Ive had my hsu VTF2 Mk3 forever and I kinda wanted something new. Bringing a whole subwoofer from the US (live in Brazil) checked in on the plane is a huge hassle. I know, cause thats how I brought my hsu sub back home. After online dating with Speedwoofers I've decided that it's easier and better to just buy the driver, amp (not sure if plate or external) and assemble it here in Brazil.
I was thinking. If I get a 150ish liters box (not counting the area of the driver itself, potential amp or braces might take), would that be enough for a good response? I live in an apartment, even my hsu sub never ever reached anywhere near its potential, so I'm really not looking to reach some crazy output. My goal is to have an agile that performs very well for music and can deal with a good range (20hz+) for movies and videogames. 18 inches may sound a bit overkill, but since I can't just swap the driver cause I have to fly to America to get another one, I just don't wanna waste the trip.... does that make sense?
I cant get my hands on 0,25mm MDF here, which is pretty much equivalent to one inch thick. I was thinking maybe using the 1 inch thick MDF would make me require less bracing making the build a lot easier?
Also maybe using a external amp could make my life easier too for the assembly and maybe I could save money with a used external amp... I use a Denon 3313 CI. Do I need anything else? Or is it just the amp, woofer and enclosure?
Any thoughts? The Ultimax II 18" measurements made me really excited!!!
Help me out, and if you think something you might wanna point out is too obvious: don't. I'm stupid, go ahead and say it. I'm just an ******* with a dream here.
I was thinking. If I get a 150ish liters box (not counting the area of the driver itself, potential amp or braces might take), would that be enough for a good response? I live in an apartment, even my hsu sub never ever reached anywhere near its potential, so I'm really not looking to reach some crazy output. My goal is to have an agile that performs very well for music and can deal with a good range (20hz+) for movies and videogames. 18 inches may sound a bit overkill, but since I can't just swap the driver cause I have to fly to America to get another one, I just don't wanna waste the trip.... does that make sense?
I cant get my hands on 0,25mm MDF here, which is pretty much equivalent to one inch thick. I was thinking maybe using the 1 inch thick MDF would make me require less bracing making the build a lot easier?
Also maybe using a external amp could make my life easier too for the assembly and maybe I could save money with a used external amp... I use a Denon 3313 CI. Do I need anything else? Or is it just the amp, woofer and enclosure?
Any thoughts? The Ultimax II 18" measurements made me really excited!!!
Help me out, and if you think something you might wanna point out is too obvious: don't. I'm stupid, go ahead and say it. I'm just an ******* with a dream here.
The UM18-22 18" Ultimax DVC 2 Ohms/Coil driver has a Qts=0.53 with a low Fs=19.5Hz. This is a driver that could be used quite well on its own in open-baffle loudspeaker systems. Its simulated response for 200W re 8Ω of power input under those conditions is shown below.
If we place this same driver in a 150-litre sealed box enclosure, then we get the following simulated response at 200W re 8Ω:
Note that we now have a faster rate of roll-off, and the f6 = 22.1 Hz instead of f6 = 18.9 Hz. If we add a 2000µF series capacitor to the circuit, as well as applying a 4th-order Linkwitz–Riley low-pass filter set to 80Hz, we get the following response. The −3dB low-frequency point is now a very respectable 19.7Hz, which seems to be quite a good result for a 150-litre enclosure. The results are for a nominal 300W re 8Ω of power input, with a peak power draw of around 460W at 18Hz or so, and the driver excursion being at the Xmax limit of 22mm. A good plate amplifier can cope with that.
If you would prefer not to include a series capacitor, then we can go the alternative route and use a peaking high-pass filter set 20Hz and Q=2.0. This can produce the following response. This isn't quite as extended as the previous solution, and it has a faster roll-off below the low-frequency −3dB point. The amplifier needs to have at least a 400W re 8Ω capability, as it's doing all the hard work.
If we place this same driver in a 150-litre sealed box enclosure, then we get the following simulated response at 200W re 8Ω:
Note that we now have a faster rate of roll-off, and the f6 = 22.1 Hz instead of f6 = 18.9 Hz. If we add a 2000µF series capacitor to the circuit, as well as applying a 4th-order Linkwitz–Riley low-pass filter set to 80Hz, we get the following response. The −3dB low-frequency point is now a very respectable 19.7Hz, which seems to be quite a good result for a 150-litre enclosure. The results are for a nominal 300W re 8Ω of power input, with a peak power draw of around 460W at 18Hz or so, and the driver excursion being at the Xmax limit of 22mm. A good plate amplifier can cope with that.
