I would like to set up a quick and dirty open baffle for some new drivers, while I model and build a more permanent set of enclosures. I have a good deal of nicely finished birch ply sitting around. Plus, I just bought a MiniDSP and multichannel amp.
But I don't know how to calculate the size for the baffle.
The drivers are:
Seas 18w EX
ScanSpeak D2608 (formerly the Peerless HDS).
There are, of course, limitations to this arrangement. Bass, volume, etc. It will be in a small room, most likely as a desktop arrangement. I have a sub for the lower end duties.
Can someone suggest a baffle size?
But I don't know how to calculate the size for the baffle.
The drivers are:
Seas 18w EX
ScanSpeak D2608 (formerly the Peerless HDS).
There are, of course, limitations to this arrangement. Bass, volume, etc. It will be in a small room, most likely as a desktop arrangement. I have a sub for the lower end duties.
Can someone suggest a baffle size?
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I'm looking to emulate these with birch ply, not perspex. Maybe desk or stand mounted. [That's a w22, not w18]
This little freeware program can get you something close enough for OB, though ideally you want it to be same size as the finished cab's baffle, but since it isn't designed yet, probably best overall to make it whatever the max acceptable baffle size can be: Home of the Edge
GM
GM
Those both look like fantastic, simple solutions. And I might learn something in the process. Unfortunately, they all require a PC or DOS window, and I only have a mac available to me.
Schmalex: With such a "small" baffle, you will not be able to generate much bass, even if you sit in the nearfield. There are two things working against bass:
#1: open baffle is just like an infinitely sized box when it comes to the driver mechanical response, so you will get something that is on a first approximation like Fs and Qts.
#2: because the pathlength between the front and back of the driver is short, there is an "acoustic short circuit" meaning that low frequency sound waves from front and back meet and largely cancel (in the low bass). This is the "open baffle response" that the software can model and is only dependent on the baffle dimensions (to a first approximation).
In the picture you showed the baffle width is the smallest dimension, and I guesstimate that the width is on the order of 30cm or 12". The approximate open baffle response would be something like the attached plot, which I generated in the edge assuming a 30x45cm baffle.
The combination of #1 and #2 will give you a rough estimate of the woofer response. Don't expect to be able to use this 2-way below about 150-200Hz. You will need to add a small subwoofer.
-Charlie
Attachments
> I'm not sure what you mean here?
On a desk in front of you (baffle sitting on desktop)
the meaningfull dimension of the baffle is the width.
The other pertinent numbers (in determining LF rolloff)
are Qts and Fs of the driver.
On a desk in front of you (baffle sitting on desktop)
the meaningfull dimension of the baffle is the width.
The other pertinent numbers (in determining LF rolloff)
are Qts and Fs of the driver.
This is all very helpful. Thanks. That simulation is interesting. And the woofer curve looks pretty awful.
"the woofer curve looks pretty awful." - really, it is just the typical open baffle behaviour. And the beforementioned backwave cancellation cannot be beaten with eq! There is a reason for an enclosure! If you make a small-form ob, you need a separate woofer crossed at ~200-250Hz. Don't be too much afraid of integration, bass waves are kind of lurky in a room and you can take advantage of boundaries because bass box(es) are separate! a,6,5" or 8" woofer low-tuned should be ok, single or a pair.
this lends to design it as a 3 way, so the tweeter is asked to reproduce the range above 5 kHz, as usual .
I'd say smaller midrange is better, 4-5''.
I'd say smaller midrange is better, 4-5''.
You could always try. It will be a good excersise to see what you can achieve with the Mini-DSP. Desktop is the worst alternative, I think, free standing better as an OB-speaker should be kept away from surfaces be it walls, floor, ceiling or desk as far as possible to perform most balanced and with as flat frequency response as the unit is capable of. Bigger room is better. To optimize you should be able to measure response.
A 42" x 12" will be sufficient to bring the SEAS unit down to round 160-200 Hz relatively level. I figure driver center 34" up on baffle.
/Erling
A 42" x 12" will be sufficient to bring the SEAS unit down to round 160-200 Hz relatively level. I figure driver center 34" up on baffle.
/Erling
Juhazi, above, has a reason for enclosures on a desk, but the arguments are the ones I say in my post of OB near surfaces. His is wrong in saying that baffle fall off cannot be cured by EQ. Listening in front of the baffle the cannecellation effect can never be 100 %, because of sound wave path differences. So EQ applies, just look at for instance Siegfried Linkwitz' site for OB design models: Electro-acoustic models to understand.
/Erling
/Erling
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skorpion,
- I meant that a box (or infinite baffle) is needed, if one wants to get as low bass as the speaker can give. Wit a reasonable size of open baffle, low end will have the dipole-typical curve.
- by "you can't beat it" I meant that the response drops really fast at certain frequency in the low end. For example I have measured my 12" driver, it drops very fast below 100Hz without a baffle. Baffle's smallest dimension determines that and you can see that happening also at IEC baffle measurements in datasheets. This is different from dipole curve -6dB/oct. Edge program doesn't show this because it doesn't have driver's T/S info.
