Funny about definitions... I (being a loudspeaker nerd) once had a discussion with a singer who just had learned about frequencies. She talked about the "highest treble" and I automatically thought about frequencies above 10 kHz. It turned out that she ment frequencies around 1000 Hz, because that is the fundamental of the very highest notes that females sing.
So I think there is a discrepancy between what musicians and technicians mean by treble and midrange. The way I cope with that is to clarify what frequencies I mean rather than speaking about ranges. (I looked back in my previous post and, phew, indeed I did that
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Possibly this discrepancy has an historical explanation; the first sound reproduction devices had a very limited frequency response, it might very well have ended at 2-3 kHz. Calling the highest frequencies "treble" would then have been highly appropriate, but as the technology advanced, maybe the "technical registers" were shifted upwards?
This is pure speculation, of course.
So I think there is a discrepancy between what musicians and technicians mean by treble and midrange. The way I cope with that is to clarify what frequencies I mean rather than speaking about ranges. (I looked back in my previous post and, phew, indeed I did that
)Possibly this discrepancy has an historical explanation; the first sound reproduction devices had a very limited frequency response, it might very well have ended at 2-3 kHz. Calling the highest frequencies "treble" would then have been highly appropriate, but as the technology advanced, maybe the "technical registers" were shifted upwards?
This is pure speculation, of course.
Well, one good speculation deserves another, so I think the idea of the midrange being shifted up has it's origin in the cost of crossover components.
If you take a look at the classic three-ways from the seventies and before, You will likely find the following in the box:
1) An 8", 10" or 12" woofer crossed over to a midrange at 800 or 900 Hz
2) A 4" midrange crossing over to a tweeter at 4,000 or 5,000 Hz.
C) A 1 inch tweeter handling the high ranges.
Remember that the lower the crossover point, the more expensive inductors and capacitors become. So there would be a substantial saving in pricing for components if the midrange comes in at 900 Hz or so instead of 200 Hz or so.
After a few years of this, it is no wonder that people in the sound field think of "the midrange" as being from 900 Hz up to 4 KHz or higher-that is the range the midranges in all the three way speakers played in!
If you take a look at the classic three-ways from the seventies and before, You will likely find the following in the box:
1) An 8", 10" or 12" woofer crossed over to a midrange at 800 or 900 Hz
2) A 4" midrange crossing over to a tweeter at 4,000 or 5,000 Hz.
C) A 1 inch tweeter handling the high ranges.
Remember that the lower the crossover point, the more expensive inductors and capacitors become. So there would be a substantial saving in pricing for components if the midrange comes in at 900 Hz or so instead of 200 Hz or so.
After a few years of this, it is no wonder that people in the sound field think of "the midrange" as being from 900 Hz up to 4 KHz or higher-that is the range the midranges in all the three way speakers played in!
It's been good to read all the replies, and it's obvious that my use of the term "overported" doesn't describe what I mean.
My situation: I have 2 x Vifa M22s in 65 litres, ported (85mmx190mm), tuned to 32hz.
The low end sounds great most of the time but on some discs, the bottom octave seems too full. Discs like Sinatra & Basie's "It Might As Well Be Swing" when the double bass kicks in sound far too big, albeit tight. Also noticed this on some other discs where there is double bass.
Now, I've considered the idea that there's nothing wrong with my alignment and that it's only certain discs that have the problem. But I still have a nagging doubt that all is not as it should be.
NB: I read an interesting piece in Stereophile by John Atkinson where he made comment that many speakers go low enough to reproduce frequencies that weren't heard in the recording studio during production. This seems like a failing in the recordings as spurious low notes could easily detract from the enjoyment of the music as they seem to be doing in my case.
My situation: I have 2 x Vifa M22s in 65 litres, ported (85mmx190mm), tuned to 32hz.
The low end sounds great most of the time but on some discs, the bottom octave seems too full. Discs like Sinatra & Basie's "It Might As Well Be Swing" when the double bass kicks in sound far too big, albeit tight. Also noticed this on some other discs where there is double bass.
