Both listening tests and frequency response testing have revealed that the baffle step correction is not enough - the upper mid-range is still too hot - so I have some new inductors on order from Madisound to correct the problem. I should be performing some additional testing/tweaking this weekend. Call me a perfectionist if you want, but I hope to have this project completed by early next week.
Andrew
Andrew
Cant' wait for your result Andy.
You may have your reasons or best compromising choice crossing
at 5K.But from the published Adire specs, (which may differ to
your actual on baffle measured) its clear that the midrange 30 degrees roll off starts to occur at approx. 3.2K and its quite sharp.
I hope those tweets do help improving those areas.
And if you do put your results here, also do show the of-axis response as well.
You may have your reasons or best compromising choice crossing
at 5K.But from the published Adire specs, (which may differ to
your actual on baffle measured) its clear that the midrange 30 degrees roll off starts to occur at approx. 3.2K and its quite sharp.
I hope those tweets do help improving those areas.
And if you do put your results here, also do show the of-axis response as well.
Irwin:
I will do my best to post the off-axis response. Although I have been modeling the response for on-axis response, I can share two points with you:
1. I measured both the tweeter and the woofer response while the drivers were mounted to the baffle in their final positions and I position the mic mid-way between the tweeter and the woofer. I then measured each driver's response. Given the fact that the mic was not directly on axis with the driver, I believe that I've already compensated for off-axis response to some extent.
2. The frequency response I obtained from the WR125S was different than what the published specs show. What I mean is that dips shown in the published response curves show in my testing too, but much more dramatically. I believe this is partly the result of smoothing of the published curves as well as alterred response when mounted on the baffle of the Parts Express .25 cu ft box.
One thing to keep in mind are some of the design goals of this project. It was my desire to get as much of the mid-range as possible from a single driver to avoid to the greatest extent possible a muddying of the very clean mid-range provided by the WR125S. By crossing around 5K I not only acheive that goal, but I am also able to smooth out some of the WR125S response anomalies I've observed above that frequency.
I received my new inductors today and I am currently testing the new values.
Regards,
Andrew
I will do my best to post the off-axis response. Although I have been modeling the response for on-axis response, I can share two points with you:
1. I measured both the tweeter and the woofer response while the drivers were mounted to the baffle in their final positions and I position the mic mid-way between the tweeter and the woofer. I then measured each driver's response. Given the fact that the mic was not directly on axis with the driver, I believe that I've already compensated for off-axis response to some extent.
2. The frequency response I obtained from the WR125S was different than what the published specs show. What I mean is that dips shown in the published response curves show in my testing too, but much more dramatically. I believe this is partly the result of smoothing of the published curves as well as alterred response when mounted on the baffle of the Parts Express .25 cu ft box.
One thing to keep in mind are some of the design goals of this project. It was my desire to get as much of the mid-range as possible from a single driver to avoid to the greatest extent possible a muddying of the very clean mid-range provided by the WR125S. By crossing around 5K I not only acheive that goal, but I am also able to smooth out some of the WR125S response anomalies I've observed above that frequency.
I received my new inductors today and I am currently testing the new values.
Regards,
Andrew
Frequency Response Curve
Folks:
Here is something for you to finally sink your teeth into. I have attached a .zip file with a .ppt slide showing an image of my frequency response test results in SpeakerWorkshop for the WR125S/DX19 combo in the Parts Express .25 cubic foot enclosure.
A few comments about the results:
1. Please ignore the "levels" shown on the graph as I did not calibrate the setup to measure SPL correctly, however all the measurements were taken using a Panasonic WM60AT microphone, a calibrated Wallin jig, and at 1 meter distance regardless of the testing angle.
2. The test results were repeatable (scientific method).
3. The accuracy of the tests below around 200hz is questionable due to the "gating" methodology I employed in the x-over.
4. The dip in response around 10K is inherent in the tweeter and is not readily noticable nor is there much I could do about this without employing a high frequency notch filter on the tweeter which I did not wish to do.
5. The tweeter output level is easily adjustable by swapping out a resistor in the L-PAD of the crossover. Even though the tweeter response "looks" low, it actually sounds a little better this way in my opinion. When I publish the x-over design, I will include some options for this adjustment.
6. I am performing final tweaking to the baffle step correction through a combination of listening tests and frequency response measurements so the midrange curves might change slightly as the design is finalized.
There will be more to come soon!
