EQ question...

[Coytee]

Just being curious:

In some recent threads, there's questions about eq'ing some Khorns to squeeze out some highs... there are pro & con thoughts/comments to that....fine. I'm not worried either way.

To change the scenario:

If you start with a speaker that is known to be in good shape (good xover & drivers). Now you have a speaker in his situation that might not be putting out enough highs (right or wrong, that's his current impression)

If you put those speakers into a bare "hard" room then you will use the room as say, 50% of what you're hearing. If you treat that room (without eq'ing the speaker) you're going to change the final sound of what you actually hear, right?

So, could he treat his room and "tilt" the treatments such that he could brighten his high end?

I guess I'm more curious as to what degree you can really effect the sound by using treatments.

Can you slightly modify the bass response while at the same time, heavily "increase" the trebel? (or would you actually heavily attenuate the bass to achieve that effect of increased highs?)

Thoughts?

(ya ya ya... I'm at work & it's lunchtime)

[Jeff Matthews]

(ya ya ya... I'm at work & it's lunchtime)

You definitely are!

[jacksonbart]

Lets go get something to eat!

[Coytee]

I'm game

http://www.chesterspizza.com/

[Frzninvt]

An Equalizer should typically be used to "cut" frequencies not boost them it shouldn't be used as a gain device. Placement options, room treatments, and crossover component & wiring updates should be done first before turning to an equalizer. Remember also that a system is only as good as it's weakest link no amount of eq can fix a crappy source or poor amplication.

Now back to your regularly scheduled programming and pizza feasting!

[fenderbender]

I posed that in the other thread...and I have no idea if I'm correct but was just flying by the seat of my pants......I don't think any room treatments will boost treble response....conversely if you can cut some of the "boomy"bass.. I think that would make the treble seem boosted at given loudness, relative to the toned down "boomy" bass.

[Don Richard]

Any speaker will sound the best in a room with the fewest problems. A room that seems bright is doing that because of reflected energy. Different frequencies will be reinforced or cut unpredictably. This condition tends to cause uneven frequency response, time smear and bad transient response. This could be caused either by the highs being reinforced or by the bass being reduced, and EQ doesn't do a good job of correcting this. Measurements should be taken to determine the exact cause which will point to the proper way to correct the problem.

[dgoreck]

Any speaker will sound the best in a room with the fewest problems. A room that seems bright is doing that because of reflected energy. Different frequencies will be reinforced or cut unpredictably. This condition tends to cause uneven frequency response, time smear and bad transient response. This could be caused either by the highs being reinforced or by the bass being reduced, and EQ doesn't do a good job of correcting this. Measurements should be taken to determine the exact cause which will point to the proper way to correct the problem.

But that's the point, if you can treat a room to eliminate the extra reflected energy which is reinforcing the highs, why can't you do the opposite, and add in say refraction points to help bolster the highs if you lacking it due to the current redesign.

If you want a sound of 8 at your seat, and you currently getting 9, you treat the room, to subtract 1, to get 8. If your hearing 7 at your seat and want, 8, you need to add +1.... ok bad example....but maybe it helps get the point across.

In my head it makes sense to be able to do so, but really the treatment of room was kill those certain refraction points and frequencies to tame response. Doing the opposite isn't easily done, I think. If your at that point, maybe just knock the room down and start over?

[mark1101]

If you want to squeeze more highs out of your speakers........why not add a tweeter? [6]

[DrWho]

The sound of the room actually constitutes about 90% of the total
sound at the listening position (just for some perspective), but human
hearing is sensitive to the time the sounds arrive so that 10% actually
ends up being about 90% of what we perceive (roughly speaking).

Take
for example a speaker playing in the middle of a field with a gigantic
wall behind the listening position. Just assume for a minute that this
wall only reflects high frequencies and ignores everything else and
that the sound off that wall arrives half a second later at the
listening position. What the listener is going to hear is the original
direct sound and then sometime later another splash of HF. When the
delay is really long, it's going to sound like the high hat is being
hit more times than it really is....the listener hears this as a
separate echo and not part of the direct sound, which is to say that
even though there is more HF information at the listening position, the
listener isn't hearing more highs 'from the speaker'.

Now move
this wall closer and closer to the listening position so that the echo
happens so fast that it can't be distinguished as a distinct echo.
Instead, it will cause a blurring type effect with the high
frequencies. Sure, there will be 'more" high frequency information, but
it will be smeared over time.

As a consequence of this smearing,
you also introduce something called comb-filtering. Here's a picture of
what it will do to the frequency response:

So
although you might be able to 'add' more at a certain frequency, you're
also going to introduce big dips at all sorts of other frequencies. I
know this graph looks a bit extreme, but what it's showing actually
happens in real life all the time...that is what reflections do to the
frequency response.

To further complicate issues, the
comb-filtering caused by the reflection is going to shift around in
frequency as you change the distance of the wall causing the
reflection. Sadly, this also occurs if you move the listening position
around (because the distance to the speaker and the distance to the all
don't stay the same as you move around the room).

So even if you
could find a material to put on the wall that only reflected the
frequencies you wanted to boost, you can't guarantee that the
comb-filtering will line up properly. If you're talking the high
frequencies, moving your by as much as an inch can move you from a peak
to a null.

