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curved cabinet stiffness


Arash

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actually I'm building a speaker inspired by LS but with curved sides. the first plan was to bend 3/8" plywood on a foam mold with a vacuum bag but this process is very time-consuming and trimming the curved panel to the needed size also demands time. another option is to cut CNC slices to put together to shape the curved part. this would be a faster way the the final result is more precise. dowel pins can be used to make the whole structure more rigid and reduce the assembly error. following picture is try of slices. I used BB plywood from Finland. dowel pins are 5H tolerance 8mm cobalt-steel round bars they fit in the hole just nice.

 

post-41711-0-95440000-1417588773_thumb.j

post-41711-0-76720000-1417588851_thumb.j

 

I want your opinion. If I go slice way, the whole speaker will be 206 individual pieces CNC machined to the exact size needed.  assuming urethane glue will be used, do you think this cabinet will be as stiff as non-slice cabinet? will steel pins affect (increase/decrease) box resonance?

 

 

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It seems you are building a Volti Vittora clone more than a la scala. You have built the same midrange horn, have the same driver behind it (bms492nd-mid). If you make it curved as well, it will be very close to vittora. I didn't hear one, but everyone says they are very good! How does Greg do the curved part, did you ask him. He may help you if this is for your own pleasure and not a commercial product.

 

Don't forget he uses a subwoofer with it. His Vittoras extend to 50hz. You may also consider building a horn sub to go with your project, it may be a step up. Then it will be fully horn loaded.

 

Did you decide on tweeters. Are you going to build a passive crossover or use an active system? I'll be watching this :)

 

ps. sorry for not helping with your questions. You just need to be sure that slices don't come off. I have seen that happening on a cnc layered tower once!

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It seems you are building a Volti Vittora clone more than a la scala. You have built the same midrange horn, have the same driver behind it (bms492nd-mid). If you make it curved as well, it will be very close to vittora. I didn't hear one, but everyone says they are very good! How does Greg do the curved part, did you ask him. He may help you if this is for your own pleasure and not a commercial product.

 

Don't forget he uses a subwoofer with it. His Vittoras extend to 50hz. You may also consider building a horn sub to go with your project, it may be a step up. Then it will be fully horn loaded.

 

Did you decide on tweeters. Are you going to build a passive crossover or use an active system? I'll be watching this :)

 

ps. sorry for not helping with your questions. You just need to be sure that slices don't come off. I have seen that happening on a cnc layered tower once!

 

thanks for the reply

about cloning Vittora it's a moot point. there is no plan of Vittora available for the public so the similarity of my speaker with Greg's stays on the surface. I'm gonna say my speaker will be in debt to Klipsch La Scala other than Volti Vittora.  I've been thinking about a renew curved LS cabinet since 2011. I've spent more than six months on the design and tweaking Hornresp with different drivers and the result is outstanding. I use an expensive top quality 15" woofer. the plans are about 20 pages of drawing. every single element is taken into consideration. I don't know, but my plans are seen by a guy who designed Vittoras for Greg (no I'm not gonna mention his name! ;) ) and he believes both are very very close. 

about drivers, yes I'll use BMS 4592ND. I have both 4592ND-Coax and also 4592ND-Mid. the Coax shows a little bit more linear on the Edgar style horn I built. it's also more expensive, I think I'll use only the midrange part of it. the tweeter will be a Beyma CP-25. I also thought about time-aligning the tweeter but that will conflict with a total height of ~105cm so I'll place the tweeter side by side the mid-horn.

I'm not gonna ask a guy who sells commercial stuff about his product. this is my speaker, I've designed it. I'll make it to the end and I may consider selling it for a very reasonable price.

the XO will be a very complicated passive network with Duelund or Jantzen.

I have air press in the store. I'll make two curved parts. one with vacuum bag shaped 3/8" plywood layers and one with slices glued under pressure. I'll put both under intense press and gradually increase the pressure up to the intense levels and survey the result. I think dowel pins will play a big role here.

