Greeting all,
Okay, I decided to rebuild an againg M&K Volkswoofer with new parts as the old ones were getting pretty tired. The new driver is a Dayton 12" DVC. The new amplifer is the Rythmik Audio 250SE (special edition).
The Dayton 12" DVC is a dual voice coil woofer being used in resistively damped operation (the second voice coil is being used as a brake to precisely adjust the Qts to my box). After some careful calculations and with the help of a Dumax report, 7.5ohms was calculated as the correct resistor to give me a Q=.707 Butterworth alignment in this sealed 50L (net) box. Heavy stuffing is used.
The subwoofer design on paper:
Driver: Dayton 12" DVC, resistively damped operation
Box: sealed, 50L (1.77cuft)
F3: 33Hz
Fc: 33Hz
F6: 26Hz
(Note: figures without room gain)
Amplifier: Rythmik Audio 250SE
The Rythmik Audio 250SE is basically a tweaked Parts Express amp. This amp has some upgraded wiring & caps, and a 24dB/octave lowpass filter in lieu of PE's 12dB/octave. The phase control has been redesigned to perform better. Hum has also been reduced.
How does it sound? Well, I've heard a bunch of subs and this is a good design, especially for music. I also tried it with home theater and it works impressively (getting the music right is the tough part, HT will follow naturally). The sub is deep and tight with an excellent balance between the boominess of a high Q and the tight (but thin sounding) bass of a low Q design. I tried Q=.6 and it was just to thin and dry sounding for my taste - it was tight , though. I also tried Q=.9 and it had a little too much boom and overhang for my taste. I have new respect for a Q=.707 Butterworth alignment. The bass has punch and hits hard like a live performance - impressive.
With a meter, I'm pretty flat down to about 30Hz, good output at 25Hz, falling fast at 20Hz (but still useful). At 1 meter, I got 100dB at 20Hz (pure tone) before hearing the Dayton DVC just starting to distort - it was quite impressive (and a little scary) to see the Dayton woofer working that hard under heavy excursion. BTW, even with one voice coil hooked up, this sub plays quite loud with serious room pounding bass.
The Rythmik Audio 250SE barely was warm to the touch after a serious workout. Hum is minimal, power is entirely adequate for this sub design, and the 24dB/octave is a very nice feature (the high frequencies are so attenuated that is difficult to tell what familiar song your listening to by just listening to the sub - it was quite easy with the old 12dB/octave M&K). The 24db filter also keeps power from the amp being wasted (robbed) on unwanted upper bass frequencies.
The phase control is a VERY USEFUL feature on this amp. I am running my mains full range and the room has a natural peak at 40Hz (which, incidentally, is also my crossover frequency). Using my meter, I actually used the phase control to create a little destructive interference to tame the 40Hz resonance of the room and smooth the crossover frequency.
With the phase control set in 100% in phase, it would have reinforced some nasty overhang which is intrinsic to my particular listening room, set 100% out of phase, it would create a void in the bass reponse. The best setting is somewhere in between. Its funny that my mains alone have more overhang without the sub due to room resonances. The sub is actually is functioning as a room bass trap to reinforce some frequencies and reduce others. The discovery of the usefulness of the phase control in taming room resonances was serendipity for me. With the overhang removed from my room the bass really hits with the cleaness and authority of a live performance. Impressive.
Note: Interestingly, the phase control seems to be backwards: 100% in phase when set on 180 degrees, not 0 degrees. Yes, I have everything wired up right in the cabinet and everywhere - its the amp. (My sub is facing the same direction as my mains and is located beside my right speaker). This is NO disadvantage or problem, just important to know.
In summary, this is a good design that has exceeded my expectations and easily bests the original M&K components in everyway (no offense M&K, that was a very good sub). I am impressed with the versatile Dayton 12" DVC and especially with the Rythmik Audio 250SE plate amp. Also, during this project it was driven home that mating the driver and the box are critical - slight changes in the tuning of the box make PROFOUND differences in the overall sound. A driver is only as good as its design. The "resistively damped operation" design is simple, but effective.
