Question Mission SX2 Speaker issue

marcd5123

Active Member
Hi Folks I have a issue which is driving me mad. Iv got a pair of Mission SX2 these were a flagship model around 5 or so years ago. These are exceptional quality speakers and the basicly the best iv ever had in years.

Anyhow I have a problem, I believe its happening on both fronts as I have a Matching Misson Centre SXC1..

Iv tryed changing CD Player, interconnects does not make a difference same issue.

I'm wondering if iv blown the drivers on both front speakers personally not sure how.. 🤔What I can describe as a hissing /scratchy sounds.. Or like playing a badly scratched LP.

This is were is gets werid it only seems to be more evident on particular frequencys its not one long constant distortion whether you play anything or not.yet these speakers of they are damaged are amazingly capable of giving such incredible details as they are very revealing speakers as nature.

If both woofer or treble drivers were to be damaged or the coils in one of the drivers what would you typically find audible wise 🤔?.

I can still get absolutely sharp crisp highs and vocals can sound pin sharpe the bass sounds more or less perfect. I can play plenty of albums from Yes to Pink Floyd, Rush and at times you would not even notice their is a problem. It's seems to be more mid-range it effects.

I purchased these speakers at the end of the line steal price to buy them now or equivalent would have to spend around £750+.

I'm running a Denon 2015 X4100 AV AMP...

I need some help here. Is this more of a AMP output stage problem rather than speakers. If the coils were damaged at all both highs or lows would I still get exceptional sound or would it be worse.. Iv never owned or damaged speakers in my life. :thumbsdow
 
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password1

Well-known Member
Assuming you dont hear the hissing you describe on the centre, I would try connecting the centre to the left and right channel and see if there is hissing.

Also try 2 channel mode.

It's almost certain the problem lies with the avr if you dont hear the hissing with the centre connected to the left or right channel.
 

marcd5123

Active Member
Hi buddy @password1 Thank you kindly for the reply. Very much appreciated.

I listen to all my music using 2 channal Pure direct mode all the time.

The only ever time I use the centre and rears are for Films, Netlfix, Prime Video ect.

When nothing is playing and volume is set to the standard leval around 50db I have put my ears to both left and right speakers and can't here a single thing when nothing is being played no loud hissing by it self that is so more or less dead silent.

Its not gotten any worse as this started to happen around 2 month ago. That the only way I can discribe the issue definitely like a record that badly scratched as the stylus is player over it and it only seems to noticeablely audio when you play a certain type of music or peace of music is played and then you can here it sounds like the midband frequency.

So today I played The Yes Album and the Highs are so shape and clean regarding the trebble frequency and the bass is pretty lean and mean pinch as it should be. Instruments are very well defined and very big sound stage as these SX2 are bloody good so that's why I'm scratching my head if speakers drivers becomes defective would they still be able to give such a high quality of sound??.
 

xmb

Well-known Member
Use the test tones provided by all AV Amps to see if all the speakers sound the same. You can also connect the speakers to other output channels when using the test tones if you think one channel of the amp is faulty. If the amp has a pure direct mode also try that, as it sounds like a decoder issue.
 

marcd5123

Active Member
Hi @xmb Thanks for the reply. Much appreciated buddy 👍😊.

If I had to choose which of the 2 items that had to be faulty I would rather have the AMP faulty. Well I'd rather not have anything faulty to be honest lol.

Anyhow annoyingly the AMP is only 5 years old so kinda pardon my language here pissed off. My previous Denon 3805 is 16 years old and not a single thing wrong with it. I only not that long ago gave a full cleanup inside and out. More or lessint unit. I kept it as a "backup unit". Could not part with it such an incredible peace of kit and one of Denon's finest AV amps they ever made.

If the drivers were faulty on either of the speakers would I even get any decent sound of them.. Thats why it got me thinking it's an amp issue. Like my old 3805 in storage at the moment I still have my old Mission V61 they are 16 years old and work 100% and they were a mid end set around £400 at the time.

My SX2 and SXC1 are only 4 years old and to be honest I would absolutely be very upset and gutted to find that the drivers are damaged from Use.

I am a audiophile at heart and take extreme care of all my equipment after all costs be a great deal of money /I vestment.

I expect speakers to last at least 10 years without fault. Now I do play my music loudly at times but I never ever drive my speakers to the point it gets the AMP clipping in anyway the highest iv ever had the amp would be 58bd but on average it always around 50db and their does not seem to be evidence of any form of stress.

The X4100W was 3rd from top of Denons range for 2015 so theirs absolutely no way the amp is badly under powered and or speakers can't handle it.

