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Blew out the woofers on my brand new speakers, need help to find the cause

NoJo2211

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Hello,
I installed an entire new system in May and things had sounded amazing until I screwed up this weekend. I was demonstrating the system for some guests (showing off) and it was suggested I play a YouTube video that showed the frequency and played the according sound. This video had millions of views. Things were set loud, but not extremely loud. Right in the beginning, In the 20-30Hz range, the woofers on the Bookshelf speakers were moving like crazy and then both Left & Right speakers at the same time began to smoke. I shut everything down and the speaker woofers are completely done. I contacted Wharfedale and they claim it is not covered because the speakers were "over-driven". They are offering to sell me replacement woofers for $99 each +shipping.

I take responsibility for probably screwing something up, but I am looking for some advice to get to the root cause to prevent anything like this from happening after the repair or replacement of these speakers. I did have these speakers wired bi-amp into the Denon unit listed below. It was configured in the 7.1 (bi-amp) menu, wired as they instructed in the attached image from the manual. In researching, one mistake I may have made was having the speakers set to Large in the Denon setup as I believe that means full range of frequency was sent to the Wharfedale EVO 4.2 and the 20Hz was below its capable range. Or was the Bi-Amp the cause? Or my wiring? Any thoughts and suggestions are greatly appreciated.

Follow Up: Thank you everyone for the discussion. I have learned a lot. Definitely no interest in watching test tone videos in the future. As I mentioned, one of my guests said to try it and 10 seconds later I have smoke. I have already adjusted the speakers to Small and set the crossover to 80Hz for after I complete the repair.

One follow up question, is there any concerns about the Bi-Amping? Is that a potential cause as well or am I fine with this AVR and speaker, assuming of course I wired it correctly. Should I just Bi-Wire instead, or not bother at all?

Denon AVR-X4700H
SVS SB-3000 Subwoofer
Wharfedale EVO 4.2 bookshelf
Wharfedale EVO 4.C center
Episode Signature Series 7 - 4 in the ceiling, 2 for rear surround and 2 for front height Dolby Atmos
Speaker wires 16AWG/ 4 conductor direct burial/in wall wire.

Denon - Bi-Amp wiring.jpg
 
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fpitas

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antcollinet

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Well you have an amp capable of putting out 200W (into 8 ohms?). Your speaker recommended amp rating is up to 120, and can dip down to 4ohms - so up to double the power from the amp.

If as a result the very high bass levels sent to the amp could cause the amp to clip - if this clipped to something similar to a square wave, this could also up to double the power again.

Probably as you surmise, you've also been sending freqencies that the speaker can't deliver. Not inherently a problem, but even though there is no audible output (or very low output) at those frequencies - there is still full power going into the coils. So in this case you can't hear that you are overloading them. And full power sine waves are have much more power in them then music with the same peaks. So if you want to protect the speakers don't use test tones unless you can also measure exactly what you are putting into the speakers in terms of power.

Basically you've put too much power into the speakers. Almost certainly you'd have heard distortion which is a sign the speakers are being over loaded.

As long as you play sensible audio (music) at sensible levels, your speakers should be fine. Don't let guests persuade you to push it as far as it can go. It's like letting your passengers tell you to rev your car to the top of the red range, and holding it there to see how it screams. It will scream: very expensively.

And there is no point in bi-amping. It won't load the speakers any more, but it also doesn't deliver any benefits in a passive speaker with crossovers built in. You are just spending extra on speaker cable.
 
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fpitas

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Prana Ferox

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Generally smoke means too many watts in too short a period of time. Those speakers are ported so below the tuning frequency (which is almost certainly above 20hz) the woofers are just flapping around unloaded. Plus for you and other humans, 20hz is barely barely at the edge of listening range so you need a ton of decibel output for it to sound 'loud' to begin with.

Generally speakers driven too hard too low tend to make mechanical noises before smoke, but maybe these Wharfs just hit different limits early, or maybe you didn't notice in time.

