Rehousing speaker - TDL RTL3

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I'm bored and can't afford the Seas drivers I want yet, but I do have a pair of TDL RTL3's collecting dust in the 'sound room' (my loft conversion). I love these speakers for what they are, but after seeing the flimsy chipboard cabinet and very poor looking crossover and internal wiring, I want to take out the drivers and use them in a new design.

A long shot, but has anyone got any T/S parameters for the bass driver? or perhaps done some mods on these speakers?
 
I once had the RTL4 (i think the bigger brothers to yours). No idea why i bought them; must have been high on something. Ah, yes, remembered - they were very cheap :) No matter how hard i tried i couldn't make them play music to save their lives - boomy bass and generally very annoying sound. Maybe it was my room or my valve amps but they simply didn't work. The cabs are terrible, the drivers - dirt cheap. Your best option is probably to sell them and buy some reasonable drivers with the money - i am sure you'll do a lot better.
 
Your opinion is appreciated. But my experience with them is quite the opposite of yours. They were cheap, I think about £400 when I bought them, but they blew away the competition to my ears. They are known for their good bass, and the soundstage is nothing short of huge. I've put them next to a pair of Celestion A3's (quite in a different league) and they held their own in the bass and soundstage area. In fact the whole experiment was to try and identify what the Celestion's were missing.

Enough rant, back to measuring...
 
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Ah, I used to love my 3's, but you're right about the 4's they were rubbish in comparison. ;) But, saying that, the mistake most people made with all the TDL range, IMHO, was driving them with underpowered amps, they needed 80-100w minimum to really sing.

The drivers in the early RTL3s were Monacor SPH175, they had squared off sides. The later, inferior versions had Visaton drivers, sorry I'm not sure of the exact model, but as they had paper cones, I think they were probably the same as, or a variant of the WS17E.

I did have measured parameters for the Monacors, but I suspect they have gone to data heaven in a HD crash years ago, however if I find them I will post details.
 
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Vikash said:
I heard that TDL made their own drivers.

Yup, you are right, all the drivers made for the big TLs were custom, but the RTL range used off the shelf drivers for budgetary reasons. I learnt about this from a chat with John Wright, as I needed to get replacement drivers for the mate who bought my 3s from me. It was as they were just closing down, before the Richer sounds buyout, and as they had no spares in stock, and John thought it was all over, he had no problems with giving me the driver details. Nice Bloke. :)
 
I found the Monacor SPH-175 driver and it does look very similar, although no exact from the pictured angle.

A couple of concerns. My measurements show Re = 10.9 (versus 5.7 on SPH-175 datasheet) and SW impedeance plot shows impedence = 150R at fs (versus ~93 on SPH-175 datasheet)

Where would you put your money? Almost certainly at a different revision driver right (my TDL's are at least 7 years old)? Or perhaps it was a modified driver just for TDL? Or maybe its my SW setup...but testing resistors is accurate.
 
I would go with your SW measurements
meaning believe them, or the fault is in my set up?

I ran some quick tests: my jig v2 and SW exactly matched my DMM readings for every resistor measurement. (I went up to 2K7R)

Is it possible for t/s parameters to change over years through underpowering, overpowering etc?

I'll test the other three drivers to see if I get consistent results.
 
Ok I've tested the four drivers using SW.

Does this look like an acceptable difference between four identical drivers? It seems a bit much to me.

Max differences between all four drivers:

fs: 6Hz
Qts: 0.11
Qms: 0.27
Qes: 0.13
 

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Well, it looks a little more than I would expect for new drivers, but for well used 7 year old ones I am not surprised. Just think of them as properly run in! ;)

The differences are likely due to manufacturing tolerances being exagerated by time and positioning. For instance, was one driver more in the sunlight than any others, or maybe one speaker was nearest to a radiator or an indoor plant, leading to slightly different levels of humidity. All will have a slight effect over time.

I would suggest that if you use them, you pair them up so the lumped parameters even out.

However, on reflection, I would suggest you just mod the existing system. Using SW, you can work out the system response, and upgrade the tweeter and crossover. You could possibly even add a sealed back dome mid driver as well, such as the Vifa DM75. Don't worry about the chipboard box, as they are TLs, the stresses on the box are not nearly as great as a sealed or ported design. That way, you get the excellent bass of the originals, and clean up the mid highs.

edit- here is the link to the DM75 datasheet, thoughon second thoughts they may not fit in. Hmm ;)
 
Ello pinkmouse,

All will have a slight effect over time.
One of the bass drivers and one tweeter has been replaced over the period as well. Result of underpowering on a drunken birthday.

I guess I should model the drivers based on the mid-measurements of all four?

However, on reflection, I would suggest you just mod the existing system
I see your point, but I kinda want to get my feet wet ,and this seems a good place to start since I have the drivers to spare. Kinda like a test run before I take on my expensive Seas design.

I want to use this material for the enclosure.

Don't worry about the chipboard box, as they are TLs, the stresses on the box are not nearly as great as a sealed or ported design
Well I had a feel around in the cabinet, and I can't see anything that classes them as TL's. Just seems like a rectangular box with a vertical brace in the middle. It might need closer inspection.
 
HELP! I just tried modelling the drivers using the t/s params derived using SW (haven't done the VAS yet - using current Moncaor SPH-175 VAS = 48l, xmax=2mm)

fs=32
re=10.9
qms=9.11
qes=0.82
sd=137cm
le=0.44

Unibox Standard Designs:
Sealed
Vb=1760.8l
fb=32.86Hz
f3=32.87Hz

Ported
Vb=750.6l
Fb=16.92Hz
F3=12.95Hz

LOL. Can anyone shed some light on the suspect qms and qes values?
 
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Hmm, just used the online version of winisd with your numbers for a quick check, and it comes out with the following recommended sizes.

Ported - Volume 97l, F3 at 25Hz, Fb 26Hz

Sealed - Volume 48l, F3 at about 45Hz

Both of these seem reasonable, within isd's usual limitations on tuning, and from what I remember of the drivers. Maybe you have found a flaw in the Unibox curve fitting routines. I would suggest trying the above volumes in Unibox to see how they work out.
 
Way out. But ignoring even the SW measurements, the Re=10.9 (published = 5.7) which could mean it's a different driver.

If I change the Qms to something more sane, everything seems to look better. I've measured each driver a number of times, trying different ways of supporting them just to rule that out, but the measurements are relatively consistent.

SW measures my sub closer to its published specs (after 4 years use), so it's not an obvious SW setup error...
 
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The Re thing suggests a 16 ohm driver, does this agree with your curves on SW?

The high Qms is strange, but I once measured an Audax 5" driver that had a Qms of about 12, but the Qes was much lower, at about 0.3.

I wish I could remember the exact designation of the Monacor driver, perhaps it had significant differences to the current model. Maybe even it was a driver modded by TDL, that they then released in their general range, but is now discontinued.

I would check the Vas as a priority.
 
I've had a thought. I questioned the high impedence at fs and then forgot about it. Now i don't know how the qms is calculated, but perhaps this is related somehow. I guess it's feasible that a bad SW setup could result in increasing error of impedance measurement as it gets higher, thus being realistic for my sub (~35R at Fs) but not so for the Monacor (~130R at Fs).

:scratch:
 
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