Not sure if this is a good idea or not. Still in the planning stages for my open baffle speaker
Could it be done to add a small sealed box woofer in phase, but mounted on the back of the baffle firing backwards, therefore out of phase with the rear output, thus diminishing the cancellation of the front wave?
Probably best to add a series resistor to decrease its output, also this would make for an easier amp load
Paul
Could it be done to add a small sealed box woofer in phase, but mounted on the back of the baffle firing backwards, therefore out of phase with the rear output, thus diminishing the cancellation of the front wave?
Probably best to add a series resistor to decrease its output, also this would make for an easier amp load
Paul
so thats what that back woofer is for on that speaker!
I was thinking of hot glue melting a box on the back, so it would be removable if not acceptable (for the trial phase).
The woofer would be pass band of around 150 Hz - 300 Hz with simple first order network
I wanted to use a full range on top with a H frame 2X 15 " eminence alpha on bottom, but instead of using BSC, using a rear firing woofer to eliminate the loss from the rear wave cancelling the rear output from the full range.
If the rear woofer was only going down to around 150 Hz, the box wouldn't need to be that big.
I was thinking of hot glue melting a box on the back, so it would be removable if not acceptable (for the trial phase).
The woofer would be pass band of around 150 Hz - 300 Hz with simple first order network
I wanted to use a full range on top with a H frame 2X 15 " eminence alpha on bottom, but instead of using BSC, using a rear firing woofer to eliminate the loss from the rear wave cancelling the rear output from the full range.
If the rear woofer was only going down to around 150 Hz, the box wouldn't need to be that big.
Have I understood Ped's example correctly. I have two Eminence Beta 15 A for an open baffle, but as MJK rightly said they are a bit more difficult than the Alpha for this use. If I put one of them in a reflex box with the cone facing upwards behind the baffle and the port facing forwards through the baffle would the rear eminence, if run out of phase with the open baffle eminence, cancel out the rear radiation of the open baffle eminence. Would the port, being out of phase with that rear driver and facing forward then be in phase with the open baffle driver for its output range. The reflex box would be smaller than ideal and this would also give a lift in the response which may of may not do too much cancelling.
If this would indeed work it should give a lift to the front firing eminence in the open baffle just as it starts to run out of xmax. I don't know though if this would be better than the increase in efficiency of having the two eminence facing forward in parallel in the open baffle. I am very aware that there is no such thing as a free lunch as they say. Any ideas.
jamikl
If this would indeed work it should give a lift to the front firing eminence in the open baffle just as it starts to run out of xmax. I don't know though if this would be better than the increase in efficiency of having the two eminence facing forward in parallel in the open baffle. I am very aware that there is no such thing as a free lunch as they say. Any ideas.
jamikl
Does nobody have any idea whether the speaker by Tekton on Peds link will work or not as per my question which covers how I imagine it is supposed to work.
This is the trend I refer to in another post where all sorts of discussions take place over countless pages with none of the experts agreeing with each other on sometimes pretty esoteric topics but what seems on the surface to be a simple question seems to be ignored.
My thanks to anybody who can take time to offer an opinion, jamikl
This is the trend I refer to in another post where all sorts of discussions take place over countless pages with none of the experts agreeing with each other on sometimes pretty esoteric topics but what seems on the surface to be a simple question seems to be ignored.
My thanks to anybody who can take time to offer an opinion, jamikl
That Tekton speaker is interesting.
My Idea was to build something like MJK's 2X alpha plus fostex open baffle speaker, but instead of using baffle step correction, use a smaller baffle for the FR, and use a second woofer (not a full range unit) mounted on the back with a passband of 200 Hz to 3 or 400 Hz to eliminate the back wave cancelling the front wave in this area.
Goal is to retain as high a sensitivity as possible.
Paul
My Idea was to build something like MJK's 2X alpha plus fostex open baffle speaker, but instead of using baffle step correction, use a smaller baffle for the FR, and use a second woofer (not a full range unit) mounted on the back with a passband of 200 Hz to 3 or 400 Hz to eliminate the back wave cancelling the front wave in this area.
