Hello guys, I'm sure there are many request for help concerning subwoofer builds, but I'm targeting a specific driver in a specific configuration. Firstly, I am NOT a pro at speaker design thus I asking for help here. Forgive me if i don't immediately understand all of the technical jargon... Give me a minute and I'll catch on fast though.
I got the idea of this build from two members here on DIYAUDIO. @xXBrunoXx and @mayhem13. I do plan to IM them with hopes that they will chime-in and further hone the ideas that they cross-pollinated into another build conversation that utilized a different driver.
My build desires starts with 6 each Dayton Audio SD315A-88 12" DVC 8+8 Ohm drivers. I am looking to integrate these driver into my HiFi listening space that is also in development and utilizing 15" coaxial full-range-loaded Open Baffles with 1" Horn Tweeters. The listening space is: 12' W x 18' L x 8ft ceilings. I'm hoping for results with as low distortion as possible, and as low frequency as possible using the driver selected. Amplifiers are a-plenty so that's not an issue.
My primary question for you guys and specifically the two members mentioned above is: What is the best scenario to use these driver as desired? My first intent is to use 4 of the drivers in front left/right-stacked configuration and placing the remaining two in the rear corners of the room. IDK if this sounds silly or not, that's why I'm hoping for great advice here. BTW, any of you guys are more than welcome to chime in... knowing that I am aware that there are always better parts with better potential. I got these drivers on sale and they have decent sensitivity. I don't listen to music at great SPL, clarity is what I hope from this build. Thanks.
I got the idea of this build from two members here on DIYAUDIO. @xXBrunoXx and @mayhem13. I do plan to IM them with hopes that they will chime-in and further hone the ideas that they cross-pollinated into another build conversation that utilized a different driver.
My build desires starts with 6 each Dayton Audio SD315A-88 12" DVC 8+8 Ohm drivers. I am looking to integrate these driver into my HiFi listening space that is also in development and utilizing 15" coaxial full-range-loaded Open Baffles with 1" Horn Tweeters. The listening space is: 12' W x 18' L x 8ft ceilings. I'm hoping for results with as low distortion as possible, and as low frequency as possible using the driver selected. Amplifiers are a-plenty so that's not an issue.
My primary question for you guys and specifically the two members mentioned above is: What is the best scenario to use these driver as desired? My first intent is to use 4 of the drivers in front left/right-stacked configuration and placing the remaining two in the rear corners of the room. IDK if this sounds silly or not, that's why I'm hoping for great advice here. BTW, any of you guys are more than welcome to chime in... knowing that I am aware that there are always better parts with better potential. I got these drivers on sale and they have decent sensitivity. I don't listen to music at great SPL, clarity is what I hope from this build. Thanks.
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Due to its low Qt, these are designed for either compression loaded horns or 'kick a$$' prosound midbass speakers, so ideally either a BLH or separate sub system.
Low Qts woofers will roll off Quickly in a model. Often leaving the lost being upset cause they want the response " Flat"
Usually leaning to the common assumptions it is a " unassisted " alignment
Even though in reality they apply EQ regardless. But just love annoying high tuning to try and make it " Flat"
If low Qts it is friendly to small boxes. But
.3 Qts probably put you in 4th order territory, meaning larger box to get low extension
Regardless, Meaning a standard BB4 alignment it should be Vented at Fs or 24 Hz in this case.
And for C4 likely slightly larger if not the same box will tune slightly higher. slightly.
Just dont be too discouraged low Qts drivers usually slope downward pretty Quickly.
And dont make the same annoying transient killing mistake and start high tuning attempting to make it " flat"
With multiple woofers and typical bass boost used, if even needed at all. Its gonna rock.
If you do bass boost, just be happy the transients will be more accurate than typical high tuned nonsense
Fs is low and take full advantage of it.
Usually leaning to the common assumptions it is a " unassisted " alignment
Even though in reality they apply EQ regardless. But just love annoying high tuning to try and make it " Flat"
If low Qts it is friendly to small boxes. But
.3 Qts probably put you in 4th order territory, meaning larger box to get low extension
Regardless, Meaning a standard BB4 alignment it should be Vented at Fs or 24 Hz in this case.
And for C4 likely slightly larger if not the same box will tune slightly higher. slightly.
Just dont be too discouraged low Qts drivers usually slope downward pretty Quickly.
And dont make the same annoying transient killing mistake and start high tuning attempting to make it " flat"
With multiple woofers and typical bass boost used, if even needed at all. Its gonna rock.
