Help with very first DIY subwoofer build
- This topic has 36 replies, 5 voices, and was last updated 9 months, 3 weeks ago by
.
-
Posts
-
-
Hi all,
So I am looking at building a DIY subwoofer for the very first time, and I am hoping to get some guidance on how to go about doing that. I’ve watched a handful of different DIY videos on designing subwoofers, but I feel like there are some important details that aren’t addressed because the author assumes people watching the videos already have some background/experience with building DIY subwoofers. What I am hoping for is a walkthrough – like treat/explain things to me like I’m a 5-year old – from start to the final design (not the construction, just the design).
A bit of background is that I currently run a simple 2.1ch HT/music system. The subwoofer in my system is a HSU ULS-15 MK2. I am in no way disappointed with it (I’ve had it since 2017 or 2018), but because it’s a single sub system, there are problems in the bass response that can only be fixed with the addition of a second sub. I know, I know… it’s best to have matching subs in a multi-sub system, but I think as long as there’s not too much of a disparity that it will be fine.
What I am hoping to build is an 18″ sealed box design (I prefer sealed over ported, plus my HSU us sealed, so keeping that the same, at least might help), and hopefully something that isn’t just a cube. I’ve spoken with someone else on a different site, but I’m getting the sense that their approach is a bit more convoluted than what I’m really after. We’ve talked about bandwidth/SPL goals, but that’s the part where I’m kind of… I don’t care? As long as the build equals or exceeds the ULS-15, output/spec-wise, I’ll be happy. I’m not after infrasound or being punched in the gut, I am more about clean, tight/fast/smooth, distortion-free bass. The sub won’t be any further than 8 feet away (minimum 6 feet).
I do live in Canada, so there may be some things that will be a little difficult to acquire. I can get components from Parts Express, and Solen in Canada has a selection of subwoofer drivers (Dayton, SB Audience mainly). If budget is a question, I don’t have one, really. Any 18″ offering from Rythmik or PSA (HSU doesn’t have an 18″ sub) lands in the $3k+ CAD price range after exchange rate/shipping/taxes, and Canadian ID companies like Funk and Harbottle are outrageously expensive. Because of that, whatever the cost of the build happens to be, it will be far less expensive than buying an equivalent, commercially-built subwoofer.
I am using a miniDSP Flex as my system’s preamp, so DSP will be handled through that. I’m sure I’m missing a lot of information, but if we start from the very beginning, I figure a lot of those questions can be addressed.
Thank you all in advance for your time.
-
You can’t go wrong with the tried and true Ultimax 18 kit from Parts Express. There’s TONS of forum posts and YouTube videos to reference for step by step instructions, and to get reviews of what you’d be getting as far as results.
My first 2 DIY subs were the sealed Ultimax 18’s, and they were super simple to do, and honestly are more than enough for any normal person’s expectations
-
I have certainly thought about that route, and it’s definitely a lot easier, but I do want to build this from the ground up.
I should also clarify that when I said “I don’t care?”, it’s more to the point that whether this build extends flat to 20Hz (with, say, an F3 of 16-18Hz, which is not far off from what I get with my ULS-15) at a SPL of 100dB, 110dB or 120dB, it really doesn’t matter to me. I’m not going to be that picky (if that makes any sense?). I do also live in a condo, so I can’t go too crazy with the SPL, but I would still like it to be able to hit those marks without any problems 🤣
I’m also not opposed to going with a 21″ driver if it makes hitting those targets easier.
** or dual 15″, but I think I’d like to keep it simple for a first-time build.
-
“… from the ground up…”
You mean your own design, or just doing all of the construction?
If you just want to do the construction, I have to recommend the Earthquake 21″ build that’s posted here for sale. It is absolutely shocking at how low and loud it gets, and I’m using the cheapest driver possible
-
Yeah, from the very beginning. I don’t want to just buy a kit.
I’d ideally like to stick with 18″, but I haven’t looked at the cost of 21″ drivers.
