Hi All,
I’m starting this thread to share a new project of a 4-way sealed speaker. It will use the following drivers:
• Tweeter: Peerless XT25SC90-04
• Mid High: HiVi Research DMB-A soft dome
• Mid Bass: Vifa P17WJ-00-08
• Woofers: Two Dayton Audio DC200-8 8” Classic woofers
The woofers will be mounted on the sides opposing each other. The driver selection wasn’t based on extensive research or data analysis - I simply listened to the mid-dome driver at a friend’s place and loved it, so I’m designing this speaker around it. Below are the SketchUp 3D models of the box:
The box will be 1050mm tall, 450mm deep, and 264mm wide on the outside. It will be built with 18mm MDF, with an additional 12mm layer of plywood or MDF on the sides. The midbass chamber will have approximately 11 liters, targeting a Qtc of 0.707. The woofers’ chamber will have about 65 liters, with a Qtc between 0.6 and 0.7.
The box will be veneered with two types of wood:
The sides will be finished with an Imbuia veneer, a typical Brazilian wood that resembles walnut. The front, back, and top will be finished with an ebony veneer. I’m not sure what type of wood the ebony veneer is, as it has been artificially darkened. I haven’t decided yet between a matte or semi-gloss finish, but I’m leaning towards matte. The design for the feet is still in progress.
My goals with this build are:
• Have fun building it. I’m well aware that designing a 4-way speaker isn’t easy, and I could have chosen a proven design. However, that would only challenge my woodworking and building skills, which isn’t my primary goal.
• My current 2-channel system uses a pair of Klipsch RP-6000F floorstanders. I’ll consider this build a success if it offers better soundstage, imaging, and clarity.
The build is already underway, and I’ll be updating this thread with pictures of the progress. Please feel free to contribute, offer criticism, ask questions, or even make fun of it! No hard fellings! 🤣
I’m starting this thread to share a new project of a 4-way sealed speaker. It will use the following drivers:
• Tweeter: Peerless XT25SC90-04
• Mid High: HiVi Research DMB-A soft dome
• Mid Bass: Vifa P17WJ-00-08
• Woofers: Two Dayton Audio DC200-8 8” Classic woofers
The woofers will be mounted on the sides opposing each other. The driver selection wasn’t based on extensive research or data analysis - I simply listened to the mid-dome driver at a friend’s place and loved it, so I’m designing this speaker around it. Below are the SketchUp 3D models of the box:
The box will be 1050mm tall, 450mm deep, and 264mm wide on the outside. It will be built with 18mm MDF, with an additional 12mm layer of plywood or MDF on the sides. The midbass chamber will have approximately 11 liters, targeting a Qtc of 0.707. The woofers’ chamber will have about 65 liters, with a Qtc between 0.6 and 0.7.
The box will be veneered with two types of wood:
The sides will be finished with an Imbuia veneer, a typical Brazilian wood that resembles walnut. The front, back, and top will be finished with an ebony veneer. I’m not sure what type of wood the ebony veneer is, as it has been artificially darkened. I haven’t decided yet between a matte or semi-gloss finish, but I’m leaning towards matte. The design for the feet is still in progress.
My goals with this build are:
• Have fun building it. I’m well aware that designing a 4-way speaker isn’t easy, and I could have chosen a proven design. However, that would only challenge my woodworking and building skills, which isn’t my primary goal.
• My current 2-channel system uses a pair of Klipsch RP-6000F floorstanders. I’ll consider this build a success if it offers better soundstage, imaging, and clarity.
The build is already underway, and I’ll be updating this thread with pictures of the progress. Please feel free to contribute, offer criticism, ask questions, or even make fun of it! No hard fellings! 🤣
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I haven’t decided yet whether it will have a traditional passive crossover or if I’ll use DSP as a crossover with four small stereo amplifiers. Or even a combination of the two — maybe a miniDSP 2x4 HD, two stereo amplifiers, and a passive crossover for the mid-high/tweeter and another for the midbass/woofers. My opinion changes all the time depending on what I've read...
I think that a fully DSP crossover solution would give me a lot of flexibility and room for changes/improvements. However, I already have a DAC and amplifier that I like very much: a RME ADI-2 DAC FS connected to an Emotiva XPA-2 GEN3. I don’t know if a MiniDSP with small amps would give me the same sound quality within a reasonable budget. On the other hand, I’m quite sure that I won’t be able to design a decent passive crossover on the first try, even with measurement equipment (I have a Dayton Audio UMM-6 measurement mic and basic knowledge of REW).
