Blown Tweeters - Polk R700

[hoppy IPA]

Both of my Polk R700's blew their tweeters likely at the same time after 4 months of use.

Replacements are being sent under warranty but I'm hoping you can help me figure out why it happened & how to avoid it happening again.

My setup is LG C1 ---> MiniDSP Flex via optical ---> Buckeye NC502MP via RCA ---> Polk R700's.

I discovered the problem a few days ago when turning on the TV to watch a show. The sound was muffled & clearly not normal. Visual inspection showed the tweeters obvious deformation.


Any ideas?

thanks,
~j

 

[MaxwellsEq]

There doesn't look to be anything strange about your setup. How loud do you listen?

 

[Sokel]

That's strange.Deformation means A LOT of power.
Levels of playback?Listening distance?
Can you measure for DC on speakers inputs with a DMM?

 

[JSmith]

how to avoid it happening again.

Why Do Tweeters Blow When Amplifiers Distort?

ESP - The Audio Pages. Why Do Tweeters Blow When Amplifiers Distort? Find out what really happens when amplifiers cause tweeters to fail.

sound-au.com

JSmith

 

[dualazmak]

Did/does your tweeter(s) have protection and/or high-pass capacitor(s)?

If yes, then why did it fail to protect your tweeter(s)? Maybe, too much excess input was given even in expected Fq zone?

Any possibility of too much inaudible but harmful UHF (ultra high frequency) noises?
Ref.
- "Near ultrasound - ultrasound" ultra-high frequency (UHF) noises in improperly engineered/processed HiRes music tracks, and EKIO's XO-EQ configuration to cut-off such noises: #362-#386, #518
I wrote that such a high amount of UHF noises would be "possibly" harmful (and useless, meaningless) for our tweeters and super tweeters. I also pointed they would be highly possibly harmful for our beloved pets including dogs, cats, birds.

Now, I always have -48 dB/Oct high-cut (low-pass) digital filter at 25 kHz in my upstream DSP configuration which cutting-off such possible UHF noises.

 

[JasonC331]

When you are in there could you take the crossover out and take detailed pictures, so users will have a good peak inside and get values for other users?
I have 2 new ones sent by Crutchfield because some paint came off during the shipping

 

[Deleted member 48726]

Did/does your tweeter(s) have protection and/or high-pass capacitor(s)?

If yes, then why did it fail to protect your tweeter(s)? Maybe, too much excess input was given even in expected Fq zone?

Any possibility of too much inaudible but harmful UHF (ultra high frequency) noises?
Ref.
- "Near ultrasound - ultrasound" ultra-high frequency (UHF) noises in improperly engineered/processed HiRes music tracks, and EKIO's XO-EQ configuration to cut-off such noises: #362-#386, #518
I wrote that such a high amount of UHF noises would be "possibly" harmful (and useless, meaningless) for our tweeters and super tweeters. I also pointed they would be highly possibly harmful for our beloved pets including dogs, cats, birds.

Now, I always have -48 dB/Oct high-cut (low-pass) digital filter at 25 kHz in my upstream DSP configuration which cutting-off such possible UHF noises.

But the MiniDSP Flex doesn't seem to let UHF through or am I misunderstanding something? Asking curiously because of your suggestion of LP filter and if I would benefit from this as well..

Source-->

Minidsp Flex Review (Audio DSP)

This is a review and detailed measurement of the Minidsp Flex audio signal processor. It was sent to me by the company and costs US $475 for unbalanced and $550 for balanced that I tested. Flex borrows the interface from SHD and puts it in a compact package. Seeing how I really liked that...

www.audiosciencereview.com

@hoppy IPA Do you have some pictures of your tweeters maybe?

 

[dualazmak]

But the MiniDSP Flex doesn't seem to let UHF through or am I misunderstanding something? Asking curiously because of your suggestion of LP filter and if I would benefit from this as well..

OK, I understood it looks MiniDSP Flex has default(?) UHF cut-off LP filter around 22 kHz.

I use, on the other hand, DSP software EKIO which does not have default UHF cut-off filter, and therefore I configured -48 dB/Oct LP at 25 kHz for midrange, tweeter, super-tweeter.

BTW, as for the physical protection capacitors, I use 68 microF (400 VDC) film cap for Beryllium midrange (covering 500 Hz - 6 kHz), 10 microF (400 VDC) film cap for Beryllium tweeter (covering 6 kHz - ca. 15 kHz), and also 10 microF (400 VDC) filme cap for metal horn super-tweeter (covering ca. 8.8 kHz to 25 kHz).

I measured Fq response before and after (pre and post) the protection capacitors as shared here.

