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lonewolf
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 Post Posted: Wednesday Oct 29, 2003 
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I've noticed that when discussing speakers, just about everyone on the Rockpage (including the senior members) are hung up on WATTS. "How many WATTS are they?" etc....

WATTS by themselves don't tell you much about the output level of a speaker. What you should be asking is:

Whats the maximum SPL at rated output?
Whats the sensitivity?

For instance:

A cabinet with a 100db (1w/1M) sensitivity running at 300 watts RMS will be just as loud as a cabinet with a 97db sensitivity running at 600 watts RMS. The sound pressure level doubles with each additional 3db of sensitivity.

So, which cab would you want? The efficient one where you only need 300W, or the less efficient one where you have to find a 100lb 600 watt megalith costing hundreds more just to get the same output?

Then there's the Peavey syndrome...Peavey now rates their cabs in watts "program power". Thats all fine and good, but I don't think they want you to know that "program power" is generally twice the RMS power and half the PEAK POWER ratings for MOST other companies.

Shame on Peavey.....
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Ron
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 Post Posted: Thursday Oct 30, 2003 
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Good topic lonewolf.

Audio companies have played the "watts" game forever, and it probably will never end.

Buyers should only believe power specs when they are accompanied by "RMS" and a frequency range ( usually 20 - 20KHz ). If there isn't a frequency range, then the measurements were probably done at 1KHz instead of the entire music range. The 1KHz measurement can be many times greater than real world output.

Sorry for being nit-picky, but it takes +6dB to double the sound pressure level (SPL) of a system. But you are correct in that it takes double the power, or double the speaker surface area to get +3dB. Also, since our ears aren't linear in response to SPL, it takes ~ +10dB for a "perceived" doubling of volume. In theory you could double the number of cabinets in your system (+3dB) and quadruple the power (+6dB) and still not get the "perceived" doubling (+10dB) of volume.

When shopping for speakers, sensitivity is important, but check that any "extra" efficiency is coming from the loading of the speaker driver in the cabinet ( horns, folded "W's", scoops, etc. ) and NOT the driver itself. If the driver itself is more efficient, that is usually at the cost of motor and cone mass. In other words, it usually takes less power to move a "wimpy" driver. Exceptions would be drivers made of high density, light-weight exotic materials ( kevlar, titanium, etc. ) and unconventional designs.

Whew, my brain hurts.

Ron
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lonewolf
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 Post Posted: Friday Oct 31, 2003 
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While it may be true that a +6db gain could be required for a double in volume perception by humans (it is probably less for wolves), BY DEFINITION, a 3db gain in SPL is a double in SPL. By definition, a 3db gain on ANY logarithmic scale is a double. That's just good old engineering mathematics, not perception. But don't take my word for it, go on over to EE West.

One of the best things you can do to check out cabinets is look at the 1W/1M frequency response curve at the frequency region you intend to use it in. You can get a good idea what the overall sensitivity will be and how much EQ compensation you will need to make it flat.

I found this especially true of SUB CABS and drivers with extended frequency response into the 3Khz+ area. There are a lot of sub cabs and 18" drivers out there that advertise a 100db sensitivity, but when you look at the chart, its 104db at 3khz where you won't be using it and maybe 90db at 60hz where you want it to be 100db. That's an awful lot of EQing. I believe that all of the speaker manufacturers are guilty of this and if you look hard, you won't find many, if any, drivers or cabs with an average sensitivity of even 95db below 120hz. If you do...LET ME KNOW!!!!!
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Last edited by lonewolf on Friday Oct 31, 2003; edited 1 time in total
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lonewolf
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 Post Posted: Friday Oct 31, 2003 
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On the topic of perception, our perception varies with frequency (and whatever is left of our hearing after years of pounding stages). As a veteran soundman, you know the old trick of boosting the 2.5K to 4K region. Shure does it with the SM58. An SPL boost of 3db in this region will raise volume perception by as much as 12db because those are the "clarity" and resonant frequencies of the human ear. Lets call perceived volume PV. It breaks down like this:

At 20hz, it takes about 20db SPL gain to get 3db PV gain

The SPL number continuously drops until 200hz:

From 200hz to 1.5Khz, 3db SPL gain = 3db PV gain

The SPL number continuously drops until 3.5Khz:

At 3.5Khz, 3db SPL gain = 12db PV gain.