So, I had the idea to experiment before building or buying a definitive solution. I've built this "thing" (I don't know how to call it) using no more than 100 usd on parts. It is a (very) cheap car audio digital processing unit connected to a (even more) cheap 4-channel car amplifier, both powered by a (again) cheap chinese AC/DC 12V 50A power supply.
This will allow me to experiment with different crossover configurations. This thing costs less than 40 usd and has a noise floor of a static factory, but has a decent number of filter types, phase/time adjustments and even parametric EQ. So I intend to configure, measure, configure, measure.... Until I get a decent FR. Then I can decide if it is feasible to replicate it in a passive crossover or not (given my design expertise that is almost none).
I think that a fully DSP crossover solution would give me a lot of flexibility and room for changes/improvements. However, I already have a DAC and amplifier that I like very much: a RME ADI-2 DAC FS connected to an Emotiva XPA-2 GEN3. I don’t know if a MiniDSP with small amps would give me the same sound quality within a reasonable budget. On the other hand, I’m quite sure that I won’t be able to design a decent passive crossover on the first try, even with measurement equipment (I have a Dayton Audio UMM-6 measurement mic and basic knowledge of REW).
So, I had the idea to experiment before building or buying a definitive solution. I've built this "thing" (I don't know how to call it) using no more than 100 usd on parts. It is a (very) cheap car audio digital processing unit connected to a (even more) cheap 4-channel car amplifier, both powered by a (again) cheap chinese AC/DC 12V 50A power supply.
This will allow me to experiment with different crossover configurations. This thing costs less than 40 usd and has a noise floor of a static factory, but has a decent number of filter types, phase/time adjustments and even parametric EQ. So I intend to configure, measure, configure, measure.... Until I get a decent FR. Then I can decide if it is feasible to replicate it in a passive crossover or not (given my design expertise that is almost none).
The woodworking part has already started. I've bought a sheet of 18mm MDF (2750mm x 1830mm) and already cut all the parts.
Testing how all braces will be mounted (midbass chamber is not yet at a 45 degree angle as in the design - I've changed it after all cuts were made). Openings on bracings were also not cut yet when this picture was taken.
I 3d-printed templates to cut the driver's holes on the baffle
It worked, but not as good as the traditional circle jig that everybody uses to cut round holes. There are a few imperfections that I will fix with wood filler or bondo before veneering. I've also rounded the edges on the back of the baffle.
The holes for the woofers on the side panels were cut using a circle jig.
This weekend I want to assemble the boxes, or at least most of it.
Testing how all braces will be mounted (midbass chamber is not yet at a 45 degree angle as in the design - I've changed it after all cuts were made). Openings on bracings were also not cut yet when this picture was taken.
I 3d-printed templates to cut the driver's holes on the baffle
It worked, but not as good as the traditional circle jig that everybody uses to cut round holes. There are a few imperfections that I will fix with wood filler or bondo before veneering. I've also rounded the edges on the back of the baffle.
The holes for the woofers on the side panels were cut using a circle jig.
This weekend I want to assemble the boxes, or at least most of it.
If you want lower midbass Q, cover the gaps that open to behind the mid and tweeter with open cell foam. You could even close one of them off completely. If you glue the perimeter around the opening, this will make a multi-chamber-aperiodically damped system. Stuff the chamber behind the midbass, and line the upper one.
I really like how you did the right angle behind the midbass in the original image.
I really like how you did the right angle behind the midbass in the original image.
I am not familiar with the concept but, after a quick google search, it seems to be an interesting possibility. I'll look into it and do the math (if there is any).
Thanks!
The weekend wasn’t as productive as I expected, but I made some progress.
The recess for the binding post plate has been cut, and the area where the crossover will be placed (if I decide to go with a passive crossover) has been marked, and 4 roles for threaded inserts were drilled.
Assembly of one of the boxes is complete. As soon as I took the picture, I realized that I forgot to round the inner edges of the woofer hole… Damn! WIll have to do it by hand or find a router bit that can to the job from the outside.
The side panel will be installed after I add the damping material. I will use 3mm butyl rubber sheets (a Dynamat-like product) and then line everything with 15mm felt.
The recess for the binding post plate has been cut, and the area where the crossover will be placed (if I decide to go with a passive crossover) has been marked, and 4 roles for threaded inserts were drilled.