If you do bass boost, just be happy the transients will be more accurate than typical high tuned nonsense
Fs is low and take full advantage of it.
My immediate intent is to run them in enclosures. Not sure if sealed or ported. I was wondering if I could mix sealed and ported in the same room and not suffer at sound quality?
I can't imagine them being suited for Open Baffle; I read that a Qts below 0.7 is not favorable for OB. As for running Di-pole, If that means firing one driver forward and another rearward (out of phase) in a vertical stacked configuration , I'd be interested in exploring that potential.
I was sort of thinking about stacking two per side left and right front; I hadn't considered Di-pole because honsetly, I didn't know it was an option..... I'm still very much a novice at the technical aspects of design. I'm a hell-ofa wood-crafter though 😉
Hey, and thanks for responding so quickly. I am in no rush to build, I just ordered the drivers yesterday.
Thanks!
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There is nothing wrong with using low Q woofers for dipole. The bigger concern is that it's a complex topic to take on for a first project.
OK, I just went off to learn about the "Di-pole" option. My understanding is: in that configuration, bass will suffer at around 8-12dB and a null will form for on-axis listening. Bass not being on-axis is not an issue, as it's pretty much omni-directional anyway. So, the Di-pole build is probably not going to work.
I think my first hill-to-climb would be to nail-down the type of box that is best for the drivers. I'm hearing different concepts of the performance of sealed verses ported, although these drivers will normally only go down to 24Hz in ported config. I don't have a problem with that as long as the bass isn't boomy or sloppy.
I bought 6 drivers, so maybe I run the double vertical stack up front sealed, (maybe individual sealed boxes stacked and bolted together for versatility in case I need to pull two out of the front) and two out rear of the room ported to play down close to the 24Hz?
I wonder what sound I'd get if I built the boxes were the front baffle is recessed about 4-6 inches back from final front edge, sort of like if they were a horn themselves, but producing bass... just hypothesizing... I have no idea what that would work like, maybe some has tried it... I did see some "servo subs" that kinda looked like that...... I think GR Research has some like this.
I'll keep researching....
Depends on the room/app.
What a load of 'crap'! 0.5 is transient perfect, the ideal.
Yes, it's an option.
You're welcome!
@DEW-IT Hi, I'm not an expert by any means, I''ve built a few speakers over the years but I'm 100% there are people here who can guide you and help you build exactly what you're looking for . I don't know what your goals are ( linearity , low bass, . ) .
Why complicate things , I would go 6 sealed: maybe arranged like this ( picture in attachements ). ( use DSP or EQ to extend the low end and take care of the dips / peaks of the woofers / room ) or Go 4 sealed in each corner and one bigger ported box with two drivers for lows .
Or go ported, different freq tunning, two subs at 40, two subs at 30, maybe two sealed ?. You have many options with 6 subs.
You can experiment with placement of the subs in your room. You can get the " tight bass" going sealed with one or two , Low bass making bigger ported boxes . Combine sealed with ported .
Why complicate things , I would go 6 sealed: maybe arranged like this ( picture in attachements ). ( use DSP or EQ to extend the low end and take care of the dips / peaks of the woofers / room ) or Go 4 sealed in each corner and one bigger ported box with two drivers for lows .
Or go ported, different freq tunning, two subs at 40, two subs at 30, maybe two sealed ?. You have many options with 6 subs.
You can experiment with placement of the subs in your room. You can get the " tight bass" going sealed with one or two , Low bass making bigger ported boxes . Combine sealed with ported .
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Thanks @xXBrunoXx !!! You may not be an expert but you've given me some great ideas already to think about.
Often the experts have shortcomings communicating with us mere mortals..lol I reached out to you and @mayhem13 because of the thread you two chimed in on. You both seemed to be able to bounce ideas in a way that I could grasp. I,m not sure if the OP got his build done, but I certainly got inspired by both your contributions to his ask.
Listen, this is about having fun building, I'm sure I will pull something together that will work well. Sure, I'd love to avoid the giant pot-holes along the way, but if I make a few friends along the way, then the whole process will have been well worth the attempt.
I'm going to chew on your ideas over-night. Already I can feel a direction developing. Like I mentioned to @mayhen13, I just ordered the drivers, they are shipping soon, so I have time to communicate more before I fire up the saws. Thanks a buch for responding. you know, I had plans to direct message you but the board wouldn't let me send it because I'm too new here, (48 hr wait) I understand.
