Yesterday i heard several cardioid subwoofer systems for a big audience (40K). I found the bass to be cartoonish, like old batman cartoons "Whack" & "Boom" one note. If you could improve the sound quality of a cardioid subwoofer array? How would you go about it? If sound quality was number one. Closed box, bigger bandwidth, improve spacing? All physical option in the design of the line itself, without sacrificing directivity, what would be possible?
Hi,
Few Q's for you first...
Were you the system engineer that set this rig up?
If not, how do you know it was the cardioid part of the setup that caused the particular sound you're querying?
Have you heard the same rig, in the same space, with the same band, just not cardioid before?
The thing is, there are lots of factors that can influence the end sound of a rig. Done right, there's nothing inherent to the cardioid setup that should cause what you're describing.
The main differences between cardioid and standard setups should be firstly, the reduced bleed to the rear and possibly thus reducing some reflections off walls.
Secondly, depending on the exact implementation, there may be a slight loss of "tightness" due to the time arrival of sound from the rear boxes not exactly matching that from the front boxes.
Third is that there may be a notch in the frequency response just above the intended bandwidth of the system, which does mean that you're often limited to a slightly lower crossover frequency from subs to mains. In large venues that's not normally a problem as the mains you would choose to use almost always go low enough to cover this part of the spectrum anyway, but it is something to be aware of.
HTH,
David.
Few Q's for you first...
Were you the system engineer that set this rig up?
If not, how do you know it was the cardioid part of the setup that caused the particular sound you're querying?
Have you heard the same rig, in the same space, with the same band, just not cardioid before?
The thing is, there are lots of factors that can influence the end sound of a rig. Done right, there's nothing inherent to the cardioid setup that should cause what you're describing.
The main differences between cardioid and standard setups should be firstly, the reduced bleed to the rear and possibly thus reducing some reflections off walls.
Secondly, depending on the exact implementation, there may be a slight loss of "tightness" due to the time arrival of sound from the rear boxes not exactly matching that from the front boxes.
Third is that there may be a notch in the frequency response just above the intended bandwidth of the system, which does mean that you're often limited to a slightly lower crossover frequency from subs to mains. In large venues that's not normally a problem as the mains you would choose to use almost always go low enough to cover this part of the spectrum anyway, but it is something to be aware of.
HTH,
David.
Hi,
No not my setup, just visiting a festival and wondering about the boom & whack. Not heard the same system anywhere else. So very little information about the system itself. just wondering how you could physically prevent the one note sound. There is alot of info about setting up subwoofer arrays, but very little about sound quality. Wondering if a closed box could help reduce the phase problems. I know closed box is not usefull for PA. But still wondering, what if?
No not my setup, just visiting a festival and wondering about the boom & whack. Not heard the same system anywhere else. So very little information about the system itself. just wondering how you could physically prevent the one note sound. There is alot of info about setting up subwoofer arrays, but very little about sound quality. Wondering if a closed box could help reduce the phase problems. I know closed box is not usefull for PA. But still wondering, what if?
A "one note sound" in a modern large scale PA is almost certainly not the result of using a cardioid setup.
Look elsewhere for the cause.
Likely suspects: The band's engineer likes it that way, or is inexperienced enough not to realise their mix decisions are causing it.
Look elsewhere for the cause.
Likely suspects: The band's engineer likes it that way, or is inexperienced enough not to realise their mix decisions are causing it.
A kick drum that will part your hair at 100ft seems to be the preferred setup for all too many FOH engineers these days, and getting that can result in... cartoon like one note bass in some cases. But there is nothing inherently one note about the performance of modern high end pro audio subwoofers in fact they have never been more capable in terms of bandwidth/ LF extension, so your experience is most certainly a result of the BE's mixing choices and/or the venues acoustics and/or your listening position.
Ok, understood clearly i heard a badly tuned system. But how would you go about physically tuning a cardioid subwoofer line for sound quality? In some cases the woofer at the back of a cardioid is smaller / differently tuned compared to that of the front woofer. A vented system has some phase problems down below. Am i wrong about my hunch that a closed box would prevent phase problems? Since it would have less phase problems. Just trying to learn by asking "stupid" questions. I know a closed box would never work for PA.