 

this is the press:

 

post-41711-0-09160000-1417595757_thumb.j

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further to previous post, actually it's a LS with a totally different doghouse. there is a waveguide at woofer exit. there is also a new kind of reflector (which plays a small role) there. sides are curved for less erosion and better dispersion. top section is just like LS II a separate part and it's also a curved shape to come along with the bassbin. there will be a hard anodized aluminum plate at the back of the top section for input terminals and settings. mid range horn is a hand-made Edgar style horn with fc253hz you can see the build process here. tweeter is Beyma CP-25. speaker is gonna be ~32.5" width at front and the half at rear, 41" tall and ~26" depth. I still look for your opinion about shaping layers under vacuum bag and cnc machined slices.

in case anybody is interested in details here are a few images of more than 20 pages of drawings that have been done so far:

 

 

post-41711-0-52040000-1417607072_thumb.g

 

post-41711-0-67880000-1417607090_thumb.g

Edited by Arash
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Very cool.

 

Arash, are you guys using a CNC router, or a point to point machine? I only ask because I find numerically controlled machines cool. The last one I owned was a Rover-13 point to point.

 

Cool project.

 

thanks Rick,

 

actually it's a customized (designed and made in Iran) multi-axis single spindle CNC machine that is controlled with Artcam and Mach3 software. it has an automatic tools changer with 12 section so there is no need to change anything manually it's just like a Swiss army knife. the spindle is a HSD heavy duty made in Italy, it's the only spindle that could cut BB plywood as thick as 3 inches with no problem. after all it's damn good at accuracy. the cuts are just precise. it utilizes a special linear bearing and ball-screw for least tolerance. we use a 43 sq feet/minute vacuum pump for suction. I don't know much about Point to point machines but the router we use is a continuous routing machine that can change change X,Y,Z axises at the same time according to the given G-code thus is able to engrave complicated shapes. once we tried to shape a elliptical tractrix horn into MDF with a bullnose and the result was fantastic. even there were no need for a sanding!

 

post-41711-0-15560000-1417641113_thumb.j

post-41711-0-62080000-1417641222_thumb.jpost-41711-0-72600000-1417641244_thumb.j

 

 

 

Edited by Arash
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This is an exciting build! 

 

I wonder about the metal pins... that would make me a bit nervous but maybe if they were either removed or very firmly epoxied to become one with the cabinet.  

Just a thought... Once you have the bins built I'd suggest experimenting with tweeter placement before you build your permanent top cabinets.  You may have already tested this in other builds though.  I found a little better sound stage and imaging with the speakers in vertical alignment.  One thing about placing the tweeter to the outside you might be improving your time alignment a little bit (depending on your toe-in).  

 

 Keep sharing your progress.

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Very cool.

 

Arash, are you guys using a CNC router, or a point to point machine? I only ask because I find numerically controlled machines cool. The last one I owned was a Rover-13 point to point.

 

Cool project.

 

thanks Rick,

 

actually it's a customized (designed and made in Iran) multi-axis single spindle CNC machine that is controlled with Artcam and Mach3 software. it has an automatic tools changer with 12 section so there is no need to change anything manually it's just like a Swiss army knife. the spindle is a HSD heavy duty made in Italy, it's the only spindle that could cut BB plywood as thick as 3 inches with no problem. after all it's damn good at accuracy. the cuts are just precise. it utilizes a special linear bearing and ball-screw for least tolerance. we use a 43 sq feet/minute vacuum pump for suction. I don't know much about Point to point machines but the router we use is a continuous routing machine that can change change X,Y,Z axises at the same time according to the given G-code thus is able to engrave complicated shapes. once we tried to shape a elliptical tractrix horn into MDF with a bullnose and the result was fantastic. even there were no need for a sanding!

 

attachicon.gif8a2113e947dfae4f23dd15e0bcd391a6024bf50439d0a8fd51fbef9a0caca922.jpg

attachicon.gif00f3a647ecfda076e5f4f468078eae6e7da106528e63f0411da1db5c32db5578.jpgattachicon.gif752432e5af6ad5a48e1fdae2bd456bdcd2ee4b443600bd3affdf2d8a7594551d.jpg

 

 

Very nice. What you describe is what is known to me as a point to point. 3 axis, with tool changer. My 13 had a ceramic bearing router, 5 head gang drill and a grooving saw.

