General Forum

Re: Beovox s80.2 and other speakers from mid 80's

ouverture — Sat, 07 Mar 2009 13:20:48 GMT

I think one of the nicest amps that sounds really good with the S80.2's is the Beolab 5000 from way back in 1967

http://www.beoworld.org/prod_details.asp?pid=383

but any of the Beomaster 5000, 5500, 6000, 6500 and 7000 models drive these speakers pretty well IMHO !

NB Beomaster 5500, 6500 and 7000

If you have owned a lot of B&O equipment then you will have probably noticed that these 3 Beomaster models give a slightly disappointing sound when used with passive loudspeakers and when compared to some of the earlier designs. This is surprising as the power amplifier circuit is very similar to that of the Beomaster 5000 and the Beocenter 7700 (amongst many others), all of which give very satisfactory performance.

The Beomaster 5500, 6500 and 7000 have a rather basic pre-amplifier circuit compared to that used in the original 5000 model but this is not the cause of the problems, the same arrangement is used in the Beocenter 9000 where it seems to work pretty well. Therefore the power amplifier circuit was investigated to see what could be causing the trouble.

The only substantial difference between the Beomaster 5000 circuit and that used in the later models is the addition of four 220nF capacitors C215, C216, C415 and C416. They are not shown on all the Beomaster 5500 circuit diagrams but many sets have them. As these do not appear in any other versions of the circuit it seemed safe to remove them and see if the performance improved. With the capacitors in circuit the sound from one Beomaster 5500 was lifeless, bland and uninteresting, without them it was more similar to the 5000, engaging and lively with a full, rich tone.

It is not clear what the purpose of these capacitors is but performance definitely improves if they are removed. Before doing this make sure that the muting relay 3RL1 is in good condition (contact resistance less than 0.5R at rest) and that the output bias current for each channel is correctly set.

Re: Beovox s80.2 and other speakers from mid 80's

Peter — Fri, 20 Feb 2009 01:57:38 GMT

Thank you for that! Having just heard a properly set up pair of S80.2s, it did seem likely that yours had an anomaly! Have you done another frequency sweep?

The 4400/6000 is a good design of amplifier and well worth a look. The 1500 and 2200 are much the same design electronically but less powerful and would be extremely cheap - affordable enough just to have a play with! The 2200 in particular is a fascinating receiver and almost completely forgotten.

Re: Beovox s80.2 and other speakers from mid 80's

Martin Gajta — Thu, 19 Feb 2009 22:05:53 GMT

Just in a case that you care,some drivers in my boxes were connected out of phase (mid frequency driver) so there was much canceling in those boxes since there is big overlap between 8" and 3" speaker and since they were out of phase almost whole spectar missed.Also there was some cancelation between mid and hi frequency speaker and that's the reason for hole in 4k section.

Good thing that came out of this is that I started to think about beomaster 5000 or 6000,and now my problem is solved BUT I'm still thinking about some B&O amp.

B&O not only in frequency domain rule but in also in phase...

Thanks to everyone of you that responsed so quickly

Martin Gajta

Re: Beovox s80.2 and other speakers from mid 80's

Peter — Wed, 18 Feb 2009 01:38:59 GMT

The 6000 seems a bit more delicate than the 4400. These are not that tricky to take apart so armed with some equipment, they are fixable. Martin does capacitor kits.

Re: Beovox s80.2 and other speakers from mid 80's

j0hnbarker — Tue, 17 Feb 2009 18:39:53 GMT

Peter :

The 6000 is a good one as John says though rather prone to blowing one channel. My favourite is the 4400 but that too will probably need a little love and attention as it will be about 30 years old.

Isn't the 6000 a derivative of the 4400 Peter? I suppose it depends on the OP's personal prefs regarding looks. There's a progression through 4400/6000/5000 series in terms of acceptability in modern interiors, from 'vintage' 4400 to 'contemporary' 5000 series. Either way any of these will probably need some work nowadays, and it's a shame that there's only a handful of people able to work on these units, given that most of the components can be replaced if required.

Re: Beovox s80.2 and other speakers from mid 80's

Peter — Tue, 17 Feb 2009 18:23:56 GMT

I would suggest having a look at the cross over in the S80s. I dare say some replacing of capacitors could be in order. B&O speakers should offer a reasonably flat response - the amplifiers certainly do. I attach the responses of my MS150s as measured professionally.

The best amplifier depends really on what you want. The 6000 is a good one as John says though rather prone to blowing one channel. My favourite is the 4400 but that too will probably need a little love and attention as it will be about 30 years old.

Re: Beovox s80.2 and other speakers from mid 80's

j0hnbarker — Tue, 17 Feb 2009 18:08:44 GMT

Martin

The road is long, and the arguments well rehearsed regarding what's the best amp in 80s Beomasters/Beocenters, suffice to say that of those you list (5000/5500/6500/7000) there is a clear but slight preference for the amp in the 5000 as having the edge. Have a search on the forum and you'll find various threads on this topic. For what it's worth I'd say that a good match for S80s would be a Beomaster 6000 (I own one and use it with MC120.2s and it's a nice sounding amp that I've never heard a bad word said about on this forum).

Beovox s80.2 and other speakers from mid 80's

Martin Gajta — Tue, 17 Feb 2009 18:02:10 GMT

I have these speakers few months and first thing I did was to measure them (I used smaart6) and one thing that I heard first and then confirm in measurements is that my speakers have boost in upper frequency section and big hole in mid bass part.It is surprisingly good in 40hz region tho.

My question is:are B&O amplifiers flat or do they have some kind of equalization to match speakers,since speakers are far from flat.I was thinking on buying beomaster 5000,6000,6500 or something similar.In pic you may see Tannoy dmt 215 (pale blue),quested (pink) and Beovox s80.2 dark blue.

Thank you

Martin Gajta