Small 2 way "in desk" speaker build suggestions

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I'm in the early planning stages of building myself my own desk from scratch. The plan right now is to make it a sort of "command and control center" for office, music, and computer gaming purposes, with a focus on integrating as much "techie" gear as possible.

Here's the MSPaint concept drawing I've come up with so far:
An externally hosted image should be here but it was not working when we last tested it.


So the idea is to integrate a relatively inexpensive 2 way sealed speaker system. The front baffle will be angled however I want. I can put it dead center at the listener, upward, outward, etc. as the driver's might call for. One of the biggest concerns is a mid/woofer that's relatively small in diameter. The corner trapezoidal pieces can't dominate the desk space. Also relatively important is that they don't interfere with USBs, headphone jacks, power and reset buttons for an integrated computer, or any other electronics that may go nearby. I can shield the other plugs and switches with copper sheeting if it proves necessary.

One thing that's important to note is that I plan to mount a swivel arm monitor attachment at the same place that the left speaker is pictured. There's a small cutaway that might not be too clear. I can play with the dimensions, but it's important to note that it will be mounted in that area. It's approximately 5x4x4" and will encroach on the usable volume behind the speakers.

The plan is to power them with an existing logitech subwoofer plate amp that's capable of about 50 watts RMS x 4 channels (it started it's life as a logitech z560 HTIB type 4.1 setup). What I don't know is the rated impedence, but I'm assuming 6 or 8 ohms. I'm only going with a 2 channel stereo integrated system plus subwoofer behind the piece labeled "computer" in the drawing above. I drew in a circle for it's position. I might find some way of adding rear surrounds, but for now that's not in the equation as my desk "floats" in the middle of a rather large room. Small business. 4 workstations in one house. I'm in the middle of the living room behind a sofa staring at my big screen TV.

This will be my first DIY speaker project. I know that with my space and position constraints I'm not going to be able to get extreme SQ out of this setup, but I've got the subwoofer that's crossed relatively high (around 120 hz I'm guessing), so low end extension isn't a pressing concern. If I can get by with a 5" class mid/woofer that would be swell. I can throw out 7"+ woofers, but if there's something in the 6-6.5" class that can handle small sealed volumes I'd consider it.

I'm aware that this is a form over function design. The desk is the project, but I'm an amateur audio enthusiast (at least until I graduate).

A premade kit is a plus since it would be my first DIY speaker build. I'm a 2nd/3rd year EE undergrad so I have a sophomoric understanding of circuit diagrams and components (for the crossover).

In summation:
1. Small volume MT sealed design
2. Small mid/woofer
3. Power handling <= 50 watts RMS at 6/8 ohms
4. Shielded?
5. Subwoofer crossed at ~120 hz
6. Primary focus of imaging and clarity, not power handling
7. Computer games, high rip rate audio CDs, Netflix style movies as an afterthought.
8. Budget is <$200, but I've got some money set aside I can tap into if it's worth it.

I must admit that this logitech setup is my reference for good sounding speakers as sad as that may sound. I've got $4000+ wholesale cost in car audio gear and sound treatment in my truck (not a boom box) and this $150 logitech box set sounds better at moderate listening levels. I've had them for nearly 10 years and haven't heard better computer speakers yet.

Any help, suggestions, or links would be much appreciated!

Thanks gang!
 
hmmm....very interesting idea... ;)

Have you considered looking at some small full-ranges, eg. Fountek fr88 or fr89? (one of the best 3'' full-ranges, was $29 before all this price rise) This way you won't be struggling for volume, and you also get relatively good "imaging" and no issues with woofer/tweeter spacing. Acoustic effects when the drivers are so close to the desk surface; this may effect imaging, although they are angled upwards, which helps. :)

Given your sub's 120Hz crossover, want of small volume and # 6.), a full range driver may suit your needs more and will be easier to implement. This is just what I think...if you want to go with a two way and larger drivers, then feel free to do/say so... ;)
 
I appreciate the suggestion.

I am inclined to lean toward a woofer/tweeter 2 way setup for the silly reason that it is more aesthetically pleasing to the untrained observer. Part of the build is to say "look at that! Isn't it awesome". If the consensus is that a fullrange is best, my current desktop set are full range ported. I know it can produce some really good results. Another minor nit-pick with fullrange is that I wont really have to do much DIY constructing. This is both a results and an experience build. Since it's my first build, I'm trying to familiarize myself some with the process, and a fullrange doesn't offer a whole lot of growing potential (if that makes sense).