If you would prefer not to include a series capacitor, then we can go the alternative route and use a peaking high-pass filter set 20Hz and Q=2.0. This can produce the following response. This isn't quite as extended as the previous solution, and it has a faster roll-off below the low-frequency −3dB point. The amplifier needs to have at least a 400W re 8Ω capability, as it's doing all the hard work.
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Wow, thank you, but I'm sorry to inform you, you probably just threw some pearls at pigs. Pigs being me. I dont know what a Linkwitz Riley is. Boy oh boy, I'm assuming that the 2000µF series capacitor is something I'd add to the amp? But I might be extremely wrong there....
I could make the enclosure a bit bigger, in fact I've been told that making it less cube shaped could be a good thing, so I was thinking about making it taller. Would it help? I'm really trying to avoid doing some soldering... I've heard that the CSS sdx12 is better for range and being in a relatively small box. But I don't think Ill be able to get one of those on the used market and they're pretty expensive. Whereas, the Ultimax drivers are plentiful in the used market in the US.
If you want to explain me what these things are I'll pay good attention. If you can't be arsed I understand that too.
Thanks 🙂
I could make the enclosure a bit bigger, in fact I've been told that making it less cube shaped could be a good thing, so I was thinking about making it taller. Would it help? I'm really trying to avoid doing some soldering... I've heard that the CSS sdx12 is better for range and being in a relatively small box. But I don't think Ill be able to get one of those on the used market and they're pretty expensive. Whereas, the Ultimax drivers are plentiful in the used market in the US.
If you want to explain me what these things are I'll pay good attention. If you can't be arsed I understand that too.
Thanks 🙂
A Linkeitz–Riley filter is a shape of filter that is often used as a low-pass filter on subwoofers. More details can be found here: https://en.m.wikipedia.org/wiki/Linkwitz–Riley_filter
Many AV receivers can apply Linkwitz–Riley filters to the low-frequency signal before it goes into the subwoofer.
Many AV receivers can apply Linkwitz–Riley filters to the low-frequency signal before it goes into the subwoofer.
The VTF-2 Mk3 uses a 12-inch driver, which is about the minimum size worth considering if good output levels at low frequencies are required. It's a dual-ported design, but has the facility to block one of the ports using the supplied foam port plug. The Hsu subwoofer offers various EQ settings to help get a desired low-frequency response curve. The performance specifications are:
Frequency Response Max. Extension Mode (±2 dB): 18 HzFrequency Response Max. Output Mode (±2 dB): 25 HzThose are quite respectable results. In sealed box mode, the roll-off would be 12dB/octave slower, and so the subwoofer might be expected to have more output at low frequencies around 15Hz.
Have you considered trading up to a Hsu VTF-2 Mk5, which allows fitting foam plugs to both ports, creating a sealed subwoofer? Then there is the VTF-3 Mk5, which uses a 15-inch driver and would likely produce a bit more low-frequency extension when configured in sealed mode. Alternatively, an SVS SB3000 13-inch sealed subwoofer offers excellent low-frequency extension, easily reaching 20Hz with a slow moderate rate of roll-off below that.
It isn't really, in the world of subwoofers, as it enables linear operation of the subwoofer to higher SPLs while trying to reproduce low frequencies. It's an engineering/performance-based choice.
The term agile performance is a difficult one to quantify, as low frequencies are going to be slower than high frequencies. Of course, sealed subwoofers are generally regarded as being more "agile", "faster", and "musical" than ported subwoofers. That's by virtue of the dynamical/transient behaviour of sealed subwoofers versus ported subwoofers, which is due to the 2nd-order low-frequency roll-off rate afforded by a sealed woofer versus the 4th-order roll-off rate of a ported driver. Of course, subwoofer systems usually include high-pass filtering to provide some driver protection against excessive excursion at very low frequencies, but the relative comparison still stands.
With a 25.4mm panel thickness, the bending stiffness is (25.4/19)^3 = 2.4 times that of 19mm MDF. You might get away with using less bracing, but most certainly some would be still be needed.
That can work, of course, but does add some limitations in terms of getting the most out of any particular driver. For many subwoofers, it is necessary to apply some filtering and EQ to get the best level of performance, and this points to using a compact, high-powered, plate amplifier with DSP on board.
The Denon AVR-3131CI seems like a fairly capable AV receiver. When using a subwoofer, it has low-pass/high-pass filter settings corresponding to 40Hz / 60Hz / 80Hz / 90Hz / 100Hz / 110Hz / 120Hz / 150Hz / 200Hz /
250Hz. Depending on your main speakers, the 80Hz setting would likely prove to be adequate. The AVR-3131CI also has Audyssey MultEQ XT, which will complement the AVR's built-in bass management system and help with the integration of the subwoofer with the main speakers.
