This is what I want to do somehow. I guess it's not difficult for midhigh and tweeter.
I am thinking of just the module in the cylinder shape. So they are just some simple cylinders with no practical cavity, but just holding the driver and binding posts, and provide cover for the wiring.
For Satori MD60N, the midigh of POR, it has some long tapered back chamber, so I need to hide it from people's view.
Scanspeak D2104, the tweeter of POR, has a pretty large faceplate for the diaphragm size, so a plastic tube slightly wider than the motor assembly and allowing back mount to replace the faceplate seems to be a good thing to do.
When used with a midrange or woofer, a minimal circular baffle does not present any real problem. As @tmuikku pointed out, the baffle signature is low.
I was thinking about tweeters mounted in the end of a cylinder when I talked about this. There are so few tweeter options with minimal flanges (50 mm or less), so we will be typically using a 105 mm cylinder to mount the tweeter, and in that case a sharp edge creates some problems for us. In this situation, it might be better to try a larger cylinder so that a radius edge can be used... for example, a 155 mm cylinder with a 25 mm radius edge around the tweeter: 25 mm radius + 105 mm tweeter flange + 25 mm radius = 155 mm total cylinder diameter. Simulations or prototyping might reveal that an even larger cylinder and larger edge radius might be better. A lot of it will depend on what you can build. I limit myself to 37 mm radius because that is the largest router bit I can easily use with my equipment (and it aint really that easy).
A rectangular or trapezoidal box with a large radius might be baffle shape that you consider. I personally would find this kind of structure easier to construct, and I like the look. You will have to decide what you can build, and what looks good to you.
How to make a 3-4 way speaker without edge diffration problems? (below 10kHz) With wide and smooth directivity.
Simple - use minimal square or whatever shape baffles! This is the idea behind B&W Nautilus and alike speakers. Multiway dipoles use same idea but with narrower radiation because of 90deg null.
But stacking these boxes and using "normal" crossover slopes will create more interferences...
Axial response simulation with the Edge
Simple - use minimal square or whatever shape baffles! This is the idea behind B&W Nautilus and alike speakers. Multiway dipoles use same idea but with narrower radiation because of 90deg null.
But stacking these boxes and using "normal" crossover slopes will create more interferences...
Axial response simulation with the Edge
Last edited:
^anything small compared to transducer size works fine, square or round almost same. Sealed back gives wide coverage pattern system though. Tweeter on big waveguide and then big MID and woofer wpould make DI higher, while still keeping edge diffraction issues at bay. Like OB, select which works toward the goal.
Hi,
in regards of the problematic back wave that emits, yeah, wiggle gone means the secondary sound is way down in SPL, -20db secondary sound makes 1db interference ripple. Rest of it, size of the thing can be utilized for the total system directivity. Want high DI then just make the baffle/structure big, but either use big transducer as well, or big roundovers to cure the wiggle. Main diffraction hump can be utilized for higher DI, or make same sized object a sphere and DI stays bit lower. One can have narrow baffle lower DI system with low diffraction issues,or wide baffle higher DI system with low diffraction issues, these are not mutually exclusive.
Logic gives lot of comfort to say that the main diffraction hump can be utilized without penalty regards timing or spatial aspects, outside how DI affects system sound. These would be problem higher up in frequency where the wiggle would also be due to same reason which is, delay to edge is long compared to wavelength.
On main diffraction hump wavelength is long compared to delay to the edge, half wavelength or less. Thats why there is amplitude hump on-axis, constructive interference as the backwave is in opposite polarity. For same reason observed from 90 off axis from opposing side there is destructive interference, as it is now ~one wavelength roundtrip for the backwave.These make the main diffraction hump higher a DI. This would be sin for almost all speakers, only big radius roundovers can mitigate the main diffraction hump, when the system approximates a sphere, these are very rare even in DIY land.
Last edited:
Looking at the big picture l see a problem with the SB MD60.
Its front plate is 130 mm or larger than a 5 inch driver. This will place more than optimal distance to the centre of a typical dome tweeter for the crossover design.
GONG.
You would be better of with a Bilisma mid dome and their 25mm tweeter. The front plate of the tweeter is only 68mm.
Their 3” dome front plate is 121 mm
Think about a 4 inch cone upper mid!
Some brands have truncated front plates. In think on the balance of probabilities it could be better alternative looking at the acoustic solution.
It will go lower too. 250-3000 hertz.
I recall Seas or Scan have truncated versions.
The driver centre distance @ 3000 hertz crossover is very important from the imaging and point source perspective.
Attachments
Last edited:
I bought this up because while diffraction is important for the distance between drivers on the crossover. Steep active filters can help minimise destructive lobes in the vertical plane but a good design engineers out the problem before it can happen.
