Are these caps OK for tweeter protection - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th February 2015, 06:32 AM   #1
diyAudio Member
 
Join Date: Jan 2008
Location: Melbourne
Default Are these caps OK for tweeter protection

I'm building a 2-way bass-reflex speaker with a Vifa XT25TG tweeter. It is bi-amped and has a 24dB/octave LR crossover at 1400Hz.

My research tells me that a 35uF cap should be OK for protecting the tweeter from DC.

I couldn't find a 35uF cap in my travels, but I did find these for $3 each. Are MKP caps suitable for the job? Would 4 of these in parallel be OK? I guess I would just stick them to the cabinet with silicone?

The iPad charger gives you an idea of their size (they are chunky).
Attached Images
File Type: jpg FullSizeRender-3.jpg (368.4 KB, 169 views)

Last edited by chris737; 4th February 2015 at 06:36 AM.
  Reply With Quote
Old 4th February 2015, 06:38 AM   #2
diyAudio Member
 
Join Date: Sep 2004
Location: Minneapolis, Minnesota, USA
Actually to keep the DC blocking cap from affecting the crossover region, for a 8 ohm tweeter you'll need about 140 uF, and double that for a 4 ohm tweeter.

Mike
  Reply With Quote
Old 4th February 2015, 07:32 AM   #3
diyAudio Member
 
Join Date: Jan 2008
Location: Melbourne
It's a 4 ohm tweeter, so 280uF huh? That's 28 of these caps! I reckon I'll get myself a motor-start cap in that case.
  Reply With Quote
Old 4th February 2015, 07:49 AM   #4
diyAudio Member
 
Join Date: Sep 2004
Location: Minneapolis, Minnesota, USA
No, motor start caps are not suitable for audio, use a motor RUN cap instead.

Mike
  Reply With Quote
Old 4th February 2015, 07:55 AM   #5
diyAudio Member
 
Join Date: Jan 2008
Location: Melbourne
OK, thanks.

Out of curiosity, how did you arrive at the 280uF figure?
  Reply With Quote
Old 4th February 2015, 07:55 AM   #6
Lojzek is offline Lojzek  Croatia
diyAudio Member
 
Lojzek's Avatar
 
Join Date: Feb 2012
It makes no sense to use a hyper value cap for this purpose.
You might do yourself a favor and measure the raw tweeter
response with an appropriate cap to help realize what it does.
  Reply With Quote
Old 4th February 2015, 07:58 AM   #7
diyAudio Member
 
Join Date: Jan 2008
Location: Melbourne
Hi Lojzek,
So you are saying 280uF is bigger than I need? Can you suggest a suitable value please?

I intend to measure the response of the speaker when it's built.

Last edited by chris737; 4th February 2015 at 08:03 AM.
  Reply With Quote
Old 4th February 2015, 08:10 AM   #8
Lojzek is offline Lojzek  Croatia
diyAudio Member
 
Lojzek's Avatar
 
Join Date: Feb 2012
You have said it yourself in the opening post.
  Reply With Quote
Old 4th February 2015, 08:16 AM   #9
Tweet is offline Tweet  Australia
diyAudio Member
 
Join Date: Jan 2015
Chris,

Presumably you are using an active crossover and directly driving the tweeter from a power amplifier.
The problem with using such a high value of capacitance is that when the amplifier first switches on, if there is no 'de-thump' circuit in place .....this is usually a time-delayed relay circuit that connects the drivers after the amplifier stabilized, that high value of capacitance will charge itself through the voice coil of the tweeter as a large pulse of DC current.
That DC pulse will have a very low frequency component in it, it may well 'pop' your tweeter(s) if the charging current of the capacitor is high enough.

I would suggest to forget the capacitor and check if Jaycar or Altronics have a standalone 'de-thump' circuit you might incorporate to intervene between the amplifiers and your drivers.

C.M
  Reply With Quote
Old 4th February 2015, 08:45 AM   #10
diyAudio Member
 
giralfino's Avatar
 
Join Date: Feb 2009
Quote:
I'm building a 2-way bass-reflex speaker with a Vifa XT25TG tweeter. It is bi-amped and has a 24dB/octave LR crossover at 1400Hz.
I just want to warn you that, according to someone who tested lots of drivers, and even used the same driver in its reference design (ZD5), the XT25 is not suited to a low crossover point. See the comments here: Zaph|Audio

Ralf
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
tweeter protection darren123 Multi-Way 7 6th February 2015 10:57 PM
Tweeter Protection? QikoCB7 Multi-Way 34 16th December 2013 07:13 AM
Combined DC protection and tweeter protection? CopperTop Solid State 10 13th January 2011 08:52 AM
Tweeter protection for active speakers paulspencer Multi-Way 31 26th October 2005 09:40 AM
Tweeter protection Cap static Multi-Way 13 15th January 2004 12:52 AM


New To Site? Need Help?

All times are GMT. The time now is 04:02 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2