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Tannoy Monitor Golds

The Red schematic looks a fair bit simpler to me, though I don't really understand these things. It can be found here, and the Gold is here. As I understand it the main difference between the two speakers is the bass cone, the one in the Gold is heavier, lower impedance and a little less efficient. The compression driver is the same part, though I think there may be some very slight differences in the horn design.

Tony.
 
Very similar looking.

On the bass side the difference is just the inductor to change (maintain at ~ 3khz?) the X over frequency due to the difference in bass driver impedance.

On the treble side the Gold has more adjustment but if you look its a very similar circuit. 10 + 20 ohm resistors with a 1.5uf cap over them, as opposed to 30 ohm with 2uf over, thus allowing adjustment to the roll off on the golds. Before this there is 6.8uf instead of 4uf and a volume of HF control.

You could make it work, with some minor value adjustments, but I wouldn't chance it or mess with the original gold X over. Better build a nice new one for the Reds with the original red values or sell the gold XO and buy some original red ones if you can.

Building a new XO based on the gold circuit, but with the red values might be interesting with some quality components.

Very tidy circuits here:
http://www.44bx.com/tannoy/images/MonitorGold12_15xO1.gif
http://www.44bx.com/tannoy/images/MonitorRedSilver15xO1.gif
 
Thanks Tony and Trancera,

As far as I know the XO frequency is 1Khz for all the Tannoy monitors until after HPD. Judging by these schematics the main difference in the bass XO is a 4mH inductor (Red) and a 1.2mH inductor (Gold). Using this as a guide http://www.apicsllc.com/apics/Misc/filter1.html it seems that the 1.2mH on the 8ohm Gold gives a 1kHz roll-off point, and the 4mH on the 16ohm Red give a 700Hz roll-off point. On the treble XO the use of a 6.8uF on the 8ohm Gold gives a 2.9kHz roll-off point, and the 4uF on the 16ohm Red give a 2.4 kHz roll-off point.

Therefore the use of the Gold XOs on Red drivers will give the following: 1.2mH on 16ohms = 2 kHz Bass roll-off, 6.8uF on 16ohms = 1.5 kHz Treble roll-off.

I need to test a 15” Red driver but I only have a 15” Gold crossover – with the above values am I likely to cause damage to the driver (most probably HF compression driver, used below the recommended XO point) if I keep it to moderate levels?

Cheers, James.
 
Well the bass should be fine, after all a bass driver doesn't need a crossover at all to stop it being damaged, within reason anyway.

The treble is of course the worry, it will be seeing frequencies an octave lower at normal volume, not reduced. To get around the problem, without having to worry about the frequencies I would:

1. Take your favourite test track
2. Rip it off the CD
3. Take it into something along the line of audacity
4. High Pass filter at 2.4K
5. Burn CD and play into driver - it will then only see higher than its 'normal' crossover frequency.

Be careful with the volume, it will seem very quiet!

... on the other hand I don't think it would damage your driver when run at less than half power, after all crossovers slope so the tweeter sees some 1.5K frequencies anyway, in fact much lower, just a lot less power output than at 2.4K. But do be careful.
 
Any of you Tannoyistas aware of a DIY cabinet for 15" Golds that has a narrow profile? Someitng a little slimmer than the usual like GRF's?
Thanks.
 
Update: Need not have worried to be honest. The 15” Tannoy Red is built on a epic scale and can probably handle extensive abuse. Had a quick think about the treble roll-off at the best part of an octave lower than the original crossover (12dB slope) – approx 12dB higher at 1kHz = 2^4 the power output = 16 times the power output at 1kHz; or 50w/16 power handling = 3w @ 93dB/0.5w sensitivity therefore about 100dB max output even with the wrong crossover values. In any case I used the ITunes Equalizer controls to reduce output at 500Hz and 1kHz by 10dB to try to ameliorate this anyway. The driver works perfectly and sounds fine, although I need to build up a crossover with the correct values long term. The Red has a beautiful midrange quality and obviously groundshaking bass down to about 35Hz in the sealed 100L cabinet. Interesting to note that the thickness of the cast frame on the Red 15” is at least twice as thick as on the HPD 12”.

Photos here:
http://www.flickr.com/photos/61564593@N08/5866222634/in/photostream/

http://www.flickr.com/photos/61564593@N08/5866222730/in/photostream/
 
sybil said:
Update: Need not have worried to be honest. The 15” Tannoy Red is built on a epic scale and can probably handle extensive abuse.
Click to expand...

I agree about the epic scale, from what I can work out from pictures the basket casting, magnet etc is the same as the Gold, and there is something amazing about picking one of these monsters up - they are simply huge, hefty beasts. I'd be reluctant to conclude that they can handle excessive abuse though, remember their context, in the Red's day 15 watts was a heck of a lot, few amplifiers had more. I get the impression that Tannoy's power rating is honest though, i.e. they can take their stated watts as RMS for a very long time unlike most ridiculously over-spec'd modern speakers where the voice coil would simply melt after a short while. Your Reds look in lovely condition, very dark non-faded cones. Where did you find them?

Tony.
 
