Speaking of loudspeaker, I understood their was a trade-off between : compactness of the enclosure, low cutoff frequency, and sensitivity. You can have two of those, but not three.
So I wonder, how can Klipsch makes something like that : https://www.klipsch.com/products/rp-400m-bookshelf-speaker
exterior (!) volume : 8.2Liters
low cut-off (3db) 52Hz
sensitivity : 93db @ 2.83V
I see no speaker on the shelf which can do a similar thing. (low VAS, low FS, high sensitivity)
How are they doing ?
My best hypothesis so far is that they dont, maybe the 93db is a maximum very far from 50hz (and the sensitivity is closer to 89db or something), maybe there's a bump at 55hz (and a hole deeper than -3db between 70hz~120hz).
But, are they doing it ? Can I do it too ?
So I wonder, how can Klipsch makes something like that : https://www.klipsch.com/products/rp-400m-bookshelf-speaker
exterior (!) volume : 8.2Liters
low cut-off (3db) 52Hz
sensitivity : 93db @ 2.83V
I see no speaker on the shelf which can do a similar thing. (low VAS, low FS, high sensitivity)
How are they doing ?
My best hypothesis so far is that they dont, maybe the 93db is a maximum very far from 50hz (and the sensitivity is closer to 89db or something), maybe there's a bump at 55hz (and a hole deeper than -3db between 70hz~120hz).
But, are they doing it ? Can I do it too ?
They lie. They've been caught doing it several times before with independent measurements. The difference in sensitivity between the published and independent test on floorstanders is about 5dB or so.
The measurements I've seen on speakers of that brand have been anything but impressive. They sell with T-shirts and decals instead of quality it seems.
Stereophile's measurements of the RP-600 put sensitivity at 6.4dB less than the Klipsch specification and to quote Audio Science Review "they (Klipsch) publish fantasy stories about sensitivity."
The efficiency is not so much the box, it is the driver. Until you get close to Fs, the box is irrelevant. Not how you couple to the air can make a big difference. That is why HORNS are use for PA as the focus the energy in one direction so the local SPL is higher. The driver still can only push as much air as it can. With funky alignments, you can get resonances that give a boost in the F3 area, but that is not the same as efficiency.
And they lie. The did give a sensitivity @ 1W, but where? 1mm ? Standard is 1M, 1W.
And they lie. The did give a sensitivity @ 1W, but where? 1mm ? Standard is 1M, 1W.
one way to get most of that = 6th order assisted reflex using driver qts ~0.312 and 6dB Q=2 boost at fb.
The reflex port looks like it's meant to be put close to a wall or corner, or on an actual bookshelf, stretching the LF cut-off, reducing baffle step etc. Radiating into 1/2 or 1/4 space.
But only in the pass band. The resonance I spoke of. Unfortunately, it usually requires totally unrealistic port dimensions. I tried several candidates subs and kept getting 20 and 30 foot ports. Caution as you still need to manage X-Max.
The efficiency, is the result of the driver above the loading. Enhanced only by how it may be coupled. For instance, flush mount in a wall so you are radiating into half space.
I've used 6th order ported a number of times in PA, domestic and my bass guitar rig. No unrealistic port dimensions reqd. My first was in the early part of the millennium and the late djk put me onto it.
Klipsch includes room gain in their sensitivity specifications, and on top of that typically drops to 4 ohms in the bass which gives an additional 3 db at 2.83v/1m.
In other words, they're complete fabrications.
In other words, they're complete fabrications.
They used to state sensitivity as 'in room' but trying to search kept putting me on the Aussie site where I didn't see it listed that way, so I didn't post it.
My personal experience with a 2W tube amplifier is that those small Klipsch does not sound any louder than similarly sized and priced bookshelf speakers that are specified at lower sensitivity. They are good speakers for the price anyway.
Better luck than I. I kept needing 5 or 6 inch ports to keep velocity down for just a twin 10 setup. How did you get a broad enough BP for a Bass guitar? Fundamentals from 40 to 400, but overtones clear up over 5K. Seems you need a direct radiator unless you built a 2-way. A couple nice 8 mids?
An big PA sub makes a lot of sense. Does not have to go terribly deep and can be physical larger. For a PA, efficiency is king. A big 40 to 80 resonant ump is not too hard to pull off and it is actually not far from what is needed.
+1
Typically you see some 3 dB between specced and real sensitivity, and likely more.
And despite relatively high sensitivit, typically ugly impedance curves make them impractical for small amplifiers with highish Rout like typical SE amplifiers.
dave
6th order ported not 6th order bandpass. Different things. Some dude named Keele thought it up.
I use 15 for LF and above that I use a pair of B&C 6s and a Selenium D220 on a Celestion 9040. I play ERBs mainly the Ibanez SRMS806.
LF enclosures in the PA were PPSL 18s and above that a variety of horn and direct radiator mids and HF depending on what the job required.