Horn/TL combo

OK. So I think i got my head rapped around this thing a little better, but have some questions. In a TL, the thing that determines whether it is expanding or tapering is the location of SL or the open end. If open end is larger, then it is an xpanding line/horn. If the open end is smaller, it is a tapered line or Tqwt. Driver positioning is always relative to the SO or closed end.
Using the open TL worksheet is easy peasy. Where things get hairy for me is when we get into a ML TL worksheet. The ML portion simply means that there is port somewhere on the acoustic line. Am I correct in thinking that it is this port that now determines the open end of the design, taking the place of SL in the open TL worksheet. It would seem that the MLTL sheet is geared more towards designing a BR, although interestingly enough, the response i get from the MLTL shhet does not match that from WinIsd.

I am going to try and model the same system in both worksheets and see what i get.
 
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I think i got it, just trying to confirm. Let me figure mine and we can compare....only if you promise to use as teaching exercise and not running joke:D

As for port. In my sims, moving the port around did make significant difference in ripple and cancellation of resonant frequencies. Bob Brines talks about the possiblity of canceling both 3rd and 5th resonant frequencies and I believe MJK has an example in his TQWT paper, but i cannot find the stupid link. Oddly enough, I cannot find many examples where people try moving the port. They mostly just change driver position. and shove the port to the bottom, i guess trying to take advantage of length to gain LF extension.
 
GM influenced me enough to abandon slot opening , so I think I got solution to have both square port and folded TL

Hmm, sorry to hear this as I'm not against them, just like anything else it just depends on the needs of the app as to what to use.

BTW, the pioneers of audio apparently understood the value of moving the vent location back up a [ML]TL as some would put the mouth of a rectangular or K-slot ducted port at the bottom and box in duct up the inside of the baffle, which is no different than if the port was located at this height from an acoustical design POV.

Where do you think I learned about such esoteric design considerations? Not much new, if anything, in [TL] speaker design.

Oh well, got to get back to gutter replacement.

GM
 
In a TL, the thing that determines whether it is expanding or tapering is the location of SL or the open end. If open end is larger, then it is an xpanding line/horn. If the open end is smaller, it is a tapered line or Tqwt. Driver positioning is always relative to the SO or closed end.

Am I correct in thinking that it is this port that now determines the open end of the design, taking the place of SL in the open TL worksheet. It would seem that the MLTL sheet is geared more towards designing a BR, although interestingly enough, the response i get from the MLTL shhet does not match that from WinIsd.

Correct and these definitions are mine and some others use to differentiate them, while others stick to the strict electrical definition of just 'TL', requiring further description that isn’t always included, sometimes causing considerable confusion as to who is recommending which TL alignment.

Right, the ‘TL’ is a ¼ WL resonator and the ‘ML’ [vent] is a ½ WL resonator in series to cause a summed tuning somewhere below these two differently tuned acoustical systems. As the vent is moved up, the path-length increases due to reflecting off the bottom of the cab, but the trade-off is reduced ¼ WL loading of the vent with a notch in the response that can become audible if moved too close to the driver.

Of course! A typical reflex program assumes a ~uniform particle density of the cab’s trapped air mass ‘spring’ whereas a MLTL has more powerful [stiffer] ¼ WL resonant action exciting/damping the vent with the trade-off that the MLTL must have a high aspect ratio and greater net Vb to have a comparable frequency response.

GM
 
Seems I only know how to design BR speakers. As GM said, I can stuff it flat, but seem to be failing at getting it clean without. Maybe this is good. Sure as hell is big, coming in at about 16ft^3. Probably too big. I am open to further correction again.
 

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Like most folks, you look at any speaker sim not billiard table flat as unacceptable, but the reality is that only a vanishingly low percentage of folks living in today’s society of high ambient noise have the ability to hear well enough to notice these small phase ‘burps’ and even then most are female and lose it before adulthood and why I relied heavily on my daughter and other young women to ‘voice’ my critical listening builds and do audible perception experiments.

Anyway, FWIW, Altec recommended a minimum 8 ft^3 sealed up to around 18 ft^3 vented if tuned to Fs, but the latter assumed a high output impedance, so today this equates to a ~ 9-10 ft^3 tuned to 35-40 Hz alignment. If a matching impedance, then sealed Vb = Vas up to IB, so you’re still thinking ‘small’ ;) for this driver if you want it ‘to be all it can be’.

GM
 
Apparently I am not going to be all I can be. I could narrow front and deep sides, but i would lose 4 feet of room if i want to pull them out any. I sitting here looking at a tiny 20' x 28.8" x 40", 13.5 ft^3(inside) and thinking if I can pass it off. What would you recommend in the 10-13ft^3 range?