Assembly of one of the boxes is complete. As soon as I took the picture, I realized that I forgot to round the inner edges of the woofer hole… Damn! WIll have to do it by hand or find a router bit that can to the job from the outside.
The side panel will be installed after I add the damping material. I will use 3mm butyl rubber sheets (a Dynamat-like product) and then line everything with 15mm felt.
Both boxes are assembled. Now I am adding damping material to the interior.
I have already applied the 3mm thick butyl rubber sheets to the sides. I’ll also apply them to the baffle, top, back, and maybe the bottom.
I’m not sure how to proceed. The box is fairly well braced, and the way the woofers will be mounted reduces a lot of the resonances. I’m uncertain if it makes sense to add damping sheets to the bracings and midbass chamber. Any opinions on this?
I have already applied the 3mm thick butyl rubber sheets to the sides. I’ll also apply them to the baffle, top, back, and maybe the bottom.
I’m not sure how to proceed. The box is fairly well braced, and the way the woofers will be mounted reduces a lot of the resonances. I’m uncertain if it makes sense to add damping sheets to the bracings and midbass chamber. Any opinions on this?
Did you check how much distance the two woofers have to each other? To be precise, their pole core bore back plate to each other? If they can't exhaust the air, you lose a lot of dynamics because of compression and also lose a lot of cooling.
Yes, that's enough space. And sorry I suspected it to be critical but I've seen it numerous times ppl just put magnet on magnet and even being proud of that, even the wanna-be perfectionist Bernd Timmermanns (of the 'renowned' German magazine "Hobby HiFi") did that. Aside from the (seemingly) obvious blockage of the magnet core piece vent, it also deforms the magnet field, causing a very asymmetric Bl(x). When I sent in a complaint about the (obvious) issue, it was ignored but he posted an article on how the impulse compensation was so extremely beneficial. He's done a lot good things but he can't admit if he's wrong. Like when he claimed to be the inventor of the high pass capacitor sealed enclosure and the high pass reflex enclosure - which were already used by Technics and other companies back in the 70s.
Okay, scratch the 'very'. It's still not something I can fathom how ppl search for weeks for the perfect drivers, bickering about the smallest differences in measurements and then self-sabotage their own speakers by that. The sum of the compression, resulting in asymmetry of compliance and Bl(x) does impact the sound.
dptucunduva, have you calculated the lowest box mode for the woofer so you can see whether you need to stuff it?
Honestly, no 😬.
But I tried to do it now, please feel free to correct me if my calculations are wrong.
The inner box dimensions for the woofer chamber are 1014mm (H), 204mm (W), and 414mm (L). So, the modes would be 169 Hz (H), 414 Hz (L) and 841Hz (H).
My initial idea is to cross the drivers at:
- Tweeter: HPF at 4500Hz
- Mid High: BPF from 850Hz to 4500Hz
- Mid Bass: LPF at 850Hz
- Woofers: LPF at 140Hz
No.
414hz and 841hz should be easily tamed using enough absorbing material inside the box.
The 169hz is theorical as you have a kind of labyrinth inside the enclosure and here again absorbing material should take care of this but you would have to be more accurate about location ( for the two sub enclosure fill/stuff them as much as you can imho), or not: stuff the whole thing as much as you can ( not packing too much as there must be some airflow for effect to happen.
Edit: Allen was faster than i was.
414hz and 841hz should be easily tamed using enough absorbing material inside the box.
The 169hz is theorical as you have a kind of labyrinth inside the enclosure and here again absorbing material should take care of this but you would have to be more accurate about location ( for the two sub enclosure fill/stuff them as much as you can imho), or not: stuff the whole thing as much as you can ( not packing too much as there must be some airflow for effect to happen.
Edit: Allen was faster than i was.
I was just rechecking my numbers. It seems the furthest (looking for lower frequency modes) direct path would be from the middle of the woofer to an inside corner, half way between the woofers. That's around 55cm or 110cm round trip.
Thanks for the tips.
I will line the inside of the box with a 15mm felt mat over the butyl rubber. Then, after that, will stuff the box with a light poly material. I have plenty availbale, so I guess it would be besto to measure without it and then again after stuffing the box.
I will line the inside of the box with a 15mm felt mat over the butyl rubber. Then, after that, will stuff the box with a light poly material. I have plenty availbale, so I guess it would be besto to measure without it and then again after stuffing the box.
Actually, from the center of the woofer to the furthest corner, that would be aprox. 776mm. The center of the woofers are 300mm from the bottom of the box.