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Tannoy cabinet thoughts: Onken?

Tony L

Tony L

Administrator
I suspect the time is approaching to give some very serious thought to some better cabinets for my 15" Monitor Golds.

The safe route is just to commission a really nice and solidly engineered and finished York clone as I have a pair built to original spec at present and they do work fairly well in the room despite being a bit muddy and lacking in mid-band clarity (known issues with original spec Yorks as the baffle board is way, way too thin and resonant for the job in hand and the port math not quite right). Mine are built very precisely to the original York plans with the same (far too thin) panels etc. Lockwood Majors are a very similar thing so influences can be taken there too. I'd actually be tempted to buy a real pair if a really nice clean pair without drivers popped up. I'd like corner Yorks too, but I suspect they'd be crazy expensive to commission.

I think I'm pretty sure R-GRFs are not for me. Certainly whenever I've heard them I've felt the bass remarkably uneven, I don't think they'd work in my room either. Too much of a risk anyway.

Infinite baffles are an option as I very much liked my first pair in their crazily over-engineered corner cabs that were close in volume to corner Lancs but about 5 times heavier! They had great tight and agile bass even if not the last word in extension and better mid clarity than the flimsy York clones I currently have if not the ease/scale.

An outsider, but one I'm really interested in, is an Onken cab. These are more often used with Altecs etc, but I see no reason why they'd not be a good option with Tannoys and I love the looks. See post 6 of this AudioHeritage thread.

Whatever I decide on will need to be built professionally as I do not have the skills and it will need to be done to a very high standard too, so I'm also looking at options there too. I definitely want a traditional looking well-finished (veneered or really nicely finished plywood) wide-baffle speaker with a grill.

Any ideas? I'm not going to rush this, the thinking may take a year or so!
 
I've always wondered what my Tannoys would sound like in big simple rectangular cabinets made out of concrete. Whether it would sound less coloured, and what the build cost would be vs a really over-engineered wooden box? I'm in the same boat as you with respect to needing the cabs built by a professional hand.
 
There is a genius-grade corner design in Gilbert Briggs' 'Loudspeakers' book where you use the brick walls and floor as the back/bottom of the cab and just build the baffle and top!

17872496921_12dbcaff4c_b.jpg


I'd build them in a shot if my room layout was compatible and didn't have neighnours on the other side of the wall!
 
Tony L said:
I'd build them in a shot if my room layout was compatible
Click to expand...

+1. In my case life would be so much easier if the door into my room was located in the middle of the wall instead of near the corner, and even better if it opened outwards into the hallway instead of inwards into the room!
 
I've just altered the thread title slightly as I'm really interested as to whether anyone has built, heard or even thought about the math of an Onken cab for a 15" Monitor Gold. I do like the look of these things as a) they look damn cool, and b) the port/vent 'Q' has to be exceptionally low. In many ways they look logically more like a kind of constrained open-baffle than a conventional port loaded speaker. That appeals as I'm really not a fan of ports at all and have often prefered the sound of my Yorks with the 'back door' slightly open (that may be a panel resonance thing though). I'd take speed, openness and agility over sheer extension any day and I'm curious if that is what Onkens may bring. Here's a site with a bit more info and plans of the internal structure, but it's not Tannoy related: www.audiodesignguide.com/HiEff/HiEff.html

PS This may actually not be too far away from what Tannoy themselves are thinking with modern Canterburys, Kensingtons, Turnberrys etc.
 
IIRC (it's a long time since I looked into the concept) Onken is a variation of the bass reflex enclosure. The idea is to have a large port area (essentially the same area as the cone) to equalise room excitation between direct sound and port sound (same area = same velocity and thus more or less identical acoustic impedance in both operating modes of the BR cabinet). It works, but I'm not convinced it's actually better than a well-executed conventional BR cab. I note that after lots of experimentation, the standard cabinet recommended by TAD for their 1601 series of drivers is "normal" BR.

