Did I blow my mid-bass woofer?

[johnsen88]

Lads,

I am absolutely bummed out after what happened. Just when I got it all going with the setup, the 6" mid-bass woofers apparently started to produce distorted sound. My speakers are Focal 816v Chorus.

I have a streamer preamp(Primare i15) that is connected to the power amp(NAD 208) using a RCA connection. There is no 12v trigger running from the Pre to the Power. Therefore, when I switch on the system, it will be the Pre first and just a few seconds later, the Power. I did the same today and when I switched on the Power amp after the Pre, there was a loud pitched sound from both thr speakers. Not the boomy sort but somewhat that often encountered when the pre is switched off before the power. I have no idea what caused this but I immediately switched of the Power amp and the mains.

I waited and switched ON again in sequence and started playing some music. Felt something was not playing as it should and when inspected closely, I heard the mid woofer producing distorted sound. Strangely the vocals were clear but when a track that had a double bass was played, I heard distortion. I listened to the tweeter and the lower woofer and found nothing unusual sonically. I have included a track which would illustrate my findings.

Reduce your volume!

YT link:

Also, I tried to gently push the polyglass cone and it produced some scratchy noise. This was not present in the lower woofer's cone- cone moved inwards with slight pressure without any sound. Meantime, I did a sine wave test for the full sweep and found no anomalies. Both speakers played the full range without a problem.

I took out one of the mid bass drivers to see if anything is melted or loose etc but am unable to ascertain if my findings would point to a structural damage within the driver. Moreover, I did not inspect the crossover board as I am not confident of taking apart anything else at this moment. I have included some pictures and will be able to take more if needed.


I sincerely hope the good people here can help me out.

Thank you in advance.

 

[Clmrt]

Looks like the cone separated from the voice coil former.

 

[Wolf11Man]

We can speculate for a week but will only come to one conclusion: You need a new woofer. No way to fix it. Doesn't matter whether you burned the voice coil with such strange test noises or the voice coil came loose.
Sorry.

 

[johnsen88]

We can speculate for a week but will only come to one conclusion: You need a new woofer. No way to fix it. Doesn't matter whether you burned the voice coil with such strange test noises or the voice coil came loose.
Sorry.

Thanks for the reply. May I know what led you to conclude that the only way around this is a new woofer?

 

[DVDdoug]

May I know what led you to conclude that the only way around this is a new woofer?

Well, there are places that "re-cone" speakers, which can be a complete rebuild.

 

[johnsen88]

Well, there are places that "re-cone" speakers, which can be a complete rebuild.

Thank you for the reply, DVDdoug. I just wanted to expand my knowledge on this and for that reason, I asked Wolf11Man how he came to that conclusion.

As for re-coning speaker, will the woofers be what they were(sonically) before if I choose to re-cone them? Also, any place online that is worth checking out for a new set of original replacement woofers?

Appreciate your help!

 

[ZolaIII]

See if this is it, not quite sure regarding impedance so try to find this in some driver database to confirm it. They don't have 8 Ohms version, change both.

PS 165 V1 LAST EDITION - 2 separate way kit 16.5 cm | Focal

PS 165 V1 LAST EDITION, 2 separate way kit 16.5 cm : enjoy high-quality speakers performance for car audio system. High-fidelity car sound system that will accompany you everywhere you go with the excellence of French brand Focal.

www.focal.com

 

[Wolf11Man]

Reconing OEM woofer used in a special build is near to impossible. There may be a basic version that was for open sale, but the ones you find inside a factory speaker usually are "modified". This may be the voice coild (height and resistance) cone (wheight), the complience of suspension and spider.
You got to get all these parameters right, usually in a complete coil, spider, surround and cone assembly that then is glued and centered in your old drives chassis. You will find this allmost impossible. If possible, many repairs lead to a very different driver, changing TSP (the data that define how a driver works), as the most common parts are used.
With PA components reconing drivers is a normal procedure, as those age by use, but that is something completely different to HIFI.
Maybe ask FOCAL about "reconditioning" your defective driver. I fear they are much to big today to care about their old stuff. It is all made in Asia, use and dump the trash... No repair wanted.

