LATEST UPDATE: My complex sphere build. Almost finished!
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So I have had a pair of Wilmslow Audio Prestige speakers for the last few years.
I heavily modified the stock cabinets, but have always planned to make new ones as they were not to my design and I don't think they are that good, even after my modifications.
I have spent a long time thinking about their replacements.
Having built these:
I realise the positives of spherical enclosures. The best diffraction results possible (no edges or corners), with virtually no wall vibrations (no corners or edges to allow modal behavior - just one single surface.
The only disadvantage is the internal major resonance at the diameter of the sphere. Not an issue for tweeters, or the VM752 volt mid-range dome as they both have sealed backs. But with some internal bracing this can easily be overcome anyway - just break up the internal volume as you would any normal box.
So spheres it is for me.
Then there is the issue of the pairing in the Prestige of the Volt RV3143 to the Volt VM752. The dome has to be crossed above 500hz - preferably about 600, and the RV3143 12" driver really doesn't like going that high. I never felt it 'kept up' with the 3" dome.
So what driver could hold it's own with the VM752 from about 80-600 hz? (I will be covering 90hz and down with 4x12" subs in stereo dual opposed configuration, as I think it is important to separate these frequencies with different enclosures that aren't physically connected).
After a lot of consideration and thought, I settled on the new SB acoustics 7.5" satori woofer - the MW19P-4. This will sit in a sealed sphere of 9 litres with a Q of 0.7 and nicely get me to about 80 hz, it is also very high performance with a SOTA motor, and very low Le/distortion etc. so should keep up with the VM752 much better than the RV3143.
So.....onto designs.
I decided to use Ikea bowls of different sizes as I have in previous builds - I was very impressed with the strength and internal damping of the bamboo block construction. But as the VM752 dome is rear mounted, I need to make the mid-range sphere's back detachable. So I went with the brushed steel bowls for the backs.
This decision was made after I tried damping the steel bowls with 4mm silent coat (a damping product for cars).
It is a constrained layer damping product that is specifically engineered for use with 1-2mm thick steel. I have used it before on my speakers - it works OK with MDF and plywood, but on the thin steel it is designed for, it is amazing. The steel bowls with this product layered up are deader than I have ever achieved with wood constructions. It demonstrates that constrained layer damping really is a finely engineered balance of physics.
Anyway, I digress. So, I actively choose the steel backs over bamboo backs after experimenting with getting the most inert spheres I could.
I then had the issue of rear mounting the VM752 into the dome shape. After trying a few different approaches (and scrapping a few bowls), I settled on using a very large hole saw, then a table sander to achieve a near perfect fit.
*CLICK ON IMAGES AT THE END FOR LARGER PICTURES*
I routed a lip onto the bamboo bowls to countersink them into the steel bowl, which will allow me to bolt them on and therefore be removable if I need to access the VM752 mid-range dome.
The MW19P-4 will just be screwed directly onto the bowl, so the steel back will be glued and screwed into position.
The Scanspeak 7000 tweeter is then mounted into a small bamboo bowl to allow a decent round-over and attempt to minimise diffraction. It will be mounted as close as possible to the mid-range dome to minimise lobing.
I plan to use some bamboo chopping boards to create the stands - each ball will be held in position by the stand and isolated from the others by sorbothane mounts.
Anyway here are some progress photos to show you where I am at with this project. This is obviously a work in progress, so fit and finish isn't yet where I want it to be, but for the initially rough up, I think it will be an interesting enclosure design!
More to follow...
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So I have had a pair of Wilmslow Audio Prestige speakers for the last few years.
An externally hosted image should be here but it was not working when we last tested it.
I heavily modified the stock cabinets, but have always planned to make new ones as they were not to my design and I don't think they are that good, even after my modifications.
I have spent a long time thinking about their replacements.
Having built these:
I realise the positives of spherical enclosures. The best diffraction results possible (no edges or corners), with virtually no wall vibrations (no corners or edges to allow modal behavior - just one single surface.
The only disadvantage is the internal major resonance at the diameter of the sphere. Not an issue for tweeters, or the VM752 volt mid-range dome as they both have sealed backs. But with some internal bracing this can easily be overcome anyway - just break up the internal volume as you would any normal box.
So spheres it is for me.
Then there is the issue of the pairing in the Prestige of the Volt RV3143 to the Volt VM752. The dome has to be crossed above 500hz - preferably about 600, and the RV3143 12" driver really doesn't like going that high. I never felt it 'kept up' with the 3" dome.
