Martin Poulin
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.
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)
For the LSR305/305P electrical mod and few more ideas, refer to the page of the JBL 306P, the sibling of the 305P.
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.
-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.
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)
On left, a bit of roxul's safe and sound acoustic absorber added.
on the right, stock damping foam placement
On left, the 306P and the LSR305 being measured
Not shown, the 305P that I've measured after.
On left, Frequency response of all 3 in my center position with minimal room treatment
The LSR305 tweeter aren't as strong as the new MKii version and roll off earlier
On left, distortion of all 3.
The LSR305 tweeter without ferrofluid shine here. lot cleaner above 1.5 KHz.
On left, impulse of all 3.
The LSR305 tweeter without ferrofluid shine here. lot less residual energy.