group delay, what's really good? - Car Audio | DiyMobileAudio.com | Car Stereo Forum

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Old 12-27-2011   #1
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Default group delay, what's really good?

So I have been reading up on group delay for subwoofers. I have been specifically reading about the Dayton Audio HO 10"

I read that anything under 25ms for a peak delay is "good", but what is really good? For example, in a sealed box with group delay under 6ms and a vented enclosure under 19ms, is there an audible distinction between the two? What is a good goal for good to great SQ?

now granted this is peak group delay, i understand that it will become less higher up in the frequency range but what about the lower frequency range?

If im trying to get more output and better efficiency, am i sacrificing sq and that "tight" sound even though group delay is under 25ms? What is exceptable and what is sloppy? I hope I am making sense here.

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Old 12-27-2011   #2
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Default

Generally no more than half a cycle of a frequency. 50hz = 1/20 = 20ms. So no more than 10ms for this given frequency, the threshold increases as frequency goes down.

GD is a function of phase (phase distortion) so in a car enviroment the "real" GD will look anything but good.

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Old 12-27-2011   #3
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Default Re: group delay, what's really good?

how exactly did you come up with that calculation? this way i can figure it out myself. and is there an audible difference when having a group delay more than half of the cycle frequency?

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Old 12-27-2011   #4
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Default Re: group delay, what's really good?

Hm... My opinion is that half a cycle vs frequency is audible. Can't remember where I've read that though, might have been in school. The audible group delay shift as frequency changes. Nevertheless, group delay is inevitable in bass frequencies. At really low frequencies like 20Hz, I don't think it matters much though, wavelengths are so long that we can't make out the differences in phase... As long as it doesn't impact FR too much.

You can simulate GD shift in WinISD for example, low tuned ported small enclosures and sealed have the "best" phase response. They actually sound pretty much the same if built correctly (and if you use a woofer made for this kind of application ofc).

Frequency Calculator: Time period frequency formula cycle duration periodic time period to frequency wavelength calculation calculate calculator Hz hertz to ms T to f worksheet definition - sengpielaudio Sengpiel Berlin

From LinkwitzLab: "I am not certain what happens in the range below 100 Hz and I have strong suspicions that this is the region where delay distortion is audible. It is also the region where delay really accumulates via vented and bandpass woofers"

From soundwesthost: "The maximum delay is 55ms at around 18Hz. Although this may seem to be "bad", it is actually a very good result. A similar delay at a higher frequency could be very audible - depending on the frequency. Group delay is the inevitable reaction to phase shift."


In any case, here's a few homepages that discuss group delay:

Discussion of Group Delay in Loudspeakers
Group Delay

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Old 12-27-2011   #5
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Default Re: group delay, what's really good?

Thank you Hanatsu, I have more reading to do to fully understand this. I've read that and I quote, "correctly built ported enclosures can create a subwoofer sound that is just as tight and sq oriented as a sealed enclosure." This leads me to believe that the difference between 6ms and 19ms at 30hz is only barely audible or not at all in certain applications. However, I have not used enough subwoofers or built enough enclosures to know if this if really the case. The last ported enclosure I built was an epic fail so I am far from knowing what I am doing.

Im hoping "CHAD" can chime in. I know he has used the Dayton Audio 10" HO in both a ported and sealed enclosure. a small ported enclosure gave him a nice flat response down to 30hz.

I would assume the increase in group delay is easily acceptable if one could have a flatter response and increased output. Is this correct?

and to make my post a little more clear, Im asking all of this so that when I build my enclosure I can do it correctly right away! My computer won't run winisd(don't know why but I have tried several times)

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Old 12-27-2011   #6
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Default Re: group delay, what's really good?

I wouldn't worry about GD ranging from 20-35Hz, can't back that statement up though. GD will peak close to tuning frequency (Fb), the lower Fb you got the lower the peak will occur. Therefore it should sound cleaner in those frequencies above Fb (compared to a "normal" tuned ported box). Decreasing box volume lowers GD but also lowers output, the port length increases aswell. You might have to put the pipe outside the box, I had to. The frequency response between the sealed the small ported enclosure should model about the same. The ported should have a little more output in lower freq but almost the same rolloff. You won't have a huge advantage in sensitivity, but the sub have an amazing power handling around Fb so that should make up for it... if you got enough juice in your amps

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Old 12-27-2011   #7
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Default Re: group delay, what's really good?

Modeled my subs, remember this only theoretical. These responses won't look like this inside a car. Also a rough guess over how cabin gain affect the different enclosures. Hope this helps a little

Pictures a bit small but they works... I guess
Attached Images
File Type: jpg fr iri12.jpg (65.4 KB, 47 views)
File Type: jpg FR w TF iri12.jpg (63.9 KB, 42 views)
File Type: jpg GD iri12.jpg (63.2 KB, 42 views)

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Old 12-27-2011   #8
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Default Re: group delay, what's really good?

Awesome thanks, that helps a lot actually. I don't listen to a whole lot of music that hits 30hz very hard anyway, and the little bit that does (rap) doesn't need to sound perfect anyway lol. I already plan on venting outside of the box and thought of a real clever way to hide it as well! For the Dayton HO i have a few amps in mind.

depending on what I choose I will have anywhere between 450 and 600 watts rms. I drive a civic so it's not a huge car. When I drove my small stratus a single ten off 200 watts sealed was actually enough for me, I don't need huge boom boom

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Old 12-28-2011   #9
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Default Re: group delay, what's really good?

Interesting thread. One warning on the ho10 is it might sound a little weak because it's such a low distortion sub. I actually chose not to keep mine because of this. I like a little fat on my bottom end lol. Still a really nice sounding sub if clinical bass is what you're after. If you want something a little more beefy the Fi x10 and q10 are great small box woofers and actually work well in smaller ported boxes than the Dayton

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Old 12-28-2011   #10
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Default Re: group delay, what's really good?

There's no need to go nuts analyzing group delay. Group delay is a function of phase, which, for the computer models you're using, is a function of the frequency response model. Choose a high-Q alignment for your box and get a peak in your GD. Coose a low-Q alignment get a flatter GD curve.
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Old 12-28-2011   #11
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Default Re: group delay, what's really good?

Quote:
Originally Posted by Hillbilly SQ View Post
the Fi x10 and q10 are great small box woofers and actually work well in smaller ported boxes than the Dayton
SMALLER? wow, i didn't think we could get much smaller lol. Hillbilly, I don't have a whole lot of places to hear and audition subwoofers. What I choose for my next sub is going to be from reviews and so forth. I don't need a lot of boom, but I have also read good stuff about FI.

Thank you Andy, that makes sense to me.

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Old 12-28-2011   #12
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Default Re: group delay, what's really good?

Quote:
Originally Posted by Hillbilly SQ View Post
I like a little fat on my bottom end
That's what she said!!

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