Scanspeak 32W/4878T Subwoofer build w/ passive radiators Questions....

[Lagarto]

Hi all. First post here.

I build high end turntables. My profession is in audio. Turntables. I built my first speakers when I was in my teens.

I am building a new subwoofer now, using the Scanspeak 32W/4878T subwoofer driver. I have one of the Scanspeak 30W//00 passive radiators. I have been researching this, and I see that 2 opposed PR's might be best.


I am aiming for:

Sound quality
Ability to play low
one cabinet is ideal, but if needed, another can be added. I think this one will be enough.

I know there are less expensive drivers. And also, that the Discovery drivers are less$$$$ I have the Revelator in hand.


I have a full woodshop here, and also full metalworking capability, so things like dialing in the weights for the PR's is no problem. Except for the measuring and knowing how much weight to use!

I have a Hypex FA501 plate amp

I am planning on 1" baltic Birch ply, well braced. Building any cabinet is no problem.

I have never measured any of my speaker builds, but it is time now.

Do I need WinISD?

Probably REW, yes. And the UMIK.

I have read from a couple of people on this forum of their Scanspeak 32w builds.

Are passive radiators a good way to go? I have one already, and read that 2, opposed, is good.

I would love some input on how to approach this, any thoughts.

This is mainly for home theater, but also for music. Mostly, my 2 way speakers have been great for music, but some types of music, bass is always good. I currently have a Linn 10" subwoofer, and it works. It is weak, though, I know it.

I am a noob, here, and am here to learn.

This will be a sealed box with PR's, not sure yet about box internal volume. From what I read, around 40l with allowance for the PR's may work well, with some adjustments in the DSP of the Hypex amp.

TIA.

 

[levimax]

UMIK-1 is OK for frequency response measurements but if you are going to be doing serious speaker design, for time domain measurements the UMIK-2 is better because it has a built in clock instead of relying on the USB bus. WinISD is good for subs, VitruixCad is also free and good and covers all speakers but it has a steep learning curve. Passive radiators are similar to ports but more expensive. For your first sub sealed is much easier than ported or passive radiators. Picking drivers first is one approach but setting design goals and then using CAD to design enclosure can lead you to required driver specs and you may be able find a cheaper driver that works. Lots of ways to go, enjoy the journey.

 

[Lagarto]

Thank you. Th eUMIK 2 looks like the option. I was already planning on getting a UMIk, as I am slowly looking into Dirac so that when the Black Friday sale comes around again, I should be ready to use it for my HT setup. Setting up Atmos speakers currently, and working on some broadband and bass traps.

This is not my first subwoofer, nor speaker project. I have built quite a few speakers, for a non-professional speaker builder. Where I am lacking in in measuring. This is also my first adventure into PR's. I need to dive into the measurements, as I also need to learn to use my HP spectrum analyzer for other audio use.

I see there is a learning curve in front of me, but I am not intimidated. Time is on my side, and taking all of this one step at a time will get me where I want to go. Lots of little things to learn. From my view, it is mostly in learning 'what questions to ask', which is why I signed up for this forum. I have been a lurker here for years, with no account. I am aware that this is a good group of people here.

I also plan some 3 way speakers from Troel's site, based on the Ellipticor midange, Revelator tweeter and woofer, and staying within the same 'genes' is part of the reasoning behind going with the 32W Scanspeak subwoofer. Also, Scanspeak is known to be among the best driver manufacturers, albiet at a price. I have learned that most things in audio have subtle differences in SQ, and especially speaker drivers. The 32W is already in my shop, along with one of the 30w PR's.

From what I have been reading so far, the one PR is close to working, in terms of displacement and excursion, but I think 2 will be better. I plan on modeling this beforehand, which is also why I am here. This is new for me and I will have questions. The displaceement (sd x Xmax) of the 32W driver is slightly more than the PR, and the excursion of the PR is 28 with the Xmax of the 32W being 14mm, so in my current level of understanding, likely 2 PR's will be better. For other reasons, too, from what I am reading. I have 3 lathes here, so turning custom weights for the PR's is easy. Not sure the level of precision in weight is beneficial for tuning, but precision work is easy.