An externally hosted image should be here but it was not working when we last tested it.
So what driver could hold it's own with the VM752 from about 80-600 hz? (I will be covering 90hz and down with 4x12" subs in stereo dual opposed configuration, as I think it is important to separate these frequencies with different enclosures that aren't physically connected).
After a lot of consideration and thought, I settled on the new SB acoustics 7.5" satori woofer - the MW19P-4. This will sit in a sealed sphere of 9 litres with a Q of 0.7 and nicely get me to about 80 hz, it is also very high performance with a SOTA motor, and very low Le/distortion etc. so should keep up with the VM752 much better than the RV3143.
So.....onto designs.
I decided to use Ikea bowls of different sizes as I have in previous builds - I was very impressed with the strength and internal damping of the bamboo block construction. But as the VM752 dome is rear mounted, I need to make the mid-range sphere's back detachable. So I went with the brushed steel bowls for the backs.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
This decision was made after I tried damping the steel bowls with 4mm silent coat (a damping product for cars).
It is a constrained layer damping product that is specifically engineered for use with 1-2mm thick steel. I have used it before on my speakers - it works OK with MDF and plywood, but on the thin steel it is designed for, it is amazing. The steel bowls with this product layered up are deader than I have ever achieved with wood constructions. It demonstrates that constrained layer damping really is a finely engineered balance of physics.
Anyway, I digress. So, I actively choose the steel backs over bamboo backs after experimenting with getting the most inert spheres I could.
I then had the issue of rear mounting the VM752 into the dome shape. After trying a few different approaches (and scrapping a few bowls), I settled on using a very large hole saw, then a table sander to achieve a near perfect fit.
*CLICK ON IMAGES AT THE END FOR LARGER PICTURES*
I routed a lip onto the bamboo bowls to countersink them into the steel bowl, which will allow me to bolt them on and therefore be removable if I need to access the VM752 mid-range dome.
The MW19P-4 will just be screwed directly onto the bowl, so the steel back will be glued and screwed into position.
The Scanspeak 7000 tweeter is then mounted into a small bamboo bowl to allow a decent round-over and attempt to minimise diffraction. It will be mounted as close as possible to the mid-range dome to minimise lobing.
I plan to use some bamboo chopping boards to create the stands - each ball will be held in position by the stand and isolated from the others by sorbothane mounts.
Anyway here are some progress photos to show you where I am at with this project. This is obviously a work in progress, so fit and finish isn't yet where I want it to be, but for the initially rough up, I think it will be an interesting enclosure design!
More to follow...
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I am now thinking if I can make the subwoofers inert enough using push-push dual opposed configuration, I may integrate them into the base of the speakers.
I have ordered 4 of these to do the job:
At £108 each, 20mm X-max, and excellent verified Klippel measurements, I couldn't resist.
I have also ordered 1200mm length of 10" diameter 10mm thick PVC schedule 40 pipe. This is almost the same diameter as the spheres- so the design should be nicely balanced if I have the sub tube end on at the base. I am hoping the dual opposed set up will cancel out all the mechanical vibrations particularly given they are on the end of an incredibly stiff pipe.....some nice vinyl wrap and it might work......
I will keep you posted.
I have ordered 4 of these to do the job:
At £108 each, 20mm X-max, and excellent verified Klippel measurements, I couldn't resist.
I have also ordered 1200mm length of 10" diameter 10mm thick PVC schedule 40 pipe. This is almost the same diameter as the spheres- so the design should be nicely balanced if I have the sub tube end on at the base. I am hoping the dual opposed set up will cancel out all the mechanical vibrations particularly given they are on the end of an incredibly stiff pipe.....some nice vinyl wrap and it might work......
I will keep you posted.
Dual opposed works wonders. My 2x15" ppsl sub barely vibrates when pushing 110dB+. While my little 10" feels like it's going to take a walk at 90dB. Bonus points if you mount the 2 drivers using the same threaded rods, doubles as bracing since you "pre-stress" the cabinet.
This is genius! As I am using a large pipe, threaded rods to mount them is a great idea!
Pipe and 45kg of subwoofers will be arriving this week so I will get some pics up! I have also picked up some brushed steel vinyl wrap so the PVC pipe will match the steel bowls.
Still not sure if it will be too much with the subwoofers integrated into the main speakers. I do like being able to move them about a bit to get best in room response.....
looks awesome, good luck with the project!
i wonder, why you didn't go for pmc TL cabinet design then?
i wonder, why you didn't go for pmc TL cabinet design then?
