4th Order for Dayton HO

[gckless]

So I recently purchased a 2011 Impala. Seats don't fold down, but I have large openings through the rear deck. For that reason, to maximize efficiency and minimize rattles, I would like to possibly do a 4th order through the rear deck for a Dayton HO 15 or two (I have two available, but may only run one depending on box size). I would like to maximize bandwidth, playing at least 30-60Hz fairly flat. The flatter the in-car response the better. I will probably cross at 63Hz with either a 12 or 24dB/octave slope.

Question is, what kind of airspace am I looking at for both chambers and port size for one HO 15? And if I want to do two, will I exactly double the single driver enclosure dimensions or can I get away with a little less than double? Simply looking for space requirements, I'll worry about actual dimensions and specific port placement.

I understand that time is money and people do charge for designs. If no one wants to reply, that's fine, I understand, no hard feelings.

Or would I just be better off going with a sealed box rear-facing?

[zxsonnyxz]

To get things started from a veeery generic winisd simulation, if I had that car and woofer I would try 1.6cuft sealed and 1.6cuft ported (just happends to be a 1:1 ratio), tune at 65+- (would suggest retuneable port) and you won't need the LPF that low as the box will do most of that job for you. You could use the LPF to just dampen the top end slightly if it plays to high. I figure 8" port 14" long would be good on not too much power for a good sounding system. Of course if you'll slam it go bigger.

Seems like a very reasonable size for a bandpass for a 15" woofer, and I like theese type of SQ woofers that plays so well and low in small sealed boxes.

If you have space for both just double everythig up, and if it gets really tight you can go slightly smaller on sealed side and use polyfill. If you want it perfect you'll have to fine tune it as you test to suit your car, and if all else fails sealed backfiring is a good back-up plan

I've only buildt one 4th order bandpass myself, but the winids curve with a simple cabin gain approximation is comparable to what I hear in my car.

Would see what the experienced guys chime in with, but figure it won't hurt to share my thoughts.

[Triticum Agricolam]

Alright, I'll take a stab at this.

For the rear chamber size, I'd suggest around 2 cubic feet. You need to 1.65 cu ft to get the generally desireable Qtc of .707, I went a little larger to lower the Qtc a bit for more gradual low end roll off and lower group delay.

For front chamber size I recommend 1.5 cubes tuned to around 50 hz. Its seems like a small space and a high tune, but if you make it much bigger than that you are going to get a peak in output, with the higher tuning that will help get you good output up to your crossover frequency at 63 hz and cabin gain should help full in the low end. I would definitely recommend you make the port adjustable in some way so you can play around with the tuning frequency a bit. For port area I'd shoot for 35 sq in assuming you are going to be putting around 1,000 watts to this thing.

Here is what my suggestion looks like with (green) and without (red) roughly approximated cabin gain:

[gckless]

Alright, I'll take a stab at this.

For the rear chamber size, I'd suggest around 2 cubic feet. You need to 1.65 cu ft to get the generally desireable Qtc of .707, I went a little larger to lower the Qtc a bit for more gradual low end roll off and lower group delay.

For front chamber size I recommend 1.5 cubes tuned to around 50 hz. Its seems like a small space and a high tune, but if you make it much bigger than that you are going to get a peak in output, with the higher tuning that will help get you good output up to your crossover frequency at 63 hz and cabin gain should help full in the low end. I would definitely recommend you make the port adjustable in some way so you can play around with the tuning frequency a bit. For port area I'd shoot for 35 sq in assuming you are going to be putting around 1,000 watts to this thing.

Here is what my suggestion looks like with (green) and without (red) roughly approximated cabin gain:

Awesome, thanks man. I think this is what I'm going to do. Think I would be ok using a 6" aero? That's my max for an aero, or I could do a rectangular port with max dimensions of 6"x10" (outside). I think I could also do a pair of 4-5" aero ports, and actually that config would be safer against driver unloading to the port inside.

I would use the front chamber size for port length calculations right?

[Triticum Agricolam]

Are you planning on running one sub or two? How much power are you going to be running?

The front chamber is the one used for port length calculations.

[gckless]

Are you planning on running one sub or two? How much power are you going to be running?

The front chamber is the one used for port length calculations.

Just one sub. Your above calcs were for one right? Don't see how that could be for two. Amp is rated for 960W, so maybe like 800W at MOST clamped.

[Triticum Agricolam]

Yup, what I posted was for one sub.

With the power you are going to run a single 6" port will probably be fine, but I wouldn't suggest any less than that.

[gckless]

Yup, what I posted was for one sub.

With the power you are going to run a single 6" port will probably be fine, but I wouldn't suggest any less than that.

Ok. I'll stick with the single 6" or a pair of 5". 5" PVC shouldn't be hard to get, and cheap, so as long as I can fit the length for them I'll go that route. Making it adjustable might be tough, the end on the box is the only end I'm going to be able to adjust. Plus not really sure how I would do that other than a PVC coupler. Might need small access panels. I was going to just make the whole front removable, but I want to be able to brace that, so I might just make a smaller access panel just large enough to fit the sub through.

Edit: Well apparently 5" is not a standard size for PVC. Go figure.

[Triticum Agricolam]

If you want to use 5" ports you may be able to find some 5" mailing tubes. Just an idea.

[gckless]

If you want to use 5" ports you may be able to find some 5" mailing tubes. Just an idea.

Only place I could find was pretty expensive.

How far do I need to be from a wall on the inside port opening? I always figured same distance as the width of the port. Which would mean to get 50Hz length in a 1.5 cube front chamber, I would need to turn it. And 5" elbows aren't cheap. Can I do anything here to shrink the length? I know either raising tuning or increasing box volume would do that, but anything acceptable is what I mean.