In other words, I'd like to have to assemble a passive crossover.

But definitely thanks for the suggestion!
 
Try a pair of the 5" SEAS coaxials
Seas Prestige L12RE/XFC (H1602) 5" Alum/Fabric Coaxial: Madisound Speaker Store

Will save some space and provides all you requested...including the desire to build some XO's.......There's a published XO from seas linked at the bottom if it makes life any easier. Coax's in the nearfield are really a thing to behold.

I appreciate the suggestion, but I'm fairly set on a 2 way woofer/tweeter configuration simply for the visual appeal, though two of you have now told me a full-range or coaxial point source sort of arrangement is best.

Also, please help me understand this. My understanding is a good metric for determining a good sealed woofer is to take Fs and divide by Qes. If the result falls under 50, it's a good sealed woofer. 50-100 is decent at both, and north of 100 is best ported. That Seas comes up around 166 using that formula. I like the Vas, but I'm not sure that setup will work for me. Again, I may not be getting the concept so feel free to correct me.

edit: Or have I switched it entirely?
 
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If you like the idea of a coax...

please do yourself a favour and check
ApexJr. out. The M&K coaxials are inexpensive ($14.95 ea.) and very good (and not bad looking either). I have 2 pairs of these drivers: one pair retrofitted to a small pair of "Teac" loudspeakers (the ones that came with the Reference 100 mini system of about 12-14 years ago). and one pair in a set of Pluto inspired loudspeakers.

The "Pluto (Siegfried Linkwitz design) loudspeaker wannabe" project that uses the recommended cross-over in a 39" long tube, and very little stuffing. Sounds too good to be true, but it is. Dirt simple to make.

Crossovers should be inexpensive to make (or buy a "bag of crossovers" from Steve at Apex Jr.). He is a small business and is a diyaudio.com sponsor. Only thing to be concerned at all about is that these drivers have no screw holes in the flanges, but some could easily be drilled.

Don't be put off by the lack of sensitivity of 87dB (2.83V/1m), you'll probably end up sitting at about 1 meter (39") away. 87dB is louder than you think. Add an inexpensive (but good) T-amp, kit or an integrated amp (hopefully a good one) that you may so have on hand, and you are a long ways along to good desktop performance.

The Teac enclosures are very small, at only 4-1/2" X 6-1/2" X 7-3/4" (outside dimensions). The walls are only 1/4" thick "hardboard" with a shiny laminate over top. They are a ported design, using a 1" diameter X 2" long rear port. I do not use them with a subwoofer at all and do not miss the bass. There is a strong sense of bass even if it doesn't measure very well.

Personally I would suggest building simple boxes, that way you can move them as desired, on your desktop or some Pluto inspired "tube" loudspeakers so they can be placed almost anywhere in the room.

Hope that helps.
 
Make sure the PC tower is isolated/ or the cabinet is very dense as the subwoofer vibrations won't do it any good. So it may be a better idea to move the tower to the other side where the rubbish (English please :p ) is. Just to make sure.

I'm on top of this one. I'm not actually going to have a typical PC case. I'm going to mount the motherboard inside that panel and plan on using rubber spacers on the mount for isolators. My hard drive is solid state, so shock isn't a concern with that one. Hopefully I'll be integrating a CD/DVD/Blu-ray drive into either the front of that panel, or up top folding into the speaker pods.

The plan is to make the desktop out of 1.5-2" hardwood (either cherry or oak depending on money and availability at my local lumber place). Then do all side panels in 3/4" matching wood. It'll be plyboard, but high quality. At least AB stock, and perhaps marine grade. I picked up a waterproofing method a few years back when refurbishing my jonboat that I may include as well before staining and polyurethaning. It involves adding several coats of a fiberglass resin and acetone blend liberally and allowing it to really soak in. Adds tons of strength and longevity.

The trash can is going to be shared with a person to my right. My current office depot job is only 46" wide. I'm making this desk 60" wide, so I've got to grant my coworker/housemate a usable trash can. I'll be tossing in a dedicated shredder and recycle bin too in a pull out drawer.
 
please do yourself a favour and check
ApexJr. out. The M&K coaxials are inexpensive ($14.95 ea.) and very good (and not bad looking either). I have 2 pairs of these drivers: one pair retrofitted to a small pair of "Teac" loudspeakers (the ones that came with the Reference 100 mini system of about 12-14 years ago). and one pair in a set of Pluto inspired loudspeakers.