The defect you have can not be repaired, in most cases the coil windings have moved on the supporting structure while being overheated. Now they rub inside the magnet gap.

 

[DVDdoug]

As for re-coning speaker, will the woofers be what they were(sonically) before if I choose to re-cone them?

I assume they know what they are doing. It's the kind of thing where you have to be a skilled specialist. If they don't actually have to change the cone, spider, or surround, the characteristics shouldn't change that much, if at all. Otherwise they can probably give you an idea of how close they can match it and if you should re-do both speakers. I'm assuming it's not both speakers... But they'd probably need the speaker in their hands before they can answer those questions.

Since it's the mid-woofer and not the main woofer (right?) the Theile-Small parameters shouldn't be that important and the main thing is probably to not change the sensitivity.

A million years ago I went to a re-coning shop in Los Angeles with my boss. That's the only reason I know anything about it.

 

[Zek]

The defect you have can not be repaired, in most cases the coil windings have moved on the supporting structure while being overheated. Now they rub inside the magnet gap.

If there is a good repairman, it is possible to make a new, higher quality coil former and replace the burnt one.

 

[dfuller]

Yeah, that driver is cooked. I don't believe Focal provide parts for their proprietary stuff to repairers, so I suspect you'll need a new driver.

 

[Jaxjax]

There are a pair of Chorus 706v on ebay , you could see if they will pull the drivers for even cheaper. It looks like it might be the same 6 1/2 mid bass driver as your 816

 

[Sokel]

The thing is that first you have to find out what caused this.
Any repair will be meaningless if the cause of this won't be fixed.

The way I read it it seems to me that some serious DC passed over in there.I would check the rest of the drivers as well.

 

[MaxwellsEq]

There is no 12v trigger running from the Pre to the Power. Therefore, when I switch on the system, it will be the Pre first and just a few seconds later, the Power.

For safety's sake always turn on the power amplifier last and turn it off first.

I always wait a few seconds before turning on my power amplifier to ensure all other devices are stable.

Before turning the power amplifier on, check that everything else looks sensible (e.g. DACs with variable volume or preamplifiers are not at maximum).

 

[johnsen88]

Thank you to all who have written a comment. Appreciate it!

See if this is it, not quite sure regarding impedance so try to find this in some driver database to confirm it. They don't have 8 Ohms version, change both.

PS 165 V1 LAST EDITION - 2 separate way kit 16.5 cm | Focal

PS 165 V1 LAST EDITION, 2 separate way kit 16.5 cm : enjoy high-quality speakers performance for car audio system. High-fidelity car sound system that will accompany you everywhere you go with the excellence of French brand Focal.

www.focal.com

I checked. Appears to be for car audio. Will it not change the sonic aspects of the mid-bass driver for this model?

Reconing OEM woofer used in a special build is near to impossible. There may be a basic version that was for open sale, but the ones you find inside a factory speaker usually are "modified". This may be the voice coild (height and resistance) cone (wheight), the complience of suspension and spider.
You got to get all these parameters right, usually in a complete coil, spider, surround and cone assembly that then is glued and centered in your old drives chassis. You will find this allmost impossible. If possible, many repairs lead to a very different driver, changing TSP (the data that define how a driver works), as the most common parts are used.
With PA components reconing drivers is a normal procedure, as those age by use, but that is something completely different to HIFI.
Maybe ask FOCAL about "reconditioning" your defective driver. I fear they are much to big today to care about their old stuff. It is all made in Asia, use and dump the trash... No repair wanted.

The defect you have can not be repaired, in most cases the coil windings have moved on the supporting structure while being overheated. Now they rub inside the magnet gap.

Appreciate the explanation Wolf11Man. I could get them re-coned, locally. These guys here have been doing it for donkey years and they are pretty good at it. I know it would be a gamble if I chose this option because of the work involved. From what I gathered, I believe parts are still available from Focal for this model. So, I may go with the straight swap with a new driver. I will ask them if they can do the repair work.