Goal is to retain as high a sensitivity as possible.
Paul
Hi all
I've tried this method of rear-wave cancellation, and it definately works - more bass than the two speakers placed side by side, which is slightly confusing.......
I know it's a very late post, but that's because I had this idea buzzing around in my head (after reading several months back), so I got bored over a 3 day weekend, began cutting up wood etc, and tried it out, powered by a little 7W/channel stereo amp. So, using some cheap woofers from a broken 2.0 powered speaker set, I devised this: (see picture attached) and gave it a try. Now, I'm trying to figure out if the driver at the back should be in a huge box (same lack of damping as the OB speaker), or simply a larger driver, to compensate for the higher excursion of the smaller open-baffle driver. I suspect these measures wouldn't be needed if I used an open-baffle designed speaker, but these are rather
expensive. In contradiction to the above post, I ran both the drivers full-range.
The sound.
These drivers were originally used as woofers, so the very high frequencies aren't as nice as they could be, but this is a basic test.
The bass is pretty punchy, rather than deep and some of the notes in the song Do You Like The Way - Santana (has some deep bass), eluded the drivers used. The overall sheer volume of this set-up isn't up to much, mainly due to the drivers used, which aren't designed for an open-baffle speaker. So, reasonable listening levels only for now.
The plan.
I plan to get hold of some better suited drivers (have some Wharfedale modus speakers, just begging to be tested), and eventually make something with a single full-range driver, which might actually do the complete sound range which would be quite rare for an OB project.
Anyone else wanting to try something similar, perhaps with different drivers?
Chris.
I've tried this method of rear-wave cancellation, and it definately works - more bass than the two speakers placed side by side, which is slightly confusing.......
I know it's a very late post, but that's because I had this idea buzzing around in my head (after reading several months back), so I got bored over a 3 day weekend, began cutting up wood etc, and tried it out, powered by a little 7W/channel stereo amp. So, using some cheap woofers from a broken 2.0 powered speaker set, I devised this: (see picture attached) and gave it a try. Now, I'm trying to figure out if the driver at the back should be in a huge box (same lack of damping as the OB speaker), or simply a larger driver, to compensate for the higher excursion of the smaller open-baffle driver. I suspect these measures wouldn't be needed if I used an open-baffle designed speaker, but these are rather
expensive. In contradiction to the above post, I ran both the drivers full-range.
The sound.
These drivers were originally used as woofers, so the very high frequencies aren't as nice as they could be, but this is a basic test.
The bass is pretty punchy, rather than deep and some of the notes in the song Do You Like The Way - Santana (has some deep bass), eluded the drivers used. The overall sheer volume of this set-up isn't up to much, mainly due to the drivers used, which aren't designed for an open-baffle speaker. So, reasonable listening levels only for now.
The plan.
I plan to get hold of some better suited drivers (have some Wharfedale modus speakers, just begging to be tested), and eventually make something with a single full-range driver, which might actually do the complete sound range which would be quite rare for an OB project.
Anyone else wanting to try something similar, perhaps with different drivers?
Chris.
Attachments
chris661, I think that is what jamikl meant...
Found a couple of posts from people who have heard/bought these:
http://74.125.47.132/search?q=cache...speakers+open+baffle&cd=4&hl=en&ct=clnk&gl=uk
http://74.125.47.132/search?q=cache...speakers+open+baffle&cd=3&hl=en&ct=clnk&gl=uk
(Members only forum, so used google cached
)
http://techtalk.parts-express.com/showthread.php?p=1530940
Sounds promising. Assuming the front speaker is unequalised, the back one would at least need a low pass filter to match the roll off caused by the largest baffle dimension (6dB/octave, I think).
Found a couple of posts from people who have heard/bought these:
http://74.125.47.132/search?q=cache...speakers+open+baffle&cd=4&hl=en&ct=clnk&gl=uk
http://74.125.47.132/search?q=cache...speakers+open+baffle&cd=3&hl=en&ct=clnk&gl=uk
(Members only forum, so used google cached
)http://techtalk.parts-express.com/showthread.php?p=1530940
Sounds promising. Assuming the front speaker is unequalised, the back one would at least need a low pass filter to match the roll off caused by the largest baffle dimension (6dB/octave, I think).
