We can not hear group-delay under 100Hz?

[Helmuth]

Originally Posted by jerome69

Helmuth, have you seen this ? : Discussion of Group Delay in Loudspeakers

I think GD greater than 10ms below 100Hz is audible.

Hi Jerome,

I never saw this discussion, it doesn't answer the problem either. They also question and guess what is going on.
As one stated one wave length delay is the max, in simulation the delay doesn't become longer than a wave length.

One can turn it around and say we make a speaker with out delay, so we do not have to answer the question what is allowable. How do we do this.
Only way I know is dipole or closed box to make delay low as possible.

[system7]

I always go for the SIMPLE answer.

High inductance on the woofer produces a slow deep bass which is almost like built-in bafflestep compensation. Low Inductance woofers produce fast lighter bass.

Similarly, reflex cabinets produce a feeling of deeper bass, but it lags the midrange and lacks impact on drums. Closed box with low inductance woofers close to a wall is fastest and can have considerable slam but at the price of deep notes.

In general, steep rolloff creates energy storage and delay.

Where it gets complicated is high-inductance woofers are a bitch to filter in the midrange. Trade-offs.

[jerome69]

Originally Posted by Helmuth

...
Only way I know is dipole or closed box to make delay low as possible.

Hi Helmut, yes but there are exceptions
Try a sim with a ER18RNX, a BR sim (17L@45Hz) with a nice group delay
I made the box, didn't sound like BR, very fast.
Keep the 10ms in mind, it is something which is admitted by speaker builders. But i think to have low GD is not enough to have precise bass.

Originally Posted by system7

...
High inductance on the woofer produces a slow deep bass which is almost like built-in bafflestep compensation. Low Inductance woofers produce fast lighter bass.
...

interresting
If you compare :
D1001-04 L26ROY
D1004-04 L26RO4Y
I have the explanation of the difference on these woofers.

I think this subject is not so simple, i have some questions, but not about group delay but about speed and bass articulations.
How fast a woofer should be in the bass to reproduce fast transient, to be well defined and articulate ?
Is group delay is a parameter ? Is intermodulation distortion is a parameter ? Is storage energy is one ? I don't have enough experience on bass drivers/baffle to answer these questions

[system7]

Ooh, new DESIGN series from SEAS.

Looks like they make a High Inductance Metal cone for the Active fans AND a LOW Inductance Metal Cone for the passive crossover fans who add a bafflestep coil around 3mH.

Lighter cones are faster too. Didn't I mention that?

[Helmuth]

Originally Posted by jerome69

Hi Helmut, yes but there are exceptions
Try a sim with a ER18RNX, a BR sim (17L@45Hz) with a nice group delay
I made the box, didn't sound like BR, very fast.
Keep the 10ms in mind, it is something which is admitted by speaker builders. But i think to have low GD is not enough to have precise bass.

Jerome,

This kind of BR tuning of the TS parameter I also do see at monacor bassdrivers. It hold the middle between Normal BR and Closed box tuning of the groupdelay.
The GD only rises with higher BR tuning, then you are on the same point as normal BR drivers.

[jerome69]

Helmut, I would go further to audibility of group delay
Yes it is audible if you have a huge peak in the group delay. But we want to know the limits. Calvin has gave figures : 6-10ms, higher than 10ms it is not good. I am agree with that.
But the debate is far from finished !
Some People don't like resonant bass because you have a lot of stored energy and cannot be right to them. Can we say resonant bass (BR, TL etc.) is not good ? There are at least 80% of speakers !

Group delay :
Audible means good bass ? Sure no !
Not audible means good bass ? I am not sure.

We have the drivers : a good driver for bass, TS parameter, baffle, electrical parameter etc.

Make good bass is not so easy... the room plays a role but don't say if you have the good condition to make good and high fidelity bass.

Perhaps it is not what you want to explore ?

[sreten]

Originally Posted by jerome69

I think GD greater than 10ms below 100Hz is audible.

Hi,

That is the sort of statement that makes discussing GD impossible.

Take a standard 4th order alignment for my standard default WinISD
driver, Fs = 40Hz, Vas = 58L, Qts = 0.43 you have to up Fs to 75Hz
to get 10mS peak group delay which is an awful bass alignment.

It peaks at 10mS @ 65Hz, which is also the -3dB point - rubbish.

The standard driver peaks at 19mS @ 36Hz - which is far better.

Even better is a good overdamped alignment, changing the
port from 38Hz to 28Hz, GD peaks at 27.5mS @ 22Hz.

At 65Hz standard and overdamped have 5ms and 4mS GD.

The overdamped has around 10mS GD @ 36Hz.

GD numbers inevitably increase with the bass extension, and clueless
comments regarding it as a useful number on its own are very wrong.

rgds, sreten.

[Pano]

Originally Posted by sreten

That is the sort of statement that makes discussing GD impossible.

Obviously not. It's being discussed right here, isn't it?

Perhaps stating GD in periods instead of time might be better?

[RockLeeEV]

I think the problem is measuring group delay in ms in the first place. Measure it in cycles instead.

[Helmuth]

Cycles isn,t that the same as saying:

Groupdelay X frequency =< 400 (rule of the thumb for designing)

example:

4msec X 100Hz = 400

10msec X 40Hz = 400

20msec X 20Hz = 400