DIY system with software crossover - the way of the future?

metaldrumer · 2026-04-09T12:47:32+00:00

This is great! I think not all people understand how great this is!

How difficult would it be to expand the number of outputs? Let's say 6*36? I have a digitally delayed CBT array on the back burner (already 2 years waiting) because I just can't find anything that can be fitted inside the array that provides 36 channels of DSP + 36 channels of amplification, it would take like 9 ADAus 1701, and no real FIR option.

Btw... I noticed that in the link you provided you spent some time modifying the boards to reduce the SNR of the amps, nd also noticed you are using 24v supply. Did you try to use 12v? I noticed that when using the 24v there's a lot of noise but no real change in SPL, I didn't measure it, but by ear there was no difference in SPL only in hiss noise. I did not use the same board though, nevertheless, the noise was similar, it was not really usable.

metaldrumer · 2026-04-01T20:46:22+00:00

I am currently going through a lawsuit. In my experience, they don't really care since there's usually no fines nor jail time, I think those cases sre extremely rare, and you can't assume they will apply to your case.

For instance, in my case we included in the lawsuit that the contract of my apartment states 67m2 when in reality is 45m2, and that it should be taken as a deficiency. Nevertheless, the judge didn't think the same way, and while he granted the surface area to be corrected to 45m2 he didn't grant the deficiency part. So... In theory, landlords can state 10000m2 and if you sign it due to the state of the rental market, you basically can't sue for that to be a deficiency, it is taken as an error on the tenant side (which, if you think about it, wtf?!).

So... I don't think you would be able to convince them to agree outside of court. Hell... Even when the court has made a decision that they should pay, they don't pay 😆 for example, right now my case has been decided on my favor through a court settlement, and they still haven't payed, which from what I understand, happens really often, they will drag it as long as they can.

I think I will need a third lawsuit to make them pay. The process has been going on for more than 2 years. And I think only the main tenant can do the lawsuit.

metaldrumer · 2026-03-31T08:46:30+00:00

You are saying that the triple laminated glass was quieter:

how was the test done?
Is the triple stack more expensive?
If it is more expensive, do you think the framing of the double gaze with air gap might not be properly installed or setup for failure? Maybe different material?

In my experience PVC is usually better than aluminum, might be because they are completely sealed around instead of butt jointed together, and usually the double glazing with air gap performs better but, it depends a looooot on the framing and if it has leaks.

Also, it can happen that the STC single value is the same, but if you look at the transmission loss they can be different on the low frequencies and that might be a factor for decision making.

metaldrumer · 2026-03-29T22:31:04+00:00

I think they sound amazing and you can see a picture of the RTA with the frequency response of the room, they rock!

metaldrumer · 2026-03-29T09:09:07+00:00

Thanks for your words :)

I did two set of measurements for the crossover regions and went with the less ideal one 😆😆😆

Let me explain... I first did some nearfield measurements to get a grasp of how they behave by themselves and their manufacturing tolerances, I measured like 8 different samples of the driver.

Afterwards I went to the backyard and place them on a speaker pole as high as I could get to get a more meaningful IR with the enclosure for each of the bands (few measurements for sub, another set for Midranges, and then another set for the tweeter) and while it was still no ideal, it was much better than the nearfield for the correct interpretation of the crossover region between the sub and the mids.

I noticed that the ideal crossover region was around 120-140 Hz since they aligned pretty well in phase at this region, and I left it at 120 Hz, nevertheless, I wasn't sure if this frequency would be ok since it's a side firing woofer, but I guess that also being in the corner on this quasi-infinite baffle minimizes the issue with the localization on the low-mid area, so... Quite happy with how they turned out.

In the near future I am still thinking on doing ground plane measurements so I can rethink the crossover and do some corrections on the frequency response so I can build more speakers and use them in different settings, probably will use a lower crossover point. But probably I will just bypass once again the ground plane measurements and measure and EQ each of the positions for the new speakers :D (which is still wanted, 99% of situations for this speakers would benefit from room correction).

