I have recently traded my SUV in for a passat TDI (50mpg!). I was using 2 DC sounds 15" XL subwoofers in a box in my suv. Which means I have 2 monster 15" drivers to play with. They have a QTS of .306, 1500+ watts RMS rating and 26mm xmax. They seem to play well with TH. I built a SS15 and love its size and output but like many these day's my audience is starting to love dubstep, trapstep, etc with 30-40hz content. I have been playing around with the different design concepts such as modifying the SS15 and Xoc1's TH-18 and a few others but honestly I'm just not that good at translating what I can come up with in hornresp into a box without wasting a ton of room folding.
So here's the challenge for all the guru's or anyone else that would like to try.
1. 2 boxes that have a -3db at 30hz 2pi.
2. Must be built using a single sheet of plywood. You can cheat by buying one piece of 2x4 MDF or plywood available at every home depot. I add this so you can cheat a little as that seemed to limit some designs in the original thread.
3. Most SPL in 30-100hz
I think this design will answer many people's questions about exactly how much output you are giving up when you are forced to reproduce 30-40hz. Once we have a winning design and a cutsheet and build sheet posted for everyone I will build these and compare one of them to my SS15 and post real world results as far as output differences.
Below are the specs for the DC audio 15's
SD 791 CMS1.17E-04 MMD 158.02 RE3.6
BL 20.73 RMS 5.47 LE 4.
These parameters have been corrected per the manufacturers input. Thank you to all that pointed out that the original specs were incorrect!
So here's the challenge for all the guru's or anyone else that would like to try.
1. 2 boxes that have a -3db at 30hz 2pi.
2. Must be built using a single sheet of plywood. You can cheat by buying one piece of 2x4 MDF or plywood available at every home depot. I add this so you can cheat a little as that seemed to limit some designs in the original thread.
3. Most SPL in 30-100hz
I think this design will answer many people's questions about exactly how much output you are giving up when you are forced to reproduce 30-40hz. Once we have a winning design and a cutsheet and build sheet posted for everyone I will build these and compare one of them to my SS15 and post real world results as far as output differences.
Below are the specs for the DC audio 15's
SD 791 CMS1.17E-04 MMD 158.02 RE3.6
BL 20.73 RMS 5.47 LE 4.
These parameters have been corrected per the manufacturers input. Thank you to all that pointed out that the original specs were incorrect!
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That MMD is way off, should be nearer to 300g...
Combined with the high Qe it's unlikely to work well in a tapped horn, especially if you want high SPL :-(
(there are much more suitable pro drivers to get you down to 30Hz with high SPL)
Here is the SS15 with my driver at 100v. This is the limit of what my behringer ep4000 can provide. Currently running 2 ohm stereo and hit roughly 95-100 volts at the limiter.
An externally hosted image should be here but it was not working when we last tested it.
There's no way a car audio 15" speaker would have an Mmd of 98.86 grams. That's lighter than a few PRO audio 15s that I know. Re-check your input information.
The data sheet for the current drivers (same Xmax, higher Pe) says Qes=0.516 -- and this is with higher (BL^2/Re) than the older driver quoted, so I'd expect that to have even higher Qes.
Quoted spec : SD 791 CMS1.79e-04 MMD 98.86 RE3.6 BL 16.76 RMS 3.58 LE 4.02 XMAX 26mm Qe 0.306
Current spec : SD 791 CMS7e-05 MMS 307 RE4.0 BL 22.7 RMS 3.58 LE 5.2 XMAX 26mm Qe 0.516
The reference SPL is about 6dB lower than drivers like the BMS15N850V2, so I'd expect the efficiency (and maximum SPL) in a tapped horn to also be about 6dB lower -- not a good recipe for high SPL, Mmd is far too high. Also the massive (and probably nonlinear) Le means it would probably be struggling badly by 100Hz...
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The T/S specs I have were taken off of DC's site when this driver was still available. They have since upgraded to a new model with different specs. I am new at this but it doesn't seem that these designs are super sensitive to what driver you put in them as long as it has a low qts. I have put an AV123 MFW-15 driver in my SS15 and it worked pretty well too. Didn't go as loud as the DC driver but that's to be expected as it has half the excursion and only 250 watts of power handling.
