Jbl sr4715a

[MoD]

Hello everybody!I was offered two of these speakers for reasonable price. I think. Maybe. They are P.A. subwoofers, and I think i could use them crossovered at 650 Hz to JBL 2360. What bass extension could be produced from these speaker in hi fi use without EQ? They are specified at 40 - 1100 Hz at -10 dB. Is that - 10 dB at 1100 Hz or at 40 Hz?

[RMC]

Hi MoD,

The -10db is likely applicable at both frequencies indicated considering the way its presented in the SR series brochure.

The cab is loaded with two 2226H (in paralell therefore 4 ohms) and the bass extension with no EQ would be quite similar to that of a single 2226 in half the cab size. Being SR the main gain here is in efficiency (sensitivity 100 db instead of 97 db) due to double identical woofers used. Also higher power capacity for another +3 db.

Hard to say exactly what bass extension you would get in absence of a net box volume and no box tuning frequency provided in the brochure.

The exterior box dimensions lead to a 11.2 cu.ft. GROSS cab volume but the net number is what matters. Failing a Vb and Fb one can only try to estimate, sort of a guessing game... From the top of my head my guess is that if its -10db at 40hz then i doubt it would do better than 50hz as a really useable F3 (no EQ as you mentioned).

Richard

[MoD]

Thank You for answer RMC,That is exactly what I am afraid of. I was thinking of use these boxes as would be used 4648A. Not much of bass extension there... EQ would be, must.Regards!

[RMC]

MoD,

I forgot to mention the following in my previous post.

Don't be surprised by the cab you were considering. There's a number of PA and SR cabs having an F3 bass "cutoff" in the 50-80 hz range. JBL has/had a number, Peavey also, as well as others. An example of these is music store type PA/SR cabs sold.

The manufacturer's engineers often prioritize efficiency (with its sensitivity derivative) and portability at the expense of deep bass. Pretty low bass usually demands large woofer(s), and more importantly, large boxes to deliver at the same time good efficiency. The compromise made is frequently low frequency bandwidth extension, same for many other makers.

Some LF cabs do come with one or more 15", which is a large driver size, but the woofer used is not necessarily engineered for very low bass, instead it could well be designed to provide higher sensitivity.

The era of big everything seems pretty much fading away. Compact, portable, array them as need be, appears to be the new normal, along with adding sub(s) when the situation requires.

Richard

[Riley Casey]

It helps to remember that the very lowest frequency of interest to a portable sound vender be it Clair Bros doing arena rock tours or your local bar band is the 40 hz low E on a bass guitar. Trucking the capacity for anything lower is an unnecessary expanse that will quickly put you out of business.

MoD,

... There's a number of PA and SR cabs having an F3 bass "cutoff" in the 50-80 hz range. JBL has/had a number, Peavey also, as well as others. ...

Richard