It's entirely possible for you to create a good subwoofer using a plate amplifier, a woofer, and your chosen enclosure. It is a bit of work though, and the plate amplifier would ideally be one that has onboard DSP. This will enable you to get the maximum performance out of your chosen driver, while keeping it within its nominal linear excursion limits.
The 2000µF series capacitor would typically be included inside the enclosure. It could be soldered into the circuit comprised of the leads going from one of the subwoofer terminals to the appropriate speaker connection terminal mounted on the cabinet. It would of course also be possible to have the capacitor mounted externally; just be careful to keep its leads covered/protected so that short circuits don't happen!
For that 18-inch driver, a larger enclosure would enable a lower tuning, resulting in some extra low-frequency extension. Would a 200-litre enclosure be something that your room listening environment is amenable to?
A taller enclosure could prove beneficial. It would likely help to break up the panel structural vibration modes, so that they are not all close to the same resonance frequency. If you are talking about internal enclosure acoustic modes, then the wavelength of sound is way too long for the typical enclosure size to have any effect.
Oh my, we are really jumping around here! We've gone from an 18-inch driver to a 12-inch driver in one fell swoop. The SDX12 XBL2 is quite well suited to a smaller enclosure. In a 75-litre sealed enclosure, that 12-inch driver produces a −3dB point of a somewhat high 45.6Hz (see below). That's not really subwoofer territory, and it requires some EQ to get it working in that domain.
What happens if we add a 4th-order 80Hz Linkwitz–Riley low-pass filter? This is typical of the low-pass filter that will likely be introduced by your AV receiver's bass management system.
With that low-pass filter added we obtain the following response. Note how we have "magically" lowered the −3dB low-frequency cut-off point from 45.6Hz to 27.5Hz. However, note that at 80Hz the result is only about −3dB, rather than the desired −6dB (the response is −6dB at about 93Hz.). This is due to the naturally falling acoustic response of the woofer in that region.
What happens if we add +4.5dB of parametric EQ at 24Hz with Q=2.0 to the above response? The results are shown below. This was obtained for a nominal power input of 40W re 8Ω, and we reach the driver's Xmax limit at around 22Hz at that input power level.
If we don't have any PEQ facilities available, we can add a 1300µF series capacitor to produce the following response. We now have a −3dB low-frequency cut-off point of 17.1Hz, and the driver's Xmax will be exceeded just a little at 18Hz at this power level. The downside of this design is that the maximum response level is down by about 3dB, but that's just typical of the trade-off between the maximum output level and the low-frequency cut-off that can be achieved by a driver of a given size.
Let's investigate the possibility of a somewhat larger enclosure for use with the UM18-22 18" Ultimax DVC 2 Ohms/Coil driver. For example, we can choose a sealed enclosure that has an effective volume of 200 litres. If we add a series inductor of 1720µF, and include the 80Hz 4th-order Linkwitz–Riley low-pass filter coming from the bass management system on the AV receiver, we can get the following response for an input power of 200W re 8Ω.
In the above, the −3dB point is 17.8Hz, which is nice and low, and we have a 3rd-order roll-off rate, which is still quite good for ensuring a good transient response. At this power level, the driver is being driven close to its Xmax, and we have a maximum output level of 109dB! You can't get that with a typical 12-inch driver with a more conservative Xmax, that's for sure.
It's worth noting that the series capacitor is acting as a high-pass filter below about 13Hz, which helps protect the driver from large power inputs/excursion at infrasonic frequencies below the system cut-off frequency. Being a closed-box system, this design also has no port chuffing at high SPLs.
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The software is called VituixCAD, and I am using its Enclosure tool for the above simulations. The software can be found here: https://kimmosaunisto.net/
Thanks <3
About buying a new sub, I would def not go the DIY route if I lived in the US or Europe. But getting things to Brasil is both a pain and exceedingly expensive. And my sub is about the heaviest and biggest I could possibly bring with me on a flight back home. Thus the DIY route option presented to me. It's more of a practical thing for me, mainly because by doing so I don't have to check in the wood weight of the subwoofer / speakers that I bring back home.
How crucial would you say a DSP is for my use case? I mean, I'd give up on the external amp thing if it's really favorable. It's probably gonna be more expensive, but what's even more expensive is having to do a do over later. So I'd rather do it the right way straight away!
