loudspeaker efficiency

I'm trying to decode headphone specs and (at least) one doesn't make any sense at all. "Nominal sound pressure level at 1 kHz" is rated at 100 dB SPL at 1 mW (0.28 V at 80 ohms). There seems to be a lot implied in this spec and 1mW generates 100dB SPL??? Trying to measure this I'm off by a mile (20dB). Has anyone spec'd headphones?

doesn't seem so suprising that you can generate alot of sound pressure with very little power when it inside a tiny little closed space, the ear canal.

how did you measure?

-Lasse

"krazy ratbag wanker "

** Headphone makers use a dummy head when making response and sensitivity tests.

YOU would be the ideal man for the job with your completely empty one.

..... Phil

Maximum with hemispheric coverage, unless ratio of Znom/Re is unusual. At frequencies high enough for the coverage to be less, then the far field sensitivity of an array can get higher than 107 dB @ 1 watt 1 meter (or 87 dB @ 1 watt, 10 meters - 1 meter may not be in the far field with a large array).

--
 - Don Klipstein (don@misty.com)

That makes some sense, I guess. "Antenna gain". Thanks. Not sure what to do with this spec. Is there a "standard" model head?

Free space, I used a model of Phyllis' head.

It's med time on Ward-C, Phyllis.

I have a hard time imagining real professional sound reinforcement loudspeakers at Wal-Mart.

Meanwhile, the good stuff did not go away. One thing that did happen is that bands that play in bars do not make as much money inflation-adjusted as they did decades ago, and cannot afford what such bands used to be able to afford.

Increasing amplifier power has changed some popular tradeoff points for bass bins or bass sound reinforcement units, to trade away efficiency for smaller size.

However, folded horn and multidriver bass bins are still available. Drivers for them are still available. 1 inch and 2 inch horns and drivers are still available.

For example, for a non-horn-loaded bass bin, to make with four (4) Electro-Voice EVX-155 15-inch drivers:

The half-space reference efficiency of one is 2.49%. Quadruple for four, to 9.96%. Re is on the low side (5.2 ohms), so Znom/Re is 1.538. I figure "reference sensitivity" of this array to be 103.7 dB in free air,

6 dB higher if placed on a reflective floor.

As for a cabinet design for this for fairly good bass response even with no wall behind it:

I figure a box 33.5 inches tall and 37.5 inches wide, made with 3/4 inch thick plywood and a 3/4 inch lip:

I like results that my "SPKR" program predicts with 11.5 cubic feet of internal volume and a 47 Hz port tuning frequency. On a reflective floor,

0 dB line in the plot by my "SPKR" program is 109.7 dB re: @1 watt, 1 meter.

(I would make the overall depth 20.75 inches including 3/4 inch lip and

2 thicknesses of 3/4 inch plywood, or 18.5 inch internal depth. This adds roughly .8 cubic foot for air displaced by the drivers and interior portion of the port ducts.)

I figure four 4-inch-inside-diameter ducts, 1 in each corner, with duct length 2.4 inches, achieves port tuning of 47 Hz. My experience suggests that this arrangement achieves 44-45 Hz, and to raise this to 47 requires shortening the the ducts to around 1.75 inches deep. You should round the front and rear edges of the ducts as much as feasible to reduce noisy turbulence at high power levels.

(I hope I got the front panel large enough here to accomodate four 15" woofers [more like 15.25 inches] and four round ducts of 4" inside diameter - I have done only "quickie" calculations so far. :) )

The results I see here from my program are -6 dB at about 48-49 Hz, and about -5.5 to -5.7 dB at 50 Hz - meaning about 104 dB sensitivity re: @ 1 watt, 1 meter at 50 Hz - very good actually for a portable bass bin on a reflective floor away from walls.

(I seem to think my program is slightly optimistic here - I expect

103.5 dB sensitivity in farfield on a reflective floor, effectively no wall behind it, with voice coil temperature of 25 C or "room temperature" (Ha-Ha, though this condition is assumed in too many other claims).

So it needs a moderate bit of equalization, preferably done with something other than a 1/3 octave graphic equalizer since those narrow bands get a bit "moo-ey" if a bunch of them in a bass frequency region are boosted around 6 dB.

I would forget about near-full reporduction of 40 Hz anyway. My experience is that the E string on a bass guitar sounds somewhat unnatural with high fundamental frequency content. (That instrument is prone to inharmonicity, more on lower/thicker strings, and I find it sounding more natural without the deeper bass spectral content.) My experience with spectral analysis of content on CDs with bassy bass drums is that there is not a lot below 45 Hz.

My experience also suggests that best port tuning frequencies are in the mid-40's or upperish-mid 40's of Hz. Lower tends to reduce bass frequency efficiency and bass frequency power handling in my experience, while much port tuning frequency much higher than low 50's of 50 Hz tends to noticeably reduce power handling of the lowest bass frequencies that need to handled to some significance. Furthermore, if port tuning frequency results in any sort of peak or sharp corner, I like the result of such best when port tuning is around 45-46 Hz or so.