- I meant that a box (or infinite baffle) is needed, if one wants to get as low bass as the speaker can give. Wit a reasonable size of open baffle, low end will have the dipole-typical curve.
- by "you can't beat it" I meant that the response drops really fast at certain frequency in the low end. For example I have measured my 12" driver, it drops very fast below 100Hz without a baffle. Baffle's smallest dimension determines that and you can see that happening also at IEC baffle measurements in datasheets. This is different from dipole curve -6dB/oct. Edge program doesn't show this because it doesn't have driver's T/S info.
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Now this, as I read it, is for some excersise and perhaps to see potential of an OB speaker.
OB is not at all an unknown business. I would recommend anyone interested to get Martin.J.Kings Math-Cad spreadsheets to see what is going on: MathCad Computer Models : Upgraded Versions
Regarding baffle roll off. You are right below some point, depending on baffle width and speaker Fs the roll off is sharper. But usually you will experience the fall below 100 Hz as sharper because octave spacing is less there.
/Erling
OB is not at all an unknown business. I would recommend anyone interested to get Martin.J.Kings Math-Cad spreadsheets to see what is going on: MathCad Computer Models : Upgraded Versions
Regarding baffle roll off. You are right below some point, depending on baffle width and speaker Fs the roll off is sharper. But usually you will experience the fall below 100 Hz as sharper because octave spacing is less there.
/Erling
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Can't beat, divide it and conquer
Really good caps are cheap at nF and pF values!!
The first order filtering combined with baffle roll off reduces Doppler distortion and eases strain on smallish amps.
After trying this with an old pair of Tannoy Series 600's, I believe a properly integrated sub can only improve things by easing excursion of woofers, not straining a cabinet, or vibrating a baffle around.
After a few years of 54" x24" panels with 12" horns and 15" woofers, I definitely like the smallish satellite/ sub combo a little better.
After mucking about with some vintage seas 21tv's, I settled on a very small open frame 2 way, angling the 8"ers up to beam away their breakup frequencies, sparing lowpass filters in the signal path, these below an open back 4" full range, the 8" highpassed at 300 hz, the 4"ers highpassed at at 5000 hz, both 1st order at line level with a single cap for each amp channel.
Really good caps are cheap at nF and pF values!!
The first order filtering combined with baffle roll off reduces Doppler distortion and eases strain on smallish amps.
After trying this with an old pair of Tannoy Series 600's, I believe a properly integrated sub can only improve things by easing excursion of woofers, not straining a cabinet, or vibrating a baffle around.
After a few years of 54" x24" panels with 12" horns and 15" woofers, I definitely like the smallish satellite/ sub combo a little better.
Baffle Size/Shape for Eminence Beta 12 LTA
Hi, I plan to build a new 3 way open baffle someday when I can afford all the pieces. However, for now, I would just like to make some quick temporary baffles for a pair of Eminence Beta 12 LTA's that should arrive here about Monday. I have been playing with The Edge program. So far I have gotten the smoothest simulation by making a 450mm x 700mm Oval shape with the driver either placed at the very bottom or the very top of the tall oval. I am new to this. One question I have about The Edge is why whenever you start a new simulation the mic distance always goes automatically to 100m? If I change the number to the distance I will be listening from (say 2 meters) the response does not look so good.
If I am doing the above equation right, it means my baffle should be at least 15.7 inches wide?
I am not much of a computer person. I would have liked to try the other free program mentioned in this thread. I was able to download it, but perhaps my computer is not set up to actually use the program, I don't know.
I would be greatfull for any suggestions or help. The specs for the Eminence Beta 12 LTA's are as follows:
Sd in sq cm 532.4
Effective diameter 12.0 inches, 305mm
Qts. 0.51
Fs 45Hz
Listening distance 2 to 3 meters
Any suggestions much appreciated
Sincerely,
Benjamin
Hi, I plan to build a new 3 way open baffle someday when I can afford all the pieces. However, for now, I would just like to make some quick temporary baffles for a pair of Eminence Beta 12 LTA's that should arrive here about Monday. I have been playing with The Edge program. So far I have gotten the smoothest simulation by making a 450mm x 700mm Oval shape with the driver either placed at the very bottom or the very top of the tall oval. I am new to this. One question I have about The Edge is why whenever you start a new simulation the mic distance always goes automatically to 100m? If I change the number to the distance I will be listening from (say 2 meters) the response does not look so good.
If I am doing the above equation right, it means my baffle should be at least 15.7 inches wide?
I am not much of a computer person. I would have liked to try the other free program mentioned in this thread. I was able to download it, but perhaps my computer is not set up to actually use the program, I don't know.
I would be greatfull for any suggestions or help. The specs for the Eminence Beta 12 LTA's are as follows:
Sd in sq cm 532.4
Effective diameter 12.0 inches, 305mm
Qts. 0.51
Fs 45Hz
Listening distance 2 to 3 meters
Any suggestions much appreciated
Sincerely,
Benjamin