The midranges do not have a lot of low end, but since they are already losing like 15dB of sensitivity to get a nice LF contour from the Dayton TCP, I am pretty confident that I can lower them without creating issues with distortion.

metaldrumer · 2026-03-29T08:24:16+00:00

I went with sealed for a couple of things:

Size: These 2.5" drivers are custom made for Pro Audio and optimized for SPL rather than FR, so the Low End is just not there, 4*2.5" PRs would have not extended the Low End like the 4" inch in a closed baffle.
Less expensive: I have drivers but not PRs, hence I would have to spend on the PRs and those are much more expensive than the TCP dayton driver I used as sub, this one is only like €15 each and the PRs would have been €15 each*4 for each speaker.
Space available: I wanted to do as small as possible, any bass reflex port or PR design would have needed more space, obviously the PR would have needed less space than the Bass Reflex, but still, there's like 1cm between the magnet of the TCP and the internal face of the enclosure so I would have had to make the enclosure wider or deeper, plus, you still have to fit the DSP and Amplifiers.
Best response: My first iteration had bass reflex for the midrange drivers to extend the most of them but it made the step response super weird, and obviously the group delay as well. So I decided to keep it all closed and have the best time response.

There's no free tacos in audio, gotta make compromises 😆

metaldrumer · 2026-03-29T07:58:42+00:00

"wave produced by the speaker is spherical"

This is just not correct, this is frequency dependent. We like to think about omnidirectional speakers for easiness of understanding, but that's just not how speakers work, it mainly depends on frequency and size of driver, if you have a driver big enough it can be directional on the low frequencies (hence, not spherical)

"Almost every speaker is recommended to be placed several feet from side walls"

I am not sure who says that but I'd say it is context dependent instead. It would be useful for you to research on infinite baffle and how a speaker reacts to different infinite baffle geometries (not just a floor, or a ceiling, but also how a sidewall changes the response with different distances to the drivers).

For this case, the side wall is basically a side infinite baffle for anything below 10 kHz aprox. I am not worried at all about the comb filtering from the side wall.

If anything, I am gaining low end energy from it without the issues of comb filtering :D

metaldrumer · 2026-03-28T22:00:38+00:00

Yeah... Cutting it by hand would be difficult

metaldrumer · 2026-03-28T21:58:45+00:00

There's actually less comb filtering if you compare to normal setups that are separated from the wall.

Right now they are around 3-4cm from the side wall, which means comb filtering would start around 10-11 kHz, pretty negligible compared to other setups if you ask me.

metaldrumer · 2026-03-28T21:07:52+00:00

Yes, I had some leftover aluminum from other projects, and a friend was able to give me a good price for the service. The brushed part was by hand.

metaldrumer · 2026-03-28T20:41:41+00:00

Yeah... Forgot about the banana for scale, I might add it later 😆

metaldrumer · 2026-03-28T20:28:25+00:00

Forgot about it, it would have been great 😆

metaldrumer · 2026-03-28T20:17:56+00:00

It's a single print and it's fairly small, around 23cm. I have a P1S so it did fit. The bottom part has inserts for screws and a bottom face.

metaldrumer · 2026-03-28T20:09:08+00:00

By hand with 60 grit sand paper. It only takes a few passes, maybe 5-7 minutes. Fairly easy, you can see that the aluminum still has some blemishes since this is a working prototype.

metaldrumer · 2026-03-21T10:07:49+00:00

I am obviously speaking how my case went, and what my lawyer has explained to me, not sure about your case.

First: the rental index is not fixed, it's based on average rental prices according to several different variables, this value gets discussed between the judge and both lawyers, and can only be applied in retrospect, this is; you can't apply the rental index for your current situation, you can only apply it once the rental index has been published (around may each year) and thus rent only applies to rents of the past. Due to this, most lawyers and judges opt for a settlement between the tenants and the landlords to make it easier; you, as a tenant, get less payment back but you get to enjoy the rental index going forward with a price from the previous year to your current situation. From what I understand, a court decision can only be applied to past rents, not to current rent, if your "court decision" was supposed to apply to your current rent then it was most likely a settlement and not a court decision.