This is a very crude set-up, so I think I should make a decent version before fiddling, but yes, I currently have this >1m into the room, with a guitar amp (you know what teenagers are like) behind it.
The whole idea for this design is to make an invisible tube of air, so you would, theoretically be able to place it up against a wall, with no ill effects.
Will test and report.
The whole idea for this design is to make an invisible tube of air, so you would, theoretically be able to place it up against a wall, with no ill effects.
Will test and report.
Tested and now reporting.
When the back speaker is up against the wall (open baffle speaker around 15cm), you get more bass, but it is tiring to listen to (had to move it away after the first track). At 50cm from the back wall, there's not a huge amount of bass, but what is there is pretty nice sounding.
So, to get it right, I put it around 30cm (OB driver distance) to the wall. Still listening to it now. Decent lows - you can tell what's going on, even if the deepest bits aren't all present. The midrange (although it's from a pretty rubbish driver) is good in comparison to how they sounded when in their plastic cab.
I know of some OB speakers that require a lot more than 30cm wall space to sound nice (Jamo 907s to name one), so I guess this is an improvement.
Chris
When the back speaker is up against the wall (open baffle speaker around 15cm), you get more bass, but it is tiring to listen to (had to move it away after the first track). At 50cm from the back wall, there's not a huge amount of bass, but what is there is pretty nice sounding.
So, to get it right, I put it around 30cm (OB driver distance) to the wall. Still listening to it now. Decent lows - you can tell what's going on, even if the deepest bits aren't all present. The midrange (although it's from a pretty rubbish driver) is good in comparison to how they sounded when in their plastic cab.
I know of some OB speakers that require a lot more than 30cm wall space to sound nice (Jamo 907s to name one), so I guess this is an improvement.
Chris
Thank you for reporting Chris, I appreciate it.
Going to do some testing for myself.
Edit: Actually I do have another question. Why put the boxed driver perpendicular to the front driver? Wouldn't putting the boxed driver behind on the same axis as the front work more effectively? I would think the rear driver would need a lowpass of some sort since the highs will be stronger than the rear wave of the front speaker due to the magnet obstruction.
Going to do some testing for myself.
Edit: Actually I do have another question. Why put the boxed driver perpendicular to the front driver? Wouldn't putting the boxed driver behind on the same axis as the front work more effectively? I would think the rear driver would need a lowpass of some sort since the highs will be stronger than the rear wave of the front speaker due to the magnet obstruction.
I agree with the need for a LP filter.
To answer your question:
The box positioned directly behind the OB driver would mean it would, effectively be up against a wall, which changes the bass (nasty cab resonances, short-range reflection). Also, the open-ness associated with OB speakers is lost, as the mid-range and treble sounds are sent backwards (not cancelled due to short W/L), and reflected off more distant walls.
Note - I am not an expert. These observations are simply from my own (limited) experience. If an expert comes along and tells you otherwise, you can guess who to believe.
The midrange sounds better positioned further away from the wall (more natural), which suggests reflecting those frequencies at a short range can affect them.
In conclusion: closer to wall = more bass (not nice bass though), midrange sounds worse.
further from the wall = less bass, nicer midrange.
This is only tested to confines of my bedroom. I haven't tested this in a concert hall.
To answer your question:
The box positioned directly behind the OB driver would mean it would, effectively be up against a wall, which changes the bass (nasty cab resonances, short-range reflection). Also, the open-ness associated with OB speakers is lost, as the mid-range and treble sounds are sent backwards (not cancelled due to short W/L), and reflected off more distant walls.
Note - I am not an expert. These observations are simply from my own (limited) experience. If an expert comes along and tells you otherwise, you can guess who to believe.
The midrange sounds better positioned further away from the wall (more natural), which suggests reflecting those frequencies at a short range can affect them.
