also birch ply comes in different grades.
but i dont think ik makes much difference.
the fact that its 13 ply ,and it feels dense and heavy,is good enough.
it should be about 13kg/m2 ,if it comes close it wil do no probs.
btw ive bild a test box of the symetric design.
have not yet tested it (no time)
i wil do some testing next saturday.
we put a signal on it for a short time,and it go's low(maybe to low)
but i dont think ik makes much difference.
the fact that its 13 ply ,and it feels dense and heavy,is good enough.
it should be about 13kg/m2 ,if it comes close it wil do no probs.
btw ive bild a test box of the symetric design.
have not yet tested it (no time)
i wil do some testing next saturday.
we put a signal on it for a short time,and it go's low(maybe to low)
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Hi Crescendo I never got around to placing all the panels in this design. What You have picked up there is just a simple error on my part.
Probably the top board is best full depth front to back.
Have not got much time today to sort anything out- Off out tonight to run My PA for a benefit gig. 2 Groups & a DJ to sort out.
Hi & yes, symmetry is nice. What i'm wondering though is, the two equal path lengths don't make the path longer, just wider/higher overall. So as the path length is the same, the available volume means a higher fb/f3 etc than could otherwise be achieved.
So what do feel are the benefits with this Sym design ?
TIA
Hi Zero D,
The reasons are still the same than half a century ago, when a similar layout was already used for front loaded horns. In simple words, this layout can play louder (especially at the low end) with the same driver since it provides an optimised load over the whole cone area compared to our 'traditional' layouts. In other words it optimises the cone pressure over the entire surface of the cone, not just on one side, but on both sides of the cone.
In the symmetric layout, the cone side that is facing the throat, will need at least a cone make up (you cant see that yet in Epa's unfinished symmetric layout picture). A simple column that crosses the total path at S2 works good. In a 'traditional' layout, one side of the cone (facing the back of the horn) has much lower pressure than the other side of the cone (you can see that in this model from Xoc1). In the symmetric layout the lowest pressure is in the centre of the cone, which is where you want it.
Since the symmetric layout has two paths, at the end the come together by facing each, one side of the back of the cone. Because of the position of the cone, that is turned 90 degrees compared to ‘traditional’ TH layouts, the horn mouth also 'sees' all sides of back of the cone. In other words the distance from the cone to the mouth is almost everywhere the same.
All in all, this symmetric layout is more close to our ideal models of HornResp. The central position of the driver also helps in using the total front as one big horn mouth instead of a reflecting area. This helps in optimising the acoustic coupling when used in small stacks.
The reasons are still the same than half a century ago, when a similar layout was already used for front loaded horns. In simple words, this layout can play louder (especially at the low end) with the same driver since it provides an optimised load over the whole cone area compared to our 'traditional' layouts. In other words it optimises the cone pressure over the entire surface of the cone, not just on one side, but on both sides of the cone.
In the symmetric layout, the cone side that is facing the throat, will need at least a cone make up (you cant see that yet in Epa's unfinished symmetric layout picture). A simple column that crosses the total path at S2 works good. In a 'traditional' layout, one side of the cone (facing the back of the horn) has much lower pressure than the other side of the cone (you can see that in this model from Xoc1). In the symmetric layout the lowest pressure is in the centre of the cone, which is where you want it.
Since the symmetric layout has two paths, at the end the come together by facing each, one side of the back of the cone. Because of the position of the cone, that is turned 90 degrees compared to ‘traditional’ TH layouts, the horn mouth also 'sees' all sides of back of the cone. In other words the distance from the cone to the mouth is almost everywhere the same.
All in all, this symmetric layout is more close to our ideal models of HornResp. The central position of the driver also helps in using the total front as one big horn mouth instead of a reflecting area. This helps in optimising the acoustic coupling when used in small stacks.
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@ Djim
Hi & thanks for the info
Yes i've been aware of them & similar for some time, & always wondered why they used up the available volume that way, instead of achieving a much lower f3/fb. Well now i do thanks to you, better late than never
How much louder, 1 - 2 dB or even more ?
A definate plus
Interesting that in Xoc1's screenie the Max compression point is @ the first bend, rather than nearer the closed end !
So all in all, lots of Very good reasons for choosing Sym It still seems however, that to achieve a lower f3/fb, we would need a bigger box than a non Sym design of equal volume, to get the desired path length.
Hi & thanks for the info
Yes i've been aware of them & similar for some time, & always wondered why they used up the available volume that way, instead of achieving a much lower f3/fb. Well now i do thanks to you, better late than never
How much louder, 1 - 2 dB or even more ?
A definate plus
Interesting that in Xoc1's screenie the Max compression point is @ the first bend, rather than nearer the closed end !
So all in all, lots of Very good reasons for choosing Sym
It still seems however, that to achieve a lower f3/fb, we would need a bigger box than a non Sym design of equal volume, to get the desired path length.Hi Zero D,
I can’t give exact figures since it really depends on several factors like, driver quality in relation to dynamic compression, the precision of the correction of S2 among other things.
