First DIY design, 3-way split tower

[Pibborando]

Hello. I have recently become interested in speaker DIY, mostly the design side (I am an artist... in training) even though I am a student and probably won't be able to fund any serious project for a few years.

Anyway, that hasn't stopped me from atleast sketchin/modeling some ideas. Here is my design for a 3-way tower, split into seperate cabinets for the woofer and mid/tweeter. I want to keep the drivers on the affordable side (best bang for your buck deal) so I'm thinking Dayton RS225 8" woofer, Peerless Exclusive 5.5" mid and Vifa XT19 tweeter (although suggestions are much more than welcome).

I don't have a CAD program so I used Lightwave 3D to flesh out the shape and size. I put a dude next to it, that I modeled, for size reference.

Image not available

Yes, I have seen Avalon speakers

How hard/expensive would making a cabinet like that be? What tools would I need?

I was also thinking about a downward firing port at the bottom of the woofer box.

Can I get advice on the design, bracing tips, volume considerations, crossovers, etc. I'm pretty much a noob at the technical side, I just like design... and nice sounding speakers! :T

[ThomasW]

Sorry but it's a little problematic getting people to spend time and energy on what's essentually vaporware.


So we don't have to reinvent the wheel.....

https://www.htguide.com/forum/showthread.php?t=23683

https://www.htguide.com/forum/showthread.php?t=3430

https://www.htguide.com/forum/showthread.php?t=19193&page=2&pp=35

You might want to buy or checkout from the library, "Speaker Building 201" and "The Loudspeaker Design Cookbook"

For free you can download Jon's speaker design article

https://www.htguide.com/forum/showthread.php?t=22862

And FWIW there are other members here owning those valuable framed sheepskin rewards for having trained and educated in Fine Art, Chris D'Alessio(CJD) and I are but a couple examples ...

[Chris7]

Welcome to HTGuide.

Generally, it's not useful to design how a speaker enclosure looks without understanding the engineering impact of your design choices. For instance, in John's M8ta design, the angle of the front baffle was specifically chosen to set the tweeter's acoustic center a certain distance back in order to make the crossover cleaner. Similarly, the shape was modeled and chosen from various shapes in order to minimize diffraction artifacts with the specific crossover point he had chosen. Yes, his cabinet looks really nice, but that's a side-effect, not the starting point. If you design the cabinet first, you can force yourself into impossible or undesirable engineering decisions. In a similar vein, you don't normally get to choose how tall your cabinet is going to be. It is determined by the listening axis you have designed the crossover for (to be specific, generally the halfway point between the tweeter and midwoofer needs to be at ear level when you are sitting). Also, the volume of your woofer cabinet needs to be calculated based on the driver's parameters, not just chosen arbitrarily.

I don't mean to discourage you, but ThomasW's suggestions for books are a good starting point. Once you understand some of the basics, you can work at developing sketches for designs you like that intersect with the engineering fundamentals.

Also, from the tone of your post I'm guessing that you don't have a lot of woodworking experience. With a complicated cabinet design like the one you posted, you're looking at a lot of work. That's not a beginner's carpentry project, and it's not something you can farm out to a cabinetmaker for a reasonable (inexpensive) cost. I know you want to do it all the first time, but you should really build a regular box design that someone else has developed to see how much work is involved with just that.

[ThomasW]

Some tool threads, there are more like these..........

https://www.htguide.com/forum/showthread.php?t=17998&highlight=tools

https://www.htguide.com/forum/showthread.php?t=21439&highlight=tools

https://www.htguide.com/forum/showthread.php?t=15711&highlight=tools

[cotdt]

Roman's design is very similar, using a choice of the L22 or RS225 as the woofer, the Peerless Exclusive 4" as midrange and the Vifa XT19 as the tweeter:

http://www.rjbaudio.com/AlpheusMkII/alpheusmkii.html

[Pibborando]

Ok, thanks guys. I know I probably sounded pretty naive there. Well, I guess I was (am), but just because this is exciting to me.

I realize that I probably (definitely) will not be able to accomplish such a complex and lofty design my first go. I guess I just needed the reality check. Anyway, thanks ThomasW for the links. I am reading Jon's article now.

