Muffled sound - help please

The most likely thing is that the amplifier was driven into clipping and has fried the BMRs. If so, you’ll need new ones. 

Are the BMR units (the uppermost drive unit) working ok in both speakers. Just wondering if party levels have either damaged the BMR unit or damaged components in the crossover. If nothing obvious (I take it you have powered down and checked cables etc). Have you any spare speakers you could substitute in to help narrow the problem down ?

You can do a little detective work yourself before carting things off to be repaired. Does the fault show on all sources? Is there any cable damage, and if you turn off, unplug and reconnect all leads to make sure they are properly inserted, does anything change? Is the fault in both channels? Does it change if you swap over the speaker cables?

One other thing I would check is that the analogue RCA interconnect cables from the Mojo to your amp have not come loose from the Mojo. If the Mojo is anything like the Hugo (mk1) I have, then the interconnects may only just fit properly, and any movement can have a disastrous impact on sound quality.  

If you have checked all connections are OK, and all is working as it should on all inputs (speakers aside) then most likely as HH says above, the amp was driven to clipping with eventually wrecked the BMR drivers in the speakers. Do you have any other spare speakers you can try to check?

Have you left your balaclava on?

Thanks everyone for the advice - I will do DIY detective work over the weekend - I have spare speakers to test. Will let you know how I get on......

Not sure about BMR drivers. But if things have been cooked, a good old school way to tell outside of the “obvious sound“ is place ones nose up to the driver and take a short but deep sniff. If you smell charcoal friend chicken you have a cooked driver,  alternatively push the driver equally either side of the centre with your fingers,  if you hear or feel a rubbing you have a cooked driver. Once the test has been a positive fail. You then place one foot in a steel capped work boot and gently persuade your off spring never to do such a thing to your stereo ever again. Aren’t they just little darlings, bless them......

hungryhalibut posted:

The most likely thing is that the amplifier was driven into clipping and has fried the ????BMRs. If so, you’ll need new ones. 

????BMR,…what is it.?

I have been in High End Hifi all my life,but have no idea what this English abbreviation means.

Keep in mind that this is an international forum,with participants from many,many countries,..therefore show consideration,and take the time to print the whole words,instead of using abbreviations.

?I used the word ”eht-cables” = ehternet-cables in a thread,an obvious abbreviation for everyone in Sweden.
But many Englishmen here,had no idea what I was talking about for cables.

So print the whole word.!

/Peder ????

 BMR stands for Balanced Mode Radiator and refers to the unique high frequency driver design found in the Ovator range.  

The S400s have BMR drivers. Balanced Mode Radiator. See more here https://www.naimaudio.com/product/ovator-s-400   and here https://www.naimaudio.com/site...-400-white-paper.pdf

Sounsfaber posted:

Not sure about BMR drivers. But if things have been cooked, a good old school way to tell outside of the “obvious sound“ is place ones nose up to the driver and take a short but deep sniff. If you smell charcoal friend chicken you have a cooked driver,  alternatively push the driver equally either side of the centre with your fingers,  if you hear or feel a rubbing you have a cooked driver. Once the test has been a positive fail. You then place one foot in a steel capped work boot and gently persuade your off spring never to do such a thing to your stereo ever again. Aren’t they just little darlings, bless them......

The BMR driver is a bit different to a regular drive unit - it's more akin to a planar or NXT type, so the push/rub test probably doesn't apply.

However, I do like the description of the "charcoal fried chicken" test...

My other half and some friends over a few Christmases ago a little too much vino blanco was consumed and the music got cranked up on my then 282/200 and the tweeter on my left Guru QM10 blew but only one and thankfully the amp was ok so maybe it might just be the drive  units.                                                                                                                                

ouch! how much is a bmr from naim i wonder....

hifi-dog posted:

ouch! how much is a bmr from naim i wonder....

I had a mate who ‘popped’ a BMR driver out of its seat . Naim were excellent and it didn’t cost the earth to get replaced. I’m sure the OP will get sorted.  All things electronic can be fixed. If Naim still have parts for the SL2, without doubt the S400 can be repaired if nessary.  

