50 year old old fart building a bandpass sub

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I want to design/build a 4th order bandpass box for my son's 2001 cavalier. I've looked over many posts and read Dickason's chapter on bandpass and have a couple questions.

What is a good vent tuning freq and bandpass to shoot for? Music selection is mostly rap but I'm trying to give my son a sub that will make him proud but meet my requirements for being at least semi-musical. Fronts will be 6" comps rolled off around 80 hz I guess.

How large of a driver do you really need? I've been playing with specs for 12" drivers and get fairly large encosures. My price point is $150 or less. I need something he can't easily destroy.

Does the vent need to be sealed to the rear deck?

I've built all types enclosures including front and rear loaded horns and tapped horns so don't hold back.

Thanks for the help
Jim
 
I don't know the size available in a Cavalier.
Because of cabin gain I would not worry about tuning low, with a correspondingly large cab.
If you get a chance to read Margerand's article in the SpeakerBuilder 6/88 issue. It goes into further detail on how a 4th order can be "jammed"for allowable ripple.
I built them back in the 80's and I tended to keep to a S =.7 and Qbp of.7143

Syd

(FWIW: I'm older than you are )
 
Last edited:
You'll probably end up tuning the box around 60-70hz with an f3 around 40-50hz. In car cabin gain is around 20dB's @ 20hz.
Measuring cabin gain? Need a little advice from the experts. - DIYMA.com
2516534482_b0d155d5ac_o.jpg
 

What is a good vent tuning freq and bandpass to shoot for? Music selection is mostly rap but I'm trying to give my son a sub that will make him proud but meet my requirements for being at least semi-musical. Fronts will be 6" comps rolled off around 80 hz I guess.
How large of a driver do you really need? I've been playing with specs for 12" drivers and get fairly large encosures.


More musical means design for wide band and shallow LF rolloff versus designing for max eff. ie one note bass. If you haven't tried Unibox yet, it is great for getting in the ballpark bandpass designs.
Seems a target size box 40-50 liters using a 10" sub driver s/be enough.
40 Hz -100 Hz

My price point is $150 or less. I need something he can't easily destroy.


You should also figure on using a line level steep rumble filter for over excursion protection. Depending on max power available use a settable attenuator to limit the power gain at the amp line in? Normal stuff for pro-sound not sure what there is for 12V systems. This may cut in your budget, but surely costs less over the long term. ie replacing burned and and bottomed out stuff.

Does the vent need to be sealed to the rear deck?


The kids long term hearing health?
 
I want to design/build a 4th order bandpass box for my son's 2001 cavalier. I've looked over many posts and read Dickason's chapter on bandpass and have a couple questions.

What is a good vent tuning freq and bandpass to shoot for? Music selection is mostly rap but I'm trying to give my son a sub that will make him proud but meet my requirements for being at least semi-musical. Fronts will be 6" comps rolled off around 80 hz I guess.

How large of a driver do you really need? I've been playing with specs for 12" drivers and get fairly large encosures. My price point is $150 or less. I need something he can't easily destroy.

Does the vent need to be sealed to the rear deck?

I've built all types enclosures including front and rear loaded horns and tapped horns so don't hold back.

Thanks for the help
Jim



It's difficult to tune a ported box without measuring the impedance curve, and bandpass boxes are even harder. (Because missing the tuning by a fraction of an octave can reduce efficiency, or create a huge peak.)

Do you have the ability to measure impedance?

If not, build something else. How about a tapped horn with a pair of diycable Anarchy woofers?

 
Here you go.

Reed Exodus Anarchy 25hz Tapped Horn - AVS Forum

Todd built them, I designed and tested them.

Any FR measurements for that TH?

What's the total volume of the box?

For cars, I usually recommend a simple design - while higher-order designs are efficient ways to use drivers, they're usually not the most efficient way to use space - important when you've only got a limited amount of space to work with.

For example, if that TH takes up ~2 cu.ft., that about the same amount of space two good 12" car audio drivers would take up in a sealed alignment (or perhaps two 10s in vented enclosures).
 
Any FR measurements for that TH?

What's the total volume of the box?

