DIY Speaker Cabs for Tannoy DCs - Advice Wanted

Hi All,

I have a pair of Tannoy DC200s which I'm currently using in my second system and which I rather like.

The thing is I strongly suspect that the cabinets are what's holding them back (plus they sure is ugly). The current cabs are stand mounters, seem to be made of chipboard, with a single port and a volume of 33 litres. I'm toying with the idea of building (with a friend who is a cabinet maker), some new cabinets and re using the drivers. The drivers are 10" Tannoy Dual Concentrics.

I confess at this point that I know next to nothing about speaker design, which is why I was hoping you chaps might be able to help here. Size (within reason) isn't an issue here. I was hoping for something which would improve the quality of the bass, which with the current cabs tend to be a bit one note. I know there are various design choices here but really don't know which would be best.

The only info I've been able to find about the DC200 is here:



And some pics:



Any advice would be appreciated

 

Speaker cabs

Hi look up about transmission line speakers.

Wilmslow audio or Williams hart may be able to heklp you with cabinet designs provided you have some detail on the driver specs.

IPL may be able to help - his cabinaets are easy to build - I ahve jsut built the S4tls using the recomended approach and the cabs are heavy and strong.

Hope that helps.

 

Id go for a large sealed box myself. This is certainly the easiest. Plus the later tannoy duals perform well in a sealed box. And you wont get one note bass.

 

Some useful links...

http://www.quarter-wave.com/Theory/TL_Theory.html

http://www.users.bigpond.com/tunnelgap/Tannoy/tannoy1.html

 

A large sealed or front ported box is what you want with these. The larger you can make it the better IME. The best Tannoy dual concentrics are *very* large.

 

Sorry Joel, pure bollocks

See here for closed box design equations:

http://www.mhsoft.nl/Closedsystem_en.asp

 

And... this proves that speaker design is quite involved.
From my experience, the best Tannoys speakers are very large and front ported (more like slots, really). Smaller Tannoys (or other point-source speakers such as the awesome Altec 612) sound less good the smaller the cabinet (and the drivers, it is true) get.
Have you listened to music through a pair of GRF Autographs?

 

More food for thought:

http://geocities.com/rbrines1/Pages/Non-Resonant_Pipes.html

Making the box bigger can make the sound worse. It all depends on the driver parameters - which in this case are unknown. I haven't been able to find any for the DC200 driver. You could try emailing Tannoy and asking for them.

 

Tannoy are not usually terribly forthcoming with TS parameters. I still think you should go for a sealed box. You could knock together a quick box and adjust the internal volume to see what sort of volume gives your preferred sound.

 

FWIW, I contacted Tannoy and Lockwood Audio a few years ago about my SRM10B monitors. I too wanted to know if putting them in larger cabinets will improve the sound. I was told by both that it's not an easy yes or no type question.

TB beat me to posting the link to Big Pond. Curses :grrr: There is also a Tannoy user group on yahoo.com. I'd try posting the question there.

 

I'd be tempted to pair them with a second 10" bass driver in each cabinet.

Why dont you give the cones to a speaker maker like wilmslow or whoever, and ask them to make finished chipboard speakers including the crossovers.

Your friend could build an attractive wooden carcass over the chipboard skeleton.

Just thoughts.
Chris

 

Thanks for the replies guys - ooer, a bit more complicated than I thought. Options appear to be big sealed box (size? dimensions? who knows?), transmission line or ported. What are the potential characteristics of which option? The big sealed box option sounds tempting if only because there are less variables involved.

I'm getting the feeling that to make an informed decision I'd need to know the driver parameters and know how to do the hard sums to work out what would be best from those. Else its guess work.

 

That's right. Without the speaker parameters you're flying blind. It's not even possible to work backwards from the existing box as you don't know what alignment the designer has chosen.

 

Thats why his only real option as a relative beginner is a sealed box and varying the capacity. Ive spoken to both Tannoy and Lockwood before about T/S parameters with no joy. Unless you want to start down the road of measuring them of course.

 

Okay, so flying blind is name of the game . So I'll assume sealed box is the way to go. The question is then the dimensions of the sealed box and materials.

I'm assuming the best option here is a big floor stander with the driver situated so that the centre tweeter is around 3 to 3.5 feet up (ear height), with a detachable baffle and some kind of internal shelving arrangement running up from the bottom so that you could adjust the size of the internal volume when you take off the baffle to work out what the best volume is.

The current box is 13 inches wide - can't be less because of the size of the driver and wouldn't want it to be more really - so I can make the box much deeper and much taller than the exisiting one. What effect does the shape of the box have? Given that its guess work is there a width, height, depth ratio that will cause less potential problem than another? Given that its for experimenting we'd presumably want the full size to be larger than optimum.

As to materials? MDF? I'm assuming that I'll need to lag the box with some kind of acoustic damping as well.

 

Here's a few examples of cabinet design to get you started:-

http://www.hilberink.nl/speaker.htm#cabinet

 

For experimentation a few sheets of mdf nailed together will suffice, unless you want to practice your woodworking skills obviously. Speaker wadding can be bought from places like maplin. Bricks or similar can be used to alter the volume of the overlarge box. Once your correct volume is attained you can draw up plans for the enclosures proper to that volume preferably with golden ratio. At least thats what id do.

 

Dev, thanks for the links - some interesting looking boxes there.

Makes sense - What is the significance of the golden ratio in terms of speaker design? And does it matter much whether the narrowest side is the side with the baffle or the side on the side (so to speak)?

If I were to get the parameters are there any spreadsheets or programmes for working out optimal box shapes or sizes? If Tannoy cna't supply, how on earth are they measured?

 

Narrow baffle = better stereo image (or so the theory goes, less reflections from said baffle). Golden ratio box helps prevent standing waves at certain frequencies occuring. (ie something like: 1 : 1.6 : 2.3) There are programs and downloadable spreadsheets all over the net, but as i doubt the chance of you getting hold of the tannoy driver parameters I wouldnt bother. And measuring stuff like, Vas, Qts etc etc isnt a picnic either im afraid. .

 

Further to the 'nailing some MDF together' option, I suggest a base that can be inserted into the speaker cabinet with a pole to push it up and down, sealed by foam (good enough to experiment with) so that you can easily experiment with different box volumes. Don't worry about niceties like damping while you're doing this. When you find a volume that gives some bass but without the hump that small budget speakers tend to have, then you can shorten the box and make a proper base.
I saw this in a speaker DIY book once.

Even when you have the driver parameters, it's still not quite straightforward as there will be sample variations. The more you pay, the less the variations.