Hi all,
I know there's been quite a few Blanda threads and they are quite simple speakers overall, but this is my first build by myself and I was looking for advice on a few areas. I am hoping to have this done in a few weeks (the bracing may delay that) so I thought it would be nice to open a thread and see what everyone here thinks or can suggest to help me.
The drivers I am using are the Pluvia 7.2 HD.
I will be using two 28cm Blanda bowls glue together. The 28cm bowls will give around 9 litres internal volume before bracing and stuffing. For a sealed QTC around 0.72, the Pluvias need around 8.5 litres of volume. For a flat vented enclosure they need around 15 litres. Vented I may get a f3 of around 60hz with 7 litres of volume (taking some off for bracing and driver volume). I will probably go with sealed enclosures as I want to use a lot of filling to damp any resonances and standing waves. My understanding is that you shouldn't really do this for vented enclosures, but correct me if I'm wrong. I also hope to use this as the tweeter for a WAW in the future if they sound good, but I think that's at least a year or two away as I don't have the space at the moment.
I have purchased just one 28cm Blanda bowl for now to see how the drilling and cutting goes. The Pluvia are around 122mm edge to edge and require a driver cut-out of 100mm. I am going to use a 102mm hole saw to cut the initial hole and then sand or cut down the sides to make a flat surface to mount the drivers onto.
Inside I am thinking to line the bowls with a heavy material such as bitumen (any suggestions on lining welcome, wondering if thick felt such as this does the same job) and also stuff with a fibre of some kind.
If anyone can provide any tips on the construction, what I should avoid, what to do and what not to do that would be helpful.
Thanks
I know there's been quite a few Blanda threads and they are quite simple speakers overall, but this is my first build by myself and I was looking for advice on a few areas. I am hoping to have this done in a few weeks (the bracing may delay that) so I thought it would be nice to open a thread and see what everyone here thinks or can suggest to help me.
The drivers I am using are the Pluvia 7.2 HD.
I will be using two 28cm Blanda bowls glue together. The 28cm bowls will give around 9 litres internal volume before bracing and stuffing. For a sealed QTC around 0.72, the Pluvias need around 8.5 litres of volume. For a flat vented enclosure they need around 15 litres. Vented I may get a f3 of around 60hz with 7 litres of volume (taking some off for bracing and driver volume). I will probably go with sealed enclosures as I want to use a lot of filling to damp any resonances and standing waves. My understanding is that you shouldn't really do this for vented enclosures, but correct me if I'm wrong. I also hope to use this as the tweeter for a WAW in the future if they sound good, but I think that's at least a year or two away as I don't have the space at the moment.
I have purchased just one 28cm Blanda bowl for now to see how the drilling and cutting goes. The Pluvia are around 122mm edge to edge and require a driver cut-out of 100mm. I am going to use a 102mm hole saw to cut the initial hole and then sand or cut down the sides to make a flat surface to mount the drivers onto.
Inside I am thinking to line the bowls with a heavy material such as bitumen (any suggestions on lining welcome, wondering if thick felt such as this does the same job) and also stuff with a fibre of some kind.
If anyone can provide any tips on the construction, what I should avoid, what to do and what not to do that would be helpful.
Thanks
I have drawn a number of bowl designs, above for the A5.2/3 (CHN-50), and the large bowls for the A7ms. Also one with the grolander bowl on the back
I have done at least a sketch for the CHR-70, P7HD fits the same size as it and the A7ms.
Optimum volume for a P7HD miniOnken is 9 litres. 16 litres seems a bit much even for a more typically tuned BR. What does th esim look like (i have a broken ethernet hub and have no accessto my modeler).
Do note that teh bowls are not full semispheres and need a band where they meet to become closer to a sphere. You will also find the bowls do not all match.
Good way to make the enclosure smaller and more likely to ring. Doing this to a regular box typically degrades things, in a shape like a sphere it is a real waste. The shape is naturally really strong and non-resonant. Bituminum damps the box walls and east up space, lining with felt damps th eair space and is recommend.
Also, re damping, the centre of the sphere needs the damping most, in my design i use that point for something else.
Sealed can be fully filled with damping, vented should be lind. With sealed you will probably want helper woofers. Vented they can be quite satisfying on there own.
dave
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Hi Dave,
Thanks for your reply. I didn't even realise they had that gronsaker bowl, I like the shape but it looks like it'll be quite a bit less in volume.
So in your plans the extra "band" in the middle is to primarily to increase the enclosure size, rather than to brace it? I did also want to brace the back of the drivers too.
I ran the sim on a website to get the numbers quickly, the blue line is 14.98 litres and a flat response according to them. The red line is 8 litres (F3 is 58hz)
I am in two minds about vented or sealed as I know vented will be better standalone, but sealed should in theory be better as a midtweeter, especially with the extra stuffing. Sealed F6 is around 66hz and they would only be used nearfield and near a wall so I think it might be okay. I do want to use them as midtweets one day, I have had some 12PWs collecting dust for a while, but I don't have the space/need for them right now. I am considering just adding a port for now and then in the future I may open them up and stuff the enclosure and seal the port with a port plug. With that being said, I don't even have a need for these speakers at the moment, but at least they're easy to store away 😀
One concern with vented is that I would be approximating the enclosure size when calculating the vent, not sure how much difference this would make if I'm a little off.
