Jeep ZJ - Box and install advice

[boz25]

Hello group,
I just joined and looking for some advice. I am an MECP installer but have been out of the game for over 10 years now. I have a 1996 Jeep Grand Cherokee. And trying to decide what type of Sub box to put in it. Looking for all types of possibilities. I love the hard hit of a sealed box, but facing back not sure it will do what I want. I also love the low stuff you can feel. And I have never had a Band Pass personally before. Here is what I have right now.

2- JL Audio 10WX4 Subs that I repaired tinsel wire on.
1 - Kicker ZR120 with SWX Module
1 - Rockford Punch 400a4 (For mids and highs)
Lots of MDF.

So I am trying to decide what type of enclosure would be best. I talked to JL and got the recommended specs for a Band Pass enclosure. But is it going to worth the time, and space?

So what would everyone recommend I do?

Thanks for reading, Kevin

 

[reloader650]

Hi boz25,

Welcome to the Forum. I like sealed and sealed rear chamber bandpass enclosures for mobile audio. The bandpass enclosure is going to be harder to get just right, and may take some experimentation. I'm curious to see the bandpass design that JL gave you, could you post it here so I can sim it. One option you may want to consider is building a PPSL enclosure, there is some excellent info on this design in the subwoofer forum. As for the placement of the subwoofer, I have had good results pointing the subwoofers to the rear of the vehicle in hatchbacks and SUVs. Hope this was helpful.

Regards,
Matt

 

[boz25]

Hi Reloader,

Here are the specs on the subs first or anyone that might want them.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0ahUKEwiUwvvFtL_SAhVp1oMKHaqcBkIQFgg7MAU&url=http%3A%2F%2Fpdfstream.manualsonline.com%2F2%2F2899e0a8-2c9f-4d82-bb8c-10e86fdc1375.pdf&usg=AFQjCNFd9zOuibGvt9rBvFrREhMj9Kbr-g&sig2=B6fqitGD9yj5jqrxsZhIrw&cad=rja

And here is the Email that I received from JL (Modified to remove junk)
-------------------------------
E. C (JL Audio) - (modified to remove name)

Feb 10, 10:29 EST
Hello, for two 10WX band pass I would suggest 1.25 cubic foot for the sealed section net volume, 1.50 cubic foot net for the ported section with a 25 square inch port area. Port needs to be 7.5 inches long. For the port I would aim it toward the back hatch for loading effect. I would try to keep it about 1.5 time the width of the port away, but you could experiment to see what you prefer.


The volumes given are net volumes. You would need to add in the subwoofer displacements. The 10WX has a displacement of .032 cubic foot. The port can be a square or round port. You would need two 4 inch round ports to equal 25 square inches of port area. The box can be straight or angled as long as it is sturdy and each section has the appropriate net volume.

Sincerely,

E. C - (Modified to remove name)
Technical Support Specialist
954-443-1100 ext. - (removed)

-----------------------
So what do you think? Should I even bother with a nice box for these subs?

Thanks, Kevin

 

[reloader650]

Thanks for the info, and sorry for the delayed response. I had a chance to sim JLs bandpass along with the sealed and bassreflex found in the owners manual. For simplicity I simed only one driver. I think the bandpass could be improved some, it just depends on what the in vehicle response is. Bandpass boxes are kind of fun to build and tune if you like tinkering and experimenting. If you just want to build something quick and easy, and always sounds good IMHO, then just go sealed. Keep us posted. Pictures are always great.

Regards,
Matt

 

[boz25]

Thanks for the info. When you ran the model, what do you think could be done for better performance? Increase the size of the ported area? Also, what would happen if I did 2 sealed boxes in the back panels, firing at each other? And does depth affect the box acoustics? What if I made the depth very shallow, but really wide. Maybe I can draw something I had in mind and post it.

Thanks, Kevin

 

[Perry Babin]

Many years ago, a friend and I were testing enclosures. With equal volume, deep enclosures (think bazooka tube) did much better than flat enclosures (truck boxes for single-cab trucks).

