smithie said:HI
I GOT THIS RESPONSE FROM FALCON CONCERNING A INDUCTOR VALVE FOR MY PLAN REGARDING THE 8LTR JX92 ENCLOSURE MATED TO THE JX125 BASS ENCLOSURE..
I am afraid that it is not possible to devise a satisfactory passive crossover for such a low frequency. The only way is to use active such as the Basset.
The values would be so large that the resistance would be far too high and the impedance of the bass units is varying - it is close to the resonances of the existing and the new bass units - that you are trying to design into a fast varying impedance which is not really possible.
M. Jones
Falcon
I DONT REALLY UNDERSTAND WHATS BEING SAID HERE OTHER THEN I HAVE TO GO ACTIVE OR ELSE THIS PLAN,IM STUFFED
AINT NOTHING EVER EASY...
SMITHIE
It only means he can't do it. The JX125 really are very good bass units and produces well controlled bass. It's possible to go very low on those where you actually "feel" the bass. The large Organs really are astonishing when played though the JX125.
hi
i was thinking that,moreso after what collin said but i also got this response from ipl who i asked the same question to....
At 80htz the inductor would be impossibly high ,The only way to do this job properly is with an active subwoofer which can be fully adjusted to your system
Kind regards ivan leslie.
everyone seems to keep telling me active...i know thats a option but iwas hoping to keep it more simple then that if i could!
as anyone had dealings,solutions and input with what im trying to do...ie can it be done,or is active the only real way!
rember in the 80s when i started out in the car hifi world i use to run my subs at 80hz with a inductor(oh i wish i had kept them) and filters(passive) on the front speakers,of course that was the days before active i guess!.....(ignorance is bliss)
smithie
i was thinking that,moreso after what collin said but i also got this response from ipl who i asked the same question to....
At 80htz the inductor would be impossibly high ,The only way to do this job properly is with an active subwoofer which can be fully adjusted to your system
Kind regards ivan leslie.
everyone seems to keep telling me active...i know thats a option but iwas hoping to keep it more simple then that if i could!
as anyone had dealings,solutions and input with what im trying to do...ie can it be done,or is active the only real way!
rember in the 80s when i started out in the car hifi world i use to run my subs at 80hz with a inductor(oh i wish i had kept them) and filters(passive) on the front speakers,of course that was the days before active i guess!.....(ignorance is bliss)
smithie
You don't have to go full active. That is, you can let the mid/full unit roll off naturally. In other words let it fall where it may. Then blend an active sub into it. That's what the common plate sub amps are designed for. The better ones will have adjustable crossover points and sometimes slopes. You can measure both and do the set up, or just do it by ear. There are various somewhat systematic methods for doing the ear method that you can find on the web.
This doesn't prevent you from going full active later if you want to have more latitude with slopes and crossover points and want to get more into measuring, etc..
Sheldon
This doesn't prevent you from going full active later if you want to have more latitude with slopes and crossover points and want to get more into measuring, etc..
Sheldon
Large inductors or large caps. Yes. The inductors get as large as 10mH, pretty big when you have large guage wiring. Large caps up of over 400uF are still within reason. But you do loose some efficiency. Two good woofers that go low and connected well with the 92 is better than one active sub for realistic music listening. It takes a significantly more work and knowledge.
Of course, active is a no brainer, just buy, plug in, listen, adjust. Also works quite well.
So actually active looks complicated but is simpler. Passive looks simple but more complicated to get optimum results.
Of course, active is a no brainer, just buy, plug in, listen, adjust. Also works quite well.
So actually active looks complicated but is simpler. Passive looks simple but more complicated to get optimum results.
The thing that puts me off going active is having to source the crossover/filter - initially for the bass.
Any recommendations for straightforward active crossover kits which would be a good fit for BrianGT's gainclone?
(I admit it, I've also got a couple of JX125s I'm itching to use with a sat arrangement.)
Colin
Any recommendations for straightforward active crossover kits which would be a good fit for BrianGT's gainclone?
(I admit it, I've also got a couple of JX125s I'm itching to use with a sat arrangement.)
Colin
I've read good things about the Marchand kits. They have a wide range, from simple inexpensive op-amp based stuff, up to tubed active. Plus, you can get the stuff anywhere from circuit board only, to kit with parts, to fully assembled.
http://www.marchandelec.com/
http://www.marchandelec.com/
Dumbass said:
I sold my Marchand because it wasn't transparent enough. I have been noodling about an XO / PCB that would be aimed at adding to a chip-amp to turn it into a woofer amp. I want something fairly versatile -- maybe i should post my manifesto and get some help?