That the Fb is lower in 'traditional' lay outs of the same volume is a misunderstanding, I think. You can use a chamber in front of the driver of a symmetric layout that compensates the absence of the distance between S1 and S2. By adding such chamber the total volume, efficiency and Fb are all equal between the traditional and symmetric lay outs. Nevertheless, the symmetric lay out still has the advantage of better cone/excursion control because of the reasons I mentioned in my earlier post.
This advantage can be measured/heard at the lowest dynamic power compression points, below the second excursion peak to be more precise. In case you design the symmetric lay out with a maximum horn mouth (mouth area equal to the total front area of the cabinet) it will no longer be the same design and in that case the efficiency rises at cost of a higher Fb. To get the same Fb from such concept it needs more volume of course.
I can’t give exact figures since it really depends on several factors like, driver quality in relation to dynamic compression, the precision of the correction of S2 among other things.
That the Fb is lower in 'traditional' lay outs of the same volume is a misunderstanding, I think. You can use a chamber in front of the driver of a symmetric layout that compensates the absence of the distance between S1 and S2. By adding such chamber the total volume, efficiency and Fb are all equal between the traditional and symmetric lay outs. Nevertheless, the symmetric lay out still has the advantage of better cone/excursion control because of the reasons I mentioned in my earlier post.
This advantage can be measured/heard at the lowest dynamic power compression points, below the second excursion peak to be more precise. In case you design the symmetric lay out with a maximum horn mouth (mouth area equal to the total front area of the cabinet) it will no longer be the same design and in that case the efficiency rises at cost of a higher Fb. To get the same Fb from such concept it needs more volume of course.
"Have you ever experienced ratteling or poking holes in plywood?"
Yes to both.
The AC grade has veneer that is paper thin over knots in the cores, a slight bump can cave-in the veneer.
I tried some ply that had 13 cores that were D cores, it buzzed.
These speakers were all for PA applications.
Yes to both.
The AC grade has veneer that is paper thin over knots in the cores, a slight bump can cave-in the veneer.
I tried some ply that had 13 cores that were D cores, it buzzed.
These speakers were all for PA applications.
One of the main reasons I want extended bottom end (below 40Hz). Djim scanned a whole mix of mine and found it was centered around 38Hz, but this is the lowww end energy I have been trying to describe.
The bassline takes a walk to the left and I took 3 'captures' to show this; from blue to red to green. The signal was fed directly from my right ch. mixer out to my interface connected to my laptop via firewire:
Note: don't mind the 'x' on the 'Mixer Right' on the command strip. I was comparing readings before I did a screen capture
The bassline takes a walk to the left and I took 3 'captures' to show this; from blue to red to green. The signal was fed directly from my right ch. mixer out to my interface connected to my laptop via firewire:
Note: don't mind the 'x' on the 'Mixer Right' on the command strip. I was comparing readings before I did a screen capture
Attachments
Looks like the fundamentals around 25 Hz are down about 10 dB from the first harmonics, Josh Ricci's Othhorn could reproduce that faithfully.
Most of the other TH PA subs you seem to be considering won't do much at all for the 25 Hz fundamental bass notes.
Art
Attachments
Hi Art,
"...the fundamentals around 25 Hz are down about 10 dB from the first harmonics, Josh Ricci's Othhorn could reproduce that faithfully."
The Othhorn is down about 10dB @ 25Hz, so even this very fine TH would require a 10dB boost to reproduce 25Hz content accurately. It may well have enough reserve in the excursion to do that as long as the incoming signal in that range is 10dB down from the rest of the music, but that'll take some investigating.
It may well take something like the Gjallerhorn (which will get close to 20Hz).
Regards,
"...the fundamentals around 25 Hz are down about 10 dB from the first harmonics, Josh Ricci's Othhorn could reproduce that faithfully."
The Othhorn is down about 10dB @ 25Hz, so even this very fine TH would require a 10dB boost to reproduce 25Hz content accurately. It may well have enough reserve in the excursion to do that as long as the incoming signal in that range is 10dB down from the rest of the music, but that'll take some investigating.
It may well take something like the Gjallerhorn (which will get close to 20Hz).
Regards,
Hi Oliver,
I don’t agree from a PA point of view. I know you like to design flat, but going down flat to 25Hz lowers the overall efficiency. That means raising the average power by 3dB in the area where you need most. It will raise the all power compression figures which you want to prevent in PA.
-10dB is still audible and with the crest factor available, you can partly make it up. Therefore it wouldn’t surprise me if Josh deliberately chose the 29Hz point as -3dB point in order to keep the best balance for PA between volume, efficiency, power compression and still be able the reach the lowest but rare notes.
I don’t agree from a PA point of view. I know you like to design flat, but going down flat to 25Hz lowers the overall efficiency. That means raising the average power by 3dB in the area where you need most. It will raise the all power compression figures which you want to prevent in PA.
-10dB is still audible and with the crest factor available, you can partly make it up. Therefore it wouldn’t surprise me if Josh deliberately chose the 29Hz point as -3dB point in order to keep the best balance for PA between volume, efficiency, power compression and still be able the reach the lowest but rare notes.
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