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TDL TRL2

Thanks.

Thats a good idea.

Im actually planning something different though. The idea is to run 4 lenghts of 15mm dowelling from the front baffle (directly behind the midbass's screw holes) to the back panel. The screw holes will be drilled through into the dowells and larger screws replaced which penetrate the front baffle and pull on the dowells. The other end of the dowel will be secured simmilarly with screws through the back panel. I'm hoping to acheive tighter bass from this mod due to the added bracing it will give. Also gives the Midbass something really solid to work against.

When its done I'll post results/pics on this thread.

Cheers, Mike
 
Installed 0.39uf Crosscaps to get the rating up to 5.99uf, closer to the original caps (6uf). The treble seems a little warmer and fuller in the upper mid. Looking forward to fitting new coils and high end resistors. Also changing the eire to something less bright.
 
I've just had a thought. Clive, the designer of these, suggested reducing the tweeter cap to 4.7, but I didn't like it, despite this apparently removing a slight bump at 2kHz approx.

Memory does play tricks, I could have sworn the original tweeter cap was 4.7, but you're absolutely right, it wasn't, it was nearer 6uF or whatever the common commercial value is. Don't make the cap too large in value, as the tweeter is handling a considerable amount of upper mid in this simple design...
 
Hi

When I ordered the caps I had to get 5.6uf + 0.39 as the cross caps werent available in 6uf. The 0.39 were out of stock so I fitted the 5.6 while waiting for the 0.39 and the sound was alot smoother. I did some mods to my CDP after that and the treble started to sound shut in and a little hard. Since fitting the 0.39's its much better. It sounds fuller and the overall tone is warmer again. As I 've changed the tweeters I really need to get them measured. Then I can redo the HF section to optimize it for the Morels. Overall its alot better than the standard setup and the morels tone blends well with the RTL midbass. Im tempted to upgrade the coils and resistors now but I sould really wait until some measurements have been done. If the bump you mention is still there (probably is, I think I can hear it) a notch filter would be best.
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Also added new plinths. Kitchen chopping boards from my local supermarket. £4.99 each.

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We're talking an "academic" bump rather than an audible one, if you see what I mean.

Clive was fastidious but at under £300 the pair something had to give and the over-complex circuits utilised by John Wright (TDL's boss) in the dearer models just had to give.

The one thing the original RTL2 could do was lift the whole sound as you stood up, where many speakers seem to introduce a steep notch at the crossover and the treble regions seem to detach themselves and "float" on their own above the speaker - the B&W 805 was awful for this - no wonder most sat on the meter bridge of a control room at ear height....

You should find it's level that will need fine tuning and the original tweeter was deliberately set a little high, giving this lovely "fresh" quality of sound. Peter Comeau, now of WD but very late of Heybrook suggests that the mid tweeter frequencies (7 - 9kHz) should be slightly up, as it can improve plucked instruments and give a sense of "air" - the RTL2 mk1 proved it IMO.
 
Yes I do agree. Strings sound very nice indeed on the RTL2's. Its that leading edge impact that I like, and the note seems to fade out nicely rather than just stopping. I also like the it that the RTL's have a great 'surrond sound' efect. I often hear instruments coming from over a metre outside the position of the speakers. Occasionally when watching movies Ive noticed sounds that appear to come from behind! They are indeed a very good design, if only they were made with solid cabinets and better quality crossover.

As mentiond above, my intention is to try and realize the full potential of the RTL, by adding birch ply cladding to the exerior and some additional bracing internally. Id like to get some measurements done so I can optimise the HF section of the crossover to better suit the Morel. Once thats done I can rebuild them with some nice components, Mills resistors, Air core inductors, and ditch the plastic terminal tray for a solid metal one. Maybe some solid brass binding posts.

PS, since doing the new plints the bass has tigtened up noticably. Theres a wider footprint now and the slabs give a stable platform. When I push the speaker theres almost no wobble. Later I will put some screws through the carpet into the floorboards to eliminate the spongy carpet. Then the slabs will sit ontop of the screw heads. Im really pleased with this mod as the biggest bug for me was the slightly soggy bass from the RTL2. Its much better now. Also when the new cladding is applied Im going to fit a couple of layers of lead sheet to the bottom of the cabinet and re attatch the plinths.

