| dfdye |
Hi!
I have been searching for some design ideas for the Hi-Fi version of the Dayton RS 12" sub, especially since they are sale this month, but I have yet to find any that have caught my eye. Thus, I figured I would throw something out there for comments before diving into building a new sub. This is my first attempt at designing a speaker, so any comments are more than welcome!
Here are my design goals:
“Moderate” box size
Sealed box
Usable response down to 20 Hz
Cheap!!!
I want to use a sealed box, both for ease of construction and to avoid port issues/noise. Of course, a good starting point would be to model the response of the speaker in the box, so I used WinISD and got the response below in a 1.9 cu. ft. sealed box. Obviously there is a lot missing on the low end. To solve this, I would like to use a Linkwitz transform circuit as an EQ to bring up the low end. Modeling this circuit to try and get f3 of 20 Hz gives, what I believe to be, pretty reasonable values without too drastically having to boost the low end. (If the circuit/component values would be helpful, I’ll post them too!) I know the ~8dB boost at 20Hz is a lot to ask of the amp, but as I said, I am not looking for massive output in that frequency range—just something reasonable.
I figured a Bash 300W plate amp would be a nice fit for this since I am not trying to tear the house down with this sub. Also, I would be worried about too much power for this driver if I went with a 500W amp. If I do need more output, I can add another unit, but I am not really a volume fiend (not that that is bad or any thing!) so I doubt that I will ever push this unit to its max. (Famous last words, right??)
If anyone has comments as to the viability of this design or comments about using Linkwitz transform circuits, I would love to hear them!
Thanks!
David |
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| mazurek |
I would suggest not to linkwitz transform it down to 20 hz, 30hz is a more reasonable target in my opinion for the sealed subwoofer. I have solely a rumble filter at 16hz, and the cone looks like it is excursing about as far as it should at respectable listening levels, I wouldn't want it to go further.
Also, try playing with the sub and test tones once you build it. I can't hear anything below 30 hz even though I'm sure there is output (spl meter, plus parts of house resonate). I would like to hear other's thoughts on this.
I believe linkwitz discusses somewhere on his site the pros and cons of his transform with respect to excursion limits. Look at his thor subwoofer, it is very similar in my opinion to a sealed dayton rf.
Another issue, factor in the lowpass to the sub into the winisd model. It looks more like an upside down parabola, and the -3db point relative to the peak spl output from the sub will be lower in frequency. |
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| dfdye |
I have indeed looked at Linkwitz's web page, and his Thor sub based on the Peerless XLS 12" was what gave me the idea for this design. He uses a more complicated crossover topology for the Thor than what I am interested in, but he also takes the boost out well past 20 Hz. That may very well be driver dependent, so I will definitely heed your suggestions about the excursion limits of this driver and play with the LT circuit before making anything permanent.
From your comments it sounds like you have one of these drivers already--is this accurate? I would like some feedback (positive or negative) about this sub since so few opinions exist from people who have actually used this driver.
As for your question regarding hearing below 30 Hz, I think I can hear down to ~20, though below 25 it is primarily feel with a little reinforcement with the ears, if that makes any sense. For me there is definitely a steep roll-off below 25, though I am not confident that I have ever really heard a system capable of producing high SPL low frequencies that would let me claim this 100% yet. Anyway, I would love to have down to 20 Hz just to have all of my bases covered (though I am still a LONG way away from considering one of those fan subs to get down to 1Hz!) |
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| mazurek |
Yes, I have 2 x sealed subwoofers with 2.2 cubic feet and the dayton hf 12". I definitely don't think they are holding my system back (stereo martin logan mosaics to be replaced with diys). I'd say they are clean, but that will depend on how you design the sub crossover, I think Linkwitz transforms are good for group delay. The way I have them crossed now (just a rumble filter), they make movies fun but don't quite rattle the house.
I can't give any critical audiophile comments as I don't have golden ears, and they are not crossed over correctly into my mains because they will be moved shortly(should be 24db/oct).
If you want, I can post a measurement for 25 hz spl, just tell me, but I got to go to class now. |
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| dfdye |
| I would love to see what they do at 25 Hz if it is not too much trouble. Thanks for offering! |
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| owdi |
Before you design a sub to be flat down to 20hz consider the impact of room gain. Check the help in WinISD for how to estimate room gain with a Linkwitz Transform.
Dan |
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| DSP_Geek |
| quote: | Originally posted by owdi
Before you design a sub to be flat down to 20hz consider the impact of room gain. Check the help in WinISD for how to estimate room gain with a Linkwitz Transform. |
True enough, but room gain comes in at +6 dB/octave while sealed boxes roll off at -12 dB/octave, so there's still a case to be made for Linkwitz transforms. The good doctor himself offers crossovers with both a LT and a switchable 50 Hz first-order high pass.