They are highend set from mission 100W per channal driven at 8ohms even though they stage 6ohm rating. I prefer running them at 8ohms it's easer and less stressful for the amp over time and also does not drive the speakers as hard so I know it definitely won't be that.
 

Jules Tohpipi

Active Member
If you carefully place your thumbs at the 9 and 3 o’clock positions on the outer edge of the bass cone (not the rubber surround), and slowly push the bass cone all the way in and release a few times, do you hear any clicking or scratching sounds?

Don’t try this on the tweeters obviously.
 

marcd5123

Active Member
Hi @Jules Tohpipi thank you kind for your reply.

Well this is what Iv managed to do... So far before I take the amp to my local authorized Denon repair centre in West Drayton as I live in Uxbridge West London.

I am faily knowledgeable when it comes to electronics as I work in the IT industry my self.

I took my multimeter and checked both front speakers for coil damage trying 3 methods.

Firstly I checked the "nominal impedance value" now mission labels the fronts as 6ohms nominal value. My multimeter read out exactly at 4.1ohms left speaker ... So I then checked the right speaker and that came out also exactly at 4.1ohms. So this is kinda weird. If either one of the front speakers had any coil damage to the woofer driver they can't both be reading exactly 4.1ohms.

So I then checked the centre speakers which strangely has a norminal impedance rating of 4ohms that was odd I always throught it was also 6ohms as the fronts were.

So I put my multimeter to the terminals at the back and the centre SXC1 read bang on exactly 3.9ohms.

So this is kinda confusing... Mission can't of labeled the front speakers drivers correctly as both fronts read 4.1ohms and centre reads 3.9ohms. So the fronts must be 4ohms nominal impedance ratted and not 4ohm.

If either of the front speakers driver unit were damaged in any way coil burnt out or misaligned inside then surly one of the front speakers would have definitely given a different impedance value!!? 🙄

I then ran a 9V battery nest and put 9v current across positive and negative terminals with some speaker cable to check for phasing and any odd sounds while the speaker coils are moving and I ran this test on both front left & right speakers and even Centre Speakers and all 3 speakers phasing were correct and also all three speakers drivers were moving fairly fastly as I put a 9v current to the drivers I could not here any odd sounds.

I then ran my thumb and finger very carefully manually on both front left and right speakers to feel any friction with the drivers and again I could not audibly here any hissing or even feel any friction. All the drivers seems very firm to move manually back and forth.

Lastly I did a continuity test again using my multimeter on all 3 speakers and all came out with a beeping sound from my multimeter.

Obviously I could not test the tweeters not quite sure how to do that effectively to check if the tweets coils are damaged in any way. All I know is when ever I put on a peace of Music on with particular high frequencys all speakers definitely seems to deliver as should to my knowledge with crispy detials.


So do you think that 4.1ohms on both fronts are actually 4ohms norminal values rather than 6ohms or do you think that both front speakers have developed exactly the same faults in the same area on the coils which surely must be an extreme rarity as you are an engineer I definitely value all your opinions in this matter.

I also took the extra time out and checked both my Misson Rear speakers they are also stated as 8ohms norminal values and the multimeter reads 7.9ohms so their perfectly fine and my multimeter works fine.

With a these tests done this surly must mean it's my Denon X4100W that's developed noise on the output stage even on pure direct mode. This is as far as I can take it knowledge wide.
 

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Jules Tohpipi

Active Member
This is a common mistaken methodology to determine the nominal impedance of a speaker.

If you pass a DC current from a multimeter into a loudspeaker then all you'll be measuring is the impedance of the bass driver (or bass drivers in the case of the bipolar M5DS surrounds). The speaker's crossover ensures this happens as its job is to act as a low pass filter when presented with low frequencies i.e. 0 Hz in this case. Measuring/assessing nominal impedance can't be done with a multi-meter.

We already know the speakers are working - in a manner.

How did the test of manually pushing the drivers in and out go? Any scratching or graunching noises?

If a speaker has been played too loud it can cause the lacquer holding the voice coil to the former to melt or soften. The voice coil can then move around and bunch up (rise up) in places. After the speaker has cooled down the lacquer sets again. Except when it plays, and depending where it bunched, the bit which bunched up either won't clear the magnet gap or grazes against it. This latter mode doesn't necessarily mean complete failure - the speaker can still electrically measure fine but is now mechanically impeded. You will here a clicking or scoring sound as the driver is pushed in and out. In your case it might have happened at the longer end of the throw given it doesn't happen all the time.

