XBL^2 hype, so what’s the disadvantages

[JCsAudio]

Most, if not all, of the XBL^2 subs are not ideal for ported boxes.

I’m starting to figure that out I think as the CSS isn’t modeling the best either but not bad. I’m wondering why that is without doing any research yet.

[ckirocz28]

I’m starting to figure that out I think as the CSS isn’t modeling the best either but not bad. I’m wondering why that is without doing any research yet.

They're geared more toward very small sealed boxes, purposefully. T/S specs are targeted for sealed boxes, that's the reason for the large Xmax, they need it for good output in sealed boxes.

[Oscar]

Decided to model the AF GB12 (orange) vs CSS SDX12 (red) vs Adire Audio Brahma (yellow) in the most ideal ported boxes that I could figure out. The Brahma really wants a huge Ported box so I went with a 2 cu ft which is the biggest I would use in a car for a 12. The Brahma is not really ideal for use in a ported box according to my simulations and is better suited for a sealed box but a DSP would be able to smooth things out.

Loving the commentary and great information that has been posted in this thread!

Attachment 7690

Brahma 12, but I get a very nice FR curve in 1.0 ft³ tuned to ~33Hz via a pair of 10" PR's

(so I guess I disagree with the Brahma wanting a large enclosure; generally speaking the figures of merit for vented enclosures [Qts^3.3*Vas*20] ≤ Vb ≤ [Qts^2.87*Vas*15], for a "maximally flat" vented enclosure volume with the best F3, with an appropriate tuning frequency)

Here is my Akabak model (bandpassed 20Hz/100Hz):







In fact, the current Brahma iterations have Qts values perfectly suitable for vented enclosures. Even the Brahma 15" has a very respectable Qts = 0.45.

[JCsAudio]

Oscar, I didn’t think about a passive radiator and I haven’t spent much time checking the Thiele Small Parameters to see if they are completely correct. I just loaded to specifications that were already in the program and let Bassbox Pro select the ideal box size. Later on I can revisit that and check.

Thanks for posting that information. I definitely don’t want to mislead anyone with incorrect information.

[Oscar]

Oscar, I didn’t think about a passive radiator and I haven’t spent much time checking the Thiele Small Parameters to see if they are completely correct. I just loaded to specifications that were already in the program and let Bassbox Pro select the ideal box size. Later on I can revisit that and check.

Thanks for posting that information. I definitely don’t want to mislead anyone with incorrect information.

Well the PR part doesn't change anything really, as the response will be nearly identical to the standard vented box, but knowing the parameters is very important. But as you can see, you can get an awesome, pretty flat 4π response in as little as 1.0 ft bass-reflex (whether vented or PR), and probably even lower if you know how to factor in the cabin gain.

In fact, you can go as low as 0.7 ft³ and tune around 30Hz with dual 10" PR's to get a downward drooping response as frequency goes down, and it should yield a decently flat in-cabin response down into the 20's.

[JCsAudio]

Turns out Oscar was right and I had the parameters incorrect so I re-ran the simulations with the correct parameters. I also modeled a passive radiator box too which was about 1 cu ft. See below graphs and comparisons to AF GB12 CSS 12. Also attached are graphs for group delay, vent volume, passive radiator, and a PDF with all the information for passive radiator. AF GB12 (orange) vs CSS SDX12 (yellow) vs Adire Audio Brahma (red) vs Adire Audio passive radiator purple.

Adire Audio Brahma ported.pdf

[Oscar]

Your purple is "off" somehow. Or were you trying to mirror my cabin-gain compensated alignment that I posted? Even then it looks "off". What is your Vb/Fb for the vented alignment and for the PR alignment?

[Queef]

I like the ported over the PR graph for Brahma !

[JCsAudio]

Your purple is "off" somehow. Or were you trying to mirror my cabin-gain compensated alignment that I posted? Even then it looks "off". What is your Vb/Fb for the vented alignment and for the PR alignment?

I was not trying to mirror anything you did but let the program dictate the alignment for the PR. The fb for the ported was 31 Hz and 1.8 cu ft. I had a lot of trouble getting a 4” round port to fit in anything smaller for the Brahma. The PR Vb was around 1 cu ft and I don’t remember the fb. I’ll have to open my laptop again to check, maybe tomorrow.

[Oscar]

I like the ported over the PR graph for Brahma !

I don't think those alignments were identical. Programs don't always know what is what. Identically sized and tuned, with enough PR Sd, they will have the same graphs.