So what would be the proper steps to designing a good speaker? I'm guessing 1) choose desired configuration (2-way, 3-way, WT, WMT, WMTM, etc.), 2) pick drivers with budget and performance in mind, 3) calculate volume of enclosures based on driver specs, 4) calculate best height/positioning for drivers, 5) design enclosure

As for the crossovers, do you pick the crossover points first, then pick the drivers that suite those points, or pick the drivers then design the crossover around them?

Also, do the optimal volume specs for the drivers change if it's ported vs closed? Ports are another whole aspect I know very little about. I'll try to read as much litterature as I can.

I want to learn as much as possible. Thanks.

edit: Do you think it would be a good way to get my feet wet by building a simple 2-way bookshelf, gaining knowlege and experience from that, then later, building a woofer box with a new crossover, incorporating the top box as well?

[Dennis H]

As for the crossovers, do you pick the crossover points first, then pick the drivers that suite those points, or pick the drivers then design the crossover around them?

A bit of both. Start with driver selection. Pick drivers that will work well together. Taking a simple 2-way example, the woofer can play cleanly high enough and the tweeter can play cleanly low enough. Once you know the drivers have a clean response range that overlaps, you can start designing a crossover to blend the two, taking into account the properties of both drivers. Bottom line, the crossover is the heart and soul of the speaker. So-so drivers with a great crossover will sound much better than great drivers with a so-so crossover.

[cjd]

Speaker design is a progression of system integration. You can't pick drivers without understanding your crossover goals, volume goals, budget goals, you can't randomly pick crossovers without understanding budget or driver, you can't... it's all integrated. Change crossover, you can change your box tuning.

I start with drivers, I think you have to. But it's a family, where you already understand some notion of what box design will result, what crossover points baffle layout will allow, what crossover points drivers will work with...

It's a multi-year process for most people to really start to be where they think they understand what they're doing, at which point someone comes along and points out something you'd never thought of before and you're back to realizing you still have a long way to go.

If you want to take that multi-year journey, there are many approaches. JonW recently started a thread on his process of jumping in. I think when he decided to go the "design your own" he understood things you're asking questions about. It's a great bunch of fun, but not without headaches.

If you want to have fun doing box design and assembling and contributing, find a more experienced (crossover) designer willing to work with you. Somewhere along the way someone will need to take accurate measurements which means completed box with drivers...

C

[Jed]

That's a nice looking design.

Post more pics with dimensions and you might peak my interest. I've got some HDS tweeters, Usher 8948a, and Scan Speak 25Ws that will need a home.

I like how your design combines elements of the Wilson Watt, and Avalon.

I'd model the bass cabinet at 60L, and top cabinet around 12L.

You might consider the drivers I'm using or substitute RS270s for the Scan Speaks if you don't want to spend that much.

Just a thought,

Jed

[Pibborando]

Thanks for the kind words Jed. I came up with a new design for the mid/tweeter box but could be a standalone bookshelf with a crossover of its own if you wanted.

Image not available

Based the dimensions around the Vifa XT19 (3.7" D) and Peerless Exclusive 5.5" (6" D). The internal volume is about 10-11L and designed to use a 2" rear port tube. There's a little shelf about 4x7" where you could put the crossover (big enough?). The drivers would be recessed slighly so a felt matt could be put over them (covering the screws of the woofer, and most of the waveguide of the tweeter). Is it felt, or is there some other material used for this?

The lower woofer box could be built later after I prove myself with this project.

What do you think?

edit: Anyone know how to get AutoCAD to just export an image of the drawing instead of me having to screenshot the window?

edit2: Updated image. Added screw holes (bored) and adjusted the size of the tweeter cutout (3.7" to 3.75" to leave a bit of room just in case)

[Jed]

The lower woofer box could be built later after I prove myself with this project.

What do you think?

How set are you on using the drivers you mentioned? Honestly, for your first design, if you plan on using measurements, you are going to need a lot of help and guidance.

We could document progress here.

I'll offer to help you out with this design, but it can only work if we use the same drivers. I picked the HDS and Ushers for their excellent price/performance ratio. Plus, the Ushers are onsale at the moment.