The SPL number continuously rises until 6Khz:

At 6Khz, 3db SPL gain = 3db PV gain

The SPL number continuously rises until 10Khz:

At 10K, 8db SPL gain = 3db PV gain

With all that gain, my ears hurt!
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lonewolf
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 Post Posted: Friday Oct 31, 2003 
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Speaking of surface area, another speaker phenomenon is ACOUSTIC COUPLING. This happens in the frequency range below 400hz and is especially useful with subs. When you take 2 identical cabinets (or drivers) and place them side by side running at the same power, they "acoustically couple" in the frequencies below 400hz. In addition to getting the 3db gain from doubling the source, you get another FREE 3db gain from the acoustic coupling effect. The effect diminishes substantially with horn loaded cabs, but works great with front loaded cabs where the surfaces are parallel.
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Ron
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 Post Posted: Saturday Nov 01, 2003 
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Great tech talk lonewolf.
Another acoustic loading effect that can be used at certain times is the "corner effect" where the corner of a room can act like a megaphone and raise your SPL. I worked an odd shaped room years ago, with no room to the left of a recessed stage. We loaded the whole PA stack into the corner to the right of the stage. Very efficient, though it tended to pull your focus away from the band.

I think we are talking apples to oranges on the dB thing also. I agree that any 3dB increase represents a doubling. Where the discrepancy is, I believe, is that I was talking source gain vs. SPL gain, and using standard models of acoustics which don't take loading into account. The acoustic source of a cone speaker has to increase by +6dB because of the inverse square law. This is due to the spherical spreading of the source pressure once it exits the enclosure. This applies mainly to front loaded cabs.

If you model the acoustic spread as a cylinder instead of a sphere, then a 3dB increase in source would result in a 3dB increase in SPL, but in the spherical model, the +6dB in source only gets you +3dB in actual pressure.

That's why all the corner loading, funky enclosures and floor reflections help. They counteract the inverse square law by turning the spherical radiating pattern into more of a cylinder.

Brain still hurts.
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lonewolf
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 Post Posted: Saturday Nov 01, 2003 
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Now I see what you were talking about--acoustic output--moving some air. I would like to design an "inflatable stage" where you throw a box up there, pull a rip cord and voila, instant stage. Since that will never happen, I've been looking for the smallest, most efficient non-powered cabs available. There are some nice subs out there with 12" drivers, but the acoustic output just wasn't anywhere near the 18" cabs and the EAWs weigh a friggin TON.

I was unable to find anything that even came close to the EV SX300 for a mid-high cab that weighs 40lbs. The problem was finding a sub that would match up with them, move some air and still be small and light enough for one person to easily carry. I gave Ron Jarrett a call to see if he had any subs from his old store and he had a pair of EV S18s that I quickly snatched up. The S18s are a decent sub, but couldn't quite match up to the output of the SX300. After looking at what seemed to be hundreds of .pdf spec sheets, I reloaded the S18 cabs with EV 18BX drivers. They have the extra low end and proper excursion that would bring a 6cu.ft. front loaded cabinet up to the SX300.

Anyway, I am thinking of starting a 3 piece band, so it was back to the drawing board to microminiaturize a system to drive them. Before visiting the Banditos at the Hitching Post last night, I pieced together the last component. This system is capable of delivering 130db average SPL (1200Wrms/1M) FLAT from 50hz-20khz with 135db peaks and yet weighs a total of about 250lbs. the dbx DriveRack PA does a lot of the work and there's even an 8 frequency Sabine feedback filter for the monitors. Its only 6 channels, but that shouldn't be a problem for most situations. Need more channels? Throw a Yamaha Promix at it. I finished it this morning...check it out:

http://www.geocities.com/jcr5/pa.html
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Last edited by lonewolf on Sunday Nov 02, 2003; edited 1 time in total
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lonewolf
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 Post Posted: Saturday Nov 01, 2003 
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17-7 at halftime!!

