Tweaking Sextets.

The Sextets are 36" high by 7½" deep by 10½" wide, the midrange enclosure has the top 10" or so of that cabinet.
Wood seems to be roughly ¾" chipboard, heavily braced with stapled/glued panels and the bass/midrange cabinet divider. The attached picture shows the driver layout.

[planet10]

The tweak i was going to suggest is not applicable then...

I saw further up mention that the ribbon is a Tonegen -- it sure looks like a set of Foster ribbons i have. Any chance of a pic of the backside?

dave

No problems.
No picture, but the back of the magnet is 3" by 2 " and has EMIT-0500 written on it, the plastic frame is 12cm wide by 10 cm high. The ribbon measures 52mm by 12mm.

[jarmusch]

hi,
I am a newbie here so first greetings to you all from Hungary
now, I am a happy owner of a just recently acquired pair of Sextets - they're simply amazing. I have had several speakers before but they are truly musical performers standing highly proud of the crowd - great job the designers did, I must say.
I, however, have some questions - hence I mainly joined the forum.
that is, I am unaware of my Sextets' model identity. I wonder if anyone could help judge it? S/N are 728207 1122/17 and 18 if this helps, and they just look like any other Sextets, albeit perhaps with a slightly smaller woofer (16.5cm) with a pointed pole piece than the minority of their peers, as it appears on the available photos from the net, and there is no switch on the back for the tweeter.
also, in the X-over, which is surely untouched, the resistor on the bass circuit is 15 Ohms, and there is a blue elko on the mid circuit the value of which, just as of all the yellow polpypropylen (?) caps', which actually look to be ICWs, can't be read for them being (purposefully?) mounted with the values facing down.
moreover, I am okay with these PP caps but feel that that lone elko should be replaced for a new one, or for a PP equivalent, to make sure it won't start to leak.
furthermore, as I see the resistor value on the bass circuit is only 8 Ohms for the MkIV version I wonder what happens if I lower the value of the now existing 15 Ohms one? to note, I have no problem with the bass, just really am curious.
please advise - your input will be much appreciated

Hi,
I would also like to tweak my Heybrook Sextets and think I have the same version as Jarsmuch;as far as i can see the crossover is:
bass: 2.2uf IWC and 15 ohms (brown green, black, gold) with a coil (across them?)
Mid: 60uf electrolytic and two 4.7 and a 2.2uf IWC in parallel making 71.6uf total in parallel across the unit
HF: 2.2uf and 2.2 ohms (red red black silver gold) in series.

I would also like more bass - should i reduce the resistor - maybe by adding another 15 ohms in parallel to halve the resistance? I have no idea how the coil affects that calculation though.... can anyone help please? I have replaced the electrolytic with a solen and have some claritycap ESAs for the rest which i have not yet fitted..

many thanks, Nigel

[Black Stuart]

jarmusch/Nigel,
I have the MK1V version and have used them continuously for over 15 years now, so it's probably time I had a look at the x/over components. I hav'nt bothered because I intend to replace the passive for an active x/over quite soon.

Nigel, I'm not sure you can get much more bass from these speakers, the woofers are quite small after all. In fact I'm impressed with the amount of bass they produce - how about using a centre sub-bass unit to back up what's there.

Passive x/overs are way out of date, the theoretical basis for active x/overs are undeniable and listening to speakers with active x/overs is totally convincing.

Check out Rod Elliot's ESP site and his excellent passive v active x/over article. He also sells a PCB and you have access to software to determine values - you will also find that an active x/over is far cheaper to produce than uprating a passive one.

The Tonigen tweeters are wonderful, so clear and detailed I could not imagine using anything other than a ribbon at the top end in a speaker. Sometime soon I will get round to using the Grand Heils (thank you Andrew) that I have had for some time now.

[Alex Kitic]

jarmusch/Nigel,

after acquiring my Sextet speakers (in 1997 approximately), I have immediately replaced the internal "mkI" wiring - particularly thin wires for mid and tweeter - for VdH CS6 wires... and that was it, I just used them as they are.

With any amplifier connected, they impart a specific character to the sound we might call "mid-forward". Fortunately, its a very good mid... but it is forward, and imparts its own character on the system.

I have checked on the crossover as posted in this thread, and mine is actually different, i.e. identical to the crossover in the jarmusch/Nigel owned speakers. I am reattaching the crossover schematics with my values written in different font below the values of the original file.

