I'd use the word continuum - along which the factor(s) which predominate in the performance will vary in significance - not always with tidy defined borders.
only the broadest transitive sense that "all horns, MLTL, Voigt pipes, etc exhibit 1/4 wave resonant behavior, so anyone of them could be described as fitting in any of those categories" - in other words, not really
change the flair rate, and in this specific case, the choke, and yes it still might "work" - perhaps even quite well, but at the very least, it won't be a FH3and all I need to do is keep the CSA and length the same... hmmm, a little knowledge is a dangerous thing
as noted above, provided you're not surprised that it performs differently and call it something else, why not?
What GM said (both posts).
FH3 is a horn, since anything with positive expansion possess 1/2 wave characteristics (to a varying extent), and is therefore a horn. Incidentally -if you kept both the length & CSA of FH3 the same, you would end up with FH3, since you haven't scaled anything...
Assuming that the entire box volume is used, then it would be an MLTL. The Arro only uses the upper part of the enclosure; like a lot of modern floorstanding speakers, there is a large cavity in the lower portion of the cabinet which can be (needs to be) filled with suitably dry sand, lead shot, antibacterial cat-litter etc. It's essentially a standmount speaker with built-in stands. A bass reflex cabinet assumes there are no standing waves / eigenmodes / call them what you will in the enclosure, and the air-particle density to be ~uniform. A QW box (TL in this parlance) deliberately generates and uses standing waves.
A pensil is an MLTL; it's just a specific alignment thereof. You can add a 'big vent' to most any vented alignment assuming you design it properly.
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Thanks everyone, this is very helpful as well as very interesting. I am discovering that there's much more to know about speakers than I realized, the more you know, the more you realize you don't know. I'm afraid my mis-spent youth didn't leave me with any useful knowledge like GM !
From what you have all told me, it is the 'big vent' that complicates the scaling of an MLTL or BR box it's attached to, yet if I understand correctly, the 'big vent' is the feature that offers the potential for better bass and avoidance of BSC. Totem seems to have missed the boat
I shall give this further thought.
By the way, given that the BR and MLTL are both resonant designs, does one have an advantage over the other except for the different physical aspect ratio's. For some reason I thought the MLTL was better in terms of bass extension albeit with the tradeoff of having to design to avoid ripples in the FR. But perhaps these two approaches amount to the same result - do they not provide essentially the same performance regarding driver loading (and unloading), group delay and bass extension ? If not, why would you choose one over the other ?
From what you have all told me, it is the 'big vent' that complicates the scaling of an MLTL or BR box it's attached to, yet if I understand correctly, the 'big vent' is the feature that offers the potential for better bass and avoidance of BSC. Totem seems to have missed the boat
I shall give this further thought.
By the way, given that the BR and MLTL are both resonant designs, does one have an advantage over the other except for the different physical aspect ratio's. For some reason I thought the MLTL was better in terms of bass extension albeit with the tradeoff of having to design to avoid ripples in the FR. But perhaps these two approaches amount to the same result - do they not provide essentially the same performance regarding driver loading (and unloading), group delay and bass extension ? If not, why would you choose one over the other ?
You're welcome! You probably weren’t forced to stay in-doors near as much as me.
Correct.
Yes, the MLTL damps the driver better at Fb and over a wider BW. In a way, you could call the MLTL a BVR since the cab’s ¼ WL resonances are doing the same thing acoustically as the BVR’s larger, longer vents plus the MLTL’s vent damps its mids response much more and why it’s been my vented alignment of choice ever since I became aware of it. It’s still a 4th order system, so unloads, rolls off same as a BR of the same tuning.
All this assumes that they have the same net Vb, Fb, but the MLTL’s ability to handle a greater net Vb, which further increases damping and lowers Fb a bit more for a given vent length or shortens it for the same Fb is its real advantage IMO. If you size/tune the BR this way, you just wind up with excessive peaking at Fb that must be damped with stuffing unless it’s driven hard to keep it thermally compressed enough to ‘fill it up’ like is done in prosound apps and why when old Altec/JBL/EV/whatever BR cabs are used in the home, they are usually re-tuned/damped to keep from sounding ‘one note’ at low power.
GM
Correct.
Yes, the MLTL damps the driver better at Fb and over a wider BW. In a way, you could call the MLTL a BVR since the cab’s ¼ WL resonances are doing the same thing acoustically as the BVR’s larger, longer vents plus the MLTL’s vent damps its mids response much more and why it’s been my vented alignment of choice ever since I became aware of it. It’s still a 4th order system, so unloads, rolls off same as a BR of the same tuning.
All this assumes that they have the same net Vb, Fb, but the MLTL’s ability to handle a greater net Vb, which further increases damping and lowers Fb a bit more for a given vent length or shortens it for the same Fb is its real advantage IMO. If you size/tune the BR this way, you just wind up with excessive peaking at Fb that must be damped with stuffing unless it’s driven hard to keep it thermally compressed enough to ‘fill it up’ like is done in prosound apps and why when old Altec/JBL/EV/whatever BR cabs are used in the home, they are usually re-tuned/damped to keep from sounding ‘one note’ at low power.
