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November 2020,

 

Living in a small apartment, I had to forget the horn system for a while and decided to buy more of the excellent JBL 3's series speaker to fill the gap. When I say that the 3's serie are excellent, this is relative to a budget speaker and with cabinet modification (adding brace at least) to stiffen the nasty 220hz resonating mode the JBL have.

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I'm using 6 JBL for obtaining a 6.1 system.

-3 of the JBL 306P (left, center, right)

-2 LSR305 (Surround L and R)

-1 JBL 305P (rear center, in mono)

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For the LSR305/305P electrical mod and few more ideas, refer to the page of the JBL 306P, the sibling of the 305P.

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Like the JBL 306P:

 

-the JBL 305P use the same class D amplifier (STA3050BW based) but the 305P use no heatsink and given lesser output power advertised, the powersupply rail is likely held a tad lower. No problem here.

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-the cabinet is 15mm thick and unbraced. This is a  problem, on the 306P, cabinet main resonance was ~240hz, on the 305P, it is around 220hz, strange but I measured it lower.

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On left, the very beneficial ferrite mod (see 306P page for details)

 

on the right, extra bracing added.

(1 horizontal cross brace and 4x 45degree brace) 

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On left, a bit of roxul's safe and sound acoustic absorber added.

 

on the right, stock damping foam placement

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On left, the 306P and the LSR305 being measured

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Not shown, the 305P that I've measured after.

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On left, Frequency response of all 3 in my center position with minimal room treatment

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The LSR305 tweeter aren't as strong as the new MKii version and roll off earlier

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On left, distortion of all 3.

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The LSR305 tweeter without ferrofluid shine here. lot cleaner above 1.5 KHz.

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On left, impulse of all 3.

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The LSR305 tweeter without ferrofluid shine here. lot less residual energy.

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