Another thing is the internal wiring, I want to change it to something better but im not sure other than the material, pure copper, no silver plating. Too harsh. Any ideas there?
 
Yes I do agree. Strings sound very nice indeed on the RTL2's. Its that leading edge impact that I like, and the note seems to fade out nicely rather than just stopping. I also like the it that the RTL's have a great 'surrond sound' effect. I often hear instruments coming from over a metre outside the position of the speakers. Occasionally when watching movies Ive noticed sounds that appear to come from behind! They are indeed a very good design, if only they were made with solid cabinets and better quality crossover.

As mentiond above, my intention is to try and realize the full potential of the RTL, by adding birch ply cladding to the exerior and some additional bracing internally. Id like to get some measurements done so I can optimise the HF section of the crossover to better suit the Morel. Once thats done I can rebuild them with some nice components, Mills resistors, Air core inductors, and ditch the plastic terminal tray for a solid metal one. Maybe some solid brass binding posts.

PS, since doing the new plints the bass has tigtened up noticably. Theres a wider footprint now and the slabs give a stable platform. When I push the speaker theres almost no wobble. Later I will put some screws through the carpet into the floorboards to eliminate the spongyness of the carpet. Then the slabs will sit ontop of the screw heads. Im really pleased with this mod as the biggest bug for me was the slightly soggy bass from the RTL2. Its much better now. Also when the new cladding is applied Im going to fit a couple of layers of lead sheet to the bottom of the cabinet and re attatch the plinths.

Another thing is the internal wiring, I want to change it to something better but im not sure what to use. Any ideas?
 
Thanks for the motivation Mike - I've just completed a major overhaul of my Mk1 RTL2's and have them running right at this minute. Here's the list of changes I made:-

Changed internal wiring to 14 gauge generic OFC from HTD.
Swapped tweeter in-line capacitors to a pair of 3uF Dayton Audio Grade 1% caps on each channel.
Put 2Ohm 2% 10W audio resistors in place of the 1.5Ohm resistors on the tweeter path.
Damped cabinet with foam and some rubbery stuff clearly made for audio damping I had in the shed put down at the bottom of the front chamber, rearranged batting per your recommendation.

I've also ordered some Morel MDT-29's to try out. Results so far are with the original tweeters...

Results:

Seems to have a less marked low cutoff than previously, more musical in the lower registers, a lot tighter too. In short, much better bass but still a bit 'loose' somehow, can't quite put my finger on it...

MUCH better top-end, far superior - detail and clarity I didn't realise my source could manage.

A tad more evidence of the tweeter's limitations - clearly with that simple crossover it's taking too much of the low frequency information and reaching resonance. I suspect that a lower cap value would sort that out but I'm going to wait and try the Morels as they have such a low Fs comparatively. I'd rather improve in this direction than separate out the HF section and break the magic.

Overall these are way better post-mod. It was a cheap upgrade to some old boxes and well worth the effort. Can't wait to get those Morels in...

I am considering a new-build using the RTL2 box design but with an active crossover and a few amps. Thinking a T-amp for the top end and an ILP module for the bottom end, Anybody out there done anything like this?
 
Regarding wiring inside...

The speaker coils represent many, many metres of thin, solid core wire for the signal to go through, so half a metre of stranded copper wire *after the crossover* isn't going to make a huge difference to be honest. A reasonable, flexible stranded instrument wire should be sufficient, to be honest, or some 0.8mm solid core if you want to be "different."
 
Probably a good point about the wiring after the coils - solid core 0.8 is likely near enough to perfect for the midbass unit. As for the top end, something with a smidge more surface area might make a tiny difference but your point is well taken - all in all it's not worth spending large sums on this bit... I reckon better coils might be a good idea in this crossover though, the iron core ones seem pretty reasonable but I do have a hankering to try some of those Jantzen film ones just to see if they make a difference.

To be fair though, the changes so far have been pretty incredible for the small investment made and I'd have to say the lower registers on these RTL2's are sounding more musical than most speakers I've come across. They may not be perfect (the hybrid transmission line no doubt contributes to the slightly lazy timing and adds to the general musicality) but they're really very good. I'm comparing them with my (passive) Linn Keilidhs and to be honest I'd have to say it's pretty close - more of a taste decision than an absolute perfection judgement. Once those Morel tweeters are in I bet we're talking dead heat or advantage TDLs...
 