The "Pluto (Siegfried Linkwitz design) loudspeaker wannabe" project that uses the recommended cross-over in a 39" long tube, and very little stuffing. Sounds too good to be true, but it is. Dirt simple to make.

Crossovers should be inexpensive to make (or buy a "bag of crossovers" from Steve at Apex Jr.). He is a small business and is a diyaudio.com sponsor. Only thing to be concerned at all about is that these drivers have no screw holes in the flanges, but some could easily be drilled.

Don't be put off by the lack of sensitivity of 87dB (2.83V/1m), you'll probably end up sitting at about 1 meter (39") away. 87dB is louder than you think. Add an inexpensive (but good) T-amp, kit or an integrated amp (hopefully a good one) that you may so have on hand, and you are a long ways along to good desktop performance.

The Teac enclosures are very small, at only 4-1/2" X 6-1/2" X 7-3/4" (outside dimensions). The walls are only 1/4" thick "hardboard" with a shiny laminate over top. They are a ported design, using a 1" diameter X 2" long rear port. I do not use them with a subwoofer at all and do not miss the bass. There is a strong sense of bass even if it doesn't measure very well.

Personally I would suggest building simple boxes, that way you can move them as desired, on your desktop or some Pluto inspired "tube" loudspeakers so they can be placed almost anywhere in the room.

Hope that helps.

That M&K looks great, but it calls for a ported box and it's coaxial. The speakers will absolutely be integrated into the desk as roughly shown in the picture above, and I'm trying to avoid a port. This desk is about packing as much into it as possible. I know this wont allow for positional adjustment, but I can optimize it exactly as I need to during construction.

I'm not worried about sensitivity or loudness. This wont be a THX home theater system. It's for medium to low volume level music and gaming. I'm going for flat response, which is probably hard enough with this design. It will probably behave something like a hybrid "in wall" and "bookshelf" stereo system.

The amp will at least start off as my existing logitech plate amp (on the back of the subwoofer), which is capable of around 50 watts RMS.
 
I found this Peerless woofer that looks like a pretty good (at least better than any I've found so far) sealed small form factor woofer Peerless 830656 5.25" Woofer: Madisound Speaker Store. It's got a suggested sealed box internal volume of 0.2 ft.^3, and if I plug that into the "Golden Ratio" it looks like dimensions I can work with. I'll have to modify them a bit with the trapezoidal shape, but roughly 7"x5.75"x8.83" or 7 x 5 3/4 x 8 5/6"

What I'm not any good at is finding a tweeter to pair it to. I believe this is a fairly common woofer as I've seen it before in car audio forums. Does anyone have a good tweeter for this? I'm typically a fan of a soft dome. It looks like it's got a livable transient response up til around 2-3k hz. I'm hoping someone's got a crossover design that can tame it down some up near it's upper bounds. It's relatively flat from 100 hz and since I don't know exactly where the subwoofer is low passed, going a little beyond the stated 120 hz from earlier isn't a bad idea.

Comments? Suggestions?
 
You want suggestions, so here goes.

You stated that this is your first DIY project, so you should keep it pretty simple, otherwise you could end up with a longer than expected project with an outcome inferior to your expectations and/or over budget.
You already complicated the project with speakers set directly on the desk: the early reflections will mess up the response. Also the monitor will interfere.

So my first suggestion is to build a set with a small fullrange maybe without any BSC circuit. Your subwoofer with the plate amp will be required. Have a look at this fully documented design: Hi-Vi B3S single driver system
Other 3" drivers that could be utilized are some Tang Band, or Peerless.

