Commercial bass cabs loaded with twelves.

Comparisons of the different models with each other and commercial cabs.
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Bill Fitzmaurice
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Commercial bass cabs loaded with twelves.

#1 Post by Bill Fitzmaurice »

These charts show what you can expect from a commercial bass cab loaded with twelves and a tweeter. They were prepared utilizing driver manufacturer data sheets.

This is a 1x12 combo, net volume 1.5 cu ft., ported, loaded with an Eminence Alpha 12. This driver is used in many OEM applications.


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Note the weak lower midrange response from 200 to 1kHz, caused by a magnet structure too weak for the mass of the cone. Also note how quickly response falls below 100Hz, the result of a cabinet that’s too small. There’s not a lot to recommend here, but that’s what you get for the price of a 1x12 combo.

At the other end of the scale is this 'boutique' 1x12, 1.5 cubic feet (net), loaded with a DeltaPro 12 and tweeter:


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The response is very smooth, with adequate sensitivity. It gives about as good a level of performance as you can get from such a small box. OTOH, the same driver in a well designed cab not that much larger will give performance equal to two of these.

This is a 2cu ft (net) 1x12 cab loaded with a premium driver, the Eminence Deltalite II 2512.


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One manufacturer of a cabinet identical in make up to this claims 98dB sensitivity, -3dB at 45Hz. The 98dB sensitivity is accurate, but the -3dB frequency is actually 55Hz. In the world of electric bass cabs those are relatively honest claims. From the equivalent driver/cabinet another manufacturer claims 100dB at 39Hz, -6dB at 36Hz; the actual figures are 90dB at 39Hz, -12dB at 36Hz. Caveat Emptor.

This chart shows two 2512s in a 3.5 cu ft cab:

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Compared to the 1x12 above it could have about 3dB added sensitivity throughout the range of the woofers, but below 200Hz it comes up short. That’s because the cabinet isn’t twice the volume of the 1x12. Why? This particular manufacturer sized his cabs to match the width of his amp heads. In fact, most manufacturers build their cabs more with an eye to how they look than how they sound. In a ported box 2512s work best with a cabinet volume of about 4.5 cu ft (net) each, but no manufacturer would ever build a box that size and load it with one twelve, because ‘it wouldn’t look right’. A common assumption is that one gets the best possible performance by filling a cab with as many drivers as can be shoe-horned in. That assumption is incorrect.

Cabinet manufacturers love to use high wattage ratings to push sales, but wattage alone doesn’t mean much. This chart shows a pair of moderately priced Eminence Delta 12s, loaded in a 5 cu ft cabinet:


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Note the very flat response through the midbass. A cab built to these specs would sound very good, without being either overly large or expensive. In the showroom you’d probably be very well impressed, especially with the cabs 800 watt rating. However, the driver xmax is only 2.4mm, so a pair would only take about 100 watts before distorting on the low notes. A pair of 2512s are rated for 500 watts, but xmax is 4.9mm, so a pair would be able to handle around 400 watts without complaint.

Does size matter? It does when it comes to bass response. This chart addresses both cabinet size and how a driver's raw SPL rating can be very misleading.


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The blue and black traces are a 93dB rated Eminence BP102 and 97dB rated Beta 12 loaded compact (2.5 cu ft net) 2x12. The Beta (black trace)does have a major sensitivity advantage, but only above 100 Hz. Below 100 Hz the supposedly less sensitive BP102 (blue trace) is on average 3dB higher in sensitivity, which equates to a doubling of amp power. This shows why merely quoting a driver sensitivity tells you very little about how a cabinet loaded with that driver will perform.

As to size, neither the Beta 12 or BP102 work to anywhere near their potential in 1.25 cu ft per driver. The red trace shows what happens when two Beta 12s are loaded in a 6.5 cu ft box. The 9dB sensitivity increase at 50 Hz is the equivalent of increasing amp power by a factor of 8. In fact, below 80Hz a pair of Beta 12s loaded into a 2.5 cu ft cab have less sensitivity than one.

What does $1800 get you these days? On the one hand, a pretty good cab. On the other, maybe not exactly what you may be led to believe. Here is a pair of premium Beyma 112NdW twelves, in a 5 cubic foot (net) cab. The 95dB average sensitivity with 38Hz f3 is quite good from a box of this size.
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On the other hand, Caveat Emptor applies. One manufacturer claims from this setup 101dB sensitivity at 28Hz, when the actual is 87dB. The Dickens, you say!

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