I am looking at a TL for a woofer with Qts 0.48 because I want a gentle roll off and a TL is supposed to give a response similar to an infinite baffle. I'd like to know if this is reasonable thinking.
The specs are:
Fs 39
Re 6.1
Qms 6.3
Vas 240 l
BL 14.6
Xmax 4.8mm
Sd 873cm^2
The spreadsheet from MJKs site gives a line of 43Hz which seems odd. Is this driver really suited to a TL?
Further, how would it compare with a closed box as far as power handling and also size of box for a similar cut off and transient response?
The specs are:
Fs 39
Re 6.1
Qms 6.3
Vas 240 l
BL 14.6
Xmax 4.8mm
Sd 873cm^2
The spreadsheet from MJKs site gives a line of 43Hz which seems odd. Is this driver really suited to a TL?
Further, how would it compare with a closed box as far as power handling and also size of box for a similar cut off and transient response?
Workers for me!
All point source drivers are suitable for TL loading over some portion of its BW, but the higher its Qts, the wider its maximally flat BW, so for < 0.5 Qts drivers the TL will be over-damped if tuned to Fs, so just like in a sealed alignment it must be tuned higher for most accurate reproduction at the expense of LF gain BW. Anyway, its real Qts is probably a bit higher, but even if it's not, tuning to Fs is plenty close enough considering our poor LF hearing acuity. If you want a maximally flat alignment combined with a room friendly roll off if it has a decent gain BW, then tuning to ~81.25 Hz is preferred. Regardless, you can find a close enough tuning between these two extremes to achieve a decent balance between tuning/F3/system Q using MJK's software.
Power handling, more for TL due to greater damping. TL is smaller due to the stuffing's thermal properties that makes the driver 'feel' like it's in an acoustically larger space.
Hmm, comparing my SS to the one on MJK's website, it's acoustically the same for a simple TL which tunes it to a 1/4 WL of the driver's 39 Hz Fs, so I assume you used one of the tapered alignments and since it's tuned somewhat higher it's a < 1/1 taper (TQWT) which in turn yields a 'faster' roll off slope, so like any 'dumb' tool, it's only as accurate as you.
GM
Yes, I think this is where it is for me. I want these (they are mains) to go low enough but I want to use multiple subs with this design, so, I need to choose an appropriate turnover frequency.
I found one of Augspurger's original tapered alignments for Qts=0.46, where Vp is half of Vas, fp is double fs, and f3 is just less than fp.
This box size would suit me, and I'm interested in good room integration but would f3=63Hz give me enough room to implement multiple subs effectively? I was thinking that a little closer to 100Hz would be more useful considering the tradeoff.... room modes starting at 200Hz against voice intelligibility down to 100Hz?
Interesting! Rick's alignments are based on GA's work, but Vp is closer to 1.5x Vas, so seems like the (mid) bass line would be pretty 'thin' once damped. Not necessarily bad, just that some form of EQ will probably be required to tonally balance them, reducing their effective efficiency.
Can't directly compare Rick's with MJK's except beginning at 70 Hz and both calc very large pipes with MJK's being a bit larger. It's interesting that Rick's is much shorter/fatter than MJK's. with acoustically small pipes you'll just have to see what's what via simming. At net Vb = 50% Vas, a ~30 Hz BR tuning, then damping it to make it ~aperiodic seems a viable alternative with an F3/Fb = ~67/52 Hz, so something to compare with.
Well, it depends on the room, but THX Ultra reference specs a 42 Hz F3 IIRC for the mains, so considering you normally want at least an octave of ~flat overlapping BW for a 2nd order XO you can't go wrong with it unless your room is so big and the subs are acoustically too far apart to sum well above this point. For typical size HTs though, a ~80 Hz F6 often suffices and why little high tuned satellites are popular.
BTW, for my records, what make/model driver is this?
GM
Can't directly compare Rick's with MJK's except beginning at 70 Hz and both calc very large pipes with MJK's being a bit larger. It's interesting that Rick's is much shorter/fatter than MJK's. with acoustically small pipes you'll just have to see what's what via simming. At net Vb = 50% Vas, a ~30 Hz BR tuning, then damping it to make it ~aperiodic seems a viable alternative with an F3/Fb = ~67/52 Hz, so something to compare with.
