Flat frequency response


I am often surprised by the number of speakers with "gee-whiz bang" technology but can't even get speaker design 101 right. I can see the benefit of avoiding a lot of signal processing but preferences notwithstanding, flat frequency response seems like the logical place to start and then progress from there.

1) Why is it so hard to achieve?

2) Does it matter?

3) Is it reasonable to say when you skip the basics you are only progressing on a flawed foundation.

cdc

I pretty much agree that speakers should be flat but the music should not be flat. The problem is most music is produced badly.

 

Floyd Toole’s book is documented research on this subject and worth a read (linked below). The short version is people like flat response on and off axis and like some side wall bounce. Now as we are all super into audio we might different just a bit here and there.

When I got into this hobby 20 years ago I read all the tech. I was amazed and drank the cool-aid of brands like B&W. I read the white papers, even bought a pair. Only to have a grating sound and chase electronics. B&W is a good example of making a great speaker sound bad. Now I use speakers with good old paper drivers and big boxes….

My current speakers have 0.5 db adjustments for the treble and mid treble and those 0.5db adjustments make a profound effect on the sound.

I think other things that are hard to measure like dynamics play a huge favor. The measurements will have you thinking a small genelec speaker will sound better than big wilson audios. I can assure you they don’t. The dynamics of those big wilson just sound more real. Something that is missed in measurements. But yes flat measurements are a basic requirement for speakers for me. I will not even audition speakers that are not flat. Then they need to bring the other things.

 

https://www.amazon.com/Sound-Reproduction-Psychoacoustics-Loudspeakers-Engineering/dp/0240520092

I’ve never envied speaker manufacturers because they have an impossible task of designing a component to work in a room that does not measure flat and will vary greatly in size and overall dimensions.  And, as we all know here, the room has a huge impact on what we ultimately hear.  Yeah, room correction software and/or room treatments can and do help greatly, but still, I’d much rather make cables and take the much higher profit margins and transportability.  God bless speaker manufacturers!

Anyone who wants to hold up "flat" as ideal needs to at least investigate the B&K or the Harman speaker curves. There’s a lot of stuff written there. Also the East Coast vs. West Coast sound. How Klipsch and AR were sounding different from JBL and why.

Also, take a look at the work Floyd Toole has done in terms of determining bass levels vs. user preferences.

Then there’s the issue of hearing and volume. Some speakers really bring out the best at low volumes while others need to be played loud.

This is just the tip of the iceberg when it comes to deciding what a speaker output should be like.

 

 

Best,

 

E

Back when I was an avid amateur speaker builder, I borrowed some test equipment from a technician so I could fine-tune a crossover design, my target being the "holy grail" of flat frequency response. As I got closer and closer to "flat", the sound got worse and worse. Still I persevered, firm in my faith that once I reached "the promised land" of flat measured frequency response, everything would fall into place and the angels would sing.

Well, that didn’t happen. When I finally arrived at "flat" response (plus or minus about .75 dB indicated at the microphone location except for the peaks and dips in the bass region), the sound was harsh and bright and imo unlistenable.

After this highly unsettling experience I started spending as much of my spare time as I could in the library of a nearby university, poring though audio industry journals trying to figure out what had gone wrong and what the solutions might be. Here are the conclusions I eventually arrived at:

1. The in-room response at the listening position dominates perceived tonal balance, and the most natural-sounding in-room response has a gently downward-sloping trend as we go up in frequency (the Harman Curve being an example of this).

2. The spectral discrepancy between the first-arrival sound and the in-room reflection field should be minimized.

3. This means that BOTH the first-arrival sound AND the in-room reflections should have approximately the same gentle downward-slope as we go up in frequency.

Therefore, in my opinion, “getting the basics right” includes getting the first-arrival sound right, and getting the reflection field right.

Duke

speaker manufacturer