Hello,

I have recently purchased a pair of monitor audio bronze B4's and a pioneer vsx1016

If the volume of the amp is turned up close to full, the mid range and low bass drivers intermittantly cut in and out of the left speaker.

I am no expert in audio setup. Would bi-amping resolve this? or is this a more serious issue?

Secondly, would more experienced users consider this a good setup?

lastly, if anyone has a manual for the B4's I would apreciate a copy

Thanks!
Niall

Re-check you wire connections carefully. Make sure there are not "strays" causing a short.
Swap the right speaker with the left (not the wires... the speakers). If the problem "moves", you have a bad speaker.

It is serious, and it may not be the speaker, although that might be waiting to happen.

The clue is that you have the gain near the max and the cut out is intermittent.

The speaker rating of 150 watts rms input power and looks ample for the Pio's 110 watts. However the amp is rated into 8 ohms so depending upon its design it may be wasting more significantly more heat trying for that into a lower impedance; enough to trip a protection circuit.

You don't say what you are listening to, but your amp may be near into clipping and that raises the average power level to the max. You may be listening to music with a narrow dynamic range (much modern rock/instrumental is that way) so that you are constantly using a very high average power level so things heat up and don't get to cool down.

Your speakers may have built in circuits to limit power and you may be tripping those, but they are usually not found on woofers. Woofers normally make mechanical distress sounds as they approach failure (if they make any sound at all).

Absent a protection circuit on the woofer it is more likely that are tripping an amp protection circuit.

By all means check the wires, switch the speakers but consider backing off on the gain (Save hardware, save your ears, save the world). ;)

The brochure for your speakers is found at
http://www.monitoraudio.co.uk/cms/uploads/userfiles/brochures/bronze_manual.pdf

The owner's manual for the other speakers in the bronze series doesn't have much more, except for the advise to bung the ports if the speaker is on or close to a wall.

Thanks for the replys!

I was really just cranking up the volume for a test ( as my wife and kids were away for the weekend :) )

So its unlikley i'll be listening to it that loud again (sounded like a bloody nightclub)

I guess I'm just concerned weather these devices are meant to reach their max load for an extended period.

By the way it was thumping dance music and the cones were shaking like mad. So when it kicked out, it needed a good bass thump to get the mid and low range drivers acting again. The tweeter never stopped during all of this.

Anyway, I will check the wires. One thing I forgot to mention is that at one point the amp switched off. So maybe its like you said, the circuits in it are overheating


Thanks also for the manual.

Cheers!
Niall

One other thing maybe worth mentioning:-

the left speaker is about 4 inches from the back wall, whereas the right one is about 14 inches away. I know the b4's have a tube in the back along with the front to push the air out. Could this affect anything?

Thanks again

One other thing maybe worth mentioning:-

the left speaker is about 4 inches from the back wall, whereas the right one is about 14 inches away. I know the b4's have a tube in the back along with the front to push the air out. Could this affect anything?

Thanks again

Yes, it could. As frequencies drop more of the sound comes from the port and less directly from the front of the driver. Air must be able to flow smoothly through the port; when it cannot the speaker's low frequency behavior can change. That is why the maker suggests "bunging" the port (changing it to a sealed design) when the speaker is near the wall.

Stuff a sock into the port to bung it.

One of the things that happens with a ported speaker is that it has a resonance frequency at which the power required for a given cone excursion drops significantly (the impedance drops so current increases). The speaker is more easily overdriven at and near that frequency. Conversely the draw on the amp is highest so it can more easily over heat.

In a sealed design and the opposite occurs; at resonance the impedance increases, so less current is drawn.

From your description, it sounds like you were overdriving the amp. If all of your bass was coming from your B4s then you probably had the amp pretty well maxed out. With 6 ohm speakers you do have a heavier load, so the amps will current limit and shut down if overdriven. Allowing them to continue to run with a clipped waveform will most likely damage your speakers.
Using a powered rsubwoofer and setting the crossover frequency up on your mains would dramatically reduce the power requirement on the amp. Alternatively you could use a beefier external amp on the left and right fronts. Kind of depends on whether you really want that volume or not.

..Doyle

Thanks,

Does that mean if I was to Bi-Amp the speakers it would put less load on the amp? I know the 1016 is capable of this.

My thinking here is that:-

is it safer to spread the load across 4 amps instead of 2 so each individual amp will not be over utilised.

i.e the bass drivers will then run on seperate amps.

or.. is it just the whole combination of power that stresses the amp.

Makes sence about a powered sub though.

BTW: Thanks for the info on why you bung the port Trekguy. It was mainly what I wanted the manual for !

Thanks,

Does that mean if I was to Bi-Amp the speakers it would put less load on the amp? I know the 1016 is capable of this.

My thinking here is that:-

is it safer to spread the load across 4 amps instead of 2 so each individual amp will not be over utilised.

i.e the bass drivers will then run on seperate amps.

or.. is it just the whole combination of power that stresses the amp.

Makes sence about a powered sub though.

There is a thread here that has a violent confrontation between those who hold two opposing theories as to why clipping damages speakers, tweeters in particular. Pick your poison--amps driven to clipping kill speakers at a power level that would otherwise be safe, because of the presence of higher frequency harmonics at clipping, or speakers get killed when any amp delivers more power than they can take.

Bi-amping addresses the first theory by ensuring that the HF amp is less likely to be driven to driven to clipping, by bass heavy material. However you need two things in addition to the extra amps to bi-amp. The speaker must in fact be bi-ampable (not just have jumpers on the terminals-those are usually for bi-wire which is worthless) and you need an external electronic crossover to divide the frequency range going to the woofer and the mid/tweeter. They can be bought, scratch built or built from kits. Good ones are not simple-
http://sound.westhost.com/p09_fig1b.gif

Are you also running a sub and if so, are the speakers set to small or large?