Onken cabinets also get very heavy very quickly, due to the large internal side partitions which effectively double the weight of your side walls (but should lead to reduced side wall radiation).

With your Tannoys, I'd model a clean .5 Q front- or side-vented BR cab (the best location for the BR vent is close to the bass driver on a side wall) and go from there.
 
Hi Tony ,

As Markus says Onken cabs are really multi ported cabs , check out the Planet 10 website it's geared around Fostex Onkens but will give you an idea of the port arrangement .

I've heard Fostex Onkens and the cab design really does enhance the LF , I would be wary of getting too much bass with a big Tannoy driver .

Have you thought about aperiodic enclosures ? . I tried it with my Chatsworths and it sounded very promising , there should be loads of scope to tune the bass with differing resistive loads .
 
Thanks for the feedback so far. As for aperiodic if I do end up going down some York/Lockwood Major type route when done right these are kind of aperiodic - the cabinet is braced/split mid-way and if done properly (which not all proper Yorks are, and neither are mine) there is a kind of 'tray' with slots in it covered in felt that kind of impedes air-flow between the upper section of the cab and lower ported area. The nearest I've tried to this with mine is to stuff a pillow in there, but that's too much, it removes too much bass. I suspect with this aspect of the York design properly implemented bass would be a lot better. There is also a school of thought that suggests the York's bass port is simply wrong. This aspect is beyond my skillset at the moment, once I've arrived at a basic cabinet design concept I'm happy with I'll unleash a mathematician or two, should there be any lurking here.

Do I take it that the Onken cabinet design might have even more bass than the York? I assumed being so open and having such a huge port area it would actually have less and behave a little more like an open baffle. That, aside from the looks, was the attraction.
 
I think cabinet rigidity is king if you want to hear what Tannoys (or any other large driver eg Altecs, JBL) can do.

I have some Butyl surround 12" golds in some 250 ltr cabs which I took extraordinary pains with to deaden and make rigid - shelves, braces, and finally casting plaster of paris on each interior surface (after sealing the wood with bitumen to stop water penetration and dusting with sand while the bitumen was wet in order to give the plaster something to grip). There is virtually no cabinet talk. The ports were telescopic, and I adjusted them by ear, in room. I have Decca ribbons as supertweeters and use a pair of Silver crossovers so the bass cone is driven full range.

I have and have heard various other classic Tannoy designs - Autos, Lockwoods* Lancasters, Berkleys and corner GRFs and although this might sound like the ravings of the home speaker builder, none are close. I'm a good few years down the line with these speakers, so no bias from fresh pride of ownership here. Very open, very dynamic, bass goes extremely low and has excellent texture - air beneath the notes, indeed. I also rate the butyl surround 12" gold as the best sounding Tannoy 12", better than silvers or reds, particularly in this implementation.

I'd be very interested in the concrete cabs idea. Indeed am considering making concrete cabs for Urei 813Cs...if I didn't like them I could always live in them!

I must admit, on purely visual evidence, the Onken look like there would be significant sonic radiation from the cab They're not very thick and neither are they braced well. I'd postpone any decision until you'd heard what Tannoys can do mounted in a dead and rigid enclosure. Just my twopennoth...



*Well...maybe...maybe Lockwoods. But different.
 
Any chance of posting some pics of your cabs so I can see what wall thickness and bracing techniques you have used?

If the Onken is a non-starter I'm pretty certain I'll end up with some over-engineered take on the York conceptually, but that still leaves a lot of construction detail to define. There are various problems I want to think about, not least of which being rigidity. I also need to decide how to mount the drivers and that's not as simple as it first seems e.g. front-mounting is best, but they must have grilles - I do not want the driver exposed as a) it looks naff IMO, and b) I don't want the cone to fade any further than it has. Then do I have a back door or not, and if so is it full height or just behind the driver. If I go for an aperiodic loading 'shelf' in the manner of some Yorks and Lockwoods then it would certainly be advantageous to be able to get at it to adjust without having to take the drivers out! Lots to think about.