Andrew
Folks:
Here is something for you to finally sink your teeth into. I have attached a .zip file with a .ppt slide showing an image of my frequency response test results in SpeakerWorkshop for the WR125S/DX19 combo in the Parts Express .25 cubic foot enclosure.
A few comments about the results:
1. Please ignore the "levels" shown on the graph as I did not calibrate the setup to measure SPL correctly, however all the measurements were taken using a Panasonic WM60AT microphone, a calibrated Wallin jig, and at 1 meter distance regardless of the testing angle.
2. The test results were repeatable (scientific method).
3. The accuracy of the tests below around 200hz is questionable due to the "gating" methodology I employed in the x-over.
4. The dip in response around 10K is inherent in the tweeter and is not readily noticable nor is there much I could do about this without employing a high frequency notch filter on the tweeter which I did not wish to do.
5. The tweeter output level is easily adjustable by swapping out a resistor in the L-PAD of the crossover. Even though the tweeter response "looks" low, it actually sounds a little better this way in my opinion. When I publish the x-over design, I will include some options for this adjustment.
6. I am performing final tweaking to the baffle step correction through a combination of listening tests and frequency response measurements so the midrange curves might change slightly as the design is finalized.
There will be more to come soon!
Andrew
looks great Andrew !
How much attenuation did you apply to the tweet?
Did you use a standard Lpad arrangement?
I have some adjustable L pads that I might try at first, if these won't mess up the crossover function.
By the way, what are the dimensions on the baffle ?
I am starting to build me boxes. I had planned to put some large radius on them, but it doesn't look like you had too bad a result with the off- the -shelf boxes which I assume just have square edges?
JM
How much attenuation did you apply to the tweet?
Did you use a standard Lpad arrangement?
I have some adjustable L pads that I might try at first, if these won't mess up the crossover function.
By the way, what are the dimensions on the baffle ?
I am starting to build me boxes. I had planned to put some large radius on them, but it doesn't look like you had too bad a result with the off- the -shelf boxes which I assume just have square edges?
JM
The tweeters required quite a bit of attenuation. I'm using 3 ohms (actually two Mills 6 ohms non-inductive in parallel) in-line and a 1 ohm (a single Dayton non-inductive resistor) to ground for the fixed L-PAD. The value of the 1 ohm resistor might change slightly as I finalize the design. The tweeter is MUCH more efficient than the woofer.
You should check out the Parts Express .25 cubic foot boxes (www.partsexpress.com) they are nicely built and not too expensive - I was surprised at how good the quality was when I first received them. I am using them with a 6 inch long and 2" diamerter port positioned behind the tweeter and mounted to the rear of the enclosure. The boxes do have rounded edges on the baffle.
You should check out the Parts Express .25 cubic foot boxes (www.partsexpress.com) they are nicely built and not too expensive - I was surprised at how good the quality was when I first received them. I am using them with a 6 inch long and 2" diamerter port positioned behind the tweeter and mounted to the rear of the enclosure. The boxes do have rounded edges on the baffle.
Baffle Layout
Folks:
Please find attached the baffle layout I used for my speaker design. I have also included a summary of some of the measurements I used for the baffle routering below. Please take the extra time to confirm that the numbers below are accurate before you cut - I haven't looked at these since January and I might have errors which I corrected on the fly while I was doing the work . . .
All values in inches:
woofer recess ring diameter 6
woofer recess ring depth 3/16
woofer cut out width 3 13/16
woofer center from bottom 3 3/4
tweeter cut out width 2 1/2
tweeter y value from top 3 3/8
tweeter x value from side 4 1/2"
tweeter recess ring diameter 3 3/4
tweeter recess ring depth 3/16
port recess ring diameter 3 3/16
port ring depth 1/8
port cut out 2 3/8
port center from top 2 1/2
I will be posting x-over schematics and related notes next.
Andrew
Folks:
Please find attached the baffle layout I used for my speaker design. I have also included a summary of some of the measurements I used for the baffle routering below. Please take the extra time to confirm that the numbers below are accurate before you cut - I haven't looked at these since January and I might have errors which I corrected on the fly while I was doing the work . . .
All values in inches:
woofer recess ring diameter 6
woofer recess ring depth 3/16
woofer cut out width 3 13/16
woofer center from bottom 3 3/4
tweeter cut out width 2 1/2
tweeter y value from top 3 3/8
tweeter x value from side 4 1/2"
tweeter recess ring diameter 3 3/4
tweeter recess ring depth 3/16
port recess ring diameter 3 3/16
port ring depth 1/8
port cut out 2 3/8
port center from top 2 1/2
I will be posting x-over schematics and related notes next.