Driver selection is the first step, so if we can agree to use the same drivers this may be a very nice learning experience for the both of us.

I realize you might want to venture out on your own, but without the measurements you're going to be in the dark, especially with the unpredictable baffle diffraction characteristics of your cabinet design.

Jed

[cjd]

XT19 to 5.5 Peerless may be a bit of a stretch - center to center spacing mayu also be (2400Hz spacing). I'll have to double check the specs on the XT19 to be absolutely sure...

Have to run unibox numbers to see if box volume is sufficient. If someone else is dong this, remember to include the additional series impedance that you'll gain from inductors in the circuit.

[ThomasW]

We could document progress here.

even though I am a student and probably won't be able to fund any serious project for a few years.

Might be a good idea to wait until he's actually ready to build the speaker. A lot can change with regard to a design in a period of years....

[Jed]

Might be a good idea to wait until he's actually ready to build the speaker. A lot can change with regard to a design in a period of years....

missed that

[Pibborando]

How set are you on using the drivers you mentioned? Honestly, for your first design, if you plan on using measurements, you are going to need a lot of help and guidance.

Not set at all. That's why I'm asking for help. Since you have those drivers availible (and I'm assuming can take measurments?) I would be more than okay with changing things to incorporate them.

The Usher 8948A, aren't those 7"? Did you want to use that as the woofer, or mids? Oh, just saw that the SS 25W is a 10". Well, I guess mids for the Usher then?

And the HDS tweeter, something like this ? Or is that a brand?

[Jed]

Not set at all. That's why I'm asking for help. Since you have those drivers availible (and I'm assuming can take measurments?) I would be more than okay with changing things to incorporate them.

The Usher 8948A, aren't those 7"? Did you want to use that as the woofer, or mids? Oh, just saw that the SS 25W is a 10". Well, I guess mids for the Usher then?

And the HDS tweeter, something like this ? Or is that a brand?

You can see some of my designs in my 3-way thread. I can take measurements, yes.

If you are ready to build, say in a few months I can help you. You see, I'm going to work on a bunch of designs this summer... well 2, actually. A 3-way with Visaton MHT12, Accuton C-79, and Aura NS10-513, and another system using the Peerless HDS tweeter, Usher 8948a mid, and Scan Speak 25W.

I was going to work with an Avalon style box for the first 3-way and a Wilson style for the second. Your box is a nice combination of both, so it might look nice with the HDS, Usher, Scan Speak combo. If the Scans are out of your price range we could try a Dayton RS270 or RS225 as a replacement woofer.

That's what I'll be doing, if you want to provide cabinet plans and see how I do things with design from point A to completion, let me know.

As Thomas pointed out however, you might not have the means to do that right now, and that is ok too.

Regards,

Jed

[Pibborando]

Saw your first "Wilson" style 3-way design in your thread. Looks very nice... I want to say... "noble" or "distinguished."

I've been working on my design. I have designed the top box on this one to use the Peerless HDS tweeter and Exclusive 5.5" midrange. The bottom will use the Dayton Reference 8" woofer (for value).

Image not available

Top box is right around 0.25 cu/ft (which is the same as the Vas of the Exclusive, this is good right?), and the bottom is 1.5 cu/ft. I've been using WinISD to do some calculations and it looks like the port should be tuned to about 27Hz or 28Hz to get the flattest and deepest response. The thing is, if I use a 3" diameter port, it tells me that it needs to be over a foot long. This would put the inside opening right below the woofer. Is this ok, or will there be problems? If I use a 2" port, it can be about half as long but the "vent mach" is 0.19, which shows up as red. This is the air speed right? What issues are there when it's too high?

I can't find any decent looking ports that are 2.5" or 2.75" anywhere. Any ideas?

Also, do most people just screw their drivers straight onto the MDF (or recess they've routed out) or put some kind of thin foam or rubber "ring" between the driver and the cabinet to reduce vibrations?

edit: For dimensions, it's 10" wide and 41.5" tall over all. The "sweet spot" between the mid and tweeter is right at 3' which is my own ear height when sitting on my couch.

[Jed]

Top box is right around 0.25 cu/ft (which is the same as the Vas of the Exclusive, this is good right?), and the bottom is 1.5 cu/ft.

