markus111 Posted April 23, 2005 Share Posted April 23, 2005 I've read about the notorious bass dropout in the Klipshorn being somewhere in the 400Hz vicinity. When I measure my Khorns (one at a time) from 1 meter and at listening position, I actually get a giant hole in the bass response centered at 250Hz. At 400Hz, it is even with the rest of the midrange. I have tried it pushed into the corner, away from the wall, using a false corner, nothing seems to make much difference. Does anyone else have this same symptom? It got me to thinking about the evolution of the crossovers. In the AA, there was a single 2.5mH inductor. In the AK-2, there was a 4mH inductor and 140uF cap. In the AK-3, there was a 4mH inductor and 100uF cap. Looking at pictures of the AK-4, it looks more complex yet. Are these crossover evolutions an attempt to fill the hole, or are they due to different bass drivers? What effect do the different low pass filters have on response? Mark Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted April 23, 2005 Share Posted April 23, 2005 Mark, I really doubt of the 250 Hz hole you see is a speaker problem. I think it is more likely to be a measurement error or a room problem. Fact is, 250 Hz is the point of maximum output. The Khorn has a peak around that general area. You can expect the frequency response to go up and down within a 10 dB "window". That is normal. If you dip isn't any biger than 10 dB, it's normal. Also, if you are using a CW singal to measure it you can expect all sorts of peaks and dips. You need to use warble tones or noise to test a speaker properly. The changes in the woofer filter in the various networks was probably done to control phase relationships between the woofer and the squawker at the crossover. Al K. Quote Link to comment Share on other sites More sharing options...
Deang Posted April 23, 2005 Share Posted April 23, 2005 The best way to get the most out that bass bin is to get a good EQ with a built in RTA. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted April 23, 2005 Share Posted April 23, 2005 Dean, did't you post a graphic once about a pair of 68uF nonpolarized caps across the woofer? Rick Quote Link to comment Share on other sites More sharing options...
markus111 Posted April 23, 2005 Author Share Posted April 23, 2005 ---------------- I think it is more likely to be a measurement error or a room problem. ---------------- I kind of wondered about that. I'm using the behringer PEQ 8024 to measure. When I put the measurement mic right up to the horn mouth, the response is pretty flat right out to 500Hz or so. It's when I put the mic anywhere else in the room that I see the dip. But -10db seems pretty huge. Isn't that 1/3 of the volume? I may have some nasty room nodes, but I'll be darned if I can figure out how to get rid of them. There's only so many places that you can move khorns, sofas, etc. Mark Quote Link to comment Share on other sites More sharing options...
markus111 Posted April 23, 2005 Author Share Posted April 23, 2005 ---------------- On 4/23/2005 11:01:09 PM 3dzapper wrote: Dean, did't you post a graphic once about a pair of 68uF nonpolarized caps across the woofer? Rick ---------------- I thought I remembered a post like this also. I'm having a helluva time searching on this forum! Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted April 24, 2005 Share Posted April 24, 2005 Mark, 10 dB is only a huge number on paper! The fact is, you brain completely disregards a narrow dip like that. It actually means nothing! Your brain is far more sensitive to a peak than a dip. Do NOT try to eq it. All you will do is make your amp clip and you WILL hear that. You could even blow your tweeter doing it! Quote Link to comment Share on other sites More sharing options...
Deang Posted April 24, 2005 Share Posted April 24, 2005 I was thinking along of lines of properly EQ'ing the room, not trying to EQ perfectly flat response out of the bass bin (which probably wouldn't sound that good anyways). Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted April 24, 2005 Share Posted April 24, 2005 You said "...When I put the measurement mic right up to the horn mouth, the response is pretty flat right out to 500Hz or so. It's when I put the mic anywhere else in the room that I see the dip..." If the response measures flat in the nearfield (horn mouth) but you see significant anomolies in a farfield measurement, and those anomolies are in the band covered by only that driver, then you are not dealing crossover problems or a faulty component or anything else related to the speaker - you are dealing with something caused by the interaction of the speaker and the room. If the dip was in an area where the midrange and the bass bin were both contributing to the sound, it'd be possible you are seeing something weird having to do with the crossover or the physical relationship between the woofer and midrange. But (uh, I don't think) the midrange in the khorn extends anywhere near as low as 250 Hz. (If I'm wrong about that and the midrange *DOES* go down that low, then my whole post is basically a load of bull$hit. Sorry.) It's unusual for a room interaction to have a significant impact that high in frequency, unless the room is pretty small or has an unusual shape. What's the room like? Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted April 24, 2005 Share Posted April 24, 2005 Ray, I just did a quick computer simulation on the AK-3 network squawker filter. The squawker is only about 5 db down at 250 Hz! It would then be driver interference rather then a crossover glitch. But then, crossover glitches really ARE just driver interference though! By contrast, my ES400 extreme-slope netwrok would be about 29 dB down at 250 Hz! This is why I keep screaming about the driver overlap with conventional gentle-slope networks! Al K. Quote Link to comment Share on other sites More sharing options...