Specs that I have written down from when I built the box in my suv are as follows.
SD 791
FS 35.6
QMS 6.98
QES .32
QTS .30
XMAX 26mm
Sensitivity 93.7
RE 3.6 (Listed as dual 2 ohm coils, my MM measures them as 1.8)
Everything else I have either guessed at or extrapolated using winisd or hornresp. I am admittedly no expert so if you think one of my specs for hornresp is wrong please let me know. If needed I may buy a DATS tester from parts express and test them to be exact.
Specs that I have written down from when I built the box in my suv are as follows.
SD 791
FS 35.6
QMS 6.98
QES .32
QTS .30
XMAX 26mm
Sensitivity 93.7
RE 3.6 (Listed as dual 2 ohm coils, my MM measures them as 1.8)
Everything else I have either guessed at or extrapolated using winisd or hornresp. I am admittedly no expert so if you think one of my specs for hornresp is wrong please let me know. If needed I may buy a DATS tester from parts express and test them to be exact.
I'm fairly sure that those numbers (with the coil size/weight needed for 26mm Xmax) are unrealistic for a 15" driver -- car audio firms aren't always noted for providing accurate T-S parameters, though the new ones look more likely to be correct (but unsuitable for a high SPL tapped horn).
The quoted Xmax could be a p-p figure.
To be realistic, I've only come across one car audio manufacturer in the last few years that quoted specs for their drivers that were grossly out of line with what I measured. I'm not familiar with the "DC Sounds" brand though.
So I called DC Audio and asked them if they had the full T/S specs for this driver. The following is what they gave me and when I pressed for details, I was told these are the specs that they have in their computer to use when designing boxes for this driver.
QES .32
QMS 6.98
QTS .306
FS 35.6
VAS 104.11
MMS 170.4
CMS .1173
RMS 5.460
RE 3.6 (series)
BL 20.707
DD 31.74
SD 791
XMAX 26mm
When entering these specs in hornresp and winisd and bassbox they all seemed to add up. When the programs would auto calculate using known data it all cross checked fine.
They did not have the data for LE. I am checking around for any spare resistors and am going to go measure this right now.
QES .32
QMS 6.98
QTS .306
FS 35.6
VAS 104.11
MMS 170.4
CMS .1173
RMS 5.460
RE 3.6 (series)
BL 20.707
DD 31.74
SD 791
XMAX 26mm
When entering these specs in hornresp and winisd and bassbox they all seemed to add up. When the programs would auto calculate using known data it all cross checked fine.
They did not have the data for LE. I am checking around for any spare resistors and am going to go measure this right now.
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Just to clarify, the company name is DC Audio and the website is DC Audio - Home.
I can help with this effort, as I know Rusty (the owner of DC Audio) and have a pair of DC XL m2 18's I'll soon be using in a home theater application.
The 26 mm Xmax number is correct. These units use a triple stack of 220 mm x 20 mm magnets and a very long 8 layer aluminum flatwire coil.
T/S parameters are shown here:
DC Audio - XL
Please note that this is for the XL m2. The previous version was slightly different, using a standard pole vent, where the new version uses a solid pole piece with 6 gap vents machined in channels down the pole piece and through the backplate. As such, the BL is slightly higher and program power handling has increased.
I can help with this effort, as I know Rusty (the owner of DC Audio) and have a pair of DC XL m2 18's I'll soon be using in a home theater application.
The 26 mm Xmax number is correct. These units use a triple stack of 220 mm x 20 mm magnets and a very long 8 layer aluminum flatwire coil.
T/S parameters are shown here:
DC Audio - XL
Please note that this is for the XL m2. The previous version was slightly different, using a standard pole vent, where the new version uses a solid pole piece with 6 gap vents machined in channels down the pole piece and through the backplate. As such, the BL is slightly higher and program power handling has increased.
The LE is somewhere very close to 4. The only resistor I had laying around was an old one from an amplifier repair and I don't know it's tolerances so LE is probably 4 +/-10%. From what I can see in hornresp this doesn't make a massive difference in response so lets just assume 4.