BTW, Rythmik Audio was informative and helpful with my choice of amplifiers. Thank you.
Regards,
Loudnclear
Okay, I decided to rebuild an againg M&K Volkswoofer with new parts as the old ones were getting pretty tired. The new driver is a Dayton 12" DVC. The new amplifer is the Rythmik Audio 250SE (special edition).
The Dayton 12" DVC is a dual voice coil woofer being used in resistively damped operation (the second voice coil is being used as a brake to precisely adjust the Qts to my box). After some careful calculations and with the help of a Dumax report, 7.5ohms was calculated as the correct resistor to give me a Q=.707 Butterworth alignment in this sealed 50L (net) box. Heavy stuffing is used.
The subwoofer design on paper:
Driver: Dayton 12" DVC, resistively damped operation
Box: sealed, 50L (1.77cuft)
F3: 33Hz
Fc: 33Hz
F6: 26Hz
(Note: figures without room gain)
Amplifier: Rythmik Audio 250SE
The Rythmik Audio 250SE is basically a tweaked Parts Express amp. This amp has some upgraded wiring & caps, and a 24dB/octave lowpass filter in lieu of PE's 12dB/octave. The phase control has been redesigned to perform better. Hum has also been reduced.
How does it sound? Well, I've heard a bunch of subs and this is a good design, especially for music. I also tried it with home theater and it works impressively (getting the music right is the tough part, HT will follow naturally). The sub is deep and tight with an excellent balance between the boominess of a high Q and the tight (but thin sounding) bass of a low Q design. I tried Q=.6 and it was just to thin and dry sounding for my taste - it was tight , though. I also tried Q=.9 and it had a little too much boom and overhang for my taste. I have new respect for a Q=.707 Butterworth alignment. The bass has punch and hits hard like a live performance - impressive.
With a meter, I'm pretty flat down to about 30Hz, good output at 25Hz, falling fast at 20Hz (but still useful). At 1 meter, I got 100dB at 20Hz (pure tone) before hearing the Dayton DVC just starting to distort - it was quite impressive (and a little scary) to see the Dayton woofer working that hard under heavy excursion. BTW, even with one voice coil hooked up, this sub plays quite loud with serious room pounding bass.
The Rythmik Audio 250SE barely was warm to the touch after a serious workout. Hum is minimal, power is entirely adequate for this sub design, and the 24dB/octave is a very nice feature (the high frequencies are so attenuated that is difficult to tell what familiar song your listening to by just listening to the sub - it was quite easy with the old 12dB/octave M&K). The 24db filter also keeps power from the amp being wasted (robbed) on unwanted upper bass frequencies.
The phase control is a VERY USEFUL feature on this amp. I am running my mains full range and the room has a natural peak at 40Hz (which, incidentally, is also my crossover frequency). Using my meter, I actually used the phase control to create a little destructive interference to tame the 40Hz resonance of the room and smooth the crossover frequency.
With the phase control set in 100% in phase, it would have reinforced some nasty overhang which is intrinsic to my particular listening room, set 100% out of phase, it would create a void in the bass reponse. The best setting is somewhere in between. Its funny that my mains alone have more overhang without the sub due to room resonances. The sub is actually is functioning as a room bass trap to reinforce some frequencies and reduce others. The discovery of the usefulness of the phase control in taming room resonances was serendipity for me. With the overhang removed from my room the bass really hits with the cleaness and authority of a live performance. Impressive.
Note: Interestingly, the phase control seems to be backwards: 100% in phase when set on 180 degrees, not 0 degrees. Yes, I have everything wired up right in the cabinet and everywhere - its the amp. (My sub is facing the same direction as my mains and is located beside my right speaker). This is NO disadvantage or problem, just important to know.