-
-
I wish to commend you on wanting to get down to the basics of understanding instead of just blindly following what “Joe Schmoe from down the street” says you should do. 👍👍
Just like any other Engineering field, this is all about the math. If you have, at a minimum, 3 to 4 basic pieces of data about a driver, you can get a baseline box design for just about any alignment (type of box design). These are:
Free Air Resonance or Resonant Frequency – Fs
Air Volume Compliance or Compliance Equivalent Volume – Vas (in Cu.Ft.)
Free Air Total Q or just Total Q – Qts
Driver Size in Inches (for my calculations) – where applicableIn this case, you want sealed, or Acoustic Suspension. This is one of the easiest to calculate.
As I said you’ll need the first 3 things (the 4th doesn’t matter here) above. There is one other thing that you will want to do, and that is decide on a final in cabinet Q, or System Q (Qcab) of the speaker when finished. Ideal is 0.707, Jazzy or punchy is around 0.6 while higher numbers are softer. Personally, I wouldn’t go for anything over a 1.0
Let me just state that I will be using alpha-numeric notation.
3 calcs you’ll do:
******
Z=(Qcab/Qts)^2*(1.05)-1
Box Resonance = Fs*Qcab/Qts
Inside cabinet volume = Vas/Z
******From this, you find the volume of the box and what frequency it is tuned.
Now, from here, go download WinISD and put in the driver parameters (there’s a good tutorial on how via Toid’s DIY YouTube channel) and play with the program to tweak things. You may find that some changes will help get you where you want to go.
-
Thank you so much – that is all very, very helpful information.
Yeah, if I’m going to do something like this, I think it’s important to know/understand the basics. DIY makes a little more sense to me right now, given there’s been a bit of a philosophical shift in how I set up my system. I should be clear that I am not disappointed with the sub I have – it’s a really good one IMO – so this wouldn’t be a replacement situation (at least for now – it all depends on how this project goes). I think I just need to add a second sub into my system (have needed this for a while I think).
I am also giving myself until next summer to get this done, so I have a fair amount of time to plan this out. My background is in fine arts, so I think I am pretty adept at building things. I have an idea in my head of how I want this to look like – a vintage-inspired design that’s in keeping with my Wharfedale Lintons. I’m getting a bit ahead of myself here, though.
I am aware that a Q of 0.707 is the ideal target. My system is sort of leaning more towards music which makes the Q around 0.6 (i.e. jazzy/punchy) intriguing.
For driver selection, is there any particular driver I should be looking at in the 18″ category? Is there any sort of consensus on whether to go with a Pro driver or HiFi driver? I get that there’s probably a lot of subjectivity to those answers, but I think it would still be useful to hear arguments for both, then I can make an informed decision based on my needs. Once I figure out the driver, then I can do the math to figure out box volume.
Thanks again.
-
Just so that I know I have the math right, I used the newer Dayton Ultimax II 18″ and got the following results (I used a Qcab of 0.707 for this example):
Z = 0.86 ?
Box Resonance = 29.35 ?
Inside cabinet volume = 288.60 (which seems awfully large…) ?
Would these be the correct results? I went to art school, so math… let’s just say… isn’t my strong suit… 🤣
-
This reply was modified 1 year, 4 months ago by .
-
This reply was modified 1 year, 4 months ago by .
-
This reply was modified 1 year, 4 months ago by .
-
This reply was modified 1 year, 4 months ago by .
-
This reply was modified 1 year, 4 months ago by
-
-
I’m out a a grocery store.at the moment. I’ll have a look when I get home.
-
Sounds good. So you don’t have to go searching, the relevant specs of the Ultimax II 18″ are:
Fs = 22Hz
Qts = 0.53
Vas = 248.2 liters
-
-
Using the data off PE’s page, I get 10.0987 cuft, or 286 L.
You used the slightly more accurate numbers, so you’re good.