 

With such a rig you can create whatever your programing skills will allow.

 

Have fun, my friend. ;)

 

Rick

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Arash!  Very very impressive!

 

I'm dying to see this all put together!

 

 

thanks man!

so do I :rolleyes:

This is an exciting build! 

 

I wonder about the metal pins... that would make me a bit nervous but maybe if they were either removed or very firmly epoxied to become one with the cabinet.  

Just a thought... Once you have the bins built I'd suggest experimenting with tweeter placement before you build your permanent top cabinets.  You may have already tested this in other builds though.  I found a little better sound stage and imaging with the speakers in vertical alignment.  One thing about placing the tweeter to the outside you might be improving your time alignment a little bit (depending on your toe-in).  

 

 Keep sharing your progress.

 

thanks

pins are cobalt-steel and no worry about rusting but the urethane glue will do the job. whole slices and pins will be glued tightly

I'll test the tweeter the way to told

I think I should submit a dedicated thread to this project.

 

 

Very cool.

 

Arash, are you guys using a CNC router, or a point to point machine? I only ask because I find numerically controlled machines cool. The last one I owned was a Rover-13 point to point.

 

Cool project.

 

thanks Rick,

 

actually it's a customized (designed and made in Iran) multi-axis single spindle CNC machine that is controlled with Artcam and Mach3 software. it has an automatic tools changer with 12 section so there is no need to change anything manually it's just like a Swiss army knife. the spindle is a HSD heavy duty made in Italy, it's the only spindle that could cut BB plywood as thick as 3 inches with no problem. after all it's damn good at accuracy. the cuts are just precise. it utilizes a special linear bearing and ball-screw for least tolerance. we use a 43 sq feet/minute vacuum pump for suction. I don't know much about Point to point machines but the router we use is a continuous routing machine that can change change X,Y,Z axises at the same time according to the given G-code thus is able to engrave complicated shapes. once we tried to shape a elliptical tractrix horn into MDF with a bullnose and the result was fantastic. even there were no need for a sanding!

 

attachicon.gif8a2113e947dfae4f23dd15e0bcd391a6024bf50439d0a8fd51fbef9a0caca922.jpg

attachicon.gif00f3a647ecfda076e5f4f468078eae6e7da106528e63f0411da1db5c32db5578.jpgattachicon.gif752432e5af6ad5a48e1fdae2bd456bdcd2ee4b443600bd3affdf2d8a7594551d.jpg

 

 

Very nice. What you describe is what is known to me as a point to point. 3 axis, with tool changer. My 13 had a ceramic bearing router, 5 head gang drill and a grooving saw.

 

With such a rig you can create whatever your programing skills will allow.

 

Have fun, my friend. ;)

 

Rick

 

 

I'm working on the 3D designing.

I appreciate you. I wish you the best

thanks,

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Arash, it seems it's going to be a wonderful speaker. You have good tools and you know how to use them. I suggest you not to put the tweeter by the midrange! I have lived with both. I had the same midrange horn with bms driver and a beyma tweeter. I heard them on the side and then on top aligned. I had both ways for more than a few months. Me and all my friends preferred them on top aligned. I have tried it with blind tests as well and preferred them on top all the time. 

 

Make some blind tests yourself. Please do try. It seems its going to be a wonderful speaker, don't compromise :)

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Awesome, cant wait to see the outcome.

 

 thanks :)

Arash, it seems it's going to be a wonderful speaker. You have good tools and you know how to use them. I suggest you not to put the tweeter by the midrange! I have lived with both. I had the same midrange horn with bms driver and a beyma tweeter. I heard them on the side and then on top aligned. I had both ways for more than a few months. Me and all my friends preferred them on top aligned. I have tried it with blind tests as well and preferred them on top all the time. 

 

Make some blind tests yourself. Please do try. It seems its going to be a wonderful speaker, don't compromise :)

 

I've thought of that but there is a problem. CP-25 vertical dispersion angle is 30 degree if I'm not mistaken. If I want to place the tweeter on top of speaker in level with mid-range, I should make a stand about 10" tall in order to prevent high frequency to hit the top surface of the speaker. I don't know if this concern is right or not.