In summary, this is a good design that has exceeded my expectations and easily bests the original M&K components in everyway (no offense M&K, that was a very good sub). I am impressed with the versatile Dayton 12" DVC and especially with the Rythmik Audio 250SE plate amp. Also, during this project it was driven home that mating the driver and the box are critical - slight changes in the tuning of the box make PROFOUND differences in the overall sound. A driver is only as good as its design. The "resistively damped operation" design is simple, but effective.
BTW, Rythmik Audio was informative and helpful with my choice of amplifiers. Thank you.
Regards,
Loudnclear
Additional note: I was looking at an error correction chart for my Radio Shack digital SPL meter (el cheapo $50). The chart said to add 7.5dB @ 20Hz (add 5dB @ 25Hz). If the error correction is right, my sub hit 107.5 dB @ 20Hz at 1 meter (in room) before any audible distortion. These meters aren't too accurate I guess?
Loudnclear
Loudnclear
Member
Joined 2003
.
I'm using the high power 12" Dayton DVC - similar to the Shiva.
This sub is really sounding good. The bass is tight and full and is perfoming with my music in a most excellent way. Again, besting the M&K, easily.
Using 1 voice coil is giving me about a 10Hz lower F3 verses both coils in series (according to my BassBox software). With room gain and meter error accounted for, I'm pretty flat well into the 20's. I'm going to generate some more numbers this weekend - I'll post them.
Andy
This sub is really sounding good. The bass is tight and full and is perfoming with my music in a most excellent way. Again, besting the M&K, easily.
Using 1 voice coil is giving me about a 10Hz lower F3 verses both coils in series (according to my BassBox software). With room gain and meter error accounted for, I'm pretty flat well into the 20's. I'm going to generate some more numbers this weekend - I'll post them.
Andy
You're kidding! I just did....
....a very similar change-out-the-guts project with an old Acoustic Research sub box I got off eBay. I used the Dayton DVC with both coils in parallel, and the Rythmik 250A amp with the crossover point set for 24hz.
Mine is in a vented 41 liter box, with the 3" by 18.5 vent.
Tell us some more about using that resistor as a brake, and how that improves the whatever. And whether it would work in a vented box...?
....a very similar change-out-the-guts project with an old Acoustic Research sub box I got off eBay. I used the Dayton DVC with both coils in parallel, and the Rythmik 250A amp with the crossover point set for 24hz.
Mine is in a vented 41 liter box, with the 3" by 18.5 vent.
Tell us some more about using that resistor as a brake, and how that improves the whatever. And whether it would work in a vented box...?
I meant coils in parallel in my last thread not series (I did not model a series wiring of the voice coils).
Resistively damped operation is cool because you can use the second voice coil to act as a brake to ajust your Qts anywhere between the Qts of both coils in parallel (Qts=.37) and 1 wired voice coil (Qts=.71). I chose Qts=.51 for my design to give me an enclosure/driver realtionship of exactly Q=.707 (considered ideal balance of boom and tightness in a sealed enclosure - my ears do agree with this value). With Qts=.51 as my target, I calculated my damping resistor to have a value of 7.5 ohms.
You could use resistively damped operation for ported enclosures, but a Qts of .37 is pretty good for the ported design. Also, you could only go higher than .37, not lower.
Andy
Resistively damped operation is cool because you can use the second voice coil to act as a brake to ajust your Qts anywhere between the Qts of both coils in parallel (Qts=.37) and 1 wired voice coil (Qts=.71). I chose Qts=.51 for my design to give me an enclosure/driver realtionship of exactly Q=.707 (considered ideal balance of boom and tightness in a sealed enclosure - my ears do agree with this value). With Qts=.51 as my target, I calculated my damping resistor to have a value of 7.5 ohms.
You could use resistively damped operation for ported enclosures, but a Qts of .37 is pretty good for the ported design. Also, you could only go higher than .37, not lower.
Andy
Okay, I just got finished generating some test tones and measuring them with a meter.