Would lining the enclosure with felt not cause the same issues you are describing with bitumen? I am asking because if it were vented then I would need to line it.
Thanks
Thanks for your reply. I didn't even realise they had that gronsaker bowl, I like the shape but it looks like it'll be quite a bit less in volume.
So in your plans the extra "band" in the middle is to primarily to increase the enclosure size, rather than to brace it? I did also want to brace the back of the drivers too.
I ran the sim on a website to get the numbers quickly, the blue line is 14.98 litres and a flat response according to them. The red line is 8 litres (F3 is 58hz)
I am in two minds about vented or sealed as I know vented will be better standalone, but sealed should in theory be better as a midtweeter, especially with the extra stuffing. Sealed F6 is around 66hz and they would only be used nearfield and near a wall so I think it might be okay. I do want to use them as midtweets one day, I have had some 12PWs collecting dust for a while, but I don't have the space/need for them right now. I am considering just adding a port for now and then in the future I may open them up and stuff the enclosure and seal the port with a port plug. With that being said, I don't even have a need for these speakers at the moment, but at least they're easy to store away 😀
One concern with vented is that I would be approximating the enclosure size when calculating the vent, not sure how much difference this would make if I'm a little off.
Would lining the enclosure with felt not cause the same issues you are describing with bitumen? I am asking because if it were vented then I would need to line it.
Thanks
Surprisingly not all that much.
It is a convient place to put the vents. Never thot of it as brace, it does a bit, but spheres don’t really need bracing.
The blue curve breaks my “1st derivative of the FR curve does not pass thru zero more then once"… it is an indicator the box is too big.
That is true. A vented box can have damping inserted intot he vent to push it heavily aperiodic and end up in between.
You lucky guy. Really nice woofers.
Now the sealed box starts making a lot more sense.
The 2 do very different things. A reflex is usually lightly damped to kill HF stuff from bouncing around.
Bituminum damps the box structure (unneeded) and eats up volume. Damping damps the air space and is irrelevant to th ebox structure and effectivily increases th ebox volume slightly.
dave
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I feel like I have seen you or someone mention this before, I thought the curve did look odd but couldn't put my finger on it. I am a bit rusty on my knowledge at the moment.
I have drilled the first bowl, just have to flatten the edges to mount the driver now. Still far from completion as I've not even decided whether to go sealed or ported yet. Once I figure it out and progress the project I will post some pics 🙂
Thanks for all your help Dave. I may have some more questions along the way but that's all I need for now 🙂 if you have any other tips they are welcome.
Hi all,
I'm hoping to have these completed either tonight or over this weekend. Just wanted some final sense checks.
I am using this speaker stuffing and I'm going to stuff it at 20g per litre, so around 160 gams per speaker. If anyone thinks this is too much or too little, please let me know.
@planet10 I am probably going to omit the band from the middle, just for ease as this is my first time really doing any woodworking. But if you think it's important, please let me know. As a reminder these will just be sealed and will be used as tweeters with helper woofers one day (xover around 250hz).
Thanks!
I'm hoping to have these completed either tonight or over this weekend. Just wanted some final sense checks.
I am using this speaker stuffing and I'm going to stuff it at 20g per litre, so around 160 gams per speaker. If anyone thinks this is too much or too little, please let me know.
@planet10 I am probably going to omit the band from the middle, just for ease as this is my first time really doing any woodworking. But if you think it's important, please let me know. As a reminder these will just be sealed and will be used as tweeters with helper woofers one day (xover around 250hz).
Thanks!
It appears to me that the point of the "band" in the middle of Dave's design is to create 6 reflex ports. The disc is cut into 6 pizza slices and there are gaps between the slices when installed, creating the ports.
If this is true, then you definitely don't want to implement this for your sealed enclosure. (I know, overstating the obvious).
Yes cogitech, that is exactly how it works. The band would be much simplier in a sealed enclosure.
dave
dave
Thank you both.
@planet10 do you think it's worth adding a bit of support for the back of the driver? I know normally in your designs there is. Rather than a band I'm going to look at also adding some small bracing around the join, more so to give them a secure connection between the two bowls rather than to brace them.
Okay, I will start with 10g and see how it goes from there, I will look into it a bit more as well.
@planet10 do you think it's worth adding a bit of support for the back of the driver? I know normally in your designs there is. Rather than a band I'm going to look at also adding some small bracing around the join, more so to give them a secure connection between the two bowls rather than to brace them.
Got a bit of a newb question.
Should I have something inside to stop the stuffing moving about? Should I glue it in place around the sides of the bowl, or is it okay to just float loosely. I thought it might be an issue if it goes in the driver or does this not matter?
