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View Full Version : woofers cone area and "feeling" at low SPLs



pos
11-13-2007, 07:28 AM
I've read many times that the 2245H produces a special "feeling" of deep and solid bass, something you cannot obtain with a single 2235H, even at moderate SPLs.

Given the fact that both properly loaded (according to JBL enclosure recommendations) drivers will have quite a similar frequency response, what gives the 2245H an advantages there? Is this solely related to cone area? Will a dual 2235H setup lead to the same king of feeling?

Is there any reason for someone listening at an average 90db level to choose a 2245H vs a 2235H ?

Robh3606
11-13-2007, 11:01 AM
Is there any reason for someone listening at an average 90db level to choose a 2245H vs a 2235H ?

Well that 90db average is misleading. Where you are going to hear the difference is on transients/impact and the sub 40Hz area. Cone area is obviously a big advantage when you are going low. I run 2235's in my 4344 wanabe clones LE14h-3 in my HT as stereo subs. I don't feel like I am missing anything in either system. The LE-14's actually are more extended in my room due to placement.

I have heard 2X 2235 in a pair of 4350 and in the room they were in it was impressive to say the least. They didn't boom and the shudder had flap your pants legs power. There was more sheer brute force power compared to what I am used too but I don't know how much of that count the cycles feeling was due to the room they were in.

I would go with the largest drivers that make sense in your room. I wanted to get 2245 from the Tent Sale way back when but couldn't deal with the cabinet sizes.

Rob:)

pos
11-14-2007, 08:37 AM
Where you are going to hear the difference is on transients/impact and the sub 40Hz area.
I see, it makes perfect sense. That is something that is difficult to see on graphs.
I have difficulties to understand why (2) 2235H will yield to an imporvement in VLF compared to (1) 2235H at moderate SPLs. There is something with that mutual coupling thingy I guess, but that is beyond my understanding...
In fact I think the 4350 goes lower than the 4343, in the specs, and that should be audible even at low SPLs. The 4350 is tuned lower (22hz?) and rely on the +6db mutual coupling effect to rise its "banana curved" VLF response.
Does that make sense?


LE14h-3 in my HT as stereo subs
So you changed your le14a to the new generation? Is it a big improvement?


I would go with the largest drivers that make sense in your room.
That is also something I have difficulties to understand. I can see the relation between SPL and room size, but not between cone area and room size. If I want to have 90db at 30hz in my fairly small room, and if a 2245H has more impact than a 2235H at that frequency, even at these low SPLs, why shouldnt' I go with the 2245H? If the room geometry tends to boost low frequencies then I could still eq or even lower the Fb and get extended basses, but that would also be the case with a 2235H or any driver with a similar response curve. I would then need even less SPLs at 30hz, but would still gain some impact by using a 2245H instead of a 2235H.
Or is this that the SPLs requirements at VLF become so small that the difference in cone area becomes Insignificant?

Ducatista47
11-14-2007, 09:50 AM
This response is outside the realm of engineering, but the 2245H is considered by some - myself included - as having more finesse than the 15" offerings. This is not an SPL issue, but rather about the quality, not the quantity of the sound.

I used to run 4333's a lot in this room (every bit of an L300 soundwise, not as modern as the 2235H but a nice alnico fifteen), and the sound from the 2245H in my 4345's is way different. I have often seen the term "more musical" written here to describe the comparison. The sound is, to my ears, more accurate, without a hint of strain and incapable of inducing listener fatigue. To be even less scientific, sweeter. Those are qualities worth having.

I suspect the 18" is capable of more bass extension, but I can't prove it. I biamp and cut it off at 30hz, JBL's recommendation for this particular monitor. I have nothing against experimentation, but I have found that trying to improve on or second guess the work of JBL engineers is an efficient way to waste time.

