Hi All 🙂
Planning by first build. And had a silly question about dispersion. I did download the vitiuxcad program, but got completely lost. Should have probably tried this 30 years earlier while I still had the chops to learn a new skill. So Iam trying to clone a build with less than half baked knowledge.
I got all the drivers to build a clone of the Janzen-Accu mid bass cabinet as originally built by Mr.Troels. This has the Accuton C30-6-358 tweeter suspended below the Accuton C173-6-191-E mid bass driver on an isolated and inter changeable tweeter baffle.
The plan is to build two of these cabs, and join them together with one cabinet inverted to end up with a MTM version. I can increase the spacing between the two cabs, with an additional wooden board in between if required. Iam just posting a rough sketch below. And please bear with my poor drawing skills 🙄
I have the Accuton C30-6-358 tweeter originally used in the build. And subsequently, I got my hands on some Accuton C51-6-282 2" upper mid domes. And I also got a Raal 70-20 XR AM ribbon tweeter. Now Iam considering replacing the original Accuton C30 tweeter, with C51-Ribbon-C51 arrangement. So this will end up being a mid bass - 2" mid dome - Ribbon - 2" mid dome - mid bass configuration. The idea is to end up with a virtual point source mid range cabinet that goes from 80 hz to 20khz.
The mid bass will be crossed over to the mid dome between 800 to 1000 hz. And mid dome to ribbon between 3800 to 5000 hz. The above frequencies were chosen to keep all drivers below their beaming frequency. I just took the stated cone diameter in their specs, and calculated their beaming frequencies based on the formula 343/cone dia. I hope this method is "ok" 😛
Used this way, do I still have to simulate the horizontal dispersion on VitiuxCad before going ahead with the build. I intend to keep all cabinet dimensions original as designed by Mr.Troels. And only replace the original tweeter. And the new tweeter baffle though higher to accommodate the additional drivers, will still have the exact same horizontal sloping dimensions to the sides. And considering that Iam lowering the original crossover frequency from about 2200 hz to 1000 hz, the CTC driver spacing should be fine I believe.
So my question is, used this way, do I still have to carry out any simulations for horizontal dispersion as all the drivers will be used below their beaming frequencies. And I will be going active with a Sublime audio K235 active crossover where I can adjust the crossover frequencies and levels only, as Iam new to the DIY world, and would'nt be able to simulate a crossover if my life depended on it. So considering all the above, should I undertake this build, or is it doomed to fail already. 😱
Thanks in advance for any and all advise.
Additional- Mr.Troels originally designed these cabs with the port tuned to 40hz. Though I would like to keep the bass below 100 or 120hz to keep the cone excursion and distortion lower. And will build a bass cab below to reach 100 hz. I got a scanspeak 26W / 8867 for this. But cannot find any builds or schematics using this particular driver. Any guidance about using this driver in a build will be very helpful. Thanks again 🙂
Planning by first build. And had a silly question about dispersion. I did download the vitiuxcad program, but got completely lost. Should have probably tried this 30 years earlier while I still had the chops to learn a new skill. So Iam trying to clone a build with less than half baked knowledge.
I got all the drivers to build a clone of the Janzen-Accu mid bass cabinet as originally built by Mr.Troels. This has the Accuton C30-6-358 tweeter suspended below the Accuton C173-6-191-E mid bass driver on an isolated and inter changeable tweeter baffle.
The plan is to build two of these cabs, and join them together with one cabinet inverted to end up with a MTM version. I can increase the spacing between the two cabs, with an additional wooden board in between if required. Iam just posting a rough sketch below. And please bear with my poor drawing skills 🙄
I have the Accuton C30-6-358 tweeter originally used in the build. And subsequently, I got my hands on some Accuton C51-6-282 2" upper mid domes. And I also got a Raal 70-20 XR AM ribbon tweeter. Now Iam considering replacing the original Accuton C30 tweeter, with C51-Ribbon-C51 arrangement. So this will end up being a mid bass - 2" mid dome - Ribbon - 2" mid dome - mid bass configuration. The idea is to end up with a virtual point source mid range cabinet that goes from 80 hz to 20khz.