Now, I've considered the idea that there's nothing wrong with my alignment and that it's only certain discs that have the problem. But I still have a nagging doubt that all is not as it should be.
NB: I read an interesting piece in Stereophile by John Atkinson where he made comment that many speakers go low enough to reproduce frequencies that weren't heard in the recording studio during production. This seems like a failing in the recordings as spurious low notes could easily detract from the enjoyment of the music as they seem to be doing in my case.
If one or both of the speakers are anywhere near a corner, the corner boosts the Fb frequency highest, and surrounding frequencies to a lesser degree. So if some of the recordings you listen to have some notes within a quarter octave of your Fb tuning frequency, and your port is near a corner, you might end up with some bass notes overemphasized.
By the way, what is your Fb, (tuning frequency)? Failing that, what is the interior dimensions of your enclosure, and the diameter and length of your port?
By the way, what is your Fb, (tuning frequency)? Failing that, what is the interior dimensions of your enclosure, and the diameter and length of your port?
Tuning freq. is actually 31.3. LspCAD calculates the F3 at 37hz. FS of driver is 30hz.
Port is front mounted, and front baffle is 1 meter from both the rear and side walls.
Cabinets have curved sides, 430mm deep, 230(front)-100(rear)mm wide, and 700mm tall. Internal dimensions.
I have the internal walls temporarily lined with 10mm carpet foam.
Port is front mounted, and front baffle is 1 meter from both the rear and side walls.
Cabinets have curved sides, 430mm deep, 230(front)-100(rear)mm wide, and 700mm tall. Internal dimensions.
I have the internal walls temporarily lined with 10mm carpet foam.
Well, as you can see from the chart below, taken from this webpage, the contrabass is one of the few instruments capable of reaching down to your tuning frequency. The piano and pipe organ are the others. I don't how much deep pipe organ music you listen to-if you listen to Basie and Sinatra I suspect not very much-and the piano is not usually played down there, even if it is capable of going that low.
A speaker is considered acoustically coupled to a corner if the frequency being reproduced has a wavelength ten times or greater than the distance to the corner. You are 39 inches, (1 meter) from the corner. 31 Hz has a wavelength of 435 inches, so the contrabass' low output is definitely coupled to that corner.
It seems highly unlikely that it is just coincidence that you are having problems with the only instrument likely to be played down to the where your Fb is, especially since the speaker reproducing those very low notes is acoustically coupled to the corner.
A speaker is considered acoustically coupled to a corner if the frequency being reproduced has a wavelength ten times or greater than the distance to the corner. You are 39 inches, (1 meter) from the corner. 31 Hz has a wavelength of 435 inches, so the contrabass' low output is definitely coupled to that corner.
It seems highly unlikely that it is just coincidence that you are having problems with the only instrument likely to be played down to the where your Fb is, especially since the speaker reproducing those very low notes is acoustically coupled to the corner.
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a bass trap is an item placed in the room to remove bass. it has nothing to do with your box. If I was you I would simply play with the positioning of the speakers, I would also experiment with different amounts and types of damping material inside the box, combinations of say pollyester and carpet underlay until you find your ideal. pollyester and fiberglass will change the effective volume of the box, placing these materials inside the box actually tricks the driver into acting as if it is a bigger box! this is an easy way to modify tuning of the ports, without touching the pvc pipe.
I do not know how the material you now use affects volume.
Personally I enjoy this stage and hearing the variations until well it sounds just right!
I do not know how the material you now use affects volume.
Personally I enjoy this stage and hearing the variations until well it sounds just right!
Member
Joined 2003
I have several recordings with ultra low-bass glitches like doors slamming down the hallway, HVAC noise, etc, that obviously wasn't noticed in the studio. As John states, it is incredibly distracting to have the sofa unexpectedly shake in the middle of a jazz set, but the cause is very obvious...nothing as subtle as you're experiencing.