For cars, I usually recommend a simple design - while higher-order designs are efficient ways to use drivers, they're usually not the most efficient way to use space - important when you've only got a limited amount of space to work with.

For example, if that TH takes up ~2 cu.ft., that about the same amount of space two good 12" car audio drivers would take up in a sealed alignment (or perhaps two 10s in vented enclosures).

Oh, I don't disagree at all with the simplicity argument. This cabinet is not simple. :D

There are a lot of easier ways to make a sub that will give you 86 dB @ 1 watt, and do so flat from 25 to 100 Hz. Thing is - I did not set out to design a sub to meet those goals, I was playing around with tapped horns. Turns out that the Anarchy is a great driver for a tapped horn. No - it is not going to blow pictures off the wall or create any booming subsonics, but it does a very good job of making the bass you can hear at levels most people normally listen at.

I designed it to see if I could, and as several people expressed interest, I refined it, folded it, and shared the design. This came from the Insubnia project over at AudioKarma. This one showed me what is possible with a tapped horn. I am pleased with the results, and learned a bunch and shared all I can.

There are probably better topologies for this driver, hope some other people take the plunge and play with it, then share their results so we can all learn.
 
I built a pair of pair of Eric's 38 hz Tangbang tapped horns. They complement my FLHs using 15" JBL drivers nicely working from about 70 hz down to their rolloff. Very impressive for home but in a car my son would completely destroy those woofers even I could refold to fit the trunk.

Seems very roboustly built drivers are better suited for cars.

littlemike: I really like the Exodus project. I'm tempted to try it out if I thought it could offer a step change over the little 38 hz designs I have.

I also have a large 12" tapped horn on paper using one of pro Eminence drivers that I have not built. It will be a little over 7 ft tall with only one fold!

Cheers,
Jim D.
 
We actually measured one of Todd's 38 Hz tapped horns the same night. Those results are posted here. Red is with the inductor, blue without. These measurements are directly comparable to the Anarchy TH, they were done the same night, at the same place, with the same gear.

The Anarchy plays about 15 Hz lower, at essentially the same 1 watt efficiency, and takes the same power.

What's not to love? :D
 
Here's a thought WRT driver choice.

If it's going to be used in a car, then surely, an 8ohm speaker will be fine. Even with a bridged amp, he'll really struggle to get it warm, because there's not enough volts available ( (V*V)/R and all that...). The multi-kilowatt car amplifiers use 1 ohm loads, to get the current draw high enough.
 
We actually measured one of Todd's 38 Hz tapped horns the same night. Those results are posted here. Red is with the inductor, blue without. These measurements are directly comparable to the Anarchy TH, they were done the same night, at the same place, with the same gear.

I like the sound of the 38 hz TH with the choke in place. Are you saying you used the same choke with your Anarchy TH and got similar results?


What's not to love?
Absolutely nothing - very cool project. :cool:

Jim D.
 
I did not use a choke on the Anarchy. I try to avoid using large series inductors wherever possible. They're expensive!

If you look close at the measurements of the 38 Hz horn with and without the choke, you can see that the peaks are cut more than the valley. The choke is clipping a bit off the resonant peaks, less off the valley.
 
The Anarchy plays about 15 Hz lower, at essentially the same 1 watt efficiency, and takes the same power.

What's not to love?

So I thought after I did a TP sim that looked really impressive for only 24.75 L net, but then I did a simple BR of the same size and it made more SPL from ~ a half octave above Fb up to ~ 90 Hz, so doesn't seem worth the extra effort if true.

GM
 
In that statement, I was comparing the Anarchy TH to the Volvotreter 38Hz Tang Band design that I measured the same night, which was also mentioned earlier in this thread.

Believe me - I am well aware that the Anarchy tapped horn is not the most practical way to make 105 dB at 25 Hz. That in its self is not a terribly high bar to achieve, there are lots of better ways to get there. Since when is hobbyist-level audio about practical though?

It was a fun project, and it has opened a lot of eyes with respect to the design and construction of a tapped horn. I sacrificed passband gain for extension and a small cabinet. It seems to have worked out well enough in this case.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.