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Droogne

Sundown ZV4 18D2 - sealed enclosure

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After a long time (and many many discussions about different drivers) I finally have chosen a driver and a design for my first build.

The driver is the very powerfull Sundown Audio zv4 18D2. A lot of info by Ricci can be found in the driver section. I have ordered 2, so will be making 2 exact enclosures.

Enclosure will be 62x62x50cm sealed. So around 158L before driver and bracing. Material will be carpent grade 18mm ply. Will be using a 22mm or double layer 18mm for the baffle. This because there wont be a lot of place between the driver cutout and the internal top and ground plate. 

Reason for this design is simple. To save room, and for many other reasons, I have chosen to have the sub as a platform for my LaScalas, and for "WAF" like reasons, it seemed best to let them have the exact footprint. This is also why I'll be using ply, to have it match the LaScala. Do I know it would probably perform better in a huge ported enclosure? Yes, and I'm also planning on doing this with these drivers. Plan is as followed:

1: build the 2x sealed enclosures

2: build the 2x ported (460L) enclosures

3: adjust the driver cutout to fit the Dayton Ultimax UM18-22 (or similar other 18" driver). The difference between them is very small. I can also make the enclosure tot fit the Ultimax from the start. The difference is .06", and I doubt it will matter for the Sundown driver that the cutout is this much bigger. 

Why stepwise, and not start with the ported subs? It comes down to my inexperience in subwoofer DIY and to keep my options open for the ported design. As this will be my first build, start with something small, cheap and simple seems the best way. That way I can see what tools I need to upgrade or buy for the more complex (slot)ported build. I will also have 2 subs that are moveable when needed, and less of a money loss when I make a big mistake.

The ported would also be a speaker platform, but I don't have the mains that will be placed under them, so it might be better to wait till I know the exact dimensions of those mains. I would also like to keep the option open to use a 24" driver for the main subs. In that case the Sundown drivers would go in to 2x smaller (ca 300L) ported subs in the back. 

Build itself

As I'm new to this, I don't know the hurdles I'll have to jump over, and what to look out for. Any pointers will be hugely appreciated. 

The cutting: I'm gonna have the same people who are building my LaScalas cut the ply. This to ensure the dimensions are correct. 

Baffle cutout: as said before I'll probably use a double baffle, with a 16,75" cutout to ensure the Ultimax will fit in nicely in the future. I'll be using a regular jigsaw for this. 

Putting it all together: this is where it gets tricky. I don't have big enough clamps.. When I build my flatpack horn loaded subwoofer I didnt require it, as it used screws instead. Except if someone can give me a way to still use glue without screws, or if I find somewhere where I can rent the clamps I'll be doing it like this: pre drill all the pannels, probably 2 or 3 on each side, then also predrill into the second pannels, this time with a smaller diameter. I would also mill the holes on the outside so the screws will sink in nicely. When putting it all together I would still use boatloads of glue, but the screws will keep the pannels thight to eachother when drying. 

Bracing

I'm gonna copy the bracing from the Marty subs (see attachment). So simple rectangular pieces from one side to the other. Would be around 2 on each side, so around 6 in total. Around 15,6L. I could also go for 2 windowbraces if there is enough spare ply. 

Filling:

Another subject where I'm wading in the unknown. What would you guys suggest? And how would this affect the volume I put in winISD? 

Wiring

As the cables are a lot cheaper, and I'll probably will have to lay around 5-10meters of them, I'll be using regular speaker wire. Any reason not to do this? 

Not sure yet how I'm gonna wire it all. I have 2 subs, which both have 2 2ohm loads. Do I wire them together inside, and connect them both to the same terminal? And do I use 1 or 2 sets of terminals for each sub? The hornsub In already have, has 2 terminals connected together internaly. Or is this not necessary when using regular wire instead of SpeakON cables? 

 

 

Amp & EQ

Amplifier

Will be using a PSA2700 amp for now. See attachment for all the specs. It has a 2x 350W output at 8ohm, 530@ 4ohm, 750W @2ohm, is bridgeable, and can tolerate a 2ohm load. What would be the best way to wire the subs? I could bridge the amp and wire all the coils in series. That way I have over 700W (not sure exactly how much it was). If I wire them for 2 seperate 4ohm loads I have 530W each. The Amp is definetely temporary. Open to any suggestions for a new one. Will probably be looking for a good second hand Powersoft model. What output (or specific model) should I be looking for? Other option is an iNuke NU6000 as they go for absurdly low prices on the second hand market.