OK, short of making these active I think the Morel tweeters I installed last night make these about as good as one could hope for from such cheap speakers. Morel MDT29's seem to blend reasonably well with the midbass after a few hours to settle down. They were outright scary when I first fired them up and I wondered if I'd made a horrible mistake. After a few minutes I decided not to 'get used' to that (apparently you can even get used to Bose 'speakers' after a while?) and I left them running for a few hours today while I was out and they have changed appreciably for the better - very fast, detailed and still smooth.

Overall this is a great package, my RTL2's have gone from unused to my front room speakers, if you can get a set on ebay for a few dollars, buy them and play - the basic design is really very good as I always thought it was back in the mid 90's but now they've got some extra sparkle up top and less confusion in the midrange.

Now to design an active crossover and build an active replica set!
 
Hey I just found this thread again, great surprise to see someone has followed a simmilar upgrade path to me!

About the bass sounding a little bit loose:

This is definately to do with the batting. Some of the more experienced PFM'ers thought I was mad re-arraging the stuffing due to the fact that Transmission lines are critical to the amount and position of the stuffing. I had a play around wioth mine and found that I could not only change the way the bass sounds but also the forwardness of the midrange.

Currently the damping material is like this:

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It did sound better but after a while I was looking to get the bass even tighter. However, Im borrowing a Cambridge Audio 840A at the moment and this has really tightened up the low end. I suspect its due to the extra power, nearly double that of the amp ive been using prior. I read eksewhere that the RTL's need a fair bit of power to sound their best.
 
At one point in addition to the above I had a small peice of foam losely placed directly behind the main driver. This gave a really forward midrange and a little less overall bass level, it still went deep though. Soon im going to try some lambs wool which apparently is a fantastic material for damping speakers. I'll post the results of my experiments here.

Other ideas I've had to tighten up the bass are:

Fitting 2 batons between the front and rear baffles in line with the top 2 mounting holes of the woofer. Then using longer screws that will penetrate the baffle and pull against the batons. The idea being to increase rigidity of the front baffle and give the driver a really solid mass to work against.

Another option to produce the same effect as above is to have a new 'extra' baffle made from 10mm Alluminium. This would mount directly onto the existing baffle. It would be milled out to allow for flush mounting of the woofer and tweeter and have threaded holes to allow the mounting screws to be tightened with more force than they would into wood.

This would be done in addition to covering the rest of the cabinet in 1/4" Birch ply, and a hard wired crossover. It would give the speaker a really modern look too.

Ive recently replaced the 10uF caps on the woofer with equivelent value Jantzen crosscaps. The effect was a more natural sounding bass (slightly tighter) and cleaner sounding lower midrange.

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Thanks Mike! My damping is now adjusted - I've found that the mids are best with that extra piece of material pushed against the crossover and slightly 'up', away from the port. People who say you're crazy to play with the damping clearly don't understand that this is not a normal transmission line - it's a hybrid, using a reflex port which is also tuned to behave like a quarter-wave line. I think it effectively 'blurs' the tuning peak of the port but I look forward to somebody with more knowledge about this design telling me why it really works so well.

I'll try the caps in the bass section. Have you sketched out the crossover at all? I think I might do that tonight/this weekend and then just build a point-point version of it with some of those Janzen foil inductors - I just need to find a way to measure the existing inductors. Anyone know what values they were designed with?

I ran a frequency sweep through the TDL's from 10Hz all the way through to 20kHz and the crossover looks to be pretty flat through the 2-4k range where I assume the crossover works. They suffer from really bad ringing at 470Hz or thereabouts though, which I'm going to assume is the stamped frame of the midbass units (so I'm going to stick on some of that bitumen gubbins) and have a droopy response from about 300Hz down (other than room nodes which break up the otherwise smooth roll-off in the bass region). I think they would benefit from baffle step compensation but that puts the crossover in a whole new realm of complexity. Has anyone tried this?

I'm also considering going active, I've got quite a few Audiosource AMP300's hanging around in my house... That would certainly put the control in a whole new league but makes my pile of gear a bit large.
 
Hi.

