Falcon Acoustics re-introduce the Q7 MiniMonitor.

[Tony L]

Do the Q7s have the metal mesh dome grilles fitted to the T27s?

It seems clear the BBC weren’t entirely happy with the T27 as that mesh grille, the felt dispersion/diffraction controls and the tygan grille in combination would I’m sure alter it’s perfomance quite noticeably from Kef’s spec sheet. The LS3/5A cab having a recessed baffle and a grille-frame obviously dictates some correction, though many speakers of that era obviously didn’t bother. I guess the BBC approaching this design with such scientific discipline noticed every change and artefact clearly on response plots. It is interesting to contrast with the JR149 which lacks the mesh grille and only had its diffraction issues addressed with foam and deadsheet at a later stage (gold badge-era).

PS After spending more time with LS3/5As I’m finding myself agreeing with the consensus they need very little toe-in. They certainly give a bigger, wider, deeper soundstage firing something fairly close to straight at the back wall. How this fits with their measured dispersion plots I’ve no idea, just a subjective thing and one I’ve read quite often.

 

[MarkL56]

I'm a bit confused by some of this. Pretty sure when I ordered my Q7s the reasoning behind opting for the Tygan grilles was that the drivers were exactly the same as in the current Falcon LS3s, where Tygan plays an important part in balancing the sound?

Over time I've found that I prefer mine with no toe in

 

[TonyScarlett]

Many of the Falcons’ competitors ( if that’s the correct term ) don’t use a felt square around the tweeter.
The Graham Audio Chartwell LS3/5a comes to mind.
They are certainly superb loudspeakers.

Hi Martyn

Are you sure your not confusing the Graham Audio LS3/5A with the LS3/5? Just had a look at the Graham Audio website & the pic of the LS3/5A shows it with the felt square.

My understanding (although you will probably know better than me) is that the felt square was added by the BBC as part of the development of the LS3/5 into the 5A.

TS

 

[Martyn Miles]

Yes, Tony, you are correct.
I was thinking of the Graham 3/5.

I believe you are correct that the felt square was added, by the BBC, when the LS3/5
became the LS3/5a.

It’s interesting that the Harbeth P3-ESR doesn’t have any felt square.
Of course, the dispersion characteristics of tweeters are all slightly different.

 

[Tony L]

It’s interesting that the Harbeth P3-ESR doesn’t have any felt square.
Of course, the dispersion characteristics of tweeters are all slightly different.

The Harbeth has no connection whatsoever to the LS3/5A. It is an entirely different speaker of a similar size, and beyond that basic size there is absolutely nothing in common between the two speakers. Not one shared component. One key difference is the Harbeth baffle is not recessed into the cabinet, the clever metal grille frame sinks into a channel between the baffle and cabinet so there is no cabinet frame/grille frame diffraction issues to address.

 

[TonyScarlett]

PS After spending more time with LS3/5As I’m finding myself agreeing with the consensus they need very little toe-in. They certainly give a bigger, wider, deeper soundstage firing something fairly close to straight at the back wall. How this fits with their measured dispersion plots I’ve no idea, just a subjective thing and one I’ve read quite often.

Exactly my experience with the Stirling V3s, firing them straight at me just narrows & flattens the soundstage too much.

TS

 

[Martyn Miles]

The Harbeth has no connection whatsoever to the LS3/5A. It is an entirely different speaker of a similar size, and beyond that basic size there is absolutely nothing in common between the two speakers. Not one shared component. One key difference is the Harbeth baffle is not recessed into the cabinet, the clever metal grille frame sinks into a channel between the baffle and cabinet so there is no cabinet frame/grille frame diffraction issues to address.

Thanks, Tony.

I’d forgotten about the unique fixing of the grille on the Harbeth.

Going back to the LS3/5a and the felt squares, I read somewhere that the dispersion characteristics of the
T27 changed when fitted with the perforated grille.
That would make sense, as the T27 was ‘bare’ when used on the LS3/5.

 

[Tony L]

That would make sense, as the T27 was ‘bare’ when used on the LS3/5.

If I recall correctly it was one of the very early and different T27 used in the LS3/5, the most obvious difference being the lack of the two wires on the front of the plate. It was used in early Kef speakers. I’ve no idea why it wasn’t renamed as it looks like an entirely different driver, some details and pictures here (Kef).

 

[ToTo Man]

If I recall correctly it was one of the very early and different T27 used in the LS3/5, the most obvious difference being the lack of the two wires on the front of the plate. It was used in early Kef speakers. I’ve no idea why it wasn’t renamed as it looks like an entirely different driver, some details and pictures here (Kef).

AFAIK there were two versions of the earlier T27 6535 tweeter, the earliest had a clear mylar(?) dome and the second version had a black dome. Both domes were slightly recessed into the faceplate, unlike the T27 SP1032 which has the dome sitting proud of the face plate.

Clear T27 6535:

Black T27 6535:

T27 SP1032:

 

[Tony L]

AFAIK there were two versions of the earlier T27 6535 tweeter, the earliest had a clear mylar(?) dome and the second version had a black dome. Both domes were slightly recessed into the faceplate, unlike the T27 SP1032 which has the dome sitting proud of the face plate.