I believe that's also called "quarter-space" efficiency (the corner effect).

Is the cabinet back supposed to be up against a back wall for that condition, or does the cab just need to be next to a wall (or is next to a wall called half-space efficiency)?

Was that odd shaped room at the Lion's Den?
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facingwest
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 Post Posted: Saturday Nov 01, 2003 
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Wanna check out cab specs that'll blow your mind? Check out Mackie's Fusion line and the one just right below it. They're claiming to have 136 SPL. Even the subs have SPL's higher than anything I've ever seen. Goto www.mackie.com and see the specs. I'm a little curious to know why they're able to have such high SPL ratings over just about any other company out there.
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Ron
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 Post Posted: Sunday Nov 02, 2003 
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Hey John,
Never trust ANY specs with the word "Peak" in them. That's what I call the RBF rating. (Right Before Flames). It's RMS or nothin'.

Sorry lonewolf,
I can't remember which room it was exactly, but it wasn't the Den. I think that the quarter/half efficiency is all about getting closer to a cylindrical model vs. a spherical model.

From all the pros I've talked to, acoustics is THE black art of engineering. Anything goes, and a TON of bullshit is spread. I may be a tech head at heart, but I only believe in the band and crowd's response when it comes to sound. The sound guy ( in my mind ) is as much an artist as any member of the band. Maybe not as talented, but definitely as critical to the overall OOMPH.
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lonewolf
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 Post Posted: Sunday Nov 02, 2003 
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Yep, they're impressive--one of the best specs I've seen--on the sub anyway. The original point of my post was efficiency and size, not SPL. The SPL is just a way to compare the outputs. My subs weigh 65lbs each and only require about 325wrms to get 125db each. Put two of them side by side and 650wrms produces 131db.

The fussion (what's with the 2 ss's) subs weigh 145lbs EACH and require either 1250wrms or 1600wrms to get those SPLs. Their specs are sketchy and are not specific about this--the cab is rated at 1600w and the amp at 1250w. They don't specify which one produces 136db. They absolutely do have impressive specs, probably from the acoustic coupling of the 2 drivers, but who wants to carry them?

The fussion 3000 weighs in at 246lbs EACH! Thats as much as my whole friggin' PA. You will have to factor in the cost of a FORKLIFT! They are slightly less efficient than my system at 1300wrms to get 130db SPL, versus 1200w.

Keep in mind that a 130db system is more than enough to handle 98% of the indoor venues in central PA. You are right, the Mackie's ARE impressive. Have you heard any?
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Last edited by lonewolf on Tuesday Nov 04, 2003; edited 1 time in total
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Ron
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 Post Posted: Sunday Nov 02, 2003 
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I would have thought that when the marketing guys found out that "fusion" was taken, they'd have tried something other than "fussion". Sounds like something for the geriatric crowd.

Oh, and I think it was "Banana Joe's" near Pittsburgh, not the 'Den.
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lonewolf
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 Post Posted: Sunday Nov 02, 2003 
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The "full space" condition is "flown" with no wall, ceiling or floor nearby. The sound is allowed to project in all directions with no horn effect. "Half-space" is when the room is halved by putting the driver against a wall OR on the floor (but not both), and cutting the projection area in half. What I'm not sure about is "quarter-space", but I think thats when you put the cabinet on the floor AND against a wall and half the half-space condition. If that's the case, the "corner effect" must be an "eighth-space" condition. Apparently each time you half it, you get a 3db gain in SPL.