Sextet_Mk4_Crossover.jpg

The large coil I have not checked for value, but I guess that it is as expected, which means the bass is cut at 880Hz (1.45mH), while the mid starts from approximately 280Hz (71.6uF). The 2.2uF in series with 15 ohms is the Zobel network correcting the impedance...

The most important detail is that since the other inductance is missing (0.35mH) the mid is left uncut, exploiting its gradual fall-off. And it goes quite high, since with the tweeter disconnected (the other connection on the biwire posts is for the tweeter alone) on axis it should be at 6.5kHz just -3dB below...

The Tonegen tweeter is cut very high, 2.2uF means 8.8kHz! I would call that "super-tweeter" behaviour. The 2.2 ohm resistor "attenuates it" a little, and serves the purpose of a fuse (that is why it is a 250mW MF unit).

Well, what I would suggest you to do is add a resistor of 1.5 ohms (5W) in series with the mid (the easiest point to add it is the black wire, starting from the caps). What will happen is recessing the midrange some 1.5dB in the lowest impedance area, between 300Hz and 800Hz, which is the area where it combines with the woofer output. This will tame most of the mid-forwardness, while leaving all the high frequency "shine".

Two small resistors for a very relevant difference in sound. What do you think?

[Alex Kitic]

I forgot to mention that you should fill the midrange cabinet with additional material, but I guess that is trick No. 1, or what everyone would usually do...

Strangely enough, one would expect that the resistor lowers speakers efficiency, but as a matter of fact I am able to play louder undistorted levels than before.

[Alex Kitic]

After some more tweaking, I have found the best and most cost effective solution.

1)
The midrange is cut too low. Remove 60uF electrolytic cap, the resulting value is almost 12uF of polypropylene caps, for a cutting frequency of 1600 Hz approximately. Yes, the bass was already cut at 880Hz, but do not let that scare you...

2)
The bass may sound a little recessed without the contribution of the mid in the 200 to 1k region. The simple resistor trick alters the impedance of the midrange and creates a peak in mid-high frequency (rising).
Adding a 23.5 ohm resistor across the midrange (immediately after the 1.5 ohm resistor in series, creating an L pad) causes the midrange to lower about 2.2 dB, without change in impedance and peaks in mid-high frequency.

3)
Now the bass is more accentuated in comparison to the midrange, but the speakers are slightly "mute" sounding. Add a good polypropylene cap across the 2.2uF in the tweeter network, between 1.5 and 2.2uF in value (I added 1.5uF 250V).
This lowers the cutting frequency of the tweeter from the rather absurd 8800 Hz to a more "reasonable" 5.5kHz.

The result is change in character. This is not a British cottage industry sounding-like speaker any more. Slightly recessed midrange, slightly bassy character, great mid-highs (ribbon tweeter at its best). High-Endish sound if you'd agree.

[Alex Kitic]

One last touch to the remodeled crossover:

With some recordings it might seem that there is too much "shine" and detail, thus I have first added an L-pad (instead of the simple 2.2 ohm resistor in series) with 2.7 ohms series and 15.6 ohms parallel, reducing tweeter output for 3.6dB with normalized impedance to the nominal 8 ohms(was 2.1 db and 10.19 ohms impedance).

This did indeed reduce the shine, but also made it sound a little "too bland" for my taste. Midrange again in evidence: while blending with the midrange has improved, this has also brought the midrange back where it used to be...

Thus a final touch represented by a 1.5 ohm resistor that can also be applied outside the box, instead of the bi-wiring bridge, preferably on the negative connectors. If you like it better that way, you can always install it inside on the crossover...

The result is additional reduction in tweeter output (to approximately 4.5dB) but this time with an impedance rise to the (almost like the starting position) 9.8 ohms (approximately - somewhere between 9.5 and 10 ohms). It seems that the tweeter "likes" to be used with a resistor in series: the sound is not at all "laid back", but for one reason or the other, the mid-range is again pushed back from the first row which is exactly why we started all this.

You cannot improve the bass output all that much - but you can achieve a more "American", or High-End-ish sound by reducing the output of the mid-range and contrasting it with the tweeter... I guess that is what they call psycho-acoustics.

Of course, it is possible that some might just like the original sound... but whoever started this thread obviously was not all that happy with the sound out of the box - and all those Sextet speakers are by now at least 20 years old, it is time to do something about their sound