Be in touch. Appreciate it!
With such layouts, the main thing is to put them at the room's odd harmonics to start with and adjust from there if need be, though the best systems I auditioned were the three woofer systems in some high end projector HTs where there was one in a corner odd harmonic junction (OHJ), one at some OHJ on the opposing wall and one ~1/3 up the back wall at another OHJ.
The Thiele–Small parameters for the SD315A-88 are: Fs=24.2Hz, Qts=0.33, and Vas=151.7 litres. This moderately low value of Qts makes this driver well-suited to vented enclosures. Using a box volume of Vb=68.4 litres tuned to Fb=29.1Hz produces the following results for one driver, where we have hit the Xmax=7.0mm limit above the box tuning frequency for an input power of 112W re 4ohms (the driver DC resistance is Re=3.2ohms). This driver produces 111dBSPL at that input power level. Of course, being an unassisted vented box enclosure, the driver displacement shoots up very quickly below the box tuning frequency Fb, so it may be prudent to use a protective high-pass filter in many applications. The −3dB cut-off frequency is F3=34.6Hz, which is moderately high if one is striving to get as much low frequency response from the driver as possible.
If we detune the enclosure to Fb=24Hz, and add a 2nd-order peaking high-pass filter (HPF) with Q=1.70 and characteristic frequency Fc=23Hz, we obtain the result below. The maximum output is about 106dB SPL, and Xmax is reached at 16.6Hz when the input power level is set to 34W re 4 ohms. Note that the peaking HPF is adding a boost of 5dB at around 25Hz, so the actual input power at that frequency is much greater than the nominal value of 34W. The benefit of this filter-assisted design is that it has a much lower −3dB cut-off frequency, which has been reduced to 25.2Hz. This design seems to get as much low-frequency response from the driver as possible while protecting it against excessive excursion below the vent tuning frequency.
If we use this driver in a closed-box enclosure whose volume is Vb=68.4 litres (the same as the vented boxes used above), we can obtain the response shown below. This includes a parametric EQ (PEQ) set to boost by 6dB at 26.0Hz using a moderately broad Q=1.0. When we reach the driver Xmax=7.0mm limit, we achieve a maximum SPL of approximately 101dB. Here the −3dB cut-off frequency is 30.0Hz, which is a bit higher than that of the filter-assisted vented box, F3=25.2Hz, and the maximum SPL is about 10dB less, while the F10 values are very similar.
And if we add an extra +2.5dB of PEQ at 28.5Hz with Q=2.00, we can get the following response. Here the −3dB cut-off frequency is 25.6Hz, but we have to suffer a further drop in maximum SPL, due to the fact that a boost of about +8.5dB is being applied at 28Hz.
The PEQ-assisted closed-box designs might be the ones that best suit your needs. Although they have the lowest maximum SPL capability before the driver Xmax is reached, their use gets around that issue by the fact that you have six drivers to work with. 🙂
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Although the chosen drivers will "work" in this configuration, they will have a bass response that can be regarded as being prematurely rolled off for music applications.
The loss in low-frequency output when Qt<0.71 is going to be noticeable. This is exacerbated by the nulls occurring at 90 degrees to the driver front radiation axis of an OB loudspeaker. This further reduces the bass energy going into the listing room. Whether or not this is a "good thing" is open to debate, and may depend on user preferences. A lightweight bass presentation may result, which may give the impression of "tightness" in the bass, and a "better" transient response.
I’d agree with @witwald that given your use case, the SDA is best suited to a ported system
First things first since we’re talking hifi…..let’s understand your room first and understand its role in all of this……I try and shout from the soapbox as much as possible where bass and sub bass are concerned……ITS ALL MODAL!
Keeping it short….watch the link and see where your room gain will come in to play
Now……from a recording engineer’s perspective…..corners are the worst place for sound. If you can eliminate the corners of your space in a clever way……let’s say turn your rectangle into an octagonal shape……use those octagonal sides as actual enclosures for the drivers ( near floor to ceiling…….not much floor space but still huge volume) with up front, two SDA’s in each front corner stacked and one in each corner in the rear. The advantage is well beyond the bass as you’re eliminating the higher modes created by your mains in those corners. Three sided enclosures…..super easy to build too. An enclosure that’s floor to ceiling triangle 12x12x18 inches will yield you 4 cuft or working enclosure volume.
