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Author Topic: Help me understand about SPL please?  (Read 676 times)

Art Welter

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Re: Help me understand about SPL please?
« Reply #10 on: September 16, 2020, 08:52:39 am »

Probably the biggest differences are with bass reflex (vented, ported) design and various pass band designs.  Bass reflex lets us put a lot of bass in a relatively small box, and the trade off is typically high levels of 2nd and 3rd order harmonic distortion. 
Tim,

Using the same drivers, a bass reflex design will generally have less 2nd and 3rd order harmonic distortion than a horn loaded design for a given excursion. Band pass designs can acoustically filter some distortion.

That said, a (proper) horn loaded design will require less excursion for a given SPL output, using a larger box.

The design of the drivers themselves makes a huge difference regarding harmonic distortion- some have "built in" distortion almost regardless of excursion, other more well-built drivers can maintain low distortion through a wide dynamic range.

If you want to compare distortion and out put of all sorts of bass designs, Josh Ricci's Data Bass web site is a great resource:

https://data-bass.com/#/?_k=3v6efr

Art
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Doug Fowler

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Re: Help me understand about SPL please?
« Reply #11 on: September 16, 2020, 11:30:25 am »

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.

Mike -

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Ivan Beaver

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Re: Help me understand about SPL please?
« Reply #12 on: September 16, 2020, 02:36:13 pm »


{Measure what you can; if you can't measure it does it matter?}
Physics and a bunch of Not So Famous Dead Guys identified electrical and physical phenomena that allows us to use mathematics to represent how things work, and demonstrate what happens when various Dead Guy parameters are changed.  But even with that, subwoofers with identical 'numbers' can sound very, very different.  All fine and lovely, but what about things we aren't measuring for?  Maybe because we haven't found a way to define what we're perceiving in ways that fit our understanding of the physics?  OTOH, if we can hear it we should be able to measure it, eh?



Exactly.

I have often heard the statement "I can hear things that don't show up on the measurements".

We can measure all kinds of things that your ear can't hear/realize. 

The argument usually assumes that a 1/3 RTA is the "ultimate measuring tool".

If you can't measure what you are hearing, then you are simply using the wrong tool for measurement. 

A yardstick cannot measure weight for example, no matter how accurate it is.
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Dave Garoutte

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Re: Help me understand about SPL please?
« Reply #13 on: September 16, 2020, 03:12:52 pm »

A yardstick cannot measure weight for example, no matter how accurate it is.
If you add a spring it can! :o
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Mike Henderson

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Re: Help me understand about SPL please?
« Reply #14 on: September 18, 2020, 12:28:11 pm »

If you add a spring it can! :o

Well guys, I am super happy to say that the SB1000e does the job!

It has a pair of RCF LP300 which the owner wired to 4ohms and I bridged my crown 3600 in mono so that matchup is good since those RCF's are 1000w continuous.

I am getting good distance and powerful deep bass and for the most part wherever I stand in the garage I am hearing the same bass just like at my bud's. That surprised me with the room acoustic issue but my gamble paid off!

So now as is usually the case I have to do something about the tops. I will create another thread for that, appreciate the help!

p.s. This is the thread for the tops: https://forums.prosoundweb.com/index.php/topic,174350.0.html
« Last Edit: September 18, 2020, 12:47:56 pm by Mike Henderson »
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Re: Help me understand about SPL please?
« Reply #14 on: September 18, 2020, 12:28:11 pm »


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