Hi,
I would like to share my project and I have some questions (and likely will have more in the near futur).
The goal is to replace Zaph Audio ZRT that I've built more than 10 years ago with (large) bookshelf speaker.
I initially planned to just make a closed version of ZRT assisted by sub but in the end I tought if would be much more fun to build something from scratch.
My comprehension is that 3 way, if well designed, leads to better performance than 2 way (with medium price drivers at least) so that is what I choose to do. I know it can be considered more difficult for a first build but in a way I tough some characteristics (like wide directivity for ex.) would be easier to achieve this way (smaller midrange driver).
DSP FILTERING
Because I don't know how to properly design a crossover passive filter, I will use active dsp filtering, probably MiniDSP Flex 8 (or T.racks 408).
Thus, I'll be able to try and error as much as needed.
Did not buy anything yet.
DRIVERS
I already have the drivers in my possession, those are:
I hesitate to ask a refund and give up with them since I feel SB26ADC is a better driver.
What do you think? Could SB21 be a better choice?
Also, I think about the waveguide option for the SB26 (I have a 3D printer at work). Should I go this way? Without waveguide the directivity error between medium and tweeter doesn't look horrible from the simulation but I watch curves with beginner eyes.. Example:
BOX
Box will be approx. 25L. The 8'' driver will be in closed box.
SUBWOOFER
Later I'll build dual opposed subwoofer for sub 80Hz duty.
AMPLIFICATION
I will go the cheap way, probably with 3 TPA325X board (Aiyima TPA3250 maybe?). Maybe 3x Fosi Audio ZA3 if I lean towards finished product.
NEXT STEPS
Right know I'm playing with VituixCAD with manufacturer graph and simulation of drivers positions in diffraction tool.
Next steps are:
- Choose baffle design (should be something like below)
Please share any toughts about my project 🙂
Have a good day!
I would like to share my project and I have some questions (and likely will have more in the near futur).
The goal is to replace Zaph Audio ZRT that I've built more than 10 years ago with (large) bookshelf speaker.
I initially planned to just make a closed version of ZRT assisted by sub but in the end I tought if would be much more fun to build something from scratch.
My comprehension is that 3 way, if well designed, leads to better performance than 2 way (with medium price drivers at least) so that is what I choose to do. I know it can be considered more difficult for a first build but in a way I tough some characteristics (like wide directivity for ex.) would be easier to achieve this way (smaller midrange driver).
DSP FILTERING
Because I don't know how to properly design a crossover passive filter, I will use active dsp filtering, probably MiniDSP Flex 8 (or T.racks 408).
Thus, I'll be able to try and error as much as needed.
Did not buy anything yet.
DRIVERS
I already have the drivers in my possession, those are:
- SB23NRXS25-4
- SB12MNRX2-25-4
- SB26ADC
I hesitate to ask a refund and give up with them since I feel SB26ADC is a better driver.
What do you think? Could SB21 be a better choice?
Also, I think about the waveguide option for the SB26 (I have a 3D printer at work). Should I go this way? Without waveguide the directivity error between medium and tweeter doesn't look horrible from the simulation but I watch curves with beginner eyes.. Example:
BOX
Box will be approx. 25L. The 8'' driver will be in closed box.
SUBWOOFER
Later I'll build dual opposed subwoofer for sub 80Hz duty.
AMPLIFICATION
I will go the cheap way, probably with 3 TPA325X board (Aiyima TPA3250 maybe?). Maybe 3x Fosi Audio ZA3 if I lean towards finished product.
NEXT STEPS
Right know I'm playing with VituixCAD with manufacturer graph and simulation of drivers positions in diffraction tool.
Next steps are:
- Choose baffle design (should be something like below)
- Build the box (my brother is a woodworker and has a CNC).
- Buy UMIK mic and measure the drivers individually in the box
- Play again with real responses in VituixCad
- Buy DSP and finalize design
- Paint and finition
Please share any toughts about my project 🙂
Have a good day!
SB do make WG tweeters . Actually, several models. The more expensive models have a larger WG and fancy domes. The other is just a fabric dome in a smaller WG.
https://sbacoustics.com/product/sb26stwgc-4-fabric/
https://sbacoustics.com/product/satori-tw29txnwg-4-textreme/
https://sbacoustics.com/product/satori-tw29bnwg-4-beryllium/
https://sbacoustics.com/product/sb26stwgc-4-fabric/
https://sbacoustics.com/product/satori-tw29txnwg-4-textreme/
https://sbacoustics.com/product/satori-tw29bnwg-4-beryllium/
About the tweeter, as I already have the SB26ADC, it seems a better option to just build the waveguide (as there's open source design for 4 inch on somasomus).
About Hypex Fusion, I've considered it and it is not my first choice because:
About Hypex Fusion, I've considered it and it is not my first choice because:
- That's not as cheap in Europe as in US
- If I build a (or even two) passive sub later, I would need another dsp for it. With 2x8 DSP, I would already have an output and only need amplifier
- I'm afraid of what could happen if for ex. one plate is not working anymore in the future and product is discontinued?
Here are my two cents worth.
You driver choices are fine, I built something very similar with the same mid range. The four inch driver crossed to a non wave guided tweeter worked fine for me.
Build a test baffle first to verify your driver layout before building enclosures.
Don't buy a USB microphone, instead get an analog microphone and a two channel audio interface with a phantom power option so you can make accurately timed measurements to determine driver offsets.
Ok, so it is ok to test medium and woofer in open baffle configuration?
About the microphone I tought that software like rew were able to send a test signal before measurement and use it as a time reference?
About the microphone I tought that software like rew were able to send a test signal before measurement and use it as a time reference?
