Which Tannoys, folks?

[Reffc]

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?

The thought had occurred to me but if it proves problematical I can always take the jigsaw to them!

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.

My amp has tone controls...that's what they call them although as you pointed out earlier, they don't alter tone, the roll off (or increase) treble response or bass response respectively. I don't therefore need the compensation on the speakers.

If your room is treated/furnished to achieve a decent response with the controls set flat, or the speaker crossover designed as flat then this is the ideal. If source components or the amp are changing things that much that adjustment is needed then I'd argue here's something wrong with them. Of course source material is a different matter and I do find it useful to have a little compensation control for badly recorded pieces.

The earlier comment about small currents being measured through the tone controls not being representative is something that I don't understand I'm afraid as it doesn't seem to make sense to me Geoff. What is "micro-welding" and how does this work? The meter I use measures DC resistance period, so if its different its purely because the circuits are exhibiting variations in resistance which will have an effect on the signal. The value of the circuit resistors and DC resistance does not alter as voltage is increased, only the current alters. However, in operation, the signal is alternating current and circuit impedance rises with frequency (properties of the driver circuit impedance with frequency) but this in itself does not can cannot compensate for resistance differences with the treble roll off and energy controls...in other words, you will not get both speakers to measure the same given the same input signal if the treble controls operate with different resistance and increasing voltage does and cannot not change this. IMHO of course.

[DSJR]

I think I'm right in saying that the 12" and 15" HPD's may have different crossover needs and I'm not sure if the basic crossover was shared? Cheviots (12") certainly needed "-1" on the level control and the sometimes rough treble (at the time with the gear used back then) needed -1 as well on the rolloff control. The larger 15" driver may not need this at all obviously.. The old 3kHz peak otherwise has been catalogued on the web..

[Reffc]

I think I'm right in saying that the 12" and 15" HPD's may have different crossover needs and I'm not sure if the basic crossover was shared? Cheviots (12") certainly needed "-1" on the level control and the sometimes rough treble (at the time with the gear used back then) needed -1 as well on the rolloff control. The larger 15" driver may not need this at all obviously.. The old 3kHz peak otherwise has been catalogued on the web..

You may be right there David as they certainly changed the crossover design between 15 inch units as well as having different ones for the 12 inch unit. To confuse matters more, they changed some of the resistor values between 12 inch models, and even between the same crossovers from different eras!

The later 385's all used the HPD385A crossover:



This compares with the HPD315 Crossover:



But the MG series shared the same crossover for both 12 inch and 15 inch models:

[walpurgis]

If source components or the amp are changing things that much that adjustment is needed then I'd argue here's something wrong with them.

The earlier comment about small currents being measured through the tone controls not being representative is something that I don't understand I'm afraid as it doesn't seem to make sense to me Geoff. What is "micro-welding" and how does this work?

Nowt wrong with my gear. Components do have varying sound characteristics and sometimes it helps to modify the balance. Much the same effect can be achieved by swapping cables about according to their influence on the sound.

As for the 'micro-welding', rotary 'click' switches have metal to metal contacts and if you were driving your speakers to a reasonable level and could see the switch contacts, assuming it was dark, you would see a tiny arc across the contacts as they make or break the actual contact. This arc does indeed produce a miniscule weld or scar if you like at the touching point. (This is why contacts that handle significant energy erode or burn away, i.e. car contact breaker points, light switches, etc.) A meter would give insufficient energy to cause this, therefore readings may not represent what happens under use.

[Reffc]

I see where you're coming from Geoff, but its exactly this variability in the controls and the corrosion/wear of the switch which leads to surprisingly large variations in DC resistance across the switch. I measured each of the resistors and they were all well within tolerance (expect for the ones I replaced) but the switches unless stripped and cleaned will result in quite major differences between units...impossible with old un-renovated units to get them sounding the same in theory. However, if they sound ok and can be adjusted to personal tastes, then that's all that matters for the individual.

[montesquieu]

I've just picked up a set of Dave Slagle autoformers from Shuggy that replicate, using a high quality transformer core, what the old switchable inductors do - I believe Joe may have a set too?

I'll be sending a package off to Nick G to work his magic on my existing crossovers as soon as some new, better quality binding posts get to me.

I haven't missed the old Tannoy variable settings (when I had my custom ones done I went for fixed inductors, like Marco) but by all accounts Dave's solution should in theory be superior to the fixed ones in terms of sound quality. Am going to explore top of the line caps as well.

[Reffc]

I'll be interested to learn what you think of the New x-overs Tom. I ended up using the services of Mark Picher who has a reputation for very good design and construction (he was recommended by none other than Lockwood Audio).

The Veneer's finally arrived

Going to attempt to veneer one of the cabs this evening and if I don't mess it up I'll post some picks later (always sets the nerves off when I'm handling veneer...especially at what the stuff costs these days).

[Reffc]

First of the cabs veneered in Sapele to give a nice gentle contrast with the antique-teak of the main cabs. Just got to give it a final light sand to bring the grain out a little and get a nice smooth finish before a few light coats of Dutch oil:

[walpurgis]

It's all beginning to look rather majestic, as big Tannoys do. I recommend putting the family crest on the front of the plinths just for that finishing touch. They should certainly look the part once you polish them. No doubt they have a very imposing presence when you walk into the room.

[montesquieu]

First of the cabs veneered in Sapele to give a nice gentle contrast with the antique-teak of the main cabs. Just got to give it a final light sand to bring the grain out a little and get a nice smooth finish before a few light coats of Dutch oil:

Hmmm not sure of the look here, Paul. I'd have painted the ply black to de-emphasise the plinth element and throw attention to onto cabinets themselves.The veneer rather draws the eye to the plinth section.