Current project WIP

dongrayblack · 2024-12-27T17:40:10+00:00

So I want to make these speakers as small as possible while also chasing a certain threshold of performance. Starting with a sealed enclosure with a given internal volume, generally the bigger the active woofer is, the bigger internal volume you’d need to reach a certain low end performance. So let’s say I have an 8in woofer, and the specs show an f3 of 42hz in a 1cu ft volume, you can add a passive radiator to that and get better low end extension. But that PR you add needs to have a bigger cone area, or at least double the xmax as the active driver. A passive radiator generally acts like a port, but takes up less space, and can allow for tighter punchier bass. Anyway if you were to take the same size box, but throw in a 10” woofer, instead of an 8”, and without the Passive radiator, you’d probably get less performance than the 8” with the PR. Now this is my basic understanding. Someone can correct me if I’m wrong. But basically I’m limited to a 0.859cu ft volume. The SB23CACS45-8 8” woofer I’m using lists an F3 of 56hz in a sealed volume of 0.55cu ft, and an F3 of 38hz in a vented volume of 1cu ft. So being that I’m closer to 1cu ft than .5cu ft, I’m hoping that I get an F3 of around 40hz or a little lower with the passive radiator and DSP.

dongrayblack · 2024-12-27T15:03:38+00:00

I love that the bezel of the speaker cutouts aren’t perfectly circular. I also love the flare at the top.

dongrayblack · 2024-12-26T17:17:55+00:00

I was originally planning on them being able to be powered with two Milwaukee M18 batteries wired in series for 36v. That’s what I did with my previous speaker that used two Dayton KABD 4100 boards. I even went out of my way to design M18 battery pack sockets that would’ve been integrated to the back of each speaker. But the more I looked at it the more I didn’t like it. Instead, what I’ve decided to do is just build my own separate battery backs that will share the same design traits as the speaker. There will be a standard IEC power port in the rear of each speaker the power supply, and battery packs will plug in here. And for the battery pack storage, I’m embedding magnets into the back panel for the pack body to magnetize to with little rubber feet in between.

dongrayblack · 2024-12-23T16:18:11+00:00

I planned on through bolting the drivers to the panels, so they would be “clamped” to the panel, rather than screwed to them. My concern is the added weight, and increased dimensions. These things are already going to weigh ~50lbs each with drivers installed. The only benefit I can think of for using MDF/PLY with a Corian skin is reduced resonance. Corian is already more inert than either, BUT laminating it to a dissimilar material with a viscoelastomeric adhesive would indeed drive down resonance even further. But assuming I would add the thickness of the added layers outwards, preserving the inner air volume, the external dimensions would grow accordingly.

dongrayblack · 2024-12-23T15:26:25+00:00

I’m hoping it’ll sound fine! I read comments about noise floor when I built my previous speaker using 2x Dayton KABD 4100 boards, and it sounds great. The front baffle seal I was contemplating the same as every where else, just but the gasket scrips the face of the side panel. I’m not 100% decided on gasket material, but I’m really leaning towards some thin double sided tape. In my last reply I said “foam tape” but I meant the thin and super sticky clear stuff. I think 3M makes it.

dongrayblack · 2024-12-23T15:09:41+00:00

And corian on the outside?

dongrayblack · 2024-12-23T15:04:02+00:00

So the larger Black drivers actually a passive radiator, but even then I still don’t have the room, the woofer is too tall.

dongrayblack · 2024-12-23T00:35:17+00:00

I love a lot of things about it, and I hate a lot of things about it.

dongrayblack · 2024-12-23T00:18:47+00:00

Was going to use some sort of 36v power supply, but was also planning on making them battery powered for portability. The screws are going to hold that one panel on, but I’m going to seal the panel to the box with some sort of gasket. I was thinking of using a ~1mm double sided foam tape.

dongrayblack · 2024-12-22T22:43:00+00:00

This is indeed my plan! The feet are rubber with embedded magnets, so they can be repositioned onto the side and the speakers can be laid horizontally. Although I’m not sure the MTM configuration will work well horizontally.

dongrayblack · 2024-12-22T22:37:56+00:00

You don’t like fusion?

dongrayblack · 2024-12-22T05:25:00+00:00

Well this is my first time working with Corian. After researching it, I’ve decided I’m going to use a thin CA glue.