Well, it depends on the room, but THX Ultra reference specs a 42 Hz F3 IIRC for the mains, so considering you normally want at least an octave of ~flat overlapping BW for a 2nd order XO you can't go wrong with it unless your room is so big and the subs are acoustically too far apart to sum well above this point. For typical size HTs though, a ~80 Hz F6 often suffices and why little high tuned satellites are popular.
BTW, for my records, what make/model driver is this?
GM
Eminence ^15LFA
Umm, how do I put this.... firstly (as I'm sure you know), I'd like the multiple subs to excite room modes as high as practical (or as necessary). Secondly, I'd like the Delta's to cross naturally without an external filter (if at all possible), and thirdly, isn't the THX spec that allows the small satellites just, umm, convenient?
Or, to be frank... I've never had to place a crossover for a multiple sub setup and I don't even know whether I'm using the right driver. I'd just like to box it so it's smooth, flat, has good transient response and rolls off at a good frequency.
Ah! Delta series.
OK, then I'm guessing whatever the room's highest fundamental's 3rd harmonic is about as high as audibly worth it, but practically, I'm thinking that all that homogenization would make the below ~300 Hz BW (assuming a ~8 ft ceiling height) would sound like mush, but never having used multiple subs above an 80 Hz 2nd order XO to smooth out room modes............ Even at 80 Hz I had to use a sub positioned up on the wall.
Convenient? No, just practical to have multiple 'reference' specs depending on room size, SPL requirements. Relatively few folks want/can tolerate for whatever reason, cinema reference levels and even if you do/can, they do just fine with the recommended 4th order XOs if the LFE system is sized up accordingly which with multiple subs makes it easy plus you can 'kill two birds with one stone' by smoothing out the room to boot.
Not surprisingly of course, manufacturers capitalize as much as practical on the consumer's ignorance and desire for small/inexpensive (if not downright cheap), so they've given sub/sat systems a really bad rep, but properly done in a modest size room can sound as good as a 'full tilt boogie' THX reference system. In larger rooms though, the sats or 'full-range' mains need to be both HE and with good directivity control like what's required in any large venue.
Hmm, I assume you mean no hi-pass on the mains as opposed to no XO at all since the latter requires the subs be band-pass (BP) alignments. OK, then if TL, AFAIK there's only one max flat alignment for this driver for a given amount of series resistance (Rs) that might go low enough, so assuming virtually zero Rs, it's Rick's ~81.25 Hz Alpha TL alignment. Note that due to its large driver, net Vb that depending on how you configure it could make the driver/floor distance probably too high for some folks plus different layouts sim differently, though down in the < 250 Hz BW our hearing acuity is poor enough that I doubt there's any audible difference.
If the goal is to get ~flat to 42 Hz in a TL, then you definitely don't have the right driver as it will require a 0.9286 Qts for a 39 Hz Fs (Fp = Fs/Qts) which will increase net Vb ~60%!
Again, to get net Vb down to achieve a similar performance with driver will require my ~aperiodic suggestion. That, or go dipole and either use mass quantities of EQ to effectively lower its mass corner or run the sub system up to a ~160 Hz low pass or some combination of the two to find an acceptable mean.
GM
OK, then I'm guessing whatever the room's highest fundamental's 3rd harmonic is about as high as audibly worth it, but practically, I'm thinking that all that homogenization would make the below ~300 Hz BW (assuming a ~8 ft ceiling height) would sound like mush, but never having used multiple subs above an 80 Hz 2nd order XO to smooth out room modes............ Even at 80 Hz I had to use a sub positioned up on the wall.
Convenient? No, just practical to have multiple 'reference' specs depending on room size, SPL requirements. Relatively few folks want/can tolerate for whatever reason, cinema reference levels and even if you do/can, they do just fine with the recommended 4th order XOs if the LFE system is sized up accordingly which with multiple subs makes it easy plus you can 'kill two birds with one stone' by smoothing out the room to boot.