In my listening room (medium size), relative to 80Hz, this sub is:
-1dB @ 50Hz
+1.5dB @ 31.5Hz
+.5dB @ 25Hz
-6dB @ 20Hz.
Max ouput at 20Hz (before audible distortion) is 107.5dB @ 1m.
Note: NO bass boost is being used.
Reasonable for a sealed 12"?
In my listening room (medium size), relative to 80Hz, this sub is:
-1dB @ 50Hz
+1.5dB @ 31.5Hz
+.5dB @ 25Hz
-6dB @ 20Hz.
Max ouput at 20Hz (before audible distortion) is 107.5dB @ 1m.
Note: NO bass boost is being used.
Reasonable for a sealed 12"?
The last numbers were from my listening spot. These are from an up close microphone.
Relative to 80Hz:
63Hz = +1.5dB
50Hz = +1.5dB
40Hz = -1dB
31.5Hz = -1.5dB
25Hz = -6.5dB
20Hz = -8dB
With room gain these numbers obviously look better. My sub is located between the front speakers - it is not corner loaded. I'll have to try that too.
Relative to 80Hz:
63Hz = +1.5dB
50Hz = +1.5dB
40Hz = -1dB
31.5Hz = -1.5dB
25Hz = -6.5dB
20Hz = -8dB
With room gain these numbers obviously look better. My sub is located between the front speakers - it is not corner loaded. I'll have to try that too.
You know, I've been doing this speaker calc stuff for about two seeks now. I'm a technical person, but all this is like brand freakin' new to me.
I'm taking away that I should probably leave both voice coils connected in my vented box... right? My amp runs a little warmer than I'd really prefer, but then again I'm playing it louder than my poor wife would really prefer, too....
I'm taking away that I should probably leave both voice coils connected in my vented box... right? My amp runs a little warmer than I'd really prefer, but then again I'm playing it louder than my poor wife would really prefer, too....
Okay DrBoyd, I ran some numbers on your 41L (1.45cuft) vented design using BassBox software. A Dumax report was used for the T/S parameters on the Dayton 12" DVC subwoofer.
Your current 41L vented design:
Vb=1.45cuft
Fb=24hz
F3=28.9hz
Dv=3"
Lv=18.5"
Fill=normal
The curve on this design looks smooth with steep roll-off below F3. Nice curve.
-------------------------------------------------
Your design using 1 voice coil (second coil left open):
Vb=1.45cuft
Fb=24Hz
F3=28.9Hz
Dv=3"
Lv=18.5"
Fill=normal
Looks good right? Wrong!!!
Your design using just 1 voice coil looks much the same numbers wise, but has a very ragged, undesirable frequency response curve that has a huge peak above F3 and a big dip below it. Can you say "boomy"? No matter what vented design I used with your 41L box, I could not improve over your design using 1 voice coil and resistively damped operation. This response curve is so ugly, it could be a modern art masterpiece.
--------------------------------
A 41L Sealed Box targeting Qtc=.707 by resistively damped operation:
Vb=1.45cuft
Fb=36.4Hz
F3=36.4Hz
Qtc=.707
Fill=Heavy
(Target Qes for resitively damped operation: Qes=.517)*
(Target Qts for resistively damped operation: Qts=.48)*
*Both of these number go together, try plugging one or both into a bassbox program
Value of the damping resistor across the second coil: Unknown (but I could calculate it if you really want it).
This curve is quite smooth with shallow roll-off below F3. Nice curve. With room gain, I'll bet this would be quite flat down deep. HOWEVER, this curve is about 6dB less sensitive than your current vented design. Looks quite good for musical accuracy, but may or may not meet your needs for HT. BTW, this design should be an easy load on your amp for less heat.
------------------------------------------------------
Conclusion: for your 41L box, the vented design looks pretty good. If you discover your needs lean towards a sealed design, then resistively damped operation will be your Huckleberry.