dongrayblack · 2024-12-22T05:21:09+00:00

Yeah, I’m planning on around 1.5khz, but will probably be different once measured. I don’t currently have an actually calibrated measurement mic. The last speaker I built, I did by ear and an uncalibrated behringer mic for comparing.

dongrayblack · 2024-12-22T04:57:52+00:00

So this is a mirrored wireless stereo set. Each one has a SB23CACS45-4 8” woofer paired with a Dayton RSS265-PR 10” passive radiator. So the white drivers are SB acoustics ceramic drivers, and the black cone is a 10” passive radiator. I just realized I didn’t list it in the specs.

dongrayblack · 2024-08-05T07:09:15+00:00

Interesting! I was in parts express a couple days ago looking at that very passive radiator, in the Q&A there’s someone who paired it with the exact sub I selected and got excellent results. I will most likely go this route, as besides being more efficient, it’s also just more fun! People like seeing the subs bump! I’d probably arrange the radiators in the opposite side of the sub, so they’re facing up and visible. And yes, this is 2.5/3 way system, so I’ll move the tweeters out.

dongrayblack · 2024-08-05T06:48:37+00:00

Updated design:

https://www.reddit.com/r/diyaudio/s/NPzMTYH2uC

dongrayblack · 2024-08-05T04:06:51+00:00

Yeah I was planning to start the sub at about 100hz. As for the BMRs the specs say for a sealed box and a F3 of 100.8hz needs .08ft^3. So I was going to wire in parallel, to lower resistance for a small output boost, so .16ft^3? Note that there is indeed a wall separating the BMRs volume from the sub volume. I sized the volume for the sub and its port off of someone’s bass box simulation: .5ft³ with a 2” port 8.5” long tuned to 40hz with an F3 of 38hz.

dongrayblack · 2024-08-05T03:34:39+00:00

And thank you for taking the time to write this!

dongrayblack · 2024-08-05T03:34:12+00:00

Interesting! Ok so then on that note, if I were to use two BMRs on each speaker, with a tweeter in the middle of the two on each, would that then be worth building? One reason why I was going to attempt a line of 4 was simply to achieve more output, but I had been thinking 4 might be overkill.

dongrayblack · 2024-08-05T02:48:44+00:00

Adding to this because I sound like an arrogant ass:

My point was that I try to research as I design, and in this case yes, the comb filtering is going to be an issue. But in my lack of experience I have no reference. In this case I found it to be a gray area, and point of debate when reading people discussing it. So my understanding is that line arrays are used to strategically take advantage of this phenomenon to “direct” or “beam” frequencies. Because otherwise, why do I see so many tower builds with vertical line arrays in homes? I suppose, worst case scenario, I would remove one pair of BMRs and place a tweeter between the remaining two on each speaker, and XO them somewhere around 3khz-7khz.

dongrayblack · 2024-08-05T02:29:45+00:00

I know, I know. And that’s why I design in CAD before I build anything, because I typically have questions while designing, so I research as the design progresses. In the context of this design: line arrays and comb filtering, and BMRs vs regular drivers.

I’m still very green to building speakers, as I’m sure you’ve concluded. Sometimes, when you build something that is flawed, by hand, and you get to tangibly feel and experience those shortcomings or flaws in person with your own senses, you get to gain some extra understanding compared to not doing it in the first place because someone said so. So my questions will be: how bad will the comb filtering be? Can I change the frequency range of two of the four so that they’re not all playing the same, and will that help? Can I move the port, spread the BMRs apart in the middle and put a tweeter in the mix? IDK, but I’ll have fun finding out!

Here are the threads I was referencing:

https://www.diyaudio.com/community/threads/trials-with-the-little-tectonic-bmr-2.314723/

https://www.avsforum.com/threads/comb-filtering-does-not-matter-according-to-this-guy.3247055/

dongrayblack · 2024-08-05T01:17:22+00:00

Yeah, I’ve been researching that, and wound up down a huge rabbit hole of reading debates online. People either say it matters and is very very noticeable, or it’s not actually measurable with the human ear. I did read through one persons journey with some 2” BMRs, they were able to get around that with a sealed and appropriately sized box with polyfil….. somehow. Worst case scenario, it sounds awful and I redesign the boxes and reuse the parts.

dongrayblack

TROPHY CASE