 

[reloader650]

I had the same results as Perry, when it comes to shallow enclosures. I had a Toyota Tacoma extended cab pickup with a single 10" sub. The box was about 1 cubic foot and was deeper than the other dimensions. I wanted to make better use of the space behind my seat, so I built a new box with the same volume but was just deep enough for the driver plus 3/4" for the pole vent. I noticed immediately that something was different, not bad just different. Everything I have read says that box shape shouldn't matter, but it did in my case. Don't let this discourage you though. I only noticed the difference because I went from one box to the other in about 30 minutes.

As for the changes to the bandpass, I would probably swap the front and rear volumes and lower the tuning about 5 to 6hz. The driver will have a little less power handling 125 watt instead of 150. How it sounds will depend a lot on your vehicles bass transfer.

Regards,
Matt

 

[boz25]

Ok. I was thinking about making the box very low profile. As low to the floor as possible so I could still put cargo in, on top of the box. I am going to build today 2 sealed test boxes. I am thinking about building some pods in the rear behind the wheel wells, and pointing toward the rear glass to reflect to the front. What do you guys think about that idea?

 

[reloader650]

I think it's a good idea to build some test boxes. MDF is cheap. I like your idea of mounting the subs on each side of the cargo area, than on the floor. But I just thought of something, in the Jeep that I had, the spare tire was in the cargo area. Where is your spare mounted? Mobile audio is one big compromise. I guess that's why I like it, it's challenging. And fiberglass is your friend. Good luck and let us know how it goes.

Regards,
Matt

 

[jeff5may]

I used to build all sorts of custom enclosures at a JL audio dealer. One thing I can tell you about them is they Excel in single reflex bandpass enclosures​, even relatively smaller ones. The low bass extension and volume that comes out is just unreal.

Before you start building boxes, try to define what you are after. Bandpass enclosures​ in general have some trade offs. For one, you lose the midbass and smooth response in the upper bass frequencies that the brand is known for. It can be very challenging to blend the transition between the bandpass and the rest of the speakers. There also exists a trade off between SPL and useful bandwidth. The narrow bandwidth boxes are super loud, but very "one note" in character. The wide bandwidth boxes are super difficult to get anything resembling flat response out of, sounding "peaky" in nature. Depending on the transfer function of the vehicle, this nonlinear response can be used as a "naturally occurring" EQ function with seemingly impossible results. Many customers just do not believe that the vehicle doesn't have hidden subs in it.

For two, JL audio has done the math and homework with all of the speakers they sell, and they give their dealers much more resources than you can find on the web. When I worked at the shop, I had a literal set of encyclopedias for reference to decide what a certain customer would be best satisfied with. The information was spot on: on all of the tables, charts, and graphs, there was a highlighted "sweet spot" region depicted, and another "highly recommend" area. Going outside of these two zones, something was lost, be it power handling, linearity, SPL, or whatever. I would highly recommend visiting a dealership and establishing a point of contact so that you can tap into this vast resource.

As to the dimensions of the chambers, a short, wide volume has inherent deficiency versus something more cubic in shape. The larger surface area is much less rigid, leading to increased flexing of walls and resulting decrease in output. Also, there are many more interior standing wave issues that affect frequency response and raw output.

 

[boz25]

Been busy.

OK. So here is what I have done so far. I built 2 sealed test boxes to JL's specs. I am not very happy with the results. I think it might be the amp. I am running them off of a Kicker ZR 120, 4 ohm stereo. 30 watts according to the amp specs and has about the right power. It also has the Subwoofer module, I think SX is the model. They are very loud at about 60hz. Also have some pretty good kick! But the lower frequencies are terrible. I built a bypass module, since my deck has a sub crossover. But to much high end distorted bass but a smoother more flat response. I have not got around to moving the sub's closer to the rear yet. Keep forgetting. So that's my update so far. I found this pic and really want to do this. But not until I am happy with box volume.