Natalie-P in a ML-TL, did anyone try?

[crazyjpeters]

Over at "some other forum", I read through the Thor redesigns, mostly work done by Scott Moose.

As well, he poked his head in here at HTGuide, and posted a few times on the Nat-P thread in the early stages, with a suggestion for a straight no-taper mass-loaded transmission line

https://www.htguide.com/forum/showpost.php?p=238306&postcount=176

https://www.htguide.com/forum/showpost.php?p=238431&postcount=180

https://www.htguide.com/forum/showpost.php?p=238657&postcount=185

I'm contemplating this as the cabinet for a Nat-P build. However, if anyone out there has bothered with a MLTL, and can compare to the usual Nat-P builds, is it advisable to build this? Perhaps with the longer port that he suggests to tailor room response?

[JonMarsh]

Martin King's TQWT is an interesting design; it's somewhat unfortunate that he's gone so "closed up" of late and not distributing his MathCAD docs any more.

The build suggestion described in post 185 is a good design and idea, notice that dropping the tuning to 28-30 Hz produces the same sort of slow roll off as the recommended reflex design with the same Fb. No surprise there.

Damping this tall narrow enclosure on the higher order modes is important; my only reservation about the TQWT, which I've never had time to investigate, is the midrange output of the port as designed and arranged. It may not be an issue, but I don't really know. For the conventional reflex, in a more standard shape (deeper, less tall), a 3" port gives good results as regards port velocity and midrange output (or lack of it). For two ways, this is more critical than a three way with a low crossover point to midrange.

[Paul K.]

Here's some info on an ML-TL I modeled, but didn't build, that can be use for either a Natalie P or a Dr. K MTM. This is from a thread on the PE forum in June this year about the Dr. K MTM.
--------------------------------------------------------------------------------

Since Ed showed the response of his take on the Dr. K's, I thought it would be useful to show the response of what I proposed. Using the cabinet with the same internal dimensions as for the compound tapered TL I posted about above (7.5"W x 14"D x 42"H), with the drivers located as previously, with the mass-loading port's center located 2" from the internal bottom of the cabinet, with the port having a diameter of 3" and a length of 3.25", and with 16 ounces of stuffing uniformly distributed by density (0.75 lb./cu.ft.) in the top 22" of the cabinet, the system response will be as shown in the attachment.
Paul

Over at "some other forum", I read through the Thor redesigns, mostly work done by Scott Moose.

As well, he poked his head in here at HTGuide, and posted a few times on the Nat-P thread in the early stages, with a suggestion for a straight no-taper mass-loaded transmission line

https://www.htguide.com/forum/showpost.php?p=238306&postcount=176

https://www.htguide.com/forum/showpost.php?p=238431&postcount=180

https://www.htguide.com/forum/showpost.php?p=238657&postcount=185

I'm contemplating this as the cabinet for a Nat-P build. However, if anyone out there has bothered with a MLTL, and can compare to the usual Nat-P builds, is it advisable to build this? Perhaps with the longer port that he suggests to tailor room response?

[crazyjpeters]

Jon, since you've chimed in to my humble thread, is it worth risking the potential midrange loss on a ML-TL, or would you stick with the tried and true (I'm still leaning towards a 50L-ish floorstander).

The room is 12'x30' with a low ceiling, and listening position is not optimal, unless I do some renovation. The room load would probably prop up the regular ported box, no?

[crazyjpeters]

Were I to go and do the huge enclosure as suggested by Scott (77L before bracing - maybe 75L after, maybe less), and tune the port length, would this be such a bad reflex box, even ignoring the possibility of it being ML-TL?

Modelling in WinISD, I tried the following variations, using a 75L with 3" x 4.75" port, and a 60L with a 3" x 5" port.

The large box looks slightly more droopy, but is this significant?

Any way to correct for potential midrange weakness after the fact? as in more stuffing? I think they recommended a "greasy wool" product...

[Jed]

The build suggestion described in post 185 is a good design and idea, notice that dropping the tuning to 28-30 Hz produces the same sort of slow roll off as the recommended reflex design with the same Fb. No surprise there.

Do you imply there is no real benefit to the transmission line in terms of bass extension?