If you insist on build a 2-way, keep in mind that most (if not all) published projects are not for a desk, so if you build one of those you will not have the proper frequency response. For an example look at this: Overnight Sensations
I'm not saying you should build this design, but if you do try answering those questions: why the designer chose this exact baffle?, and why the drivers are located where they are?
Hint: diffraction and reflections. If you alter the baffle and drivers location you will change the frequency response of the speaker.
So you can change an existing design or do a new one, but you first need to learn the theory and then use appropriate tools. For a free set look here: FRD tools

Last, some thoughts about the Peerless 830656. I use this driver in a vented configuration, and I find it a good driver. Check my design here on diyaudio: Peerless-830656-suggestions-3. However the closed box needed could be bigger that the ones needed for a 3-4" driver. Another consideration is the tweeter you need: I mated the Peerless with a Vifa BC25TG15, but this tweeter has a 4" faceplate, if you need something smaller, you are at your own.

Ralf
 
You want suggestions, so here goes.

You stated that this is your first DIY project, so you should keep it pretty simple, otherwise you could end up with a longer than expected project with an outcome inferior to your expectations and/or over budget.
You already complicated the project with speakers set directly on the desk: the early reflections will mess up the response. Also the monitor will interfere.

So my first suggestion is to build a set with a small fullrange maybe without any BSC circuit. Your subwoofer with the plate amp will be required. Have a look at this fully documented design: Hi-Vi B3S single driver system
Other 3" drivers that could be utilized are some Tang Band, or Peerless.

If you insist on build a 2-way, keep in mind that most (if not all) published projects are not for a desk, so if you build one of those you will not have the proper frequency response. For an example look at this: Overnight Sensations
I'm not saying you should build this design, but if you do try answering those questions: why the designer chose this exact baffle?, and why the drivers are located where they are?
Hint: diffraction and reflections. If you alter the baffle and drivers location you will change the frequency response of the speaker.
So you can change an existing design or do a new one, but you first need to learn the theory and then use appropriate tools. For a free set look here: FRD tools

Last, some thoughts about the Peerless 830656. I use this driver in a vented configuration, and I find it a good driver. Check my design here on diyaudio: Peerless-830656-suggestions-3. However the closed box needed could be bigger that the ones needed for a 3-4" driver. Another consideration is the tweeter you need: I mated the Peerless with a Vifa BC25TG15, but this tweeter has a 4" faceplate, if you need something smaller, you are at your own.

Ralf

Thanks much Ralf. I know almost nothing about baffle step, but I'm eager to learn.

Would a good course of action be to pick out a pair of drivers (woofer and tweeter) then play with the enclosure shape to flatten out the response, followed by the crossover network, or do I need to start by considering the shape of the enclosure, then pick drivers, then tweak their positioning on the baffle face? I mean the rough shape is fairly set, but the angles and triangle edge lengths are up in the air. I figure I've got a maximum height of about 6" before it becomes intrusive to the workspace. Since the baffle face is intended to be angled slightly upward, that gives me a usable baffle height of more like 6.5".

What I don't know is if there's any way to model a box that takes into account the desktop. Basically an off 90* wall for modeling purposes. I would guess that my best bet to avoid such issues is to go with a highly directional cone with a big drop off off-axis, but that can only get me so far.

This is an elementary illustration of my concern:
An externally hosted image should be here but it was not working when we last tested it.


I may come out with acoustically dead holes in the frequency spectrum, and some amplified peaks. Is this a legitimate concern? I imagine this comes up with a typical bookshelf type monitor too.
 
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You got the problem right. However IMHO it will be very difficult, if not nearly impossible to just play with some drivers and crossover and try to find an acceptable response varying the enclosure (how many enclosures you will need?). You will also need test equipment - at least a (calibrated) microphone.
I don't know if it exist a (free) software able to calculate also the effect of the reflections. But even if you find one, the problem is that you will have nulls. If you move the head you will clearly hear.
The only idea I have is to avoid the reflections, by suppressing them: try a thick piece of felt in the desk area in front of the speakers.
Ralf
 
You got the problem right. However IMHO it will be very difficult, if not nearly impossible to just play with some drivers and crossover and try to find an acceptable response varying the enclosure (how many enclosures you will need?). You will also need test equipment - at least a (calibrated) microphone.
I don't know if it exist a (free) software able to calculate also the effect of the reflections. But even if you find one, the problem is that you will have nulls. If you move the head you will clearly hear.
The only idea I have is to avoid the reflections, by suppressing them: try a thick piece of felt in the desk area in front of the speakers.
Ralf