No, you have to model using using the TS parameters in a program like unibox, which is free. Ask yourself these questions:

How low will I crossover the midrange unit?

Will the box volume contribute to the low end extention in passband response or will I use an electrical solution and oversized box?

How will dampening the box influence the response?

Will I go with a sealed or ported boxed midrange to meet said objectives?

Have I modeled the diffraction effects to see optimal layout of drivers on the baffle using software like the EDGE?

I've been using WinISD to do some calculations and it looks like the port should be tuned to about 27Hz or 28Hz to get the flattest and deepest response.

RS225 likes about 60L tuned to 28HZ or so.

The thing is, if I use a 3" diameter port, it tells me that it needs to be over a foot long. This would put the inside opening right below the woofer. Is this ok, or will there be problems? If I use a 2" port, it can be about half as long but the "vent mach" is 0.19, which shows up as red. This is the air speed right? What issues are there when it's too high?

Use a 3" port flared like the Precision Ports at PE.

Also, do most people just screw their drivers straight onto the MDF (or recess they've routed out) or put some kind of thin foam or rubber "ring" between the driver and the cabinet to reduce vibrations?

I flush mount the flanges using a router, then gasket tape on the frame.


Here's a recommendation- collaborate with someone on the board who has more experience and learn along the way. When will you be ready to build?

[Pibborando]

Ok, thanks for the tips Jed. Been thinking about this some more and had another question. Whipped up two designs to ask, which one would be 1) easier/cheaper to build, 2) easier to design a crossover for, and 3) perform better as a full range tower?

Sketch: Image not available

These were just to get the basic shapes and ideas down. Haven't begun to think about exact dimensions. Not sure why I used a TS line for the second and not the first. I suppose the first design could also use a TS line and the second could also use a port... so that factors into the complexity of the design and performance.

From what I understand, a bass-reflex cabinet can get you more low output, but falls off sharply, where as a (properly tuned) TS line won't output as much but the bass will extend much deeper?

First design was inspired by the NatP and Acoustic Zen Adagio (wish I had the means to make sexy curved cabinets like those). Second was a continuation of my previous design and also inspired by this .

edit: The maker of the Adagio, in an interview, talked about the importance of underhung voice coils and how they have much less low end distortion than traditional drivers. There's those Dynavox woofers on PE which seem to use an underhung design. Anyone heard them?

[JonMarsh]

From what I understand, a bass-reflex cabinet can get you more low output, but falls off sharply, where as a (properly tuned) TS line won't output as much but the bass will extend much deeper?

Ah, that comes under the category of no generalization is worth a dang, including this one.

Martin King's TQWT "TL" is in fact just a special variation of a bass reflex; in general, (oops!), you can design a relatively low Q reflex with good extension and tight in room response just by using the right design targets and driver- the key, in my opinion, is shooting for a tuning at F6 that has a slow slope downwards from 100 Hz, so that the room boundary re-inforcement results in fairly flat in room response, and of course no peaking at the box tuning.

An example is the M12ta three way design study ported bass reflex alignment, using the Aurasound NS12-513A in 76 liter enclosure tuned to 18 Hz, as shown below. (yeah, the NS12 is an underhung motor, BTW).



I've done this kind of alignment numerous times in ported systems, including the M8ta. I used to build conventional TL's in the 70's, and this is a lot less hassle. But that's not to say a conventional TL couldn't be fun... they're just rather big. ;W

[Pibborando]

Ok, thanks Jon. I wasn't thinking about room gain before (tried to get the deepest response in WinISD, which would probably lead to big peaks in an actual room). So it looks like a standard port with the right tuning would be the simplest option, since TLs look quite complicated to design and build right.

How do you feel about front vs rear porting? How does the delay from the reflected wave (off the rear wall) from the port affect the sound? I'd imagine you could lose a bit of clarity but would the soundstage deepen? If I don't have to worry about having to put my speakers right up against the wall, which would be the better option?

[Jed]

If I don't have to worry about having to put my speakers right up against the wall, which would be the better option?

Jon gave you the best option in his example with Aurasound NS12. If you shoot for the same targets as he did, with the gradual decline in response starting at 100HZ, you'll be golden. Though, depends on how much bass you want and how dead your room is. I prefer downfiring or rear firing.

