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Help me understand about SPL please?

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Mike Henderson:
Hey guys, how are you all doing, hope you all are being safe and all is well!

So this is troublesome Mike again [sorry] this time with a related issue as a spin-off from my previous questions.

If you guys might remember I was wondering why the SB1000 power-wise would be more pounding and give more distance than my Dual 18" Sonic:

https://www.sixstardj.com/sonicr218sub.html

I just got the EAW SB1000e sub [FINALLY!!] and it has the RCF LP300 Woofers and looking at it's specs I was very surprised to see that it is only 1000 Watts "continuous" power:

https://usspeaker.com/rcf%20-%20L18P300-1.htm

The Eminence Kilomax Pros I had on the Sonic is higher rated than that RCF 300:

https://www.eminence.com/speakers/speaker-detail/?model=Kilomax_Pro_18A

So I was told by a speaker tech friend of mine that it's the SPL which makes the difference.

The Sensitivity in the Kilomax is 95.8 and in the RCF is 97 so not much difference. The SPL in the Sonic cab is 102 and in the SB1000 132 Long Term and 138 Peak so that's a whopping difference so that I can understand, regarding the cabinets themselves that is.

So my question is it seems to me when comparing those 2 mentioned above that it is the cabinet's specs and design which mainly determines the power and distance of the bass, is this correct please? you guys know I am not all that technically sound so I am just trying to understand this as best as I can, thanks.

David A. Williams:
I'd like to put off talking about driver specifications for a minute and hone in on the following:

--- Quote --- ... I was wondering why the SB1000 power-wise would be more pounding and give more distance than my Dual 18" Sonic:
--- End quote ---

People are often misguided about the relationship between SPL and distance. To set the record straight: each time you double your distance from a speaker, that speaker becomes 6 dB quieter. There's no way to design a single cabinet or a horn to skirt this issue (we'll ignore line array theory for now...). Manufacturers who advertise "long throw" speakers really mean "loud, with a narrow coverage angle" and it seems to confuse people. Without diving into spec sheets I'd fully expect an expensive product like the SB1000 to play louder than your other option, but "more distance" is a shaky claim.

Now, let's get into some of those specs:

A thermal limit is implied by a "continuous" power rating. Exceed this for long enough and the voice coil will overheat, causing irreversible damage. A 250W difference in this specification isn't by any means remarkable, and isn't enough to overcome the difference in sensitivity in this case.

Now, you've given some cabinet specs as well, but keep in mind these are only valid for the OEM drivers, which you don't have. Disregard them; besides, the number you've given for the Sonic is likely a halfspace sensitivity number, and for EAW a halfspace max spl number. Completely different information.

Finally, let's deal with the fact that you aren't using OEM drivers. Without knowing the volume and tuning of the enclosure, you can't be sure that your drivers are even safe at their max rated power. The TS parameters could be such that your drivers over-excurt at far below their rated power.

Caleb Dueck:

--- Quote from: Mike Henderson on September 15, 2020, 10:48:46 AM ---I just got the EAW SB1000e sub [FINALLY!!] and it has the RCF LP300 Woofers and looking at it's specs I was very surprised to see that it is only 1000 Watts "continuous" power:

--- End quote ---

There isn't any one single spec that determines the difference between a Pro subwoofer and a DJ subwoofer.  Roughly - Pro grade is the best, MI (Musical Instrument, IE music store brands) is a step down, and DJ is yet another step down.  There are a whole list of variables that get their corners cut each time you take a step down.  Power handling is one of the more minor variables. 

Without rehashing the whole list (a week with Google, the DIY subwoofer threads on soundforums.net, etc will really open your eyes) - the very short summary is that if you need real bass, ignore DJ brands, step over the MI brands, and look at Pro brands.  Used Pro, like you bought, is a good way to ease into things.  The more modern Pro offerings are even better than the older pro offerings like the SB1000.

A subwoofer is the sum of all parts - the quality of the drivers themselves, the design of the enclosure, the type of enclosure (horn loaded, rear horn, vented, band pass, T-line, infinite baffle, sealed, etc), the quality/stiffness/density of the enclosure, the type of amplifier powering it, the processing in the amplifier. 

As David said - subs don't 'throw' bass.  Part of why horn loaded subs 'throw' better is that the mouth of the sub isn't right against the face of the driver, so the most drastic drop has already happened.  When you eliminate the artificial 'super loud up close', at distance it's more even.  It's easier to visualize than explain. 

The first step to learning how subs really work - is to ignore the number of watts in the advertising, especially with lower end products.  All they are is for marketing, where larger numbers sell more boxes.   

Chris Grimshaw:

--- Quote from: Mike Henderson on September 15, 2020, 10:48:46 AM ---
The Sensitivity in the Kilomax is 95.8

--- End quote ---

Bet it isn't.
As I said in another thread, those things barely had enough motor for a 15", let alone an 18". They'll probably have fairly low sensitivity below 100Hz.

Chris

Caleb Dueck:

--- Quote from: Chris Grimshaw on September 15, 2020, 01:22:24 PM ---Bet it isn't.
As I said in another thread, those things barely had enough motor for a 15", let alone an 18". They'll probably have fairly low sensitivity below 100Hz.

Chris

--- End quote ---

Your're right, at 30Hz, it's 78dB. 

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