In conclusion: closer to wall = more bass (not nice bass though), midrange sounds worse.
further from the wall = less bass, nicer midrange.
This is only tested to confines of my bedroom. I haven't tested this in a concert hall.
Thank you for your excellent responses. All your points make perfect sense...
The reason why I was asking all these questions was because the idea of a cardioid is quite intriguing for me. I am always looking for new ideas to try to incorporate them into a very difficult environment, my car I love to experiment with new ideas. I was bold enough to try full range drivers in a car, now I need something new to spend my time. Time do do some measuring.
The reason why I was asking all these questions was because the idea of a cardioid is quite intriguing for me. I am always looking for new ideas to try to incorporate them into a very difficult environment, my car
I love to experiment with new ideas. I was bold enough to try full range drivers in a car, now I need something new to spend my time. Time do do some measuring. chris661 said:
Interesting (perhaps) discovery.
Car FR speakers, such as http://www.visaton.com/en/car_hifi/breitband/fr12_4.html would be good for OB use, as car doors have big cabinets compared to what we would use for a hifi driver.
The Qts of that one is 1.87. The Aminence Alpha 15A (used commonly for OB projects) has a Qts of 1.2 (roughly
), so I'm going to experiment with drivers of different Qts.
Here's my thinking. Qts = mechanical stiffness (according to other sites), so a higher Qts would mean a larger box is required (bigger speakers, like the 15A need bigger boxes). A really high Qts driver would suggest it could be used in OB, which is the idea.
The link above shows the driver I'm getting today (they're fairly cheap, so no worries if they don't work). I may have to get a supertweeter to cover the dip in frequency response at 13-16kHz.
So, 1.5 way OB project it is.
Chris
PS - a car project would be interesting. Maybe mount the cancellation drivers on the parcel shelf, then put the OB speakers on top on the rear seat, as a test. You would probably have to fight off the teenagers wondering how much Xmax the drivers have though.....
Car FR speakers, such as http://www.visaton.com/en/car_hifi/breitband/fr12_4.html would be good for OB use, as car doors have big cabinets compared to what we would use for a hifi driver.
The Qts of that one is 1.87. The Aminence Alpha 15A (used commonly for OB projects) has a Qts of 1.2 (roughly
), so I'm going to experiment with drivers of different Qts.Here's my thinking. Qts = mechanical stiffness (according to other sites), so a higher Qts would mean a larger box is required (bigger speakers, like the 15A need bigger boxes). A really high Qts driver would suggest it could be used in OB, which is the idea.
The link above shows the driver I'm getting today (they're fairly cheap, so no worries if they don't work). I may have to get a supertweeter to cover the dip in frequency response at 13-16kHz.
So, 1.5 way OB project it is.
Chris
PS - a car project would be interesting. Maybe mount the cancellation drivers on the parcel shelf, then put the OB speakers on top on the rear seat, as a test. You would probably have to fight off the teenagers wondering how much Xmax the drivers have though.....
I know it's another post in quick succession, but I've been tinkering.
I decided I should try to get a LP filter in there somewhere. Then I noticed something handy. For my sub, I made an adjustable LP filter, ranging from 60Hz up to full range. So, using that (dunno what I set it to), I managed to re-enforce the lower midrange, and bass, without making too much higher mid (which doesn't need cancellation).
Sounds even better now. Even the most basic speakers can be made reasonable...
I'll find out what I set the filter to, (probably this evening, as I got school in 5 mins), and report back then.
Remembering that LP filter will definately push this project forwards. "To infinity, and beyond"
Chris
I decided I should try to get a LP filter in there somewhere. Then I noticed something handy. For my sub, I made an adjustable LP filter, ranging from 60Hz up to full range. So, using that (dunno what I set it to), I managed to re-enforce the lower midrange, and bass, without making too much higher mid (which doesn't need cancellation).
Sounds even better now. Even the most basic speakers can be made reasonable...
I'll find out what I set the filter to, (probably this evening, as I got school in 5 mins), and report back then.
Remembering that LP filter will definately push this project forwards. "To infinity, and beyond"
Chris
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