Critique this TQWT

[pjanda1]

I'm working on a design for my brother-in-law, who's domestic requirements for cabinet size are a little more strict than mine. I've been playing with TQWT's in horn response, and I like a couple of things about them. If the sims are correct, I can get quite a bit of LF gain, which I hope will lessen the need for BSC (maybe even eliminate it against a wall). They also seem to limit driver excursion to a greater degree than comparable vented alignments, which I feel helps cut down on distortion with wideband drivers. Finally, I just like the idea. Something like this (what used to be referred to as a TL) has some simple old school charm.

GM posted a 10:1 design for this driver, but that won't fit in the size limitations of my brother in law. I'm looking at something with less taper, and then I plan to fold it. I've looked at a couple of different methods for folding, and done some sims with untapered sections. It looks like I should be able to get something of similar volume and taper (or progressively smaller sections) that will perform similarly and end up in the neighborhood of 12Wx14Dx42H. I'll mess with the folding layout later, but for now, I'd like any folks who have an opinion to take a look at the basic pipe. I'm not saying I'll be deterred (I am stubborn), but I'm open to suggestions. This design may end up on my commercial site at some point. If that bothers you, feel free to refrain from comment.

pj

[rjbond3rd]

Hi PJ,

1. Driver? I'm assuming BetsyK?

2. What's the driver offset (Z-driver)?

3. Doesn't .5 pi mean corner loading, as opposed to wall?

Yes, I am a newb.

[fwater]

Hornresp doesn't have a provision for changing the location of a vent in a ML-TQWP, but adding a 5" diameter hole at the end of the line in replacemant of a regular mouth tames a big peak at 175Hz and valley at 300Hz. It also gets a few more Hz of extension before xmax is breached. There is a cost of 1.5 or 2 dB in output around 50Hz and up, with a slight gain below 40Hz. I ran these numbers at 1Pi to be realistic and set the path length difference in the combined response tab at -40 to simulate placement near a back wall.

Anyone know a rule of thumb in regards to response behavior when moving the z of the vent in a ML-TQWP?

[pjanda1]

The driver is 18.5cm down the line. When using the offset driver function, the driver is between the first and second sections. It is indeed the Betsy K. And .5pi is corner loading, which in addition to increasing the level, boosts the bottom of the response chart a it compared to 1 or 2 pi.

fwater, my guess is that some damping will tame those peaks and valleys a bit. I'm hesitant to give up much gain unless it does seem rough in room. I am thinking of using a rear exit, which means it would be easy to add some quick-and-dirty mass loading.

pj

[fwater]

Indeed, a quick and dirty panel with a hole will go largely unnoticed. This is what I had meant to portray (but didn't at all) in my reply. Let me rephrase the whole thing...

Your numbers indicate an F3 of a around 50Hz with a slow rolloff, a decent amount of output, and the possibility (as you said) of not needing to add in a BSC circuit. What's not to like? Nothing, but the perfectionist in me ran some more numbers and if one were to add a panel with a 5" diameter hole...

Insert the rest of my previous message here. I would, however, recommend simulating at 1Pi because I can't see how corner-loading would have an effect here with no horn effect from the enclosure at all, but I can see a boundry reinforcement gain to be had if snuggled up against the wall, further upping the possibility of eliminating external BSC parts. Overall and either way, I can't see any reason to not try this cabinet. Well, maybe one reason...

Changing the driver z unsurprisingly has a large effect, but setting the z closer to the middle of the line to simulate a a flipped orientation with the terminus near the floor (thereby allowing a simulation at 0.5Pi in my amature mind) gives an enormous gain down low compared to a z of 18.5 and 1Pi for the traditional cabinet orientation. Even running in 1Pi gives a little bonus around the 40-50Hz area. The cost is more numerous and profound ripples, but nothing that can't probably be tamed with experimental stuffing. Run the numbers and compare to see if you might aggree.

[pjanda1]

I've been playing with it quite a bit this evening, and I'm getting less excited about the idea. If I move the driver down, I screw up my ability to fold it as I had hoped. I think the TQWT has great merit, but it probably needs to be left tall with a decent offset. I've been sim'ing a basic ML-TL, and that road may be the path of least resistance.

pj