Boomy bass in Klipschorns

[mr-b]

Hi

I've just acquired a pair of Klipschorns ('88) with AK-2 crossovers to

replace my previous LaScalas. They sound a lot fuller than the LaScalas

at both ends of the spectrum, but they do seem to have a very

pronounced boomy bass at certain freqs.

This is most noticeable with any bass guitar sound, which tends to dominate and sounds bloated or flabby.

I've tried varying source, amp and room position (pulling them well out of the corners) but it still remains.

Any ideas what could be wrong or what to test next?

[seti]

What is your system profile amp / preamp etc ?

[PrestonTom]

Hello MrB,

The definition of "boomy" probably means different things to different people. However, various aspects of the bass should have changed when you moved the K-Horns out of the corners. I assume they were tight in the corners initially.

If the "boominess" is dramatic (not subtle) I would not worry about amps, crossover (if it works correctly) and wiring. However, I would direct your attention to the source material since the K-Horns should have a very accurate bass reproduction (is the source/recording "boomy").

Further, and this is more likely, I would try changing your listening position to see if this changes things. I mention this because room acoustics are a very likely culprit (esp for frequencies below 400-500 Hz).

God Luck,

-Tom

[tofu]

i have the same problem, but with my scalas. it's more of a midbass problem, though. i don't have any bass traps in my room yet, but i've learned to live with it until then.

it's very evident on songs like "come together" by the beatles.

[Colin]

never heard Khorn bass described as boomy before, probably is the room, any measurements?[H]

[D-MAN]

I too would think that you're exciting some here-to-fore unnoticed low frequency room modes. That is a room dependent thing. Absorption is possibly required.

Ensure that the bass bins are flush to the corners with no air leaks, that creates a boominess as well as "bad bass", of course.

DM

[jdm56]

I agree that it is almost certainly a room issue. If your rooms resonant modes are not evenly distributed, you WILL have boomy bass with a k-horn pair sitting in the corners. The corner placement excites all room modes, so basically you are at the mercy of the room! A good room geometry will yield smooth and powerful bass from k-horns, while a too square room, for instance, will be boomy at some frequencies and thin at other's.

[DrWho]

Would you describe this boominess as more like a tubby sound? If so,

every pair of khorns I've heard has the same problem (including rooms

with very good acoustics). So I wouldn't be too quick to blaim the room

right away. Do you notice this same boominess with other speakers

positioned at the same location? If not, then that confirms even

further that it's probably the speakers and not the room.

There will be many on the forum that passionately disagree with this

viewpoint and you can imagine the possible reasons for it. I should

probably mention that the problem isn't as noticeable with jazz and

classical recordings, but with rock it becomes ever more apparent and

makes the listening most unenjoyable. Some will want to blaim the

source material as being the faulty link, but we have no control over

our source material and must build our systems around that to which we

listen. But I do want to point out that these so called tubby

recordings have no hint of it on any of the other hundreds of systems

I've listened to.

So that said, what kind of music are you listening to? If you're into

rock then I might suggest you look into a pair of cornwalls...

Btw, you do realize that the khorn was built such that the corner of

the room finishes the flare rate of the bass horn....so you have to

tuck them into the corner and make a good seal with the tailboard. You

mentioned pulling them out into the room and this simply won't work

with these speakers.

[3dzapper]

mr-b, Khorns have a prodigious amount of very very effecient bass and go almost an octave lower than LaScalas. You don't be any chance have a loudness control on do you? Fletcher/ Munsen is out the window with Khorns, they are too effecient. You have no control over the curveof the bass/treble emphasis with F/M loudness on.

Just a thought.

Rick

[DrWho]

Fletcher/ Munsen is out the window with Khorns, they are too effecient.

F-M curves have absolutely nothing to do with the sensitivity of the system.

[3dzapper]

Grasshopper, The F/M curves dictate the bass/treble boost to compensate for the human ear relative to volume. An amplifier does not know the sensitivity of the speakers connected to it so the designers will build for the average sensitivity speaker +/-85db @ 2.83V/1 meter. Although F/M curves are set, the amount of amplification necessary to attain them with 104db sensitive speakers is far less than that necessary for the design average.

Because of this, PWK specifically recommended that the loudness contour not be used. If any bass boost should be desired, he said to the effect, that "it is more accurate to use the manual control.

It is in the Dope From Hope papers if you are interested.

Rick

[homemade]

I'll bet the boomy bass is actually too much bass in the 125hz range. By adding a subwoofer to my system it has become more balanced and I notice the effect less. One could use an eq. to reduce that part of the sound spectrum too. 4-6db cut in the 125hz band will do wonders. Too many design compromises and resonances in the speaker and perhaps room to keep that band tamed down.

[DrWho]

Grasshopper, The F/M curves dictate the

bass/treble boost to compensate for the human ear relative to volume.

An amplifier does not know the sensitivity of the speakers connected to

it so the designers will build for the average sensitivity speaker

+/-85db @ 2.83V/1 meter. Although F/M curves are set, the amount of

amplification necessary to attain them with 104db sensitive speakers is

far less than that necessary for the design average.