I can certainly make the box 200L by making it taller and maybe a little bit deeper (I'm assuming a sealed sub has no issues with being fairly close to the wall, right?). 17.8Hz F3 looks fantastic to me. Better than I anticipated tbh! Will it look weird? Yeah. But I don't give a damn, I'm not married.
PS: I wasnt thinking about foregoing bracing, just having to do less, to make it simpler on me and also maximizing the internal space of the enclosure 😉
PS2: What kind of dampening do you recommend?
About buying a new sub, I would def not go the DIY route if I lived in the US or Europe. But getting things to Brasil is both a pain and exceedingly expensive. And my sub is about the heaviest and biggest I could possibly bring with me on a flight back home. Thus the DIY route option presented to me. It's more of a practical thing for me, mainly because by doing so I don't have to check in the wood weight of the subwoofer / speakers that I bring back home.
How crucial would you say a DSP is for my use case? I mean, I'd give up on the external amp thing if it's really favorable. It's probably gonna be more expensive, but what's even more expensive is having to do a do over later. So I'd rather do it the right way straight away!
I can certainly make the box 200L by making it taller and maybe a little bit deeper (I'm assuming a sealed sub has no issues with being fairly close to the wall, right?). 17.8Hz F3 looks fantastic to me. Better than I anticipated tbh! Will it look weird? Yeah. But I don't give a damn, I'm not married.
PS: I wasnt thinking about foregoing bracing, just having to do less, to make it simpler on me and also maximizing the internal space of the enclosure 😉
PS2: What kind of dampening do you recommend?
@witwald , btw, you sound like a very knowledgeable guy so let me pick your brain kinda off topic here for a sec if you don't mind. In the future, after the sub, I will build a pair of towers so I can move my pair of Ascend Acoustics CMT-340 SE to my bedroom and leave the towers in my living room. Where can I find some good speaker projects to download or buy?
Also, in order to get effective 200L, how many liters should the internal space really be. Like, ofc, Im calculating the internal spacing deducing the thickness of the MDF, but that still doesn't count the area of the driver itself, bracing and potentially even the plate amp. Whats the internal area I should aim for in order to get effective 200L?
Also, in order to get effective 200L, how many liters should the internal space really be. Like, ofc, Im calculating the internal spacing deducing the thickness of the MDF, but that still doesn't count the area of the driver itself, bracing and potentially even the plate amp. Whats the internal area I should aim for in order to get effective 200L?
SVS have a dealer in Brasil, http://audiogene.com.br/. But they could still be a long way away from where you are located, making shipping diffcult.
DSP certainly isn't crucial, going by the potential designs that were previously explored, but it does offer a lot of flexibility. Of course, there would be a learning curve to navigate on the road to implementing DSP-based designs.
The external amplifier option is quite workable, as long as you have one that can put out reasonable power into a 4Ω load. Of course, how much power you need depends a lot on your desired listening levels.
I was a bit surprised by the 17.8Hz cut-off when a suitable series capacitor value is chosen. The driver is capable of very high SPLs if powered up to reach its Xmax, that's for sure. It seems quite capable of dealing with the LFE channel and its 10dB boost when watching movies.
Even with 25.4mm-thick panels, putting bracing in is probably still quite important, as you are going to be exciting some large "breathing" motion of the panel walls due to the cyclic internal pressure fluctuations. It doesn't need much of an increase in outside dimensions to compensate for the volume taken up by the bracing.
At the frequencies where the subwoofer is operating, say below 160Hz, I'm not sure if adding panel damping will make all that much difference. Of course, you can add damping panels, comprised of bitumen pads, and attach them to the inside surfaces of the walls of the enclosure. These bitumen damping panels are common in the car industry, and I'd try to find then in at least a 3mm thickness for them to have much effect. Some would come with a self-adhesive layer on one side. These could be themselves covered with a thin layer of aluminium sheet, creating what is known as constrained layer damping (see Noise and Vibration Control with Constrained Layer Damping Systems), making the damping much more effective.
The effective volume of the enclosure is not easy to specify entirely accurately. As you've mentioned, you need to take into account the volume of the bracing, as well as the internal volume displaced by the cone and the magnet structure. It really requires some work with a list of components and a spreadsheet, in order to be able to tally up all the separate contributions.
If you add an inch or two of acoustic absorption material to the panel walls, then this would likely make only increase the effective volume of the enclosure by a small amount, which might be able to be neglected.