If you mean loading the rv3143 with a TL cabinet instead of the ported box....what difference would that make?
Check out the response graph of the rv3143 in my first post. Pushing that driver up to meet the volt vm752 at 600hz is not ideal in my book.
So it calls for making the 3-way into a 4-way...
If I'm turning it into a 4 way....May as well pick the best drivers for the 20-90hz and 90-600 ranges. So a 7.5" midwoofer, and 4 big crazy excursion subs....are much better than a single high le 12" woofer.
Hope this makes sense.
Thought you might like to hear how effective 4mm constrained layer damping is on the 1mm steel bowl.
I presume because the resonant frequency is so high already (incredibly stiff steel hemisphere) and the wall is thin and relatively light, the damping product works so much better than it does on MDF and plywood. The treated dome is utterly dead.
Listen for yourself (be aware there is a slight echo in the room which you can hear off the walls, this isn't the treated dome!):
https://youtu.be/MpkUbizbBjI
I presume because the resonant frequency is so high already (incredibly stiff steel hemisphere) and the wall is thin and relatively light, the damping product works so much better than it does on MDF and plywood. The treated dome is utterly dead.
Listen for yourself (be aware there is a slight echo in the room which you can hear off the walls, this isn't the treated dome!):
https://youtu.be/MpkUbizbBjI
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Nice project Bushman! Alpine subs are great drivers - I have used them in many 6th order slot loaded bandpass subs - models anyhow which were then built by others with great success. Great value drivers.
Cheers X!
I was planning on making dual opposed subs like this for my X-bush spheres as you know, but the bass on those is so good with the 4x8" SB acoustics woofers that they really don't need it, but this project will do.
I am very likely to do them sealed as I will be using DSP, so don't have to worry about box tuning.
I was planning on making dual opposed subs like this for my X-bush spheres as you know, but the bass on those is so good with the 4x8" SB acoustics woofers that they really don't need it, but this project will do.
I am very likely to do them sealed as I will be using DSP, so don't have to worry about box tuning.
And yet you managed to persuade me to consider using subs without me needing them with my arrays, remember? 😀.
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😀😀😀😀
Hi wesayso!
LOL!!!, my argument still stands - I am currently using the X-bushes either side of my desk (like in the photo in the first post) so they are really high end computer monitors! They are mainly used near-field and are rarely turned up.
Going back to the maths again:
Your line arrays:
Single Vifa TC9 = 37cm2 SD
So, 50 vifas x 37cm2 = 1850cm2 total SD
3mm x-max
So VD (x-max x SD) for the 50 x Vifas = 555.0 cm3 volume displacement.
My X-bushes:
Single SB23NRXS45-8 = 216cm2 SD
So, 4 SB23s x 216cm2 = 864cm2 total SD
6.5mm x-max
So VD = 561.6cm3
i.e. - the X-bushes will move slightly more air than your arrays (and you know how good the bass is already on them!). I am sure if you were using your arrays for near field monitors either side of your desk like me, I probably couldn't have persuaded you to add subs!!!!
Honestly, given you use them at a much further distance, and for HT use, I think you will benefit from the subs (hopefully! 😉)
I still haven't built my listening room in the garage (work in progress) but when they go out there, I almost certainly will add subs, as I will need more SD.
This current project will only reach to 80 hz with the satori 7.5" woofer, so subs are definitely required!
However, your reminder makes me think I should definitely keep the subs seperate so I can move them between projects as required......Hmmm.
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Yes, it had been on my mind forever... just out of curiosity alone.
The added 1165.0 cm3 of the Scan Speaks should make some difference 😉.
But you didn't stop there! 4 of those Alpine monsters should be able to create some waves... 😛
The added 1165.0 cm3 of the Scan Speaks should make some difference 😉.
But you didn't stop there! 4 of those Alpine monsters should be able to create some waves... 😛
I know! I have been planning subs ever since I made the X-bushes, so I wanted to make some that could effortlessly do what ever was asked of them.....
I have gone for the 10" SWRs in the end, to keep them as compact as possible in the pipe (I am probably looking at using a 40cm length of pipe per pair, sealed and dual opposed).
But they will provide some decent displacement!
Alpine SWR 10D2. SD = 333cm2.
4x 333 = 1332 cm2.
x-max = 20mm
So VD = 2664 cm3 !!!
They should be all I could ever want or need!
wow guys, you may live in very solid houses to allow not your walls to check like flat planars 😱 😛 🙂
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