I havent drawn up the XO but if you beat me to it please post it on this thread. I also fancy trying those Jantzen coils. I havent checked but sometimes cored inductors have the value written on the end of the ferrite. It will probably be written in black ink so you might need a flashlight to see it. You also need to take into account the resistance of the coil I think.

Your results from the FR analysis are interesting. You could be right about that ringing being caused by the basket. Someone on Diyaudio.com suggested applying 'no more nails' or a simmilar hard setting glue at the point where the basket joins the magnet. You will notice there is a small gap so I would think the idea is just to fill this so the magnet is more secure. Also adding bitumin might be good. Just be sure not to overlap the edge of the frame legs, you dont want to restrict airflow.

If you look behind the mounting flange on the woofer there is a hollow recess. I have considered filling this with a 2 part resin. You would need to lay the driver face down and get it perfectly flat and plug the screw holes. Then pour the resin until it meets the edge of the flange perfectly. You would have to re-drill the mounting holes after. I experimented by filling this recess with blue tack and it did improve things. The midrange seemed less couloured and the upper bass better defined. Why dont you try it and take another sweep and see if it makes a difference to that 470hz ringing. Id be very interested to know what happens.

Theres also the issue of the cabinet which isnt the best build quality really. I plan at somepoint to cut out the front baffle and add a new one made from a stiffer material. Something like Birch ply would probably be better. Also a thick bead of glue around the internal partitions and brace wouldnt be a bad idea.

On the whole though its so amazing how much performance can be had from these speakers with just a couple of mods. Im still amazed at the imaging these things produce.

Do you think that plastic terminal tray is a problem? I cant help thinking that a bit of bitumin would be good there also.

Mike.
 
At this point I think I should suggest getting another pair as a reference for tonal balance. The standard article is too bright as it is (about 2db if I remember the measurements I saw) and if the Morel tweeters are brighter again it must be in the Royd/Neat screaming category now....

The RTL2 mk1's seemed to work best against a wall and baffle step correction will certainly turn them into 0.75's and I really wouldn't do this if I were you - far less sensitivity, treble sensitivity lost as you pad the thing down to the new mid level and massive cone excursion to get anything out of them.

If there's a massive resonance in the midband, Id suspect something in the cabinet, as those drivers were built on good commercial chassis and didn't buzz to my knowledge.

I wish Clive Gibson would look in here, as he could give you chapter and verse on them - he designed the basic drivers and box layout and I believe the crossover too. Final voicing was down to John Wright.

Dear old things, the RTL2 mk1, let down by claggy cabinet finishes, especially the rosewood coloured ones.
 
Thanks for that DJSR.

Maybe bracing the internal partition to the front baffle would be good then. Also cladding the enclosure in 1/4 birch ply should be worthwile.

I wouldnt say mine sound overly bright but with some recordings I do feel a little more attenuation on the Morel's would be beneficial. I'll try replacing the resistors with some 2ohm.
 
The internal partition was well attached to the cabinet sides as I remember, but an extra brace wouldn't go amiss.

This design worked BECAUSE it was so simple and the balance was almost a "tamed Naim" style liveliness. I'd love to find some mk2's one day and liven them up the same way (easy once you see the 5 Ohm or so tweeter resistor and change it for one much less in value).
 
Hi DJSR.

Yes the partition is well attatched as are all the internal joins (plenty of hot glue IIRC) but thats not the real issue. The point is to control the resonance of this panel by attatching its centre to the front baffle, thus damping the vibration.

At the moment I have another project which needs de-bugging but as soon as I can I'm going to have a go at improving the cabinets. Im also going to re-build the XO 'point to point' using some 1mm Gold plated Silver wire that I have spare from a I/C experiment. At the same time I intend to replace the resistors with something better. The new XO will be sealed with 2 part resin which I will also use to fill the recess behind the mounting flange on the mid bass driver. I may build new plinths which incorporate the new xo, or go for a seperate enclosure. Im not sure yet.

Any ideas on what to do with the terminal tray? I want to get rid of it completely but I cant decide if I should fill it with a section of wood or cover it with an Alu plate. What do you think would be best?

(Heres an example of a resin sealed XO taken from John Ekels site):

SEAS%20W15CY%20Maple%20020%20verkleind.jpg


http://www.johneekels.nl/websitepagina/speakers.html
 


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