I forgot to mention:
Ever the busy-body, I wondered what differences I would see if I simply
slot loaded a woofer which was mounted flat on the baffle. By this I
mean a woofer that is already mounted conventionally on an open
baffle. So I made a plate to cover the woofer which had a cut-out so
as to constrict the radiating surface by a factor of three and I measured
the near field response with and without the plate.
Unlike the original article where there was about 9 dB near-field
difference, this yielded only 1 to 2 dB. This approach appears to impart
much less forward momentum because while the air comes out at a
higher velocity, its direction is scattered.
In the version where there is significant slot depth to focus momentum
toward the front, we see the larger difference.
I have begun purchasing for a prototype which will focus (pun intended)
on this effect to improve the frontal far-field sensitivity of the design.
Ever the busy-body, I wondered what differences I would see if I simply
slot loaded a woofer which was mounted flat on the baffle. By this I
mean a woofer that is already mounted conventionally on an open
baffle. So I made a plate to cover the woofer which had a cut-out so
as to constrict the radiating surface by a factor of three and I measured
the near field response with and without the plate.
Unlike the original article where there was about 9 dB near-field
difference, this yielded only 1 to 2 dB. This approach appears to impart
much less forward momentum because while the air comes out at a
higher velocity, its direction is scattered.
In the version where there is significant slot depth to focus momentum
toward the front, we see the larger difference.
I have begun purchasing for a prototype which will focus (pun intended)
on this effect to improve the frontal far-field sensitivity of the design.
Hi,
How do they compare at a distance of, say, 3~4 meters as ordinary listening position?
My own (limited) experiences with slot on flat baffle reveal the 'compression ratios' do have some effects. The fs drops as the slot gets smaller, and the bass sound tends to be heavy-footed. It's not slow, but a sensible tendency that the energy seems to be squeezed to the low end. A slot area of 40% Sd or so give me a best compromise in my case -- punchier than plain OB but not too heavy.
And, when 'far field sensitivty' is called for, I guess a real horn is inevitable
Good idea; I haden't thought about plate amps having the phase and low-pass adjustment. I have some old JBL/Urei and Tascam amps I was gonna use.
Maybe it would be cheaper in time and money to use those plates, than buy/build a low-level-signal circuit. I'll have to balance what I envision of the quality of the end result ;-)
I just ordered some components for a switch between solid-state and vacuum amps: a 12P3T rotary switch with silver-plated copper terminals and 6 pairs of gold-plated brass banana terminals.
This will switch the main speakers between amps and also switch the smaller side-surround speakers from surround to mains on the solid-state surround receiver, so that the solid-state receiver can output 3.1 channels while the vacuum amp is working in stereo.
Oh no, I just thought of another option. My mixer has two main outputs; one I was intending to use for subs. I guess I can use another switch cascaded for that.
uhm... there also looks to be a L/R Sub Speaker power output switch on this Marantz SR-8002 receiver, in the Multi section.
That gives me a few options during listening/production
Maybe it would be cheaper in time and money to use those plates, than buy/build a low-level-signal circuit. I'll have to balance what I envision of the quality of the end result ;-)
I just ordered some components for a switch between solid-state and vacuum amps: a 12P3T rotary switch with silver-plated copper terminals and 6 pairs of gold-plated brass banana terminals.
This will switch the main speakers between amps and also switch the smaller side-surround speakers from surround to mains on the solid-state surround receiver, so that the solid-state receiver can output 3.1 channels while the vacuum amp is working in stereo.
Oh no, I just thought of another option. My mixer has two main outputs; one I was intending to use for subs. I guess I can use another switch cascaded for that.
uhm... there also looks to be a L/R Sub Speaker power output switch on this Marantz SR-8002 receiver, in the Multi section.
That gives me a few options during listening/production
Anyone remember that thread? http://www.diyaudio.com/forums/multi-way/148303-emerald-physics.html
Ever since I made that last post there it hounds my conscience. Although I am semi right I am semi wrong too. And since those Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories and the present thread I think about this phenomenon.
