Frequently answered questions
How does the two chambered bandpass design change the response at the rear (phase/level etc.) of the loudspeaker to achieve the cardioid behaviour?
The task of the rear loudspeaker in a cardioid arrangement is to wait for the program from the front loudspeaker to be diffracted around the cabinet, and then at the right time cancel it. Compared to the processing in an active, bi-amped solution this can also be achieved by the following:
a) The correct physical offset between front and rear loudspeaker, which is no different.
b) The rear loudspeaker's frequency response must match that which is diffracted around the cabinet from the front loudspeaker using additional a bandpass to provide low pass filtering.
c) A certain amount of frequency independent delay must be present in the rear loudspeaker's signal, hence the low bandpass resonator has to be tuned in a defined relation to the front facing bass-reflex chamber.
d) A certain amount of frequency dependent delay must be present in the rear loudspeaker's signal; this is also achieved with an additional low pass of the bandpass system.
e) Once points a) to d) are provided correctly, the polarity of the rear loudspeaker's signal must be set to provide inverted acoustic output relative to that of the front loudspeaker which is easily done in the internal wiring.
Why is the rear grill shaped as it is?
There are two different exits for the rear chambers.
How far off the wall can it be positioned?
It can be placed the wheel distance from a wall as this does not adversely affect the performance at the front. The main thing possibly influenced is the cardioid performance which happens behind and to the back sides of the speaker. This is valid for the B4-SUB, J-SUB, J-INFRA and CSA setups.
What is the recommended minimum distance to place between two subwoofers?
As recommended with other cardioid subwoofers a minimum of half the cabinet width or 60cm / 2 feet, also displayed at each cabinets serial number label.
Why is the design of the handle different to all your other subwoofers?
The positioning of the different chambers within the cabinet does not permit the usual handles and position.
Can a B2/Q-SUB/J-SUB/J-INFRA be used in conjunction with the B4 subwoofer, and can a B2 be placed next to a J-SUB?
We do not recommend mixing omni directional and cardioid subwoofers.
How many B4-SUBs give an equivalent SPL output to a three Q-SUBs in CSA?
Three B4s have the same average SPL compared to three Q-SUB/CSAs. The real benefit of the B4 comes in smaller systems or distributed sub arrays.
In the sound reinforcement world what this really means is that the B4-SUB is currently the smallest and most economical solution to provide cardioid low frequency performance from a single cabinet position driven by using only one amplifier channel. It is also possible to create single bass arrays for medium SPL using eight B4-SUBs amplified by two D12 / D6 amplifiers. However, three B4-SUBs are required to match the performance of three Q-SUBs in a CSA setup when used for a single sub position, since this also requires two amplifier channels it is not necessarily the most cost effective solution. From a total performance point of view, above two B4-SUBs in one speaker position, the next size of useful and economic setup exhibiting cardioid behaviour requires three 18" speakers and two amplifier channels using a 2-way active approach, or in fact three Q-SUBs in CSA or a J-SUB.
In other words if you do not require the output of three 18" drivers at a single subwoofer position but want the benefits that a cardioid setup offers.
It is documented that the B4 subwoofer is compatible with the E and T-Series, what about the Q and Ci-Series?
The behaviour is the same as any other combination of d&b top and sub cabinets in active mode and released since 2003. They are basically compatible with only a slight difference in the low pass.
Can B4-SUBs be stacked with T-Series and Q-Series cabinets?
By using the T Base plate you can safely stack up to six T10 loudspeakers onto a B4-SUB, Q-SUB or E15X-SUB.
Is the B4 integrated into ArrayCalc?
The B4 will be integrated into ArrayCalc Version 6. In the meantime Q-SUB/CSA can be used to predict the horizontal behaviour of a B4-SUB array.
Where does that "breath" sound from the rear port at high levels come from?
There always has been vent noise from at all subwoofers and it is very hard to avoid it with reasonable effort. In contrast to standard subwoofers you can now perceive vent noise at the back of a cardioid subwoofer as these are no longer masked there.
Will there be a B4-SUB configuration for the E-PAC?
No, we will not supply a B4-SUB configuration for the E-PAC.
Is it possible to fly the B4-SUB?
The B4-SUB is exclusively designed for ground stacked use.