Looks like you are exploring a lot of design concepts at this point, which is good.

Jed

[DS-21]

Wait a minute...since when does Unibox work in Excel for OSX? Those buttons, icons, and fonts look far to nice to be the Windows version of Excel.

[JonMarsh]

well, Unibox isn't fully funcitonal in Excel on the Mac, but a fair amount of it works, enought that a Unibox sheet with basic data entered can be examined, plotted, etc. The VBA parts don't work. My MacBook dual boots XP, and my MacBook Pro dual boots Vista; my Quad Core G5 PowerMac runs XP in Virtual PC.

The preferred porting in my opinion is

1 Downward firing- this is how the M8ta works, as well as the M12ta in construction. This also locates the port and driver in the configuration Martin King recommends for the so called TQWT TL using a conventional port. Does the best job of masking any midrange output, especially if downward firing into carpet.

2 Rear firing. Port output is primarily at tuning with a sloping decline as you go up in frequency until you hit the port resonances dictated by diameter and length. Better to direct that backwards than in your face, IMO.


Re location, the finished speakers should ALWAYS be away from the wall, with golden mean ratio dimensions from the woofer to the three closes boundaries (floor, rear wall, side wall), the Cardas layout guidelines are a good way to go if you can't caculate this stuff yourself.



See this post by Evil Twin for more on the theory and results behind that.

[Pibborando]

Ok... so I've been messin around in AutoCAD some more and I think maybe this would be a good design?

Images not available

Would use two Dayton RS180S-8 7" woofers and a Dayton RS28A-4 tweeter in a D'Appolito configuration. Drivers aligned to their acoustic centers.

9" wide (7" internal), 14" deep (11.5" internal), and 46" tall (40" cabinet + 6" plinth, 37" internal), so right around 50L. Does stuffing increase or decrease the perceived volume? Would use a 10" long, rear firing flared port (about 29Hz tuning).

I would guess I could use a crossover similar to the NatP, but adjust it because of the offset drive mounting?

Also, can the port be braced along the tube for support or does it need room all around it to work properly?

Does this look good at all?

[Jed]

Ok... so I've been messin around in AutoCAD some more and I think maybe this would be a good design?

Images not available

Would use two Dayton RS180S-8 7" woofers and a Dayton RS28A-4 tweeter in a D'Appolito configuration. Drivers aligned to their acoustic centers.

9" wide (7" internal), 14" deep (11.5" internal), and 46" tall (40" cabinet + 6" plinth, 37" internal), so right around 50L. Does stuffing increase or decrease the perceived volume? Would use a 10" long, rear firing flared port (about 29Hz tuning).

I would guess I could use a crossover similar to the NatP, but adjust it because of the offset drive mounting?

Also, can the port be braced along the tube for support or does it need room all around it to work properly?

Does this look good at all?

Other than for aesthetics, I don't see any benefit of modifying Jon's design, other than to try something out to see what will happen or if you plan on aligning the acoustic centers to fascilitate a 2nd order design with a non-electrical solution for phase alignment. I still wouldn't recommend 2nd order slopes because of the inherent cone breakups of the RS metal cones. So, if you really wanna get into design, first download the FRD tools and play around with Speakerworkshop to get some experience with crossover design, so that when you are ready, you can take measurements of your own. These deviations you make will undoubtedly require major crossover renovations.

Plan B- Build it to specs, test it out, measure it, simulate the crossover to gain experience on crossovers and how they work, then tackle the custom stuff.

Just my 2 pennies.

[johngalt47]

What ever happened to this project?

[ruseriousclark]

Who is John Galt?

[---k---]

Who is John Galt?

Find out April 15th.

[ruseriousclark]

Find out April 15th.

Read that book twice in the past two years, waiting for the movie to come out. Setting is going to be different though and I'm afraid it will suffer as a result. Hope its a four hour flick... or done it parts. That's a lot of subject matter to build up and conclude in 2 hours.

[---k---]

April 15th is Part 1 of 3. I've seen some good reviews of it. Better stop thought now, because we're thread crapping and off topic. :E