EQ

I'll be using a UMIK-1 setup mic and REW to determin the appropriate PEQs for my Behringer Ultradriver DCX2496.

 

 

Thanks for reading through! Any thoughts, suggestions or questions are very welcome!

 

 

 

 

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Glad you settled on some good drivers.  :) You'll definitely want more power.  Your amp choice may be influenced by whether you need DSP/EQ capability on the amps or have an external DSP.  I honestly don't know amps that well and have rather expensive tastes.  For me the choice of a SpeakerPower SP2-12k was easy, being that I wanted something without noisy fans and had no need for DSP.

On 2/2/2018 at 3:59 PM, Droogne said:

Bracing

I'm gonna copy the bracing from the Marty subs (see attachment). So simple rectangular pieces from one side to the other. Would be around 2 on each side, so around 6 in total. Around 15,6L. I could also go for 2 windowbraces if there is enough spare ply.

Opinions vary as to how much and what kind of bracing is suitable, but the Marty-style should be fine for you.  The primary intention is to push the resonance frequencies of the panels up as much as possible and to reduce mechanical transmission from the driver to the cabinet.  If you want to add additional braces, my suggestion would be to put them between the front and rear, close to where the driver basket sits.  This, along with a thicker (ideally doubled 18mm) baffle, will help with the latter goal.

On 2/2/2018 at 3:59 PM, Droogne said:

Filling:

Another subject where I'm wading in the unknown. What would you guys suggest? And how would this affect the volume I put in winISD?

Again, opinions vary, but I lean toward using it pretty sparingly.  The goals are to knock out the modal resonances that energize within the cabinet airspace, kill the rear wave from the driver, and for a ported design, substantially absorb the frequencies that coincide with the port resonance.  Attaching 4" thick absorbent material of your choiec to the cabinet walls should work pretty well.

If cabinet is stuffed more densely, it will significantly change the low frequency response of the driver and give the appearance of extended bass.  However, it appears this apparent increase in extension occurs primarily due to a loss of output at higher frequencies rather than an increase of output at lower frequencies.  So in other words, it's probably best to avoid over-stuffing.

Most types of stuffing occupy little actual volume, so there is no need to compensate volume in WinISD.

On 2/2/2018 at 3:59 PM, Droogne said:

Wiring

As the cables are a lot cheaper, and I'll probably will have to lay around 5-10meters of them, I'll be using regular speaker wire. Any reason not to do this? 

Not sure yet how I'm gonna wire it all. I have 2 subs, which both have 2 2ohm loads. Do I wire them together inside, and connect them both to the same terminal? And do I use 1 or 2 sets of terminals for each sub? The hornsub In already have, has 2 terminals connected together internaly. Or is this not necessary when using regular wire instead of SpeakON cables?

Speaker wire is fine, but you might consider a lower (thicker) gauge than is typical.  Each of my dual-opposed 21" subs is run off a 6kW amp channel, and I connect each sub using a 4-wire 12-guage cable.  So, each 21" driver (3 kW power) gets its own 12-guage run.

You'll want to run each 2 ohm voice coil in series and then either connect them to each amp channel or run them in series to the amp in bridged mode.  For your PSA-2700 amp, I don't think it will matter.  You can series the voice within the cabinet by running a short lead between the (+) of one set of terminals and the (-) of the other.  Or you can just wire both sets of terminals to one 4-pole SpeakON connector and construct a cable adapter to put them in series.

With my subs, I opted to connect each set of terminals directly to a SpeakON, so that if I decide to add another amp later, I can run the coils in parallel without having to open the cabinets.  Each sub has two drivers, each with two voice coils which connect the two SpeakON ports in each cabinet.  They are connected to the amps via the 4-wire cables using adapters that split the 4-wires into pairs, each of which goes into a separate SpeakON connector that gets plugged into each port on the cabinet.  I bent short strands of 12-guage wire into a U-shape and inserted it into the two unused terminals of the connectors in order to create a series connection between the voice coils.  When it's time to add another amp, I can just make new Y-adapter connectors that parallel into the 4-pole SpeakONs instead.

Does that make sense?

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On 4-2-2018 at 8:34 AM, SME said:

Glad you settled on some good drivers.  :) You'll definitely want more power.  Your amp choice may be influenced by whether you need DSP/EQ capability on the amps or have an external DSP.  I honestly don't know amps that well and have rather expensive tastes.  For me the choice of a SpeakerPower SP2-12k was easy, being that I wanted something without noisy fans and had no need for DSP.

