Since I already have a 4 x 12" Marshall Cab. With reflex units the bass is extended and is more like that quoted, but it drops off rapidly by some 24dB per octave below resonance. As it is common practice to specify a response some 10Hz below the quoted resonance, the specified bass response is thus likely to be optimistic.
Is always higher with sealed enclosures than the quoted free air resonance. However that frequency is raised by the effect of the air in the enclosure, and small enclosures raise it more than large ones. It is governed by the resonant frequency of the cone, below which the response falls off by 12dB per octave for sealed enclosures.
Most manufactures are quite optimistic with their lower level. Ideally the speaker should go down to 41Hz, if possible. The frequency range is 41Hz (E3) to 261 Hz (middle C), so speakers producing deep bass are desirable. The requirements of Bass is much different to that of other speaker design. I had previously built some speaker cabs a few years ago but then I thought that any old box would do!! Yes, I was proved wrong.this time I wanted to do it the right way! So after reviewing what was on offer I then decided to build my own cabinet. I can only guess that 30hz must be a -12db point!! Don't always trust what the manufacture claims!! Overall, the current market offerings were expensive and slightly over-rated.
Peavey were claiming a low Bass response from 30hz for there 15" Cab's!! However since their drivers have a Fs of around 40Hz. First they were all very expensive, some more than others. I initially looked at what Peavey, Trace Elliot, Ampeg and Gallien-Krieger had to offer. The one thing I've learned, is that designing an enclosure, involves a lot of different audio trade-off and compromises. Once you are happy with what you know and want, then you're ready to build.
So how do you go about it? Easy.first of all work out exactly what do you want to from your cab? Low bass roll off or extended bass with a sharp roll off? A large or small enclosure? Vented or sealed Enclosure? What size or how many driver/s? The particular type of driver characteristics do you require? What Amp you have? What can you afford? Once you know exactly what YOU want, then get out there and research the different designs and building techniques, there is a mountain of information on the net, books etc. So what's out on the A lot of basics which can be applied to this sort of design, but there was nothing really specific for building a bass or guitar speaker enclosures.
So when I go about making my next speaker cabinet, I'll be a lot wiser. I decided to place my experiences on the I've tried to keep things as simple as possible so even a complete novice could have an attempt at building one! I also made mistakes building this cabinet, but I've learned from them. If you are any way handy with a saw and screwdriver, you'll go a long way. Therefore, I could design & build an enclosure to my own spec's and finish it the way I want! If you design and build the enclosure correctly, you get the Cab of your dreams, for half the cost!! Buying a decent off-the-shelf Bass Cab is not cheap. So I had decided why not go and build one myself!
I had looked around at the commercial offerings and I wasn't happy with what I saw especially with the prices. Why go to all that trouble? I've been asked.especially by Susi, who having fantastic patience put up with all the hassle, whirling & drilling noises and endless Not? Hmmm.not a very good answer, however, the main reason is I wanted a smaller, lighter & more manageable cabinet than my Marshall 4 x 12" stack. Layout, Cutting & Fitting the Front Baffle & Rear panel.See also my other project, a 2 x12" Sealed Bass cabinet. Designing & buiding a Bass Guitar loudspeaker Cabinet