Almost every 2,5 speaker has too hot bass! they complely forget the room effect int their designs. But there are millions of people that like that kind of bass! Here is a very good example of a very very well designed speaker, I am sure that bass boost is not an accident! When you see 2-4 bass drivers, you must hear lots of bass!
That looks like a curve from Stereophile. He splices nearfield or dustcap woofer measurements with farfield upper range. The nearfield woofer measurement shows what 2 pi response (flush in an infinite baffle) would be, rather than free field response.
Most commercial speakers are designed to be 4 pi flat and would show a similar bass rise under those measurement conditions.
David
Agreed, but a gentle "tilted straight line" slope is desirable, not a +6dB bass hump
Yes that is the Stereophile response of PSB. JA tells that perhaps 3dB boost in this kind of graph would be ideal. Some of the measured speakers have more some less boost. Listening impression was "it was deeper and more powerful than I would have expected, given the driver complement and the size of the cabinet." (how do we interprete that
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Stereophiles mid and upper region is average of 0-15¤ (30¤ window) This kind of response should be slowly sloping towards highs, like davidrsb said.
)Stereophiles mid and upper region is average of 0-15¤ (30¤ window) This kind of response should be slowly sloping towards highs, like davidrsb said.
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I wouldn't be so sure about that. The Olive study I referred to shows a pretty bumpy preference curve. But then they only allowed for a fixed frequency range to be adjusted.
Something I'm trying to learn but will never master, so looking to choose well behaved drivers and keep the x/o simple. Also the cabinet shape can help as you pointed out, also a sloping baffle (10 plus degrees) can help a little
If a baffle is curved to the point where there is little flat surface, wd that help ?
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Anyone got the schematic for Rod Elliott's variable BSC circuit?
His website has been very intermittent of late.
Would I be able to operate it as a balanced circuit? - my PA tops are designed for half-space use, but are frequently put up on stands, ie, full-space.
If not, I'll just use a graphic eq. Having the BSC at the twist of a dial would be nice, though.
Cheers
Chris
Edit - nevermid, found it on Google
I know there's a relevant equation for calculating the capacitor value. Anyone have it on-hand?
His website has been very intermittent of late.
Would I be able to operate it as a balanced circuit? - my PA tops are designed for half-space use, but are frequently put up on stands, ie, full-space.
If not, I'll just use a graphic eq. Having the BSC at the twist of a dial would be nice, though.
Cheers
Chris
Edit - nevermid, found it on Google
I know there's a relevant equation for calculating the capacitor value. Anyone have it on-hand?
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This PSB has a very complex bass system. JA's response has summed response of all bass drivers and ports, which can explain the difference to NRC measurement. NRC response is measured at 2m in anechoid chamber (spl corrected to 1m).
Notice different scale! NRC response shows some 3dB bump at 80-130Hz, instead of the 6dB bump in Stereophile response. Both shown here are average of 0-15¤ hor.
To my experience, nearfield response in pretty close to what we get in a typical room placement.
Another thing that means a lot is where bass drivers and ports are located. This PSB should in theory have a very well balanced and even bass unless placed too close to front wall or corner.
This is NRC measurement of PSB Platinum T6 (listening window) Notice the difference in bass response! T6 is older design with 3 bass drivers. This kind of response in anechoid measurement gives flat bass in a room. (And that is generally said to be dry, clean and perhaps lean)
Notice different scale! NRC response shows some 3dB bump at 80-130Hz, instead of the 6dB bump in Stereophile response. Both shown here are average of 0-15¤ hor.
To my experience, nearfield response in pretty close to what we get in a typical room placement.
Another thing that means a lot is where bass drivers and ports are located. This PSB should in theory have a very well balanced and even bass unless placed too close to front wall or corner.
This is NRC measurement of PSB Platinum T6 (listening window) Notice the difference in bass response! T6 is older design with 3 bass drivers. This kind of response in anechoid measurement gives flat bass in a room. (And that is generally said to be dry, clean and perhaps lean)
An externally hosted image should be here but it was not working when we last tested it.
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The flat NRC curve shows that the BSC is spot on. It also means that in real rooms, there will be a big bass peak as floor and rear wall reflections do their work
There will also be dips and this is where the whole discussion about baffle step compensation for anechoic chambers becomes moot. We hear the speaker and the room. The baffle step becomes rather meaningless. Meaningful is what happens within a specific room.
Baffle step (loss), floor gain and cancellation, front wall gain and cancellation, baffle diffraction, driver directivity etc. physical phenomenoms fight, they don't really compensate
It is common practise (for diyers) to use 6dB BSC (baffle step correction) for standmounted or big freestanding speakers, 3dB BSC for those who are supposed to be placed near front wall and 0dB BSC for soffit mounting or in-shelf bookshelf speaker. This is because BS is -6dB, floor gain is +3dB and wall gain is +3dB.
The problem is like markus said, that all these have different knees (Fc) and that floor and front wall also make a sharp cancellations (of which the first is of greatest importance).
Many active speakers (monitors) come with switches to adjust low bass, mid bass and tweeter level. Sometimes also the corner frequency can be selected.
Even more sophisticated way is to use programmable DSP, but then the end user (or the seller of some high-end speakers) must make measurements and adjut dsp. There are also dsps with automatic equalization (eg.Audyssey)
These equalizations get even more complicated when we add room modes, ceiling, sidewall and backwall reflections...
And this gets even more complicated when we realize that even a small move of the speaker of listener (mic) changes all of these!
Room acoustic treatment is often needed after the best compromise of speaker placement and listener location is decided.
All in all - we need to have speakers with different radiation pattern, different BSC. The user must realize all these factors to make the best match of speakers and the room. DSP equalization has a small role but mainly for the room eigenmodes and minor smoothing/tilting/voicing of response . DSP/EQ does not change reflections and radiation patterns. (A DSP-based "active" crossover and equalization per driver is a different story!)
It is common practise (for diyers) to use 6dB BSC (baffle step correction) for standmounted or big freestanding speakers, 3dB BSC for those who are supposed to be placed near front wall and 0dB BSC for soffit mounting or in-shelf bookshelf speaker. This is because BS is -6dB, floor gain is +3dB and wall gain is +3dB.
The problem is like markus said, that all these have different knees (Fc) and that floor and front wall also make a sharp cancellations (of which the first is of greatest importance).
Many active speakers (monitors) come with switches to adjust low bass, mid bass and tweeter level. Sometimes also the corner frequency can be selected.
Even more sophisticated way is to use programmable DSP, but then the end user (or the seller of some high-end speakers) must make measurements and adjut dsp. There are also dsps with automatic equalization (eg.Audyssey)
These equalizations get even more complicated when we add room modes, ceiling, sidewall and backwall reflections...
And this gets even more complicated when we realize that even a small move of the speaker of listener (mic) changes all of these!
Room acoustic treatment is often needed after the best compromise of speaker placement and listener location is decided.
All in all - we need to have speakers with different radiation pattern, different BSC. The user must realize all these factors to make the best match of speakers and the room. DSP equalization has a small role but mainly for the room eigenmodes and minor smoothing/tilting/voicing of response . DSP/EQ does not change reflections and radiation patterns. (A DSP-based "active" crossover and equalization per driver is a different story!)
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I`m considering Baffle Step to even effect the midrange as if you see the way the correction curve requires some of its upper part of the baffle step is felt even at the low midrange as well. I feel just increasing the size of inductor will not help in here. Can anyone express your thoughts on this please.
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Dont use a separate BSC circuit, too much heat and current. Just measure your Drivers and make a normal 3 way crossover and account for the variation,