PS If you think those Onkens look lightweight you should see my Yorks! The front baffle is just 1cm thick (or whatever that is in inches anyway)! That's a panel the size of a wardrobe door holding one of the largest and heaviest loudspeaker drivers eve made! It is *exactly* to the original Tannoy spec!
 
Tony, the first thing I would do is getting your drivers measured. I'm sure Rob will help you with that. You really need the T/S parameters to take the guesswork out of your cabinet plans.
 
Sorry no pics....I can remove the port assembly, but because of the baf wadding substitute(argos' s cheapest duvets) theres not a lot to be seen.

I'll tell you what I can though.

Thee cabs are 23mm birch ply. The front baffle is double thickness. They had two internal shelves with cut outs of the same material. When I glued them together initially I was disappointed how resonant they still were. Working through the driver hole I cross braced with three by two between any panels which resonated when rapped. I remember a lot of braces. I also made and glued in a four by four brace from the rear panel for the rear on the driver to brace against with blu tack. The plaster thickness I would put around 30 mm. I also installed a chassis earth on the driver and connected that to the house earth. Crossover is external and connection at the rear of the cab is a four pole speakon - great design, contacts are wiped every time you plug in.

If you like the aesthetic of the corner York you could apply much the same processes as I did, to great effect I'm sure - few parallel surfaces is a big plus I think. Maybe scale up the cabinet to allow for the thicker walls but keep the same internal volume. Mind if you mount the driver from within you cant brace the rear.
 
Tony L said:
Any chance of posting some pics of your cabs so I can see what wall thickness and bracing techniques you have used?

If the Onken is a non-starter I'm pretty certain I'll end up with some over-engineered take on the York conceptually, but that still leaves a lot of construction detail to define. There are various problems I want to think about, not least of which being rigidity. I also need to decide how to mount the drivers and that's not as simple as it first seems e.g. front-mounting is best, but they must have grilles - I do not want the driver exposed as a) it looks naff IMO, and b) I don't want the cone to fade any further than it has. Then do I have a back door or not, and if so is it full height or just behind the driver. If I go for an aperiodic loading 'shelf' in the manner of some Yorks and Lockwoods then it would certainly be advantageous to be able to get at it to adjust without having to take the drivers out! Lots to think about.

PS If you think those Onkens look lightweight you should see my Yorks! The front baffle is just 1cm thick (or whatever that is in inches anyway)! That's a panel the size of a wardrobe door holding one of the largest and heaviest loudspeaker drivers eve made! It is *exactly* to the original Tannoy spec!
Click to expand...

One centimeter is .39 inches, that's pretty thin. Most plywood comes in 1/2, 5/8, 3/4 inch.

So for reference your Tannoy's have 10mm thick cabinets.

The DMT 15 and 215 cabinets are 36mm front/back and 20.6mm top/bottom/sides. It also has an energy absorbing bracing matrix that the back of the driver rests against.
 
ff1d1l said:
I think cabinet rigidity is king if you want to hear what Tannoys (or any other large driver eg Altecs, JBL) can do.

I have some Butyl surround 12" golds in some 250 ltr cabs which I took extraordinary pains with to deaden and make rigid - shelves, braces, and finally casting plaster of paris on each interior surface (after sealing the wood with bitumen to stop water penetration and dusting with sand while the bitumen was wet in order to give the plaster something to grip). There is virtually no cabinet talk. The ports were telescopic, and I adjusted them by ear, in room. I have Decca ribbons as supertweeters and use a pair of Silver crossovers so the bass cone is driven full range.

I have and have heard various other classic Tannoy designs - Autos, Lockwoods* Lancasters, Berkleys and corner GRFs and although this might sound like the ravings of the home speaker builder, none are close. I'm a good few years down the line with these speakers, so no bias from fresh pride of ownership here. Very open, very dynamic, bass goes extremely low and has excellent texture - air beneath the notes, indeed. I also rate the butyl surround 12" gold as the best sounding Tannoy 12", better than silvers or reds, particularly in this implementation.

