Vifta Xt15 and Vifa BC25SC06-04 design, filter help - 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 30th March 2014, 05:07 PM   #1
bcrazy is offline bcrazy  Norway
diyAudio Member
 
Join Date: Oct 2005
Default Vifta Xt15 and Vifa BC25SC06-04 design, filter help

I've been building speakers for some years but never attempted to design the filter myself. I want a small bookshelf speaker about 5 liters. I have done some simulation with boxsim, and this is the result.

Does it look OK?
Used frequency and impedance curves from zaphaudio.com

I am also considering buying some measurement tools, and have been looking at the Dayton Audio OmniMic V2 system.

Any advice appreciated !

xt15_bc25.jpg

xt15_bc25filter.jpg

Last edited by bcrazy; 30th March 2014 at 05:59 PM.
  Reply With Quote
Old 16th April 2014, 09:40 AM   #2
bcrazy is offline bcrazy  Norway
diyAudio Member
 
Join Date: Oct 2005
Up
  Reply With Quote
Old 16th April 2014, 12:27 PM   #3
system7 is offline system7  United Kingdom
diyAudio Member
 
system7's Avatar
 
Join Date: Aug 2008
Can't place the woofer at all. Where is a link?

This is what you typically do with 5" bass: SEAS 5INCH
__________________
Well, there it is! Best regards from Steve in Portsmouth, UK.
  Reply With Quote
Old 16th April 2014, 02:10 PM   #4
bcrazy is offline bcrazy  Norway
diyAudio Member
 
Join Date: Oct 2005
It some sort of oem driver i think. Here's a link from zaphaudio

http://www.zaphaudio.com/tidbits/Vifa-XT15-FR.gif

Zaph|Audio

Tweeter

https://www.parts-express.com/pedocs...ions-46535.pdf
  Reply With Quote
Old 16th April 2014, 02:29 PM   #5
system7 is offline system7  United Kingdom
diyAudio Member
 
system7's Avatar
 
Join Date: Aug 2008
Hmm... a WOODEN driver?

Guess you'd treat it like the paper SEAS CA15RLY version in that Troels Gravesen link I gave you. Add some resistance to the shunt arm of the bass to reduce that bump at crossover. I'd try something like 1mH, 10uF and 3.3 ohms for the bass. Third order filter to suit. Crossover around 3kHz. Much bigger box though. Try 12L. Anything less would be silly.

You can strip out Troels' LCR correction and the RC Zobel on the tweeter probably. Those are driver specific. I usually set the bass filter, and let Boxsim optimise the treble. But you can usually use much smaller capacitors than Boxsim comes up with. 4uF, 0.2mH and 10uF would probably be about right.
__________________
Well, there it is! Best regards from Steve in Portsmouth, UK.
  Reply With Quote
Old 16th April 2014, 03:49 PM   #6
system7 is offline system7  United Kingdom
diyAudio Member
 
system7's Avatar
 
Join Date: Aug 2008
I'd forgotten just how hard these 5" drivers can be if you don't do a low crossover!

Looks like some sort of bass notch around 1.5kHz is essential to stop the midrange rising badly.

This was a sim I did of a KEF R101 mini with a 1.4kHz LCR trap. It's an alternative to Troels' notch for 2.8kHz crossover. You'll want entirely different values, I expect. Thought it might help anyway. It's very flat and phase and impedance is good.

Sort of standard circuit for BBC type mini speakers.
Attached Images
File Type: png KEF R101 Type Filter.PNG (7.1 KB, 84 views)
__________________
Well, there it is! Best regards from Steve in Portsmouth, UK.
  Reply With Quote
Old 16th April 2014, 04:40 PM   #7
bcrazy is offline bcrazy  Norway
diyAudio Member
 
Join Date: Oct 2005
Thanks! Just recieved my omnimic, so I will build the boxes and measure the drivers in the box. I also have some vifa bc25tg15-04 i might use instead of the bc25sc06-04. The boxes will be around 5 liters because they will need to "fit" in the kitchen
  Reply With Quote
Old 26th April 2014, 09:51 PM   #8
bcrazy is offline bcrazy  Norway
diyAudio Member
 
Join Date: Oct 2005
Update: This is the first speaker that i will design the crossover by myself. I have read a lot about the topic, but the thing I have have the hardest time understanding is the phase, and phase tracking? of the drivers.