I want to be able to achieve very good transparency, can't have it getting in the way of a good full-range so have some very specific ideas....
dave
hi
i realise this question might ruin any chance of credability i may have (haha lets be hornest ive never had any anyway)
but what about in car power amps(not the really cheap stuff) they havr good power figures,massive if you look at the class d designs but more to the point some have very versitile xovers(variable along with the slopes,plus varible gains etc) and there all built into a nice enclosure,all they would need is a 12-14.5 voltage with decent current.
well whats your views...or have i sniffed alittle to much resin W?
all the best
smithie
i realise this question might ruin any chance of credability i may have (haha lets be hornest ive never had any anyway)
but what about in car power amps(not the really cheap stuff) they havr good power figures,massive if you look at the class d designs but more to the point some have very versitile xovers(variable along with the slopes,plus varible gains etc) and there all built into a nice enclosure,all they would need is a 12-14.5 voltage with decent current.
well whats your views...or have i sniffed alittle to much resin W?
all the best
smithie
ps
forgot to mention that i tried my pioneer 400 solid state on the vtls i built and i can rule my valve amps out as the problem im experiencing with them as its still alive and kicking with the pioneer!
ive just dug out my incar precisionpower 31 band octave equaliser so if i get a quite period over the w,end then i might hook it into the system,that way i should know exactly where the trouble frq is...i know i should get out more...but it bugs me,moreso when it seems that im the onlyone suffering with this problem from this design!
smithie
forgot to mention that i tried my pioneer 400 solid state on the vtls i built and i can rule my valve amps out as the problem im experiencing with them as its still alive and kicking with the pioneer!
ive just dug out my incar precisionpower 31 band octave equaliser so if i get a quite period over the w,end then i might hook it into the system,that way i should know exactly where the trouble frq is...i know i should get out more...but it bugs me,moreso when it seems that im the onlyone suffering with this problem from this design!
smithie
I wonder if passive line-level xover might be the way to go for you. Or simply no high-pass on the full-ranger, just low-pass on the woofer. (Full-ranger in damped alignment like sealed or open baffle will have limited excursion in lower freqs.)planet10 said:
Which Marchand kit did you use? (And what kind of PS did you have for it?)
I also wonder if battery PS might have improved things. Also, perhaps opamp rolling.
Anzwaz . . .
Dumbass said:
The PLLXO fits into my XO manifesto, but 1st order XOs don't totally cut it for some of the aps i want. 1 of the intended uses for the XO is as you have described, so the active bit would be just on the woofer. A stage more complex would add a PLLXO (preferrably in the form of replacing an existing coupling cap(s) with something smaller. But a full active XO is also sometimes desired and for this purpose i'd like to be able to subtract the low-pass from the FR to derive a high pass.
XM9 (with opamp upgrades) with the deluxe (still just basic) power supply
My felling is that PS is critically important for op-amps despite their typically high PSRR. To that end the board for the fantasy XO would be set up so that if you wanted a separate reg could be put on every op-amp. I have bits already to try 3 levels of regs (7815/7915, 317/337. & LM338). I also have a Vacuum State Low Voltage SuperReg coming (my guess is that this will be best). I also have some small power-amp size trafos to use.
dave
planet10 said:
PLLXO need not be only 1st order. If i remember right some company called Fmod used to make PLLXOs for car audio use and claimed a slope of 12db/oct. the PLLXOs fit inside a small RCA connector (female-male).
Hi Smithie
I've just found the details of the old JX92 (non-S model). This was in production from the mid-90s to around 2000. There are a few differences such as Vas and Qts - I wonder if that would alter how it performs in a VTL designed for the S model? Current JX92S specs are here
Brief specs of the 92 are
mechanical Q - 1.42
electrical Q - 0.63
total Q - 0.44
mechanical resistance - 1.43
force factor - 4.06
dc resistance - 5.10
dynamic mass - 7.22
system compliance - 17.32
equiv air vol - 12.18L
SPL - 86.5
min box vol - 4L (IB)
max box vol - 12L (IB)
I've just found the details of the old JX92 (non-S model). This was in production from the mid-90s to around 2000. There are a few differences such as Vas and Qts - I wonder if that would alter how it performs in a VTL designed for the S model? Current JX92S specs are here
Brief specs of the 92 are
mechanical Q - 1.42
electrical Q - 0.63
total Q - 0.44
mechanical resistance - 1.43
force factor - 4.06
dc resistance - 5.10
dynamic mass - 7.22
system compliance - 17.32
equiv air vol - 12.18L
SPL - 86.5
min box vol - 4L (IB)
max box vol - 12L (IB)
Just a few thoughts. I deliverately haven't looked at the plans available on the Jordan site, but this is the best practical response I can get from the JX92S in MathCad after playing adround for 5 minutes or so. It's a straight, mass-loaded quarter-wave tube:
Length: 45".