Because of

this, PWK specifically recommended that the loudness contour not be

used. If any bass boost should be desired, he said to the effect,

that "it is more accurate to use the manual control.

It is in the Dope From Hope papers if you are interested.

The loudness button will affect the frequency response the exact same

way regardless of the amplifiers output. A loudness button that adds

6dB from 100Hz and below will always add 6dB regardless of where the

volume dial is located or how many watts are being pushed. (a loudness

button is really just a fixed bass shelf filter...nothing super fancy).

There are a few amps that I can think of with a variable loudness

feature that change the amount of attenuation with the volume dial

(instead of a fixed EQ), but they usually have a calibration knob to

fine tune the amount of loudness shift corresponding to the volume

knob. If they're going to go through all the trouble with variable

loudness, then they are probably going to spend the extra dollar to

make it useful.

I suppose there might be amps with variable loudness built in, but I

would be curious to know which model amps are doing this. If they are,

it would actually be really simple to wire in a knob to fine tune it to

your speakers [] (I think in most cases it could be done with a single L-Pad between the volume knob and bass shelf filter).

[homemade]

I would say that most components with loudness comp. circuits are always variable. Even cheap car stereos that had a loudness control were variable-just not adjustable. Most of them were calibrated to cancel out any bass and treble boost past 1/2 volume or so. If I remember correctly, look at a Radio Shack catalog and many volume controls have a loudness tap built onto them.

[DrWho]

Hmmm, I'll have to go look at a few more circuit diagrams...I have

always experienced that they weren't variable and we were always taught

in school that they weren't variable (but wouldn't be the first time a

professor was wrong) []

[3dzapper]

Most amps do have variable loudness circuits. The one in this link uses a simple opamp circuit. It could easily be built on one chip. http://www.redcircuits.com/Page67.htm

In days of yore with tube integrated amps or pre-amps, the variable loudness was obtained by inserting a resistor/capacitor circuit off a point fixed at approx 25% up the volume pot. When the wiper reached a point above (less resistance on the signal/louder) the contour circuit was removed from the equasion.

Rick

Wow! i can't believe I took that much time finding that schematic, looking at others and typing this post! it's late.

[DrWho]

Hmmm, that circuit worries me because you actually don't need HF

attenuation according to the F-M curves. If you look at the chart you

will notice that the high frequencies need to be louder compared to the

1kHz signal. BUT, the difference between the high frequencies and 1kHz

are the same through all volume ranges. For example, 10kHz needs to

always be 10dB louder for every reference volume between 0dB and 90dB. It is only

at volumes greater than 90dB that 10kHz specifically becomes an issue

(ever notice the high hat and cymbals on the drums seem to really

pierce when you blast at insane levels?) Anyways, my point here is that

the higher frequencies will have already been compensated for in the

studio and you don't need an extra EQ to compensate.

The key to reading the F-M curves is in the difference between

reference SPL's....not the specific changes along the same reference

SPL!

The opposite effect happens on the low end of the spectrum where less

attenuation is needed when the volume is increased...so unless I'm

reading the circuit wrong, I don't think it's properly integrating a

true loudness countour...

[3dzapper]

Hey Who, I don't know if you noticed or not. By looking at the F/M chart you can see that many "high end" speakers have a frequency response plot that closly matches the F/M curve at 100db. Slightly accentuated bass, a "softer presence range, and a "crisper" HF response.

(This one does not have the 15KHz rise that some do)

Actually it seems I am wrong, almost everyone I have clicked has a restricted cut-off HF in the 10-20KHz range? This one is a B&W 800:

Rick

[3dzapper]

"the difference between the high frequencies and 1kHz are the same through all volume ranges."

That is just a cheap basic circuit. Like what you would find on a boom box. Most people are more concerned with the compensation for loss of bass or bass boost in and of itself and could care less about the highs. Remember those of us who really care about the sound quality of our music are but a small population in the universe of listeners. Thus the Bloze customer.[]

Rick

[DrWho]

Only cuz "audiophiles" claim to have golden ears and pride themselves

in listening at low volumes [] Of course audiophiles can't have any

extra EQ circuitry so the speaker manufactures just implement the

loundess curve with the speaker itself. At lower volumes a non-flat

speaker definetly sounds better!

I still think a boosted HF range is completely unnecessary....if anything you would want HF reduction only at volumes above 90dB!

The cornwalls have a similar slope and that is probably why they sound

better at lower volumes. Though there is a point where when you're

really really cranking it that the bass response seems to flatten

out....which is probably more due to room acoustics and power

compresssion.

Ideally we would have a tag sitting on the header of our CD players

that stores the volume at which the CD was mastered in the studio. This

data would then get sent to our amplifier (or wherever the volume

control is being implemented) that has a calibration knob, which we

would only have to set once to indicate where say 80dB SPL corresponds

to the volume dial (it really doesn't matter exactly what SPL because

the correction can be extrapolated from any reference). This approach

would allow the entire attenuation to be automated and we wouldn't have

to recalibrate between recordings mastered at different volumes. With

such a system we could then design our speakers with a flat response

and they would sound fine at any volume...though the audiophile dopes

will still have issues with the extra circuitry.