Is the
2240
e-155
- basket the same as in the 2245?
SO, if i recone a e-155 basket, then i get one real 2245 ?
Is the
2240
e-155
- basket the same as in the 2245?
SO, if i recone a e-155 basket, then i get one real 2245 ?
YES! C8R2245 => 2240 or E155 basket => 2245! Have fun!
Here's your nominal parameters:
Fs = 20 Hz
Qms = 2.2
Vas = 821.2 liters
Cms = 347.3 ĩm/N
Mms = 185 g
Rms = 10.42 mohms
Xmax = 9.5 mm
Xmech = 12.7 mm
P-Dia = 406.4 mm
Sd = 0.129 sq.m
P-Vd = 1230 cu.cm
Qes = 0.31
Re = 5.8 ohms
Le = 1.4 mH
Z = 8 ohms
BL = 21 Tm
Pe = 300 watts
Qts = 0.27
no = 2.1 %
1-W SPL = 95 dB
2.83-V SPL = 96.77 dB
Last edited by 4313B; 04-28-2003 at 07:24 AM.
now i know the house will fall apart!!
i may get my hans on two e-155 and one new 2245,
then i just need one more 2245 and i have one per corner.
i will try to simulate the 2245 in an closed box with two
passive radiators from stryke, 18" radiators....
holy mother
Why on earth would you want to turn a 2245H-based system into garbage by adding passive radiators? Passive radiators add additional capacitance, inductance and resistance compared with a port/duct. In addition, mutal coupling from the passive radiator is less than you would get from a close proximity port/duct! I could see using PR8's and PR10's with LE8's and LE10's in small enclosures but I can't see mucking up 2235H's or 2245H's with passive radiators.
Last edited by 4313B; 04-28-2003 at 09:28 AM.
OK Giskard, so i would not even think about it then!
It's good to think about such things. Oftentimes though, it's not much fun to go to all the trouble of building such things and then being disappointed.
Giskard: "Why on earth would you want to turn a 2245H-based system into garbage by adding passive radiators? Passive radiators add additional capacitance, inductance and resistance compared with a port/duct. In addition, mutal coupling from the passive radiator is less than you would get from a close proximity port/duct! I could see using PR8's and PR10's with LE8's and LE10's in small enclosures but I can't see mucking up 2235H's or 2245H's with passive radiators."
Please tell more about what problems to encounter if using two 18" passive radiators with one 2245 18"
in the simulations all things look nice
has anyone been testing this before?
"Please tell more about what problems to encounter if using two 18" passive radiators with one 2245 18""
Read about passive radiators on the Internet and in the AES journals. They DO have their uses. I personally wouldn't use them in a high performance VLF system.
"in the simulations all things look nice"
What simulations?
"has anyone been testing this before?"
Not a 2245H and PR's. I've done extensive testing with LE8/PR8, LE10/PR10, 128H/PR300, 124A/H & PR15C, 136A/H & PR15C, LE14A/H & PR15C, 2235H/PR15C.
You would do well to build a few test boxes and do some comparisons so you can get a feel for what's going on with PR versus vented systems. Unfortunately, with the 2245H, all your test boxes will need to be quite large. Sonotubes would be a nice alternative but you will need to have the PR and 2245H side by side to fairly compare them with a 2245H and close proximity port. You should be able to discern the superior mutual coupling at VLF with the port. The port should also sound "tighter", the PR should sound "fuller". Where the PR really shines, smoothing midband response, is irrelevant in a VLF application.
The thing is, Giskard, you're throwing out the baby with the bathwater a bit here...
All the JBL PR's you mentioned, without exception, are relatively HIGH resonance PRs... ie, their internal, out-of-box, resonances are 15 Hz and higher. OTOH, the Stryke PR he mentioned, once it's loaded with the appropriate weight, will have an Fp of 10 Hz or lower.
What does this do? It ELIMINATES, to pretty much any practical extent, the added compliance effects (ie, the capacitance) of the PR, as is concerned with the actual box tuning resonance (which should STILL be in the same range as a port, ie, probably 20-something Hz for a 2235). In short, the suspension of the Stryke is VERY compliant... to the extent, where it's contribution to the transfer function is pretty much swamped by other factors... it'll be so far out of the used bandwidth of the system, as to effect almost no change on group delay and such, as compared to a port.
I've done PR systems with Fp of 5Hz... and have used systems with PRs tuned to 5-10 Hz (such as the extremely capable EV Interface series speakers of the late '70s... which if you're looking for TIGHT bass, GOOD GRIEF they do that WELL!), and they actually have LOWER noise and distortion than a ported box (no port wind noise, and no power compression effects!), and allow a sometimes BETTER coupling with the air (ie, LARGE diaphragm area, requiring little excursion, and having a more matched acoustical impedence with the air itself, ie, LOWER LOSSES) than a port...
