Audibility of group delay? - Page 3 - 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 2nd March 2012, 06:16 PM   #21
diyAudio Member
 
Rullknufs's Avatar
 
Join Date: Mar 2010
Location: Sweden
Send a message via Skype™ to Rullknufs
Quote:
Originally Posted by tuxedocivic View Post
Yes



Yes, up to 7.5ms iirc.
Would 7.5ms be enough to make a big improvement? On a scale from 1 to 10, how difficult is it to time adjust?
  Reply With Quote
Old 2nd March 2012, 06:39 PM   #22
diyAudio Member
 
tuxedocivic's Avatar
 
Join Date: Jan 2011
Location: Ladysmith, BC
It should be enough in a normal room.

1 being easy. 0.25. You just type it in with all the other settings. In 0.02ms intervals. All the work will be the measuring to determine the amount. If you leave it hooked up to your computer, do what Waltersys was saying by reversing the phase on the woofer. Adjust the delay (start with 1ms intervals and iterate) until the null is deep. That's the delay you should use. Save it to the minidsp and flip the polarity back. You can even reverse the phase on the mini I think...? Not sure about that though.
  Reply With Quote
Old 2nd March 2012, 07:41 PM   #23
diyAudio Member
 
Rullknufs's Avatar
 
Join Date: Mar 2010
Location: Sweden
Send a message via Skype™ to Rullknufs
That's cool...
But regarding cabinet options, what do you suggest I use? I'm not sure if I will be able to use the boosted bottom response that the ported box gives compared to a closed one. I mean, my room is about 16sqm. Should I go with a sealed box and maybe use some LT EQ (can miniDSP do that?) and boost bottom end if I feel the need?
  Reply With Quote
Old 2nd March 2012, 07:44 PM   #24
diyAudio Member
 
tuxedocivic's Avatar
 
Join Date: Jan 2011
Location: Ladysmith, BC
The minidsp can do LT EQ. If you have the amplifier power.
  Reply With Quote
Old 2nd March 2012, 07:52 PM   #25
diyAudio Member
 
Rullknufs's Avatar
 
Join Date: Mar 2010
Location: Sweden
Send a message via Skype™ to Rullknufs
I can adapt.
So, do you think a smaller sealed box would be a better option than a larger vented box?
  Reply With Quote
Old 2nd March 2012, 07:57 PM   #26
diyAudio Member
 
Join Date: Feb 2002
Location: Western Sydney
I'm almost scared to ask, but what does a 'Gaussian aperature' look like????
__________________
Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
  Reply With Quote
Old 2nd March 2012, 08:04 PM   #27
Boscoe is offline Boscoe  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Location: England
Quote:
Originally Posted by toenail View Post
I'm working on a ported sub enclosure that has a group delay peak of 32.4ms @ 20.1 hz. Is this considered excessive? Transfer function phase peaks at 179.2* @ 22.0 hz.

I've been reading some interesting articles that suggest the phase and the dalay graphs are simply two different ways to show the same characteristic of output. How audidble is this?

If I understand phase correctly, being close to 180* out of phase at 22 hz means that waveform of frequencies in that range will arrive at a later time than those at say 30* out of phase. This would mean that my perception of those frequencies would be that they were played at a lower db level, though in reality they're not. I'm wondering, could I could actually hear the difference, and what the threshold is for acceptibility of group delay/phase? Bass would sound sloppy/slow due to different frequencies arriving at different times?

Any thoughts appreciated.
The low the frequency the more GD you can get away with. The sound of the bass won't change just the time it gets to you and your ears aren't very sensitive to changes in bass distortion wise. Personally I'm a bit of a perfectionist I don't like to see GD rise above 50ms at 20hz. Slopes bass generally means poor quality drivers with low power amps and poorly tuned ported enclosures. If you use a passive crossover it doesn't matter how good you kit is you've already lost any hope what so ever of good bass reproduction. The passive crossover is the worst thing in hifi that has ever existed, along with tubes...
__________________
I thought about it once, but then thought again.
  Reply With Quote
Old 2nd March 2012, 09:31 PM   #28
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by Rullknufs View Post
I can adapt.
So, do you think a smaller sealed box would be a better option than a larger vented box?
Cabinet decisions should be made with the sound pressure level level desired, BR,TH,and BP type boxes all have a big level advantage over sealed subs.

