John
At resonance the woofer cone is basically not moving, so there is no sound radiation from the side of the cone without the Helmholtz resonator. Thus there is only one side radiating and the distance from the front to the back is irrelavent - its a monopole no matter what this distance is.
And think about it this way. I make a subwoofer with a 15" direct radiating driver and a ported rear enclosure tuned to 50 Hz. Now, I put the port on the back and face the driver away from me. How is this any different than what is being done here?
Just like any ported sub it has its assets and its problems, but I'll stick with my claim that at these frequencies the source type makes very little difference. It's all about the number of sources, location and setup. Nothing in the design being discussed here changes any of that. It's the fact that it is LP'd below 100 Hz that makes this true. It's just a ported sub, thats all.
At resonance the woofer cone is basically not moving, so there is no sound radiation from the side of the cone without the Helmholtz resonator. Thus there is only one side radiating and the distance from the front to the back is irrelavent - its a monopole no matter what this distance is.
And think about it this way. I make a subwoofer with a 15" direct radiating driver and a ported rear enclosure tuned to 50 Hz. Now, I put the port on the back and face the driver away from me. How is this any different than what is being done here?
Just like any ported sub it has its assets and its problems, but I'll stick with my claim that at these frequencies the source type makes very little difference. It's all about the number of sources, location and setup. Nothing in the design being discussed here changes any of that. It's the fact that it is LP'd below 100 Hz that makes this true. It's just a ported sub, thats all.
Any further development on this? I am thinking of trying this with a single Alpha 15a, the Beta cx12 and the B&C DE10.
I cant seem to get any decent box software to simulate the 6 inch diam 1/2 in port, and varying volumes as suggested. Based on the overall baffle thickness, I imagine the front volume to be about 4.8L. This would be an approximate 13.75x2.0 cutout in front of the Alpha. Sound about right?
Patrick have you pursued this?
andy
I cant seem to get any decent box software to simulate the 6 inch diam 1/2 in port, and varying volumes as suggested. Based on the overall baffle thickness, I imagine the front volume to be about 4.8L. This would be an approximate 13.75x2.0 cutout in front of the Alpha. Sound about right?
Patrick have you pursued this?
andy
Emerald CS1, Dipole or Linear Quadrupole?
Not 1.3 in their own web site now. The (older) CS1 seemed only appear in some audio shows, I'm not sure ...
emerald CS1 - Google ·j´M
It has 2 open baffles for bass - front and rear. Would it be "Linear Quadrupole" instead of dipole?
Interesting animations here, you may see how linear quadrupole works:
Radiation from monopoles, dipoles, quadrupoles
(scroll down and see the last one)
Anyone tried this?
Not 1.3 in their own web site now. The (older) CS1 seemed only appear in some audio shows, I'm not sure ...
emerald CS1 - Google ·j´M
It has 2 open baffles for bass - front and rear. Would it be "Linear Quadrupole" instead of dipole?
Interesting animations here, you may see how linear quadrupole works:
Radiation from monopoles, dipoles, quadrupoles
(scroll down and see the last one)
Anyone tried this?
Very interesting speakers! Any clue what the make of the 18 inch woofers is? Because if they are Goldwoods it would be scandalous!
The 15 inch Alpha powered version is scandalous too! The whole system together with the crossover utilizes parts worth 700-750$ - mention that: on retail prices! And this sells for nearly 5.000$
Not that the profit rate is uncommon for a market such as the hi-fi or hi-end hi-fi... it's not uncommon for any market!
But double 15 inchers on an OB with DSP is something that we very well know! Half the forum has twin or single Eminence 15 inch OB's and the other half have 18 inch Goldwoods on H-frames!
With the cone area of twin 15's and EQ it's normal that 15hz @ -3 are achieved. - No one mentions at what power input and until what power input though!
The "18 Goldwoods run out of excursion with about 7 to 17 watts with sine wave at 20 hz... and they are rated to be 18hz@-6 db in the H-frame...
15 hz@ -3 db for the "15's would mean that they are EQ-r*ped and I doubt if they would last more than 15-20 watts before reaching max excursion!
Note as well that those ports are not that restrictive at all and if you bare in mind that the air compression is linear almost until liquid state and you'll know why those speakers look like that!
They are just selling DIY projects masked as highly sophisticated commercial products!
And they deserve we to replicate their design completely and publish the plans together with the DSP settings for free download!
As I see it the woofers are flush mount on the back part of the baffle and are closed by 12.5mm front baffle on top. - easy to figure out and replicate...
And I'm sure that the DSP settings would be easy to figure out too.
Now for some simple mechanics... SD of the Eminence would be around 855 cm2 (132.5 sq in) and the face of the opening is 213 cm2 (33 sq in) - this is exactly 4 times smaller.
I can bet that the air velocity at the opening does not reach 4 times the velocity of the membrane! And that it's effective face is less than the phisical too I even can bet that the flow through it is non uniform! Due to the close proximity of the barrier to the piston there is a radial flow perpendicular to the axis of movement of the piston.
The air also has mass and thus inertia. In such small enclosure relative to the piston area the twist from one axis of movement must occur in very complex way, but that is another story.
The area of the "port" is effectively smaller, because the air traveling next to the front wall of the chamber has to take a 90 degree turn, which is a hard task for every substance obtaining mass and thus that turn gains certain radius.
But don't forget that this is movement of air mass from the perimeter to the center and there is another movement which is on an perpendicular axis - all that is mixed in the opening resulting in several low-high pressure/velocity areas across it and thus reducing it's effective face. And at this place the air is once more compressed due to it's inertia towards the open end.
Compressing always happens due to work exercised over certain time period... which in this case is for surely out of pace with the initial cone movement and compression.
Do you know why a horn has gentle slopes and flowing curves? - Yes! because air doesn't like to be pushed very hard... actually while at atmospheric pressure and at room temperature it has at least 200 bar towards it's liquid state (thus pretty much linear compression in the first several bars) it has only one bar towards the absolute vacuum... so it rather hates to be sucked through very steep angles... and then it behaves differently opposed to being pushed through small holes.
As a conclusion I see that "device" as an air decoubler - let the acoustics specialists say whether this is good or not... For me this is an a-synchronous air decoupler that gets more and more severe with the increase of the driver excursion. It just seems that the compressed and accelerated air would continue to evade the cavity after the cone has began it's back movement and on bigger cone excursions regimes the air wouldn't be able to manage to get back in the same quantity due to disintegration of the flow through the opening... - note that at switching of cycles the air around the opening is accelerated away from it!
Another consideration is that due to air compression losses efficiency would suffer (some excoursion is used only for compressing of air, but not for moving - remember, air got inertia). The resulting limited flow through the opening and due to the fact that the opening is flush mounted on a flat board (not a horn or waveguide) there is no air column above it to be set in motion in order to make use of the energy of the accelerated air exiting the hole. So it occurs to me that actually less air mass would be set in motion.
And in addition a 4.5 liter enclosure does not contain enough mass (5.4 grams specifically) to counter an accelerated 60 gramme membrane even though that the membrane is suspended, the speed of the air would have to be near 10 times the speed of the membrane... so there just isn't enough inertia to effectively limit cone movement! There even are no evidences for capillary effects as well! (small pipes can sometimes present enormous resistance... but only very tiny ones - that's due to the surface tension of fluids and especially liquids and pressure waves, but only when they travel through microscopic pipes...)
Again a parallel with horns - in terms of efficiency a horn is a device used to couple a driver membrane to an area of air that is bigger than it's actual membrane area and thus the efficiency gains.
A horn does not suffer from membrane decoupling and flow disintegration (sort of shredding, known also as pressure disintegration in hydraulics) because the rate of the cross-section decrease/increase is consistent with the air compressing rate at the respective pressure differences across the path length.
EDIT: and there is yet another consideration why didn't they do this trick on the back of the speaker? - it's not impossible... but if they did it would look exactly as the OB's we all very well know
Best regards from me!
The 15 inch Alpha powered version is scandalous too! The whole system together with the crossover utilizes parts worth 700-750$ - mention that: on retail prices! And this sells for nearly 5.000$
Not that the profit rate is uncommon for a market such as the hi-fi or hi-end hi-fi... it's not uncommon for any market!
But double 15 inchers on an OB with DSP is something that we very well know! Half the forum has twin or single Eminence 15 inch OB's and the other half have 18 inch Goldwoods on H-frames!
With the cone area of twin 15's and EQ it's normal that 15hz @ -3 are achieved. - No one mentions at what power input and until what power input though!
The "18 Goldwoods run out of excursion with about 7 to 17 watts with sine wave at 20 hz... and they are rated to be 18hz@-6 db in the H-frame...
15 hz@ -3 db for the "15's would mean that they are EQ-r*ped and I doubt if they would last more than 15-20 watts before reaching max excursion!
Note as well that those ports are not that restrictive at all and if you bare in mind that the air compression is linear almost until liquid state and you'll know why those speakers look like that!
They are just selling DIY projects masked as highly sophisticated commercial products!
And they deserve we to replicate their design completely and publish the plans together with the DSP settings for free download!
As I see it the woofers are flush mount on the back part of the baffle and are closed by 12.5mm front baffle on top. - easy to figure out and replicate...
And I'm sure that the DSP settings would be easy to figure out too.
Now for some simple mechanics... SD of the Eminence would be around 855 cm2 (132.5 sq in) and the face of the opening is 213 cm2 (33 sq in) - this is exactly 4 times smaller.
I can bet that the air velocity at the opening does not reach 4 times the velocity of the membrane! And that it's effective face is less than the phisical too
I even can bet that the flow through it is non uniform! Due to the close proximity of the barrier to the piston there is a radial flow perpendicular to the axis of movement of the piston.The air also has mass and thus inertia. In such small enclosure relative to the piston area the twist from one axis of movement must occur in very complex way, but that is another story.
The area of the "port" is effectively smaller, because the air traveling next to the front wall of the chamber has to take a 90 degree turn, which is a hard task for every substance obtaining mass and thus that turn gains certain radius.
But don't forget that this is movement of air mass from the perimeter to the center and there is another movement which is on an perpendicular axis - all that is mixed in the opening resulting in several low-high pressure/velocity areas across it and thus reducing it's effective face. And at this place the air is once more compressed due to it's inertia towards the open end.
Compressing always happens due to work exercised over certain time period... which in this case is for surely out of pace with the initial cone movement and compression.
Do you know why a horn has gentle slopes and flowing curves? - Yes! because air doesn't like to be pushed very hard... actually while at atmospheric pressure and at room temperature it has at least 200 bar towards it's liquid state (thus pretty much linear compression in the first several bars) it has only one bar towards the absolute vacuum... so it rather hates to be sucked through very steep angles... and then it behaves differently opposed to being pushed through small holes.
As a conclusion I see that "device" as an air decoubler
- let the acoustics specialists say whether this is good or not... For me this is an a-synchronous air decoupler that gets more and more severe with the increase of the driver excursion. It just seems that the compressed and accelerated air would continue to evade the cavity after the cone has began it's back movement and on bigger cone excursions regimes the air wouldn't be able to manage to get back in the same quantity due to disintegration of the flow through the opening... - note that at switching of cycles the air around the opening is accelerated away from it!Another consideration is that due to air compression losses efficiency would suffer (some excoursion is used only for compressing of air, but not for moving - remember, air got inertia). The resulting limited flow through the opening and due to the fact that the opening is flush mounted on a flat board (not a horn or waveguide) there is no air column above it to be set in motion in order to make use of the energy of the accelerated air exiting the hole. So it occurs to me that actually less air mass would be set in motion.
And in addition a 4.5 liter enclosure does not contain enough mass (5.4 grams specifically) to counter an accelerated 60 gramme membrane even though that the membrane is suspended, the speed of the air would have to be near 10 times the speed of the membrane... so there just isn't enough inertia to effectively limit cone movement! There even are no evidences for capillary effects as well! (small pipes can sometimes present enormous resistance... but only very tiny ones - that's due to the surface tension of fluids and especially liquids and pressure waves, but only when they travel through microscopic pipes...)
Again a parallel with horns - in terms of efficiency a horn is a device used to couple a driver membrane to an area of air that is bigger than it's actual membrane area and thus the efficiency gains.
A horn does not suffer from membrane decoupling and flow disintegration (sort of shredding, known also as pressure disintegration in hydraulics) because the rate of the cross-section decrease/increase is consistent with the air compressing rate at the respective pressure differences across the path length.
EDIT: and there is yet another consideration
why didn't they do this trick on the back of the speaker? - it's not impossible... but if they did it would look exactly as the OB's we all very well know Best regards from me!
Last edited:
Old thread new question
I have made round up/down firing subs with the "emerald" ports facing to the ceiling. They sound very good, and measure good too.
I would like your opinion on the following: What would happen to the "peaky behavior" when placing the ports off axis ?
Would appreciate your comments
Peter
I have made round up/down firing subs with the "emerald" ports facing to the ceiling. They sound very good, and measure good too.
I would like your opinion on the following: What would happen to the "peaky behavior" when placing the ports off axis ?
Would appreciate your comments
Peter
No response
Anyone listened to the CS1 in the shows? Or anyone knows why they stopped making this model?
I heard it at the CAS two years ago. I brought a CD of myself playing several songs on the Hammond B3. I sounded so real through the system, it gave me goosebumps. The only time I heard this recording sound better, it through my studio system consisting of Dunlavy SC-V/Bryston 28B SST amps
I built something similar.
The tops are Synergy horns, with Vifa XT25 at the apex flanked by four dipole Dayton ND91s
The woofer is similar to the Emerald Physics, but with a Diyma12 woofer. (Fairly similar to the Peerless XLS subs.)
The red curve is the 12" woofer in a simple U-Frame, about 30cm deep
The green curve is with a coupling chamber, similar to the Emerald Physics. You can see the coupling chamber reduces high frequency output, just as a coupling chamber on a horn or a bandpass does
The blue curve is with fiberglass batting inside the coupling chamber. It *really* cleans up the response.
Not an expert, but it looks to me like a modified U shaped baffle. The front chamber probably creates propagation delay, allowing more low end from the dipole. I've read that U shaped baffles usually have stuffing to control the 1/4 wavelength resonance. The stuffing also can extend low frequency response. If the chamber delays sound, like stuffing, then it may also extend low end FR. I want to try this.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.