MelodyMan

Expensive Mistake - Tweeter Damage

Recommended Posts

I have recently learnt the most expensive lesson of my short active speaker career, not using a protection circuit with tweeters directly connected to an amp.  Both of my Focal AudioM TD5 tweeters have suffered a power short/surge from a faulty plug board and Im now facing a very expensive replacement if indeed I can find the same model (£300 each) or need to find out if they can be repaired. 

A few people told me to protect the tweeters with an inline circuit but I never got round to it and all was fine for a few months until I shifted the system into a different room and used a different power plug board.  This power board had individual switches on each socket which I used to turn off power to the system but on this occasion I heard a sizzling sound at the switch which I believe was a power short which I think must have traveled to the amp and damaged the tweeters, although I didnt hear any nasty noise from the tweeter at the time.  The drivers still provide some audible output at a very reduced level but when touching the cone a greater level is achieved more to what is expected which would might indicate they are still working but the coils/cones are damaged.  Both tweeters have been affected at the same time to the same degree of damage.  I have rewired them separately with different amps and crossover and find the same results. 

Any advice on who I might turn to for repair would be very much appreciated and any advice on how to create an inline protection circuit would be most welcome.

Share this post


Link to post
Share on other sites
Super Wammer

Contact Serge Auckland of this parish, I know he advised me to do this, and like you I have not as yet, but have been lucky so far :(.

Share this post


Link to post
Share on other sites

There's voice coil and surround kits for the TC120 on eBay,  they may be  similar,  but finding someone skilled enough to fit them will be the next issue.

Share this post


Link to post
Share on other sites

Hi MelodyMan,

I have had this problem about 10 years ago were you have a power surge or you overload the tweeters direct from an amp then burn the tweeter coils out.

My cure was a simple cure which has worked for me ever since - since I build my own active crossovers I took one of the tops filters off the pcb board to make that 6db/octave to the amp , then at the tweeter I used a 3.3uF capacitor & a .47ohm 5 watt resister in the speaker box to the tweeter, ensuring no crossover point is changed by doing that.

I would of thought your amps would of had relays to protect from power surges & would not of clicked in when the surge happened which probably gave a transient to the tweeter which it is not designed for.

My tweeter protect just cuts the lower frequencies off like a normal passive crossover but still gives that super sharp treble you expect with an active crossover system.

Ever since doing this to my amp/speaker systems I have never blown a tweeter up since.

Regards

Jon247

Share this post


Link to post
Share on other sites

Hi All, thanks for the advice I will try the method with capacitor and resistor. Do these need to match the tweeter or I can just use the same values mentioned by Jon247.

I have sourced two coil repair kits from Zalytron in the US and one brand new 2nd hand unit off fleeBay so ready to get back in action.  I used a couple of spare Wharfdale Diamond tweeters as back up in the meantime and they dont sound too bad but look out of place.

I would still like to know how this type of damage from a power surge can be avoided in future. Is the inline capacitor and resistor the best method, is it worth getting a power board with surge protector does anyone have a recommendation for these. And is it worth using an amp for the tweeter that has built in DC (direct current) protection, would this help avoid a similar problem.   

What other types of failure can occur with active setups that I could try to avoid any more expensive mistakes in future.

Any advice on suitable amplifiers for an active tweeter setup would be appreciated.

Share this post


Link to post
Share on other sites

This article explains well the purpose of a capacitor in an active speaker setup

https://www.audiofrog.com/community/tech-tips/to-cap-or-not-to-cap-tweeters-in-systems-with-active-crossovers/

Share this post


Link to post
Share on other sites

Do you know your active speaker crossover points as that is the first thing to find out ?

What is the exact impedance of the tweeters ie 7.4 ohms / 3.6ohms ?

(3.3uF at 8 ohms is on my system a 6khz crossover point) - only because I wanted to make use of my wide band mid range cones frequency response.

Edited by Jon247
additional info

Share this post


Link to post
Share on other sites

The tweeter is 6 ohms and the XO is around 2200 and I used this very useful capacitor vs frequency calculator http://www.carstereo.com/help/Articles.cfm?id=1  to select a 12uF capacitor. Should have them back up and running soon enough.

Jon, that 6kHz XO is very high is that more like a super tweeter?

Share this post


Link to post
Share on other sites

Hi MelodyMan,

6Khz is fine as a tweeter - super tweeter is 10khz + - FYI, I am using a 3-Way System remember the mid start to roll off at 4Khz & the Tops roll in at 6Khz so the X point is 5Khz.

You will want to go a lot lower than the crossover frequency, work out how low the roll off cuts then add a cap for that frequency, perhaps 200hz, perhaps a 47uF 100v BP cap & a .47ohm 5W resister is needed for protection which will not affect your roll off, other wise your tweeter may roll off to quick loosing some highs in the process.

200hz should be low enough on the tweeter roll off not to influence anything down at that frequency.

Cap first then .47ohm 5w after cap to tweeter

You may have to test with different size caps to make sure your sound is not affected ?

Regards

Jon247

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.