Not surprisingly of course, manufacturers capitalize as much as practical on the consumer's ignorance and desire for small/inexpensive (if not downright cheap), so they've given sub/sat systems a really bad rep, but properly done in a modest size room can sound as good as a 'full tilt boogie' THX reference system. In larger rooms though, the sats or 'full-range' mains need to be both HE and with good directivity control like what's required in any large venue.
Hmm, I assume you mean no hi-pass on the mains as opposed to no XO at all since the latter requires the subs be band-pass (BP) alignments. OK, then if TL, AFAIK there's only one max flat alignment for this driver for a given amount of series resistance (Rs) that might go low enough, so assuming virtually zero Rs, it's Rick's ~81.25 Hz Alpha TL alignment. Note that due to its large driver, net Vb that depending on how you configure it could make the driver/floor distance probably too high for some folks plus different layouts sim differently, though down in the < 250 Hz BW our hearing acuity is poor enough that I doubt there's any audible difference.
If the goal is to get ~flat to 42 Hz in a TL, then you definitely don't have the right driver as it will require a 0.9286 Qts for a 39 Hz Fs (Fp = Fs/Qts) which will increase net Vb ~60%!
Again, to get net Vb down to achieve a similar performance with driver will require my ~aperiodic suggestion. That, or go dipole and either use mass quantities of EQ to effectively lower its mass corner or run the sub system up to a ~160 Hz low pass or some combination of the two to find an acceptable mean.
GM
OK, I didn't realise that there may be too much of a good thing here.
You needed to chase the modes up the wall?
I was just planning to put them all on the floor against the walls....one between the mains and the others staggered with one either side of me.I'm thinking of three tapped horns, for what it's worth. Small ones would be convenient.
...is a little larger than I'd like
Do you mean this BR with the port stuffed?
_or_
I have some 'H' frames that I could use...I even like the idea, except...
...I planned to put these into corners and control the directivity. I don't know that I can get dipoles to work that way....
and, the dipole way of avoiding modes crossed over to the multiple sub way of joining with the modes seems a little weird. What do you think?
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In some cases there isn't, just a point of diminishing returns and why multiple subs are a good plan. higher up though where our hearing acuity is improving we need better definition to place the note in space and time referenced to adjacent notes and why monopole speakers replaced dipole for HT surrounds with the advent of DD as the preferred system.
Then again, if you want to be immersed in a sound-field similar to what you get in an acoustically large space such as a symphony hall, then go for it, but add multiple mains also to get the desired perceived Rt60 reverberant field. Never tried it with a movie soundtrack, but in trying to visualize it through a quadraphonic (four corner loaded) 901 system to achieve it is more than I can imagine/bear to contemplate. Increasing perceived space is much better implemented in the digital domain when working with multiple discreet channels.
Not exactly. When I built my first 'sub' in '70 it became quickly obvious that where it was located WRT the ~full-range horn mains had a huge impact on perceived overall performance and that none of them sounded all that great beyond the rumbling 'thrill' factor, so after a quick self course in room acoustics where I learned that they have the same main resonant modes as an open duct, I built two more (one much smaller to keep its mounting weight semi-manageable), hence the need for one up on the wall to help with the mid-bass floor/ceiling modes. I haven't read Dr. Geddes's book, but IIRC he recommended doing it in a thread.
Unfortunately, when I scaled back my life-style to retire fairly early, the only houses within budget meant a very lossy one and any sub I've tried that worked well enough also shook the house too much and due to a variety of reasons I've never been able to justify beefing up the room enough to work well or been able to consider a better built domicle until this recent housing market collapse, so 'hope springs eternal' once again........
OK, folks have found that TH's HF 'hash' (similar in performance to what you propose) dictates a XO point in the 40-60 Hz BW depending on room modes, so maybe better to build the TH's first to find how low the mains must go to blend well. That, or just assume the 42 Hz THX standard, rendering using Rick's TL alignment moot.
Right, the BR's vent will be long by default, so will need damping regardless for best performance, so might as well increase its stuffing density to get a critically damped response.
Never played all that much with dipoles as mains since the low fs drivers available had very limited linear excursion, but same as a box speaker can be reduced in net Vb due to corner loading, it seems reasonable to me that the same applies to a dipole's baffle width for the same baffle height as it gets closer to the apex. Only one way to know for sure and won't cost much to find out, so let us know..........
