ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
I noticed some questionable notes on the differences between the S80, and the S80.2. On several locations it's said the only difference in these 2 models was the addition of post type input connections being added to the S80.2, in addition to the DIN types common to the Beovox brand.
However, I see the mid range dome is also different. The early S80 seems to have used a plastic or poly dome, and the S80.2 went to a cloth dome. Surely that would have resulted in a crossover change as well?
Does anyone know of a link for the specific crossover of the S80.2 model? All the ones I see are just for the S80, and I'd like to confirm the actual parts used.
I dissembled the Vifa tweeter on these by the way. They do use Ferrofluid, and they do have a dense felt domed pad to reduce back wave reflections. Not a bad tweeter at all; but run too hot, imo. I added a 2 ohm resistor in front of the input to the network for them. Required unsoldering the cap/resistor from the board, soldering them together above the board, and running the 2 ohm resistor to the input+ with the other end going to the cap/resistor. Something of a pain, but did reduce sibilants.
Please let me know if you know where I can see the actual S80.2 schematic.
Thank you.
The Beovox S80 and S80.2 differs greatly when it comes to the crossovers.The schematics and parts lists can be found in the service manuals.
Martin
Actually, I looked there, and it seems every other model is listed, but not the S80.2. Unless I'm missing it with these old eyes?
We do ask for a minimum membership level of silver to access the manuals etc. from the productssection of the main Beoworld website so, being a bronze member, I suppose you can't have looked there.
Thank you for the response. However, you can see what is listed there, you just can't download them. If what I wanted was listed, then I'd be tempted to become a member. All I really wanted was a schematic to confirm some of the parts values. I.e, the capacitors on the tweeter leg seemed to be 3.3uf in parallel with a 6.8 ohm resistor. And there was another capacitor that also looked like it was 3.3uf. That is something commonly done to provide lift in the response, and the only reason I can see for that is because of the first order, in-phase crossover topology. First order networks are difficult to implement because of the very large amount of driver overlap. A often overlooked problem with first order networks is what happens in the lobing. That lobing problem means that drivers often end up needing to be mounted in what appears to be upside down, where the woofer is above the mid, that is above the tweeter. See the Dynaudio Consequence and you'll see this rather bizarre looking arrangement. In the case of the Beovox S80.2, and it seems other models in their lineup; the woofer is canted up, relative to the mid/tweeter module. Then, the factory stands further tilt the entire speaker backwards. Listening as carefully as I could in near field, it appears the best driver integration is achieved with the speaker tilted, and between the woofer and the 75mm dome mid range. That places the tweeter away from ear level, which would result in the extreme highs being directed away from the optimum listening axis - hence the need for an other wise very linear tweeter response needing to be lifted so it's off axis remains more or less balanced when in the optimum listening axis of the speaker. I've also seen where this series is said to be of the "phase link" type. Not true. The idea behind the "Phase Link" approach, as I understand it, applies to second order networks, with the drivers connected in-phase with one another. That arrangement results in 180 degree phase angles between the drivers, or a NULL in the response. So, a Phase Link is a fill in driver, usually a first order bandpass, that fills in the NULL. It's not a perfect approach, and others have implemented similar techniques. It did do some things right, and it is a legitimate approach, however, I think the biggest benefit was marketing. All of which is of no importance here, as this was not a Phase Link design at all. Anyway - if someone has a copy of the crossover network I'd appreciate it. I just wanted to confirm the actual/original capacitors used on the tweeter leg, as mine had bad caps, and the values were nearly unreadable. Thank again for your input, it's always appreciated!
I can see that the Beovox S80-2 service manual has been listed as Beovox S80 by mistake.I have asked for it to be moved.But it IS in there, schematics and parts list.
I got for free a pair of foam rotted S80.2's. I also noticed that voicecoil was loose one of the midrange drivers, fixed that with epoxy. Replaced the foams and installed new oversized dust caps (90 mm). New dust caps are also made of fabric like old ones. However old dust caps have some kind of non breathable coating on them. New dust caps are breathable, does this affect the sound somehow?What is the purpose of this filter kind of material in the centre of magnet? The old material was brittle and I had to replace it with similar type.I measured the crossovers capacitors with LIMP and results are in the text file. I haven't done a lot LRC measurements so I don't know are the results good or bad.