In short, it ain't what you got, it's how you use it...
Regards,
Gordon.
who is actually building a PR coupled 4th order bandpass box now, if that doesn't make your head spin like a top!
No, you misundestood what I said.
The PR ITSELF has an INTERNAL resonance of somewhere near 5 Hz, with the suspension and mass it has on board. However, the MASS and the DIAPHRAGM AREA of the PR, give a SYSTEM resonance (ie, the equivalent of port tuning) the SAME as a standard ported box (ie, the woofer will see a 20-something-Hz, whatever is appropriate, when the mass is adjusted to the right amount by weighting the PR cone). You can look at the impedence curve of the driver, and tune the PR to get nearly identical peaks, at identical frequencies, as a ported driver... which indicates that the system will function pretty much identically in transient response as a ported box.
The idea is to get the PR's OWN resonance far enough away from the system resonance, that it stops having much significant effect on the group delay or the overall effective transfer function, in any range the driver is putting out significant output levels... and that IS possible, with more modern, large-area, compliant, PR designs...
Basically, you can treat the PR as JUST a mass, with a bit of damping (and most PRs have VERY HIGH Qms, with their foam surrounds and very compliant suspensions) resistance... usually the resistance loss is low enough, to be lower than the other box losses in a box of 5-10 ft^3. Make the suspension as compliant as possible... which will put the PR Fp at the very low frequencies mentioned, and this will indeed be the effective case...
Regards,
Gordon.
"That's my problem and I probably shouldn't have posted to this thread."
Wrong!(sorry - you're the only one thus far to have employed this little demon
)
"G.T. and I went over PR's back in the early 80's and again in the early 90's"
That is precisely why your post is helpful, IMHO. I too have played around with the LE8/PR8 and LE10/PR10 and find the results interesting, but am not convinced that (for my ears...) PR's are superior over a ported cabinet for the VLF. Granted, a 2245H goes to depths not well reproduced (if at all...) by the LE8 or LE10, so my experience may not be that relevant...
Last edited by boputnam; 07-25-2003 at 02:54 PM.
bo
"Indeed, not!!"
Well, it may just be that some of us (myself specifically!) are just too hardheaded, and just have to learn about these things ourselves by doing them in person, to believe them.
I have liked the results of the extremely-compliant PRs I've seen used... for example, the Boston Acoustics PV1000 sub, is one example of a PR making a system work VERY well in the VLF (f3 of 22 Hz in a 1 ft^3 cube, and it can do 110 dB @ 1m down there!), without the "boingy" sound that oftentimes can accompany less-than-optimal PR systems (and believe me, Giskard, I've seen my share of BAD PR systems too... but I've seen just as many bad PORTED systems!). That Boston actually has REAL PITCH DEFINITION down low... which is a RARITY in speakers of ANY price, IME!!
It does seem, that one of the side effects of the more sophisticated computer modelling programs being available, is that it is now possible to "pound out" a lot of the areas where it's been hard to experiment with all the possible iterations... and I find that PRs are one of those areas. They definitely are one of those things, that unless they're done right, they can definitely come back and bite you on the @$$...
Regards,
Gordon.
"...the Boston Acoustics PV1000 sub, is one example of a PR making a system work VERY well in the VLF (f3 of 22 Hz in a 1 ft^3 cube, and it can do 110 dB @ 1m down there!)"
Really!
I am not particularly interested in debating whether a PR system is better than a vented system, but I thought Boston Acoustics was in the "good for the money" category. Pulling off f3 in the low 20s and putting out 110dB down there from a 1 cu ft box is tough. My little 11" Velodyne cube does it, but it cost $1500, and I wouldn't call it very musical. The Bob Carver Sunfire subs use passives in their small cubes as well, but I think they are a bit thick sounding.
I wouldn't even be that kind to the Carver/Sunfire sub. To me, just a bunch of random rumble.
OTOH, the Boston has the kind of well-damped, tight, tuneful bass that I can live with. No, it probably can't fill a room with SPL (mostly noise, tho) like the Sunfire... but it certainly does sound GOOD.
Of course, for $1200, it ain't no bargain basement subwoofer either. But with the engineering in it, there's not much that can beat it, in anywhere near that price range, IMHO...
I take the lazy mans approach; I read up on various audio applications, attempt to grasp the concepts/research/results and decide if I think it is correct, then I latch onto the emerging conclusion and discard the evidence leading up to it. (My brain only has so much room)
Soooooo, after reading about them, it was also my opinion that a PR is not a great solution, especially with a 2245H, where a solution is not needed. I don't see what is gained here, even if the PR is a good one. And the added cost, complexity, and potential for foul-ups seems to argue against it.
Lastly, and I tend to hate arguements like this one, but here goes anyway............why have the pro audio manufacturers who used to mess with PR's all abandoned their use? Don't say cost.
MBB
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