sfogg Posted April 24, 2005 Share Posted April 24, 2005 Mark, " When I put the measurement mic right up to the horn mouth, the response is pretty flat right out to 500Hz or so. It's when I put the mic anywhere else in the room that I see the dip." Repeat your measurements driving the woofer alone directly. If you still see the dip it is room induced. If you don't it is driver interaction. Shawn Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted April 24, 2005 Share Posted April 24, 2005 Shawn, Good idea! Driving the woofer alone will tell you if it's room or driver interaction. AL K. Quote Link to comment Share on other sites More sharing options...
markus111 Posted April 24, 2005 Author Share Posted April 24, 2005 Okay - I did a bunch more measurements. With the woofer run full range (no inductor) the hole is still there, although not as bad! It looks like it may be the room plus the driver interaction perhaps? I tried the mic in several locations, and not surprisingly the response changed at each location. When the mic was 6 inches off the floor, the response was great - so at least I've got that going for me I actually wish this was purely an electrical issue, as those I can fix! Room modes are a big black hole in my understanding. The room is definitely not the most khorn friendly. It is approximately 12 x 20, and the khorns are on the short wall. This is unfortunatly the way that they have to stay if I want to stay married. They are currently toed out away from the corners. I am using false corners with bottoms that I built out of 1" pine. As I mentioned earlier, it makes no difference if the horns are pushed and sealed to the corners or not - the hole is still there. Mark Quote Link to comment Share on other sites More sharing options...
Deang Posted April 24, 2005 Share Posted April 24, 2005 By contrast, my ES400 extreme-slope netwrok would be about 29 dB down at 250 Hz! This is why I keep screaming about the driver overlap with conventional gentle-slope networks! 29db! Now that hole is worse than the one he has, LOL!! For crying out loud Al, he's only 10db down now! Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted April 25, 2005 Share Posted April 25, 2005 Dean, YOU DOPE! I mean the SQUAWKER output will be 29 dB down at 250 Hz!!! Mark, Removing the woofer inductor won't di it! YOu need to disconnect the squawker. How to do that depends on what network you have. If you have the AA, just remove the cable from the barrier block. If you have one of the AK series you will have to unscrew the driver. You could also drape a nich thick blanket over the top section such that it completely covers the squawker horn mouth. The idea is to have the woofer ONLY make the sound. Al K. Quote Link to comment Share on other sites More sharing options...
Deang Posted April 25, 2005 Share Posted April 25, 2005 LOL, hey, any chance I get to muddy the waters a little, I'm going to take it. Quote Link to comment Share on other sites More sharing options...
markus111 Posted April 25, 2005 Author Share Posted April 25, 2005 ---------------- On 4/25/2005 6:05:00 AM Al Klappenberger wrote: Dean, YOU DOPE! I mean the SQUAWKER output will be 29 dB down at 250 Hz!!! Mark, Removing the woofer inductor won't di it! YOu need to disconnect the squawker. How to do that depends on what network you have. If you have the AA, just remove the cable from the barrier block. If you have one of the AK series you will have to unscrew the driver. You could also drape a nich thick blanket over the top section such that it completely covers the squawker horn mouth. The idea is to have the woofer ONLY make the sound. Al K. ---------------- I should have clarified that - I disconnected the woofer from the network and hooked the woofer directly to the amp, with no squawker or tweeter. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted April 25, 2005 Share Posted April 25, 2005 Mark, Ok.. If the woofer is the only thing making the sound, it's the room! If it's a real narrow glitch, forget about it! There's nothing you can do except rearange the furnature and that will probably just move the glitch to some other spot in the room! AL K. Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted April 25, 2005 Share Posted April 25, 2005 Another perspective on this one. At 250 Hz the wavelength is over 4 ft. With wavelengths this large, there is generally very little absorption by curtains & carpets. It is the room geometry that is dictating much of the response that is received - there will definitely be resonances and dips as the waves and reflections add together (constructively and destructively). With a continuous pure tone, 10 to 20 dB variations are not unusual especially in a small room. This is easily verified by finding the location of a relative dip and then moving the mic about a 1/2 wavelength away (about 2 ft in a direction realtive to the nearest wall). Using a third octave band of noise will diminish the fluctuations (as to be expected: the broader the signal the less the variation). I would not worry about the contribution of energy coming from the mid-range driver since it contributes considerably less to the overall level at this low frequency ( I can't remember the roll off, but if it is more than several dB down from the woofer it would offer very little cancellation even if it were 180 deg out of phase). Attempting to equalize is highly problematic. As an exapmle I was listening to a 1000 Hz tone the other day (remember the wavelength is 13 inches) and none of us would consider this to be a "low frequency" tone. This was done over a sigle K-Horn in a typically furnished & carpeted living room (12 x 18 and with many openings into halls and adjacent rooms). Moving my head 1/2 foot or so in various directions had a very appreciable impact. Using the relation that the perceived level of sound "doubles" when the physical level increases by about 10 dB, then I was getting changes in level of close to 10 dB. This is a folksy measure, and continuous pure tones are not music; however it does show the burdensome influence of room acoustics. How could one ever hope to equalize. Would you even try to do that. And remember this as at 1000 Hz (close to 2 octaves above "middle C"). The problem will be worse at lower frequencies. Room acoustics are frustrating, and not easily tamed. All in all, relax, put the microphone away and enjoy the music. -Tom Quote Link to comment Share on other sites More sharing options...
JohnA Posted April 28, 2005 Share Posted April 28, 2005 Hi Ray! haven't seen you in a while. Doin' good? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.