Which Tannoys, folks?

[Reffc]

As a reminder to everyone still persevering with original crossovers with the variable treble controls, I measured DC resistance across each part of the circuits today and found unsurprisingly that there was a huge variation between units due to variations in wear with the variable controls.

Where I would expect both to be identical is where the controls are rolled up full where the resistance should be close to the 50 Ohms dictated by the wire wound resistor of that value in each unit. I had just replaced my resistors with Mills wire wounds of 51 Ohms (12watts) and got readings of 51.4 and 51.6 across the crossover circuit, but when rolled back level, one measured 31 Ohms and the other 1.2 Ohms! Proof if any was needed, that the old crossovers are let down by the treble controls, which are only any good if taken apart and thoroughly cleaned up which is a PITA of a job (a day per unit).

Good job I hadn't gone to the expense of replacing anything on the originals except for the large value resistors!

[Marco]

Proof if any was needed, that the old crossovers are let down by the treble controls, which are only any good if taken apart and thoroughly cleaned up which is a PITA of a job (a day per unit).

Indeed. I was never tempted to retain anything about the original crossovers, including the treble controls, although I know that things are slightly different with this current project of yours.

The improvement gained by removing the treble controls, and hard-wiring them in the 'flat' position, using VDH Hybrid internal speaker wire, was rather shocking!

Marco.

[DSJR]

Tannoy also discovered in their crossover re-works in the early 80's how bad these switches could become and that's why they were replaced with the rather tasty screw settings as on your Turnberry's.

One of the things has usually to find the optimum setting and hard wire this on the board, bypassing the controls altogether. My preferred on Cheviots for example was -1 on both, but that was then, although on master quality material.....

[Marco]

That's exactly what I did, resulting in fundamental sonic improvements.

Unless you want to retain the vintage aspects of Tannoys, the treble controls are completely unnecessary. I don't even see the point of them on modern Tannoys, as if your system is voiced properly and the room is decent, there should be no need to move the controls from the 'flat' position.

Marco.

[Reffc]

That's exactly what I did, resulting in fundamental sonic improvements.

Unless you want to retain the vintage aspects of Tannoys, the treble controls are completely unnecessary. I don't even see the point of them on modern Tannoys, as if your system is voiced properly and the room is decent, there should be no need to move the controls from the 'flat' position.

Marco.

I agree with that, however it does no harm having them as all rooms are different and at least it allows the end user to set them for best in room acoustic performance then forget them, especially so these days of amps without proper tone controls (shock, horror, I said it! ) Mine are set to the level positions and the crossovers I'm getting are designed for as flat a response as the driver will deliver within reason. After that, it's down to how I tune the cabinets (damping etc) as to what the Mansfields will sound like. I still have no idea what to expect as I've never heard a pair before, but in some ways, I'm not that bothered as I'll have rescued them and (hopefully) improved on the originals with the care and thought I'm trying to put into the project.

[walpurgis]

I'm sorry, "tone controls", what are they? I vaguely recollect somebody using that term back in the seventies or eighties, but don't understand what bit of 'tone' they refer to.

Actually, I would not have them on an amplifier, but might consider retaining a Musical Fidelity X-Tone for making recordings (or just an equaliser) to address imbalances in older material.

I have kept the tweeter 'level' and 'roll off' controls on my Tannoys, because I know if I take them out of circuit there'll be a 3db rise in HF output. Not what I want. I'm aware there are ways this can be compensated for, but until I notice a problem with the existing switches I won't make a change. What is not widely understood, is that with the kind of switches used by Tannoy (and other makes), is that meter readings don't tell the whole story. A meter only puts through a tiny bit of current and won't necessarily read the switch contact accurately. When the speakers are being driven and a few volts are going through, the switch contacts 'micro weld' and make a very positive contact. This does of course justify the argument for a good contact clean though

[Marco]

I have kept the tweeter 'level' and 'roll off' controls on my Tannoys, because I know if I take them out of circuit there'll be a 3db rise in HF output. Not what I want. I'm aware there are ways this can be compensated for, but until I notice a problem with the existing switches I won't make a change.

Can't say I noticed that, Geoff, when the controls were removed on my 15MGs, so I guess the chap who made the crossovers for me, and installed them, compensated for that.

Mind you, before when the original crossovers were in, the speakers sounded so veiled, tubby sounding and old fashioned (dunno if my Tannoys had particularly bad crossovers, but I certainly couldn't have lived with them that way), that I guess the much livelier, vivid and more detailed sound, but in no way artificially 'forced' or 'in yer face', I've got now, is fundamentally 'brighter' too, but I doubt for the reasons you've mentioned.

It's more likely the result of very old caps and resistors, long past their 'sell by date', being replaced with brand new and sonically superior modern varieties, as the 'before and after' improvement was veritably 'night and day'!!

Even if such fundamental sonic improvements hadn't happened, the thought of tone controls sitting in-line with the signal path, would've gone against all my purist principles and done my head in, so sooner rather than later, they'd have been whipped out, and everything hardwired, as I'm a great believer in keeping signal paths as short and as uninterrupted as possible.

If it were practical to hardwire my whole system together, without any cables or connectors of any kind, I'd do it!!

Marco.

[The Black Adder]

Hi Paul.

Just an observation with the stands here. I made some stands just like those before I went with some open metal ones for the Lancasters. One thing I remember was that they sounded better with an open back as they acted like boom boxes. Have you tried that at all? It may be a different kettle though with those cabs, but it might be worth a go... Maybe even a circular port if you need to keep more rigidity?

[walpurgis]

I have to say, I do find the controls switches useful on occasion. I do chop and change components around within my line up and currently find -1 on the tweeter 'level' setting seems about right. I don't use the 'roll-off'. There is no audible imbalance between the speakers.

I have yet to take the crossovers out for evaluation. This will be done and at the same time the internal wiring will probably be upgraded. No rush, it's all sounding very fine indeed at the moment.

As for hard wiring an entire system, it has been done. I vaguely recall a feature in a mag about a system which was like this, in America I believe. Not sure the benefits would outweigh the hinderances though.

[Marco]

Indeed - it would be totally impractical, but it doesn't stop me from getting as close to that ideal as possible, as the sonic benefits of doing so are always easily heard!

I do chop and change components around within my line up.

That's where you and I differ, as I have very much a settled system now. The only changes I make these days are to ancillary items and/or internal components in my equipment, some of which is tube-rolling.

Marco.