The Celestion kid strikes again.....!

[Marco]

Hi Nathan,

Yes I noticed that, so you should try and find out. I particularly enjoyed reading this part of his appraisal:

...wait till you hear the thrill of the power of a bass drum reproduced through these masterpieces as the "thud" hits you in stomach and gives you goosebumps!

...These speakers are the very antithesis of modern "tight" speakers with their hamburger sized bass drivers which attempt to defy the laws of physics...

Hehehe... Definitely a man after my own heart!

And it mirrors what I heard from them on Friday night on the end of a good but fairly unremarkable Technics separates system. Goodness knows what they'll be capable of on the end of my Copper amp, etc!!!

Marco.

P.S Does anyone know how efficient they are? I can't seem to find any mention of this anywhere.

[RochaCullen]

Just had a quick Google and apparently they are fairly inefficient 4ohm monsters requiring a bit of grunt. So your copper amp might not be up to the job.

[Marco]

The crossover looks quite good actually Looks like a 24Db/octave low pass feeding the bass driver, the mid is fed by a 12Db/octave high & low pass from what i can make out. The tweeter looks to be fed from an 18Db/octave high pass filter, interestingly the caps feeding the tweeter look like metalised plastic of some form or another.

The only nasties are on the mid & bass units. It looks like the mid is fed via a 24uf & 6uf in parallel & there is a cheapy directly accross the driver itself at 4uf (by the looks of things - from what i can see ).

If i was going to change anything it'd be the caps on the midrange, but seeing as you know the tweeter caps are of reasonable quality & not cheap reversible electrolytics you could upgrade those as well if you wanted to with no worries about ESR & phase shifts

Cheers, Mark - noted. However, I'd need to know the µF value of the relevant caps before proceeding any further

Marco.

[Marco]

Hi Nathan,

Just had a quick Google and apparently they are fairly inefficient 4ohm monsters requiring a bit of grunt. So your copper amp might not be up to the job.

Cheers for the info. Yes I read that somewhere, but I've also read the opposite and that they're pretty valve friendly. Experience with Celestion speakers from the same product line suggests that I'm more inclined to side with the latter view.

Furthermore, if a 40W Technics amp can drive them to ludicrous levels, I suspect that I don't have much to worry about. The Copper amp certainly drives the 15XRs with no problems whatsoever, and normally small speakers are much less efficient than larger ones.

However, if it is a problem, I'll just have to find a monster SS amp to partner them!

I'll let you know later if this proves to be a real issue or not

Marco.

[RochaCullen]

Yes it would be great to know how you get on.

Your mentioning that a Technics 40W amp can drive them sufficiently would make me think that you are right and that they are reasonably efficient. Having had myself a Technics 40W amp, I know how limited their power output can be. Plus, given the speakers come from the 70s, when amplifiers with serious grunt were not the vogue, you would not expect the Celestions to be to power hungry!

[Clive]

IIRC the output transformers on the copper amp are wound for 6 ohms. Should be fine.

[Rare Bird]

Got it, dude - cheers

When I get them, I'll double check that mine have those types of crossover boards. They should do, as the pic was taken from a site featuring early ones like mine with the black (non-veneered) fronts.

Mine definitely have the same terminals and face place as you indicated.

Regarding the crossovers, I've read that the later versions with the veneered fronts supposedly have improved crossovers (although some say they were just more complicated...), so I wondered if there was any truth in that?

Yes, the inductors look nice, so I'll leave those as they are.


Finally, mine are in a beautiful rich walnut finish, which seems quite rare, as all the other 66 Studio Monitors I've seen are in ubiquitous 70s teak... Do you know if that would've made them more expensive to buy originally? I know that more 'exotic' finishes on speakers, usually only available as a special option, often attract a premium price.

You may prefer the early crossover being hard wired, later were tracked PCB's.

Light woods are in fashion at the mo within housholds no? even said that i would always go for a light wood over dark anyday.

I don't think manufacturers played silly games trying to squeeze money out the punter with different finishes back then..you pay around £200 ish for a pair of '66's around '73 (just short of £2K today)

Actually they don't weigh anywhere near as much as you'd think, pretty easy to carry one on your own as i have found out They aren't bulky except in height.

I've had '66's in the past, a very late pair

http://theartofsound.net/forum/showt...?t=9028&page=5

They are not light at a guess 25-28Kg, not mega heavy buy carrying a pair from the car to the listerning room twice aint too pleasant especially if marco had a knackered back like mine..

[Marco]

Hi Clive,

IIRC the output transformers on the copper amp are wound for 6 ohms. Should be fine.

Yep, I was just about to post the same thing. The crossovers don't look overly complicated either, so I doubt I'll have anything to worry about

In fact, there's about the same in them as inside my 15" MGs, and they only have one dual-concentric driver, not multiple drive units, as per the Celestions.

Marco.

[Marco]

Hi dude,

You may prefer the early crossover being hard wired, later were tracked PCB's.

Yup, that was my thinking, too!

Light woods are in fashion at the mo within housholds no? even said that i would always go for a light wood over dark anyday.

Indeed, but only if you have a modern-style house. Whilst I like some light woods, they just look wrong in a period property like ours, or Wynn Hall, should we move there.

My real preference though is a nice mid to dark oak or walnut, as I like warm, rich wood finishes, finding 'blond' wood rather cold and incipid.

I love traditional wood panelling in period homes, so that's the look I like to create. If you look at the advert for Tannoy Westminsters in the current brochure for the Prestige range, that's my ideal kind of room

I don't think manufacturers played silly games trying to squeeze money out the punter with different finishes back then..you pay around £200 ish for a pair of '66's around '73 (just short of £2K today)

Fair enough, if that were the case, but I don't think there's any denying that the walnut finish is rarer than the teak, and thus more desirable to some.

I've had '66's in the past, a very late pair

http://theartofsound.net/forum/showt...?t=9028&page=5

They are not light at a guess 25-28Kg, not mega heavy buy carrying a pair from the car to the listerning room twice aint too pleasant especially if marco had a knackered back like mine..

Fortunately my back is ok when lifting a straight heavy weight. What I can't do (since my op after the removal of a non-malignant spinal tumour three years ago) is stand or kneel for very long, as part of the bone structure of my spine needed to be cut out in order to remove the tumour, so it's left me with some partial immobility.

Other than that though, and of course being not right in the head, I'm hunky-dory!

Marco.

[Reid Malenfant]

Ok Marco, you just knew i was going to perform operation 66

I can confirm that the values i gave earlier are correct

The capacitors fitted on the crossovers on my pair of 66s are different, but still film types. In my case the capacitors connected directly to the tweeter (top right of the picture) are both 3.3uf for a total of 6.6uf.

The capacitors connected to the speaker input feeding the tweeter (top left of picture) in my case are 6 x 0.68uf for a total of 4.08uf. I'd suggest 4uf is close enough & that on the picture they'd both be 2uf...