Why does S400 remind me of a Russian missile delivery system......????

You can always get a s/h pair Ovators for modest prices.

The BMR's are fabulous.

???? Steveaxe,...Next time your teenage children shall have a party,..do like this....

?Rent two small active PA-loudspeakers,such as musicians use when they play at any local Pub etc.

These loudspeakers allow your youngsters to blow on with,and no risk to your music-system.
You know how it was when we were younger,..is it Party,the volume should be high ????????.

They do not cost so much to rent an evening,..in addition,you know that your music-system works the next day.

You can also supplement with a smaller sub,if you are going to be really serious,..I always rent if I'm going to have a little bigger "Party".

/Peder ????

I would no sooner let teenage children loose on my hifi than let them have access to my bank account or pilot a moon shot!! What on earth were you thinking of?

Peder posted:

hungryhalibut posted:

The most likely thing is that the amplifier was driven into clipping and has fried the ????BMRs. If so, you’ll need new ones. 

????BMR,…what is it.?

I have been in High End Hifi all my life,but have no idea what this English abbreviation means.

Keep in mind that this is an international forum,with participants from many,many countries,..therefore show consideration,and take the time to print the whole words,instead of using abbreviations.

?I used the word ”eht-cables” = ehternet-cables in a thread,an obvious abbreviation for everyone in Sweden.
But many Englishmen here,had no idea what I was talking about for cables.

So print the whole word.!

/Peder ????

Is Ehternet Swedish for Ethernet?  

Timmo1341 posted:

I would no sooner let teenage children loose on my hifi than let them have access to my bank account or pilot a moon shot!! What on earth were you thinking of?

???? Timmo1341,...Exactly ????????????????.

ChrisSU posted:

Peder posted:

hungryhalibut posted:

The most likely thing is that the amplifier was driven into clipping and has fried the ????BMRs. If so, you’ll need new ones. 

????BMR,…what is it.?

I have been in High End Hifi all my life,but have no idea what this English abbreviation means.

Keep in mind that this is an international forum,with participants from many,many countries,..therefore show consideration,and take the time to print the whole words,instead of using abbreviations.

?I used the word ”eht-cables” = ehternet-cables in a thread,an obvious abbreviation for everyone in Sweden.
But many Englishmen here,had no idea what I was talking about for cables.

So print the whole word.!

/Peder ????

Is Ehternet Swedish for Ethernet?  

???? ChrisSU,...Oops,spelled wrong...sorry,too early in the morning ????.

/Peder???? 

Peder posted:

Timmo1341 posted:

I would no sooner let teenage children loose on my hifi than let them have access to my bank account or pilot a moon shot!! What on earth were you thinking of?

???? Timmo1341,...Exactly ????????????????.

I disagree, I would never discourage the kids from enjoying music. Next time, maybe use a streamer with the maximum volume setting trimmed down a bit. 

Timmo1341 posted:

I would no sooner let teenage children loose on my hifi than let them have access to my bank account or pilot a moon shot!! What on earth were you thinking of?

A bit off topic, but an Englishman mentioned to me - ages ago - that there were Jaguars having a 'father' and 'son' key. When the 'son' key was used, horsepower was limited. Fact or fiction?

There used to be special places for children to help keep them out of mischief called Workhouses.

Peder posted:

Timmo1341 posted:

I would no sooner let teenage children loose on my hifi than let them have access to my bank account or pilot a moon shot!! What on earth were you thinking of?

???? Timmo1341,...Exactly ????????????????.

After I came home from work one day to find a Crumpet in the drawer of my CDX2 (My then 4 year old daughter had observed me loading CD's into the transport), I put the whole rig up in my loft were it sat for 10 years before coming out of hibernation earlier this year. My solution? Spotify on their laptops and Sonos. I've had to live in audio purgatory for over a decade but it put an end to my panic attacks!