I am designing a 3.5 way speaker system (at least I think that is the correct term haha 
) consisting of a planar-magnetic tweeter, 2" dome midrange, 6.5" mid/woofer, and a second identical 6.5" driver but used only as a woofer.
It may sound like a strange combination, but having reviewed the characteristics of the drivers I plan to use it should work pretty well. I will be using a pair of the Foster planar/ribbon tweeters, crossed over at 6K to a HiVi DMB-A dome mid, then that will cross at 1K to a HiVi D6G woofer (yes I know this is not an ideal crossover point, but compromises need to made).
The reason behind this theory, is looking at the response graph for the woofer, there is a strong resonance between 1-2k then the response drops off very fast. I plan to use the mid/woofer with a low pass at 900 Hz or so, so hopefully combined with the resonant peak and the rolloff from the filter should enable it to pass smoothly to the dome mid. There will likely be lots of trial and error, but thats part of the fun isn't it?
This leads me to my actual question regarding this project (all of the above is to put everything in context), is that I plan to use a second 6.5" driver as a woofer only, operating up to around 200 Hz (once again, trial and error and listening tests to find the best xover point) to augment the bass response, hence it being a 3.5 way.
In short, both the 6.5" drivers will only have a low pass filter, but one will be set to around 1K and the other to around 200 Hz. Is it okay to put these into the same cabinet together and have them share the same airspace, or would it be beneficial to put a divider between them and run as two independent enclosures? I thought about running the upper one in a sealed cabinet and the lower one in a vented box, but towards the lower end may get some phase differences between them so if I use two separate enclosures they will probably both be vented.
Or, would it likely not make much difference? I am pretty sure that I could get away with putting them together in the same airspace, as the cone excursion required by frequencies >200Hz should be small enough that the back wave from the woofer shouldn't have much effect, because the top woofer will still be carrying all the same info as the lower woofer, just with an extended upper range.
I want to do this properly, and I value any relevant input from others who either have more knowledge than I or have undertaken similar projects and know what works. Sorry if my post is a bit too long, I try my best to explain the situation in full to give a clear view of my intentions and help you to visualise the scenario. Thanks you for your time, any help is appreciated as always
) consisting of a planar-magnetic tweeter, 2" dome midrange, 6.5" mid/woofer, and a second identical 6.5" driver but used only as a woofer.It may sound like a strange combination, but having reviewed the characteristics of the drivers I plan to use it should work pretty well. I will be using a pair of the Foster planar/ribbon tweeters, crossed over at 6K to a HiVi DMB-A dome mid, then that will cross at 1K to a HiVi D6G woofer (yes I know this is not an ideal crossover point, but compromises need to made).
The reason behind this theory, is looking at the response graph for the woofer, there is a strong resonance between 1-2k then the response drops off very fast. I plan to use the mid/woofer with a low pass at 900 Hz or so, so hopefully combined with the resonant peak and the rolloff from the filter should enable it to pass smoothly to the dome mid. There will likely be lots of trial and error, but thats part of the fun isn't it?
This leads me to my actual question regarding this project (all of the above is to put everything in context), is that I plan to use a second 6.5" driver as a woofer only, operating up to around 200 Hz (once again, trial and error and listening tests to find the best xover point) to augment the bass response, hence it being a 3.5 way.
In short, both the 6.5" drivers will only have a low pass filter, but one will be set to around 1K and the other to around 200 Hz. Is it okay to put these into the same cabinet together and have them share the same airspace, or would it be beneficial to put a divider between them and run as two independent enclosures? I thought about running the upper one in a sealed cabinet and the lower one in a vented box, but towards the lower end may get some phase differences between them so if I use two separate enclosures they will probably both be vented.
Or, would it likely not make much difference? I am pretty sure that I could get away with putting them together in the same airspace, as the cone excursion required by frequencies >200Hz should be small enough that the back wave from the woofer shouldn't have much effect, because the top woofer will still be carrying all the same info as the lower woofer, just with an extended upper range.
I want to do this properly, and I value any relevant input from others who either have more knowledge than I or have undertaken similar projects and know what works. Sorry if my post is a bit too long, I try my best to explain the situation in full to give a clear view of my intentions and help you to visualise the scenario. Thanks you for your time, any help is appreciated as always
in short....yes, its ok they share the same box
its only the lowest frequencies that makes them move at all, meaning they will move the same anyway
now, if you would be using slightly differently specced woofers, which might be possible, then it 'could' be a different matter, depends
Both woofers are identical, so that shouldn't be an issue.