Since you are limited to around 7.5ms of time correction, cabinet designs showing more group delay at the crossover point would not be a good choice.

The TH 200 sq shown below, a long path tapped horn, requires a bit more than 7.5ms to align a sealed top cabinet.

The Sammi is a ported cabinet using a pair of $5 speakers, it would require little or no delay to align with a sealed top cabinet.

The 7506 is a Sony 7506 headphone, used worldwide in studios and soundstages. It has fairly flat response, where it is flat the phase response is also flat. Unfortunately for the screen shot below, most of its response happens to fall at about -180 degrees, so much of the trace ends up not being visible, it would be right at the top or bottom of the display.

Phase and frequency response are reciprocal, if DSP is applied to flatten the frequency response, it also flattens the phase response. If a PEQ setting were applied to correct the 7506 broad boost centered at 60 Hz, and the dip at 250, itís phase response would also flatten out.
Same with the Sammi problem at 475 Hz.

The TH response above 250 would require far too many filters to correct, but sounds quite good in itís intended pass band of 30 to 100 Hz. It would require sealed top cabinets to be delayed by around 9ms optimally.

The difference between 7.5ms and 9 is within 1/4 wavelength at 100 Hz, so your DSP would still work fine for that large tapped horn, but many home theater type TH designet to work down to 16 Hz would require twice that delay time to be integrated perfectly.

That said, there are many proponents using several subs all around the room without any time alignment to even out room response, things can subjectively sound good even though that type of set up is terrible when phase or group delay is considered.

In a small room, getting too picky about phase/group delay is akin to complaining about a kid with a squirtgun shooting at you in a rainstorm.

Art
Attached Images
File Type: png FR,Phase.png (130.2 KB, 335 views)
  Reply With Quote
Old 2nd March 2012, 11:24 PM   #29
Ron E is offline Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
Quote:
Originally Posted by PeteMcK View Post
I'm almost scared to ask, but what does a 'Gaussian aperature' look like????
Transmission curve (cross section) is a gaussian curve,
It holds for optics as well, but I don't think it is all that practical for acoustics in air except in limited frequency ranges - like Keele's CBT arrays.
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan
Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. óAldous Huxley
  Reply With Quote
Old 4th March 2012, 11:51 PM   #30
diyAudio Member
 
Join Date: Sep 2008
Group delay by itself is inaudible. A recording is a group delay. The issue becomes important when the group delay of two drivers operating at the same frequency at the same time have different group delays. Their differences will cause an interference pattern in space where at some point at some frequencies they will add in phase to combine for a 3db gain in amplitude and at others will cancel completely causing a net amplitude of zero. This is the theory behind the so called "time aligned" speaker system, matching group delays between drivers. However, unless the drivers also happen to be coaxial there will be similar cancellation and reinforcements at various points in space. This is a direct consequence of classical wave mechanics analysis. If you want a speaker system to be phase coherent it must be time aligned at the crossover region and coaxial. Generally the tweeter has a shorter group delay than a midrange, a midrange shorter than a woofer. This is due to differences in inertial mass. If the drivers are coaxial, one way to align them in time is to apply the correct digital time delays to each driver using active crossovers and multiamplification and then sit on the coincident axis of the speakers. This will not cancel out effects due to room reflections however. The good news is that it's all probably very unimportant. There are far more serious issues related to accurate sound reproduction. In the 1970s it was one of the fads du jour, today it's been replaced by newer more lucrative fads in this industry.
  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
Acceptable group delay mitchyz250f Multi-Way 43 28th November 2008 07:40 PM
Group Delay Correction? pandaemonium9 Subwoofers 2 30th December 2007 05:32 AM
Group Delay............When Is Too Much Too Much? OMNIFEX Multi-Way 0 14th March 2003 07:30 AM
group delay question. theChris Multi-Way 8 28th November 2002 11:35 AM
Group Delay? Ignite Multi-Way 6 13th November 2001 05:52 AM


New To Site? Need Help?

All times are GMT. The time now is 07:52 AM.


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