Hello, I'm new to the forums but not to loudspeaker design....Its funny how many people don't know what the think of group delay, what it is and what it means to Sound Quality....I'd like to believe that I am one of the first people in recent times, within the DIY community to make connection between the Group Delay Curve and the Time to Peak energy curve...the trend of both lines.
When it comes to describing a sub as tight...No one is ever specific enough of what they are talking about...imagine that....If I say I want a tight woofer....am I speaking of time to peak energy or time to -25db energy? Both ..... Now that I have made known the to aspects of Time distortion....it must be made known that inside of a "room"...the room dominates all of these specs (Phase, FR, GD and Decay times).....phase can cause strange anomalies.....you can only expect direct energy measurements to be more faithful in a faithful within a nearfield situation but within 1 meter measurements of my current home system incorporating dual 12"s, I have anomalies non the less....as if near field didn't matter lol.
Regarding driver size....everyone that the epitome of Sound Quality is low excursion......See it move....see it distort. So a large driver needs to move less in order to achieve the same spl as a smaller driver thus distortion is less.....Multiple drivers can be using to increase accumulated surface area for a range of spectrum. These multi drivers boost efficiency and drive down excursion resulting in the same lowering of distortion.
If your driver only has to move a few MM to achieve desired output, you no longer have to worry about thd or dynamic compression/power compression
Agreed, I've been taught by the guys at Diya and over and over its touted that a 15" is the apex midrange. I also agree with much thats said in the above post, just wanted to add my 2 cents 😃
Oh ya! another thing! vented boxes tuned lower, will have lower group delay in the areas away from the tuning note. The lower you move the tuning note aka Fb.....the better group delay is in the area in perspective to the tuning note....I'm not looking at horn resp right now but I think the same trend will happen with Sealed boxes as you move the Fc lower via Box size....