First of all, sorry for the late answer! I was enjoying some quality (ski)vacation in Italy. Good times. Now I'm back and 2 months of almost 100% free time to throw at my sound system.

The drivers just arrived! Those are some damn heavy monsters ö almost hurt my arm trying to lift them up my stairs! 

IMG_20180214_141321.jpg

Amps are something I know I will have to do something about. It will work for now, and thats what Important. Upgrading the amp is the next step. in the "grand plan".

On 4-2-2018 at 8:34 AM, SME said:

Opinions vary as to how much and what kind of bracing is suitable, but the Marty-style should be fine for you.  The primary intention is to push the resonance frequencies of the panels up as much as possible and to reduce mechanical transmission from the driver to the cabinet.  If you want to add additional braces, my suggestion would be to put them between the front and rear, close to where the driver basket sits.  This, along with a thicker (ideally doubled 18mm) baffle, will help with the latter goal.

Got it. Thanks.

On 4-2-2018 at 8:34 AM, SME said:

Again, opinions vary, but I lean toward using it pretty sparingly.  The goals are to knock out the modal resonances that energize within the cabinet airspace, kill the rear wave from the driver, and for a ported design, substantially absorb the frequencies that coincide with the port resonance.  Attaching 4" thick absorbent material of your choiec to the cabinet walls should work pretty well.

If cabinet is stuffed more densely, it will significantly change the low frequency response of the driver and give the appearance of extended bass.  However, it appears this apparent increase in extension occurs primarily due to a loss of output at higher frequencies rather than an increase of output at lower frequencies.  So in other words, it's probably best to avoid over-stuffing.

Not sure what material to use, but it seems people are using a lot of standard mattress filling etc, should something like that work? 

On 4-2-2018 at 8:34 AM, SME said:

Most types of stuffing occupy little actual volume, so there is no need to compensate volume in WinISD.

I mean vice versa, that stuffing actuallyl increases the internal volume. By 15-20% I heard. 

On 4-2-2018 at 8:34 AM, SME said:

Speaker wire is fine, but you might consider a lower (thicker) gauge than is typical.  Each of my dual-opposed 21" subs is run off a 6kW amp channel, and I connect each sub using a 4-wire 12-guage cable.  So, each 21" driver (3 kW power) gets its own 12-guage run.

Yeah, I was thinking about using thicker wire. Wouldnt 2 smaller cables give the same result? 

On 4-2-2018 at 8:34 AM, SME said:

You'll want to run each 2 ohm voice coil in series and then either connect them to each amp channel or run them in series to the amp in bridged mode.  For your PSA-2700 amp, I don't think it will matter.  You can series the voice within the cabinet by running a short lead between the (+) of one set of terminals and the (-) of the other.  Or you can just wire both sets of terminals to one 4-pole SpeakON connector and construct a cable adapter to put them in series.

With my subs, I opted to connect each set of terminals directly to a SpeakON, so that if I decide to add another amp later, I can run the coils in parallel without having to open the cabinets.  Each sub has two drivers, each with two voice coils which connect the two SpeakON ports in each cabinet.  They are connected to the amps via the 4-wire cables using adapters that split the 4-wires into pairs, each of which goes into a separate SpeakON connector that gets plugged into each port on the cabinet.  I bent short strands of 12-guage wire into a U-shape and inserted it into the two unused terminals of the connectors in order to create a series connection between the voice coils.  When it's time to add another amp, I can just make new Y-adapter connectors that parallel into the 4-pole SpeakONs instead.

Does that make sense?

It does. It actually does. Seems similar to what I have in my PA sub atm. 

 

 

About the build it self: as I'm coordinating this build with the LaScalas the project will have to wait for another week as the LaScala builders need extra time to start. I have also asked for a quote on the cutting for the pannels, so there is possibility I'll only need to assemble the bins. So I think I'm looking at 1 or 2 weeks till my front stage is done (Xilica actively crossed 2-way LaScalas with a K510 horn and Faital PRO HF200 drivers and the 2 Sundown subs)

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7 hours ago, Droogne said:

Not sure what material to use, but it seems people are using a lot of standard mattress filling etc, should something like that work?

