FINISHED: DIY 2-way computer/desktop speaker build - help!
Hello all, need your advice!
I am thinking of building a computer/desktop speakers. I have some parts (woofers and amp) laying around which I could use, but I have little experience in designing speakers.
Tweeter: ?
Woofer: SB Acoustics SB20PFC30-4 8" Paper Cone Woofer (Buying a SB Acoustics SB20PFC30-4 woofer? - SoundImports)
Amp: 3e Audio TPA3251 4x100W 4ch Class D (TPA3251-4CH-100W | 3e Audio)
So, my questions are, what tweeter would combine well with the chosen woofer? What would be the crossover frequency (I can program one for the DSP)? What should be the dimensions, internal volume, and should there be a vent? What kind of vent?
For the housing, I have plenty of quality veneer available, but I could also buy MDF. This build would be my second build as my first one was in school couple decades ago...
Cheers!
Hello all, need your advice!
I am thinking of building a computer/desktop speakers. I have some parts (woofers and amp) laying around which I could use, but I have little experience in designing speakers.
Tweeter: ?
Woofer: SB Acoustics SB20PFC30-4 8" Paper Cone Woofer (Buying a SB Acoustics SB20PFC30-4 woofer? - SoundImports)
Amp: 3e Audio TPA3251 4x100W 4ch Class D (TPA3251-4CH-100W | 3e Audio)
So, my questions are, what tweeter would combine well with the chosen woofer? What would be the crossover frequency (I can program one for the DSP)? What should be the dimensions, internal volume, and should there be a vent? What kind of vent?
For the housing, I have plenty of quality veneer available, but I could also buy MDF. This build would be my second build as my first one was in school couple decades ago...
Cheers!
Last edited:
No tweeter crosses very well to an 8" woofer. You'll need a mid-tweeter or a small fullrange for best results. I have one in a small aperiodic enclosure with L.Cao FA6 and Dayton AMT automotive tweeter. Crossover points are 400 and 5000Hz. Woofer chamber is 15L with a very restrictive 8 x 200mm slot port.
+1 on the SB65WBAC25-4. It’s 82dB at 2.83v so perfect match for the 8in after baffle step loss. No need to add a resistor to pad the tweeter down. Cross even from 600Hz to 1000Hz simple first order even for a FAST type system. Very similar to what I did here:
10F/8424 & RS225-8 FAST / WAW Ref Monitor
I have in fact, tested the above system with the SB65 and RS225-8 and they sound great together. Both aluminum cones and SB65 has reach up to 20kHz easily.
10F/8424 & RS225-8 FAST / WAW Ref Monitor
I have in fact, tested the above system with the SB65 and RS225-8 and they sound great together. Both aluminum cones and SB65 has reach up to 20kHz easily.
I've also had a look at the SB20pfc as it's much cheaper than the RS225 here (Melbourne). While it's a paper cone, the specs and frequency response are very close to the Dayton.
I don't have the drivers or measuring equipment but I modelled a two way in Xsim using the SB20 and the VIFA TC7FD-004, a very nice and cheap 2.5" full range driver; it looked good although I didn't model a cabinet.
Geoff
I don't have the drivers or measuring equipment but I modelled a two way in Xsim using the SB20 and the VIFA TC7FD-004, a very nice and cheap 2.5" full range driver; it looked good although I didn't model a cabinet.
Geoff
Okay, SB65 for the fullrange. No one yet gave any ideas for the enclosure, but maybe if I copy, say Adam T8V speakers, which dimensions are (WxHxD): 250 x 400 x 335mm. Size would be reasonable and volume 33.5L. I was thinking of using quality Finnish plywood as the material, which I have plentiful. I have no idea about the vent though. Should the box have different chambers for the woofer and fullrange elements? I guess its a hit or miss...
One thing with the woofer, it has a bit strange flange/collar/whatever that carving it to the wood would be somewhat tricky, especially with the plywood. Surface mount might be visually less attractive.
One thing with the woofer, it has a bit strange flange/collar/whatever that carving it to the wood would be somewhat tricky, especially with the plywood. Surface mount might be visually less attractive.
Definitely need separate small chamber for SB65. Use a small sports cone stuffed with polyfill or fiberglass. Have that isolated from the main chamber.
If you are good with 55Hz I think the main chamber can be sealed. Just follow recommend box volume.
If you are good with 55Hz I think the main chamber can be sealed. Just follow recommend box volume.
The vented box for the SB20 is relatively large, so I don't think it could be regarded as a desktop. Madisound's product page provides some calculated volumes, vents sizes and F3s for sealed and vented cabinets.
SB Acoustics SB20PFC30-8 8" Paper Cone Woofer
The frame shape is indeed a pain to mount and SB has now discontinued that in favour of a round frame. I did a test build with the SB16PFC (same shape) and just surface mounted it. However, it can be flush mounted, there's a project on Parts Express Tech Talk for a MTM with the SB13 (again, same frame shape) which includes advice on how to mount the SBs.