Andrew
Final X-Over
Folks:
Here is the final x-over schematic attached for download, a parts list and some of my notes:
Please note that the design is subject to change and no guarantees of performance are provided.
1. The design does not include impedance compensation circuitry.
2. My testing of the 2.0mH inductors show that their values were about 7% too high. I manually unwound these inductors by hand exactly 8 turns. This brought the measured value down to 2.0 from about 2.17. The degree to which these speakers sound "mid-forward" is controlled by the value of this inductor. If you wish to play with the woofer x-over you may try unwinding the 2.0 mH more than 8 turns or you could just try a 1.8 mH. I have tried both and the speakers sound very good but brighter with the 1.8 mH. With the unwound 2.0mH they sound a little more "darK" with a more pronounced mid-bass but are a little easier to listen to overall. The value of this inductor is used to control the baffle step as well as helps to define the 2nd order low pass x-over for the woofer. The change from 2.0 to 1.8 mostly impacts the baffle step correction. I have found that with different electronics either the 1.8 or 2.0 might sound better. Running off my Denon receiver directly I prefer the 1.8 but running the Denon pre to my Dynaco ST-400 amp I prefer the 2.0 as the Dynaco (with a full rebuild and my modifications) is brighter in the midrange than the Denon on its own.
For Home Theatre I would recommend going a little brighter and opting for the 1.8mH inductors. For music the choice is yours.
3. The 1 ohm inductors in the tweeter L-PAD can be swapped out to make the tweeter brighter or more laid back. Differences of 1/10 ohm are noticable. If you wish to calculate additional values, you may do so easily with this on-line tool:
http://www.1728.com/resistrs.htm
To get the tweeter brighter try a value of 1.1. To bring the level down try .9 ohms.
For reference, 1.1 can be obtained by running a 2.0 and 2.4 in parallel. A .9 can be obtained by running a 1.5 and a 2.4 in parallel. These values are all available in the Dayton non-inductive line from PE . . .
4. Although the system is using 2nd order x-overs, be sure to wire the tweeter and woofer with the same polarities (not inverted on the tweeter). This eliminates a null which is formed from the inverse wiring configuration in the farfield measurement.
5. Pack the enclosure heavily with fiberfill directly behind the woofer in both the front and rear parts of the lower half of the enclosure.
6. Build your x-over on the fiberboard strips and mount them in the middle of the enclosure to the cross brace using zip ties and put some fiberfill between the x-over and the cross brace to eliminate noise/vibrations. Drill holes in the fiberboard to define mounting locations. Be sure to mount your inductors perpendicular to one another and rotated 90 degrees to reduce magnetic interference between them.
7. Be sure to make your baffle cut-outs as mirror images of each other.
8. Parts needed:
Madisound:
2 x 2.0 mH Solen Sidewinder 16 GA inductor
2 x .1 mH Solen Sidewinder 16 GA inductor
2 x Solen 2.5uF capacitors (or substitute your favorite type - for tweeter and in-line)
2 x Solen 4.7uF capacitors (or substitute your favorite type)
Parts Express:
Pair of .25 cu ft enclosures
2 x 3 ohm non-inductive resistor (go high quality on this one - for tweeter - I use 2 x 6 ohm Mills in parallel for each x-over).
2 x 1.0 ohm non-inductive resistors (I used the Dayton non-inductive resistor from Parts Express)
2" Adjustable length port tube PE part #260-387 (just use primary part of the tube factory cut to 6" length)
2 x Pair of Dayton model #BPA-38G speaker binding posts PE part #091-1245
Additional:
16 Gauge wire
2 strips of 3"x5"x.25" fiberboard
zip ties
crimp spade connectors
poly-fill
mounting screws and matching t-nuts for woofers
wood screws for mounting tweeters
Enjoy them!
Andrew
Folks:
Here is the final x-over schematic attached for download, a parts list and some of my notes:
Please note that the design is subject to change and no guarantees of performance are provided.
