Hi,
I'm new to the forum. Working from home now and want to upgrade from my old PC speakers. Planning to build a set of desk top speakers using MarkAudio CHP-70 drivers.
Project goals: simple build, good sound quality for low level background music while working, nice finished appearance. I found the enclosed plans, and I have a few questions. My apologies in advance if all this info is already available elsewhere, but I could not find it easily, and I'd welcome some input from the experienced folk on this site!
1) Can I replace the circular port with a slot port? (I just think it would look better) The cross section of the design is about 5 square inches. Should I make the slot the same cross section? How long should the slot be within the cabinet?
2) Does the design require any input filter circuitry? I plan to initially power it from an old receiver, and maybe later shift to a small dedicated amp with bluetooth.
3) What do you think about using solid wood (I have some maple) instead of MDF or plywood. It would make the project easier for finishing. Maybe just the front baffle?
4) For aesthetics, thinking about a 1/4" or 1/2" round-over of the front baffle - again for aesthetics. Any issues with this?
5) The design shows no internal bracing. I'm assuming this is not needed for a small box like this? - and I don't expect to play it loud.
6) What internal stuffing is recommended? I'm hoping for cheap and easy.
My thought is to try these out without a sub. Maybe I'd add a little one later.
Thanks in advance!
I'm new to the forum. Working from home now and want to upgrade from my old PC speakers. Planning to build a set of desk top speakers using MarkAudio CHP-70 drivers.
Project goals: simple build, good sound quality for low level background music while working, nice finished appearance. I found the enclosed plans, and I have a few questions. My apologies in advance if all this info is already available elsewhere, but I could not find it easily, and I'd welcome some input from the experienced folk on this site!
1) Can I replace the circular port with a slot port? (I just think it would look better) The cross section of the design is about 5 square inches. Should I make the slot the same cross section? How long should the slot be within the cabinet?
2) Does the design require any input filter circuitry? I plan to initially power it from an old receiver, and maybe later shift to a small dedicated amp with bluetooth.
3) What do you think about using solid wood (I have some maple) instead of MDF or plywood. It would make the project easier for finishing. Maybe just the front baffle?
4) For aesthetics, thinking about a 1/4" or 1/2" round-over of the front baffle - again for aesthetics. Any issues with this?
5) The design shows no internal bracing. I'm assuming this is not needed for a small box like this? - and I don't expect to play it loud.
6) What internal stuffing is recommended? I'm hoping for cheap and easy.
My thought is to try these out without a sub. Maybe I'd add a little one later.
Thanks in advance!
I cannot fully answer all your questions, however..
You can make a slot port
Solid wood is fine, or solid wood over something like MDF
A round-over is fine and will not affect any significant amount
If you can add at least one internal brace, could be just a dowel in between the largest of the panels
Usually the stuffing is polyester fiber
Enjoy
You can make a slot port
Solid wood is fine, or solid wood over something like MDF
A round-over is fine and will not affect any significant amount
If you can add at least one internal brace, could be just a dowel in between the largest of the panels
Usually the stuffing is polyester fiber
Enjoy
Take a look at the CHP 70 slim golden ratio. I used these for a long time for desktop speakers and they are truly amazing.
Look for the Classic Golden Ratio dKal-El70.3.
Frugal-phile | Box Library / Mark Audio
Look for the Classic Golden Ratio dKal-El70.3.
Frugal-phile | Box Library / Mark Audio
Answers below:
Yes, you can replace a round tube with a slot port. Make the slot port the same area and the same equivalent length as the circular port. I typically use a short cover board inside the enclosure spaced just above the bottom of the box to form the slot.
The area of the port is about 962 sq. mm per the well know Area = pi x r^2 . One example is to make the slot the same width as the inside width of the cabinet which is 140 mm. But with that width the slot height would be (962/140) = 6.87 mm. You can play with port width and height to your pleasure to get the height you prefer. For the slot port length I would use the 75 mm in the drawing less the thickness of the cover board to compute the travel distance for the air flowing through the port. Thus for this example if we use 18 mm thickness material the cover board length would be 75 mm - 18 mm = 57 mm long.
You may eventually have a baffle compensation network on the input if your situation needs it. When placed on a desk close to the wall your speakers may not need any compensation.
I have made many speakers with solid wood side cheeks and MDF for the other panels. My recommendation is to use kiln dried wood and have the grain flowing in the vertical direction (as in a tree) for best results.
Roundovers for the enclosure are visually pleasing. Notice that there is a small roundover of the exit hole for the driver inside the enclosure.
