Newbie Anthem question: target roll off

[Stuffed Chimp]

I recently got an Anthem MRX300 and am amazed by the effect ARC has had on taming a horrid bass node in my room.

I’m curious, however: I have full range speakers and no sub (hifi listening only). When I set the target bass roll off curve to ‘flat’ (no bass roll off - by my very limited understanding this would be the best setting for full range speakers) the system sounded awful: really thin and no deep bass to speak of.

However when I set it to roll off at 30Hz (the lowest setting on legacy ARC - I understand Genesis allows a target curve of 20Hz) suddenly everything was back where is should be and sounding immense.

So, absolute newbie question: why does a flat target curve sound awful and why does a target curve rolling off the bass above where my speakers can plumb to sound amazing?

My speakers are rated at a frequent response down to the mid-20s.

Prior to this setup I used a 2.1 system and listening to some of my favourite albums I have detected a lack of the deepest bass in places. Is this an effect of the 30Hz roll off curve?

Thanks in advance!

 

[dante01]

I'd seriously doubt that your speakers are portraying frequencies as low as 20Hz correctly, not unless you paid a small ransome for them and you've a room that is comparable to a light aircraft hanger in which to house them? The bass drivers in speakers able to be classed as being truly full range would need to be at least 15" in diameter.

There's also yje matter of the power you are diverting away from the mid and upper range drivers if using the main speakers to portray low end bass. You are effectively lower the dynamic headroom relative to the upper frequencies by portraying the low end frquencies via the speakers as opposed to using the sub to handle them.

 

[rccarguy3]

What speakers do you have?

 

[Stuffed Chimp]

IPL acoustics STL4s. They’re transmission line designs and are sublime.

Why would the flat curve sound so bad then, and the 30Hz curve bring back the goods?

I think I’m fundamentally misunderstanding what these curves mean, hence the ‘newbie’ part of the question!

 

[rccarguy3]

Not sure principles of transmission line, know they have wide frequency response as that is part of TL, but at what dB output, and distortion? I doubt they can match dB output at 20hz relative to a 12" subwoofer?