Yeah, it should work OK.  It may not absorb as well as some other options like rockwool or fiber glass, but those are a lot more messy to work with.  You'll want to use staples or some other method to keep it in place.  Another option which is more pricey is to use acoustic foam wedges with spray adhesive, like I did.

8 hours ago, Droogne said:

I mean vice versa, that stuffing actuallyl increases the internal volume. By 15-20% I heard.

This is kind of a misleading conclusion.  Dense stuffing will indeed alter the relative response shape to have a lower Q, as though the enclosure has more volume.  However, the response shape changes because of a loss of output near the resonance and because of an increase in output below it, which is what happens with more volume.  So even though too much stuffing *looks like* an increase in volume , all you're really doing is throwing away output.  You still want enough stuffing to absorb the rear wave from the woofer and control standing waves inside the enclosure though.

8 hours ago, Droogne said:

Yeah, I was thinking about using thicker wire. Wouldnt 2 smaller cables give the same result?

Yep.  What's important is total cross-sectional area, so basically: number_of_cables * pi * (D/4)^2, where D is the diameter and can be looked up in AWG charts via Google.

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29 minutes ago, SME said:

Yeah, it should work OK.  It may not absorb as well as some other options like rockwool or fiber glass, but those are a lot more messy to work with.  You'll want to use staples or some other method to keep it in place.  Another option which is more pricey is to use acoustic foam wedges with spray adhesive, like I did.

Hmm I'll look up some prices. Dont imagine using something a bit more expensive will be a big cost relatively.

29 minutes ago, SME said:

This is kind of a misleading conclusion.  Dense stuffing will indeed alter the relative response shape to have a lower Q, as though the enclosure has more volume.  However, the response shape changes because of a loss of output near the resonance and because of an increase in output below it, which is what happens with more volume.  So even though too much stuffing *looks like* an increase in volume , all you're really doing is throwing away output.  You still want enough stuffing to absorb the rear wave from the woofer and control standing waves inside the enclosure though.

Ok, already thought that after your last comment about it, but wanted to be sure. I'll stuff, but I'll leave it out of winISD. 

29 minutes ago, SME said:

Yep.  What's important is total cross-sectional area, so basically: number_of_cables * pi * (D/4)^2, where D is the diameter and can be looked up in AWG charts via Google.

Yeah, I just have a lot of wires laying around (bought like a 200m roll for my surround) so will just combine them. 

 

Will keep you posted about any developments. Till I build them and the LaScalas I'm gonna keep busy with my new Xilica (gonna actively amp my LCR) and designing and building a custom synergy horn to use as height channels.

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@SME 

 

Hey, as I wanted to do the subs together with the LaScalas, it took me a while to make the sub enclosures (lots of delay on the LaScalas..), but this week they're gonna be finished! Decided to make the subs in the wood working atelier as they have awesome tools! See below: awesome tool for the perfect cut out! Exciting times ahead !

 

 

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I'm not exactly sure.  If the Google translation is reliable, it lists "sound absorption" as an application, but if not clear how effective it is.  Presumably it is an open-cell foam? The foam must be open cell and allow air to pass through for it to absorb sound well.  The right amount of flow resistance is also important, but that kind of information is rarely published.  Without test data, the best you can do is take the manufacturers word for it.  At 3 cm thin, you'll definitely want at least a few layers of it.

The product I use comes from http://www.thefoamfactory.com, which is located here in the States. They provide engineering data and the prices aren't bad.  The stuff doesn't absorb as well as fiberglass or rockwool products, but for the price (including shipping!) and lack of irritating fibers, it was a good fit for me.  Perhaps you can find something similar?  Or it's possible the product you linked to will work fine.

Some people use materials like denim scrap or Polyfil with satisfactory results and lower cost than the above products.  YMMV.

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I have ordered something that should work. Hopefully enough for both, but definetely for at least one. Doing the bracing know (cant seem to upload any pictures..). Also ordered an iNuke NU6000 (was only 200eu so just decided to go for it. I have some other uses for it if I don't like it enough for the ultra low bass).

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I just cut all the bracing, and noticed I cut one too short. I'm out of wood now, so.. Go buy some new, or would this be OK considering a lot of glue, and a thigh screw to attach it to the wall. @SME

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Put some PL premium or a bunch of wood glue in there and screw it through the wall. Should be fine. 