Fix your woofers, set them to Small, and buy at least 3 more 13" subs and try again
 

AdamG

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Almost certainly you'd have heard distortion which is a sign the speakers are being over loaded
If I can add on here. Test tones are Not for demonstrations involving alcohol. In addition with human hearing not being as sensitive to distortion in low frequency range. But setting bookshelves as Full Range. That was probably the killing shot. You basically sent full range 20-30Hz test tones to bookshelve speakers. Eat your pie and take the replacement offer with gratitude. $200 is a cheap price to pay. I recall personally paying much more back in my former life. ;)

Next time use Bass Management of the AVR. Set all speakers to Small and set their individual (pairs) crossovers as specified by the OEM or as measured in room f3 performance. Let the Subwoofers you have do the heavy lifting. They are built for it and their job is to take this hard load off your mains.

The Evo’s published specs are: 54Hz ~ 22kHz Recommended settings the crossover for them at 80Hz.
 
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fpitas

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fpitas

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Those speakers are ported so below the tuning frequency (which is almost certainly above 20hz) the woofers are just flapping around unloaded
That's something worth repeating. Nothing destroys a driver like driving it hard below the port tuning.
 
D

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Your errors:
- Too low frequency for the small speaker
- Too much power for the small speaker
- Using test tones on speakers in a non controlled (you didn't know the signal strength) environment

Test tones are not music. Their crest factor is much lower than music and thus strains the system a lot more.
 

Blumlein 88

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Well everyone has given good info. Try sweeps instead. Just don't sweep too long, and even then you can overdrive things. It is just harder to do. Plus with any test tone turn it way down. Turned too far down you don't hear anything, as you have experienced the reverse is much worse. And just so you don't feel too stupid, I've blown woofers once ( I only had a bridged pair of Classe amps capable of 1000 watts at 8 ohms driving them), and tweeters another time on different speakers. It happens if you venture into testing.

Though often ignored due to various issues picking the right value, fuses can be a good thing for speakers. You'll end up needing a smaller one than you think, and you might pop it now and again when it wouldn't have harmed the speaker. But it can save your speakers. Or buy some old Quad ESL-63's. They'll protect the speaker with an iron hand. When the crowbar protection shorts the amp smoke will come out of the amp not the speakers. Amps usually have fuses anyway.
 

audiofooled

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one mistake I may have made was having the speakers set to Large in the Denon setup as I believe that means full range of frequency was sent to the Wharfedale EVO 4.2 and the 20Hz was below its capable range.

Low frequency sweeps are meant for testing subwoofers. Your sub would mask any distortion or even mechanical noise coming out of your mains so you cannot hear any audible problems before it's too late.
 

Sokel

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Your speakers have an F3 at 56Hz according to specs.
Forcing them down to 20's so they can have an output that you can hear is a miracle that only smoke occurred.
With such an incident I would also check amp for damage as it was also forced to output too much power,well into clipping I suspect.
 
D

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Your speakers have an F3 at 56Hz according to specs.
Forcing them down to 20's so they can have an output that you can hear is a miracle that only smoke occurred.
With such an incident I would also check amp for damage as it was also forced to output too much power,well into clipping I suspect.
Nah, I don't think the weakest link in this Mythbusting episode was the amp. It is probably fine.
 

r042wal

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Well you have an amp capable of putting out 200W (into 8 ohms?). Your speaker recommended amp rating is up to 120, and can dip down to 4ohms - so up to double the power from the amp.
@antcollinet a little sideways on the topic. I have a McIntosh MC500 power amp that will push 500 watts to each channel at 8 ohms. It will also do 4, and 16 ohms.
My Celection Diton 66 towers are only rated 160 watts at 8 ohms. I never drive them hard and I have all this overhead. Would there be any advantage to running this 4 ohms? Thanks.
 
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