Three HCCA 152 Designs

[Patrick Bateman]

Over on FB, someone was asking for an HCCA 152 design, so I thought I'd throw one together.

 

First off, for a bandpass box, I use the calculator from carstereo.com, and then I take the results and plug them into Hornresp. I haven't found a faster way to design a bandpass. Basically the carstereo.com calculator appears to use the formulas pioneered by Augsperger back in the 90s, which work great. It basically takes the guesswork out of bandpass boxes.

 

Hornresp is great for doing the actual simulation.

 

Here's the specs from Orion.

If what you're using is different (an older model perhaps?) please let me know so I can update the sim.

[Patrick Bateman]

 

Here's the frequency response using the 'default' parameters from the bandpass box calculator. This is with no tweaking, basically I just punched in the numbers and it spit this out.

 

This think is silly, with cabin gain it should exceed 152 dB at 140Hz. This assumes no thermal compression and no port compression. (A big assumption.)

 

 

Here's the excursion. Due to the high tuning, it won't exceed xmax as long as you put a high pass filter in series. (A subsonic filter.)

 

 

The box volume is just four cubic feet. The rear chamber is 56 liters, the front is 42, and the port takes up 11.347 liters. There are two port options: you can use four PVC ports that are 4" in diameter that flare out to 6" in diameter on each end. Or you can use ONE 8" diameter port that flares out to 12"

 

There's one LITTLE problem with this design, which is that it needs THIRTY THOUSAND WATTS to hit xmax. So, obviously, this "cookbook" design is no good. This is a problem I see with a lot of woofers that have a low VAS, it's hard to use up all of their XMAX.

So, stay tuned, I'll see what I can do to get the power requirements DOWN, because there's no way these woofers are going to withstand 15,000 watts each.

[Patrick Bateman]

Let's see what the published design does. It appears to be a bandpass, but the port and the front chamber basically "blend" into each other. This is actually a smart way to reduce turbulence.

[Patrick Bateman]

 

The published design is basically unusable. I guess it might be "neat" if you wanted a box that played one note over and over and over. This is basically a textbook example of why people hate bandpass boxes, this thing is terrible. (The black trace is the published design from Orion, the grey line is a "textbook" design I made, using a bandpass box calculator)

[Patrick Bateman]

 

I narrowed the bandwidth of the bandpass box, and made it bigger, yielding this. About 1.25 octaves of bandwidth and flat response in the passband.

 

 

Cabin gain generally adds about 24dB of output at 20Hz and 12dB of output at 40Hz. Here's what the response would look like with cabin gain.

 

 

With 3000 watts into 4ohms, it's not hitting it's excursion limits.

 

 

Here's the specs:

94.5 liters for the rear chamber, or you can use dual chambers, each with 47.25 liters

Sixty liters for the front chamber

There are four 4" PVC ports that are 4" in diameter in the center and flare out to 6" in diameter at the exit. The total port length is 19.78". The 4" ports can be replaced with a single 8" port that flares to 12"

You can build the box without flares but I wouldn't recommend that, flared ports perform better.

These three designs are kinda interesting, but this subwoofer isn't really optimum for a car stereo bandpass. It will work fine, but it's better suited for a home theater bandpass. Basically it has a ton of excursion that isn't getting used. Another option would be a very VERY high power car stereo bandpass, but I don't think the voice coils could handle it. If I was doing a bandpass that's about this large for a vehicle, I'd be using as much power as I could afford, with a woofer that's very very high power. Something like a Faital or 18Sound eighteen would be great in this application.

 

I really need to get some (real) work done today, but this woofer looks like an interesting candidate for a QB5 alignment. Basically a QB5 would move the resonance lower, taking advantage of this woofer's high XMAX and displacement. 

The downside of the QB5 is that it requires an electronic or DSP highpass, so it wouldn't be useful unless you have one.

 

Here's QB5, possibly my favorite subwoofer alignment : https://sound-au.com/qb5align.htm
 

[Patrick Bateman]

The first bandpass box in this thread, post #1, is tuned to 62Hz.

The second bandpass box in this thread, from Orion, is tuned to 61Hz.

The third bandpass in this thread is tuned to 50Hz.