Speaking of obvious, have you tried temporarily plugging the ports? Quick and easy to try, and should come close to a very low-Q sealed box.
Speaking of obvious, have you tried temporarily plugging the ports? Quick and easy to try, and should come close to a very low-Q sealed box.
How would you plan to measure something without measuring equipment?
I guess measuring the Qtc would not be too hard or involve a lot of equipment.
Also, remember that in a closed box, both free air resonance, Fs, and free air Q, (Qts), become Fc and Qtc respectively and rise according to the following formula:
Fc = sq rt [(Vas/Vb) + 1] X Fs
Same formula for Qts and Qtc
Below is a graph for two Vifa M22 WR-09 in a 65 liter box, sealed and ported to 31 Hz. The Qtc is 0.54. The other Vifa M22's WinISD listed were far to high in Qts, (0.7), for it to be them.
Incidentally, from as far back as the 1950's Novak of Jensen speakers wrote that the way to make a good ported box was to make a sealed box with a Qtc of around 0.5, then port it. His article, though published in the JAES, received little attention until Thiele and Small's article was published. The Qtc should be just a tad higher than 0.5, but not enough to make much of a difference.
People don't realize it, but for all practical building purposes, the ported box was solved before Thiele-Small's work-although they went into it in much, much greater detail than Novak did.
I guess measuring the Qtc would not be too hard or involve a lot of equipment.
Also, remember that in a closed box, both free air resonance, Fs, and free air Q, (Qts), become Fc and Qtc respectively and rise according to the following formula:
Fc = sq rt [(Vas/Vb) + 1] X Fs
Same formula for Qts and Qtc
Below is a graph for two Vifa M22 WR-09 in a 65 liter box, sealed and ported to 31 Hz. The Qtc is 0.54. The other Vifa M22's WinISD listed were far to high in Qts, (0.7), for it to be them.
Incidentally, from as far back as the 1950's Novak of Jensen speakers wrote that the way to make a good ported box was to make a sealed box with a Qtc of around 0.5, then port it. His article, though published in the JAES, received little attention until Thiele and Small's article was published. The Qtc should be just a tad higher than 0.5, but not enough to make much of a difference.
People don't realize it, but for all practical building purposes, the ported box was solved before Thiele-Small's work-although they went into it in much, much greater detail than Novak did.
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Hard to believe the industry went all those years having the closed box solved, but not having a clue about the ported box. They knew all about Qtc and such.
The closed box was considered supreme for hifi until 1980 or so. Before then, the ported box was considered a boom box, largely due to the mistuned units being sold at the time.
Novak's paper came out in the mid fifties. And you would think that once you had the closed box figured out, someone would just go down the line with various closed box Qtc's and port them to see what sounded good. Yet they went for years and years before the ported box was finally considered fully understood.
The closed box was considered supreme for hifi until 1980 or so. Before then, the ported box was considered a boom box, largely due to the mistuned units being sold at the time.
Novak's paper came out in the mid fifties. And you would think that once you had the closed box figured out, someone would just go down the line with various closed box Qtc's and port them to see what sounded good. Yet they went for years and years before the ported box was finally considered fully understood.
I am just finishing a set of vented enclosures for my Jordan JX92S.
Two pairs of ears and the room calculator shows my room to have a dip at 100Hz to 200Hz, so I tuned the port for a little boost here. The boost worked, but the rest of the bass did not. Lengthening the port to match the driver/box resonance tightened it all up, with no lessening of the overall effect, just an occasional brain alert when a running bass line wanes and waxes again.
I guess that the boost is best implemented by electronics.
Two pairs of ears and the room calculator shows my room to have a dip at 100Hz to 200Hz, so I tuned the port for a little boost here. The boost worked, but the rest of the bass did not. Lengthening the port to match the driver/box resonance tightened it all up, with no lessening of the overall effect, just an occasional brain alert when a running bass line wanes and waxes again.
I guess that the boost is best implemented by electronics.
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