-
Cool, thank you! So that means my math was (more or less) correct? I did get 285 liters plus change, too, if I rounded the Z value up to 0.87 instead of leaving it with the 6 or so decimal points. If I went with the Ultimax II 18″, is there a way to reduce the size of the box a little bit without negatively affecting the results too much or… ? Like, raising the Qcab to 0.8 reduces it to a 6.31 cubic ft cabinet volume, but I don’t know what effect that has (yet).
And what about a driver like the SB Audience NERO-18SW1900D? When I did the same math, I get an Inside Cabinet volume of 2.82 cubic ft (70.75 cubic liters). That seems smaller than it should be (I got a Z value of 1.98 and box resonance of 57.23Hz)? Would you lower the Qcab value in that case (say, 0.6 or 0.5)?
Fs of that driver is 34Hz, Qts is 0.42 and Vas is 157.9 liters
And with regards to driver selection, is there a particular type of driver that is better-suited for a sealed cabinet vs. vented?
-
For those calcs I gave you, the Z value is just an intermediate value used to calculate box volume. No need to worry about posting it.
As to what is better for sealed vs vented/ported vs open baffle, really low Q drivers (0.30 or less) are better suited to sealed. Somewhat higher (say 0.35 up into the high 0.6 range) are better suited to ports or equivalent. Generally very high Q (somewhere around .95 or more ) are better suited to infinite baffle.
I invite comments from others on this. Please weigh in.
As to Toid’s videos all of them on WinISD are recommended, especially the one about entering the speaker driver parameters. To help, here is a screenshot of everything that needs to be entered:
-
Once again, thanks for the input. I do subscribe to Toid’s YT, so I can go watch some of those videos shortly.
My mentioning of the cabinet volumes was more to verify that I was doing things “correctly.” I understand that there are things like bracing, and damping materials that would effectively increase the box size in order to hit the numbers (particularly those drivers that yield a much smaller net volume). I was plunking the results into the online SubBox pro calculator (which does account for the woofer displacement, but not any of the bracing, etc…), and in some cases I would get boxes that were, say, 22″ x 22″ x 5″ or something silly. I’m not going to worry too much about that until I look at things in WinISD, and move on to the next steps.
I’ll check out some drivers that have lower Qts values – are there any particular drivers I should absolutely avoid (i.e. brand)? And should I be worrying about whether the driver has a neodymium or ferrite magnet?
And agreed – if there’s anyone else who can offer their advice/opinions, please chime in!
EDIT:
So I am watching an intro WinISD video from Toid and when entering the driver data, one of the specs he mentions – Cms – isn’t even listed in the driver specs (example the B&C 18DS100-4 driver). What do you do in that case?
EDIT 2:
I was able to find the Cms info from loudspeakerdatabase.com, so if I run into that issue again, I can always check there. I did download the actual file from that site, but it wasn’t showing up when I tried to import in WinISD. I think it’s just due to the way I’m running the software on my Mac. If I decide that I want to pursue this more beyond this project, then I might pony up the dough for a Parallels subscription, and run it through something more “official.”
-
I am a Mac user, but I was just able to get WinISD running via Wineskin, so I can start to tinker around with that. Which Toid video do you recommend I watch?
I’ve also seen that there’s a specific order you have to enter the information. Is that still true?
-
-
I also would like to recommend watching HexiBase (on YouTube) and in particular, his videos on T/S parameters. Very thorough explanation of how it is all derived and they interact to calculate other T/S parameters.
Previously, I gave you the order of Sealed -> Vented -> Infinite Baffle. In HexiBase’s video, it’s Vented -> Sealed -> Infinite Baffle. I still say play with the drivers in different enclosure types to see how they model. ME, Personally, I prefer a Qts of around .40 to .42 for Vented, down to .38 or up to mid .5’s. Really, it all depends.-
Thanks for that – I did go and watch Hexibase’s videos on T/S parameters. Because I have no previous history with this process, a lot of it admittedly went over my head, but it was all very informative.