I spent several months looking at drivers for this sub, thinking. I selected this one because of the low fs, that it is ideal for a sealed box / smallish cabinet, and that it has relatively high power handling for a non- PA sub driver.

I am looking into Bass Box Pro, as it looks simple to learn, and am about to download WinISD, as it may do everything I need. I have a commercial account at Parts Express, so that saves some on cost for the BBP.

The actual building of this cabinet is easy, maybe a days work including making the router templaces for the PR's and the Hypex amp. The design portion of the build, I do not know how long that will take. I am not in a hurry. I think it is simpler than say, designing a 3 way speaker with crossovers.

I hear there is a little bit of a learning curve for the Hypex filter program, so that is right up with the measuring in terms of unknown for me, but it is on the menu.

I am here for guidance in learning to model the boxes, with the most likely design around 2 PR's. Suspecting that they will need some tuning. And then in learning to navigate the Hypex software and finally in using measurements to fine tune and verify my work. Currently, I am stuck with these drivers and will have to suffer through with them.

Attached are a couple of my past speaker priojects. The layered cabs are for Goto 15" drivers. I have built 16 of these cabs for a client. This is part of a really cool 3 way horn system. About $275k all in for 4 cabs with the top horns and drivers. The other pics are of one of my old PA's, some Punisher and Xtro's. Another are my current 2-way speakers that I have been enjoying for the past 10 years or so. They sound awesome, and this is on a very capable system. One of my other current projects, is making some sealed box Atmos speakers using the Jordan JX92 full range drivers. I have built a good number of different speakers with these drivers. I think they might work well for Atmos. They can be gorgeous sounding in the right cabinet.

 

[levimax]

Thank you. Th eUMIK 2 looks like the option. I was already planning on getting a UMIk, as I am slowly looking into Dirac so that when the Black Friday sale comes around again, I should be ready to use it for my HT setup. Setting up Atmos speakers currently, and working on some broadband and bass traps.

This is not my first subwoofer, nor speaker project. I have built quite a few speakers, for a non-professional speaker builder. Where I am lacking in in measuring. This is also my first adventure into PR's. I need to dive into the measurements, as I also need to learn to use my HP spectrum analyzer for other audio use.

I see there is a learning curve in front of me, but I am not intimidated. Time is on my side, and taking all of this one step at a time will get me where I want to go. Lots of little things to learn. From my view, it is mostly in learning 'what questions to ask', which is why I signed up for this forum. I have been a lurker here for years, with no account. I am aware that this is a good group of people here.

I also plan some 3 way speakers from Troel's site, based on the Ellipticor midange, Revelator tweeter and woofer, and staying within the same 'genes' is part of the reasoning behind going with the 32W Scanspeak subwoofer. Also, Scanspeak is known to be among the best driver manufacturers, albiet at a price. I have learned that most things in audio have subtle differences in SQ, and especially speaker drivers. The 32W is already in my shop, along with one of the 30w PR's.

From what I have been reading so far, the one PR is close to working, in terms of displacement and excursion, but I think 2 will be better. I plan on modeling this beforehand, which is also why I am here. This is new for me and I will have questions. The displaceement (sd x Xmax) of the 32W driver is slightly more than the PR, and the excursion of the PR is 28 with the Xmax of the 32W being 14mm, so in my current level of understanding, likely 2 PR's will be better. For other reasons, too, from what I am reading. I have 3 lathes here, so turning custom weights for the PR's is easy. Not sure the level of precision in weight is beneficial for tuning, but precision work is easy.

I spent several months looking at drivers for this sub, thinking. I selected this one because of the low fs, that it is ideal for a sealed box / smallish cabinet, and that it has relatively high power handling for a non- PA sub driver.

I am looking into Bass Box Pro, as it looks simple to learn, and am about to download WinISD, as it may do everything I need. I have a commercial account at Parts Express, so that saves some on cost for the BBP.