Thanks for your input, it confirms what I had thought
And regarding the mids back wave being reflected through the woofer, I will be using internal baffles as well as stuffing to help break up and dissipate any standing waves, so that should take care of that problem.
A single box is a poor effort, you should really isolate the woofer from the mid.
If not, you creating what is called a "passive radiator".
Passive radiator (speaker) - Wikipedia, the free encyclopedia
Adding stuffing will not be enough to dampen fluctuations in air pressure. Sound will travel from one cone to another in your existing design causing distortion.
In fact a true passive radiator would not suffer as much distortion as your design, as it only has one active element. In your design, you have two active elements working against, and interacting with each other.
If not, you creating what is called a "passive radiator".
Passive radiator (speaker) - Wikipedia, the free encyclopedia
Adding stuffing will not be enough to dampen fluctuations in air pressure. Sound will travel from one cone to another in your existing design causing distortion.
In fact a true passive radiator would not suffer as much distortion as your design, as it only has one active element. In your design, you have two active elements working against, and interacting with each other.
I don't see how I will be creating a passive radiator, the only difference between the signals the two 6.5" drivers will receive is the upper one will have more midrange, the bass content will be the same between them. And I doubt the midrange back-wave would have sufficient energy to modulate the cone of the lower woofer. In an actual passive radiator system, how much midrange information from the active driver comes out of the passive radiator?
Its not simply a midrange-only driver sharing the same cabinet with a woofer, that's just daft haha.
And to Pete McK, thank you for your suggestion, I will definitely consider that.
In all honesty I think this speaker will most probably turn into a mess, not because of your lack of skill or knowledge but because there is many crossover points and just dealing with one is hard enough. If your using passive crossovers (which are the work of the devil) the problem will be exaggerated.
Would the two woofers be side by side or vertical?
Seems like if you want to port the lower woofer and seal the mid woofer you would want separate boxes anyway right? That would leave you with a separate box for the mid/tweeter and the tweeter is sealed so then you'd have only the volume to worry about on the mid.
I agree with the number of crossover points being tricky
It could seem a little redundant doing that but it may also be more efficient. You're sort of getting 12" worth of woofer. Like a 12" coaxial woofer idea...
Sounds like an idea to try though!
Seems like if you want to port the lower woofer and seal the mid woofer you would want separate boxes anyway right? That would leave you with a separate box for the mid/tweeter and the tweeter is sealed so then you'd have only the volume to worry about on the mid.
I agree with the number of crossover points being tricky
It could seem a little redundant doing that but it may also be more efficient. You're sort of getting 12" worth of woofer. Like a 12" coaxial woofer idea...
Sounds like an idea to try though!
I guarantee you will have midrange coming out the woofer despite the multiple crossovers.
A friend of mine owned a piar for years without even realizing it, until he went to recone them and said "Where's the magnet off these speakers??"
They have almost all the movement and sound of an active speaker.
Visaton use a separate chamber for the woofer and bafflestep correction sub-woofer in the 3.5 way Symphonie. I'd guess they have their reasons.
The Casablanca III is a bit closer to your particular crossover points. Both would be worth exploring with Visaton's excellent BoxSim program. I found some very good results using the W300S 12" unit with their G 50 FFL dome midrange. The bigger driver is more efficient at around an impressive 90dB and has better phase alignment on a second order filter.
Of course, if you design for wallmounting bookshelf style, you can dump the second woofer anyway.
The Casablanca III is a bit closer to your particular crossover points. Both would be worth exploring with Visaton's excellent BoxSim program. I found some very good results using the W300S 12" unit with their G 50 FFL dome midrange. The bigger driver is more efficient at around an impressive 90dB and has better phase alignment on a second order filter.
Of course, if you design for wallmounting bookshelf style, you can dump the second woofer anyway.
Visaton may have had their reasons, but the JBL Everest puts both in the same chamber:
http://www.jblsynthesis.com/downloads/products/prod_92_634480738068402787_Everest%20DD66000%20HR.pdf
See illustration on page 13.
http://www.jblsynthesis.com/downloads/products/prod_92_634480738068402787_Everest%20DD66000%20HR.pdf
See illustration on page 13.
passive radiator ?