Assuming that we get the following response with this driver in the SS15.
Assuming that we get the following response with this driver in the SS15.
An externally hosted image should be here but it was not working when we last tested it.
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Yes, but doubtful that a light cone would survive the pressure, or sound any good near full Xmax.
And your sim is still about 20 Hz shy of your goal.
For a small enclosure the driver probably would put out a lot more low bass if you model it as a BR tuned to 30 Hz, a BR also could be a bit larger than the SS15 as it won't have near as many internal parts.
It will need to be stiff (forget MDF or 1/2 inch ply) and have a very large flared port to handle that much Xmax.
So the sim that I posted above is the specs for Jbells box here:
http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge.html
That is the box that I have it in now and it sounds great. I have run it up to around 100volts with my ep4000 amp with the 30hz hpf engaged and it sounds great with no signs of distress that I can discern. However there is little output below 40hz.
The point of this thread is to design a horn that will allow extension to 30hz in a similar size box and then compare the two in the real world and see how much output we are giving up.
This questions seems to constantly be coming up, and I think with the popularity of deep electronic music and most pop music being remixed, will continue to present a challenge for those of us that DJ or use pro sound. This will help show everyone exactly what they are giving up in SPL for the extra extension in a tapped horn.
http://www.diyaudio.com/forums/subwoofers/170771-single-sheet-th-challenge.html
That is the box that I have it in now and it sounds great. I have run it up to around 100volts with my ep4000 amp with the 30hz hpf engaged and it sounds great with no signs of distress that I can discern. However there is little output below 40hz.
The point of this thread is to design a horn that will allow extension to 30hz in a similar size box and then compare the two in the real world and see how much output we are giving up.
This questions seems to constantly be coming up, and I think with the popularity of deep electronic music and most pop music being remixed, will continue to present a challenge for those of us that DJ or use pro sound. This will help show everyone exactly what they are giving up in SPL for the extra extension in a tapped horn.
I am going to be running these full tilt for 6-8 hrs straight at an upcoming event so it will be interesting to see if the cones hold up. If they don't I will have my normal boxes there waiting.
So this also might answer some questions a lot of people have about whether drivers such as these will hold up at high pressure in a TH. This box has a fairly low compression ratio so though I am a newb, I think it will be fine. I will also most likely run my MFW-15 driver in these cabs until I experience a failure just to answer some of my own questions from threads predicting power handling in a tapped horn. It is a driver with well documented power handling and failure points in reflex and sealed enclosures. So it will make for a fun experiment.
So this also might answer some questions a lot of people have about whether drivers such as these will hold up at high pressure in a TH. This box has a fairly low compression ratio so though I am a newb, I think it will be fine. I will also most likely run my MFW-15 driver in these cabs until I experience a failure just to answer some of my own questions from threads predicting power handling in a tapped horn. It is a driver with well documented power handling and failure points in reflex and sealed enclosures. So it will make for a fun experiment.
The cones are very heavy duty on these and I'm sure you won't have any trouble there.
Modeling with the current parameters on the website though, you have a ~5 dB peak at 120 Hz. If you have any measurement gear or a signal generator, it would be interesting to see if that shows up in the design or is just in the Horn response model.
Modeling with the current parameters on the website though, you have a ~5 dB peak at 120 Hz. If you have any measurement gear or a signal generator, it would be interesting to see if that shows up in the design or is just in the Horn response model.
That's not possible. True 30hz extension and "ss15 sized" boxes are not in the same category.
For a 15-18" driver, and true 30hz from a tapped horn, or any horn loaded subwoofer for that matter, expect 400+ L cabinets. (Probably 5-600L)
You want compact and 30hz? Use a BR cabinet as Art said.
You want 30hz, compact and horn loaded? Try out my PAL12. Well it'll get close to 30hz, more like 35hz output. (Under 300L)
If you REALLY need the 30hz, forget the small size thing. Not gunna happen.
And I'm not talking about getting 30hz from a group of 50hz cabinets where excursion / distortion rises like crazy under Fb. If you want the 30hz from the beginning, design a rig to reach that. Don't do it as an after thought.
Just my 2c.
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