Yes, it can. A USB microphone is a very convenient thing when there is no necessary sound card for a classic measuring microphone.
Many people make a test baffle and then create a enclosure using rigid foam insulation. I just use heavy duty corrugated cardboard and tape to make mine. I will use any scrap wood I have laying around to make the baffle, either 1/2 inch (12mm) plywood or MDF. Then screw an appropriately sized box made from cardboard and tape to it.
Yes, REW does have a mode using a separate audio signal to create timed measurements but what I suggested is simpler to use and the cost isn't really a problem because you have not bought the USB microphone yet. I started with USB and found it to be cumbersome and bought what I have described. I have Behringer UMC204HD and a SonarWorks SoundID Reference Measurement Microphone. They cost about $200.00 here in the US for both, close to the cost of the UMIK-2. Twice the cost of the UMIK-1. @uriy-ch is correct to state that a separate sound card is not needed with a USB microphone, if the built-in sound of you computer is up the job, but I still prefer an audio interface. You will also need a microphone stand and possibly you will need to build a turn table to make complete measurements.
Look at @hifijim 's post, he describes every step of the design and build process. Here is one of his threads, check it out and any of his other threads.
Yes, REW does have a mode using a separate audio signal to create timed measurements but what I suggested is simpler to use and the cost isn't really a problem because you have not bought the USB microphone yet. I started with USB and found it to be cumbersome and bought what I have described. I have Behringer UMC204HD and a SonarWorks SoundID Reference Measurement Microphone. They cost about $200.00 here in the US for both, close to the cost of the UMIK-2. Twice the cost of the UMIK-1. @uriy-ch is correct to state that a separate sound card is not needed with a USB microphone, if the built-in sound of you computer is up the job, but I still prefer an audio interface. You will also need a microphone stand and possibly you will need to build a turn table to make complete measurements.
Look at @hifijim 's post, he describes every step of the design and build process. Here is one of his threads, check it out and any of his other threads.
Any opinion on the SB26ADC vs SB21SDCN option? Should I try to cancel SB21 command as I already have SB26ADC?
Advantages seems:
Advantages seems:
- a bit wider dispersion for SB21, closer center to center with medium
- better performances for SB26, waveguide possible
distortions are much better on 26ADC, it will cross low, 2-2.5k no problem, but the character of alu dome in the sound is present. 21SDNC - the distortions suck especially in the lower portion of its spectrum with the Neo motor structure and smaller rear chamber, but because it's a fabric dome, it's easier on ears in mid and upper treble, say mellower. Make separate baffle part for each tweeter so u can swap them and try each of them. if you can push the mids to 4-5k x-o point, then it might be possible to try the 21SDNC. Don't forget there is around 6dB baffle step loss at around 150Hz relative to upper mids (1kHz) - baffle diffraction module in Vituix can model frq resp changes due to baffle and driver placement - it's not 100% but gives good idea whats going on. And since you moved drivers way over to one side there will be asymmetric diffraction effect in upper mids and highs, which has its good and negative consequences. Definitively go with DSP, 4ohm drivers don't play easily in passive 3 way design. I think HiFi Compass has tested most of the drivers from SB u listed.
I would opt for removable baffle, in fact I always make double thickness baffle anyway. I can also try different drivers if something doesnt go my way.
You can't use open baffle for lower freqs measurements due to wave cancellation. And yes the REW sents the reference signal but its only valid for analog mic, dual channel measurement. Since the USB mic has uncontrollable time delay, its kind off useless in impulse response measurements. You could measure drivers separately, and their sum IN phase and with one driver, say mid, Out Off phase and then move the drivers acoustic centre in CAD until the loaded data corresponds with the measurements.
Ok thank you. My interpretation is that lower crossover point is better in term of horizontal and vertical directivity so maybe I should aim for 2-2K5.
Yes I did use the diffraction tool which take into account the baffle-step losses.
I need to do a precise comparaison between layout but first tests seems to be in favour to the assymetric layout (especially for the medium).
Yes, REW is able to send an acoustic timing signal if the setup of an electrical timing reference is not possible due to the use of a USB microphone. The acoustic timing signal must be sent via a separate channel to a small speaker, which must not move relative to the DUT and the microphone during the entire measurement process.
The acoustic timing signal is a sweep from 5 to 20 kHz, so an old tweeter is sufficient.
I suppose if we are talking about a three-way speaker system, then the HF speaker can be used for the dither, then the measurements of the other speakers will be aligned in time relative to the HF speaker.
But this HF speaker has to be powered via a separate channel either.
And remember: the timing signal playing speaker must not change it's position relative either the DUT AND the mic. How will this be possible for example if you want to measure your DUT under different angles?
But the delay doesn't depend on the angle ? Why would it be important to keep timing reference while measuring off-axis response?
I tought:
- as uriy-ch said:
on-axis
pc -> audio interface -> amp -> tweeter : test signal = timing ref
pc -> audio interface -> amp -> medium : test signal = delay relative to tweeter
pc -> audio interface -> amp -> woofer : test signal = delay relative to tweeter
then off-axis no need for timing reference just frequency response at each step?
The microphone should receive direct sound from the HF speaker, when turning the speaker, you can catch the reflected sound from the speaker first, and then the measurement result will be incorrect. Also, the HF speaker emits in 2pi and when turning the speaker more than 90 degrees, the microphone will not receive direct sound from the HF speaker.
I don't get how the timing reference corrects that. Do you have readings to share about a complete measurement procedure?
Also, my plan is to make the final measurements outside far from any reflective surface.
Also, my plan is to make the final measurements outside far from any reflective surface.