Maximum Bass for $1000

[Patrick Bateman]

Here's the response of an 18Sound 18NLW9600 (http://www.usspeaker.com/eighteensound-18NLW9600-1.htm) in a vented box. That's basically one half of a PK Sound CX800. (It wouldn't be fair to use the whole thing, because I'm setting the budget at $1000 and the 18NLW9600 is $700.)

The 18NLW9600 isn't quite as efficient as the TH-Mini...

But feed it three thousand watts and it beats the TH-Mini across board. As it should - the woofer is over three times more expensive, the box is bigger, and the power is higher. But YOWZA there aren't many woofers that can legitimately take three thousand watts. What a beast. To put this in perspective, that's TWELVE THOUSAND WATTS into two ohms.

If you want to model it yourself, here are the hornresp specs

[Patrick Bateman]

As noted above, the 18Sound 18NLW9600, as used in the PK Sound CX800, is winning this race. If you have a thousand bucks to spend, this is a tough one to beat. The pic above shows a couple of Alpine SWS-10D2s in a tapped horn versus the 18NLW9600 in a vented box. The 18NLW9600 isn't just louder, the box is smaller.

In this case, the problem is that the Alpine doesn't have enough BL. Basically it's low BL leads to a large box. But the Alpine *does* have more xmax than the 18Sound, and it's a fraction of the price. ($100 versus $700.)

It's tempting to try an isobaric here. That will reduce the box size and raise the power handling. But it will also lower the efficiency.

I can see why JTR is using a high efficiency driver with high xmax. The Alpine's efficiency is too low, but it's xmax is great. The 18Sound has high effiicency, but it's xmax isn't as good as the Alpine.

Something in the middle would be perfect. Not sure what that would be though.

[Triticum Agricolam]

Alright, you have piqued my interest in your TH-Mini clone. Do you have any plans for it?

[Patrick Bateman]

Alright, you have piqued my interest in your TH-Mini clone. Do you have any plans for it?

Check out the thread "the smallest tapped horn" over on diyaudio

If anyone's interested in buying mine, I've posted it a few times on Craigslist for $80. It's loaded with a P-Audio SN12-MB. The driver itself sells for $120, so you're basically getting the driver at a discount and the box for free. But there's a reason for that; my craftsmanship is terrible and I can't make a good looking box to save my life. But it works.

If anyone wants it, I live in San Diego.

[Patrick Bateman]

I've had good results with Celestion. They're owned by the same company that owns Kef, and their engineering is consistently good.

So I tried designing a tapped horn like the TH-Mini, but enlarged to fit a 15". The Celestion FTR15-4080F. It sells for about $200 each, or 2/7ths of the price of the 18Sound Eighteen that's in the CX800.

Here's another pic of the TH-Mini folding, to give you a general idea.

Unfortunately, this didn't work much better than the B&C 12PS100. The output level is still inferior to the vented box with the 18NLW9600. (Note that the vented box needs way more power.)

It looks like the only way to beat the 18NLW9600 is to go isobaric. Here's a sim with four of the Celestion FTR15s, in the exact same box as above, but this time isobaric. By going isobaric we raise our power handling, raise our displacement, and the box size is about the same.

We *finally* exceed the output of the 18NLW9600. But this comes at a price! The 18NLW9600 is $700, and four of the Celestions are $800.

That 18NLW9600 is really tough to beat.

[Patrick Bateman]

As mentioned earlier in the thread, I'd like to see how the JTR Growler performs, but I can't find any woofers that seem to "fit" in a design like that. I know that JTR's drivers are custom built.

I would speculate that the ideal driver for a box like the JTR would have a 12" cone, a 4" voice coil, an FS around 50hz and an xmax of over 20mm. There are plenty of prosound drivers that meet the first three criteria; I am not aware of any that meet the last. There are plenty of car sound drivers that are the right size and have high xmax, but their FS and their BL is too low for a horn. I've heard that some have used TC Sounds drivers in Lab Subs, and I already have a pair of DIYMA 12s which are fairly similar, so I thought I'd see how those would fare.

When I measured my DIYMA 12s, the specs were way WAY off the published specs. I think this may be a combination of their age and the fact I haven't used them much. Basically, I think the Thiele Small will probably get closer to spec after I run them for a few hours.