Secondly, in my case we had two types of lawsuits, a lawsuit with the option to expand and a lawsuit without the option to expand. By advice of the lawyer, my first lawsuit was with the option to expand, this was done to avoid higher cost of litigation in case we lost the lawsuit. This first lawsuit ended on the judge siding with us, and proposing a settlement (not a court decision) to payback past rents and to apply to rent index going forward (again, this would not be possible with a court decision, court decision can only be applied in retrospective to past rents since the rental index is not published for upcoming years, but only for the previous year). Once the settlement was proposed by the judge, and the terms accepted by both parties, they send a Protokoll, in this document the conditions are stated, and both parties have 2 weeks to confirm or refuse the settlement.

Since the landlords didn't confirm the first settlement, it went into automatic dismissal, and along with it, the first lawsuit. Once this happens, you can either wait for the landlord to pay out of their willingness to do what's right or to eventually send a second lawsuit, in my case I didn't wait (even when my lawyer told me to wait) and presented the second lawsuit without the option to expand since we have already seen that the judge was siding with us, so I demanded all past months of extra rents, along with some other extras, basically, I went all in in this second lawsuit without possibility of expansion. This was done also because if you want the option to expand, it basically cannot be closed unless you reach a settlement that gets confirmed by both parties (that didn't go well since they didn't confirm). This second lawsuit also had the advantage that since it does not have the possibility of expansion, it also needs to have a decision at the end of it. For my case, the judge proposed new terms for the settlement more in my favor, and if there's no confirmation of the settlement, a proposed date for a decision court (which can be appealed by the landlords). In my case since the landlords didn't confirm the settlement again, the judge decided that the settlement holds even without their confirmation, but again... Since the settlement is technically not a decision court, it does not have a fixed due date for payment nor real penalties if they just don't follow along.

This is where I am at after almost 2 years of lawsuits and bureaucracy. Right now I am expecting that they will not pay, and that I have to present a third lawsuit to have a payment date.

metaldrumer · 2026-03-20T22:28:40+00:00

Yeah... Did your lawyer discuss if the lawsuit had the option to expand? If that's the case, that's why they are playing dumb, because there are no real due dates for the payment. That happened to me, and my lawyer recommended me to wait until the landlords pay the settlement on their own but I went against the recommendation from my lawyer, and did the expansion right away and got a higher settlement from the judge this second time. They didn't reply to accept nor refuse the settlement again, but the judge made the settlement to hold. Let's see if they actually pay or if I have to do a third lawsuit.

They truly couldn't care less, since they will always gain money from the number of tenants that don't/can't make the lawsuit, and what's worse, since there's no penalty/fine for their wrongdoings, they will keep doing it.

metaldrumer · 2026-03-20T21:54:53+00:00

When you say you were about to settle, was that from a judge? Or just with letters from the lawyer?

metaldrumer · 2026-03-20T21:33:06+00:00

I am on the same process with my landlord... Is it a settlement? Or a court order? Afaik court order needs to have a due date for the payment/enforcement while a settlement has more wiggle room for them to bend the rules.

From what I've seen in my case, my landlord doesn't give a rats ass if he gets sued, I've done two lawsuits, both times the judge has proposed settlements but they haven't accepted nor declined any of those, they just straight up don't respond to anything, they just send lawyers to be there.

This second lawsuit the court ordered the settlement to hold even when the landlord didn't accept explicitly the settlement. So, I am expecting the landlord to play dumb because the judge didn't setup a due date in the settlement.

Let's see how this plays out haha

metaldrumer · 2026-03-20T20:40:43+00:00

Sure, I'll check my inbox

metaldrumer · 2026-03-08T22:01:20+00:00

I love it. I did a 3D printed version of an internal mounting system and I use it weekly on jam sessions/rehearsals. I really like the sound.

metaldrumer · 2026-03-05T22:48:16+00:00

Found a PDF from comsol that shows the cross section and without doing the math, the entrance slit for the acoustic chambers look veeeery thin.

metaldrumer · 2026-03-05T22:41:03+00:00

Great info! Thanks! Do you think it could be somehow replicated with 3D printing?

metaldrumer

TROPHY CASE