Thanks
Should I have something inside to stop the stuffing moving about? Should I glue it in place around the sides of the bowl, or is it okay to just float loosely. I thought it might be an issue if it goes in the driver or does this not matter?
Thanks
If it is a reflex the walls are lined and they should be fixed. Hot glue is good. For sealed the volume is filled and if the damping is decent, and decently teased, it wil stay where you put it.
If it isn’t decent — i am in the midst of a fix where the recycled cotton felt disintegrated, got inside the frame and made me thinlk i killed the driver. If you worry about this some very pourous cloth stretched over the back of the driver.
dave
If it isn’t decent — i am in the midst of a fix where the recycled cotton felt disintegrated, got inside the frame and made me thinlk i killed the driver. If you worry about this some very pourous cloth stretched over the back of the driver.
dave
Hi Dave,
Thanks for clarifying. I think because it's a large and empty bowl it makes a good shape for sliding things about. I've attached a photo of one half with the stuffing in it.
I went with 15g and it seems about right, it looked more teased before I put it in the bowl but it's like it's remerged together a bit now. The stuffing reaches roughly around to the back of the driver where bracing would usually go.
I am going to try to tease it back out some more and see if it sticks a bit better, otherwise I'll look at covering the driver or adding something inside to keep it from moving about
Thanks for clarifying. I think because it's a large and empty bowl it makes a good shape for sliding things about. I've attached a photo of one half with the stuffing in it.
I went with 15g and it seems about right, it looked more teased before I put it in the bowl but it's like it's remerged together a bit now. The stuffing reaches roughly around to the back of the driver where bracing would usually go.
I am going to try to tease it back out some more and see if it sticks a bit better, otherwise I'll look at covering the driver or adding something inside to keep it from moving about
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They are completed now.
They have less bass than I thought they would, based on the Sims, but perhaps 80hz f3 is even less than I thought (I feel like some male vocals sound quiet or recessed). I will measure in room response at some point. I'm not fussed as I'm hoping to use them with a 250hz xover. I need to try different amounts of toe out as well, but I'm testing them on my desk at the moment and there's no space to move them as they will crash into my monitor.
Trying to judge them on mids and trebles alone is difficult as most music has some bass in there, but on early impressions some things are definitely impressing me. I am going to test with a sub once I have time, hopefully it'll give me a more complete picture of how they can really sound.
I definitely prefer the top end over the 7ms I have, not sure what's up with them. I feel like the directivity is better too, but that may be down to the extra treble.
I will try to post a picture later.
Thanks
They have less bass than I thought they would, based on the Sims, but perhaps 80hz f3 is even less than I thought (I feel like some male vocals sound quiet or recessed). I will measure in room response at some point. I'm not fussed as I'm hoping to use them with a 250hz xover. I need to try different amounts of toe out as well, but I'm testing them on my desk at the moment and there's no space to move them as they will crash into my monitor.
Trying to judge them on mids and trebles alone is difficult as most music has some bass in there, but on early impressions some things are definitely impressing me. I am going to test with a sub once I have time, hopefully it'll give me a more complete picture of how they can really sound.
I definitely prefer the top end over the 7ms I have, not sure what's up with them. I feel like the directivity is better too, but that may be down to the extra treble.
I will try to post a picture later.
Thanks
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My P7.2HD’s really came in to their own at the 50+ hour mark. I used them gently as recommended and slowly increased volume. Bass developed later in the process for sure.
I have broken them in with no enclosure for at least 50-100 hours (can't remember now as it was last year) so I think they're good on that front, but maybe they'll improve further.
I think the issues I have with the sound are from them being sealed. I wouldn't have made them sealed to use as standalone speakers of course. I'm tempted to put a port in them or finish my WAW project, but I think that's going to take a lot more time
I am finding it tricky to pin down the sound character as they sound a little hollow at times (perhaps a bit trebly and lacking in mids somewhere) but I think toeing them out more will help with that. Maybe it's just the lack of bass but I've not had time to test today, hopefully tomorrow!
I think the issues I have with the sound are from them being sealed. I wouldn't have made them sealed to use as standalone speakers of course. I'm tempted to put a port in them or finish my WAW project, but I think that's going to take a lot more time
I am finding it tricky to pin down the sound character as they sound a little hollow at times (perhaps a bit trebly and lacking in mids somewhere) but I think toeing them out more will help with that. Maybe it's just the lack of bass but I've not had time to test today, hopefully tomorrow!
What enclosure did you go with?
Here are a few pictures for anyone interested in doing their own bowls (ignore the wire mess on my desk). I think they look great and everyone who's seen them thinks they look cool. Tempted to port them and use them as desk speakers but I don't need new desk speakers (love my adam monitors already) and also they are so wide they crash into my monitor if I'm not careful haha
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Here are a few pictures for anyone interested in doing their own bowls (ignore the wire mess on my desk). I think they look great and everyone who's seen them thinks they look cool. Tempted to port them and use them as desk speakers but I don't need new desk speakers (love my adam monitors already) and also they are so wide they crash into my monitor if I'm not careful haha
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