I think what I am getting hung up on right now (and might need a nudge to get out of) is the box size. I still have to look at a few other drivers to see what that looks like in WinISD, but the one driver I played around with the one driver came back with a volume of 0.905 cubic feet (around 25.6 liters). What my idiot brain is struggling with is how does that work? Clearly I’m not building a box that isn’t even be deep enough to fit the depth of the driver, so how do you determine the actual size of box to build when the math gives you values that are so small?
The other thing I’m going to need to understand is what filters (i.e. Linkwitz transform or 2nd order HP, etc…) do you apply in WinISD to get more out of the driver. I know the models don’t account for room gain, but again… no experience to know what to do at this time.
-
-
Ok, so I think I’m going to need a bit of help understanding some of the settings in WinISD. I’m looking at an SB Audience ROSSO 18SW800 driver in this example. I’ve entered all of the necessary driver information, and it’s spit out whatever WinISD spits out. I will list my questions below:
1. Under Signal > System input power, what value do I enter? It’s an 8ohm nominal driver, and if I, say, use a Crown XLS 1002, it gives a Bridged 8ohm rating of 700W. I’ve also seen in a few videos that they enter 80% of the total value of the amp they are planning to use… if my idiot brain is understanding this right, would be 560W? Now, what I see when I select SPL, the graph starts rolling off, and when it hits about 45Hz, there’s a kink in the slope and the roll off isn’t as gradual. I’ve attached a photo of what that looks like on my end. When I, say, lower that to 400W, the kink goes away. The overall SPL drops a bit before it starts to roll off, but only by about 1-2dB.
2. You can see in the attached photo that by the time it hits 20Hz, the SPL has dropped by a fair amount. I understand that none of this accounts for room gain, etc… but I would like it to be higher at the 20Hz point. My understanding is that I would probably need to add a Linkwitz transform filter to achieve that, but I haven’t the foggiest clue what numbers to enter in order to create the “correct” filter. For example, if I am aiming to hit an F3 of around 16Hz, what do I enter for the f0, fp, Q0 and Qp values? In my example, WinISD seems to automatically set the f0 to the Fsc value under the Box tab and the Q0 automatically gets set to 0.449. Fp and Qp were set by default to 20Hz and 0.707. I’ve attached a photo to show what that looks like on my end (you can see the kink more clearly – I left the system input power at 560W, and dropping it to 400 removes that kink). I have also attached a photo of what the cone excursion graph looks like with this filter applied.
3. Is all of this fruitless with the driver I am modelling in this example? Would a different driver be a better fit?
-
Chiming in as a novice. Some big idea things I’m noticing:
That driver you listed for this test has an Fs of 33Hz. My understanding is that a driver’s response tends to fall off quickly after that number so it might not be the right choice if you’re looking to get to 20Hz.
Don’t ignore the cone excursion graph. I missed that on my first one and was confused that my speaker wasn’t playing as low as the SPL graph showed. When you pass the red line it will not play those frequencies. I haven’t built a sealed sub yet but I’m pretty sure If you want it to go lower before hitting cone excursion the box needs to be bigger. Those guidelines for how big of a box fits that driver is just a starting point. Feel free to adjust it to suit your preferred outcome
Cone excursion is based on input wattage though. If you won’t run it that high then you can back off the wattage and see how low it goes at quieter volumes
-
It doesn’t seem to matter what driver I select, in my tests so far. Even the Dayton RSS460HO-4, which has a spec’d Fs of 18.8Hz or the new iteration of the Ultimax 18″ (Fs of 22Hz) kind of does the same thing (though the UMII18-22 does seem to have an easier time). I don’t know what the specs are for the driver in my HSU ULS-15, but it hits 20Hz in my space (though that’s with room gain), and it’s only a 15″ driver in an 18″ cube. What I would like to know is why that kink in the graph appears. I do have the Xmax limited box checked in the Advanced tab (which is what Toid says to do in his tutorial video).
