ACME sound Low B-1 Owner's Manual
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Owners Notes Low B-2 and Low B-4 Systems8on their sides, with the midranges and tweeters oriented on a common vertical axis. Acoustically, thisorientation offers a better “line source” than stacking the two boxes upright or side-by-side.Experiment.Placement: Low B-1At first glance, the Low B-1 looks a little strange. As was mentioned above, the speaker uses a Fender-type strap handle. The port is apparently located on the top, next to the handle. Unusual.In fact, however, the port and the handle are located on the side of the speaker. They are placed on acommon surface to discourage the user from stacking another speaker (or anything else) over the port,thereby ruining the operation of the port, and placing the woofer at great risk. As was mentioned in thesection on placement of the B-2, blocking the port(s) greatly reduces system power-handling, and is to beavoided at all costs.As a consequence, the disadvantage of this type of handle for use on the Low B-2, limiting stackingoptions, is a necessity on this smaller speaker, and allows the use of this excellent handle on the B-1.Place the speaker with the midrange and the tweeter toward the top.The port and handle will be on the side, correctly, and the top of the box will provide an open surface forplacement of your amplifier, or for stacking a second Low B-1.CablesAs a design goal, internal systemresistance has been kept to aminimum. To maintain the samelevel of electrical integrity, short,heavy gauge cables are best. Don'trun out and spend a fortunehowever, unless you're certain thatwhat you have is inadequate. Irecommend a cable of under .3Ohms, and the larger the cable thebetter.StandsSome customers have successfullyused the Low B-2 systems as PAspeakers. This has led to the idea ofusing the units elevated on speakerstands. Be warned: There are onlytwo small places on the cabinetwhere a recessed receptacle can bemounted, and you don’t knowwhere they are. To cut holesanywhere else in the box will doirreparable harm to the enclosure.This is because of the orientation ofthe special bracing that is used tostress the enclosure. DO NOT CUTHOLES IN THE ENCLOSURES FOR THEPURPOSE OF INSERTING SPEAKERSTANDS WITHOUT CONSULTINGWITH US FIRST! If you need to dothis, please call before you destroyPort Placement: Front, Rear, or Side?Bass players seem to enjoy discussing the merits of front or rear placement of ports.Based on their experiences, many players and manufacturers alike are convinced thatfront placement has distinct advantages over rear placement, or vice-versa.When asked to justify their opinions, these partisans will invariably refer to vagueimpressions and gut feelings. They will never talk about wave propagation orHelmholtz resonation. In fact, a bass-reflex enclosure, at the frequencies where theport contributes to the system’s output, is a pressure device, as opposed to a wavedevice. So the interaction of the enclosure and the port, and the port's position withrespect to the woofer, itself, are unaffected by any directional activity. Direction isutterly unimportant. By way of illustration, examine another pressure -related model,a balloon. As you inflate a balloon, does it expand on one direction only, or in alldirections at once?Only after a port’s output leaves the cabinet, and enters the environment, does itassume the characteristics of a wave, one of which is direction of propagation.Direction does assume importance when speaking of waves. Only, however, atfrequencies where the size of the source is large compared to the wavelength underconsideration. The highest frequencies at which the port in our Low-B systemscontribute to system output have wavelengths of 14 feet or so. The speakers areobviously quite small compared to these wavelengths, and the port output isomnidirectional. Again, port placement is irrelevant to system performance.Why does the B-2 have ports in the back? Because that’s where they fit. Why does theB-4 have its third port in the front? Same reason.The B-1 system could have been correctly tuned with a shorter, smaller diameter portlocated in either the front or the back, if location mattered. But it doesn’t . Thedrawback would have been that at higher power levels, excessive port friction wouldhave resulted in diminished power handling capability. This larger diameter, longerport fits when installed on the side of the box. Plain and simple.Tell your friends that the reason your B-1 system sounds so good is that thetremendous innovation of a side-mounted port results in some type of magicalquantum-leap in performance. In fact, the truth is much less exciting: a high-qualitywoofer in a solid and correctly-tuned enclosure. Feel free to let other people lose sleepover where their ports are located. Now you know the truth. |
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