MY own OB speaker project

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Nick
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#16 Re: MY own OB speaker project

Post by Nick »

I'm not sure these will be added to the Reiver Acoustics range as really the DIY ply bases and side frames really need to be professionally CNC laser cut from sheet aluminium and then professionally powder coated. My initial investigations suggest these will cost in the region of £600 - £700 for the machining and then there is the added cost of the powder coating. Still depending on interest..............?
I would think they would look even better milled and anodised, but not sure about the cost of that. If you have the cad files for them I could find out if you like. You could also have the option of acrylic panels for the fronts.
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#17 Re: MY own OB speaker project

Post by Toppsy »

I like your thinking Nick. However for now lets wait and see how they sound with all drivers and the 3-way filter.
Yours, Ali's and Andrew's feedback when we have the mini meet my place next month will decide which way I go with these.
Before that I shall be inviting Scott and Chris round for feedback when I have the 3-way filter built and wired in. I'm sure the filter will need some fine tuning.

But yes if they sound as good (or better) than they look then yes I'll certainly CAD up some machining drawings for you to get prices.
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Ray P
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#18 Re: MY own OB speaker project

Post by Ray P »

I was thinking acrylic panels too, rather more practical as a DIY project than something like acrylic quasar OBs.

But, as you say, no point getting ahead of yourself with such thinking. Will be interesting to see how the development progresses and the views of the early audition panels.

Cheers

Ray
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#19 Re: MY own OB speaker project

Post by Ant »

The problem with acrylic is the machining, its a pig to machine cleanly without low speed cutters as the heat buildup melts it if too fast, and chips it if too slow so its not a great material 'just to see' with. Been there and done that
As Mark knows with his speakers, it costs alot to have the pieces machined for you, so I would be inclined to get a few quotes and see wether its viable to try while they are at the prototype stage (colins 'prototypes' are somewhat nicer than prototypes though :D)
I wouldn't like to try cutting a hole for a driver out of a large piece of acrylic tbh
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#20 Re: MY own OB speaker project

Post by Toppsy »

My own experience cutting and drilling Acrylic is similar to Ant's, so I agree these would have to be ordered and cut by a third party specialist.The material is also not cheap Though I do have to say it has a certain bling. In this instance however, I believe solid cast block is the most suitable for the 6 baffle panels. Mounting the drivers on the rear of the panels and using the clear (not solid colour) acrylic would show the screw fixings and the mounting flange of the driver with the sealing neoprene rubber sealing rings and IMO would spoil the looks and the aesthetics. This restricts the options to a few colours most notable black or white.

Out of interest I have just done a online quote for solid black 25mm thick acrylic block cut to size with polished edges. Quoted price for a single large baffle panel (540mm x 420mm) was £136.99. Quoted price for a single centre baffle (540mm x 300mm) was £97.85. These prices do not include cutting the driver hole or the driver fixing holes. To compare you can get a 2440mm x 1220mm x 25mm sheet of birch plywood for the price of a single 540mm x 420mm x 25mm acrylic panel.
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#21 Re: MY own OB speaker project

Post by Ant »

I suppose the other way would be to get the cheapest piece of acrylic you can, cut a raggy hole out with a router and trammel, ignore the nasty finish and see that way. If it looks a bugger it doesnt matter. If there is a benefit to using the material that justifies the cost, then offer the panels as an option for a customer build.
Its still unlikely to be cheap,
Another option is to try kitchen fitters who do acrylic worktops, a couple of offcuts from sink cutouts may be available. When i was working for the company who made me redundant, i did alot of design work on kitchens that used this, the material was not solid, it had a 1/2" thick acrylic face, backed with a higer densitiy particleboard to make it reasonably viable cost wise, and allowed it to be fitted with the standard jigs and routers the fitters used. Measurements had to be very very precise as the pieces were specially cut rather than cut on site, same as granite tops. We had some pieces of it on display that were there as cross sections so folks could see the construction. Was very dead is you tapped it. Not all firms will use the same stuff, but maybe worth a look 'just to see'
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#22 Re: MY own OB speaker project

Post by ed »

Hi Colin

I might be misunderstanding the explanation re the side cheeks but I couldn't see how the lengthwise angle was jointed. I understand the issues with acrylic cutting having ventured into laser cutters recently, but this alternative seemed a possibility for a diy approach:

aluminium angle embedded/routed in the side cheeks/supports.....or maybe I'm missing the point completely...
cheeks.jpg
should be very easy to attach/weld a piece at the bottom of the equal angle for attachment to the base?
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#23 Re: MY own OB speaker project

Post by IslandPink »

The 20mm thick pieces I had cut by the supplier (with CNC router) for the OB's , came out pretty nice. A rounding cutter on my router gave nice translucent rounded edges - they could be further improved by a bit of hand polishing with the right compound, I'm sure.
Maybe laser cutting isn't the way to go on this ?
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#24 Re: MY own OB speaker project

Post by Ray P »

ed wrote: Fri Oct 13, 2017 11:08 am aluminium angle embedded/routed in the side cheeks/supports.....or maybe I'm missing the point completely...

cheeks.jpg

should be very easy to attach/weld a piece at the bottom of the equal angle for attachment to the base?
Ed, that's more or less what I had in mind with my earlier post about disguising some angle bracket.

