Hi,
I have seen some answers before, but the aspect i am examining is different.
The design i am proposing is 2 mid ranges, tweeter and woofer. The design will be either :
I do not know the dispersion pattern of the drivers. It is an active system, so time delays can be modified easily.
In previous work in public address systems, column speaker were used to ensure that they could reach an audience moving backwards in direction, but did have less horizontal dispersion.
The seating position is designed to be 2.5m at least away from the baffle - so will horizontal alignment of the mid ranges be acceptable, or will there be detrimental constructive/destructive effects of the sound at this and greater distance ?
Any guidance thankfully received.
Regards,
Shadders.
I have seen some answers before, but the aspect i am examining is different.
The design i am proposing is 2 mid ranges, tweeter and woofer. The design will be either :
- MMTW vertically aligned, with the two mid ranges aligned above and below the ear level line on the baffle.
- MMTW horizontally aligned with the mid range speakers side by side, and their acoustic centres aligned at the ear level.
I do not know the dispersion pattern of the drivers. It is an active system, so time delays can be modified easily.
In previous work in public address systems, column speaker were used to ensure that they could reach an audience moving backwards in direction, but did have less horizontal dispersion.
The seating position is designed to be 2.5m at least away from the baffle - so will horizontal alignment of the mid ranges be acceptable, or will there be detrimental constructive/destructive effects of the sound at this and greater distance ?
Any guidance thankfully received.
Regards,
Shadders.
If you have multiple drivers, its all about where the lobes fall.
For that matter, its also about Center to Center spacing and frequency range of the drivers.
I think that the lobbing in a vertical alignment would tend to point to floor and ceiling. Side to side would produce horizontal lobbing.
I have heard both that work.
HTH
Doug
For that matter, its also about Center to Center spacing and frequency range of the drivers.
I think that the lobbing in a vertical alignment would tend to point to floor and ceiling. Side to side would produce horizontal lobbing.
I have heard both that work.
HTH
Doug
For home HiFi, I'd probably go TMMW vertical, or maybe MTMW vertical.
Generally, you want the tweeter at (or near) ear height, and you want the midrange drivers as close to the tweeter as possible so that you keep the off-axis response somewhere near smooth through the crossover region.
As a rule, it's better to have your lobing in the vertical plane, since there's usually a narrow set of listening angles, while horizontally might be all the way across a sofa which mandates wider coverage.
Chris
Generally, you want the tweeter at (or near) ear height, and you want the midrange drivers as close to the tweeter as possible so that you keep the off-axis response somewhere near smooth through the crossover region.
As a rule, it's better to have your lobing in the vertical plane, since there's usually a narrow set of listening angles, while horizontally might be all the way across a sofa which mandates wider coverage.
Chris
Hi DougL,
Thanks - thinking about it, horizontal lobing (horizontal alignment) will mean people slightly off axis will experience constructive/destructive interference, where for vertical alignment, no matter where you are left or right slightly off axis, then the interference should be the same.
This is all very theoretical, so vertical seems optimal for anyone listening at the same horizontal level.
Thanks and regards,
Shadders.
Hi Chris,
Thanks for the reply.
Since this is an active system, and i will be using time alignment, so the tweeter will have the relevant delay, this should compensate for the difference in ear/tweeter level, and hence the time delay will point the tweeter lobe downwards.
Does this seem acceptable ?.
To add - it will be a transmission line - so bottom to top will be MMTW - the enclosure for the mid ranges will form part of the transmission line labyrinth.
Thanks and regards,
Shadders.
In a sense, two drivers are like one oblong shaped driver. Lobing is therefore a somewhat imperfect representation of differing directivities. The longer dimension has the potential to offer narrowed response for, say, another octave (wherever that might be). With the drivers arranged vetically, that extra narrowing would occur in the vertical dimension. By and large, wider directivity is more tolerable in the horizontal dimension.
Hi,
Thanks. So the horizontal configuration would be a better option, from a person perspective.
Thanks and regards,
Shadders.