Okay then. I know this may be one of those pindrop moments in this forum, but what if I ignored the enclosure and instead merely relied on the ideal woofer/tweeter/crossover combination, and let the results be what they will? Will the imaging just be complete trash, with the frequency spectrum chalk full of blatantly obvious peaks and valleys or could I still pull out results that would be good enough to impress the casual listener? This isn't meant to be a record studio. If I'm willing to compromise on the sound quality to an extent to keep my basic design parameters as outlined, am I really cruisin' for a bruisin'? I mean my current desk is covered in beer cans, water bottles, and coffee cups. That can't be great for sound quality, but it's not too noticeable for me.
 
a little more info on the Vifa coaxial speakers...and other stuff

girafino's comment about a simple full range driver project is right on the point, regarding the B3S drivers. Small enclosures, and very easy to move around. I can't stress enough the ability to move the speakers on your desktop, even for just background music. And the 41Hz amp kits are excellent: I have the amp6Basic and love it.

Zaph's speakers are simple and very small. My "retrofits" using the ApexJr coaxs are similar in size (maybe a little smaller). These speakers (the coaxials) can be used in a small sealed box. I'm looking to see what the T/S parameters are, if I can still find them. The tweeters can also be removed from the centre pedestal. The pedestal can then be cut down, and the opening to the motor system can be fitted with either a fabric dust cap (or paper), or a phase plug very easily.

In fact Ceri, you could build a very nice "under monitor soundbar" similar to the types used under televisions. Whatever driver you use (if this is a consideration at all), must be magnetically shielded.

Use a proven tweeter/mid-woof design with a crossover used for those particular drivers, and you could play with a box. Why are you against any ported designs (other than if you screw up a sealed design, it is usually not the end of the world, but in a ported box it can be)?
 
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Use a proven tweeter/mid-woof design with a crossover used for those particular drivers, and you could play with a box. Why are you against any ported designs (other than if you screw up a sealed design, it is usually not the end of the world, but in a ported box it can be)?

I'm against a ported design for a few reasons.

1. I'd have to integrate a port with very limited dimensions (the triangular/trapezoidal enclosure on the corners with a woofer magnet sticking into it will take up a lot of the room as-is).
2. I have a small internal volume to work with and the larger I make it, the less desktop surface area I get. That's the primary reason for building the desk - to get more usable space.
3. Simplicity for a first timer like you mentioned. I've built ported sub boxes for my vehicle before, and had good results, but I'm adding a DIY crossover to this design, so I figure the less variables the better. I'm not trying to make this easy as I want to get outside my comfort zone with this, but I think I can do that without worrying about ports.
4. I've got a subwoofer with a high crossover that's plenty of bass for me. This isn't a crappy little breadbox computer speaker sub. It's probably about 20 lbs in it's box and ported. It doesn't knock over the fine china, but it can rattle the pictures on the wall if I want it to (which I don't).

Is my design goal just an absurdity? I honestly don't know if the parameters I've put forward are just unreachable. Nobody seems to want to suggest a woofer/tweeter 2 way passive crossover system for this, even with the caveat that I'm not after recording studio sound quality, and putting forth that the Peerless 830656 has my interest. Is there not a DIY driver pair that will work in a small sealed box? I apologize if that sounds snippy. I know DIY speaker building can be very complicated, but I believe my design goals are reasonable. I'm actually rather surprised that a search didn't turn up any projects like this. Aren't there any general rules of thumb that can be combined when considering a baffle layout like I've pictured above (ie midrange is likely to be boosted for a listener inside 1 meter)?

I do appreciate the replies thus far. I'm trying to bring this back to my specific project. Looking over some of the modeling software programs from before, I'm well outside my abilities. I'm not even 100% comfortable with T/S parameters and their effect on design, but I know enough that they're important.

My revised goals:
1. 2 way passive crossover stereo speakers for computer games and music
2. Woofer in the 4-5.5" class, tweeter with a baffle no larger than the woofer, but it can be up to that same 4-5.5" size if necessary.
3. 50 watts RMS power handling preferably at 6-8 ohms
4. Low to medium volume levels
5. Sealed small volume enclosure. Sensitivity and low bass extension aren't a primary concern (Hoffman's Law). These will probably never see 50 watts, but I mention it because it's what I've got.
6. The enclosure integrated into the desk as roughly shown in my pictures.
7. A relatively flat frequency sweep. I understand now that baffle step compensation is a big unknown, but a highly directional woofer crossed at 120 hz could combat this to some extent.
 
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