- Don Klipstein ( snipped-for-privacy@misty.com)

They also got that from lighter cone edge connection treatment. With a price... as in extremely lower longevity.

Today's speakers are less efficient because the edge suspension is of a better quality polymer, life span wise, but has a greater mass than the straight, W-crimped treated paper edge of yesteryear.

I imagine that has something to do with a low end performance degradation.

Modern polymer and other media cones are probably stronger and last longer than paper too, but are also a bit heavier. Of course these references are regarding cone style driver devices (speakers). I think paper cone drivers are still out there in common use. Are not the live music industry drivers paper cone?

The differing data you mention may also refer to differing cabinet designs as well. Back then, there were a lot of "Acoustic Suspension" style cabinet designs, and IIRC they had a higher response.

I think you misread.

The biggest one I see on Ebay is 1600W.

I doubt that they would leave out the upper end of the product line.

Got a link?

I would blame that more on heavier cone mass from "felted" heavier cone design permitted by more-flexible suspension design (keeps down Qts, Qes) and also permitted by increase of available or cost-effectively-available amplifier power through the 1970's and 1980's.

Last time I checked, paper cone loudspeakers are still fairly current.

As for loudspeakers to use in/with non-bass guitar amplifiers - I sense longstanding practice to use loudspeakers manufactured in UK as opposed to USA. Reasoning here: I sense "fullrange loudspeaker design practice" to have differed between USA and UK, in favor of American ones having more-elevated upper-midrange and lower-treble response, deriving from past-ongoing practice used before to maximize intelligibility of voices reproduced byradio loudspeakers. I sense that such American practice was necessitated to accentuate "vocal clarity" by "duller American accents". Meanwhile, it appears to me that "vocal clarity" in UK is somewhat "brighter" / "better", leading to loudspeaker cone design practice towards ones that do not as-much elevate upper midrange and lower treble response.

This is why I suspect UK loudspeakers such as ones by Celestion and Jenson tend to be favored (in my experience) for electric guitar loudspeakers over the "harsher" Electro-Voice and even JBL E-series ones.

I furthermore note as best as I sensed and experienced, though only mildly - Pyle offering sometime in the mid-late 1980's or so (IIRC) musical instrument (especially guitar) loudspeakers, with less-elevated upper midrange and lower treble response that I sensed typical of UK ones. However, what I remember IIRC was some degradation in midrange efficiency in favor of design becoming at least slightly more-woofer-like, with tradeoff of efficiency to enhancement/extension of low frequency response. I would not blame Pyle at all, not even the slightest, for trying such an approach (which I only merely suspect they tried in one loudspeaker line that I have less-than-half-followed).

"Acoustic suspension" referred to a loudspeaker enclosure that was essentially sealed and port-less at all audio frequencies including down to 25 or maybe 20 Hz or so ballpark, including many that had little diiference from "truly sealed" at 10 Hz.

"Acoustic Suspension" referred to a sealed loudspeaker enclosure combined with a loudspeaker whose suspension had less stiffness than the air in the enclosure had.

I remember "acoustic suspension" as a design for "higher fidelity" with more trade-off against efficiency in favor of flatter frequency response, likely-favored by heavier cones of less-midrange-resonant "felted" design, and also depending on available amplifier power increasing.

Furthermore, I remember derivative "tuned port" / "bass reflex" designs that greatly further extend bass response, significantly improving how low in frequency reasonably flat frequency response is achievable, including in part extension downward of -3dB point (even compared to same box size and same "half space reference efficicncy") at mild-ish expense of rolloff ultimate slope becoming24 dB/octave rather than 12.

Heck, in 12 dB/octave highpass filter loudspeaker enclosure design, it appears to me that "effective volume" is 1/ (1/Vas + 1/vb). But in design for 24 dB/octave ultimate bassward rolloff, I sense that 100% of the air volume within enclosure in question is "workingfor you".

- Don Klipstein ( snipped-for-privacy@misty.com)

With the size of that surround, it only qualifies as an 18" if one wants to get technical about it.

I did not know that there were 22" driver form factors out there even.

MTX is retarded, BTW, if they think that there is $11k of value there. I guess gang boy retards will spend their illicitly obtained gang boy retard drug money on lots of stupid shit.

That's why a baseball cap costs $30 now. The world is full of utter idiots.

MTX deserves to go bankrupt with price schedules like that.

They are following the Monster paradigm, and I think that all companies that do should eat shit and die while intelligent consumers stand by laughing.

I thought the sex change would have helped Phil, but he just went from an ass to a bitch.

rated

measure

There are several, depending on which collection of properties you wish=20 to have represented. Not the least of which may be age based size.

Oh, great. "That's the nice thing about standards; there are so many to choose from." Any pointers to a source for these things?

make

rated

lot

measure

pressure

=20

It has been many years, i would have to google them up again.