In a corner, a speaker's modes are so dominated by the room's in a corner placement that it will be mostly monopole in reality. Indeed, if the side gaps get too narrow, then they will act as lossy vents, so it seems reasonable to me to mount a driver on the narrowest practical baffle to find the right balance of baffle height Vs gaps.
An H frame will create horn 'vents', so experimenting with a gapped top plate seems another loading option. Taking this to its extreme, i.e. the side panels folded back to both create a slot to load the corner and extend the horn's initial expansion and the top closed off to seal it, it becomes a '50s era small Klipsch, EV corner horn.
GM
Then again, if you want to be immersed in a sound-field similar to what you get in an acoustically large space such as a symphony hall, then go for it, but add multiple mains also to get the desired perceived Rt60 reverberant field. Never tried it with a movie soundtrack, but in trying to visualize it through a quadraphonic (four corner loaded) 901 system to achieve it is more than I can imagine/bear to contemplate. Increasing perceived space is much better implemented in the digital domain when working with multiple discreet channels.
Not exactly. When I built my first 'sub' in '70 it became quickly obvious that where it was located WRT the ~full-range horn mains had a huge impact on perceived overall performance and that none of them sounded all that great beyond the rumbling 'thrill' factor, so after a quick self course in room acoustics where I learned that they have the same main resonant modes as an open duct, I built two more (one much smaller to keep its mounting weight semi-manageable), hence the need for one up on the wall to help with the mid-bass floor/ceiling modes. I haven't read Dr. Geddes's book, but IIRC he recommended doing it in a thread.
Unfortunately, when I scaled back my life-style to retire fairly early, the only houses within budget meant a very lossy one and any sub I've tried that worked well enough also shook the house too much and due to a variety of reasons I've never been able to justify beefing up the room enough to work well or been able to consider a better built domicle until this recent housing market collapse, so 'hope springs eternal' once again........
OK, folks have found that TH's HF 'hash' (similar in performance to what you propose) dictates a XO point in the 40-60 Hz BW depending on room modes, so maybe better to build the TH's first to find how low the mains must go to blend well. That, or just assume the 42 Hz THX standard, rendering using Rick's TL alignment moot.
Right, the BR's vent will be long by default, so will need damping regardless for best performance, so might as well increase its stuffing density to get a critically damped response.
Never played all that much with dipoles as mains since the low fs drivers available had very limited linear excursion, but same as a box speaker can be reduced in net Vb due to corner loading, it seems reasonable to me that the same applies to a dipole's baffle width for the same baffle height as it gets closer to the apex. Only one way to know for sure and won't cost much to find out, so let us know..........
In a corner, a speaker's modes are so dominated by the room's in a corner placement that it will be mostly monopole in reality. Indeed, if the side gaps get too narrow, then they will act as lossy vents, so it seems reasonable to me to mount a driver on the narrowest practical baffle to find the right balance of baffle height Vs gaps.
An H frame will create horn 'vents', so experimenting with a gapped top plate seems another loading option. Taking this to its extreme, i.e. the side panels folded back to both create a slot to load the corner and extend the horn's initial expansion and the top closed off to seal it, it becomes a '50s era small Klipsch, EV corner horn.
GM
I simmed a 93 litre (3.28'^3) closed box. By adding a port (not aperiodically damped) tuned to 30Hz, the result is within 2dB higher than the closed box all the way down to 40Hz.
I assume that damping would knock this 2dB off (and maybe a little more).
The closed Qtc for this sized box would be about 0.9
What differences would you expect to hear from the closed versus the aperiodic?
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~Aperiodic effectively lowers the driver's Qts, Qb, so is much better damped Vs a 0.9 Qtc sealed alignment, ergo will have a more accurate decay up to the limits of the amp's slew rate which governs the system's ultimate transient response. Down low though where our hearing acuity sucks, it may not be all that obvious with such a low tuning unless room effects combines to exacerbate it and why all my personal HIFI/HT designs are critically to over-damped to mimic a compression horn's high DF (< 0.5 Qp).
GM
GM
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