This is not to rule out that's it's an amp problem, of course.
 
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marcd5123

Active Member
Hi @Jules Tohpipi . Well the SX2s are acutally bi-wired including the centre speaker. So when I did test both sets SX2 and centre SXC1 no links were in place so their is no way of the meter of the meter measuring including Xover. So this would have been direct to the main woofer drivers in all speakers .hence the read out.

Yes for the M5DS they definitely would have gone via the crossover but it's still measuring correctly as per the readout.

I did state all the results using a 9V battery test and manual test with my previous statement above. :thumbsup:
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Jules Tohpipi

Active Member
Hi @Jules Tohpipi . Well the SX2s are acutally bi-wired including the centre speaker. So when I did test both sets SX2 and centre SXC1 no links were in place so their is no way of the meter of the meter measuring including Xover. So this would have been direct to the main woofer drivers in all speakers .hence the read out.

Yes for the M5DS they definitely would have gone via the crossover but it's still measuring correctly as per the readout.

I did state all the results using a 9V battery test and manual test with my previous statement above. :thumbsup:
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The signal still goes through the respective high/low pass filters of the crossover regardless of whether the bi-wire links are in place or not. Anyway if the links weren’t in place then you’re just measuring one driver at a time aren’t you - not both.

Nominal impedance is measured/calculated over a broad frequency range to include the combined average impedance of the two drive units as seen by the amplifier across those frequencies. You can’t calculate it by firing in a single frequency and measuring with a Maplins multi-meter.

The bi-polar speakers are a peculiar example which I can’t be bothered to explain in full here. But the short version is that their nominal impedance is higher than 8 Ohms but Mission has always traditionally quoted their bi-polar speakers as 8 Ohms anyway. Hence why you saw the 8 Ohms of 2x4 Ohms bass drivers whilst at the same time the crossover was blocking your multi-meter from including the impedance of the two HF units. QED.
 
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marcd5123

Active Member
Hi @Jules Tohpipi thanks for the reply much appreciated buddy.

I went on youtube to get an idea 💡 on how folks generally fault find issues with speakers. To be honest Iv never had these sort of issues ever this is actually a first for me.

So I watched around 4 YouTube videos to get an brief idea and see if their is Consistency to how you test bass units for faults.

So I decided to follow this one...


The 3 tests...

Check for impedance
Check for basic continuity
And manual physical check.

So all the youtube videos that I watched gave more or less the same way of testing seemed Stright farward enough to get an idea if the bass drivers are completely shot or not.

So I understand regarding the M5DS 2x 4ohms drivers =8ohm or 7.9ohm each.

So would I understand that both front SX2 bass drivers gave exact measurements of 4.1ohms each which proves their is correct amount of resistance for those speakers which excludes the HF tweeter driver which would be around 2ohms as they are fraction of the size thus giving a much smaller resistance reading to give the 6ohms norminal rating overhaul for each of the front SX2 then.

I fully understand that 6ohm is an normainal rating given by Mission as resistance will absolutely fluctuate up and down depending on the frequency/power the speakers are given by the amp. They are 100w each fronts and centre but again that's not the real value. I understand its RMS value would probably be around 40-50 w depending on the frequency speakers are outputting. Anyhow if those SX2 were giving out 100W continuously my ears would bleed.

Its quite odd that the Centre SXC1 is rated at 4ohms. My previous Mission were all rated at 8ohms including the tweeter this is the very first time iv noticed centre and fronts are different.

Anyhow iv always run the X4100W at its default of 8ohms this way balance of power and stress on the amp is nicely balanced out.

I could have manually changed the amp impedance setting on the Denon to 6ohms which sounds great for extra power .. However for long term longevity of the X4100W not such a great idea at all. AMP will heat up alot more and put even more undue stress on the components it cost me alot of money.

Denon actually stress to run the amp at 6ohms if you gave a single 6ohms speaker in the 5.1 setup. Which is realy odd states it in the manual and even Denons own technical department told me to run the X4100W at 6ohms I rather found that ilogical.

Running the amp at 8ohms is actually far better and healthier for the amp and speakers and still gives more than enough power in my opinion. Iv done so for years now. My previous Denon 3805 had not impedance selector it just did it it self.

Anyhow I could retest once more with the links in place I surpose.


Okay update 2/7/20

I have managed to dig out the manual specs for the speakers and the meter was reading the Minimum impedance values for all the speakers which coincides exactly with what the manual states for the front and centre speaker speakers

All your help and information has been very useful. Thank you. :thumbsup:
 

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