A lot of folks think there is magic there, but I see what you are saying. It would be interesting to A/B a speaker in a TL versus a reflex design with the same tuning.

I bet there would be next to no difference but I could be wrong.

[cjd]

Do you imply there is no real benefit to the transmission line in terms of bass extension?

There is NO benefit in terms of bass extension. None.

The way Jon does many of his bass reflex alignments they fall into the quarter-wave tuned pipe camp anyhow... though that's not the same as a tapered quarter-wave. As you push box volume up and stop trying to hit a target volume, absolutely - note that just because you use MKing's worksheets doesn't mean you don't end up with a standard ported setup with a bump in the low end and... none of the "magic"

There may be a subjective or perceived difference in the sound of the bass when done correctly with a tapered pipe.

C

[ThomasW]

I bet there would be next to no difference but I could be wrong.

+1

In the mid 1970's when TLs were all the rage Jon and I built them by the dozen (or so it seemed). One of our more infamous designs used a 10 DVC driver from CTS. The massively braced box weighed a ton, it would take the full output from a Phase Linear 700 and bring the amp to it's knees. Sure was loud though..... 8O

Nobody gets low bass from a pair of 6.5" drivers regardless of the alignment. So why bother with a TL when it takes a sub to do the job correctly....

[Dennis H]

As well, he poked his head in here at HTGuide, and posted a few times on the Nat-P thread in the early stages, with a suggestion for a straight no-taper mass-loaded transmission line

To the rest of us, a straight, no-taper, mass-loaded, transmission line, with a round port, as Scott proposed, is just a reflex box with some stuffing. As I recall from that thread, there wasn't a lot of difference between Scott's sim in Mathcad and one I did in WinISD using the same box volume and port size, decreasing Qa to account for the stuffing.

[crazyjpeters]

Well, I'm convinced enough to not bother trying a TL, as there have been multiple successful builds of floorstander bass-reflex designs to have a comfort zone with them.

There look to be several builds of floorstander NatPs. Can anyone suggest the optimum, with a 3" Precision Port? I've seen 50L, 60L and more? I'll eventually be adding a sub, but I can't say when. Is it recommended to modify it to sealed when using a sub?

[Paul K.]

Hmmm...

In case you might be interested, I've attached a couple of graphs showing the response of the same driver in a tapered TL and an ML-TL. I did this modeling several years ago to satisfy my own curiosity. These two lines are eqivalent and, IMO, illustrate that an ML-TL is just as much of a TL as a tapered TL when the ML-TL is optimally designed. While the responses from these two are not absolutely identical, I really doubt anyone would be able to hear any differences. Thus, if the tapered TL is automatically accepted as being a "true" TL, why would one not say the same of the ML-TL? I think it's a bit prejudicial and short-sighted to arbitrarily dismiss a specific type of design. Of course everyone is entitled to their opinion. [I apologize for any lack of "fidelity" in the attachment; it's several years old and I wasn't using some really good software that I have now.]

To the rest of us, a straight, no-taper, mass-loaded, transmission line, with a round port, as Scott proposed, is just a reflex box with some stuffing. As I recall from that thread, there wasn't a lot of difference between Scott's sim in Mathcad and one I did in WinISD using the same box volume and port size, decreasing Qa to account for the stuffing.

[cjd]

I think that the modeling tools from MKing simply put a lot more data at our fingertips and were better able to get a handle on some of the more esoteric differences that things like how WHERE you place your drivers along the length of a column of air with a vent in a specific spot might change the sound.

[Paul K.]

There is NO benefit in terms of bass extension. None.

The way Jon does many of his bass reflex alignments they fall into the quarter-wave tuned pipe camp anyhow... though that's not the same as a tapered quarter-wave. As you push box volume up and stop trying to hit a target volume, absolutely - note that just because you use MKing's worksheets doesn't mean you don't end up with a standard ported setup with a bump in the low end and... none of the "magic"

There may be a subjective or perceived difference in the sound of the bass when done correctly with a tapered pipe.

C

Based on the two very similar responses I posted for an ML-TL and a tapered TL for the same driver, I suggest the "magic" is just as achievable in a correctly done ML-TL as it is in a "correctly" done tapered pipe. I also suggest there will be no audible differences between the two.