The mid bass will be crossed over to the mid dome between 800 to 1000 hz. And mid dome to ribbon between 3800 to 5000 hz. The above frequencies were chosen to keep all drivers below their beaming frequency. I just took the stated cone diameter in their specs, and calculated their beaming frequencies based on the formula 343/cone dia. I hope this method is "ok" 😛
Used this way, do I still have to simulate the horizontal dispersion on VitiuxCad before going ahead with the build. I intend to keep all cabinet dimensions original as designed by Mr.Troels. And only replace the original tweeter. And the new tweeter baffle though higher to accommodate the additional drivers, will still have the exact same horizontal sloping dimensions to the sides. And considering that Iam lowering the original crossover frequency from about 2200 hz to 1000 hz, the CTC driver spacing should be fine I believe.
So my question is, used this way, do I still have to carry out any simulations for horizontal dispersion as all the drivers will be used below their beaming frequencies. And I will be going active with a Sublime audio K235 active crossover where I can adjust the crossover frequencies and levels only, as Iam new to the DIY world, and would'nt be able to simulate a crossover if my life depended on it. So considering all the above, should I undertake this build, or is it doomed to fail already. 😱
Thanks in advance for any and all advise.
Additional- Mr.Troels originally designed these cabs with the port tuned to 40hz. Though I would like to keep the bass below 100 or 120hz to keep the cone excursion and distortion lower. And will build a bass cab below to reach 100 hz. I got a scanspeak 26W / 8867 for this. But cannot find any builds or schematics using this particular driver. Any guidance about using this driver in a build will be very helpful. Thanks again 🙂
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Keep trying! We are all born knowing nothing.
To create an ideal driver sim you need to know the size of the box face in mm and where each driver is positioned. I find using an app like inkscape can help you make the boxes as a vector image (https://inkscape.org/). Graph paper works too.
You will then make a baffle sim for each driver or in your case the tweeter, the pair of mids, and the woofer would be your sim, In the baffle simulator you can export the directivity measurements of each.
Here is a sim I made of a tweeter on a baffle. Note the sim mic is over the tweeter. You need to know the SD of all of your drivers. For your mid you will use the count=2. The export is the bottom in the bottom right. Be sure to save each drivers baffle sim as you place them. You will need the baffle sim later when you take real measurements of the woofer. I suggest reading the vcad manual for real measurements because like the rew guide.
Next you will import the files you just exported out of the baffle sim into the drivers section of vcad:
Now you can add each driver to the XO section and you are off to the races. The mindset to keep is that each driver has its own set of directivity measurements/settings. Also change the vcad preferences to your EQ tool
Wow...thanks a ton for taking the time to post such a detailed and elaborate explanation. Much appreciated 🙂
I seem to get a handle on what needs to be done from the above. Seems there is no replacement for learning one of these Sim tools if I want to keep faffing in the longer term. Thanks a lot again ... With gratitude - Newlash09
'Sound is round' and in theory the diaphragm is a perfect piston, so from the driver's Fs to the voice coil's frequency diameter it's pistonic, so above this point any higher frequencies must either travel along the surface of the diaphragm and/or the dustcap, i.e. its TL modes BW that are governed by open cylinder (pipe) modes.
Since sound power expands exponentially we can 'close enough' find frequency (mean) XO points on it so that multiway and/or arrayed speakers can 'layer' their output on top of each other in the proper time offset (time aligned*/focused) over long distances.
Example: 20 Hz Fs, 3" (7.62 cm) dia. VC
~34400 cm_sec/pi/7.62 = ~1437 Hz
(20*1437)^0.5 = ~169.5 Hz mean and if too low, then (169.5*1437)^0.5 = 493.6 Hz, etc., up to the 1437 Hz limit
* Assuming the speakers are properly time aligned either physically and/or electronically
Since sound power expands exponentially we can 'close enough' find frequency (mean) XO points on it so that multiway and/or arrayed speakers can 'layer' their output on top of each other in the proper time offset (time aligned*/focused) over long distances.
Example: 20 Hz Fs, 3" (7.62 cm) dia. VC
~34400 cm_sec/pi/7.62 = ~1437 Hz
(20*1437)^0.5 = ~169.5 Hz mean and if too low, then (169.5*1437)^0.5 = 493.6 Hz, etc., up to the 1437 Hz limit
* Assuming the speakers are properly time aligned either physically and/or electronically