Galeons - SB13 MTM -
Techtalk Speaker Building, Audio, Video Discussion Forum
The SBPFC series (12, 13, 16 and 20) are excellent value for the $ and several speaker makers here and in Germany use them in commercial projects.
I don't it's necessarily true that 'no' tweeter will work well with an 8" woofer: Wolf's "Zingers" speakers use an 8" with the Peerless DA25 and people who've built them are very happy.
Geoff
SB Acoustics SB20PFC30-8 8" Paper Cone Woofer
The frame shape is indeed a pain to mount and SB has now discontinued that in favour of a round frame. I did a test build with the SB16PFC (same shape) and just surface mounted it. However, it can be flush mounted, there's a project on Parts Express Tech Talk for a MTM with the SB13 (again, same frame shape) which includes advice on how to mount the SBs.
Galeons - SB13 MTM -
Techtalk Speaker Building, Audio, Video Discussion Forum
The SBPFC series (12, 13, 16 and 20) are excellent value for the $ and several speaker makers here and in Germany use them in commercial projects.
I don't it's necessarily true that 'no' tweeter will work well with an 8" woofer: Wolf's "Zingers" speakers use an 8" with the Peerless DA25 and people who've built them are very happy.
Geoff
Last edited:
Just ballparking numbers. Madisound's page gives following numbers:
""
Sealed box of 0.5 to 0.75 cubic foot for a 3dB down of about 70Hz
Vented box of 0.75 cubic foot with 2" Ø vent by 5" long for f3 of 55Hz
Vented box of 1.0 cubic foot with 2" Ø vent by 4" long for f3 of 49Hz
Vented box of 1.25 cubic feet with 2" Ø vent by 3.5" long for f3 of 45Hz
Vented box of 1.5 cubic feet with 2" Ø vent by 3" long for f3 of 42Hz
""
Now I'm thinking dimensions could be (WxHxD): 250x500x250mm, giving volume of 31L (about 1.1 cubic foot). This depth of 250mm would be more suitable on tabletop than the 335mm. I could also make a removable backplate with screws and sealant so I could try with the 4" vent and without vent. I think I surface mount the SB20. It is what it is.
""
Sealed box of 0.5 to 0.75 cubic foot for a 3dB down of about 70Hz
Vented box of 0.75 cubic foot with 2" Ø vent by 5" long for f3 of 55Hz
Vented box of 1.0 cubic foot with 2" Ø vent by 4" long for f3 of 49Hz
Vented box of 1.25 cubic feet with 2" Ø vent by 3.5" long for f3 of 45Hz
Vented box of 1.5 cubic feet with 2" Ø vent by 3" long for f3 of 42Hz
""
Now I'm thinking dimensions could be (WxHxD): 250x500x250mm, giving volume of 31L (about 1.1 cubic foot). This depth of 250mm would be more suitable on tabletop than the 335mm. I could also make a removable backplate with screws and sealant so I could try with the 4" vent and without vent. I think I surface mount the SB20. It is what it is.
For desktop levels, I'd always recommend sealed & EQ, unless cone area is in short supply. In that case, PRs make sense.
Chris
Chris
One way to get around the ugly frame with a FR crossed around 300Hz is to mount the woofer sideways. This also helps with woofer resonances at the top of the passband.
I definitely recommend sealed for this woofer. There is very little excursion capability and the bass could be a lot cleaner even with aperiodic port. In BR it will sound pretty ugly, remember it's a cheap plastic frame and a very primitive motor.
I definitely recommend sealed for this woofer. There is very little excursion capability and the bass could be a lot cleaner even with aperiodic port. In BR it will sound pretty ugly, remember it's a cheap plastic frame and a very primitive motor.
It might have a simple motor, a funny shaped plastic frame and a paper cone (or, as SB calls it, 'papyrus') but so does the SB16pfc, and that sounds pretty good to me. As far as I can tell - from the specs, anyway - Xmax is 4.5mm, OK but not up to the RS225: but then in Oz, it's less than half the price.
I like the idea of sideways mounting, I've never tried that but have seen it in several projects. A neater solution than trying to flush mount the thing, I gave up.
The only DIY build I've seen with the SB20pfc was a two way, sealed cabinet with the VIFA TC9 full range driver, XO at 600Hz, so you may well be right about the box alignment.
Geoff
I like the idea of sideways mounting, I've never tried that but have seen it in several projects. A neater solution than trying to flush mount the thing, I gave up.
The only DIY build I've seen with the SB20pfc was a two way, sealed cabinet with the VIFA TC9 full range driver, XO at 600Hz, so you may well be right about the box alignment.