Alvis, its not a midrange driver
its a 2.5way principle converted to 3.5way
do you know what a 2.5way is
or else, time to look it up
not easy at all, no
and why 3.5way and not 'just' plain 3way
a lot of effort with such small drivers
may I ask, why ?
question is whether the mid dome is doing any good all, over a 'plain 2.5way design
Hi,
Quite frankly you have no idea what you are talking about and cannot
guarantee anything, if you understand the original question, if you don't .....
rgds, sreten.
There is no good reason to separate 0.5 way drivers in reality.
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Of course you agree with srten, he is the local authority?
I think perhaps Tinitus and Srten need an education in physics, not wishfull thinking.
When you have both woofers doing a bass compression, the mid will not be able to overcome these distortions, the power used for bass is higher, the surface area is doubles, so are the bass producing motors.
In a single driver the mid rides up and down on the woofer, aside from a little doppler effect, this more or less works, because the woofer moves in and out to from electrical signals creating the mid, the speaker is dictating the pressure responses.
Now when you add a second woofer, with no mid range riding along, this does not work well.
When both woofers compress, the air pressure rises and distorts the mid.
When the woofers move out, the vacuum created distorts the mid range.
The mid simply cannot move in it's proper range of motion with all that pressure modulation going on.
I promise.
I think perhaps Tinitus and Srten need an education in physics, not wishfull thinking.
When you have both woofers doing a bass compression, the mid will not be able to overcome these distortions, the power used for bass is higher, the surface area is doubles, so are the bass producing motors.
In a single driver the mid rides up and down on the woofer, aside from a little doppler effect, this more or less works, because the woofer moves in and out to from electrical signals creating the mid, the speaker is dictating the pressure responses.
Now when you add a second woofer, with no mid range riding along, this does not work well.
When both woofers compress, the air pressure rises and distorts the mid.
When the woofers move out, the vacuum created distorts the mid range.
The mid simply cannot move in it's proper range of motion with all that pressure modulation going on.
I promise.
We will doubtless descend into the usual depressing diyaudio spat if this line is further pursued. I will steer us in a slightly different productive direction.
The thing to know about midrange domes is that they are VERY EFFICIENT and have dispersion to die for!
They integrate BEAUTIFULLY with woofers and tweeters, but you may need to double up smaller drivers in the conventional way to match on efficiency.
I did an appraisal of the legendary Celestion Ditton 66 and AR-3A speakers, both of which use 12" bass and a dome:
I just used the Visaton Casablanca III 2nd order design and optimised it for different woofers. Interestingly, the big 10" and 12" woofers aligned best on phase and efficiency (90dB!) where small woofers struggled, and celestion's third order tweeter filter aligned very well around 10kHz, but less so at lower frequencies. Truly an interesting study. I really want a dome midrange. Superb what you can do with one.
The thing to know about midrange domes is that they are VERY EFFICIENT and have dispersion to die for!
An externally hosted image should be here but it was not working when we last tested it.
They integrate BEAUTIFULLY with woofers and tweeters, but you may need to double up smaller drivers in the conventional way to match on efficiency.
I did an appraisal of the legendary Celestion Ditton 66 and AR-3A speakers, both of which use 12" bass and a dome:
An externally hosted image should be here but it was not working when we last tested it.
I just used the Visaton Casablanca III 2nd order design and optimised it for different woofers. Interestingly, the big 10" and 12" woofers aligned best on phase and efficiency (90dB!) where small woofers struggled, and celestion's third order tweeter filter aligned very well around 10kHz, but less so at lower frequencies. Truly an interesting study. I really want a dome midrange. Superb what you can do with one.
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I'm sorry, but this simply isn't so.
You could use the same argument to "show" that a midbass in a small cabinet would also have modulation issues in the midrange.
Remember each bass driver would "see" half the cabinet volume, as, being identical, they'll each pressurise their own half of the cabinet exactly.
Imagine there is a dividing wall between the two chambers. When the woofers move, they each press on the wall. They have moved the same amount and occupy an equal volume of air to each other, so the pressure on the dividing wall must be the same on both sides. The forces cancel exactly and there's no movement of the wall because of this.
So if the wall does not experience any net force, why bother with it?
Doing without will yield the same results (so long as the cabinet is otherwise mechanically braced).
Chris
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