Twin-coned speakers

[Edward Huggins]

I have always had a soft spot for these. I enjoy the point source sound they always offer and the complete absence of any need for a crossover unit, with their attendant disadvantages - cost, phase shift, insertion loss et al.
Many years ago, as with others I'm sure, loved those ELAC or Wharfedale 8" and 10" twin cone, roll-surround, units mounted in largish reflex enclosures.
Of course, they did not provide a true treble that one might associate with a dedicated Tweeter, but gave out what I would call a high mid-range with a natural roll off at about 8KHz. To my now failing (HF) ears these still sound
re-assuringly endearing....
What are other Members memories of these in their hey day and, maybe, even now? That's always assuming you can still source those, once plentiful, driver units!

[kalee20]

I like them. Though they do have their drawbacks.

Feed a high-frequency signal and a low-frequency signal in at the same time, and with the best linearity in the world, there will be intermodulation, thanks to Mr Doppler. And the resultant frequency modulation of the HF by the LF creates a complex set of sidebands.

Splitting the frequency ranges does reduce this effect.

I listen to the spoken word a lot, radio plays etc. and use small DC4 Tannoys for stereo jobs, nearly the same but with a co-axial tweeter (with a crossover and ingenious phase stuff too). And it really does make a difference in the accuracy of the "sound stage" having them (low/high frequencies) on the same axis. With some well produced/engineered plays the actors walk about in the room (my room), marvellous!

[Trevor]

Wharfdale super 8 and Goodmans Axiet 8 come to mind at normal signal levels great
But the very best is the Lowther series had a pair for 10 years superb
single units can be stunning
I have owned all these during my life in audio
Trev

[Boulevardier]

I remember how good they could sound. My first "reasonable" speaker was a Fane 8" with roll-surround and twin cones. I built a bass-reflex cabinet for it following the design by Goodmans in their booklet for constructors. It sounded very good indeed (though only mono). A rather over-sensitive friend of mine nearly passed out with lust when he heard the breathy Francoise Hardie played through it.

Mike

Originally Posted by Edward Huggins

I
Many years ago, as with others I'm sure, loved those ELAC or Wharfedale 8" and 10" twin cone, roll-surround, units mounted in largish reflex enclosures.

[Whaam68]

Coincidentally I brought a pair of super 8 RS/AL down from the loft in my lunch break today. I’m finishing off a low power valve amp and as I got a new circular saw for my Birthday from the missus. I thought to build the 1 cu ft reflex or distributed port enclosure from Gilbert Briggs cabinet handbook. The drivers dated 1967 have been up there for some years in a box wrapped in plastic. I thought I’d best test them and the one on the right didn’t take kindly to a bit of riders on the Storm at low power as the foam backing to the whizzer cone just immediately crumbled to dust before my eyes. The other is equally fragile. I’ve ordered some open cell foam to re build that and some liquid latex to coat the back of the surrounds which are porous.

I did once have a set of Lowther PM6A in an old pair of Acousta cabinets but I could never really get the bottom end in those cabs and sold them on. Wish I’d kept the drivers and persevered now but there you go.
Mike

[rontech]

My first high fidelity loudspeaker was a Goodmans Axiom MkII with hefty alnico magnet. I made a large corner cabinet using two adjacent brick corner walls in my parents lounge. The front panel was double skinned and filled with dry sea sand. Also fitted the correct Goodmans "Acoustic Resistance Aperture in the front. It sounded pretty impressive at the time ( 1957 )

[G6Tanuki]

I never really understood the 2-cones-on-one-driver-coil thing: pragmatically the little-cone's ability-to-move-fast (as needed to deliver sane HF response) will be horribly compromised by the inertial-mass damping of the big cone.

I much preferred the mentality of "2-in-1" speakers where a 6x4 LF driver had a little HF unit hung in its centre and fed either from the HF-side of a crossover or - preferably - from a separate HF amplifier-chain.

[Disclosure: I don't have 'golden ears' - my hearing-below-300Hz was trashed in an explosion so I only get to bodily ~~feel~~ the bassline through my lungs and bowels]

[LeakyGrid]

Back in mono days, I was always very pleased with my Goodmans Twin Axiom 10. I had it in a large home-built floor-standing single port reflex enclosure, and it was driven by a Williamson amp. It sounded great to me, the first hi-fi setup I'd ever had.

Roger

[mhennessy]

Originally Posted by G6Tanuki

I never really understood the 2-cones-on-one-driver-coil thing: pragmatically the little-cone's ability-to-move-fast (as needed to deliver sane HF response) will be horribly compromised by the inertial-mass damping of the big cone.

Effectively, twin-cone speakers have a mechanical crossover. The connection between the voice coil former and the larger diaphragm allows the former (in both senses of the word!) to move somewhat independently of the latter, enabling the "whizzer" to produce high(ish) frequencies.

This idea of decoupling at high frequencies is very common. If you've ever seen a diaphragm with rings embossed into it, that's why. And even if there isn't an obvious method, the profile of the diaphragm will allow the inner sections to move faster than the whole thing. A lot of research has been done in this area over the decades, but there still remains an element of black magic (or luck!).

Originally Posted by Edward Huggins

I have always had a soft spot for these. I enjoy the point source sound they always offer and the complete absence of any need for a crossover unit, with their attendant disadvantages - cost, phase shift, insertion loss et al.

