I am starting this thread, because soon I will move to a new house and set up my horn system again, after a year of living in a rented house with no space to install them. I am fortunate that it will be a dedicated room to enjoy my favorite music in the best way possible, within certain constraints, of course. The properties of the room are not very ideal, as it is a rectangular basement room, with solid concrete walls, ceiling and floor. There is a small room in the back and one access door about halfway. The dimensions are 2,4m ( 8ft) high by 4m (13.3ft) by 10,45m (34.8ft) long. Let's call it a pipe drawer...
The speaker setup is as follows: eight bandpass small subwoofers with single 8" woofers, two lower midbass exponential front horns, two mid-high Le'Cleach horns with BMS 4592ND.
In my previous home, I succeeded to have achieved a proper overall sound, so I know these set of speakers work good together. That room was treated with absorption, diffusion and bass traps at their optimum places, as far as a irregular living room can be tuned.
The new room poses one big challenge among some others: the length of 10,45m (34,8ft) in relation to the other dimensions. So I started to model the room acoustics in REW, trying numerous subwoofer/midbass placements. The multiple subs give me the possibility to use various proven concepts for multisub low frequency applications. While I did not model all variants, none of those concepts are really satisfying in this particular room, but one does. In the end, a Double Bass Array will be the concept of choice to build the system from the ground up.
The advantages from the simulation are clear:
Disadvantages are also clear, but from a hardware point:
* Need for a DSP and multiple amps, in my case I will need four DSP channels and associated amps. I already own a MiniDSP 8x10HD but the amount of delay is insufficient for this room and I only have two channels left for sub bass. The solution (hurts financially) is to aquire a T.Rack (Thomann) DSP amp, a suitable one would be a 4x250w class D-amp plus DSP build in. This means an extra ADDA conversion after the MiniDSP, as this amp has no digital input, but it is cost effective and for low frequencies, I do not think an extra conversion step hurts too much. With four channels of DSP, one can fine tune the response better than with two channels.
* The back subwoofers do not contribute to the sound as they cancel the sound as soon as the plane wave reaches the back wall, so there are only 4 smallish subwoofers that provides the sound pressure a.k.a. lower efficiency. As I do not listen to ear splitting sound levels, I can get away with this disadvantage. It will take about 100 watts to reach 107dB according to the simulation. The mid-high CD can reach that level with 1W input as the difference in efficiency is about 20dB. No problems here, as I use a flea power 1W tube amp for this horn.
Conclusion up to now: a DBA is the best solution in my opinion when dealing with long, narrow rooms -albeit against considerable costs, but also with savings on the bass trap side.
The picture below is an overview of my simulation with both subwoofers and midbass together, I chose to use PSY smoothing in the left graph, to have a simplified view of what is to be expected. The simulation is without any EQ. EQ'ing will of course be preferable, and possible. I applied a modest amount of acoustic absorpion to the room, but fortunately it does not need a lot of absorption, ergo too much absorption will screw it up. I will continue this thread when I am actually moving in and starting to install the system and make measurements of the process.
The speaker setup is as follows: eight bandpass small subwoofers with single 8" woofers, two lower midbass exponential front horns, two mid-high Le'Cleach horns with BMS 4592ND.
In my previous home, I succeeded to have achieved a proper overall sound, so I know these set of speakers work good together. That room was treated with absorption, diffusion and bass traps at their optimum places, as far as a irregular living room can be tuned.
The new room poses one big challenge among some others: the length of 10,45m (34,8ft) in relation to the other dimensions. So I started to model the room acoustics in REW, trying numerous subwoofer/midbass placements. The multiple subs give me the possibility to use various proven concepts for multisub low frequency applications. While I did not model all variants, none of those concepts are really satisfying in this particular room, but one does. In the end, a Double Bass Array will be the concept of choice to build the system from the ground up.
The advantages from the simulation are clear:
- Linear frequency range from 30Hz to 300Hz with exellent Group Delay and phase behavior.
- No resonant behavior of certain frequencies in the bass region and good extension into the lowest frequencies.
- More even bass sound across the room, as a DBA generates a plane wave without back wall or side wall reflections.
- Short decay of low frequencies without using extensive bass trapping, i.e. no smearing effects in the bass.
- No need to fill the room with randomly placed subwoofers (a la Geddes), with the associated cable spagetti.
- The subs do not take much space and can be placed against the back wall without much cabling challenges.
Disadvantages are also clear, but from a hardware point:
* Need for a DSP and multiple amps, in my case I will need four DSP channels and associated amps. I already own a MiniDSP 8x10HD but the amount of delay is insufficient for this room and I only have two channels left for sub bass. The solution (hurts financially) is to aquire a T.Rack (Thomann) DSP amp, a suitable one would be a 4x250w class D-amp plus DSP build in. This means an extra ADDA conversion after the MiniDSP, as this amp has no digital input, but it is cost effective and for low frequencies, I do not think an extra conversion step hurts too much. With four channels of DSP, one can fine tune the response better than with two channels.