OK, so in the general sense, yes, a closed box will have less phase shift and thus group delay than a vented box. There is still some phase shift though, so it's not as black & white as to be able to say it would prevent phase problems entirely.
But, as I think you know already, the loss of efficiency that goes along with it means that is not a useful compromise for PA, so we live with it.
Maximising sound quality in a commercial PA subwoofer involves all the usual design decisions: How low do we want to go, how loud, how big a box can we carry around.
Then pick a driver that fits the intersection of those criteria.
Make sure it comes from a reputable manufacturer and has high power handling and excursion to let you drive it hard without too much distortion.
Pick a vent tuning frequency that controls excursion as well as possible without needing too high an HPF frequency (as that limits bass extension and increases phase shift at the same time).
Make the vents big enough (and/or use flared vents) to minimise port non-linearities (particularly audible "chuffing").
After that, it's just EQ and integration with the main PA.
Ideally, get the sub itself flat, and get good phase matching with the mains for at least an octave or so at the crossover point, as getting this wrong can lead to cancellation of output.
Then it's just voicing to suit the taste of whoever is mixing the gig. Some engineers do go for the "haystack" approach to LF where the entire sub signal is boosted 10-20dB above the mains, others will prefer a flatter system and just apply EQ on a per-channel basis if they want extra impact for things like a kick drum.
All of the above would be exactly the same for cardioid or standard setups.
There are a couple of different ways that the directional behaviour can be created which do have slightly different compromises - some do have more phase/timing issues than others, so choosing how to get directionality can be a part of the sound quality decision making.
In general, we don't need to try and get 100% cancellation behind the subs, which is why we don't need equal numbers/sizes of drivers for the rear parts - if using multiples of one box type, a common ratio is 2 forward : 1 back; or for single box solutions like d&b's V & Y subs there might be a smaller driver chosen for the rear part. The important part is that the rear source has the same frequency and phase response as the front part - if d&b's designers are good enough to achieve that for the bandpass rear sections of those subs, then more power to them.
HTH,
David.
But, as I think you know already, the loss of efficiency that goes along with it means that is not a useful compromise for PA, so we live with it.
Maximising sound quality in a commercial PA subwoofer involves all the usual design decisions: How low do we want to go, how loud, how big a box can we carry around.
Then pick a driver that fits the intersection of those criteria.
Make sure it comes from a reputable manufacturer and has high power handling and excursion to let you drive it hard without too much distortion.
Pick a vent tuning frequency that controls excursion as well as possible without needing too high an HPF frequency (as that limits bass extension and increases phase shift at the same time).
Make the vents big enough (and/or use flared vents) to minimise port non-linearities (particularly audible "chuffing").
After that, it's just EQ and integration with the main PA.
Ideally, get the sub itself flat, and get good phase matching with the mains for at least an octave or so at the crossover point, as getting this wrong can lead to cancellation of output.
Then it's just voicing to suit the taste of whoever is mixing the gig. Some engineers do go for the "haystack" approach to LF where the entire sub signal is boosted 10-20dB above the mains, others will prefer a flatter system and just apply EQ on a per-channel basis if they want extra impact for things like a kick drum.
All of the above would be exactly the same for cardioid or standard setups.
There are a couple of different ways that the directional behaviour can be created which do have slightly different compromises - some do have more phase/timing issues than others, so choosing how to get directionality can be a part of the sound quality decision making.
In general, we don't need to try and get 100% cancellation behind the subs, which is why we don't need equal numbers/sizes of drivers for the rear parts - if using multiples of one box type, a common ratio is 2 forward : 1 back; or for single box solutions like d&b's V & Y subs there might be a smaller driver chosen for the rear part. The important part is that the rear source has the same frequency and phase response as the front part - if d&b's designers are good enough to achieve that for the bandpass rear sections of those subs, then more power to them.
HTH,
David.