Clark

pos
11-14-2007, 10:45 AM
an efficient way to waste time.that's what life is all about ;)

These 2245 look damn nice. I know they ARE overkill for my room and listening habits BUT all the rest I have is also overkill (2435H compression drivers, 2123H mids, 2500W worth of quality amps, ...).
So when I am there why should I settle with a lonely 15" per channel ?? :D
Now I want a pair of le14H-3 per side at a BARE MINIMUM.:barf:

Robh3606
11-14-2007, 11:17 AM
Hello Clark


This response is outside the realm of engineering, but the 2245H is considered by some - myself included - as having more finesse than the 15" offerings. This is not an SPL issue, but rather about the quality, not the quantity of the sound.

That's a club I would like to join. Just don't have the room:banghead:. These drivers don't sound the same. My favorite is the LE-14A or H's over a 2235. They just sound better to me. Not that there's anything wrong with the 2235. Just a personal preference.

Hello POS


That is also something I have difficulties to understand. I can see the relation between SPL and room size, but not between cone area and room size

SPL is really what you are looking for with VLF or at least the abillity to produce 100db+ peaks cleanly. All other things being equal more radiating area will get you there more easilly with lower excursions required and in most cases lower power.


A 4350/55 is really a bad example as far as mutual coupling being used to extend the low end on a speaker system. The 2235's in the 4350/55 are coupled over their entire range for maximum SPL. You need to look to the 4435 or the Everest 2 as examples where the range is effectively extended.

The 4435 has one driver rolled off below 100Hz or so and run the other full range up to the horn. The 1/2 driver couples below 100Hz and extends the range compared to a single woofer and sums in a way that it has the same sensitivity as the single fullrange woofer. Great way to get there. You double your power handling as well where you really need it.

Rob:)

pos
11-14-2007, 11:41 AM
Yes the 4435 really is an elegant design! I don't understand why Westlake did copy that one.
Regarding the mutual coupling in 4350, I think the +6db only occures under 150hz or so (following 1/4 wave length distance rule), so it sort of also extends bass, the 150hz-300hz range being only +3db (in practice I imagine the gain drope slowly from 6db to 3db accros that range?...).
I gather this is what commands the lower tuning of these boxes. I also read here that the double 15" Westlakes where tuned even lower, around 20hz.

Ducatista47
11-14-2007, 02:55 PM
that's what life is all about ;)

Sorry, I didn't mean to put down DIY. I was talking about specific designs and recommendations. JBL engineers are really good!



Hello Clark
That's a club I would like to join. Just don't have the room:banghead:. These drivers don't sound the same. My favorite is the LE-14A or H's over a 2235. They just sound better to me. Not that there's anything wrong with the 2235. Just a personal preference.

Notice I didn't include the 14 inch offerings in the comparison. :D With at least half of my friends preferring the LE14-X over anything else - and that would be in the world - I would not dare step on that idea. I don't see any 15 inch in the 250Ti either. Greg Timbers always has my full attention. And I again thank him for the 4345, 2245H, 2122H and everything else. If I could afford an Everest II pair, I'd thank him for that too.;)

Clark

toddalin
11-14-2007, 05:02 PM
Can't be solely related to cone area. You also need to consider the cone throw.

My Sunfire Signature (a 10" with a 10" passive radiator) can shake your fillings loose and easily keeps up with the three 2235s, the W15GTI and four 10" surrounds in my HT setup.

All out of a <1 cubic foot cube. :blink:

Robh3606
11-14-2007, 06:16 PM
Can't be solely related to cone area. You also need to consider the cone throw.

It's not. The volume of air moved is also key. Figure the effective diaphram area times the peak to peak X-Max at X frequency. The lower you go the more volume of air you need to move to keep the SPL the same and the larger the excursion. That's why a larger cone area gives you an advantage and why a smaller 10" cone can surpass a larger cone by having a larger X-max. The problem is you loose efficiency with these smaller heavy cones.

You also have the issue of volume vs quality. I find the smaller cones to simply not sound as good. At least the ones I have heard

Rob:)

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