I’m absolutely not ignoring the cone excursion, which is why I want to figure out how to correctly set the Linkwitz transform filter. Each time I apply that filter at whatever defaults it shows when i add the filter (this differs depending on the driver), the cone excursion skyrockets, so there has to be a way to do it where the excursion doesn’t go off the charts. Increasing the box size doesn’t appear to lower the excursion, either, it seems to make it worse, in fact. Shrinking the box does lower the excursion, but the box Q goes up past where I want it to be.
Backing off the system input power does drop the excursion, but it doesn’t drop below the red line until I set the system input power to 5 watts (at 7ft, which is where the sub would be located from my MLP) with that ROSSO 18SW800. That drops the SPL down to 95dB with the Linkwitz transform is disabled (down from 114dB) before it starts to roll off. My own personal listening levels aren’t that high – about 60 to 65dB on average – so I don’t know how much of that I have to factor into this whole thing. Also when taking measurements in REW, I bump the MV up so that the measurement SPL level is around 40-50dB above the noise floor. I just don’t want to build something only to have it explode if I try to take a measurement.
-
-
I’ve tinkered around with the newer Dayton Ultimax II driver – can someone have a look at this file, and let me know if there’s something wrong (I’m still not sure about the system input power, for example)? This is all just testing the waters, so nothing is set in stone or anything like that. Bear in mind that I do not quite know what I’m doing, here, so I apologize to those who are far more experienced. The volume of this is 10.5 cuft to hit a Q of 0.707. The Linkwitz Transform filter is set at the default of what it spit out when I added the filter. The system power input was reduced to 150w in order to get the cone excursion below the red line.
If I remove the Linkwitz transform, bump the system power input to 1240 watts (80% of the 1550w available with a Crown 1502, bridged 4ohm), then simply adding a 2nd order Butterworth Highpass filter cutoff at 10Hz looks like it might be better/simpler? Only “issue” there is the F3 ends up being about 30Hz, F10 would be about 18Hz (though that’s still at about 102dB).
I watched a video from Dayton where the guy goes through the construction of the previous Ultimax 18″ kit they had, and when he talks about stuffing, he says that 1lb of stuffing = 1 cuft. My understanding from that is if I were to build a 6.5 cuft box for this driver, I would add 4lbs of stuffing to get the driver to see it as a 10.5 cuft box, yes?
-
I checked out the file you linked. I think your main problem is trying to add low end below what the driver can do. If you follow the recommended Vas from that driver’s spec page of 248 liters and put no filters in you can see that the response in WinISD matches pretty close to the published graph on that spec sheet. Even using the full 1200 watts RMS as advertised you will not hit cone excursion. Because of the impedance curve the fact is that the driver can only play so low and so loud. You can tune that bottom end up if you’re running at lower wattage or you can leave the natural roll off and go up to the rated RMS wattage.
-
That’s sort of what I am looking into finding out with the Linkwitz transform filter – i.e. what can be done to manipulate it to squeeze a bit more low end without causing the cone excursion to go off the charts. The only thing that seems to do that is lowering the system input power, but then I’m sacrificing a lot of SPL, which I may or may not want (ultimately this all gets level matched down to 75dB anyway once it’s integrated into the system). I also know that none of this accounts for room gain, so I am sure some of that low end will get a bit of a boost from that.
What I think I might end up doing if that Linkwitz thing is a bust – should I stick with the UMII18-22 – is leave it as is, and apply a simple 2nd order Butterworth Highpass filter to get that cone excursion down a little bit since it does creep up a bit past the red line. Because really, 18Hz at 102dB is still pretty okay in my books, which – again – would be a little bit more due to room gain.
Now, would I be safe to assume that the Dayton Audio guy in the video is correct when he says that 1lb of stuffing = 1 cuft, which would get the driver (UMII18-22, in this case) to see a 6.5 cuft box as a 10.5 cuft box if I stuffed it with 4lbs of damping material? If so, and I just leave things as is with a simple Highpass filter then I think I might have my build, but I am going to look at a few more drivers in the meantime to see if there’s anything “better.” There are a lot of options out there, and I’m still not sure which one is the perfect fit. A lot of these drivers only seem to have Fs values around 30-40Hz, so there’s gotta be a way to get more extension via DSP without causing them to explode, no?
