I know that very low q drivers 0.2-0.3 have a higher group delay in a box the same or above vas. What you can do about that?
Using a smaller box?
Subwoofers with qts of 0.4-.0.45 have the group delay exactly at the "sq" limit 20ms at 30hz where the low q subs goes much more above that.
But a low q subwoofer is better for ported and should sound better. I don't get it.
Thank you
Using a smaller box?
Subwoofers with qts of 0.4-.0.45 have the group delay exactly at the "sq" limit 20ms at 30hz where the low q subs goes much more above that.
But a low q subwoofer is better for ported and should sound better. I don't get it.
Thank you
In a sealed box yes, but in a vented box it have higher group delay (around Fb).
One solution to reduce GD is the pull down the SPL peak at Fb. But in a real-world subwoofer applicaton, high GD is not a problem IMO:
Higher than sealed, yes sure.
For vented speaker it very much depends on tuning.
Steep slopes have high group delay. That usually happens with higher Q drivers (for "flat" tuning).
"But a low q subwoofer is better for ported and should sound better. I don't get it."
In a vented box, the internal pressures are higher than in a sealed box plus below Fb, the unloading is more controlled with a lower Q driver. So even with a higher GD peak, a lower Q driver is still more desirable (simply by the more controlled cone motion) than a lower Q driver with lower GD peak.
In a vented box, the internal pressures are higher than in a sealed box plus below Fb, the unloading is more controlled with a lower Q driver. So even with a higher GD peak, a lower Q driver is still more desirable (simply by the more controlled cone motion) than a lower Q driver with lower GD peak.
What is important is the Q value of the subwoofer system, not of the driver. I think you are mixing the two between your statements. With that said:
Q (of the driver in the box) values of less than 0.5 are not all that useful (for a sealed box).
It's not typically possible to fix the corner frequency while adjusting the Q by changing the box volume. Instead both the Q and the Fb will rise as the box is made smaller.
With that said, group delay arises from changes in the frequency response of the subwoofer. The low Q version has a drooping response that is already changing at frequency that is above Fb, and this causes the group delay to start increasing sooner (e.g. at a higher frequency) than another hypothetic subwoofer with the same Fb and a higher Q value. But keep in mind the same driver could not be used to create these same two systems! This is also why a vented system can have lower group delay within the passband than a closed box one - the vented system typically has a flatter and more extended passband, but then drops off faster below the tuning frequency.
Keep in mind that group delay is not the only time domain parameter that is important. Vented systems, due to their higher rolloff below tuning, have worse transient response = more ringing compared to a closed box.
IMHO normal amounts of group delay at frequencies below 80Hz is not really something to worry about.
Edit: the last part of this old BassList post has some useful info on closed box group delay vs the corner frequency:
https://trueaudio.com/basslst2.htm
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The comparison is not fair because the vented and sealed box have different frequency responses. It would be interesting if the sealed box are EQ-ed to the same response as the vented have. I mean not mathematically but in reality.
The OP and last post bring up an important point: are we talking about SYNTHESIS or DESIGN? What are these? Answer:
SYNTHESIS: is where you formulate or describe the response that you wish to achieve
DESIGN: is when you try to make a particular driver have a particular response, or just maximize whatever response you can get out of it
Mostly, DIYers are doing DESIGN. This means they choose a driver for one reason or another (good parameters, cheap, on sale, recommended, etc) and then they work with it to make a loudspeaker or subwoofer or whatever. In that case when presented with the choice of what to do with it, you are completely constrained by this driver that you already have. You can put it in a vented box, you can put it into a closed box, and you can try to optimize those design options to have the best performance. On the other hand, a professional loudspeaker engineer can design a driver to have certain parameters (e.g their TS parameters, etc) and then have a run of that driver manufactured so that they can use it to match some specification that they synthesized for their product. These distinctions are important for this discussion. Why:
Because DIYers are doing DESIGN, you cannot really make a comparison like "when the tuning frequency of a closed box and a vented box are the same, which will have the better transient response". This is because, typically, you cannot create these two cases using the same driver (at least without some active equalization) but also because these two types of system will have different rolloff rates and therefore different ultimate (e.g. at DC) group delay levels.
If group delay is important to you, the designer, I suggest that you do calculate a few what-if design scenarios using a box-modeling program that will plot the group delay vs frequency. Then you can compare the group delay against what is generally considered to be acceptable, and make your design decisions based on that.
SYNTHESIS: is where you formulate or describe the response that you wish to achieve
DESIGN: is when you try to make a particular driver have a particular response, or just maximize whatever response you can get out of it
Mostly, DIYers are doing DESIGN. This means they choose a driver for one reason or another (good parameters, cheap, on sale, recommended, etc) and then they work with it to make a loudspeaker or subwoofer or whatever. In that case when presented with the choice of what to do with it, you are completely constrained by this driver that you already have. You can put it in a vented box, you can put it into a closed box, and you can try to optimize those design options to have the best performance. On the other hand, a professional loudspeaker engineer can design a driver to have certain parameters (e.g their TS parameters, etc) and then have a run of that driver manufactured so that they can use it to match some specification that they synthesized for their product. These distinctions are important for this discussion. Why:
Because DIYers are doing DESIGN, you cannot really make a comparison like "when the tuning frequency of a closed box and a vented box are the same, which will have the better transient response". This is because, typically, you cannot create these two cases using the same driver (at least without some active equalization) but also because these two types of system will have different rolloff rates and therefore different ultimate (e.g. at DC) group delay levels.
If group delay is important to you, the designer, I suggest that you do calculate a few what-if design scenarios using a box-modeling program that will plot the group delay vs frequency. Then you can compare the group delay against what is generally considered to be acceptable, and make your design decisions based on that.
That's not wrong but that's not completely right either.
EVERY high Q function causes increased/higher GD.
It doesn't matter if it's the tuning, the crossover or EQ. It applies to everything in the signal chain. Some (or everything) of the GD can be compensated by a DSP but that causes lag.
You cannot really EQ the two systems to be the same, exactly, although "sort of" if you only consider from the corner frequency and up. But even if the corner frequencies are the same, what Q value do you choose for the closed box? Which alignment for the vented box? Even with some generous hand-waving, you definitely cannot make the frequency responses the same below the corner frequency, and this gives rise to a higher level of group delay for the vented box because its ultimate rolloff rate MUST be higher.
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Some says it doesn't matter what Qtc of the sealed box have because it can be EQ-ed to almost any FR.
You can EQ a sealed box exactly to the same as a vented box but the opposite is much harder or impossible.
Well, you can, with 'enough' filters/dsp effort. It's neither practical nor in the least desirable. But even with the same GD, fr and spl, the modified sealed sub will perform worse because it has to do much more excursion to reach the same spl as BR. And the Bl(x) becomes more unlinear with the higher excursion. Both results ls in much higher distortion.
While this is true, it always comes at the price of dynamic and distortion.
It's not impossible in the most cases, it is often just a modified tuning needed (besides the EQing).
The first measurement was taken with a completely different environment and also contains reflections.
Yes, I agree but I did it to correct the claim.
That's not possible because without filters you can't get them to the same fr.
It's hard to say because the time scale is unreadable. The Paradigm measurement frequency is on its resonance, and the RCF is above. The bad decay of the Paradigm does not necessarily mean a high GD. GD and delayed decay are not equal.