Based on that logic, here's the params I am using. These params are an average of what npdang published ten years ago, and what I've measured.

fs = 26.3

qes = 0.5

qms = 6.18

qts =

vas = 42L

re = 3.7

xmax = 20mm

vc dia = 3"

Here's npdang's params : http://www.diymobileaudio.com/forum/car-audio-classifieds/57117-diyma-12-sub-clearance-until-supplies-last.html

From the specs, you can see that it's *close* to what I'd think JTR would use for the Growler, but the FS is too low.

But let's see what it can do...

[Patrick Bateman]

Wow, that worked really well!

My lowly Diyma12s, which I bought for something like $100 when npdang was clearing them out, don't just match the 18" 18Sound woofer, they exceed it!

I'm kinda shocked. I've had these in tapped horns, and they worked well, but I don't think I've ever even considered them for a front loaded horn. I think I assumed that the size would be completely out-of-control. But it's really not too bad at all, because the VAS is so low and the BL is so high.

The simulation above shows the $700 18Sound 18NLW9600 in a 100 liter vented box versus the $100 Diyma12 in a 100 liter front loaded horn. Even more shocking than the ridiculous performance of the DIYMA horn is that it's not even CLOSE to it's xmax. So I'm thinking it might be possible to reduce the box size a little further by finding a 10" woofer with similar specs.

Which is what I'll do right now...

Basically we want a 10" that looks something like this:

fs = 30hz

qts = 0.46

xmax = 15mm or more

vc dia = 3" or more

[Patrick Bateman]

While the DIYMA is a nice woofer, and I already own it, the sims seems to indicate that we can get away with something smaller than a twelve, in exchange for a smaller horn.

IE, a single 10" in a horn may be able to keep up with one of the world's best eighteens in a vented box.

Here's a sim comparing the Alpine SWR-12D2 versus the Alpine SWR-10D2 in a front loaded horn. The Alpine twelve is in a 100 liter box, the same size as the vented box for the 18Sound 18. The Alpine ten is in a 75 liter box, 25% smaller than the twelve.

You can see from the sim that going with a twelve doesn't buy you much; about one decibel more output, and a box that's 25% bigger. The law of diminishing returns in full effect here.

Here's the excursion. Very close.


Here's the specs, if you want to sim it yourself.

I think the 10" is a nice design, but now I have a new problem. I'm exceeding the RMS rating of the woofer... by a lot. The Alpines are good for 300 watts, and I'm feeding them 1200 to get to these levels.

But the good news is that I'm not exceeding xmax.

So I think the next step, to take this a little bit further, is to do this:

1) find a woofer with an even smaller cone (since I'm not exceeding xmax)

2) and use a pair of them, or even four (to maximize power handling.)

Basically I need to find a woofer with higher power handling now, or use an array of woofers to raise the power handling.

[Patrick Bateman]

I tried simming the horn with a couple of the JBL Differential Drive woofers:

1) The 15" worked really nicely, but the box got HUGE. Due to the high VAS (six cubic feet) the horn grew to sixteen cubic feet in volume. Ouch. On the upside, if you need a REALLY loud front loaded horn, consider the 15" JBL differential drive woofer!

2) The 12" worked about as well as the Diyma12. I'd probably consider it, but I'm not convinced that it would be much of an upgrade. The efficiency was a tiny bit higher, but the woofer would cost me about $400 delivered. I'd really like to find a solution that would offer significantly more output - at least 3dB - for about $300ish

[Patrick Bateman]

I know this is a long read, but I'm close to a winner here.

I tweaked the Alpine box by adding a second SWR-10D2. With 69.28volts, that gets us to an SPL that comfortably exceeds the 18Sound 18" across the board. At 60hz we're 6dB louder.

I'm cheating a bit here; the Alpine is a 2ohm load and the 18Sound is a 4ohm load. But the 18Sound is maxed out anyways, because it's displacement limited. The Alpine may be thermally limited here, but I feel comfortable that the Alpine can withstand short bursts of 1000 watts. I'm certain the 18Sound can't exceed it's xmas, so 125dB is "the wall" for a single 18NLW9600. (Unless you tuned it higher or narrower, which I don't want to do.)

This is an affordable box; about $300 for the woofers and under $100 for the wood.

But I already own some Alpine SWS-10D2, so next up I'll figure out how much more output you get from the Type R vs the Type S.