I’ve also looked at the Dayton RSS460HO-4, which should be the closest thing to the UMII18-22, but it rolls off a lot sooner than what Dayton’s specs seems to indicate when I pop it into WinISD, so I don’t know what’s going on there.
And someone has to know what those kinks in the graphs mean… it’s only there when the SPL Xmax limited box is selected, but I would like to know what it means.
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by
-
-
You have discovered the trade-off of SPL vs. LF extension. It’s just harder for drivers to push those low frequencies at high volumes. That’s why live events need a wall of subs to get usable levels that low in frequency. The Meyer VLFC is even made just for that very bottom end because regular subs don’t do it well. You can get that low in theatres because it’s a much lower SPL required for a small space. They also tend to have multiple subs to achieve that result.
A highpass filter is definitely recommended as a safety for subs even if it starts at 20-25Hz. You don’t want them trying to play lower than that without a limit on the excursion from a HP filter. Personally 102dB would be plenty for my listening but that’s subjective. Stuffing is a bit complicated. I’m wary of broad statements like “this much stuffing makes the box seem this big”. I think sam_adams from this forum explains it well (https://www.audiosciencereview.com/forum/index.php?threads/is-all-speaker-fill-created-equal.47151/) You need dense material to limit airflow but everything in speaker building has a tradeoff. In this case you are sacrificing efficiency.
I see what you are saying about the RSS not going as low in WinISD as their graph. My only observation is an efficiency gain. Using less wattage to get the same SPL maybe means you can bump the low end more before cone excursion? Not sure there
What kinks in the graph are you referring to?
-
What do people typically do in that case? Do they retain the SPL or do they sacrifice SPL in favour of low end extension? Or is it one of those “it depends on…” answers? This project is meant to add a second sub into my system (and if it goes well, build it again, and replace my HSU -ULS-15 altogether), so that is another thing to consider with regards to low end extension.
The HPF option really seems to be the easiest option, and I’m not too distraught about the results with the UMII18 driver – again, 102dB at 18Hz is still very loud (and yes, I am aware of the equal loudness curve, etc… so I know for it to be “audible” it requires significantly higher SPL).
The stuffing I would use wouldn’t necessarily be the typical polyfill. I’d probably use actual carted wool (which I think is denser, and more effective) – my wife is a knitter, and spins her own yarn sometimes, so I have a good, cheap source for that – or some of that recycled denim insulation (2″ thick) or a combination of both.
This is an extreme example, but this is what I’m talking about (I think it will appear below). This is the same ROSSO driver as above (post #17, I think), but I set the system power input at the full 800 watts (the driver’s RMS value) to exaggerate the effect. It’s there when I set the system input power for that driver even at the 80% value (560 watts) of the amp I would’ve probably used in this particular case (Crown 1002 – its 8ohm bridged value is 700 watts, and the ROSSO is an 8ohm nominal driver). This shows up when the “SPL is Xmax limited” box is checked in the Advanced section under “Project” in the bottom left corner of the screenshot. In Toid’s video about creating the “perfect box” he says to check that option. You can see in the graph that it starts to roll off, and then at about 55Hz, there’s a sharp elbow, and the graph goes down in a straight line instead of a gradual curve. It seems to be related to cone excursion, but even if I apply a Highpass filter to drop the excursion below the line, it’s still there.
-
-
I think you should go back and double check everything in your driver information / parameters. When I brought the file into WinISD, many of the designations (just to the right of the input boxes) were not set to the same as the datasheet from Dayton Audio – M instead of mm or cm, etc. Yes, most of it came through and converted fine, but some of the data was just plain wrong – like the BL and the RE were multiples of what they should have been.
So, go back and set the designations correctly, then match up the green inputs to the datasheet. Go over them 2 or 3 times just to make sure, then save the driver.
