A different dimension rect. Tannoy GRF for Reds

[Magna Audio]

I've been building a different dimension rect. GRF for that narrower room space...

First I used Hornresp to model the back loaded horn section and get the volume / baffle (throat and mouth sizes right). Once suitably conforming with the orginal shape rect. Tannoy model it was time to cut wood. 21mm Scandi birch ply throughout of course.

These are exactly the same volume at the others but are 45cm wide, 125cm tall and deeper by a bit.

Here's some pics
Basic plan


Cut out - The front baffle really is the narrowest you can go...


Under construction


First cab up


Recessed removable backs - allow access to crossover / tuning of the folded horn damping if needed. 24 screws fixing and gasket so no risk of resonance.


Part finished - few more spray coats to go.


In the room under test with HPD's loaded


Brass panhead bolts or caphead?



Full length vintage cloth grilles





Geniune NOS Tannoy Reds badges




Under listening tests with the Reds loaded and using a little 5W SET EL84 amp the sound easily filled my large lounge diner with great full Tannoy sound.
The modelling worked - they sound just the same as the other Rect 21mm birch ply Tannoy cabs I have heard.

I'm very happy with the resulting look / sound. Enjoyable project.

[tannoy man]

A fantastic job

[Welder]

Hello Steve.

They look excellent
Looking at the finish you’ve achieved with the bare ply has made me feel a bit ashamed of the impatient, well its what they sound like not what they look like, approach I have to my builds. So much so in fact that I think I’m going to make the effort and do something to make my Volts look a little less like something that got dragged out of some studio and went on the road as a PA setup.

Part of my reluctance to spend time and effort on finish is I have quite large radii on my enclosures and apart from the cost of say veneering, there is also the difficulty in bending without steaming and getting a robust and easily repairable finish at a reasonable cost.

So, if you wouldn’t mind sharing, how did you go about finishing the enclosures, stain/varnish/number of coats, method?

[Spur07]

lovely job Steve, loving the cherry red finish - a true work of art.

I recently built some OB's and p*ssed about with various wood stain finishes only to end up painting it gloss white!

[DSJR]

They look beautiful for such a large enclosure. Hope they sound as good as they look..

[aquapiranha]

Hi Steve, I have been waiting for you to let us know about these since you mentioned them a while ago. I personally think they look better than the standard wide version and would go for this design myself. Now that you have confirmed the sound is the same, I would definitely build them myself. Thanks for taking the time to post up the design and pictures - do you have the plans?

Steve

[Magna Audio]

Thanks guys - always fun to try something different and nice that the hornresp modelling hold true in reality of listening tests.

[Magna Audio]

1. Sand down to remove all the cross grain cuts / make end grain / edges smooth and even.
2. Condition the plywood with a mix of shellac sanding sealer and industrial alcohol. This soaks in but leaves a level of sealing that prevents subsequent stain from soaking in unevenly.
3. For these cabs I sprayed the water based stain on (I have a nice compressor and paint spray gun) -use a proper filter mask.
4. Apply many coats of clear water based varnish - polish a bit but not too much.

I have also had good results spraying water based coloured varnish directly onto the conditioned wood too. I will be finishing my 5 way horn project birch ply 12 sided conicals / tapped horns that way.

They currently look like this


but first I am going to make a tubular metal stand / support for the upper and mid horns and get rid of the lash up stands I made in 0.5hr to test them... It will be one rear vertical that you won't see and two or three horizontals that the horns will hang off.
Base will be on pads or 4 castors so they can be moved.
1 or 1.5" tube should do it - bit of angle grinding and welding to boot.


There you go.

Hello Steve.

They look excellent
Looking at the finish you’ve achieved with the bare ply has made me feel a bit ashamed of the impatient, well its what they sound like not what they look like, approach I have to my builds. So much so in fact that I think I’m going to make the effort and do something to make my Volts look a little less like something that got dragged out of some studio and went on the road as a PA setup.

Part of my reluctance to spend time and effort on finish is I have quite large radii on my enclosures and apart from the cost of say veneering, there is also the difficulty in bending without steaming and getting a robust and easily repairable finish at a reasonable cost.

So, if you wouldn’t mind sharing, how did you go about finishing the enclosures, stain/varnish/number of coats, method?

[daveskis]

Great work Steve, inspiring me to finish mine.

If only I could get that Tasmanian Blackwood for the trim delivered!!!

[Welder]

Thanks Steve
I’ve had some horrendous results trying to finish ply in the past.
Spraying equipment must help. Its been the sealing stage that has given me the most grief.
I’ll give your shellac and alcohol sealing mix a go; proportions (?) if I’m not pushing my luck please