The first decision is to determine the acoustic design point. Generally this is on axis with the tweeter. However there is a trade off where this practice places the mid upper midrange driver below the listening height of say 93cm at 80cm.
What is the impact?
The upper mid driver is now off axis and the distance to this driver is greater to the listener position than the tweeter. Assuming the 8” or 6 1/ 2 “ mid bass driver is below upper mid range this places it at least 27cm below the tweeter acoustic centre. The distance to the listener is even further than the upper mid dome.
Looking at this from the spread of the driver pass bands the lower mid is operating up to 800 hertz while the tweeter is operating from 3000 hertz or possibly 3800 hertz.
You realise the SB 60mm mid dome with the 130mm front plate is a fill in driver from
800 hertz to 3000 hertz.
How does this play out on creating a seemless translation of harmonic overtones?
If you listen in the far field say 5 metres it might not impact on coherency or driver integration but at 2.5 metres l would be questioning the length of this mid range high frequency array.
So what are your options?
You could place the lower mid range driver above the tweeter. You could also increase the width of the upper midrange driver from say 400 to 3000 hertz. The effect of this is that the entire mid range is now cover by one driver.
The lower mid range driver is removed or is now operating as a bass driver from 40 to 400 hertz.
The question is what trade are you going to live with?
I believe these trade offs should be considered and a decision made before looking at diffraction.
The first decision is to determine the acoustic design point. Generally this is on axis with the tweeter. However there is a trade off where this practice places the mid upper midrange driver below the listening height of say 93cm at 80cm.
What is the impact?
The upper mid driver is now off axis and the distance to this driver is greater to the listener position than the tweeter. Assuming the 8” or 6 1/ 2 “ mid bass driver is below upper mid range this places it at least 27cm below the tweeter acoustic centre. The distance to the listener is even further than the upper mid dome.
Looking at this from the spread of the driver pass bands the lower mid is operating up to 800 hertz while the tweeter is operating from 3000 hertz or possibly 3800 hertz.
You realise the SB 60mm mid dome with the 130mm front plate is a fill in driver from
800 hertz to 3000 hertz.
How does this play out on creating a seemless translation of harmonic overtones?
If you listen in the far field say 5 metres it might not impact on coherency or driver integration but at 2.5 metres l would be questioning the length of this mid range high frequency array.
So what are your options?
You could place the lower mid range driver above the tweeter. You could also increase the width of the upper midrange driver from say 400 to 3000 hertz. The effect of this is that the entire mid range is now cover by one driver.
The lower mid range driver is removed or is now operating as a bass driver from 40 to 400 hertz.
The question is what trade are you going to live with?
I believe these trade offs should be considered and a decision made before looking at diffraction.
Attachments
http://www.legendspeakers.com.au/ultimate_active/
This link is good summary of how a loudspeaker designer went about defining similar systems.
This link is good summary of how a loudspeaker designer went about defining similar systems.
Back in 2003 I heard a DEQX active system, I think it was the first high end DEQX system?
The trapezoid cabinet time aligned the drivers physically and eliminated the "cliff edge" baffle step with the tapered width.
This reduced the DSP load on the DEQX which was used for crossover and Eq'ing. Worth mentioning the cabinet weight - 97Kg each! There was a lot of tech explanation in the brochure relating to the cabinet being 1,000 times heavier than the moving mass of the drivers... I can tell you those speakers had incredible transient / bass mid ... Drums were giggle out loud real!
"Quote from Positive Feddback Magazine reviewer
"Overkill Audio showed their Ovation speakers and electronics designed for them by deHavilland. The room also used cables from Crystal Cable, as well as equipment from DEQX and Equi=Tech. The sound in this room was very powerful and... firm. Like rock-solid in its ability to move sound through the air. Really quite stellar this is by far the best I have heard the Manger driver sound."
The trapezoid cabinet time aligned the drivers physically and eliminated the "cliff edge" baffle step with the tapered width.
This reduced the DSP load on the DEQX which was used for crossover and Eq'ing. Worth mentioning the cabinet weight - 97Kg each! There was a lot of tech explanation in the brochure relating to the cabinet being 1,000 times heavier than the moving mass of the drivers... I can tell you those speakers had incredible transient / bass mid ... Drums were giggle out loud real!
"Quote from Positive Feddback Magazine reviewer
"Overkill Audio showed their Ovation speakers and electronics designed for them by deHavilland. The room also used cables from Crystal Cable, as well as equipment from DEQX and Equi=Tech. The sound in this room was very powerful and... firm. Like rock-solid in its ability to move sound through the air. Really quite stellar this is by far the best I have heard the Manger driver sound."
And it's smaller brother, a good example if someone don't want to struggle to create a tapered enclosure.Looks familiar
Rob
Yes an older passive design with several versions over many years. The ratio of cabinet weight vs mms is not good? Why?