For the case of a sealed enclosure, it's a good idea to fill it with acoustic absorption material, such as dacron filling. This will have the effect of increasing the effective acoustic volume of the enclosure, Vab, due to the changes in sound propagation through that medium, such that it is greater than the physical internal volume of the enclosure, Vb. Small has stated in one of his papers that "using practical materials the actual increase is probably never more than about 25%". The actual effective volume is something that can be determined once the enclosure is actually built and the driver and filling material installed. I suppose you could allow for an increase of 15%, which means that your enclosures physical volume would be 15% less than 200litres, or 170litres. It's still a big enclosure, whichever way we slice it and dice it!
If you add an inch or two of acoustic absorption material to the panel walls, then this would likely make only increase the effective volume of the enclosure by a small amount, which might be able to be neglected.
For the case of a sealed enclosure, it's a good idea to fill it with acoustic absorption material, such as dacron filling. This will have the effect of increasing the effective acoustic volume of the enclosure, Vab, due to the changes in sound propagation through that medium, such that it is greater than the physical internal volume of the enclosure, Vb. Small has stated in one of his papers that "using practical materials the actual increase is probably never more than about 25%". The actual effective volume is something that can be determined once the enclosure is actually built and the driver and filling material installed. I suppose you could allow for an increase of 15%, which means that your enclosures physical volume would be 15% less than 200litres, or 170litres. It's still a big enclosure, whichever way we slice it and dice it!
Think about building an enclosure which is not a simple cuboid, when such thick material and the bracing required to make it work properly will be minimised. A six-sided box is the weakest shape you can make an enclosure, having the largest unsupported panel size and hence the insane amount of bracing we see in larger enclosures. There is no worse shape where resonances are concerned, and especially problematic for subwoofers.
My 18" sealed subs are made from 15mm ply with 6mm bracing, and the first major resonance is around 500Hz; the greatest unsupported panel width is 70mm.
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As far as speaker projects go, maybe take a look at the following web sites:
http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm
https://www.madisoundspeakerstore.com/2-way-speaker-kits/
https://www.seas.no/index.php?option=com_content&view=category&id=66&Itemid=365
https://wilmslowaudio.co.uk/speaker-kits
There are no doubt many others.
http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm
https://www.madisoundspeakerstore.com/2-way-speaker-kits/
https://www.seas.no/index.php?option=com_content&view=category&id=66&Itemid=365
https://wilmslowaudio.co.uk/speaker-kits
There are no doubt many others.
Which particular 18-inch driver did you select? And what are the external enclosure dimensions? And what sort of amplifier did you use?
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The drivers chose me as they were on offer! 6 x B&C 18PZB100 in 55l enclosures. External 500 x 400mm approx.. Amplifiers 6 x Behringer EP 2500 bridged.
Nice. All of them except for madisound seems to be eurocentric. And madisound speakers are just rlyyyy expensive. I saw a kit on partsexpress, I've talked to them and they were willing to do the kit without the wood panels. Its a bit on the pricier side, but doable.... I'd love to be able to spend less than 800 dollars on the electronic parts alone.
https://www.parts-express.com/Solstice-MLTL-Reference-Tower-Speaker-Kit-300-708?quantity=1
But yeah, that's me jumping ahead of myself. It's subs first, then speakers.
Well, I'm not married, my gf doesn't live here. Making the cabinet taller would look kinda weird I guess. But What matters to me the most is the audio quality, so I'm willing to make the sacrifice. Besides, I put a nice wood veener around it or a nice looking paint, it won't look that bad. I just have to mind the footprint since the living room isnt that big. Heck, I'd still have to figure out where to put the second subwoofer if I do end up with a dual sub setup.
Oh man, trust me, its going to be cheaper to go to the US and back and bring back the SVS subwoofer rather than buy there. Here it's priced as a "luxury item". A more affordable option would be to buy it in Paraguay. But still, a hassle and expensive.
About my listening levels, I'm not crazy and I live in an apartment. I'm not looking to shake the building to oblivion lol. But how would that capacitor thing work? I'd install it to the plate amplifier? I saw some good options for used plate amplifiers online. I was thinking 500W or more. Depending on how much for the drivers I could even get two to build a pair of them, since ppl say two subwoofers is sooooooooo much better than one. The double damping with aluminum sounds great actually, since car stuff is not hard to find or expensive here. In fact the whole brazilian driver and speakers market is centered around the auto market.
Just found this video. The box is much smaller and its a passive speaker, but I liked how through he was with his explanations. The double baffle idea I sure did enjoy, and also how he made the bracing, it seemed like a nice simple idea. I'd probably need more bracing than that, but still seemed like an efficient way to do it. He didn't dampen it at all tho.