Now make a new project with a closed box and .707 Q and see what it looks like then. Now, on the data sheet it specifies that XMAX is good up to 70% of power, so put 840 in the watts area of the signal tab. You should be much more pleased with the outcome.
-
Can you take a screenshot and show me because I am certain I had the correct values (i.e. mm, cm2, Tm, mm/N, etc…)
I’ve also just installed WinISD on the PC I use at work, and entered the values of the ROSSO 18SW800 (the driver cited in those screenshots), and got the same results as what I see at home.
If you’re referring to the .wpr file I attached above with the UMII18-22 driver – again… I am certain the values are correct. Also, the UMII18-22 is different from the previous UM18-22, and I was referencing Dayton’s own datasheet.
I even just downloaded the .wpr file I attached, loaded it into WinISD at work (where I’m at right now), and all of the values (i.e. mm, cm2, Tm, mm/N, etc…) are all correct vs the UMII18-22’s datasheet
Edit: Sorry – just looked a little closer. For some reason the Re and Bl values weren’t correct, so I have adjusted those… don’t know what happened there, but I definitely didn’t enter 16.8 ohm or 38 Bl for that driver (and they were set to the correct ohm and Tm settings…)
Edit 2: I figured out why it set those specs higher – when I changed the number of voice coils to 2 (which is has), then the ohm and Bl numbers jumped up. I also set it to Series because the data sheet says, “*Dual 2-ohm voice coils. All specifications measured with voice coils wired in series.”
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by .
-
This reply was modified 1 year, 3 months ago by
-
I’ve attached an update .wpr for the UMII18-22 (the data for this driver should be correct, now?). Please let me know if there’s anything horribly wrong with this. I could probably benefit from some help regarding the Linkwitz transform filter. But it might not even be necessary since a simple 2nd order Butterworth Highpass gets me to about the same end result, but with more system input power.
As always, thank you for your incredible input so far.
-
This is how it came into Win ISD. Fix Le (1.15 mH), Sd (1184 cm^2), and Znom (2 ohm). Next post with info.
-
-
Default design from prompts to 0.707 (works out to 0.704) and no filter, 840W.
-
Oh dear… 🤣 I must have had that ROSSO driver in my head because 1256.6 is the Sd for that. I’ve corrected those variables, and added the Le (it wasn’t auto-calculating, and it’s not a number that I recall Toid entering in his video so I haven’t been including that). It (obviously) now matches what you’ve shown in your screenshots. The only question I have would be about the Znom. You mention to change it to 2ohm, but on the PE site (and even the Dayton Audio site), it does say that the impedance is 4ohm. So wouldn’t that make the Znom entry 4ohm? And is everything else was okay?
Under Signal, I do set the distance to 7ft (2.134 meters) because that’s technically how far the sub would be from my MLP. That doesn’t appear to affect the cone excursion when I change it to that value, thankfully. I also nudged the system input power to 880W since that’s 80% of what a Crown 1002 would do in its 4ohm bridged mode.
I would like to build the box a little smaller than the volume generated in WinISD, so what’s the “best” approach to shrinking the box without compromising things too much? If I shrink the box by 4-5 cuft, is there a known mathematical formula to calculate how much “stuffing” to put inside the box for the driver to see it as 11.398 cuft? I get that it probably depends on the material used since there are differences in density, but even a general “guideline” would be helpful. Ben here has addressed some of this, but I welcome as much information as possible in order to gain a better understanding.
Dayton Audio suggests a 4 cuft closed box for this driver (Q target of 0.8). Reducing the box in WinISD to 6.51 cuft gets a Q of 0.8, which tells me that there’s ~2.5 cuft of space (less the space taken up by the bracing, and woofer displacement) that is filled with some kind of “stuffing”, yes?
Understanding that room gain will play a part, is there a way to bring the low end extension up a little bit without causing the cone excursion to skyrocket? When would one use a Linkwitz transform filter (I know its application is only for sealed/closed boxes)? What do those 4 values mean (f0 Q0, fp and Qp)? It seems that this UMII18-22 driver is good on its own without any real tweaking like that, but say if a different driver that didn’t extend as low as the UMII18-22 was chosen… though I haven’t come across a driver that “beats” the UMII18-22.