The foam plug in the mid/woofer is there to prevent debris from getting into the motor structure. It may have a small effect on damping too, but it's so porous that it would be a minor reduction in Q.
The dust caps can be lightly coated with latex if you wish, Make sure it's an even coat. I'd probably do that myself as the woofer is already vented at the back, and keeping it air tight in front should slightly improve the bass response.
I obtained the schematic for this exact model, and there is an error. Since yours are apart, you can see what is incorrect in the official schematic. Take a look at the wires colors and lengths going to the tweeter. In the schematic, it shows the tweeter wired in the same polarity as the mid, and woofer.
However, see the wires! They are cut so that the tweeter is wired in opposite polarity from the mid!
In fact, if you try and reverse those leads, you'd need to lengthen one wire and cut the other. While this seems intuitively correct to keep "first order......" crossover topology, it actually will result in the tweeter and mid being out of phase at the crossover frequency. Try it if you wish - there is a very audible suckout in the upper mid range if you wire it, per the crossover schematic. Someone just made a small typo..
The tweeter circuit was changed on this model from the previous version. In the S.80, the capacitor going to the tweeter leg was 6.8 uf. In the S.80.2, it was changed to 3.3 uf., but the tweeters themselves are the same, or nearly so. The designer took into account the actual response curves of the mid range(changed in the two models)and made a wise choice in permitting an out of phase electrical filter, to put the acoustic sums "in phase". This also put lower demands on the tweeter.
I eventually swapped mine out to a later version of the Vifa tweeter; this one with a good sized cavity behind the dome to lower fs. I also ended up slightly padding it down with a 1.2 ohm resistor before the cap/resistor shunt that feeds the tweeter leg. I felt this necessary because the new tweeter was slightly more efficient then then the original.
This mod took away some of the sibilance the S-80.2 had that was bothering me, and smoothed the mid range through high range transition. It's actually a very fine sounding speaker with a little bsc of around 4 db(in my room), per Murphy calculations. Google for that if unfamiliar. Then, actively crossover to a good sub woofer system, and you'll be impressed!
btw - I hope you bought the exact replacement foam for those woofers? Nothing generic will fit right, or at least nothing I've come across did.
best wishes, and happy holidays!
oldtableman: btw - I hope you bought the exact replacement foam for those woofers? Nothing generic will fit right, or at least nothing I've come across did.
I bought the foams from Audiofriends. Model number is MSN-3/mk4FM. It's a generic model, but I think they fitted pretty well.
oldtableman: The dust caps can be lightly coated with latex if you wish, Make sure it's an even coat. I'd probably do that myself as the woofer is already vented at the back, and keeping it air tight in front should slightly improve the bass response.
Is it possible to use the glue that comes with the new foams (white, water based) to make coating on dust caps? Perhaps thin the glue 50 % with water.
I just looked at mine, and the original dustcaps are soft and are a slightly open weave fabric. I don't think coating them with PVA or similar is a particularly good idea. I'd keep them soft, and as close to original as possible. PVA will tend to be a bit firm when it sets, even if thinned. A rigid dust cap will effect the response in the drivers upper end, and could negatively effect the crossover to the 75mm dome mid range. Best bet - keep them as stock as possible.
oldtableman: I obtained the schematic for this exact model, and there is an error. Since yours are apart, you can see what is incorrect in the official schematic. Take a look at the wires colors and lengths going to the tweeter. In the schematic, it shows the tweeter wired in the same polarity as the mid, and woofer. However, see the wires! They are cut so that the tweeter is wired in opposite polarity from the mid! In fact, if you try and reverse those leads, you'd need to lengthen one wire and cut the other. While this seems intuitively correct to keep "first order......" crossover topology, it actually will result in the tweeter and mid being out of phase at the crossover frequency. Try it if you wish - there is a very audible suckout in the upper mid range if you wire it, per the crossover schematic. Someone just made a small typo..
I have the schematics well and I just checked the tweeter and mid wires. It looks like mine is wired exactly like in schematics, polarity is the same, am I right?