Made from 18 mm thick material you likely will not need much bracing. If you wish, you can use dowels between the sides and top/bottom if you wish.
For sealed and many transmission line speakers you can stuff with polyfill. For a vented or bass reflex version like this design 1.5 inch convoluted egg crate acoustic foam is the material to use. Checkout Parts Express for this foam. Usually this material or pieces of it covers portion of the inside walls, rear, and top. You place it so that the air flow between the driver and the port is not impeded.
Good luck.
Jim
Yes, you can replace a round tube with a slot port. Make the slot port the same area and the same equivalent length as the circular port. I typically use a short cover board inside the enclosure spaced just above the bottom of the box to form the slot.
The area of the port is about 962 sq. mm per the well know Area = pi x r^2 . One example is to make the slot the same width as the inside width of the cabinet which is 140 mm. But with that width the slot height would be (962/140) = 6.87 mm. You can play with port width and height to your pleasure to get the height you prefer. For the slot port length I would use the 75 mm in the drawing less the thickness of the cover board to compute the travel distance for the air flowing through the port. Thus for this example if we use 18 mm thickness material the cover board length would be 75 mm - 18 mm = 57 mm long.
You may eventually have a baffle compensation network on the input if your situation needs it. When placed on a desk close to the wall your speakers may not need any compensation.
I have made many speakers with solid wood side cheeks and MDF for the other panels. My recommendation is to use kiln dried wood and have the grain flowing in the vertical direction (as in a tree) for best results.
Roundovers for the enclosure are visually pleasing. Notice that there is a small roundover of the exit hole for the driver inside the enclosure.
Made from 18 mm thick material you likely will not need much bracing. If you wish, you can use dowels between the sides and top/bottom if you wish.
For sealed and many transmission line speakers you can stuff with polyfill. For a vented or bass reflex version like this design 1.5 inch convoluted egg crate acoustic foam is the material to use. Checkout Parts Express for this foam. Usually this material or pieces of it covers portion of the inside walls, rear, and top. You place it so that the air flow between the driver and the port is not impeded.
Good luck.
Jim
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We will assume that this is the CHP70.2/3 (depending on how you count), the currently available one. Good sounding, but has a shelved down top end.
Step 0: go look for one from Scott (scottmoose) or the CGR already mentioned. Mark’s designs are often suspect and both of us have worked to provide better options.
Scott recently sold off a dozen or so pair sof these and published a sketch for a design for these in it (i have yet to redraw it).
Yes. Basically same cross-section and same area. The CGR comes w slot vent already.
Maybe. Some would add BSC (Baffle Step Compensation), but not likely needed if you are listening nearfield. Something i rarely like.
Stay away from MDF it is not a great speaker building material — its only asset is that it is cheap.
Building with solid wood is often done, but one really should have knowledge of the issue sthis brings. A solid baffle is more sensible.
Not an issue, we usually used a chamfer, as it approximates a larger roundover (and we like the aesthetics)
I haven’t bothered figuring out the volume of this design, but big for this driver in a vented box is 9-10 litres and we would build it from 15mm and typically add a brace from the driver to the back panel so as to share driver energy with more panels. Cutting a big hole in th ebaffle makes it the weakest panel.
Some sort of lining is usually used to line the walls of a vented enclosure. Jim mentions foam, not something all that effective, poly batting as used inside jaskets and quilts is suitable but like not as cheap or as well preforming as thin (~25mm) fiberglass insulation. We use cotton felt (or sometimes recycled wool felt (12-13mm), a cheap source is often found as carpet underlay in older cars (avoid anything 100% synthetic)
These don’t go as low as the Gen 1 CHP or its EL70 cousin, but likely go low enuff to satisfy near-field, but that depends on how much bass you like.
dave
A quick update:
The drivers arrived. I've built the boxes. I decided to stick with the bass reflex design instead of the golden ratio version of the enclosure due to the smaller size.
I am still waiting on the damping material, so the boxes are empty and not sealed. Even so, the sound is quite nice. Looking forward to getting them sealed up. My first experience with a FR speaker. Also provides nice audio for all those video meetings! Not sure if I will stain the wood or leave them natural before applying a finish. When I get them done, I'll post another update.
The drivers arrived. I've built the boxes. I decided to stick with the bass reflex design instead of the golden ratio version of the enclosure due to the smaller size.
I am still waiting on the damping material, so the boxes are empty and not sealed. Even so, the sound is quite nice. Looking forward to getting them sealed up. My first experience with a FR speaker. Also provides nice audio for all those video meetings! Not sure if I will stain the wood or leave them natural before applying a finish. When I get them done, I'll post another update.