Cheers,
Francois. |
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| dfdye |
| quote: | Originally posted by DSP_Geek
True enough, but room gain comes in at +6 dB/octave while sealed boxes roll off at -12 dB/octave, so there's still a case to be made for Linkwitz transforms. |
Indeed, but I made the classic mistake of forgetting that I will actually use the speakers in a room and not in the computer! :) I am trying to rectify that now. |
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| mazurek |
I was watching the cone, and playing a 25 hz test tone. From watching some white dot on the cone moving back and forth, it looked like about 12 mm peak to peak excursion resulted in 90 dB at 1 meter using an uncalibrated radioshack digital meter (+5db if same calibration as analog). I stopped there because my house was going to explode, and my subwoofer is my baby and I don't want to hurt it.
I think it would get about 6db more at full excursion according to winisd. |
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| dfdye |
| quote: | Originally posted by mazurek
I stopped there because my house was going to explode |
Nice!! Thanks for the measurement.
As another EQ option I have been looking at the built in bass boost of the Bash amp. Taking room gain into consideration (thanks owdi! though I am not sure I am doing it right yet. . . .), enabling a +5 db boost at 20-24 Hz smooths out the low end fairly nicely. Of course, without room gain, the bass boost doesn't do enough--thus the original proposal for using a LT. There is a little peaking, so I am sure I am going to have to play with the system to get it right once it is in the room, but eliminating the LT would definitely simplify things. |
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| owdi |
| quote: | Originally posted by DSP_Geek
True enough, but room gain comes in at +6 dB/octave while sealed boxes roll off at -12 dB/octave, so there's still a case to be made for Linkwitz transforms. The good doctor himself offers crossovers with both a LT and a switchable 50 Hz first-order high pass.
Cheers,
Francois. |
Try this tool, the Room Response Calculator.
Dan |
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| dfdye |
It looks great, but I am having issues getting it to work. I think it is the version of Excel I am running, so I will try it later on a different computer. Thanks for the tip!
David |
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| owdi |
Something else to try is WinISD .50a7 (the alpha version). This is much more powerful than the pro version, and can show you maximum SPL and power graphs.
In a 1.9 cu ft. box, the Dayton 12" HF sub can hit 100db at 25hz w/ 250 watts at full xmax.
I tried a few different configurations and the amount of bass boost you will want really depends on the in room response. 5db at 25-30 hz seems right in a midsize room.
A ported box would be much more difficult given your size restrictions. The only way you could pull it off is by doubling box size, using a slot port, and half the box would be the port.
Dan |
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| dfdye |
| quote: | Originally posted by owdi
Something else to try is WinISD .50a7 (the alpha version). |
I actually switched to that in hopes of finding the room response function, but all I could manage was using a LT to simulate room gain.
That's what I was using to model the amp bass boost, and assuming a 3-6 db room gain at 20 Hz, the +5 bass boost at 22 Hz gave me a little better low end extension than the 25-30. Of course I am sure we are using different paramaters somewhere to cause the discrepency, but either way, I am sure that you will agree that playing around with it once the sub is in the room will be the ultimate guide! (I am sure my wife will love to hear that!)| quote: | Originally posted by owdi
A ported box would be much more difficult given your size restrictions. The only way you could pull it off is by doubling box size, using a slot port, and half the box would be the port.
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Absolutely! And I have never heard a ported box that I like. I am CERTAIN that they exist, but I have yet to find it. I am pretty comfortable with the 2.1 cu ft sealed box coupled with electronic EQ to get down to the range I want. If it sounds terrible, I can always try another one! :) |
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| dfdye |
Well, I just finished hooking it up (figured priming the box without putting on a slick finish would be sufficient since it would be hidden most of the time), and I am quite impressed if I do say so myself.
I have not been able to run frequency sweeps due to my wife wanting to watch Charlie and the Chocolate Factory :), but so far the sound sems pretty ballanced and definitely fills out my North Creek CM-77's well.
Final configuration was 2.1 cu. ft. box with +4db @ 22 Hz. I unfortunately don't have a mic. that is anywhere close to flat (that is definitely on my wish list, though!), so I can't post response curves in the room. I will, however, let you know qualitativetely what is going on when I get a chance.
Thanks everyone for the feedback! |
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| troyhenson |
I just completed a project with the BASH 300W amp and I really like it (different driver though). To enable me to easily adjust the boost I added a temporary bread board for the boost resistors and ran it outside of the enclosure during testing. This worked well but introduced a bit of hum that went away as soon as the final resistors were soldered to the amp's boards.