I assume they know what they are doing. It's the kind of thing where you have to be a skilled specialist. If they don't actually have to change the cone, spider, or surround, the characteristics shouldn't change that much, if at all. Otherwise they can probably give you an idea of how close they can match it and if you should re-do both speakers. I'm assuming it's not both speakers... But they'd probably need the speaker in their hands before they can answer those questions.

Since it's the mid-woofer and not the main woofer (right?) the Theile-Small parameters shouldn't be that important and the main thing is probably to not change the sensitivity.

A million years ago I went to a re-coning shop in Los Angeles with my boss. That's the only reason I know anything about it.

I did ask about this. They said that it will not be 100% like how the factory manufactures and/or measures. I guess it is for those who want the drivers to work and nothing more. For me, I would go with a new replacement driver because there is no guarantee that each side will sound identical after reconing.

There are a pair of Chorus 706v on ebay , you could see if they will pull the drivers for even cheaper. It looks like it might be the same 6 1/2 mid bass driver as your 816

I did. I will write them a DM. I doubt they will do this.

The thing is that first you have to find out what caused this.
Any repair will be meaningless if the cause of this won't be fixed.

The way I read it it seems to me that some serious DC passed over in there.I would check the rest of the drivers as well.

I have been trying to figure it out for the past 2 days. I will be dropping NAD an email for clarification. They have always been helpful when it comes to troubleshooting. I believe it is the power amp that caused this. How do I check the other drivers? A physical examination alone would not show much. I am getting a multimeter in. Should I remove each driver and check its resistance?

For safety's sake always turn on the power amplifier last and turn it off first.

I always wait a few seconds before turning on my power amplifier to ensure all other devices are stable.

Before turning the power amplifier on, check that everything else looks sensible (e.g. DACs with variable volume or preamplifiers are not at maximum).

This is exactly what I do.

My sequence: I switch on the main outlet > AV line filter > Integrated Amp > Wait a few seconds for the relay to click > Power Amp > Wait for a second or two for the relay to click > Ready for use. The sequence is reversed when shutting off. At times, I do wait a minute or so after I reduce the volume to 0, to power off the power amp. If I did so immediately, the speakers would produce an audible 'pop'. I read somewhere here that waiting a while before powering off the power amp would be the best.

Also, FYI the power amp is plugged into the 'switched' socket. The integrated amp is plugged into the 'unswitched' socket. Am I doing it correctly here?

I listen at very low volumes(65 dB or thereabouts at 2m)

 

[ZolaIII]

@johnsen88 ask them directly (Focal) if those are same unit's like in your speakers. If they are you probably can get it as the car kit for less money and easier.

 

[Timcognito]

My friend's Crown Amp blew up his very large and expensive Focal speaker driver and he was able to get a replacement from Focal. He is the second owner so it wasn't that new. Give the local distributor a call.

 

[johnsen88]

Lads, I have added a diagram of my setup. Excuse the amateurish illustration. It may be useful for some who require a visual illustration of my connections. Appreciate your help!

 

[johnsen88]

@johnsen88 ask them directly (Focal) if those are same unit's like in your speakers. If they are you probably can get it as the car kit for less money and easier.

The good news is that they have spares! They confirmed it when I wrote to them asking about its availability. I guess it would be a 1-1 switch. My concern now would be if such damage spared the other two, namely, the tweeter and the woofer. How do I even know if those are fine?

My friend's Crown Amp blew up his very large and expensive Focal speaker driver and he was able to get a replacement from Focal. He is the second owner so it wasn't that new. Give the local distributor a call.

Well damn. I am hearing these horror stories of power amps destroying speakers. It is really frustrating to see this happen when you are extra careful. I am not sure what exactly went wrong at my end but this happened after a good month into usage. What is even more annoying is the very fact that the Power Amp was sent to the agent for servicing and given the all-clear to be used.

 

[Timcognito]

The good news is that they have spares! They confirmed it when I wrote to them asking about its availability. I guess it would be a 1-1 switch. My concern now would be if such damage spared the other two, namely, the tweeter and the woofer. How do I even know if those are fine?

This all happened a few years ago for my friend and is second hand, IIRC he was told that some about the architecture/design of Crown was not compatible with the Focals and he got a different amp as a result.