[RossJP]

I have a problem where when I turn the volume up loud, it seems to drop back down very quickly, and it seems like it also taking all the bass out. It then stays at the lower, thinner, level.

I recently bought a Beocenter 9500 to replace my previous Beomaster. I have it connected to a pair of Beovox 5700 and a pair of Redlines. It does this on aux (bluetooth), on phono (beogram), and on onboard CD.

If you play a song loud which gets louder part-way through, the system kills the volume at this point too. It doesn’t “recover” afterward, not till it’s been turned off & on.

Does anyone know is this normal? Am I just expecting too much? My lounge is only about 6 x 7m, and I only want it loud once in a while, but it seems disappointing for something that looks so good, and I’m sure my old Beomaster didn’t do this. Is this just a more advanced self-protection system?

If this is the genuine limit of the 9500 amps then I am thinking I should get some Beolabs to get the volume I want. I will miss the 5700s though, I’ve had them for over 20 years and they look and sound great.

Apologies for joining the forum and then asking for help straight away!

[Guy]

Hi and welcome to Beoworld!

I have definitely experienced a similar automatic volume reduction when using my BC9500 to drive a pair of passive Audiorama 8000 speakers – I assumed that it was due to some sort of overload protection although I can’t find this documented anywhere. (I will have a search of the archived forums to see if I can find anything.) I didn’t have to switch my BC9500 off/on to reset it – turning the volume down resolved the problem.

Instead of getting BeoLabs, one quick and easy way to reduce the load would be to get hold of a secondhand B&O Passive which could be used as an ‘off-board’ amp for one of the pairs of speakers. This could simply be connected to one of the BC9500s Powerlink outputs and would automatically turn on with the main unit.

Are you using both sets of speakers in the same room?

EDIT: I found this in the service manual – the protection circuit loops back to the microprocessor where it is labelled ‘Power Down’ which I would interpret to mean power reduced, rather than power off (but I could be wrong!):

EDIT2: There can also be problems with the Mute Relay (poor contacts giving poor/low sound), but this would only affect the sound from the Speaker 1 sockets (the relay is 3 RL 1 in the diagram above).

[RossJP]

Thanks Guy, for your very helpful reply. I had missed that in the manual, but think I was searching in the schematic rather than the block diagram for clues. That would make sense then.

I had thought about the Passive (amp) units, but they are are only 3oW so probably not up to what I sometimes want.

The speakers are all in the same room. I have the big 5700s up front on channel 1 and the smaller Redlines (45 I think) wall mounted at the rear on channel 2. I can test if it’s related to the mute relay by only using the 5700s and putting them on channel 2, then see if the problem still happens.

 

 

[Glitch]

RossJP wrote:

Does anyone know is this normal? Am I just expecting too much?

You are probably expecting too much. Based on a quick search, the BC9500 appears to be only rated at 8 ohms. This typically means that the manufacturer expects you to hookup either one or two pairs of 8 ohm speakers. Running two pairs of 8 ohm speakers is roughly equivalent to running one pair of 4 ohm speakers (assuming the internal connections are in parallel). With this in mind, you shouldn’t have any issues running just your BV5700’s (which are 4 ohm) or just your Redlines (which are 8 ohm?).

The problem is when you try to run both, the equivalent impedance is roughly 2.7 ohms. Usually, one can get away with this as long as you keep the volume low, but this configuration is (probably) not how the receiver was intended to be used.

Are you having any issues running only one pair of speakers at a time?

If you don’t have any issues with running the BV5700’s by themselves, then the BC9500 is likely working properly. If you still have issues while running one pair, then they may be something else that needs to be addressed.

I wouldn’t recommend mixing different impedance speakers on the same amp from a sound level perspective. You may have noticed that one pair of speakers plays louder than the other. Matching the speaker’s impedance (and efficiency) will usually result in a better overall listening experience.

Glitch

 

[RossJP]

I have just tried only the 5700 speakers, and on channel 2. It no longer drops volume at at full volume. Actually it might have a little with louder songs, but nowhere near as pronounced.

So maybe I’ll keep the 5700s up front and get some smaller Beolabs for the rear.

[Guy]

RossJP wrote:

I have just tried only the 5700 speakers, and on channel 2. It no longer drops volume at at full volume. Actually it might have a little with louder songs, but nowhere near as pronounced.

If the mute relay is fine then the ‘speakers 1’ connection should be fine also, so that is worth trying just to be sure. (But faulty mute relay symptoms are usually a little different – often cutting out at low volumes until the volume is increased and then the mute relay jumps into action and the sound blares out!)