GM
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I'll have to read this a couple of more times, but I believe what is being said is that the BVR offers similar benefits to the MLTL in terms of bass performance, but BR by itself is not technically as 'good'.
So if there was a choice to be made between the Pensil (MLTL) and Derwent (BVR) the basic performance is similar from the perspective of bass loading of the drivers but the BVR has the additional potential that it may couple to the room better. Adding a vent to the Pensil would allow it to couple to more air, but requires modeling/re-design.
However, if scaleability without re-design/modeling is important, the Pensil is the safer route.
Is there enough to be gained from learning how to design/scale the BVR rather than use the Pensil ? I guess nobody can answer that except me...
One thing I noticed about the Pensil - it has no internal partition. I'm more accustomed to seeing something that's got at least one fold, like Henkjan's TL. The Pensil seems almost 'too simple' ?
So if there was a choice to be made between the Pensil (MLTL) and Derwent (BVR) the basic performance is similar from the perspective of bass loading of the drivers but the BVR has the additional potential that it may couple to the room better. Adding a vent to the Pensil would allow it to couple to more air, but requires modeling/re-design.
However, if scaleability without re-design/modeling is important, the Pensil is the safer route.
Is there enough to be gained from learning how to design/scale the BVR rather than use the Pensil ? I guess nobody can answer that except me...
One thing I noticed about the Pensil - it has no internal partition. I'm more accustomed to seeing something that's got at least one fold, like Henkjan's TL. The Pensil seems almost 'too simple' ?
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Hmm, BVR [big vent reflex] means it should provide more bass, mid-bass performance than the MLTL, though with the caveat that it can’t provide as smooth a response. There’s nothing wrong with a BR alignment when properly implemented, but too often in consumer products it’s not, so has an undeservedly bad reputation.
??? If the Pensil is a MLTL, it already has a vent. If you mean converting it into a BVR and then scaled to a different range of driver specs would be more work than designing from scratch.
A MLTL is simple since it’s nothing more than a BR stretched out until it has sufficient ¼ WL action to damp the vent enough to require altering its specs to maintain a given tuning [Fb]. This doesn’t mean it has to be ¼ WL of Fb, only long enough to add damping to the vent, which will be up in the mid-bass for most apps, ergo why it creates a wider vent BW than the BR. In between these two acoustical loading points it’s still a BR.
Historically, the BVR alignment was required to offset as much as practical the shortcomings of the electronics and software of the tube era and what we define as baffle step compensation [BSC] now, so for me, the BVR need only be used for high output impedance apps or where the speaker will be well away from any wall/corners or when one wants to tune the cab over a wider than normal BW [DBR and its short horn variants].
GM
??? If the Pensil is a MLTL, it already has a vent. If you mean converting it into a BVR and then scaled to a different range of driver specs would be more work than designing from scratch.
A MLTL is simple since it’s nothing more than a BR stretched out until it has sufficient ¼ WL action to damp the vent enough to require altering its specs to maintain a given tuning [Fb]. This doesn’t mean it has to be ¼ WL of Fb, only long enough to add damping to the vent, which will be up in the mid-bass for most apps, ergo why it creates a wider vent BW than the BR. In between these two acoustical loading points it’s still a BR.
Historically, the BVR alignment was required to offset as much as practical the shortcomings of the electronics and software of the tube era and what we define as baffle step compensation [BSC] now, so for me, the BVR need only be used for high output impedance apps or where the speaker will be well away from any wall/corners or when one wants to tune the cab over a wider than normal BW [DBR and its short horn variants].
GM
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My thought with Pensil was whether there was an advantage in adding a 'big' vent to what is currently a 'little' vent in order to couple any LF output from that vent to the room for improved bass. Such an arrangement would, for me, look like an FH3 type system - but let me now confuse others by claiming such a thing whilst my knowledge is still rather small. In terms of scaling, for the most part, I'm only looking to make the box narrower - no change in driver.
I like this way of thinking about it.
Hmm, since the Pensil is already long enough to tune/damp its vent over a relatively wide BW, adding a large vent to the existing one would lower Fb, adding more gain BW at the expense of smoothness, but not sure if that's a good plan or not, especially WRT driver protection. Don't recall ever experimenting with, or even simming, one.
Then again, I guess the bottom vent couplers I've used like I spec'd for the original 'short' Jordan JX92S MLTL could be construed as one [the volume behind the sloped baffle should be filled with sterilized sand, Portland cement, Kitty Litter, Oil Dri or similar].
I've never built or even auditioned any, but folks say it makes smooth, solid bass with no need for BSC once properly toe'd in as Jordan recommends.
Scaling in what way? By reducing its net Vb or just changing its width x depth ratio to some golden or acoustic ratio?
GM
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Thanks GM for your inputs! If BAF results in WAF, it's ok
You're welcome! Hope it all turns out well.
GM
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