech note on the Bitches Brew "little brother," the Live Edge Dipoles. These took 1st Place at the Parts Express Speaker Design Competition August 4-5 2023 in Ohio:
https://www.diyaudio.com/community/...ker-design-competition-updated-design.405104/
This post contains many tech details about design choices, combining passive filters with DSP, and has configuration files for MiniDSP 2x4HD as well as Flex Eight.
https://www.diyaudio.com/community/...ker-design-competition-updated-design.405104/
This post contains many tech details about design choices, combining passive filters with DSP, and has configuration files for MiniDSP 2x4HD as well as Flex Eight.
@perrymarshall: Is the Bitches Brew the best of the speakers you have designed and made do you think?
Yes definitely. In particular their top to bottom coherency and being completely unruffled by anything you throw at them. Most people haven't heard sound like that before.
2 1/2 years later I'd be hard pressed to significantly improve them.
The Live Edge Dipoles I just posted about which won the 2023 Speaker Design Competition sound quite similar in a much smaller, lighter and less expensive package.
2 1/2 years later I'd be hard pressed to significantly improve them.
The Live Edge Dipoles I just posted about which won the 2023 Speaker Design Competition sound quite similar in a much smaller, lighter and less expensive package.
You are right. The Radian coax is slightly better. The Beryllium is better than the Titanium.
The B&C titanium has a very slightly abrasive edge UNLESS your amp has a super smooth texture. Then it goes away. The 1/48th octave DSP correction custom fit to both left and right helps too.
That said, the Bitches Brews still sound better overall. They have a buttery smooth integration that I believe is from 3 15s that all have pressed cones, all same size, same radiation pattern and a very similar “signature sound” and a totally seamless crossover.
The B&C titanium has a very slightly abrasive edge UNLESS your amp has a super smooth texture. Then it goes away. The 1/48th octave DSP correction custom fit to both left and right helps too.
That said, the Bitches Brews still sound better overall. They have a buttery smooth integration that I believe is from 3 15s that all have pressed cones, all same size, same radiation pattern and a very similar “signature sound” and a totally seamless crossover.