* The back subwoofers do not contribute to the sound as they cancel the sound as soon as the plane wave reaches the back wall, so there are only 4 smallish subwoofers that provides the sound pressure a.k.a. lower efficiency. As I do not listen to ear splitting sound levels, I can get away with this disadvantage. It will take about 100 watts to reach 107dB according to the simulation. The mid-high CD can reach that level with 1W input as the difference in efficiency is about 20dB. No problems here, as I use a flea power 1W tube amp for this horn.
Conclusion up to now: a DBA is the best solution in my opinion when dealing with long, narrow rooms -albeit against considerable costs, but also with savings on the bass trap side.
The picture below is an overview of my simulation with both subwoofers and midbass together, I chose to use PSY smoothing in the left graph, to have a simplified view of what is to be expected. The simulation is without any EQ. EQ'ing will of course be preferable, and possible. I applied a modest amount of acoustic absorpion to the room, but fortunately it does not need a lot of absorption, ergo too much absorption will screw it up. I will continue this thread when I am actually moving in and starting to install the system and make measurements of the process.
Out of curiosity, I modelled a Single Bass Array with all the eight subs against the front wall and maximum damping on the back wall, to see if it is better or worse than a Double Bass Array. I also simulated a quasi DBA with all subwoofers on the front, but the right four subwoofers inverted and delayed with the same amount of a regular DBA and without any damping of the backwall.
I am pretty surprised by the results. Below is a graph showing to the left an SPL graph overview: 1) DBA plus midbass (in red) versus: 2) Quasi DBA with and without midbass (purple) versus: 3) SBA with full damping (light and darker orange). These have been psy smoothed. Levels are as modelled.
To the right, the plain results of the modelled SBA plus midbass, without EQ.
(Note: forget the straight grey line at 70dB, the upper one is the min. phase in the above graph)
Conclusions:
The SBA with full damping is theoretically superior over a DBA in this simulation and with these room dimensions. The output of the combined subwoofers are 6dB more (more headroom or less distortion!), the SPL graph is just as smooth (the residual 3dB bump at 30Hz may be even desirable) and group delay, impulse response and waterfall show better performance than with a DBA. Also the integration with the midbass (and possibly the rest of the speakers) is much better. So to my surprise and pleasure, it will be better to opt for a SBA in this room, soundwise. I'll have to change the topic title...
I do have the space to build a proper wall-to-wall bass trap on the back wall of plm 4ft deep, with a two feet deep stack of Rockwool ($250-300). That will be sufficient, together with some EQ. This form of damping also consumes no electricity. And to start with, I have a bunch of pretty effective corner bass traps that I can use initially.
I can keep using my older MiniDSP -with insufficient delay for a DBA- and the stereo sub amp I have at hand, without buying additional equipment (yay!). Less cable spagetti. One does not even have to use a DSP. An analog crossover plus analog EQ to a mono amp is the minimum requirement, a DSP is handy to fine tune but not strictly neccesary. So from a butget perspective also a better choice.
The quasi DBA with eight subs in the front seem to work as a real DBA -at least on the listening position in the middle of the room- with no back wall subs neccesary, but a time delay is mandatory. If my simulation is correct, the Quasi DBA seems to have the same efficiency as a regular DBA, that is surprising. It may be a solution for those with no space on the back wall. Usual requirements for SBA/DBA still need to be fullfilled.
To be continued..
I am pretty surprised by the results. Below is a graph showing to the left an SPL graph overview: 1) DBA plus midbass (in red) versus: 2) Quasi DBA with and without midbass (purple) versus: 3) SBA with full damping (light and darker orange). These have been psy smoothed. Levels are as modelled.
To the right, the plain results of the modelled SBA plus midbass, without EQ.
(Note: forget the straight grey line at 70dB, the upper one is the min. phase in the above graph)
Conclusions:
The SBA with full damping is theoretically superior over a DBA in this simulation and with these room dimensions. The output of the combined subwoofers are 6dB more (more headroom or less distortion!), the SPL graph is just as smooth (the residual 3dB bump at 30Hz may be even desirable) and group delay, impulse response and waterfall show better performance than with a DBA. Also the integration with the midbass (and possibly the rest of the speakers) is much better. So to my surprise and pleasure, it will be better to opt for a SBA in this room, soundwise. I'll have to change the topic title...
I do have the space to build a proper wall-to-wall bass trap on the back wall of plm 4ft deep, with a two feet deep stack of Rockwool ($250-300). That will be sufficient, together with some EQ. This form of damping also consumes no electricity. And to start with, I have a bunch of pretty effective corner bass traps that I can use initially.
I can keep using my older MiniDSP -with insufficient delay for a DBA- and the stereo sub amp I have at hand, without buying additional equipment (yay!). Less cable spagetti. One does not even have to use a DSP. An analog crossover plus analog EQ to a mono amp is the minimum requirement, a DSP is handy to fine tune but not strictly neccesary. So from a butget perspective also a better choice.
The quasi DBA with eight subs in the front seem to work as a real DBA -at least on the listening position in the middle of the room- with no back wall subs neccesary, but a time delay is mandatory. If my simulation is correct, the Quasi DBA seems to have the same efficiency as a regular DBA, that is surprising. It may be a solution for those with no space on the back wall. Usual requirements for SBA/DBA still need to be fullfilled.
To be continued..
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