I used WinISD to model the system. In my listening room (23 ft. by 13 ft by 7 ft - in the basement) the bass gain fit a parametric EQ setting of 23 Hz, +3dB, with Q=0.65. I'm sure other rooms are quite different, but that may be a starting point to help you to determine how much EQ boost you will need in your design. With those figures WinISD was spot-on with the in-room response of the system. I was quite pleasantly surprised.
-Troy |
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| dfdye |
I have also been pleasantly surprised. WinISD seems to have hit the parameters spot on. The sub qualitatively has a pretty flat response from ~100 Hz to 30 Hz based on my ears not noticing any nasty peaks or dips in response while running sine wave sweeps. Below that, I start loosing hearing sensitivity, so I can’t make a good judgment as to intensity, though there is definitely usable response down to ~22 Hz which is where I can’t hear it any more, but the cone is still definitely cranking below that. Fortunately, there don’t seem to be any nasty room mode peaks and the rough room modeling seems to be spot on.
I must admit that I am not one to believe in vanishingly low ripple in frequency response curves. As long as I don’t notice peaks, they don’t exist to me! :D That being said, I can happily say that this sub is “Flat to Me.” (insert catch phrase trademark symbol here! :) ). I was worried this would not be the case due to using the bass boost on the amp, but it seems to blend quite well. This was definitely easier than using a LT circuit.
EDIT: forgot to mention that I posted a cutout sheet for the box in another thread in case anyone is interested. The thread is here: http://www.diyaudio.com/forums/show...&threadid=71667 |
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| dfdye |
Here are some crappy pictures I took with my phone (!!!) but they show the general idea. Enjoy.
Also, I know the placement it horrid, but it is wife mandated, so it will have to do until we move in a few months. |
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| dfdye |
| And another of the amp. . . |
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| simon5 |
| Corner placement is not that horrid. It depends on the room hehe! |
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| grae |
| I'm really interested in building a setup almost identical to your's, but vented. Could I yield better results as far as frequency response and output with a ported enclosure the same size? The drivers I have in mind are the 10 or 12" ts2+ or the Dayton HiFi's. I've been playing around with bassbox pro and winisd for the past few days now, and I'm still not sure I'm doing everything correctly. It seems that with the tc2+'s I would need a larger enclosure to get the desired results I want. |
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| dfdye |
If you want a vented enclosure, I would recommend that you look closely at the RS High Output drivers. From what I have heard of them, they are designed for vented or small sealed box enclosures, whereas the HF versions are designed for (relatively) larger sealed enclosures.
I have not played around with the HO drivers, but I can say that with the system I described here, I can get down to ~25 Hz with what sounds like a pretty flat response, though I have not measured--only listened to a frequency generator via computer output. To my untrained ear, this sub is not at all boomy, but there is a nasty room mode that creeps in from time to time when all of the doors are shut in my den. :D I can hear down to 22 Hz where the driver is still putting out a pretty good deal of sound, but below that my hearing cuts out (though the driver is still going crazy!) I am not sure how much lower you want to go than this, but even with a tuned port, I am not sure how much lower you could get with this driver.
I am not sure exactly what your goals are, so I cannot tell you whether you will be able to get what you want with the sealed HF's, but if you could better describe what you think my setup will lack that you are interested in (like the power to rattle the nails out of your house's frame :eek: ) then let me know and I may be able to offer some suggestions. Specifically, I am not sure how low you want to go and how much output you want! I am quite pleased with the frequency response of my system, and the output is MORE than enough for the small room I have it in (I have the amp power knob turned to ~the 10 o’clock position and I think I still have it a little high sometimes).
If you really want more output, the HO driver accepts a ton more power (700W I think), but by the time you put money into a larger amp, I would think you could build a pair of moderately powered subs (~300W each) with the same or greater output level that would be more musically accurate than a vented enclosure.
If you are primarily interested in hearing explosions from DVD's this obviously won't make too much of a difference, but if you are going to use the subs as musical sources too, I would go with 2 moderately powered sealed boxes over 1 monster vented enclosure, but that's just me! :) |
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| paulspencer |
| I've tried the room response calculator and when comparing it to actual response of the room, there isn't much similarity! In fact if I had used the simulation in my design in any way, it would have done a lot of damage! Where it predicted a large 50 Hz dip, there is actually a large 35 Hz peak and no dip until 80 Hz. |
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| dfdye |
| quote: | Originally posted by paulspencer
I've tried the room response calculator and when comparing it to actual response of the room, there isn't much similarity! In fact if I had used the simulation in my design in any way, it would have done a lot of damage! Where it predicted a large 50 Hz dip, there is actually a large 35 Hz peak and no dip until 80 Hz. |
Good to know for future reference. I guess I am glad I never got it to work and assumed a generic room response instead! |
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