The actual building of this cabinet is easy, maybe a days work including making the router templaces for the PR's and the Hypex amp.

I hear there is a little bit of a learning curve for the Hypex filter program, so that is right up with the measuring in terms of unknown for me, but it is on the menu.

I am here for guidance in learning to model the boxes, with the most likely design around 2 PR's. Suspecting that they will need some tuning. And then in learning to navigate the Hypex software and finally in using measurements to fine tune and verify my work. Currently, I am stuck with these drivers and will have to suffer through with them.

Attached are a couple of my past speaker priojects. The layered cabs are for Goto 15" drivers. I have built 16 of these cabs for a client. This is part of a really cool 3 way horn system. About $275k all in for 4 cabs with the top horns and drivers. The other pics are of one of my old PA's, some Punisher and Xtro's. Another are my current 2-way speakers that I have been enjoying for the past 10 years or so. They sound awesome, and this is on a very capable system. One of my other current projects, is making some sealed box Atmos speakers using the Jordan JX92 full range drivers. I have built a good number of different speakers with these drivers. I think they might work well for Atmos. They can be gorgeous sounding in the right cabinet.

Sounds like you well on your way. If you want to learn about measurements and CAD and aren't afraid of a learning curve, VituixCAD has an exhaustive document that takes you through every step of speaker design using VituixCAD including measuring the raw drivers (the first step). https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html

It may be overkill for a sub but it is a great document and a powerful program.

 

[Lagarto]

Sounds like you well on your way. If you want to learn about measurements and CAD and aren't afraid of a learning curve, VituixCAD has an exhaustive document that takes you through every step of speaker design using VituixCAD including measuring the raw drivers (the first step). https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_help_20.html

It may be overkill for a sub but it is a great document and a powerful program.

Is the VituixCAd a good tool for determining a starting point for PR weights?

It may be overkill for this sub, but if it is not too difficult to learn, understanding how to use something like this will 'unlock' a whole world for me.

Also, will I be needing to take measurements directly into either VituixCAD, WinISD, or even the Bass Box Pro? Or are these mainly modeling programs? I think REW is part of what is needed for measuring, but am still unsure. One of my current challenges is that I can see that these programs run on Windows, and my only Windows laptop is ancient and does not have a battery. It still works. My main workstation is Windows, but it is in the other room.

Also, how critical is an anechoic room for taking measurements, say, for this sub? How far off am I in thinking that I should be able to get pretty close on the cabinet design with the modeling software, and that in using the DSP in the Hypex amp, and in placement, closing the rest of the gap can and should be done 'in-situ'?

 

[DVDdoug]

that it is ideal for a sealed box / smallish cabinet,

As you may know, passive radiators are more like ported speakers than sealed. WinISD or Bass Box will help you with all of the trade-offs.

With a truly sealed design you'll normally "need" some EQ to extend the deep bass. Ported designs can usually go lower (before considering EQ) but they don't benefit as much from EQ boost because below the tuning frequency the woofer (and PR) tend to "flop around" with a lot of movement but not much sound.

This post shows the general trade-offs between sealed and ported. The ported box cuts-off lower but it has a steeper roll-off so at some point the curves cross. "Pro" subwoofers used live and in dance clubs are usually large ported boxes tuned to go-down around 40Hz. This allows for efficiency and high SPL to fill a large venue with bass you can feel in your body. Home subwoofers are often smaller sealed boxes with EQ and lots of amplifier power to fill the smaller room with bass that goes lower.

Or are these mainly modeling programs? I think REW is part of what is needed for measuring,

The only one I've used is WinISD and it's only for modeling. REW is "the standard" for measuring speakers/rooms. (Unless you have a Klippel setup like our host Amir, which gets-around not having an anechoic chamber.)

Also, how critical is an anechoic room for taking measurments, say, for this sub?

If you measure the performance of the subwoofer, do it outdoors. Then, you'll probably want to measure and EQ again once it's in the room. Once you're in a room,
Room Modes dominate.