I do apologize for all of the dumb questions. Once again, thank you for your time, and patience (I get how frustrating it can be when dealing with people who are completely new to something like this – I regularly teach silkscreen printing to people who have little-to-no experience with the medium).
-
I know it’s been some time since my last reply, but I did want to clarify (in case it came across this way) that citing the specs from Dayton/PE was not meant in any way as a any kind of “Nuh uh you’re wrong” kind of thing, I was only looking to find out whether the Dayton/PE specs Nominal impedance spec should be entered or if the Znom was to be set to 2ohm. I did load in the driver with Znom set to 2 and 4ohm, and quite literally the only difference was something like -/+ 0.3 to 0.5dB in SPL, which is audibly not going to make any difference.
At this point, I think I have the driver selected as I haven’t come across any other driver that has naturally extended as low as the UMII18-22. I am sure that some of the low end will get a boost from room gain, so I’m not too worried abotu that. I’d rather keep things as simple as possible for my very first attempt.
So given all of that, I might be at the stage of figuring out the cabinet size/damping materials, etc… While I personally wouldn’t be adverse to build an 11 cuft box, I do enjoy having my head on my shoulders, so I think I would ideally like for this to be somewhere around 7 cuft as a max box size. I’m hoping that it’s as easy as what I’ve seen across a few other forums (1lb of polyfill = 0.75 to 1 cuft), but I’ve also seen posts that seem to suggest that it’s not that simple (in my case, though, I’d use carted wool instead of a synthetic polyfill). I’ll continue to search around the internet, but I think it might be a little difficult to sift through all of the proverbial chatter, which has the potential for analysis paralysis.
Anyway, I can’t thank you enough for all of the help in this. I certainly hope that I haven’t been too annoying or caused any amount of frustration 😳
-
-
Sorry I haven’t replied. It’s just that I have a metric S***-ton of stuff going on right now and there’s not enough time for me to sit down and go over everything. I was hoping another denizen of the forum would hop on and help. Either way, I’ve got to get back at it. I’ll check in at some point soon.
-
Oh, please don’t feel as though you’re obligated to respond. 😳
Unless there’s a trick with filters to extend the low end without exploding the cone excursion, I think I might be able to move on to the details surrounding the box itself?
And if there are any other users here that can add their voice to this, please do!
-
-
I’m in a similiar situation. Did you ever figure out how much damping material to put inside? I think you’re spot on with the 4 cubic ft 0.8 Qtc alignment using damping material, otherwise the numbers given by dayton audio just doesn’t add up. Did you end up building it? I plan on doing a 6 cubic ft enclosure with the same driver; 11 cubic ft feels a bit large unless you’re doing something like a cylindrical enclosure.
-
I have not even made any attempt to build this yet – it was always going to be a project to start sometime this year (I started thinking about it late last year) once the weather got warmer. I also have a tendency to plan these things, and abandon them due to laziness. It’s been a long time since I’ve been on this forum, but I believe I was sort of targeting a Q of 0.7, and the math would have been based on whatever WinISD spit out at me.
-
-
I’m not saying I have an answer for how much damping material to use to simulate a cubic ft, but this video was helpful – https://www.youtube.com/watch?v=3xe-g35SmEY
A few people in the comments mentioned a point of diminishing returns, where adding additional damping material begins to reduce total output. Someone also said 40% of the enclosures volume with polyfill will be effective (some trial and error will likely be necessary to dial in the best amount). Using WinISD, my enclosure size of 6 cubic ft has an f10 of 20.35 Hz and 0.844 Qtc, which brings me down only 2 dB compared to using the 0.707 enclosure – and that’s without any damping material. With damping material I imagine 0.761 could be possible, which estimates only 1 dB loss at 20 Hz. I will likely do some measurements once I finish building mine.
-
- You must be logged in to reply to this topic.