Best regards,
Andy
Your current 41L vented design:
Vb=1.45cuft
Fb=24hz
F3=28.9hz
Dv=3"
Lv=18.5"
Fill=normal
The curve on this design looks smooth with steep roll-off below F3. Nice curve.
-------------------------------------------------
Your design using 1 voice coil (second coil left open):
Vb=1.45cuft
Fb=24Hz
F3=28.9Hz
Dv=3"
Lv=18.5"
Fill=normal
Looks good right? Wrong!!!
Your design using just 1 voice coil looks much the same numbers wise, but has a very ragged, undesirable frequency response curve that has a huge peak above F3 and a big dip below it. Can you say "boomy"? No matter what vented design I used with your 41L box, I could not improve over your design using 1 voice coil and resistively damped operation. This response curve is so ugly, it could be a modern art masterpiece.
--------------------------------
A 41L Sealed Box targeting Qtc=.707 by resistively damped operation:
Vb=1.45cuft
Fb=36.4Hz
F3=36.4Hz
Qtc=.707
Fill=Heavy
(Target Qes for resitively damped operation: Qes=.517)*
(Target Qts for resistively damped operation: Qts=.48)*
*Both of these number go together, try plugging one or both into a bassbox program
Value of the damping resistor across the second coil: Unknown (but I could calculate it if you really want it).
This curve is quite smooth with shallow roll-off below F3. Nice curve. With room gain, I'll bet this would be quite flat down deep. HOWEVER, this curve is about 6dB less sensitive than your current vented design. Looks quite good for musical accuracy, but may or may not meet your needs for HT. BTW, this design should be an easy load on your amp for less heat.
------------------------------------------------------
Conclusion: for your 41L box, the vented design looks pretty good. If you discover your needs lean towards a sealed design, then resistively damped operation will be your Huckleberry.
Best regards,
Andy
Andy, thanks for looking at it! This is my first subwoofer, and I've gotta tell you - I'm just tickled pink with it. My intention was just to piece somthing inexpensive together for about a year, at whch time my situation will change to where I'm planning to get an SVS.
But I'm very impressed with how this one turned out. Between the advice on this forum and the PE forum, quite a bit of dumb luck, and the help of WinISD, I've got something that's making me drag out my old disks and actually hear the bass track for the first time! I was anticipating that the ported design would be boomy, but I don't hear that in it at all. I'd call it solid and flat.
My main amp is a re-capped Magnavox tube type with (4) 6V6's in PP, and it does an excellent job on the vocals and high end. Main speakers are JBL L-100's. Although the JBL's are supposed to reach 27 Hz, this sub really adds the bass dimension.
Lessons learned:
A $19.95 roto-zip from Harbor Freight makes a great trim router for expanding the speaker mounting base.
An RV store will sell you some great putty tape for speaker and amp mounting.
3" abs drain pipe makes a great port.
Left-over generic tar-rubber auto sound dampening sheets do pretty well on sub-woofer panels.
Don
But I'm very impressed with how this one turned out. Between the advice on this forum and the PE forum, quite a bit of dumb luck, and the help of WinISD, I've got something that's making me drag out my old disks and actually hear the bass track for the first time! I was anticipating that the ported design would be boomy, but I don't hear that in it at all. I'd call it solid and flat.
My main amp is a re-capped Magnavox tube type with (4) 6V6's in PP, and it does an excellent job on the vocals and high end. Main speakers are JBL L-100's. Although the JBL's are supposed to reach 27 Hz, this sub really adds the bass dimension.
Lessons learned:
A $19.95 roto-zip from Harbor Freight makes a great trim router for expanding the speaker mounting base.
An RV store will sell you some great putty tape for speaker and amp mounting.
3" abs drain pipe makes a great port.
Left-over generic tar-rubber auto sound dampening sheets do pretty well on sub-woofer panels.
Don
Drboyd, here's some more number for you.
Both Dayton DVC voice coils in parallel, sealed enclosure, Q=.707:
Vc=.811cuft
Fc=46.4Hz
F3=46.4Hz
Qtc=.707
Fill=normal
This sub will not go very low, even with room gain.