A word of caution re power input into comp drivers, It ain't the watts at lower frequencies it's the cone/dome excursion. The diaphragm is very close to the phase plug and you will almost certainly damage it with the even modest 'watts' if you push their xover too low with shallow slopes( besides breaking the x1.7 horn cut off rule and sounding crap).
 
The Tannoy 15" cone flare has a 500hz horn cut off ie you ideally don't want your HF driver xover lower than about 1khz(500 x1.7 is ok in some quarters with a steep xover slope but to minimise horn honk it's best to go for 2x horn cut off ime.)
 
Thanks for the useful info Cooky. I kept the volume to a minimum and changed the eq slopes to reduce musical output at these frequencies. I am satisfied that the Red in good order and will now look to source the correct crossover.

In the meantime I will return to the 12”Golds and HPDs that I am using in the Mansfield cabinets. I am almost tempted to make a set of mini-GRFs out of the Mansfields, retaining the original side walls and rear baffle, but substituting a new baffle from 24mm plywood and internal horn parts and internal enclosure lining made from 18mm plywood. I have done a quick CAD drawing of this just sizing up by eye and it would likely be a 4/5ths scale GRF-R replica in section, designed to take 12” Golds or HPDs. Does anyone know of a horn-modelling programme that I could test this out before I get handy with the cabinets? The Mansfields have internal dims of approx 760 x 500 x 320 as opposed to the GRF-R internal dims of 940 x 550 x 400. I think I can probably get all the horn relationships to work at this 4/5ths scale. I’ll post a sketch of this for discussion.
 
As above here is a quick AutoCAD sketch of a 4/5ths scale GRF-R replica horn built into a Tannoy Mansfield (or presumably Lancaster) cabinets.

http://www.flickr.com/photos/61564593@N08/5866605544/in/photostream

I have eyeballed some dims and taken others from memory so it will most likely change in detail. However, it would be cheap and easy to build and the external finish is already done. I intend to make the horn rebates in the side walls by lining the internal walls with 9 mm ply to sides and base. Horn chamfers could be made from solid softwood sections. The addition of the horn should serve to brace the rather resonant cabinet nicely. Cork lining to the horn mouth. I need to feed these figures into a Horn modelling programme with the details of the 12” Golds to find out what the response is, and to see if this is a worthwhile endeavour. Anybody got any suggestions for this?
 
I am building a pair of Baltic birch ply cabs at the moment using 21mm throughout for a pair of Reds. They will be exactly 45cm wide. About the narrowest you can go and fit a 15" driver.
See a pic of drawing (bit crappy done in .ppt).


Here's one of the cab in progress before the plinth was on


I have not got the Red's to try yet but will load my HPD's in and see on she sounds.

I used Hornresp to model the throat and mouth of each section of the folded horn and ensured the right areas were used to get the same modelled response as the usual rect. GRF. Backloaded horns can't really be modelled in Hornresp perfectly as you cannot have the front radiation / HF horn playing in, but it gives a good idea of the folded horn comparison.

The height will be 125cm and deeper than usual to get the same volume as the usual GRF.

Interesting little project.



aquapiranha said:
Thanks Cooky. I am not bothered about the overall size really I just like the look of slimmer cabinets but if it comes down to it I will not be sacrificing performance for looks.
Click to expand...
 
speedysteve1 said:
I am building a pair of Baltic birch ply cabs at the moment using 21mm throughout for a pair of Reds. They will be exactly 45cm wide. About the narrowest you can go and fit a 15" driver.
See a pic of drawing (bit crappy done in .ppt).


Here's one of the cab in progress before the plinth was on


I have not got the Red's to try yet but will load my HPD's in and see on she sounds.

I used Hornresp to model the throat and mouth of each section of the folded horn and ensured the right areas were used to get the same modelled response as the usual rect. GRF. Backloaded horns can't really be modelled in Hornresp perfectly as you cannot have the front radiation / HF horn playing in, but it gives a good idea of the folded horn comparison.

The height will be 125cm and deeper than usual to get the same volume as the usual GRF.

Interesting little project.
Click to expand...

Very nice Steve. I have followed with interest your projects, and thank you for sharing that with us. I would love to hear your thoughts when tested, and maybe get a sly look at some plans? :D
 
Thanks :) Have you seen my main project of the last few months?



5 way, Tapped subs, concial mid bass, mid and upper + tweeter
These babies ROCK!

Sorry for the off topic Tony:)

aquapiranha said:
Very nice Steve. I have followed with interest your projects, and thank you for sharing that with us. I would love to hear your thoughts when tested, and maybe get a sly look at some plans? :D
Click to expand...
 
Steve, they look amazing - what are the drivers and how do you manage all the XO points?

Does anyone know how to remove the knobs from the Monitor Gold treble energy switch without breaking them? I need to tighten one pot but I dont want to crack the plastic of the switch getting it off. Also, what screw thread holds the faceplate onto the back-box?

Cheers, James.
 
Steve,

Thanks for sharing these pictures. Fantastic projects, and the pics are great ammunition for me to show and say "Look, you see, I'm not so bad..."

Andrew
 
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