Rob
I got the idea from the Overkill brochure and it has consistently proven to be a good one. Its not always practical even in DIY, and very rarely in commercial designs but the goal is to minimise cabinet rocking or even "walking" in extreme cases. I have posted about this recently maybe back in this thread?
Edit, I posted about this on another thread, hope this makes sense... The Overkill brochure had graphs and accelerometer data and actual baffle / cabinet movement readings so it was all understandable and logical. I lost the brochure years ago so hope my version makes sense!
Edit: Yes please check my post back on page 15, post 292 on this thread. https://www.diyaudio.com/community/threads/4-way-instead-of-3-way.413297/post-7705731
Cheers
A.
Edit, I posted about this on another thread, hope this makes sense... The Overkill brochure had graphs and accelerometer data and actual baffle / cabinet movement readings so it was all understandable and logical. I lost the brochure years ago so hope my version makes sense!
Edit: Yes please check my post back on page 15, post 292 on this thread. https://www.diyaudio.com/community/threads/4-way-instead-of-3-way.413297/post-7705731
Cheers
A.
Last edited:
Back to the topic l watched an interview of one of the top model Wilson Benesch.
The design faced similar issues discussed here. Aside from the compound loading to halve the Vas the vertical layout is intuitive.
https://wilson-benesch.com/resolution_3zero_floorstanding_loudspeaker/
https://wilson-benesch.com/omnium_floorstanding_loudspeaker/
https://wilson-benesch.com/p3-0_floorstanding_loudspeaker/
I still think the Wilson approach is the most flexible diy friendly concept.
https://www.wilsonaudio.com/products/sasha/sasha-v
The mid and hf will be the area to be tweaked and tinkered. Making that a removable head on the main bass enclosure make perfect sense.
Adding the complex of cylinder shaped sub enclosure adds complexity that may not add any objective performance.
What l like about the head on the Wilson concept is that it can be tilted up or down by raising or lowering the rear. Those are the sort of adjustments that are going to dial in and get solid gains out of high performance drivers.
The design faced similar issues discussed here. Aside from the compound loading to halve the Vas the vertical layout is intuitive.
https://wilson-benesch.com/resolution_3zero_floorstanding_loudspeaker/
https://wilson-benesch.com/omnium_floorstanding_loudspeaker/
https://wilson-benesch.com/p3-0_floorstanding_loudspeaker/
I still think the Wilson approach is the most flexible diy friendly concept.
https://www.wilsonaudio.com/products/sasha/sasha-v
The mid and hf will be the area to be tweaked and tinkered. Making that a removable head on the main bass enclosure make perfect sense.
Adding the complex of cylinder shaped sub enclosure adds complexity that may not add any objective performance.
What l like about the head on the Wilson concept is that it can be tilted up or down by raising or lowering the rear. Those are the sort of adjustments that are going to dial in and get solid gains out of high performance drivers.
The reason is that a listeners head height varies and that variation has a direct impact on the smoothness of the crossover points @ 800 and 3000 hertz. Even slight 0.5 db change in the continuity of the response in the 1000-3000 are discernible. That’s difficult to measure in a room. Even more tedious is messing around with the network sittings. Its is not the way to going about this adjustment.
This gets back to my previous point that
placing the crossover points close together like that will make it sensitive to response fluctuations with listening height.
Moving the crossover point down to about 400-500 hertz might seem to fly in the face of using a 2 inch driver. Well use a 3 inch driver because that as a decision trade off is more valuable if you value coherence.
The dispersion of modern dome radiators is about varying the diaphragm thickness and the dome geometry.
Capturing this range in a single driver is arguably more important subjective than anything else.
My fallback position is the Biliesma mid domes if you must use a dome radiator. But narrowing down your options to a dome does limit you if you want to evaluate different drivers.
Seas, Scan, Eton, Peerless all make competent cone drivers. There are some very good ceramic treated diaphragms in 3-4 inch categories. Textreme would be another new material to evaluate.
The mms of this driver is only 4.7 gm. It has an under hung motor and +- 3.4 mm Xmax.
https://www.madisoundspeakerstore.c...anspeak-illuminator-12mu/8731t-00-4-midrange/
This gets back to my previous point that
placing the crossover points close together like that will make it sensitive to response fluctuations with listening height.
Moving the crossover point down to about 400-500 hertz might seem to fly in the face of using a 2 inch driver. Well use a 3 inch driver because that as a decision trade off is more valuable if you value coherence.
The dispersion of modern dome radiators is about varying the diaphragm thickness and the dome geometry.
Capturing this range in a single driver is arguably more important subjective than anything else.
My fallback position is the Biliesma mid domes if you must use a dome radiator. But narrowing down your options to a dome does limit you if you want to evaluate different drivers.
