Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Freq measurements and Hypex Filter Design adjustments
Freq measurements and Hypex Filter Design adjustments
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 11th August 2019, 09:21 AM   #191
Draki is online now Draki  Macedonia
diyAudio Member
 
Join Date: Sep 2010
Location: Macedonia
Quote:
Originally Posted by Steve2111 View Post
Draki
with the same loudspeaker drivers.
Tweeter Focal Audiom TD5
Mid ATC SM75-150S
Woofer Focal Audiom 15 WX


And some nice drivers those are! Sigh....
  Reply With Quote
Old 11th August 2019, 04:20 PM   #192
PLB is offline PLB  United Kingdom
diyAudio Member
 
Join Date: Sep 2008
Location: The backbone of England
Quote:
Originally Posted by Steve2111 View Post
Hi Peter
Do I flatten the curve with Boost/Cuts etc first, then apply the LR4 Lowpass to get to the target?
Steve
Hi Steve,

Yes, flatten the curve first (ideally to about 1.5 octaves past the crossover frequency), then apply the LR4 Lowpass. After this, use ARTA's target curve to compare your results with. The two responses should closely overlap to about 1.5 octaves past the crossover frequency.

Please keep in mind my comment in post No.103 (last paragraph) that the accuracy of a nearfield response is limited at high frequencies. This limit is dependant on the drivers diameter! For your 15 inch driver, an accurate response can only be guarenteed to about 332Hz!

Peter
  Reply With Quote
Old 13th September 2019, 07:01 PM   #193
Steve2111 is offline Steve2111
diyAudio Member
 
Join Date: Jun 2019
Default Freq measurements and Hypex Filter Design adjustments

Hi.
Now have my living room back for measurements etc.
I have bought and read Duhazi's suggestion of:

Accurate Sound Reproduction Using DSP, by Mitch Barnett.

Good but doesn't really help with the workings of HFD.
What I have gleaned from the book though which is relevant to my task:

Target curve should be flat (horizontal) upto 1KHz, then slope down to -6dB at 20KHz.

I'm going to ignore this and aim for all horizontal because if the recording has taken this into consideration, then would be compensating twice. I don't know therefore going to go a neutral flat horizontal.

More from the book:
"Design a digital crossover that does not introduce any frequency or time domain distotions. (seems logical, but how?) In addition to the benefits of bi-amping or tri-amping, digital crossovers open the door to driver linearization and time alignment" ( I thought this was possible passively too??)
"Linearize approx. +/- 2dB, Time alignment, usuallydelay Mid 1000 samples and tweeter 200 samples" (again I hope someone can explain this to me?)

Apart from reading the book, I have had the time to leisurely read all the posts again. I have at last come to the conclusion that my method may be wrong and that YSDR, Peter, Charlie and perhaps others are correct.

My method was to apply the crossovers straight away and then try to linearize the drivers. Why? To cut out of the equation the response beyond the crossover point so that there is less linearization, less filters/biquads etc.

Apparently this could cause drivers to be out of phase and also perhaps have "suck out" (I think it's called that) at crossover frequency. (there's not much suck out apparent in my total measurements though???)

The correct way (someone is going to say, says who?) is to linearize each driver to +/- 1dB first and to at least 1 or 1.5 octaves beyond crossover frequency. Once response of each driver is linearized, the crossovers can be applied and the resultant response should follow that of a Target Curve. If so, there should be no suck out at crossover and adjacent drivers should be in phase. IS THAT SO?

In the HFD manual: "For best crossover filter results, Linkwitz Riley are a good choice.............LR4 results in 360º phase shift - low output with 1 period delay"

I suppose LR8, 720º phase shift??

"The main advantage of LR filters is, when using them as low pass and high pass crossover filter (with same cut-off freq) your total filter response will be flat"
  Reply With Quote
Old 13th September 2019, 07:09 PM   #194
Steve2111 is offline Steve2111
diyAudio Member
 
Join Date: Jun 2019
Default Freq measurements and Hypex Filter Design adjustments

Draki & Peter
Your book suggestions seem very good too.
But I now feel that I need to plough on with HFD.
A decent manual would be great
  Reply With Quote
Old 14th September 2019, 06:24 AM   #195
YSDR is online now YSDR  Europe
diyAudio Member
 
Join Date: Nov 2013
Hi Steve, welcome back!

Here are few possible answers to your questions:

- A flat target curve as you said is a good starting point. You can fine tune later if you feel so.

- Avoiding time domain response distortion requires FIR filtering (instead of IIR), which the Hypex products doesn't have (yet?). But FIR filtering is not 'perfect' either because it introduces a larger total time delay to the whole response which may be a problem with e.g. movies where the sound and the picture needs to be in sync.

- Linearizing the total response after applying the crossovers not necessarily causes dips in the response (as you see with your result), but you may not use the maximum gain from the interaction of two or more drivers, and this may cause additional unnecessary distortion and stress to the drivers.