Nother thought that came up last night in regards to big enclosure. What about stuffed U Frame. I grew up listening to old Alnico Guitar speakers in crappy little uf rame boxes with a back and they had plenty of tone and low end. I believe I have read that the Altecs like some dampening and wondered if somthing like this would work.

Dunno wha to do. Wna tt let these babies sing, but it has to be presentable or I will listen to them all the time because I am sleeping on the couch.
 
I don't recall you listing any max LxWxD limitations based on local conditions, but sounds like whatever it is, it is what it is WRT available net Vb and if they will be used both near and away from room boundaries, then you’ll need two sets of EQ settings to maintain some semblance of balance between the two.

WRT guitar amps, you didn’t hear any real bass out of them, just very strong mid-bass, though backed into a corner to create a pseudo corner horn can be sufficient for most consumer musical recordings. Do you have two good corners available?

GM
 
I didn't said that you're against them (slot openings) , but I understood that with square one I'll need less tweaks later

or - in other words , no need for test boxes

Square? For the life of me I can't recall recommending them. Round, yes, since they can be easily slid in and out for trying different lengths, though it needs some blu-tak or similar to temporarily seal them.

GM
 
I don't recall you listing any max LxWxD limitations based on local conditions, but sounds like whatever it is, it is what it is WRT available net Vb and if they will be used both near and away from room boundaries, then you’ll need two sets of EQ settings to maintain some semblance of balance between the two.

WRT guitar amps, you didn’t hear any real bass out of them, just very strong mid-bass, though backed into a corner to create a pseudo corner horn can be sufficient for most consumer musical recordings. Do you have two good corners available?

GM


As for local limitations, I really need to keep it visually reasonable. Based on past conversations, it would seem that a vertical driver position of 32" will help with room modes(1/3rds and fifths). They will be in the corner of a room that is 14' x 32', but i will be sitting about 16' from the wall. That makes listening position about 10-12'. The speakers should end up about the same distance apart being in the corners of the room. The bigger they get, the more pulling them out becomes a problem(although i will haev the possiblity of sliding seating postition back). I have been playing with 20" x 28.8" x 40". This is getting to the max height wise, considering that these are internal dimensions. Wider and deeper are possible in limited degrees, only because I cant have a fridge and would like to keep attractive proportions.

I played with the software some more last night and cam to realize that it is practically impossible to get a non BR response from a cabinet unless it is Vb ~ Vas. This is assuming mass loading and traditional rectangular shape. If i model a tall expanding tqwt and not fold it, things change.

Just interested in opinions. I would like to see the inside of the MLTL that you designed for the 416 that is linked earlier in the thread. I am getting tired of modeling. Saw finger is getting itchy. I will comfort myself with the horns for now.
 
So i have pretty much decided on a size and have just a few follow up questions.

Would have curved sides eliminate the need for high width/depth aspect ratio? Right now, looking at 42,28,20-24.

Time alignment is going to be an issue, but i think it is solvable. If i move the driver halfway down the baffle, i get a superior response in almost every way, but the will create phase issues correct? Ideally, dont we want the drivers within a quaterwave length, verticslly at the xover point?
 
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Time alignment is going to be an issue, but i think it is solvable. If i move the driver halfway down the baffle, i get a superior response in almost every way, but the will create phase issues correct? Ideally, dont we want the drivers within a quaterwave length, verticslly at the xover point?

Vertical separation between the drivers results in vertical lobing in the response. Keeping the drivers as close as practical reduces this.

Can you post a side view (cut-away) for the enclosure you are considering?

The response lobe may be "aimed" by adjusting the acoustic centers of the drivers axially with respect to each other. If you move the CD/horn combination forward, the lobe shifts down...and vice versa.
 
THanks Ed. THat is what I was assuming. My cabinet is going to look very similar to the one here. I will have a pocket included like he has that will allow me to slip the A290 horn in. THe cabinet in the picture is 47 x 25 x 24. Mine will end up being like his, but about 52" tall, and a little wider, and maybe not as deep. Appx final enclosure size will be about 14ft^3

Wardsweb DIY 3-way horns
 
Here is a view of my proposed enclosure. Still BR, unfortunately, as I hae yet to model a decnt anything else.

Showing two views. One with driver up in box and at 1/3 of room height. The other with driver at 1/2 bo and 1/5 room height. It is interesting how moving the driver to the middle as GM spoke of, affected the performance. It would seem like the same response, but the acoustical impedance and port pressure are quite dfferent. It would be interesting to hear the difference. unfortunately the middle position would create other issues. I am moving forward with this unless someone has any suggested changes.