Seas, Scan, Eton, Peerless all make competent cone drivers. There are some very good ceramic treated diaphragms in 3-4 inch categories. Textreme would be another new material to evaluate.
The mms of this driver is only 4.7 gm. It has an under hung motor and +- 3.4 mm Xmax.
https://www.madisoundspeakerstore.c...anspeak-illuminator-12mu/8731t-00-4-midrange/
Last edited:
Thank you very much for bringing this up. I looked at the picture of the Satori, and it appears that the front ring could be removed by unscrewing 3 in the back side. That would still leave the diameter of the rest of the driver at 114mm. Practical minimum diameter of the cylinder is probably 120mm, so about 2x of the diaphragm diameter. How bad is the baffle's effect if it's 120mm wide, in the band from 700~ 5000Hz?
Similar thing could be done for D2104 to reduce it to 75 ~ 80mm. It is still over 3x of the diaphragm. Covering over 4000 ~ 5000Hz, how bad is it? Sorry that the simulator doesn't seem to work well on Mac...
The crossover is probably over 4000Hz. Does this change anything?
It’s a double edge sword with some quirks.
Yes it above 2000 hertz and 3000 hertz which 2 way systems struggle with.
But at 4000 hertz wavelength is 1/2 that of 2000 hertz. Its 86mm.
Technically when the distance of the diaphragm centres are greater than the wavelength of the crossover some issues start to surface in the practice implementation.
This principally effects the vertical axis polar response at the listening position and the global horizontal polar response.
In detail
Ideally want the diaphragm centres one wavelength or less at the crossover point to avoid irregularities in the vertical polar response. A sharper crossover slope reduces the irregularities and an FIR crossover is good. But the drivers occupy still different locations. This means they both can’t be on axis to the listening position.
This creeps into your minimum listening distance for system coherence. That is why l referred to having an adjustment of the angle on both the upper mid and the tweeter.
When you design the network you will normally use the tweeter as the design point or on axis listener position. So finding that needs some physical adjustment and is best done by tilting the mid high frequency array.
Horizontally global polar response.
Matching the off axis polars is also important. My suggestion is to initially run a series of measurements at 5 degree intervals on an IEC baffle (scaled to this frequency range with both drivers mounted one above the other.
Measure each individually. Then compare the off axis curves. You want the 0-30 degree to line up and the 30-50 degree to be reasonably close past the crossover point.
This will give you a baseline to validate your drivers are going to work properly with your proposed crossover points. What happens on your actual baffles is in the lap of the gods.
This is about the imaging of the system.
You don’t want pits or bumps in the polar response around the crossover region.
As l keep saying it’s about the overtones being uninterrupted.
The loudspeakers job is to translate with a minimum of errors. A multi way system is about greater precision but the implementation unless done skill fully can bring it all undone.
You can’t predetermine everything in advance but you can predict where the accidents (the errors) will likely occur because you made some informed decisions.
The SB dome mid with either work or it won’t in your scenario. They are not crazy expensive so give it a shot.
Yes it above 2000 hertz and 3000 hertz which 2 way systems struggle with.
But at 4000 hertz wavelength is 1/2 that of 2000 hertz. Its 86mm.
Technically when the distance of the diaphragm centres are greater than the wavelength of the crossover some issues start to surface in the practice implementation.
This principally effects the vertical axis polar response at the listening position and the global horizontal polar response.
In detail
Ideally want the diaphragm centres one wavelength or less at the crossover point to avoid irregularities in the vertical polar response. A sharper crossover slope reduces the irregularities and an FIR crossover is good. But the drivers occupy still different locations. This means they both can’t be on axis to the listening position.
This creeps into your minimum listening distance for system coherence. That is why l referred to having an adjustment of the angle on both the upper mid and the tweeter.
When you design the network you will normally use the tweeter as the design point or on axis listener position. So finding that needs some physical adjustment and is best done by tilting the mid high frequency array.
Horizontally global polar response.
Matching the off axis polars is also important. My suggestion is to initially run a series of measurements at 5 degree intervals on an IEC baffle (scaled to this frequency range with both drivers mounted one above the other.
Measure each individually. Then compare the off axis curves. You want the 0-30 degree to line up and the 30-50 degree to be reasonably close past the crossover point.
This will give you a baseline to validate your drivers are going to work properly with your proposed crossover points. What happens on your actual baffles is in the lap of the gods.
This is about the imaging of the system.
You don’t want pits or bumps in the polar response around the crossover region.
As l keep saying it’s about the overtones being uninterrupted.
The loudspeakers job is to translate with a minimum of errors. A multi way system is about greater precision but the implementation unless done skill fully can bring it all undone.
You can’t predetermine everything in advance but you can predict where the accidents (the errors) will likely occur because you made some informed decisions.
The SB dome mid with either work or it won’t in your scenario. They are not crazy expensive so give it a shot.