Quad bandpass subwoofer design need advice!

[DJFUTILE]

I've been working on this design for many months now. I am no acoustical engineer so I'm unsure if it will have a good sound quality and power output etc. Any advice on design, dimensions, port sizes etc would be greatly appreciated! thanks

Dylan Winfield
Architectural Draughtsmen

PS. Please see attached file

[Solinar]

First off, your file attachment is corrupted. For those attempting to download it, save it to disk and add a .zip to the end of it to open it.

There is no way to answer any of your questions without a whole lot more detail.

1) What are the theile small parameters of your drivers?
2) What are all of the dimensions of your enclosure (chamber volumes, port lengths and sizes)?
3) what amp are you planning on driving them with?
4) What are your desired results (what kind of response are you hoping for, playing what kind of music in what kind of setting)?

Its a pretty picture, but there is no way to determine any semblance of a clue of how it would sound from the picture only.

In fact, answer all of the above questions and most posters here wont even need to look at your picture to answer your original questions.

[RJ]

I don't think you'll be able to get the port lengths that short unless the diameter of the port is small. Anytime you add a port to a box it's length increases. Small port diameters can create a lot of chuffing and chuffing sounds really really bad.

[BassAwdyO]

It is true the ports are probably too small in diameter. The best way to let us know how your design is setup would be a list of Theile/small parameters for the drivers and the internal air volume of the chambers with tuning frequencys.

One thing that seems strange to me is how the rear chamber is ported into the front chamber and the front is ported outside.
This should work OK if the rear chamber is tuned lower than the front(and the 6th order bandpass response is good), but port chuffing in the front ports will be even more of issue

In my experience bandpass enclosures really arent advantageous to sealed or ported ones. They require a much larger volume with only small efficiency gain and the filtering charachteristics are less than optimal. In my opinion you need a higher slope crossover with a bandpass enclosure!

[bwbass]

Originally posted by BassAwdyO
In my experience bandpass enclosures really arent advantageous to sealed or ported ones. They require a much larger volume with only small efficiency gain and the filtering charachteristics are less than optimal.

Ditto that.

Any extra effieciency you pick up from a bandpass design comes at the expense of bandwidth, usually in the form of less deep bass extension. Transient performance is degraded, and of course there is the port noise issue.

Good for a lot of upper-bass boom, if that's what you want.

[BAM]

You should have posted this in the Subwoofer forum, seeing as this topic is indeed about a SUBWOOFER.

[DJFUTILE]

I can't specify parameters yet as i havn't bought the drivers but I will find them out soon, I was thinking the Enclosure to stand around 1 metre tall (40"). this allows around a 2 inch space between each driver. Depth about 50cm with the internal chamber for each driver about 30cm. These are just rough dimensions until the parameters are known.