------------------------------------------------
Both voice coils in parallel, 41L (1.45cuft) sealed enclosure:
Vc=41L (1.45cuft)
Fc=37.5Hz
F3=47.3Hz
Qtc=.580
Fill=normal
This sub will not go low and will sound a little anemic with Q=.58
-------------------------------------------------
My design, 50L (1.77cuft), sealed, resistively damped oper*:
Vc=1.77cuft
Fc=34.1Hz
F3=34.2Hz
Qtc=.707
Fill=heavy
*1 voice coil with a 7.5ohm resistor across terminals, 1 voice coil to the amp
This is a good sealed design with good performance. Slow roll off gives good room gain numbers.
---------------------------------------------------
Conclusion:
1)The Dayton 12" DVC subwoofer likes to be in ported enclosure when both voice coils are parallelled, and conversely does not particularly like the sealed enclosure.
2) With one voice coil hooked up, the driver is begging to be in a sealed enclosure and can be precisely tuned to the box using resistively damped operation. (1 voice coil with NO RESISTOR looks good in an infinite baffle design). 1 voice coil operation does not like the ported enclosure giving a poor response curve.
3) The Dayton DVC 12" subwoofer is a versitile driver.
-------------------------------------------------
Best regards,
Andy
Both Dayton DVC voice coils in parallel, sealed enclosure, Q=.707:
Vc=.811cuft
Fc=46.4Hz
F3=46.4Hz
Qtc=.707
Fill=normal
This sub will not go very low, even with room gain.
------------------------------------------------
Both voice coils in parallel, 41L (1.45cuft) sealed enclosure:
Vc=41L (1.45cuft)
Fc=37.5Hz
F3=47.3Hz
Qtc=.580
Fill=normal
This sub will not go low and will sound a little anemic with Q=.58
-------------------------------------------------
My design, 50L (1.77cuft), sealed, resistively damped oper*:
Vc=1.77cuft
Fc=34.1Hz
F3=34.2Hz
Qtc=.707
Fill=heavy
*1 voice coil with a 7.5ohm resistor across terminals, 1 voice coil to the amp
This is a good sealed design with good performance. Slow roll off gives good room gain numbers.
---------------------------------------------------
Conclusion:
1)The Dayton 12" DVC subwoofer likes to be in ported enclosure when both voice coils are parallelled, and conversely does not particularly like the sealed enclosure.
2) With one voice coil hooked up, the driver is begging to be in a sealed enclosure and can be precisely tuned to the box using resistively damped operation. (1 voice coil with NO RESISTOR looks good in an infinite baffle design). 1 voice coil operation does not like the ported enclosure giving a poor response curve.
3) The Dayton DVC 12" subwoofer is a versitile driver.
-------------------------------------------------
Best regards,
Andy
Here's some numbers with only 1 voice coil wired up with no damping resistor. Looks pretty good for an infinite baffle design. (I'll bet Dayton's 15" IB woofer is basically a 15" DVC with only 1 voice coil.) These numbers are for the 12" DVC, 1 coil wired:
Vc=9.68cuft
Fc=24.3Hz
F3=24.3Hz
Qtc=.707
Fill=normal
-------------------------
Vc=infinite
Fc=21.3Hz
F3=24.1
Qtc=.633
Fill=minimal
-------------------------
This is a nice, versatile woofer. Anybody out there use the Dayton DVC woofer in an infinite baffle application?
Warm regards,
Andy
Vc=9.68cuft
Fc=24.3Hz
F3=24.3Hz
Qtc=.707
Fill=normal
-------------------------
Vc=infinite
Fc=21.3Hz
F3=24.1
Qtc=.633
Fill=minimal
-------------------------
This is a nice, versatile woofer. Anybody out there use the Dayton DVC woofer in an infinite baffle application?
Warm regards,
Andy
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