Horizontal reflections tend to be less of an issue, I don't like high frequency early ceiling reflections. I think this is shown in peoples choices to narrow vertical directivity with elliptical horns and vertical line arrays, assuming it's done for that reason. If there is lobing, and this remains to be demonstrated with the specifics of your driver configuration, then maybe vertical is a safer bet.
The situation is a little more complex than that. Lower frequency reflections might last in the room and contribute to the power therein, higher frequencies might bounce off a near wall to the listening position then dissipate.
The situation is a little more complex than that. Lower frequency reflections might last in the room and contribute to the power therein, higher frequencies might bounce off a near wall to the listening position then dissipate.
Why not build a proven TMW 3-way with the tweeter at 39" ear level? Well understood cabinet construction with diffraction control. Proven "desirable" polar pattern which most music is studio mixed to match. Clever crossovers which reduce phase and time-alignment artifacts. Solutions for baffle step and floor bounce. There are good reasons why, "everybody is doing it."
Do you already own 4 midrange drivers you want to use? If these midrange are larger then 5", then vertical MTM-W can still provide a wide lobe polar pattern if a robust low crossover frequency tweeter is selected. There are a few waveguide+dome tweeters which offer the lower crossover frequency plus pattern control required by l-o-n-g MTM alignments.
Do you already own 4 midrange drivers you want to use? If these midrange are larger then 5", then vertical MTM-W can still provide a wide lobe polar pattern if a robust low crossover frequency tweeter is selected. There are a few waveguide+dome tweeters which offer the lower crossover frequency plus pattern control required by l-o-n-g MTM alignments.
I'd put the area surrounding the drivers, if exists, which is often the baffle on which the speakers are attached to, into the equation, either
Hi Doug,
Apologies for the late reply.
I would have thought that the near field experience/response will have been worse than a far field response. At the far field the waves will be constructing/destructing, and essentially you will hear/experience a wave front.
At the mid range frequency use - which will be 250Hz to 3kHz, the 1/4 wavelength is less than 0.4metres.
Thanks and regards,
Shadders.
Hi LineSource,
As this is an active design, i can implement the relevant time alignments where necessary. With the correct time alignment - the polar patterns can be pointed as required - with the relevant assumed ear level.
I have not purchased the mid range drivers yet - will be using the SB Acoustics MW13P-8 which is a 5inch driver. I can see that an MTM alignment with the tweeter at ear level is the same as MMT if the middle of the mid range line is at ear level (time delay applied to tweeter).
If the Mid Range drivers are beside each other - then this part i am not sure about, if there is any anecdotal or empirical evidence indicating that this configuration is less optimal.
The woofer i am using is 150watts, the SB Acoustics are 40watts - so for the frequency range to be implemented for the mid range, i wanted ensure that SPL/Power levels correlated to the expected power density in the frequency range of operation.
Thanks and regards,
Shadders.
At 800 Hz, 1/4 wavelength is ~11 CM or 4.2 inches. Practical with 4 inch drivers.
At 3Khz, 1/4 wavelength is about an inch or 3 cm. They are going to be about a wavelength apart at these frequencies.
This is why the MTM designers look for the tweeter that plays as low as possible.
I personally would opt for one larger / more efficient midrange rather than 2 midranges.
Good Luck.
Doug
At 3Khz, 1/4 wavelength is about an inch or 3 cm. They are going to be about a wavelength apart at these frequencies.
This is why the MTM designers look for the tweeter that plays as low as possible.
I personally would opt for one larger / more efficient midrange rather than 2 midranges.
Good Luck.
Doug
Hi Doug,
Thanks for the reply.
Are you inferring that at the 3kHz crossover frequency that the associated wavelength has a negative effect - such as destructive interference between the tweeter and midrange outputs ?.
If tweeter has the relevant delay, such that at the distance of 3metres from the baffle to the listener, the delay of the tweeter ensures constructive interference at the crossover of 3kHz, that there is still an issue ?.
I am assuming that the acoustic centre of the midrange is behind the tweeter here - so this is taken into the calculation for the delay of the tweeter to the ear, to match the distance from both midranges to the ear.
The midranges i have examined, even the 6inch mid ranges have low power and low sensitivity, and those with reasonable power have a smaller linear excursion/coil travel.
Regards,
Shadders.
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