I would still consider experimenting with a Passive for your RL45s – you can pick them up for about £30 and sell for no loss if you don’t use it! This would leave the BC9500 to just drive the 5700s.

This is not my advert but I have bought from the seller before: https://www.ebay.co.uk/itm/145245293217

[Glitch]

RossJP wrote:

So maybe I’ll keep the 5700s up front and get some smaller Beolabs for the rear.

You will likely have the same issues with “smaller Beolabs for the rear”. The root of the problem is that the low impedance configuration that you are trying to run is pushing the BC9500 past its design limit.

How loud are you trying to achieve? I would expect that the BC9500/BV5700 would get pretty loud (louder than most people would want to listen).

Of course, “loud” is a relative term. Consider buying an inexpensive decibel sound level meter. This will give you a better idea of how loud things are actually getting. I use mine as a way to protect my precious hearing.

Have you considered running a powered subwoofer? This would allow you to offload the the power hungry low frequencies from the BC9500.

Glitch

[Guy]

Glitch wrote:

You will likely have the same issues with “smaller Beolabs for the rear”. The root of the problem is that the low impedance configuration that you are trying to run is pushing the BC9500 past its design limit.

But wouldn’t Beolabs reduce the load on the BC9500 because they are providing their own amplification? (Connected to BC9500’s PL output before its main amp stage)

[Glitch]

Guy wrote:

But wouldn’t Beolabs reduce the load on the BC9500 because they are providing their own amplification? (Connected to BC9500’s PL output before its main amp stage)

Absolutely. My mistake. I misread the statement and was thinking “Beovox” (i.e. physically smaller speakers wouldn’t change anything).

How would the relative loudness between the front and rear speakers be controlled with a either a Beolab speaker or Passive solution?

Of course, if one wants really wants “loud”, two pair of Beolab Pentas would do the trick ;-).

Glitch

[Guy]

Glitch wrote:

How would the relative loudness between the front and rear speakers be controlled with a either a Beolab speaker or Passive solution?

They couldn’t, unless it was set up as a pseudo linkroom (by adding a BL1611 and and an IR eye to the Passive, which would then have to be put in L.OPT 4 so that it could only be controlled by pressing LINK first on the Beo4.)

But then RossJP is currently unable to control relative volume, but can of course Mute the speakers connected to the Spkr 1 output. If I was using the Passive setup (not with BL1611 etc), I would connect the 5700s to the BC9500 spkr 2 output. Mute would then work on the PL output to the Passive and other speaker pair, enabling them to be turned off whilst leaving the 5700s running*.

EDIT: This would be a bit messy to use because every time you then adjusted the volume control the BC9500 would unmute!!

[Guy]

This thread has reminded me that my in-laws had their BC9500 connected to two sets of passive speakers, in their case RL60.2s and CX50s. The CX50s were in a seperate room but for some reason they didn’t want an MCL sensor on the wall!! A speaker switch selected RL60s, CX50s or both.

Anyway, I disconnected the system when they moved house and realised that the speakers were connected in series from the speaker 1 sockets. The selector switch (DPDT, centre off) effectively ‘shorted out’ the speaker pair that was not being used. The centre position meant both pairs of speakers were driven in series. Obviously impedance varied according to the switch setting but the system worked well!

Here’s a scruffy schematic to explain!

I should add that the switch was fitted by the local B&O dealer when they purchased the system. The BC9500 spkr 2 socket was also being used to supply a couple of MCL2 link rooms.

[Glitch]

Guy: If you like speaker schematics (and I suspect that you do 😉 ) check out this one…

The cool thing that this one does is puts the speakers into series when both sets are selected. Note: the L&R channel signals originate from the upper left of the diagram.

 

RossJP: Just curious…

What did you have before the BC9500? Were you happy with the sound level?

Did you add the Redlines in order to get more volume or did you want rear speakers (or both)?

 

Glitch

 

[RossJP]

Just curious… What did you have before the BC9500? Were you happy with the sound level? Did you add the Redlines in order to get more volume or did you want rear speakers (or both)?

I had a Beomaster 5500, and I found it fine, but it was so long between last turning up that one loud and this one, I couldn’t make a reliable comparison. I do have a dB meter somewhere, if not, work will have one I can borrow…

I got the RLs for both, I like having 4 speakers because I like the way it spreads the sound round the room, instead of having such sweet-spots where the sound is better, it all ends up like a sweet-spot with 4 (to me, anyway). Extra volume is a bonus.#

I will probably try the Passive amp, since it’s quite cheap. While looking at alternatives, I wonder about Beolab 2s for the rear? I would then have a pair of column speakers up front, later, and maybe a Beolab 3 even later. One step at a time though!

[Author]

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