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Very busy last few days, and also been spending most my time on setting up the 5x LaScalas. First 3x LaScalas are setup, and although they need some tweaking DSP wise, they already sound amazing! Bracing for the first sub is done, and the filling has arrived. Some more questions about how to apply this. Do I cut up the sheets so I can apply some to every inch of the walls? Or is it OK if "most" of the walls are covered? And I assume every wall has to be covered?  The sheets are 1" thick. So 3 layers? Or would 2 also work? 

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Cover as much as you can.  Definitely do at least 3" thick where you can.  A full 4" may be even better.  Also make certain that the material is secured to the walls so that it doesn't interfere with the driver.

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Okay, will do. How do I know if I covered enough and used a tick enough layer? I mean, how would this sound if I didnt do this properly?

 

 

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If not done properly, the sound may be colored or boxy, especially when the sub is driven harder.  The stuffing mainly helps suppress noise and distortion overtones, which may otherwise be amplified by the rear-wave resonance and/or modal cavity resonances inside the enclosure and can leak out through the enclosure walls or the cone itself.

The thickness influences how low the absorption works.  For a material with good absorption properties, a 4" thick layer should absorb very well down into the 200s and should be sufficient to substantially attenuate sounds in the 100s too.

Resonances that are bad enough may also appear in an impedance measurement, but that depends on other factors too like how much inductance there is to potentially hide such resonances.  And anyway, by the time they are bad enough to show up in the impedance, they are usually quite audible in my experience.  YMMV.

Edit: Just a note that a peak in impedance from a resonance won't necessarily be audible unless you are running the sub at the affected frequencies.  Still, you want to suppress such resonances as much as possible for the best sound.

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35 minutes ago, SME said:

If not done properly, the sound may be colored or boxy, especially when the sub is driven harder.  The stuffing mainly helps suppress noise and distortion overtones, which may otherwise be amplified by the rear-wave resonance and/or modal cavity resonances inside the enclosure and can leak out through the enclosure walls or the cone itself.

The thickness influences how low the absorption works.  For a material with good absorption properties, a 4" thick layer should absorb very well down into the 200s and should be sufficient to substantially attenuate sounds in the 100s too.

Resonances that are bad enough may also appear in an impedance measurement, but that depends on other factors too like how much inductance there is to potentially hide such resonances.  And anyway, by the time they are bad enough to show up in the impedance, they are usually quite audible in my experience.  YMMV.

Edit: Just a note that a peak in impedance from a resonance won't necessarily be audible unless you are running the sub at the affected frequencies.  Still, you want to suppress such resonances as much as possible for the best sound.

I ordered 8 packs of filling, so 8x2 sheets measuring 20"x15". I'm not sure how much place the bracing is gonna take, but I'll figure that out when applying it. Was hoping those 16 sheets would be enough for both subs, but that doesnt seem to be the case (was not sure how big/thick they were when I ordered them). Will fill it up and see how much I need. Would it be a smart idea to just screw (and maybe apply a thin layer of wood glue on the outer margins) the top on it. If I hear it sounds good, I take it off again and use absurd amounts of glue to make sure it's truely air tight. Also, what would be a good way to apply it? It seems the stapler I have dont really have the power to perforate the MDF.. I might use some very shallow screws (or nails if I can find those).

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I used spray adhesive with the foam I bought.  That may be a bit messy if you have to layer the foam.  I'm not sure wood glue would work well either.  Shallow screws or nails ought to be fine.  It might be helpful to use washers or something so they hold the material without ripping through it.

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Bracing: I ended up trying a few different things. 

 

1: screws. Screw them! Loads and loads of work to make sure the material didnt get cauught in the screw when screwing it in. More than once I ended up swirling the whole piece at top speeds like a helicopter trying to lift up. Ended up ripping through the screws that were already in place.. Did use something (not sure how to translate) called a ring, to keep the material in place. That seemed to do the trick. Second layer I was able to staple to the first one attached with the screws. Conclusion: it would have worked, but would have taken a lot lot of time. 

 

2: Wood Glue: it worked! If spread enough it firmly keeps the material in place. I not only spread it, but also made sure it was absorbed a bit. I used weights and clamps to keep it tight to the walls till it dried. Second layer I attached with staples (and a layer of glue in between for good measure).

 

3: Staples: although the MDF is way to sturdy to pierce with regular staples, I found out that the plywood I used for bracing was pierceable. After (and during the process) glueing I stapled all the material to the adjacent bracings. 

 

All in all I think it worked out fine! The picture is not of the final stage though, I added some more after the picture.

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