And again, our ears naturally distinguish between the
direct and reflected sounds, which means that there is still going to
be some blurring of the perceived direct sound.

Also, it is
terribly unnatural to have extra high frequency content in the natural
reverb of the room when there isn't high frequency content in the
direct sound. Your ears are going to hear that as distortion.

[Don Richard]

But that's the point, if you can treat a room to eliminate the extra reflected energy which is reinforcing the highs, why can't you do the opposite, and add in say refraction points to help bolster the highs if you lacking it due to the current redesign.

You can. Some studios use the Live End Dead End technique - the half of the room with the speakers is dead which controls the early reflections. The other half is live and diffused which gives the room a pleasing sound. A room with excessive damping throughout the room can sound muffled in which case adding diffusers to the rear of the room can correct the problem. What you want to do is to avoid the early reflections - they cause time smear and compromise transient response.

That is, if it is indeed the room causing the problem. If it is the speaker causing poor high frequency response, and it is operating properly, an EQ can be used to tune the speaker to taste.

[DrWho]

Some studios use the Live End Dead End technique - the half of the room with the speakers is dead which controls the early reflections. The other half is live and diffused which gives the room a pleasing sound.

For some reason I can't remember the guy's name off the top of my head right now, but whoever started the LEDE concept has totally revamped the technique based on the measurements he was taking of his rooms with TEF.

The modern LEDE (which you'll never read about on the internet) is a process where you minimize as much as possible the early reflections within the Haas window and then use diffusion to create as dense as possible sound field after the Haas window. So basically, your ETC graph would have a spike at 0ms from the direct sound and then 20-40ms of no reflections, and then your first reflection after the Haas window (the Haas kicker) needs to have a flat tonal balance and then the reflections need to decay logorithmically as you extend out in time. The final consideration is that there be no specular reflections after the Haas kicker...

In concept, the original notion of LEDE gets close to what I just described, but it should be quite clear that there are some major limitations...the most significant of which is that you don't want to overuse the absorption in the front of the room. Also, it's a lot easier to establish the proper reverberant decay after the Haas kicker if you redirect the early reflections instead of absorbing them.

[Don Richard]

For some reason I can't remember the guy's name off the top of my head right now, but whoever started the LEDE concept has totally revamped the technique based on the measurements he was taking of his rooms with TEF.

Don Davis in the third edition of Sound System Engineering gives the whole story on this technique. Before TEF the front half was deadened as much as possible. When accurate measurements became possible it was found that selective application of absorptive material could be employed with good results. Further research using TEF resulted in the Reflection Free Zone (RFZ) technique. Russ Berger was a studio control room designer who developed much of this stuff.

[DrWho]

Ah yes, Russ Berger [Y]

[SWL]

With all the experimenting I have tried with room treatments, I 've been able to tame the highs by treating early reflection points and placing an absorber behind the horn of the speakers. The bonus I received from placing the absorbers behind the horns was increased bass.......and most of all......increased mid-bass!!

I have yet to find a configuration with room acoustics that boosts the treble........but have found that properly dialing in the sub will do just that......in addition to enhancing the mids as well. []

It is true.......the room plays the biggest role.

[artto]

If you put those speakers into a bare "hard" room then you will use the room as say, 50% of what you're hearing. If you treat that room (without eq'ing the speaker) you're going to change the final sound of what you actually hear, right?

So, could he treat his room and "tilt" the treatments such that he could brighten his high end?

I guess I'm more curious as to what degree you can really effect the sound by using treatments.

Can you slightly modify the bass response while at the same time, heavily "increase" the trebel? (or would you actually heavily attenuate the bass to achieve that effect of increased highs?)

Thoughts?

(ya ya ya... I'm at work & it's lunchtime)

To arbitrarily use a figure like "50%" is misleading and inappropriate. We all know Dr. Bose says its at least 90% (joke). But yes, you will alter what you hear.

And yes, you can "brighten" what you hear but this is a very very thin line. The additional brightness would be the result of numerous short-delay reflections which also destroy clairity and definition. You aren't actually increasing the treble engery as you would by active EQ boosting the treble. You should never use EQ for boosting anyway.

One way that I achieve what you mentioned is by the use of polycylindrical masonite panels. The hard surface reflects and diffuses the middle and higher frequencies while at the same time absorbing some bass and helping to break up standing waves. Attenuating the bass while trying to "increase the treble" is fairly difficult to do with acoustic treatments as the same devices that reflect or "trap" the longer wavelengths of lower frequencies also do the same for the higher frequencies.

[DrWho]

To arbitrarily use a figure like "50%" is misleading and inappropriate. We all know Dr. Bose says its at least 90% (joke). But yes, you will alter what you hear.

If I'm recalling correctly, PWK says 90% in the Dope from Hope.

You should never use EQ for boosting anyway.

Boosting and cutting is effectively the same thing in terms of power handling and distortion. Any other argument against boosting should really be an argument against EQ'ing non-minimum phase problems...

In other words, I really feel boosting is totally an acceptable practice. A perfect example would be CD-EQ.

I don't mean to nitpick, but I think it leads to better solutions. For example, using room acoustics to boost the highs is a non-minimum phase solution.