You’ll need to know your rooms response to choose the proper tuning frequency of each enclosure……….rough guess given your room dimensions?……….around 6db of room gain at 35hz and 12db of gain at 18hz. If we weren’t in DIy perfectionist mode, a fair guess would be to tune each sub to an f3 in room response of 40hz…….with 6 of em, considering the estimated room gain, we’re talking flat in room response to 20hz
Hey there, thanks for your input! First, if I don't respond right away know that I'm not wasting your time. I am in the background studying what you suggest, so as not to waste your time when I chime in to pick you guys brains. Like I mentioned, I am a novice at the technical aspects of speaker building; I'm learning fast though. So please bare with me if I ask something that might seem obvious to you guys 🙂
I watched your video by Erin, I totally love Erin's work! I watch him all the time. Though his video here is about car subs, I do understand the room-gain process in as much as it is in theory. I don't have WinISD so the modeling of my room will have to be estimated until I can get versed on that program... Again, My room is: 12"w x 18"L x 8 foot ceilings.
@witwald I believe has delivered me almost to the gold-post with this build. His details concerning the actual SD315A-88 drivers. Both his, ported and sealed scenarios are my new targets. ( I'm leaning sealed) As he suggested, The sealed route would probably walk-me-to-home, if I can get a few things in place, like the PEQ aspects of his idea. I believe he's modeling the sealed route on me using an parametric equalizer to adjust/boost frequency parameters to achieve his suggested outcome with the 6 drivers in sealed config. This scenarios if I understand, will land me in the range of 30Hz performance with an SPL of 101dB. I will run that by him for clarification.
YOUR BOX IDEA:
I believe his sealed model would dovetail with you "Octagon room Idea," where I could do the 4 enclosures in triangle configuration and placed in the corners. I like this idea. However, to stay in line with his data, the volume of the enclosures would have to fit his proposed Vb=68.4 litres; am I reading this right?
@witwald wrote: "If we use this driver in a closed-box enclosure whose volume is Vb=68.4 litres (the same as the vented boxes used above), we can obtain the response shown below. This includes a parametric EQ (PEQ) set to boost by 6dB at 26.0Hz using a moderately broad Q=1.0. When we reach the driver Xmax=7.0mm limit, we achieve a maximum SPL of approximately 101dB. Here the −3dB cut-off frequency is 30.0Hz, which is a bit higher than that of the filter-assisted vented box, F3=25.2Hz, and the maximum SPL is about 10dB less, while the F10 values are very similar."
I wont ramble more until I get a deeper understanding from @witwald. I will put it out there that I DO plan to treat the room by building corner deflector (maybe in concert with your enclosure idea) also front, rear, side, and ceiling damping. In addition, a floor area rug.
There's no panic to respond. I know you guys have busy lives. So reach out when you get time. I have notification turned on so I see when you reach-out.
Appreciate you!
I watched your video by Erin, I totally love Erin's work! I watch him all the time. Though his video here is about car subs, I do understand the room-gain process in as much as it is in theory. I don't have WinISD so the modeling of my room will have to be estimated until I can get versed on that program... Again, My room is: 12"w x 18"L x 8 foot ceilings.
@witwald I believe has delivered me almost to the gold-post with this build. His details concerning the actual SD315A-88 drivers. Both his, ported and sealed scenarios are my new targets. ( I'm leaning sealed) As he suggested, The sealed route would probably walk-me-to-home, if I can get a few things in place, like the PEQ aspects of his idea. I believe he's modeling the sealed route on me using an parametric equalizer to adjust/boost frequency parameters to achieve his suggested outcome with the 6 drivers in sealed config. This scenarios if I understand, will land me in the range of 30Hz performance with an SPL of 101dB. I will run that by him for clarification.
YOUR BOX IDEA:
I believe his sealed model would dovetail with you "Octagon room Idea," where I could do the 4 enclosures in triangle configuration and placed in the corners. I like this idea. However, to stay in line with his data, the volume of the enclosures would have to fit his proposed Vb=68.4 litres; am I reading this right?
@witwald wrote: "If we use this driver in a closed-box enclosure whose volume is Vb=68.4 litres (the same as the vented boxes used above), we can obtain the response shown below. This includes a parametric EQ (PEQ) set to boost by 6dB at 26.0Hz using a moderately broad Q=1.0. When we reach the driver Xmax=7.0mm limit, we achieve a maximum SPL of approximately 101dB. Here the −3dB cut-off frequency is 30.0Hz, which is a bit higher than that of the filter-assisted vented box, F3=25.2Hz, and the maximum SPL is about 10dB less, while the F10 values are very similar."