1. The design does not include impedance compensation circuitry.
2. My testing of the 2.0mH inductors show that their values were about 7% too high. I manually unwound these inductors by hand exactly 8 turns. This brought the measured value down to 2.0 from about 2.17. The degree to which these speakers sound "mid-forward" is controlled by the value of this inductor. If you wish to play with the woofer x-over you may try unwinding the 2.0 mH more than 8 turns or you could just try a 1.8 mH. I have tried both and the speakers sound very good but brighter with the 1.8 mH. With the unwound 2.0mH they sound a little more "darK" with a more pronounced mid-bass but are a little easier to listen to overall. The value of this inductor is used to control the baffle step as well as helps to define the 2nd order low pass x-over for the woofer. The change from 2.0 to 1.8 mostly impacts the baffle step correction. I have found that with different electronics either the 1.8 or 2.0 might sound better. Running off my Denon receiver directly I prefer the 1.8 but running the Denon pre to my Dynaco ST-400 amp I prefer the 2.0 as the Dynaco (with a full rebuild and my modifications) is brighter in the midrange than the Denon on its own.
For Home Theatre I would recommend going a little brighter and opting for the 1.8mH inductors. For music the choice is yours.
3. The 1 ohm inductors in the tweeter L-PAD can be swapped out to make the tweeter brighter or more laid back. Differences of 1/10 ohm are noticable. If you wish to calculate additional values, you may do so easily with this on-line tool:
http://www.1728.com/resistrs.htm
To get the tweeter brighter try a value of 1.1. To bring the level down try .9 ohms.
For reference, 1.1 can be obtained by running a 2.0 and 2.4 in parallel. A .9 can be obtained by running a 1.5 and a 2.4 in parallel. These values are all available in the Dayton non-inductive line from PE . . .
4. Although the system is using 2nd order x-overs, be sure to wire the tweeter and woofer with the same polarities (not inverted on the tweeter). This eliminates a null which is formed from the inverse wiring configuration in the farfield measurement.
5. Pack the enclosure heavily with fiberfill directly behind the woofer in both the front and rear parts of the lower half of the enclosure.
6. Build your x-over on the fiberboard strips and mount them in the middle of the enclosure to the cross brace using zip ties and put some fiberfill between the x-over and the cross brace to eliminate noise/vibrations. Drill holes in the fiberboard to define mounting locations. Be sure to mount your inductors perpendicular to one another and rotated 90 degrees to reduce magnetic interference between them.
7. Be sure to make your baffle cut-outs as mirror images of each other.
8. Parts needed:
Madisound:
2 x 2.0 mH Solen Sidewinder 16 GA inductor
2 x .1 mH Solen Sidewinder 16 GA inductor
2 x Solen 2.5uF capacitors (or substitute your favorite type - for tweeter and in-line)
2 x Solen 4.7uF capacitors (or substitute your favorite type)
Parts Express:
Pair of .25 cu ft enclosures
2 x 3 ohm non-inductive resistor (go high quality on this one - for tweeter - I use 2 x 6 ohm Mills in parallel for each x-over).
2 x 1.0 ohm non-inductive resistors (I used the Dayton non-inductive resistor from Parts Express)
2" Adjustable length port tube PE part #260-387 (just use primary part of the tube factory cut to 6" length)
2 x Pair of Dayton model #BPA-38G speaker binding posts PE part #091-1245
Additional:
16 Gauge wire
2 strips of 3"x5"x.25" fiberboard
zip ties
crimp spade connectors
poly-fill
mounting screws and matching t-nuts for woofers
wood screws for mounting tweeters
Enjoy them!
Andrew
Attachments
Yes, I do have an overall impedance curve. The crossover itself impacts the impedance dramatically. I can also post the individual driver impedance curves if you are interested in those as well, just let me know.
I am traveling today through Friday on business, but I will try to post the curve for you over the weekend.
Generally speaking I think the concern has to do with making sure the impedance doesn't go so low that the load is hard for an amplifier to drive. The good thing about the impedance I measured is that it is not too low and therefore should be okay for amplifiers to drive the speaker without any problem. Off hand I can't remember the lowest point but I will share the curve with everyone once I'm back home.
Regards,
Andrew
I am traveling today through Friday on business, but I will try to post the curve for you over the weekend.
Generally speaking I think the concern has to do with making sure the impedance doesn't go so low that the load is hard for an amplifier to drive. The good thing about the impedance I measured is that it is not too low and therefore should be okay for amplifiers to drive the speaker without any problem. Off hand I can't remember the lowest point but I will share the curve with everyone once I'm back home.
Regards,
Andrew
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