That's a good point about RBF. The cabs and drivers I'm familiar with all have "peak" ratings of 4 times the rms ratings. Thats 6db of instantaneous headroom between the average and peak SPL. The Mackies only have 3db between their "average" and peak SPL. I wonder if Mackie has engaged in the "Peavey syndrome" that I mentioned earlier and are using program power in their average calculations rather than rms power. In any event, the 3db spec is simply not enough instantaneous headroom in my book, especially for subs. I'm guilty of not following that rule on my mini-PA. I only have about 75wrms or 1db (about 400w to peak or 3+db) amplifier headroom at full rated output of the speakers (there are TWO limiters between the EQ and the speakers). Still, this is better than most systems that I see where they matched the amp's power 1:1 or less with the speaker ratings and there is no clean headroom.
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facingwest
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 Post Posted: Monday Nov 03, 2003 
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I haven't had the pleasure of hearing the fusion series, however, our soundguy uses Mackie tops and bottoms and it's one of the most impressive PA setups I've seen in a long time. The highs are crystal clear, smooth mids, and a deep punch for the size of the system. If you ever get the chance, check out one of Retro's shows and you'll get to hear it for yourself. I've heard a lot of different setups and this one really caught my ear. Something really cool about Mackie is their cabs are loaded with EAW's and pound!!
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lonewolf
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 Post Posted: Monday Nov 03, 2003 
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EAW doesn't make raw drivers. They use RCF drivers. I believe that Mackie uses them as well. RCF makes very good stuff.
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Craven Sound
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 Post Posted: Monday Nov 03, 2003 
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I think that EAW USED to use RCF components until they were bought by Mackie. Now, EAW uses whatever Mackie supplies them. There are a lot of pissed EAW owners that are getting cheap replacements while their equipment is still in warranty. Kenton Forsyte should take his company back.
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tonefight
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 Post Posted: Tuesday Nov 25, 2003 
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I've got the basics of this topic but you guys definatly have a better handle on it so why don't you check out this link and let me know how they rank ( I'm pretty much stuck with them now though )

http://www.carvin.com/cgi-bin/Isearch.exe?P1=APS

The 1588A speakers are the core to the system i'm working on and I will probably be buying the 1801A subs very shortly.
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facingwest
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 Post Posted: Wednesday Nov 26, 2003 
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For the buck, Carvin doesn't make bad stuff. However, as many things I saw having to be replaced, they are not worth it. Everything from horn drivers, to subs, to in-ear monitors, to poweramps, to boards, to the circuitry within their cabinets, to cables going bad quick, to........... Need I say more? Wink Carvin's new stuff is J-U-N-K!!
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tonefight
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 Post Posted: Wednesday Nov 26, 2003 
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Well that's not what I wanted to hear John, I didn't realize you guys had that much trouble with their stuff. I knew the system up at the pub was mostly Carvin stuff and I knew the subs got blown out but I figured that was from pushing them. Actually you guys using their stuff and seeing it at the pub kinda led me to feel a little secure in buying it. At this point I'll just have to cross my fingers and hope for the best.

Has anyone else had trouble with Carvin gear?
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facingwest
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 Post Posted: Thursday Nov 27, 2003 
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One great thing Carvin is good for is replacing gear under warranty. Everything that was broke, they either replaced entirely or sent replacement parts. I had a FET1000 poweramp and EQ from them for years and never had any troubles....Well, until I lent the power amp to my brother. Not sure if it was its time to go or what. I did get a lot of use out of it before it was replaced by a newer one (Carvin traded the old poweramp and some change for it), which blew 1 channel within a few months. The second channel just went out on me last weekend at the Castle, which made me run my setup through the monitors.
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Dave
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 Post Posted: Thursday Nov 27, 2003 
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tonefight wrote:

Has anyone else had trouble with Carvin gear?


I have a bunch of Carvin gear. I purchased all of it used from various sources. I have 3 DCM2000 amps and a DCM600. I also have Carvin TR series speakers and subs. All of it has worked perfectly. The DCM amps seem to be built like tanks. A couple years ago I was talking to a Carvin rep and I told him how I was running 4 cabinets off of a bridged DCM2000. He said 'you shouldn't be doing that' (2 Ohms). Well, I had done it several times and the amp never quit and is still working great along with 2 others now. This was obviously a no-no and I know better now, but it is a good example of how hard you can run thier amps. I get crap about my Carvin gear from a lot of guys, but it works. I did just sell a Carvin 24 channel mixer. I was the 3rd owner and it worked great.
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