Yes, that’s my understanding too.

I guess the thing with Kef is to ignore the first part of the model number, e.g. T27 just means it is one of a range of tweeters (and not even a 27mm one!), a B110 a bass mid (127mm!). It is the SPxxxx number that identifies the actual unit and its specification. Their numbering makes far less sense than I once assumed. The Kef .pdf I link to above is very useful and explains a lot. One to save for future reference.

 

[Martyn Miles]

I wonder how the dispersion characteristics of modern tweeters ( Seas, etc. ) as used by Harbeth,
Graham and Stirling compare with the T27.

 

[AmadeusMozart]

I wish the Q7s I had on home demo had been supplied with Tygan grilles in addition to the stock shear grilles as I'd have been able to measure them to confirm exactly how much more HF they attenuate. Perhaps another Q7 owner is in a position to perform such a measurement?

@raysablade, if the grille frame is deep enough you could perhaps cut a thin piece of acoustically-transparent foam to size and push it into place behind the shear fabric to make the fabric appear more opaque? 5mm might be too thick but I've seen acoustically-transparent foam as thin as 3mm, though 5mm is easier to source.

FWIW
The grilles are not as deep as on the LS3/5A so the standard LS3/5A felt pads don't fit. The grilles also have a bit of a "step" on the driver side so there is little to be gained with felt squares. I also found a study from someone who stated that after extensive testing a felt cover has to be at least 1/4" high (thick). If it is 1/8" then actually the performance gets worse. It also has to be pure wool felt, anything synthetic will not work. Plus the felt had to stop at the edge of the tweeter, not close to the dome.

Jerry does not have felt pads on his own Q7 speakers.

Re Tygan: it is thicker but still some reflection of light on the woofer is ever so slightly noticeable under certain angle / light. I like the looks and that it is a thicker material and that the grille sticks about 1/32" out from the veneered edge.

Speech intelligibility has improved considerably (for me) but they'll show up bad recordings and mediocre sources quickly.

 

[Yank]

AFAIK there were two versions of the earlier T27 6535 tweeter, the earliest had a clear mylar(?) dome and the second version had a black dome. Both domes were slightly recessed into the faceplate, unlike the T27 SP1032 which has the dome sitting proud of the face plate.

Clear T27 6535:

Black T27 6535:

T27 SP1032:

Back in the 1970s one of the popular modifications to the T27 SP1032 was to remove the black coating from the diaphragm and surround. It came off easily with a cotton swab and some carbon tetrachloride, or 1,1,1 trichloroethane.

 

[Yank]

Yes, that’s my understanding too.

I guess the thing with Kef is to ignore the first part of the model number, e.g. T27 just means it is one of a range of tweeters (and not even a 27mm one!), a B110 a bass mid (127mm!). It is the SPxxxx number that identifies the actual unit and its specification. Their numbering makes far less sense than I once assumed. The Kef .pdf I link to above is very useful and explains a lot. One to save for future reference.

Re: the T27, I think the diaphragm and motor were essentially the same for the three versions shown above, the difference is in the faceplate and the diaphragm coating.

 

[Martyn Miles]

I used a pair of unused SP6535 T27s when building a pair of replica LS3/5s.
They had black domes.
They sounded excellent in conjunction with the B110s and the appropriate crossovers.

 

[AmadeusMozart]

I used a pair of unused SP6535 T27s when building a pair of replica LS3/5s.
They had black domes.
They sounded excellent in conjunction with the B110s and the appropriate crossovers.

Long time ago I build the Kef Constructor series CS1 and CS1A. (Documentation can still be found online.) KEF offered these as a "lower cost DIY" alternative to the KEF 101 (which in itself was an alternative to the LS3/5A).

On one of these the B110 mid/woofer is in the front, the other has the B110 at the back of the baffle. I could not hear a difference between them but... due to the B110 being mounted on different sides of the baffle the CS1 and CS1A had different crossovers.

RE: Comparing the T27 tweeter to Seas etc. as used by other vendors: I feel the Seas may be (is?) a better tweeter but then it no longer will be an LS3/5A in spirit and execution where the emphasis is on orginal reproduction with all its warts and all, both physically and audible.

@Tony L I wonder if the metal grille on the T27 was initially added as a protection for the front mounted diafragm since the LS3/5A was intended to be used in broadcast vans.

 

[Martyn Miles]

Tony.
I understand the tweeter grille was initially fitted for protection, during rigging, an article stated.
The idea of LS3/5a in a rig is stretching things...

 

[Yank]

My understanding is that the tweeter screen was sourced from Celestion, it's from their HF2000.

 

[Martyn Miles]

You are correct.

 

[ToTo Man]

And right on cue; below shows the effect the perforated brass grille has on an HF2000. It gives a +3dB boost in output between 10kHz-15kHz.

I had the good fortune of acquiring a handful of new old stock HF2000 units last year (from Texas of all places!). I took a leap of faith as they were an untested barn find. It appears they enjoyed the dry Texan climate as 75% of the units tested were a perfect match to within fractions of a dB, I honestly could not believe it! Unfortunately all of the grilles had come unstuck but it shouldn't be too much trouble re-attaching them.