So & SM = 4.5Sd
Port: 3"x4" (WxD) 4" from the base on the front panel.
Driver centre at 33.75" from the base (11.25" from the top).
0.5lbs ft^3 of stuffing. You can reduce this to 0.25lbs ft^3 at the price of fractionally increasing the ripple.
You won't need any series resistance here, though a BSC circuit will be needed. Approximate values would be a 3mH inductor and 3-4ohm resistor. I wouldn't bother with a zobel in this case.
Best
Scott
Length: 45".
So & SM = 4.5Sd
Port: 3"x4" (WxD) 4" from the base on the front panel.
Driver centre at 33.75" from the base (11.25" from the top).
0.5lbs ft^3 of stuffing. You can reduce this to 0.25lbs ft^3 at the price of fractionally increasing the ripple.
You won't need any series resistance here, though a BSC circuit will be needed. Approximate values would be a 3mH inductor and 3-4ohm resistor. I wouldn't bother with a zobel in this case.
Best
Scott
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Hi Scottmoose
I haven't seen GM's graphs for his MLTL designs but the 48 inch long version gives good output to the low 30s. The specs are here.
GM sets the drivers a little farther down the pipe than in your example - the 31" version has it about 11" down. I presume this all to do with damping the harmonics. I'd lbe very intersted to see graphs of his two designs.
I haven't seen GM's graphs for his MLTL designs but the 48 inch long version gives good output to the low 30s. The specs are here.
GM sets the drivers a little farther down the pipe than in your example - the 31" version has it about 11" down. I presume this all to do with damping the harmonics. I'd lbe very intersted to see graphs of his two designs.
...and here's the anechoic plot for Greg's MLTL48, also in Martin's MathCad worksheets.
Both provide similar results to the one I made earlier, which I find comforting. We've taken a different approach however -Greg has gone for a narrower, shallower cabinet that's a whisker taller, with a fraction more stuffing, and a narrower, shorter port. I have gone for a slightly shorter cabinet, with much more internal volume, and a wider, longer port, following my usual approach as I'm always a little uneasy about narrow vents. Paranoia for the most part, but I always take the larger option as I don't pretend to have anything like Greg's practical and technical knowledge or experience -few people do, other than, say, Martin King, Terry Cain, and Bob Brines.
My cabinet appears to go very fractionally deeper, with a hint of a peak at cut-off, which was what I was aiming for, but there's little in it, so Greg's is by far the more economical design in terms of space taken up.
The MLTL31 looks to be the flattest of the lot. It gives little or nothing away to the others in extension either, though the stand it requires means there's little in it in terms of outright space taken up I suppose. Two superb designs then, but what would you expect, coming from the source?
Best
Scott
Both provide similar results to the one I made earlier, which I find comforting. We've taken a different approach however -Greg has gone for a narrower, shallower cabinet that's a whisker taller, with a fraction more stuffing, and a narrower, shorter port. I have gone for a slightly shorter cabinet, with much more internal volume, and a wider, longer port, following my usual approach as I'm always a little uneasy about narrow vents. Paranoia for the most part, but I always take the larger option as I don't pretend to have anything like Greg's practical and technical knowledge or experience -few people do, other than, say, Martin King, Terry Cain, and Bob Brines.
My cabinet appears to go very fractionally deeper, with a hint of a peak at cut-off, which was what I was aiming for, but there's little in it, so Greg's is by far the more economical design in terms of space taken up.
The MLTL31 looks to be the flattest of the lot. It gives little or nothing away to the others in extension either, though the stand it requires means there's little in it in terms of outright space taken up I suppose. Two superb designs then, but what would you expect, coming from the source?
Best
Scott
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