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Discussion Starter · #1 ·
By "slow" I mean - is the group delay on JL subs excessive?

I used REW to measure the delay on my F110's as compared to my main speakers. For this measurement, the subs and the main speakers were in the same plane. I found that the GD was 50ms. Turning the ARO ("Automatic Room Optimization") program on and off made no difference to the measured group delay. For those who don't know - the ARO is a feature on JL subs that applies a single band equalizer to attempt to remove any peaks in the subwoofer response.

Text Line Plot Font Design

The above picture shows the group delay of 50ms with respect to the main system. The measurement was taken from the listening position, i.e. about 4m from where the speaker and subs are.

From my reading, it appears that a GD of 5-10ms is considered the limit of audibility (please correct me if I am wrong), so a GD of 50ms is definitely audible. And so it is - I have always thought that my bass sounded "slow" and poorly integrated. As it turns out, a friend demonstrated to me what happens when you time align the sub to the mains - bass goes from sounding flabby and "slow", to sounding tight and "fast".

I have no idea why the sub is delayed by 50ms.

I am wondering whether others have measured the GD on their JL subs and found the same thing? I am also wondering what the GD is like on other brands of subwoofer?
 

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It's doubtful that the "sub" is slow.

What's far more likely is that you don't have flat frequency response in your room.

Don't worry about group delay - get the mains and subs integrated well and the bass will be very tight. You may need more subwoofers and different placement to do it.
 

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No they are not. If you are getting bad sounds it's because you have poor placement or poor setup. A crawl test would probably do wonders.
 

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Discussion Starter · #4 · (Edited)
I think both of you need to re-read my post.

To clarify, I am not asking about my in-room frequency response. Nor do I need tips on setting up my subwoofer(s). I do not need speculation about what other flaws may or may not exist in my system - I have done the sweeps, I can see where the problems are, and I know what I need to do to address it. I don't need to be told to put my sub on my seat and then place the microphone in various spots in the room. I know how to do all that.

My question relates to the time alignment of my subwoofers.

I want to know:

- if others consider 50ms to be excessive
- whether the GD in other subwoofers is in the same ballpark

If people could stick with answering my question, I would be most grateful.
 

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Your fundamental misunderstanding is that you think group delay is independent of the room. You are not performing anechoic or quasi-anechoic measurements of your subwoofers - so you have no frame of reference. That group delay is likely due to a room interaction and not the subwoofers themselves. Of course 50ms will be audible - the cause however is likely a room issue. Measure your subs in a quasi-anechoic scenario like a football field, and then post your GD - that will let us evaluate the subs themselves.
 

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I think both of you need to re-read my post.

To clarify, I am not asking about my in-room frequency response. Nor do I need tips on setting up my subwoofer(s). I do not need speculation about what other flaws may or may not exist in my system - I have done the sweeps, I can see where the problems are, and I know what I need to do to address it. I don't need to be told to put my sub on my seat and then place the microphone in various spots in the room. I know how to do all that.

My question relates to the time alignment of my subwoofers.

I want to know:

- if others consider 50ms to be excessive
- whether the GD in other subwoofers is in the same ballpark

If people could stick with answering my question, I would be most grateful.
A group delay of 50ms in a subwoofer is inaudible(kind of like directionality).

Given the sub in question is sealed I suspect the measurement to be inaccurate. Rarely to sealed sub have 50ms group delay.
Are your mains ported?

You can generally ignore group delay in subs any indication that you can hear it is probably psycho-acoustic in nature.

Since you have a genuine interest check out the following articles
http://www.silcom.com/~aludwig/Phase_audibility.htm
http://www.music.miami.edu/programs/...title_page.htm
http://www.zainea.com/firing.htm
http://www.audioholics.com/educatio...an-hearing-phase-distortion-audibility-part-2

Please note these can be quite heady reading. Even if it were audible the effects would be subtle.
 

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By "slow" I mean - is the group delay on JL subs excessive?

I used REW to measure the delay on my F110's as compared to my main speakers. For this measurement, the subs and the main speakers were in the same plane. I found that the GD was 50ms. Turning the ARO ("Automatic Room Optimization") program on and off made no difference to the measured group delay. For those who don't know - the ARO is a feature on JL subs that applies a single band equalizer to attempt to remove any peaks in the subwoofer response.

View attachment 35513

The above picture shows the group delay of 50ms with respect to the main system. The measurement was taken from the listening position, i.e. about 4m from where the speaker and subs are.

From my reading, it appears that a GD of 5-10ms is considered the limit of audibility (please correct me if I am wrong), so a GD of 50ms is definitely audible. And so it is - I have always thought that my bass sounded "slow" and poorly integrated. As it turns out, a friend demonstrated to me what happens when you time align the sub to the mains - bass goes from sounding flabby and "slow", to sounding tight and "fast".

I have no idea why the sub is delayed by 50ms.

I am wondering whether others have measured the GD on their JL subs and found the same thing? I am also wondering what the GD is like on other brands of subwoofer?

Group delay is the rate of change of the phase - in other words, the derivative or slope of the of the phase response.

There are a multiple number of ways to align a full range source and a sub.

The most comprehensive is this method utilizing functions available in a program such as REW.

The displays are made a bit easier to interpret with this PPT augmentation.
 

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Discussion Starter · #8 ·
Thank you guys for your helpful replies! A bit of reading to get through later when I get home from work.
 

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Hi keith

(know we have clashed in the past on these type of things) but 'slow' no matter how intuitive or reasonable is more down to implementation/alignment.

Personally I don't use group delay graphs (somehow don't make sense to me) but rather the impulse graphs.

Whether that will give further insights or not I don't know, maybe check from that angle and good luck.
 

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Hi keith

(know we have clashed in the past on these type of things) but 'slow' no matter how intuitive or reasonable is more down to implementation/alignment.

Personally I don't use group delay graphs (somehow don't make sense to me) but rather the impulse graphs.

Whether that will give further insights or not I don't know, maybe check from that angle and good luck.
Slow is just another word for bad IMO. Many people think large drivers are slower because they are often built in enclosures with a high Qtc. Believe me spend an evening with some LMS drivers in a proper enclosures and you will discover this is a myth.
 

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Slow bass almost always indicates a set up issue. The "quickest", tightest bass I have ever had comes from two well integrated 18" subs.
 

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Slow bass almost always indicates a set up issue. The "quickest", tightest bass I have ever had comes from two well integrated 18" subs.
I am a long time lurker of many forums. I thought it would be best to post to you here since this seems like a fair forum :wave:. I've only heard subs from Best Buy and some Paradigms/Velodynes/JL Audio from a local store. I've read through the majority of the GTG threads available to get an idea of ID subs. You have seem to heard numerous sub setups in many rooms. What 18" subs are you referring to having the tightest bass?
 

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Welcome to HTS, HooHACherrySoda.

The best bass I have ever owned comes from dual Chase Home Theater 18.1's. I've had anywhere from 10" subs on up to my current 18". Honestly, the bigger subs have produced the tightest bass in my experience. They don't have to move as far as smaller drivers, therefore returning to rest quicker, ready to hit again.
 
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