I'd be very interested in the concrete cabs idea. Indeed am considering making concrete cabs for Urei 813Cs...if I didn't like them I could always live in them!

I must admit, on purely visual evidence, the Onken look like there would be significant sonic radiation from the cab They're not very thick and neither are they braced well. I'd postpone any decision until you'd heard what Tannoys can do mounted in a dead and rigid enclosure. Just my twopennoth...



*Well...maybe...maybe Lockwoods. But different.
Click to expand...

Quite true.

I've designed and built a fair few cabinets for Tannoy speakers now, and they do have to be very rigid and very well damped to get the best from the Tannoy drivers. That and decent crossovers transforms vintage Tannoys into Prestige series beaters, no contest.
 
John said:
One centimeter is .39 inches, that's pretty thin. Most plywood comes in 1/2, 5/8, 3/4.

So for reference your Tannoy's have 10mm thick cabinets.

The DMT 15 and 215 cabinets are 36mm front/back and 20.6mm top/bottom/sides. It also has an energy absorbing bracing matrix that the back of the driver rests against.
Click to expand...

Just measured: 12mm baffle boards, the cabinet sides are a fair bit thicker. As I say they are very exactly built DIY York cabinets, so the baffle, walls etc are the same as any real York (or I assume Lancaster). I remember comparing them to the original Tannoy plans when I bought them and whilst the finish is very rudimentary they are very precisely done so should certainly sound like Yorks should. This is just how Tannoy built cabs at the time. My first pair in the corner cabs were very, very much better built with cabinet walls about an inch and a half thick, heavily braced and even featured a fair bit of metal in their construction. I've only ever considered that I have a box to keep my drivers in until I eventually get a better pair of cabs built. That has always been the plan. The good thing is I have a very good clean pair of drivers that seem very well pair-matched, plus in real terms I paid peanuts for them (effectively nothing, see my original Tannoy thread as whilst I sold the first pair I bought back at the same price) so spending a bit in cabs is doable without losing any money on the overall investment.
 
It's a wise decision Tony to go heavy and rigid with Tannoy cabs as the enemy of all DC drivers is resonant cabinets. Not much produced by the factory was very good in that respect, with the worst offenders being cabs like the Lancasters.

All of my Tannoy cabinets built for customers have used between 36mm and 50mm layered ply front baffles (and bases) and 18mm sides and backs but with heavy internal bracing. Very heavy and very rigid. It makes a big difference for the better providing of course that the cabinet sizing and tuning have been correctly done.
 
I'd not actually, and I even searched for 'Onken calculator'! I now need to find all the parameters for the 15" Monitor Gold...

Has anyone here actually heard an Onken in comparison to anything else? I'm very curious as to what the character traits are, e.g. lean and tight, slow with great gobs of bass - does it have a stereotype at all?

I really like the looks of the things and reckon with a bit of creative license I could create something pretty stunning in a 'mid century modernist' sort of style by just setting the baffle back a little (maybe giving just the baffle a slope back of a few degrees to compensate for the driver being a little low) and having a grille that covered the baffle but not the ports. Dark veneer, exposed ply edges, wheat grille. Job done!
 
Tony L said:
I now need to find all the parameters for the 15" Monitor Gold...
Click to expand...
Never ever trust the published parameters for historic drivers, get your specific samples measured!

Onken bass, correctly executed, is the opposite of slow and gobs of bass, it sounds light (as in light on its feet, not lightweight) and fast. But it may take a while to get right. The usual recommendations are to get the vent surface to between 80-100% of Sd (the closer to 100% the better), and to apply a correction factor to the port length thrown up by traditional BR calculators because the vents go back to almost the back of the cabinets, so part of the back wall efectively acts as vent as well. 80-85% of calculated length should be about right.

My personal preference is for a fairly low-Q BR alignment, .5, but depending on taste you can go a little higher.

More Onken pictures here: http://www.re-speakers.de/front_content.php?idcat=15
 
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