Here is my post that keeps me thinking: http://www.diyaudio.com/forums/multi-way/148303-emerald-physics-5.html#post2407563
Interestingly, it seems it should work with boxed speakers too. Maybe only for lowering the system resonance. But that would not be a small improvement for a sealed system for instance.
EDIT: Hm, I went through it again, although the analysis is generally true, the conclusion about decoupling might be doubtful due to lack of experience with the scale of the phenomenon. Although conclusions might be true, they might simply not apply with the given areas and cone excursions. Also, I didn't take into consideration that the accelerated air has more energy and the proportion of that energy to the one otherwise transmitted to the medium by a bare driver membrane.
Ever since I made that last post there it hounds my conscience. Although I am semi right I am semi wrong too. And since those Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories and the present thread I think about this phenomenon.
Here is my post that keeps me thinking: http://www.diyaudio.com/forums/multi-way/148303-emerald-physics-5.html#post2407563
Interestingly, it seems it should work with boxed speakers too. Maybe only for lowering the system resonance. But that would not be a small improvement for a sealed system for instance.
EDIT: Hm, I went through it again, although the analysis is generally true, the conclusion about decoupling might be doubtful due to lack of experience with the scale of the phenomenon. Although conclusions might be true, they might simply not apply with the given areas and cone excursions. Also, I didn't take into consideration that the accelerated air has more energy and the proportion of that energy to the one otherwise transmitted to the medium by a bare driver membrane.
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No, I made a plate to cover the woofer, and I put an opening in it 1/3
the size of the woofer surface.
No, I made a plate to cover the woofer, and I put an opening in it 1/3
the size of the woofer surface.
photos?
Maybe just a nice cheap plate amplifier for the bottom. They come with
most of the controls you want, and they are likely good enough for the
bottom end.
Ok, I found a pair of new 100W Velodyne plate amps with 40-120Hz crossover and a 0/180 phase switch. 100 watts is plenty for this small room and 10" driver.
Working out the details of construction, what I have now is a 45 degree outward bevel on the main baffle and to allow adjustment of the distance between two vertical rounded edges to form the slot, for fine tuning. This could be done by making screw slots in the adjustable slot-baffle halves and install carriage bolts with wing nuts on the outside.
I'm beginning to learn about acoustic design; I have a technical degree in electronics, so I'm familiar with some of the basics. When we see "Slot Loaded" I'm assuming that this means the slot loads the driver with an acoustic impedance. From this I imagine that this can also be seen as a technique for matching the impedance of the driver with the impedance of the room, which can vary greatly between each room. If this is true then it supports my approach of being able to vary the size of the slot for fine-tuning.
And Tyimo, what is a SLOB? Not that I know how to do that calculation ;-)
Oh, sorry, I spelled it out and got slot loaded open baffle...
I'm beginning to learn about acoustic design; I have a technical degree in electronics, so I'm familiar with some of the basics. When we see "Slot Loaded" I'm assuming that this means the slot loads the driver with an acoustic impedance. From this I imagine that this can also be seen as a technique for matching the impedance of the driver with the impedance of the room, which can vary greatly between each room. If this is true then it supports my approach of being able to vary the size of the slot for fine-tuning.
And Tyimo, what is a SLOB? Not that I know how to do that calculation ;-)
Oh, sorry, I spelled it out and got slot loaded open baffle...
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See how it looks in my case:
http://www.diyaudio.com/forums/full...-b200-eminence-beta-15-ob-14.html#post2755119
Baffle dimensions are set/ limited by my wife. I can play with other variables as much as I like, and the slot loading appeared to be a good one.
Before mounting the screws, I tried to make it wider/ narrower and just listened. With the slot, they do sound better
http://www.diyaudio.com/forums/full...-b200-eminence-beta-15-ob-14.html#post2755119
Baffle dimensions are set/ limited by my wife. I can play with other variables as much as I like, and the slot loading appeared to be a good one.
Before mounting the screws, I tried to make it wider/ narrower and just listened. With the slot, they do sound better
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