It is also possible to get 6mm thick aluminium angle that is L shaped, I've seen some that was about 150mm x 50mm so it might be possible to use the wider side for the actual support 'cheek' - not sure of the depth of Colin's sife cheeks so maybe that section wouldn't be big enough. If so, with something like a metalworking band saw and some elbow grease it is probably possible to DIY the four support sections.

https://www.metals4u.co.uk/aluminium/c1 ... x14)/p3028

Mark, isn't flame polishing the way to go with finishing Acrylic?

Ray
Last edited by Ray P on Fri Oct 13, 2017 2:09 pm, edited 1 time in total.
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#25 Re: MY own OB speaker project

Post by Toppsy »

ed wrote: Fri Oct 13, 2017 11:08 am Hi Colin

I might be misunderstanding the explanation re the side cheeks but I couldn't see how the lengthwise angle was jointed. I understand the issues with acrylic cutting having ventured into laser cutters recently, but this alternative seemed a possibility for a diy approach:

aluminium angle embedded/routed in the side cheeks/supports.....or maybe I'm missing the point completely...

cheeks.jpg

should be very easy to attach/weld a piece at the bottom of the equal angle for attachment to the base?
Ed,
I have enlarged a part of the photo that showed the side frames that should make things a little clearer?

Image

In my prototypes I have simply butt jointed (90-deg) the 40mm wide strips to the side frames using wood glue and size '0' biscuit joints. All from 9mm sheet birch ply.

If I was to have these professionally manufactured the options to me would be to have them CNC machined (either laser cut, water jet cut, milled, etc. whichever was the most cost effective from say 5mm/6mm sheet steel or aluminium. The 40mm mounting strips could either be bent on a bending press and made as part of the CNC machined exploded view side frames or made as separate strips and seam welded/fillet welded on the inside to the main sides. I have a local company that can offer all CNC cutting options as well as welding and bending options. The bases just need to be either CNC milled or laser cut to shape. Both these options I reckon would give a cleaner looking final product.

The problem I see with your recessed angle option is that the side frames would have to be machined from thicker material to accommodate the recess angle strips. However, thanks for the suggestion. It'll go into the thinking pot with all the other suggested options when (and if\) I decide these may be a commercially viable speaker for me to invest have the various parts made externally.
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#26 Re: MY own OB speaker project

Post by Ray P »

If the front mounting strip is 40mm wide then the pictures suggest the depth of the side 'cheeks' is more than 150mm so the aluminium angle I mentioned won't be deep enough. Ah well...
Toppsy wrote: Fri Oct 13, 2017 1:47 pm The problem I see with your recessed angle option is that the side frames would have to be machined from thicker material to accommodate the recess angle strips.
Is this a problem other than for the aesthetics?
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#27 Re: MY own OB speaker project

Post by Toppsy »

Ray P wrote: Fri Oct 13, 2017 2:15 pm
Toppsy wrote: Fri Oct 13, 2017 1:47 pm The problem I see with your recessed angle option is that the side frames would have to be machined from thicker material to accommodate the recess angle strips.
Is this a problem other than for the aesthetics?
Ray,
it's not a problem for a DIY solution as the angles can be glued/riveted or bolted to the sides but for commercial speaker that would perhaps retail for around £2K I think so.
As built the side frames are 210 mm wide at the base. For (any) future builds I would probably make the mounting flanges 50mm wide rather than the as built 40mm and use M8 furniture fixing bolts rather than the M6 I have used.

The baffles are an integral structural part of the whole speakers and add greatly to the overall stability of the whole frames and so I would not suggest using anything thinner than 25mm, be it Acrylic, MDF, Plywood or other material.
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#28 Re: MY own OB speaker project

Post by Toppsy »

The Transformer core inductors finally arrived from Germany earlier in the week Image

I have just finished the 3-way XO'ers temporary lash-ups for testing purposes for when Scott and Chris come over this afternoon. Should be an interesting tweaking of the filters session. To add to the mix I have also the 2-way modified XO that Scott designed for the Coax drivers as standalone speakers that on the baffles and without any added bass help do sound rather good but as one would expect lack bottom end extension but nevertheless are an engaging listen.

As an aside earlier in the week I did try the twin 15" drivers driven direct with no filter and they are surprisingly good. The spec sheet states the FR for these drivers is F3-4000Hz and I don't doubt this listening to the drivers alone. This suggests to me that they will work rather well in a 2-way configuration replacing the 2-way coax driver with a horn loaded compression driver. Depending how this 3-way configuration set-up works out I reckon this could be worth further experimentation. I have in mind a rather nice Monacor 1.4" compression driver (MRD-300) that when coupled with their MRH-300 mid-high range horn has the capability of a 1kHz - 20kHz FR and the driver a recommended minimum XO of 1.2kHz. This however, will require a slightly larger central baffle to accommodate the horn, so a complete new speaker build.

I'll report back later our initial listening findings and any fine tuning mods.
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#29 Re: MY own OB speaker project

Post by Ray P »

Interesting. We await the verdict of the Lancashire jury...
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#30 Re: MY own OB speaker project

Post by The Stratmangler »

It was a very fruitful afternoon, and Scott's input was invaluable.
The elements for a really good speaker were already in place, it's just that the various elements weren't quite gelling.
A bit of alchemy happened, and base metal became gold.
It could have gone the other way, and we'd have created purest green, but thankfully it wasn't the case.

Various bits of music were played, basically trying to trip the speakers up, and we didn't once have cause to wince.
Eventually the "torture track" (Metallica - S&M - Nothing Else Matters) was retrieved from its hiding place, and for once I actually enjoyed it.
As far as I'm concerned that counts as a result.

If they weren't so big I'd be after a pair ... :lol:
Chris :happy3:
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