I may also build the speaker with two tweeters! one side by side of midrange inside the cabinet and one in a separate box to put on the speaker and connect it to the back with a cable and there will be a selection switch back there.

 

post-41711-0-83040000-1417788589_thumb.g

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I've thought of that but there is a problem. CP-25 vertical dispersion angle is 30 degree if I'm not mistaken. If I want to place the tweeter on top of speaker in level with mid-range, I should make a stand about 10" tall in order to prevent high frequency to hit the top surface of the speaker. I don't know if this concern is right or not.

I may also build the speaker with two tweeters! one side by side of midrange inside the cabinet and one in a separate box to put on the speaker and connect it to the back with a cable and there will be a selection switch back there.

 

attachicon.gifalignment.gif

 

 

 

I think your concern is valid but I would want to test with my ears.  I have the same drivers in my setup vertically aligned like you are showing but the mid point of the drivers are exactly 9.5 inches apart.  I installed the CP-25 on a temporary motorboard that I was going to use to move the tweeter up in small increments and listen for changes or improvements.  I haven't moved from the original spot yet but I have placed a couple of layers of felt across the top of the Eliptrac 400 midhorn. Both horns are too high from where I sit so I'm not going to mess with the tweeter placement relative to the midhorn until I get the whole thing lower.  The height of the midhorn obviously affects the angle of the tweeter to your head.

 

I have these sitting on top of my LaScalas currently.  I tried turning the LaScalas on their side but that placed horns too low.  I'm building some new bass bins and will see about getting the height correct with those installed in the next month or so.  I have a suspicion that my height selection might come back very close to where PWK chose. 

 

post-36269-0-92240000-1417797950_thumb.j

 

I should add that as far as vertical alignment... I tried to align the diaphragms vertically.  Here's a cross section of the 4590 which might be similar to the 4592:

 

post-36269-0-41960000-1417799054.jpg

 

Here's a 4592:

post-36269-0-69720000-1417800109_thumb.j

 

Edited by muel
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Given all the fuss, have you considered making this a two way speaker? There are many here who think it is superior to a 3way design. There are lots of KPT-904's and Jubes out there that are 2 way!

 

If not, perhaps an efficient supertweeter or ribbon tweeter crossed very high just to hit those frequencies only 3 year olds can hear.

 

edit: I know you have gone to a ton of trouble designing this speaker, and since you have both the coax and midrange version of that driver, you have already considered this option. I assume it is the capability of the Tractrix horn you built that is stopping you. IMO, a blind test and a sweep test comparing the coax in that horn with a triax with the two separate horns would be a good way to go if you haven't already done it.

Edited by mustang guy
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I was also concerned about the height of the tweeter. I tried it in 3 different positions for about 2 months each! First I put the tweeter high enough so the vertical dispersion would not hit on top of the tophats. Although it was sounding good, this was a little too high. It was like listening to a concert from up close but the stage is high so you are listening from below. We could also distinguish sounds coming from the mids or tweeters which is not good.


tweeter on top! time alignment baby


 


Then I put them 10cm's lower. The vertical dispersion angle showed that now there will be some, if very little of the high frequencies hitting the top of the tophats. I heard no artifacts, but tweeters coming lower sounded in a better soundstage, still a little high but more cohesive.


 


Then I put them even lower and listen. It sounded much better and I could hardly hear any problems because of vertical dispersion. I always like basstraps on top khorns. It always help with the overall sound, making everything sounding better in my setup. So I cut into it a place for tweeter and keep it on top. Now the high frequencies travelling downwards would be hitting this panel first. We made blind tests with and without them basstrap. We decided this was the way to go. I don't know if this helps but at the end this setup was sounding much better than having tweeters. To be sure, we then put the tweeters back again to mids side and listened to extensively. Then put them back again on top with the basstrap. For me it was a big difference and in a positive way. So I will keep it like this. 


new alignment


 

I don't know, food for thought. I wish you end up with the best possible scenario!

 


Next thing is changing the tweeter to Fostex t500amkII :)


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