Just for your reference, latest signal path in my setup (ref. here);

 

[hoppy IPA]

@MaxwellsEq How do I listen? admittedly I like it loud.. often

@Sokel - yes. crutchfield has emailed guidance on how to do this. hoping I can do it correctly

@JSmith - thank you! Looks helpful

@dualazmak - I am not clear on that

@JasonC331 - For sure! I received the iFixit pry tool kit yesterday. Hoping for the best to avoid damage.

@Holdt - I do have pictures. Ill upload later today.

 

[MaxwellsEq]

@MaxwellsEq How do I listen? admittedly I like it loud.. often

OK, you might just have pushed them too far. Tweeters can be vulnerable to thermal overload. This can happen if the heat builds up and you get thermal runaway.
Once you have repaired them, you might want to try a phone based sound level meter such as NIOSH, to find what levels you are running at

 

[Flexecutioner]

If you haven't already, it wouldn't hurt to double-check any PEQ/FIR filters that are enabled. If you're using Dirac for a full-range correction, you should also check your target curve.

 

[Prana Ferox]

Do the failure dates line up with the presence of unusally finger-pokey children?

 

[hoppy IPA]

@Flexecutioner no adjustments MiniDSP Device Console other than high & low pass filters.

@Prana Ferox child free for life

Tweeter 1 exchange successful. The escutcheon pried off with ease - 3 magnets hold it in place. P1 phillips head screwdriver for the 3 wood screws fastening the tweeter to the cabinet. A toothpick or dental pick is helpful to remove the locking quick disconnects on the speaker wire.

 

[MAB]

Your tweeter looks mechanically damaged. They appear to be pushed in. Right?
If so, and if the damage caused the coils to rub, game over.

Also, don't set them face-down!

 

[MaxwellsEq]

The damage looks more mechanical then electrical - it would normally equate to children's fingers. I don't think listening at high levels could do that.

 

[Sokel]

Thing is that is too centered to be pushed by someone.It would need to push the ring by the tip,carefully to end to a result like this and furthermore,both of them!

Regardless,something must be very wrong to end up like this,I would double-triple check everything before connect them,SW and HW.
Also a visual inspection to crossover,such power may have fry components in there too.

 

[Deleted member 48726]

Your tweeter looks mechanically damaged. They appear to be pushed in. Right?
If so, and if the damage caused the coils to rub, game over.

View attachment 303016

Also, don't set them face-down!

I suppose extreme overheating could do that but it would have sounded very bad a long time before that to happen. OP might be
1. deaf,
2. have a badly clipping amplifier or something is wrong with the crossover. But it happened to both speakers so crossover faults is likely impossible.

 

[hoppy IPA]

@Holdt - Here are the pics of both blown tweeters. The damage pattern is very similar. As to your 1. I do have a hearing disability from my 2 decades in a Heavy Armored Cavalry Brigade. So that's a solid point!

@MAB - The replacement tweeter you're referring to is sitting in the factory protective shipping material. That picture shows the lot numbers of each speaker. I heard there was a run of bad tweeters (see post #11) so hopefully this is helpful for someone else. I'll be curious what lot number the other bad tweeter is since they were bought from different stores (Polk & Crutchfield).

 

[AdamG]

Why Do Tweeters Blow When Amplifiers Distort?

ESP - The Audio Pages. Why Do Tweeters Blow When Amplifiers Distort? Find out what really happens when amplifiers cause tweeters to fail.

sound-au.com

JSmith

The R-700 is rated 50-300 Watts. The Hypex nc500mp could essentially deliver too much power so I wouldn’t go past maybe 60%. But looking at the pictures they don’t have the typical fried look. The surround material normally shows signs of heat deformation. As others have said Kids or very bad visitors/guests.

 

[MAB]

@Holdt - Here are the pics of both blown tweeters. The damage pattern is very similar. As to your 1. I do have a hearing disability from my 2 decades in a Heavy Armored Cavalry Brigade. So that's a solid point!

@MAB - The replacement tweeter you're referring to is sitting in the factory protective shipping material. That picture shows the lot numbers of each speaker. I heard there was a run of bad tweeters (see post #11) so hopefully this is helpful for someone else. I'll be curious what lot number the other bad tweeter is since they were bought from different stores (Polk & Crutchfield).

View attachment 303073View attachment 303074

Did they get shipped to you like this?
If so, it was mechanical damage during shipping or handling!!! If so, likely the root-cause.
If you accidentally deformed them (like laying the speaker down on it's face), then be super cautious going forward! Did they ever get laid down on their faces?
In any case, looks like you are back up and running again! You are doing a solid on the repair...

Also, I like loud occasionally. If you find that you are blowing tweeters because of loud, you might want to consider more efficient speakers!!! These Polk are not very efficient and if you find you want more volume, they will be the limiter!