A well-designed crossover is not something to be feared. A speaker - like just anything - is a bunch of compromises, but in my experience, the potential advantages of full-range speakers do not outweigh their problems. I've heard quite a lot, including some extremely expensive current designs, and none of them have performed better than a decent 2-way. Quite the reverse, in fact.

Of course, there are plenty of full-range speakers that are very pleasant and enjoyable. But that's nothing to do with your list of alleged crossover disadvantages. I have attempted to explain this in the past, and am happy to try again, but in short, cost aside, those "disadvantages" are actually essential elements of how they work, and are what enable you to design a system that will measure and sound better than a full-range driver. Without "insertion loss", how can you equalise the system? And just to be clear, the insertion loss of a crossover is a tiny fraction of a dB in the areas where it's not equalising out unwanted rising responses, such as down at the bass end.

If you can live without bass extension, there are some very nice 2-4" drive units around. But as you go up in diameter, things get much harder to manage, especially the power response (the combination of the on-axis and off-axis response).

I've heard a few good coaxial systems. These are a lot better than a "whizzer" setup, but even so, the ones I've heard did not image any better (and often not as good) than a good 2-way. The "point source" idea is very appealing and people intuitively think it should improve the stereo image, but in reality, the main advantage of a coaxial setup is better power response (because the off-axis response is more uniform as you move the mic around the drive unit).

One area where older speakers often win is sensitivity - that's because the paper diaphragms are relatively light compared to more modern materials. But sadly they are not very well damped, so have many resonant modes - which causes the frequency response to be all over the place (along with the associated phase shifts). Modern diaphragms have much better damping, so exhibit much smoother frequency responses, but are less efficient as a result.

If you're lucky, the peaks and troughs fall in the right places, and you've got something that sounds pleasant. But the opposite could easily happen. Speaker design involved a lot of luck in the good old days!

[Edward Huggins]

Thanks for this detail. I can't dissagree with anything you say here. In my long experience of acoustics it all makes perfect sense. I only make mention of these twin-cone units as I just enjoyed, and still enjoy, the nostaglic and coloured sound they make. And the hours of fun and learning I had over countless experiments and variations with traditional wooden cabinets, omni-diectional columns and pipe designs....
Of course they can never be compared to co-axial or seperate twin (or more) drive units.

[Restoration73]

Wharfedale did sell a cabinet version 8" TC - the Chevin. It was smaller than the
Denton, 300 x 220. Sounds fine for a small bookshelf.

[Beobloke]

Other than a couple of notable exceptions such as the Goodmans Axiom 201/301/401, my opinion of twin-coned loudspeakers is that they are an utter abomination and only suitable for use in the bottom of car doors and firing at your ankles.

But that’s just me...

[Radio Wrangler]

Dual-cone speakers DO have a crossover. It's mechanical and relies on floppiness in the main cone as well as the relative masses and air loads. Whether this is better or worse than doing it with inductors and capacitors would be an interesting debate. I think it has fewer freedoms. At least it's concentric!

David

[mhennessy]

Post #13 reminds me that the simple full-range units in my last car were surprisingly good - more than good enough for car audio. The same drive units in my wife's last car were not as nice, but it was a different model with different door mouldings and rather more cabin noise. My current car has the Harmon Kardon 16 unit setup, and honestly, it's not that much better (and worse in some areas, especially at the bass end). My wife's current car with the standard 6 speaker setup is probably better overall, perhaps surprisingly.

If nothing else, this illustrates the difficulties of generalisations

At least a car audio designer has the advantage of a relatively fixed environment and he or she knows where all of the ears will be located. But hi-fi speakers can be plonked just about anywhere in rooms of all sizes, and this is the main thing keeping designers awake at night!

[Trevor]

The Barker Duode loudspeaker comes to mind a composite cone with a bakelite harden cone section and a rubber decoupled voice coil on a aluminium former
I would loved to have heard one of these
Trev

[unitaudio]

I have a pair of Wharfedale Chevins Which cost me £3. They're in very good condition and sound pleasant enough.

I'll be honest and say I'd feel a bit hard done by if they were my only speakers. The treble is a bit soft, predictably enough and the small cabinets don't allow for much in the way of deep bass but I'd seen them in old magazines and was interested in them to the point I felt I had to try them out for £3.

I wasn't disappointed and used them on my bedroom system for about a year. Overall I prefer the EMI 13"x8" twin cones I used back in the 80's. These can give quite a decent account of themselves if they're fitted in good cabinets.

The thing I love about twin cone speakers is that occasionally you come across one that punches well above it's weight. It's just a shame they're not as common as they once were. For a cash-strapped teenager, twin cones were often the only affordable way to obtain anything even approaching an acceptible sound.

Regards,
Paul

[Max Ripple]

I too have fond memories of the EMI 13"x8" drive units.They seemed to be readily available at sensible cost during the late sixties,early seventies.
I was able to put together audio systems for college mates,that sounded pretty good.
A smaller version of the drive unit was employed in my Dad's Ferguson stereogram,and combined with the large area of the cabinet,the sound was great.
I recentley refurbished the Ferguson unit,and with a replacement BSR pu for the original expired Ronnette pu,I was still impressed after all these years.
Nick

[Radio Wrangler]

But the posher EMI 13.5x8 inch units dispensed with the whizzer and mounted a pair of tweeters on a bridge in front of the main cone.

David

[Ted Kendall]

The B&W DM1 used a modified version of the EMI 13x8 to very good effect - albeit without the tweeters and with a lot of damping on the main cone.