I wont ramble more until I get a deeper understanding from @witwald. I will put it out there that I DO plan to treat the room by building corner deflector (maybe in concert with your enclosure idea) also front, rear, side, and ceiling damping. In addition, a floor area rug.
There's no panic to respond. I know you guys have busy lives. So reach out when you get time. I have notification turned on so I see when you reach-out.
Appreciate you!
Interesting, except room gain has been debunked. It's there in theory, just not in practice.
WOW! WOW! Am I grateful that xXBronXx called in the cavalry to help me out... lol Sorry that I took so long responding. All day I have been studying your ideas and data, trying to get up to speed on terminology and your concepts in action.
@mayhem13 has chimed in at my request as I had witnessed his awesome ideas and inputs from another thread. He tossed-out the suggestion of using the 6 drivers in sealed configuration, as you also suggested, however building the enclosures in triangle form and placing them in the four corners of the room to assist in breaking up corner deflections in. I believe I understand him that way. (please take a minute to read my response to him as it addresses a few questions I have for you)
And before I go ANY FURTHER, let me say Thankyou! for your help. You expertise will shave-off the impossible for me towards getting this build done, all the while teaching me a multitude about this hobby. You are appreciated!
NOW, Though I would love to achieve the lower frequencies with this build, I am keenly aware that the drivers are just not optimal for reaching the lower Hz. With that in mind, I think targeting the sealed configuration that you've detailed is a more realistic and doable option. Besides that, it will involve less technical expertise on my end, not that I can't eventually rise to the challenge🙂
Here you wrote:
If we use this driver in a closed-box enclosure whose volume is Vb=68.4 litres (the same as the vented boxes used above), we can obtain the response shown below. This includes a parametric EQ (PEQ) set to boost by 6dB at 26.0Hz using a moderately broad Q=1.0. When we reach the driver Xmax=7.0mm limit, we achieve a maximum SPL of approximately 101dB. Here the −3dB cut-off frequency is 30.0Hz, which is a bit higher than that of the filter-assisted vented box, F3=25.2Hz, and the maximum SPL is about 10dB less, while the F10 values are very similar.
1. Vb=68.4 litres: could this enclosure requirement work in the triangle form as @mayhem13 likes, and still fit the data perimeters you've calculated? (please see his comments)
2. (This includes a parametric EQ (PEQ) set to boost by 6dB at 26.0Hz using a moderately broad Q=1.0) I read this to mean I would need an parametric Equalizer in front of the drivers? (where Q=1.0), here, I believe this is the setting required on the equalizer boost, is this correct?
3. ** If an Equalizer is suggested, do you know of any decent transparent units you can recommend? Also, I had a member mention a Subwoofer controller Rolls SX95. that would function in-front of the sub inputs....to filter frequency, this would be beneficial if I were doing gthe ported option right? I have plenty amps, but only my Crown XLS1002 has function pertinent to this build.*
4. My understanding: The goal is to avoid reaching driver Xmax+7.0 limit at all times, correct? So would this still yield around the 101dB SPL without running into driver damage territory?
5. By adding the extra 2.5dB of PEQ at 28.5Hz with Q=2.00; what SPL penalty would I realize? ( I couldn't see those numbers, and, as with above Q=1.00, I'm still a bit vague on understanding the meaning of the "Q=2,00")
You wrote:
And if we add an extra +2.5dB of PEQ at 28.5Hz with Q=2.00, we can get the following response. Here the −3dB cut-off frequency is 25.6Hz, but we have to suffer a further drop in maximum SPL, due to the fact that a boost of about +8.5dB is being applied at 28Hz.
The SDA drivers are fairly efficient @93.7dB but I think SPL much below 90 might leave me shallow in the low end....IDK, considering the SPL balance with my 15" Open Baffle Coaxials. They are very efficient also so I won't need to throw a bunch of power at any of these drivers, I think, because the room size. Clarity is my goal.
I'll stop here before I write a book..lol Please, there's no rush to respond, I have notifications turned on so I will see whenever you reply.
Hope you had a Great weekend!
Appreciated you!
I think Greg is referring to standing waves that might leave you in a node or antinode if not placing the subwoofers at harmonic intervals (I built a goofy open ended pipe speaker as an example) in the room ?