- If you linearize your drivers above and below the crossovers point and then apply an LR type filter you can get a maximum possible gain and flat response from the interaction of two or more driver if the phases matches at the desired axis. To get phase matching at your desired (listening)axis you can fine tune with the channel delay in HFD.

- You are right, LR4 filters are 360 degree out of phase (1 period delay for the lower frequency driver), LR8 filters are 720 degree out of phase (2 period delay for the lower frequency driver). 1 period delay may not necessarily audible, but naturally, the 2 period delay have more chance to be audible.

Last edited by YSDR; 14th September 2019 at 06:49 AM.
  Reply With Quote
Old 14th September 2019, 08:31 AM   #196
Steve2111 is offline Steve2111
diyAudio Member
 
Join Date: Jun 2019
Hi Dene, Thanks.

So I have decent woofer and mid measurements but you weren't too impressed with my tweeter measurement with high pass at 1KHz.

The XO freq for tweeter was to be 2KHz though you mentioned this was low. I have found Focal speakers with my tweeter with cut off freq at 2.2KHz and 2.5KHz. I could raise to one of these?

But for the tweeter measurement I am not comfortable to measure without high pass. I don't think that I can go much lower than 1KHz. See attached manufacturer's curve.

As you know, I have taken measurements with ARTA. Any advantage in taking measurements in HFD?
  Reply With Quote
Old 14th September 2019, 12:09 PM   #197
YSDR is online now YSDR  Europe
diyAudio Member
 
Join Date: Nov 2013
Yes, you can rise the crossover frequency of tweeter/mid for better power handling and lower distortion. Your mid dome used to 3.8kHz (if I remember correctly) in commercial designs anyway but i recommend lower than that if your tweeter can handle. Guess between 2.2-3kHz.

Measuring the tweeter's frequency response for crossover development without any high-pass filter is pretty normal method at any decent speaker designer/manufacturer , including Focal i bet. Just don't do too loud, it is really not necessary to do it loud, it can be done very quietly and the tweeter have no problem to handle that.

One advantage of HFD measurement is that you need to measure once per driver for frequency response correcting. But for best result you need more measurements to check off-axis responses and ARTA have the advantage here for measuring, overlaying and averaging more measurements like the off-axis responses.
  Reply With Quote
Old 14th September 2019, 02:48 PM   #198
Juhazi is offline Juhazi  Finland
diyAudio Member
 
Juhazi's Avatar
 
Join Date: Mar 2007
Location: Jyväskylä, Finland
With REW and propably with ARTA you can set lower limit for the measurement sweep/noise. A protective serial capasitor for the tweeter might be a good idea, if the driver is rare or expensive. Remember to measure off-axis response of each driver in the baffle too! To catch distortion play at least at 90dB at 1m, preferably 95dB.

Each driver's response should be flat at least 1 octave past intended xo point, to get good phase mach and sound. Doing this first enables you to easily try several different xo points and slopes.

After setting crossovers, check timing/delay by playing two drivers at the time, also with reversed polarity on the other. Check spl response and step response.
__________________
Radikal aktivist AINOgradient speaker project

Last edited by Juhazi; 14th September 2019 at 02:59 PM.
  Reply With Quote
Old 15th September 2019, 06:29 PM   #199
Steve2111 is offline Steve2111
diyAudio Member
 
Join Date: Jun 2019
Default Freq measurements and Hypex Filter Design adjustments

The Tweeter manufacturer's curves
Attached Files
File Type: pdf Audiom TD5.pdf (515.2 KB, 7 views)
  Reply With Quote
Old 15th September 2019, 07:49 PM   #200
YSDR is online now YSDR  Europe
diyAudio Member
 
Join Date: Nov 2013
Quote:
Originally Posted by Steve2111 View Post
The Tweeter manufacturer's curves
Looks pretty flat down to 2kHz, so if you use a 2,5kHz LR4 crossover for example, you get good phase and frequency response down to 2kHz, which is not so bad.

But if you want better phase and frequency response, apply a Shelf2 -> LowShelf -> Center freq 1000Hz -> Q=0,7 -> Gain=10dB filter + your choice of LR crossover obviously.

Of course, this is only true, if you have the exactly same tweeter frequency response like in the datasheet.

Last edited by YSDR; 15th September 2019 at 07:53 PM.
  Reply With Quote

Reply


Freq measurements and Hypex Filter Design adjustmentsHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Capacitor to filter low freq buzz? steve71 Multi-Way 15 20th January 2009 05:48 PM
Freq resp measurements on the Apex Jr 3" M&K twin cone? Brisso57 Multi-Way 0 11th October 2007 08:38 PM
Notch filter at x'over freq. of woofer? grantnsw Multi-Way 23 25th August 2006 12:39 PM
problem with freq filter Magnat biatch Multi-Way 1 27th November 2005 04:40 PM
Freq Response Measurements of PHL drivers akunec Multi-Way 18 20th February 2005 12:39 AM


New To Site? Need Help?

All times are GMT. The time now is 12:19 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki