Virtuix Cad
Enter a baffle size in the diffraction tool, and create 2 separate full space simulations with off axis data for 2 woofers according to their positions.
In crossover tap when simulating set Y axis to resemble correct center to center spacing they will be mounted.
Basically the sim will have full space losses shown and response on a baffle. And setting Y axis will have right phase to see the interaction
or canceling in the vertical. Simply cross over the lower woofer, lower to fill in the step in the response created by the baffle and full space losses
AKA baffle step.
Very quick guide of course.
For limited space project/tower with 2x 6.5" woofers. Great idea
Quick easy project would be 2 way or 2.5 way.
Basically the lower woofer is crossed over lower to slightly make up for full space losses.
Likely a Zillion suggestions for 6.5 inch woofers.
Even though Qts is a little high around .5
I would use 2x Visaton W170S-8 ohm, lots of bass for a relatively budget woofer.
And a large tweeter which will work in sim and real life with no waveguide to cross low to 6.5"
Is good old Dayton RST28F ( fabric) or RST28A ( aluminum) 1 1/8 " tweeters around 700 ish Fs
So you can cross low. Also have truncated mounting plate so you can mount them very very close.
All the vertical behavior will be understood in sim as long as all the Y coordinates are set right so the phase behavior is correct.
Tweeter is 0,0 xy it is listening position. First woofer Y is set for distance from tweeter center, second woofer Y distance is set from
center of first woofer. Cant make a drawing now, but a simple drawing done in sketch up, will make all your sim distances more accurate.
@Bmsluite Not a proposed design, but could be. 2x 6.5" and truncated dayton tweet
Just a example how I cheat make things easy for setting up your sim.
Basically all the work done, just to sim real quick from a old drawing I dug up.
I make a simple cad drawing, So I can arrange everything in the diffraction tool for drivers positions/baffle
Then know center to center distance to enter in X,Y all in a line so only Y
Tweeter is " listening position" so can start at 0, 0 for X,Y
In diffraction tool set drivers to those positions, with mic centered on each driver, export as full space vertical, horizontal off axis.
Then to get right phase, enter Y in crossover driver tap.
In crossover tap open 3 drivers, when your using diffraction tool you can also select " feed speaker"
Highlight the driver in crossover tap you want to " feed" too.
Saves time, hunting for your diffraction tool FRD exports, it just drops them right into the driver FRD
off course as you do each driver make sure you highlight the right driver in the crossover tap.
When I export in diffraction tool I give the name woofer 1 woofer 2 etc etc.
Making sure I didnt screw up the feed, since the FRD file names will a have a reference.
Just a example how I cheat make things easy for setting up your sim.
Basically all the work done, just to sim real quick from a old drawing I dug up.
I make a simple cad drawing, So I can arrange everything in the diffraction tool for drivers positions/baffle
Then know center to center distance to enter in X,Y all in a line so only Y
Tweeter is " listening position" so can start at 0, 0 for X,Y
In diffraction tool set drivers to those positions, with mic centered on each driver, export as full space vertical, horizontal off axis.
Then to get right phase, enter Y in crossover driver tap.
In crossover tap open 3 drivers, when your using diffraction tool you can also select " feed speaker"
Highlight the driver in crossover tap you want to " feed" too.
Saves time, hunting for your diffraction tool FRD exports, it just drops them right into the driver FRD
off course as you do each driver make sure you highlight the right driver in the crossover tap.
When I export in diffraction tool I give the name woofer 1 woofer 2 etc etc.
Making sure I didnt screw up the feed, since the FRD file names will a have a reference.
Exactly…..and let’s not forget the .5 circuit that allows for spacing the two woofers farther apart to avoid lobing and reduce baffle step……one woofer close to the floor and the second close to the mid……wouldn’t do this with a 2 way though. Now with baffle losses reduced we can create our tall slim tower speaker with low frequency extension, improved spatial imaging and spouse acceptance factor
Here’s a very interesting little driver with an even more attractive use case for say 6 drivers…..two parallel groups of three wired in series for a nominal 6 ohm load and +6 db sensitivity. Not to mention no to minimal low pass filter required.
https://www.parts-express.com/pedocs/specs/295-248--dayton-audio-rc180-55-specification-sheet.pdf
An f3 of 55hz but were sealed…….so an f6 of 38hz or so……keep it close to the wall and we can do even better. Mount it on the wall and now we’re talkin.
The woofer should not be too high from the ground. That is where you will get the classic null or additional dip in the low end
people get in room.
Close to the floor is important, but the large floor plane not the entire problem.
It is actually the combination of the large floor area , and the null is actually finally created by the distance from the side wall.
But since the side wall distance will vary room to room, to stop most the problem, you have to remain close to the largest plane. Typically the floor.
Actually sound doesn't care if the room is upside down or not. You do, most people dont stand on the ceiling.
But if you wanted to mount the speakers very very high, again sound doesnt care if you upside down or not.
Your basically dealing with 2 very large planes the floor or ceiling.
So a very very high mounted speaker, then the ceiling is consider the ground, then the woofer must be real close to the ceiling.
Doesnt matter upside down or not, your either very close to the ground or ceiling with the woofer.
Usually no more than 24 to27" from the largest plane, then the final null is actually created by the side wall.
As mentioned we cant change side wall distance as much as the larger plane, floor, or ceiling make your choice.
Of course if your very very close to the large plane, ground or ceiling less than 12" then highly unlikely the side wall will ever cause a null.
Small speakers on stands are nice for the tweeter to be at ear level. But your very likely to be typical furniture height
Say 30 to 36" from the large ground plane or ceiling, even further. So the side wall distance will yes guarantee to cause the classic bass null
in room.
" Multi" sub to rid the bass null almost nonsense. Again very very close to the floor. Side wall interaction completely goes away in the corner.
Any further long distance plane to create that null, eliminated if you point the sub straight up.
Straight up, in corner no null. with multi sub a sub towards the center of room, guarantees a null regardless. At least go to one wall and straight...up
Sound doesnt care if your upside down so if you had a sin sub woofer mounted high, make a wild guess how to do it. it is upside down figure it out.
people get in room.
Close to the floor is important, but the large floor plane not the entire problem.
It is actually the combination of the large floor area , and the null is actually finally created by the distance from the side wall.
But since the side wall distance will vary room to room, to stop most the problem, you have to remain close to the largest plane. Typically the floor.
Actually sound doesn't care if the room is upside down or not. You do, most people dont stand on the ceiling.
But if you wanted to mount the speakers very very high, again sound doesnt care if you upside down or not.
Your basically dealing with 2 very large planes the floor or ceiling.
So a very very high mounted speaker, then the ceiling is consider the ground, then the woofer must be real close to the ceiling.
Doesnt matter upside down or not, your either very close to the ground or ceiling with the woofer.
Usually no more than 24 to27" from the largest plane, then the final null is actually created by the side wall.
As mentioned we cant change side wall distance as much as the larger plane, floor, or ceiling make your choice.
Of course if your very very close to the large plane, ground or ceiling less than 12" then highly unlikely the side wall will ever cause a null.
Small speakers on stands are nice for the tweeter to be at ear level. But your very likely to be typical furniture height
Say 30 to 36" from the large ground plane or ceiling, even further. So the side wall distance will yes guarantee to cause the classic bass null
in room.
" Multi" sub to rid the bass null almost nonsense. Again very very close to the floor. Side wall interaction completely goes away in the corner.
Any further long distance plane to create that null, eliminated if you point the sub straight up.
Straight up, in corner no null. with multi sub a sub towards the center of room, guarantees a null regardless. At least go to one wall and straight...up
Sound doesnt care if your upside down so if you had a sin sub woofer mounted high, make a wild guess how to do it. it is upside down figure it out.
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When have you measured this?
I think you are confusing headroom with output impedance. No amplifier can exceed it's power supply, so sure the more current you are drawing the lower the maximum voltage swing that can be sustained (assuming we do not exceed thermal limits). Those are true statements but they apply at the limits of the amplifier power.
Well below that where most of us listen my understanding is that what matters is the amplifier "output impedance" which is the measured effects of the complex sum of the output stages, feedback and power supply impedance. At that place you should be looking at damping factor as a guide for how well the amplifier will maintain output vs. input vs. frequency. Solid state amplifiers today usually have at least a DF of 100 (0.08 Ohms) or higher, especially in the bass section. If you expect to use a tube amplifier that's another story and you are well served by keeping the entire speaker impedance above the recommended minimums.
The other losses you mention are so trivial that we usually deal with them in crossover design without even thinking about it, so not sure why this is important. That is, assuming there were any significant losses in wiring or amplifier performance we would have measured it and adjusted for it without even knowing they were there.
Obviously no amplifier can do that. And yes.
But you can design a amplifier for a higher voltage swing fairly easily without a lot of added cost.
Designing it for a higher current load is another thing, that means scaling up everything thermally including the PCB trays, wiring, capacitors temp rating, cooling fins etc etc.
A power transformer will become less efficient the more current you draw from it, resulting in reduced efficiency and thermal losses.
Now remember that your speaker cables, resistors and inductors in terms of power and heating is simply pieces of wire, with differentiating resistance and CSA.
Now onto the next question what generates heat in a electrical circuit? Current / Amperes. Look it up where you wish.
If you want equal output from a series and paralell circuit.
The series connection results in a higher voltage and less current. Yes?
The paralell connection results in a higher current draw due to the decreased imp. So the current is higher and voltage is lower. Yes?
So if the amps are identical.
The one running into the lower impedance will produce a magnitude more heat, meaning a loss in efficiency due to the added thermal stress.
And yes you can build them to tolerate that to some degree.
Good old Krell FFPB's , evo's,. ASR Emitter etc. are good examples.
Something that more or less doubles it's output all the way down into 0-1 ohms.
There are very few amps that handles that especially these days.
When you see any amp that cannot do that, it is thermally compromised and it will show depending on the power demand.
It's not my formula, but you got the math correct, the far field has been reached at just 20.4 inches, (.52 meters).
Sound in a free field will drop at 6 dB per doubling of distance after that short distance.
In a room, there will be constructive and destructive interference patterns from every boundary.
If speaker and listening positions are chosen correctly, the average may result in only minor deviations.
It's not immune, the difference in arrival time between the direct sound and reflected sound are lessened, moving the first cancellation frequency higher, increasing in frequency at a longer distance as the path length of the reflection reduces relative to the direct path, reducing the arrival time difference.
Depending on the frequency and listening or measurement axis, you can consider them as either.
The individual drivers are each point sources above their beam frequency.
If you define "beam frequency" as a radiation pattern where the -6dB point is ~90 degrees, it's roughly the speed of sound divided by the driver cone diameter, 565Hz for 24", 1130Hz for 12", 2260Hz for 6", etc.
Each driver is more of a "point source" as it becomes more directional.
At or above the "beam frequency", the SPL of the reflection compared to the direct SPL may have already been reduced by 6dB before the inverse square loss of 6dB per doubling of distance is even considered.
The amplitude of constructive or destructive interference is inversely proportional to the direct to reflected SPL, a 1/1 ratio theoretically being a maximum of +6dB constructive, and a complete cancellation for frequencies 180 degrees out of phase.
Fortunately, the reflections are never at a 1/1 ratio to the direct level in a room.
Any way you figure it, there is no "one size fits all" rule for woofer height or orientation, just compromises that may work better for individual rooms and listening distance and position.
Art
I appreciate all the details. I thought we used near ground plane measurements with the assumption that we'd have no reflectios so was a very good way to achieve quasi-anechoic responses from woofers and subwoofers, even if the subwoofer was not actually embedded in the floor. 😀
I'm familiar with the issues of boundary reflections but for my questions I really just wanted to focus like a laser in understanding the physics of multiple drivers placed adjacent to each other and how that affected the radiating wave front(s), so I'm going to focus on how apparently my prior understanding of that seems to have been mistaken.
So I had thought that at low frequencies (wavelength >> diameter of driver) the wave fronts from each driver became planar. That is, if I added several woofers, I'd get the identical wavefront as if I had used a planar like an ESL. That is, a single flat wavefront. It seems this is mistaken, but can be approximately true at distances given by the formula above, but that's the estimate. The reality is if I stack 5 woofers on top I have 5 point sources. How they add and subtract is also not what i'm asking yet. Just want to understand the wave fronts.
So, reality with my 5 stacked subs is that I have 5 spherical wavefronts which will add and subtract in complex ways. It's not the same as if I had a theoretical 5' tall and 1' wide driver in a box.
Is my last statement correct?
I'm familiar with the issues of boundary reflections but for my questions I really just wanted to focus like a laser in understanding the physics of multiple drivers placed adjacent to each other and how that affected the radiating wave front(s), so I'm going to focus on how apparently my prior understanding of that seems to have been mistaken.
So I had thought that at low frequencies (wavelength >> diameter of driver) the wave fronts from each driver became planar. That is, if I added several woofers, I'd get the identical wavefront as if I had used a planar like an ESL. That is, a single flat wavefront. It seems this is mistaken, but can be approximately true at distances given by the formula above, but that's the estimate. The reality is if I stack 5 woofers on top I have 5 point sources. How they add and subtract is also not what i'm asking yet. Just want to understand the wave fronts.
So, reality with my 5 stacked subs is that I have 5 spherical wavefronts which will add and subtract in complex ways. It's not the same as if I had a theoretical 5' tall and 1' wide driver in a box.
Is my last statement correct?
I've scanned through this thread, 99% of it is way above my pay grade. Somebody seemed to suggest that beyond protecting the amp - series is pointless.
Because I'm green - I have a question.
1) Single 8ohm driver: Box delivers 90dB
2) 2 x 8ohm parallel drivers: Box delivers 96dB
3) 2 x 8ohm series drivers: Box delivers 90dB
In each of these scenarios how much juice is a class D amp pulling from the wall. Or is gas mileage not a consideration?
Because I'm green - I have a question.
1) Single 8ohm driver: Box delivers 90dB
2) 2 x 8ohm parallel drivers: Box delivers 96dB
3) 2 x 8ohm series drivers: Box delivers 90dB
In each of these scenarios how much juice is a class D amp pulling from the wall. Or is gas mileage not a consideration?
One answer would be to see post # 10... But I can explain it in a bit more detail than that table does.
Let's assume a single 8R driver with a sensitivity of 90 dB/2.83V @ 1m. It also has an efficiency of 90 dB/W. It draws 0.35 A from the amplifier.
Now we put two of these drivers in parallel, and assuming it is a woofer we double the box volume and adjust the vent, so the tuning remains the same. Each driver sees 2.83 V, and each driver draws 0.35 A. Each driver individually consumes 1 W and produces 90 dB SPL. The total current delivered by the amplifier is 0.7 A, and the total power consumed by the two drivers is 2 W. The total output of the two drivers is 96 dB SPL. If we turn down the amplifier so we get 1 W of output, the amplifier voltage and current is 2 V and 0.5 A, and the total SPL is 93 dB. The result is the system sensitivity is 96 dB/2.83V, the impedance is now 4R, the efficiency is 93 dB/W.
Next we put the two drivers in series, and adjust the box volume and vent as necessary. The two 8R drivers in series now have a total impedance of 16R. With 2.83 V, the current is 0.18 A, and the total power consumed by both drivers is 0.5 W. Each driver individually sees 1.41 V and consumes 0.25 W, and produces 84 dB SPL. Both drivers together produce 90 dB SPL. The net result is the system sensitivity is 90 dB/2.83V, the efficiency is 93 dB/W.
In the real world, amplifiers usually have 3 output limits. They have a voltage limit, they have a current limit, and they have a long-term (thermal) power limit. If you compare two different amps which are both rated at 100 W into 8R, it is very likely that the 4R and 2R ratings will be different, and the long term power limit will be different. This is why the question is a bit complicated. How much power and sound you can get from an amp+speaker is not a simple question. It depends on the amp and the speaker, and it requires some calculations...
Series connection is less common than parallel connection, particularly with 8R drivers. There are design scenarios where series connection makes sense.
j.
wimps...
That said, I still have a pair of ADS L810s in perfect, refurbished shape with dual 8" woofers.
They have astonishing bass, not like the IRS above, but incredible fast deep bass. Sitting on 12" metal stands, the woofers are about 2 and 3 feet above the floor and the stands angle the speakers a little bit backwards.
The have really good bass.... no lobbing, no strange standing waves... the idea then was that two 8 inch woofers could move faster than a larger 10 incher.
I also have a tall PSB Goldi tower... it has a Big Ten Inch woofer, biamped, close to the floor with a big 5 inch port. It also has very good bass, deeper than the ADS, but it sounds different. The PSB has a large midrange and single tweeter to the top ( inverted ) and it was sold as a minimonitor with a subwoofer... which pretty much defines its sound. It has less mid bass "power" than the 810s, but it goes deeper. The PSBs also have much better imaging ( but that's comparing a '76 and an '01 speaker... not fair.
In my experience with such things, what you gain with multiple woofer sis "speed". You get more motor per square inch of woofer.... and each woofer does add +3db to the acoustic output -when in parallel and assuming your amp can drive all that current.
That said, I still have a pair of ADS L810s in perfect, refurbished shape with dual 8" woofers.
They have astonishing bass, not like the IRS above, but incredible fast deep bass. Sitting on 12" metal stands, the woofers are about 2 and 3 feet above the floor and the stands angle the speakers a little bit backwards.
The have really good bass.... no lobbing, no strange standing waves... the idea then was that two 8 inch woofers could move faster than a larger 10 incher.
I also have a tall PSB Goldi tower... it has a Big Ten Inch woofer, biamped, close to the floor with a big 5 inch port. It also has very good bass, deeper than the ADS, but it sounds different. The PSB has a large midrange and single tweeter to the top ( inverted ) and it was sold as a minimonitor with a subwoofer... which pretty much defines its sound. It has less mid bass "power" than the 810s, but it goes deeper. The PSBs also have much better imaging ( but that's comparing a '76 and an '01 speaker... not fair.
In my experience with such things, what you gain with multiple woofer sis "speed". You get more motor per square inch of woofer.... and each woofer does add +3db to the acoustic output -when in parallel and assuming your amp can drive all that current.
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I believe that with parallel drivers, you double the electrical power but quadruple the audible power. That is, electrical power coming from the amp is 3 dB more, but audible power is +6 dB. So from a watt to watt example the parallel drivers are more efficient.
Also these are super easy to try out with XSim or VituixCAD.
wimps...
Haha... a stack of six wimpy 12"s ?? ....
How about my just finished stack of four 18"s...😀
If you read post #40, you'd see that the simple answer is that two drivers actually draw half the power of a single driver, whether they are connected in series or in parallel. As to how any specific amp behaves, that's a different matter, as @hifijim points out above.
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Well, I guess we should give Nelson his due.... I suppose having a room with a tall ceiling and a
wife that understands goes a long way, huh?
https://www.passdiy.com/pdf/el-pipe-o.pdf
The pictures shows it before they drank too much red wine.... when there were two woofers per side.
wife that understands goes a long way, huh?
https://www.passdiy.com/pdf/el-pipe-o.pdf
The pictures shows it before they drank too much red wine.... when there were two woofers per side.
Both Tony’s &nMark’s multiple woofer subs, since they have even number of woofer’s, whynaren’tnthey push-push.
Currently working on a Twin TAD 18” woofer. There will be a minimum of 4 of them, each with their own big Purifi amp.
Big towers that maximize visible woofers are “mine is bigger than yours” cosmetics.
Nelson’s El-Pipo is an interesting design example, but even when half the woofers died and they ended up with one per tube the line is too small (fat) to properly do the job.
These earlier examples are also too small:
https://www.t-linespeakers.org/projects/steve/index.html
This one was theoretical, http://www.t-linespeakers.org/FALL/push-push.html
dave
PS: For anyone driving by I have the essential bits for a miniEl-Pipo with Eastech 7” woofers,
Currently working on a Twin TAD 18” woofer. There will be a minimum of 4 of them, each with their own big Purifi amp.
Big towers that maximize visible woofers are “mine is bigger than yours” cosmetics.
Nelson’s El-Pipo is an interesting design example, but even when half the woofers died and they ended up with one per tube the line is too small (fat) to properly do the job.
These earlier examples are also too small:
https://www.t-linespeakers.org/projects/steve/index.html
This one was theoretical, http://www.t-linespeakers.org/FALL/push-push.html
dave
PS: For anyone driving by I have the essential bits for a miniEl-Pipo with Eastech 7” woofers,
Hmm... I forget... what do you call that design where you make one wall disappear by putting lots of drivers on it?
The idea is to make seem like the room is much bigger than it this by canceling the sounds waves hitting it.
The HT guys use that to develop very long low frequency waveforms...
Tri-something?
Yea... here, Trinov Waveforming....
https://www.ecoustics.com/news/trinnov-expands-waveforming-affordable-home/
https://www.trinnov.com/en/technologies/active-acoustics/waveforming/
Fix the room first, then add woofers...
You could build a fake, 6 inch deep "wall" with a lot of small, 4" woofers... build two... one for the front of the room and one for the back of the room... you could start experimenting with stuff like these ( I got two of the passive ones, with low pass crossover and a little amp )...
https://www.parts-express.com/Dayto...t-Low-Profile-Powered-Subw-300-639?quantity=1
Take the woofers out of the speaker.... make the wall the speaker. In essence, start thinking OUTSIDE THE BOX...
The idea is to make seem like the room is much bigger than it this by canceling the sounds waves hitting it.
The HT guys use that to develop very long low frequency waveforms...
Tri-something?
Yea... here, Trinov Waveforming....
https://www.ecoustics.com/news/trinnov-expands-waveforming-affordable-home/
https://www.trinnov.com/en/technologies/active-acoustics/waveforming/
Fix the room first, then add woofers...
You could build a fake, 6 inch deep "wall" with a lot of small, 4" woofers... build two... one for the front of the room and one for the back of the room... you could start experimenting with stuff like these ( I got two of the passive ones, with low pass crossover and a little amp )...
https://www.parts-express.com/Dayto...t-Low-Profile-Powered-Subw-300-639?quantity=1
Take the woofers out of the speaker.... make the wall the speaker. In essence, start thinking OUTSIDE THE BOX...
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What kind of processing is required?
Aaah... I see...
https://en.wikipedia.org/wiki/Double_bass_array
Just a delay and drive the back speakers out of phase. Hmmm, I got most of the parts except for the delay gizmo....
I think my wife is gonna kill me.....
Aaah... I see...
https://en.wikipedia.org/wiki/Double_bass_array
Just a delay and drive the back speakers out of phase. Hmmm, I got most of the parts except for the delay gizmo....
I think my wife is gonna kill me.....