Thoughts on this QWTL design

[DLHgn]

What do y'all think of this design? 1/4 Wave T-line. Line area is 98 inch^2 and ~113". It's for a B2 audio IS12v3. Fs is 32.1 Hz but drops at least 2 if not up to 4 Hz after break in (this is what the owner said). Sd of driver is 75.4 inch^2. Will either be using 3/4" MDF or Baltic Birch depending on my budget when I get to making this.

Driver T/S paramters can be found here: http://www.b2audio.com/is



Thanks in advance

[DLHgn]

Also, how would you model this in hornsrep? I don't think i'm using the program right. I tried recreating a project I had on WinIsd and they had no where near the same graphs.

[Triticum Agricolam]

That would be modeled as an offset driver transmission line in HornResp. I'm I the field right now, but I can help you with HornResp when I get in.

[DLHgn]

That would be modeled as an offset driver transmission line in HornResp. I'm I the field right now, but I can help you with HornResp when I get in.

I really appreciate it. I figured it would be and tried modeling that but I couldn't get the offset right.

[Triticum Agricolam]

OK, here is how the input screen in HornResp should look (roughly) for your design:

S1,S2, & S3 are the cross sectional area's of the line, since there is no taper they are all the same, 636.26 sq cm (98 sq in). FYI, you can select a field and hit F6 and then you can enter in imperial units, really handy.

L12, and L23 (shown as Par in my screenshot) are the line length. L12 is the line before the sub, and L23 is the line after. I guessed and set L12 to about 13" and L23 to about 100".

Here is the modeled frequency response:

Doesn't look too bad, but there is a pretty big peak around tuning. A couple things you could do to reduce are to tune lower and/or reduce the cross sectional area of the line.

To smooth out the frequency response you can try positioning the sub farther down the line, so increase L12 and decrease L23. Puting the sub 1/5 or 1/3 of the way down the line are common practices.

[DLHgn]

That's pretty much what my graph looked like but more peaky. I've read read about the 1/3 down and all that to help with the standing waves or modes or what not (need to re read that paper). As for the line area, I don't know how to reduce it because my sub mounting is 12.6" and the depth is somewhere around 5.4" or so. Any suggestions on how to decrease the area? Would tuning the enclosure lower have a negative impact on system as a whole. I can't get to my computer right now to do my own testing or I would.

[Triticum Agricolam]

To reduce line area you can narrow up your enclosure until its just wide enough for the sub cutout diameter. You can also make the segment where the sub is mounted deeper and reduce the depth of the line everywhere else. I can show you how to model a layout like that in hornresp if you need.

Another option is to reverse mount the sub, then you can make the line as shallow as you want.

Tuning lower will allow you play lower, and have smoother frequency response. The only disadvantage is it makes for a larger enclosure.

[DLHgn]

To reduce line area you can narrow up your enclosure until its just wide enough for the sub cutout diameter. You can also make the segment where the sub is mounted deeper and reduce the depth of the line everywhere else. I can show you how to model a layout like that in hornresp if you need.

Another option is to reverse mount the sub, then you can make the line as shallow as you want.

Tuning lower will allow you play lower, and have smoother frequency response. The only disadvantage is it makes for a larger enclosure.

I was trying to avoid reverse mounting if I could (it has to sit in my room and I don't know how good that would look) but it may be my only option. As for size, i'm really not too worried about that. As long as it's not ungodly massive i'll be fine. I was worried about making the panels too narrow for the sub cutout. My original design was 13x7" but I was worried that it would be too weak. One of my concerns about reverse mounting is how would I run the wire to the sub without it looking crappy? I would like to have as flat of a response as possible but how low of tuning could I go before it becomes too low for the sub? Again, sorry for not being able to model this stuff with you at the moment but I can't really get on my computer because I don't have a charger for it (using a school computer right now). As soon as I get a charger I will start modeling these things myself and really crack down on learning how to use hornsrep.

[DLHgn]

So this is the the graph and parameters screen I have





Looks pretty much the same. I'll try and play with the positioning a bit.

[DLHgn]

This is with 1/3 of way down line



And this is with 1/5 down



Not much improvement