Geoff
The cone is not too far off the Satoris actually, at least visually. I have the MW19P on hand and they don't look that different last I checked. The Satori is better finished overall with a slight gleam to the actual paper, but the fiber arrangement and the overall materials used are similar.
I haven't heard the 6" version myself, but on the 8" at least the bass is not great. Even in a sealed box it tends to be a little floppy at moderate levels. For desktop listening it might not be as much of an issue due to lower levels, but when crossing low a hard cone is really the way to go, even if it is on a stamped frame.
You've to note that a while round frame is evenly supported, the SB frame has large lands that have basically zero support from the baffle. Though there are plenty of woofers with this frame design, none IIRC are made of plastic. Witness the Volt B2549 (which I also have in another speaker) with just 4x M5 bolts but the frame is a massive cast aluminum basket. Extremely rigid and not prone to flex at all, unlike plastic.
The unfortunate design is coupled to a poor material choice, specially for a design that is supposed to have some bass reproduction capability. I was actually taken aback by how weak it was in that area. Midrange is actually not too bad, I tried it with a SB26STCN tweeter crossed at 1.6k and it sounded fine for nearfield, but it beamed like crazy unless you got quite far away from the speaker, and then the levels required were too much for the woofer.
Just to add, I have mine surface mounted on the side panel. Crossover is low enough (and simple enough) that it does a decent job. A high sensitivity driver is recommended so that input power levels remain low. You definitely don't want to be going beyond 90dB average with this driver.
I haven't heard the 6" version myself, but on the 8" at least the bass is not great. Even in a sealed box it tends to be a little floppy at moderate levels. For desktop listening it might not be as much of an issue due to lower levels, but when crossing low a hard cone is really the way to go, even if it is on a stamped frame.
You've to note that a while round frame is evenly supported, the SB frame has large lands that have basically zero support from the baffle. Though there are plenty of woofers with this frame design, none IIRC are made of plastic. Witness the Volt B2549 (which I also have in another speaker) with just 4x M5 bolts but the frame is a massive cast aluminum basket. Extremely rigid and not prone to flex at all, unlike plastic.
The unfortunate design is coupled to a poor material choice, specially for a design that is supposed to have some bass reproduction capability. I was actually taken aback by how weak it was in that area. Midrange is actually not too bad, I tried it with a SB26STCN tweeter crossed at 1.6k and it sounded fine for nearfield, but it beamed like crazy unless you got quite far away from the speaker, and then the levels required were too much for the woofer.
Just to add, I have mine surface mounted on the side panel. Crossover is low enough (and simple enough) that it does a decent job. A high sensitivity driver is recommended so that input power levels remain low. You definitely don't want to be going beyond 90dB average with this driver.
What about 3d print a cover for the sb65? Just something simple that could be screwed to the driver? The part can be as simple as an open box. If nuts or inserts where attached to the 3d enclosure, it would have the added advantage of making the driver removable.
I am designing a similar enclousure for a two way 5.5" waveguide (even maybe pot the waveguide with epoxy till the driver mount point).
I am designing a similar enclousure for a two way 5.5" waveguide (even maybe pot the waveguide with epoxy till the driver mount point).
I have finished this project... almost. I was able to have a carpenter help me with the boxes. Material used is high quality 18mm plywood and the mass of the box is 9.15kg each. Pretty heavy. Finished with wood stain and two layers of lacquer.
I don't have a passive crossover but I'm using an amp with a DSP. I tried different crossovers but found out that I liked the 300 Hz the most and a bit of gain on the lower frequencies. The neat thing about the SigmaStudio and the DSP is that you can try different settings while listening. I haven't yet finished the amp though. I was thinking of adding a subwoofer and I need to make a box for the amp and the power supplies. As you can see the amp is not a very safe for now. 😀
Drivers:
SB Acoustics SB65WBAC25-4 2,5" Full Range Driver 4 Ohm
SB Acoustics SB20PFC30-4 8" Paper Cone Woofer
Amp:
TPA3251 4ch TPA3251-4CH-100W | 3e Audio
2x 24V 4A PSU (one for the speaker amp and one for the sub amp)
Attached few images.
I don't have a passive crossover but I'm using an amp with a DSP. I tried different crossovers but found out that I liked the 300 Hz the most and a bit of gain on the lower frequencies. The neat thing about the SigmaStudio and the DSP is that you can try different settings while listening. I haven't yet finished the amp though. I was thinking of adding a subwoofer and I need to make a box for the amp and the power supplies. As you can see the amp is not a very safe for now. 😀
Drivers:
SB Acoustics SB65WBAC25-4 2,5" Full Range Driver 4 Ohm
SB Acoustics SB20PFC30-4 8" Paper Cone Woofer
Amp:
TPA3251 4ch TPA3251-4CH-100W | 3e Audio
2x 24V 4A PSU (one for the speaker amp and one for the sub amp)
Attached few images.