If someone could explain this to my in simple terms, please do!

Anyway I have spent some time measuring the drivers in the box they will sit in with omnimic, and some more simulations. These are not from my own frd files but simulating with the graphs from my own measurements comes very close. (I still need to learn how to make good/correct measurements)

So here is the new crossover:

Comments appreciated.
Attached Images
File Type: jpg VifaXt_BC25TG.jpg (297.1 KB, 55 views)
File Type: jpg Phase.jpg (287.1 KB, 54 views)
File Type: jpg crossocer.jpg (115.8 KB, 53 views)

Last edited by bcrazy; 26th April 2014 at 09:54 PM.
  Reply With Quote
Old 27th April 2014, 07:59 AM   #9
system7 is offline system7  United Kingdom
diyAudio Member
 
system7's Avatar
 
Join Date: Aug 2008
Vifa XT15:

Qts 0.53
Vas 9.96 L
Le 0.64
Re 5.5

http://www.zaphaudio.com/tidbits/Vifa-XT15-TS.gif

BC25SC06-04

Re 2.9

The driver seems to have a resonance at around 2kHz which you must notch with a parallel LCR trap if you are to avoid the too low crossover point. I would try 0.5mH and 10uF and 10R. You may be able to crossover around 3kHz then.

Bass Coil around 1.5mH is reasonable. Maybe 2R + 6.8uF shunt, but that is a wild guess.

The tweeter is hugely efficient and low Re. I would put at least 3.3R is series with it, maybe more in the course of simming it.

You have an impedance dip at 4kHz which says the tweeter filter is underdamped. Impedance is also dipping too low at the very top. You therefore need smaller capacitors (say 3.3uF) and perhaps a slightly bigger coil. I would put a resistor in front of the tweeter filter too. You really ought to get the high end impedance amp friendly and above 10-15 ohms that way.

Phase should be aligned at crossover and in the region where the two drivers are both contributing significantly. Say to the -12dB point of the weaker driver. I show a reasonable effort below with 3kHz XO. Troels' tweeter filter looks about right to me. I can't say how you'll get on with the bass, which probably needs something different.

It's quite a good strategy to get a reasonable flat curve on the 5" bass first, with a -6dB rolloff around 3-3.5kHz, then just tie the treble filter in with it. By the nature of the 5" driver, you'll have a cone breakup peak at around 7-8kHz too, they all do that.
Attached Images
File Type: png Decent Phase 3kHz XO.PNG (11.0 KB, 42 views)
File Type: jpg Troels Gravesen Vifa PL14WJ SS R2604.JPG (36.1 KB, 14 views)
__________________
Well, there it is! Best regards from Steve in Portsmouth, UK.

Last edited by system7; 27th April 2014 at 08:11 AM.
  Reply With Quote
Old 27th April 2014, 09:56 AM   #10
system7 is offline system7  United Kingdom
diyAudio Member
 
system7's Avatar
 
Join Date: Aug 2008
I should mention that if you are getting nowhere on phase alignment, it is worth flipping the waveguide tweeter polarity and trying different slopes. I think, if I remember right, 24dB per octave symettrical LR4 slopes usually line up on phase. 18dB/octave 3rd order slopes may line up with tweeter negative polarity.

You seem to be getting asymettric slopes, which can be done, but gets complicated sometimes. Frankly, sometimes I give up and conclude these drivers don't play together nicely.
__________________
Well, there it is! Best regards from Steve in Portsmouth, UK.
  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
First Build Dayton DA175 and Vifa BC25SC06-04 alg460 Multi-Way 134 5th February 2014 07:32 AM
troels design: peerless hds ppb 830860 + vifa xt 25tg 30-04 : Low volume tweeter then_dude Multi-Way 55 9th October 2011 05:00 PM
XO for Vifa PL18WO-08-09 and Vifa XT25TG30-04 MTM knightat83 Multi-Way 6 24th January 2009 08:51 AM
Vifa DQ25SC16-04 design kamppi Multi-Way 2 12th October 2008 06:42 AM


New To Site? Need Help?

All times are GMT. The time now is 08:28 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2