When building speakers how do you calculate volume?

Question

I am planning on building a speaker cabinate will two Eminence Kappa 12a speakers and one RCF 850 titanium driver. The speaks for the Eminence speaker call for a volume of 112 liters. Since I have two speakers does the volume need to double? Do Drivers also require a specific amount of volume. I can;t find a spec volume amount for the driver.

Answer 1

I have provided links to all of the driver datasheets you need to begin the loudspeaker enclosure design and construction process. (Note: when feasible it is ALWAYS much better to design loudspeaker enclosures using Thiele-Small parameters obtained from first-hand measurements, after a rigorous driver break-in period, rather than relying upon those provided by the driver manufacturer.)



Using high EBP drivers such as the Eminence Kappa 12 you will obtain the best results by constructing a “vented box” enclosure designed for a maximally-flat Butterworth—or near maximally-flat—fourth-order alignment (assuming an enclosure Q, i.e., Q.sub.L, equal to 7.) You can derive the necessary loudspeaker enclosure design parameters using: (a) tables from one of the popular loudspeaker design publications, such as the highly-recommended Loudspeaker Design Cookbook by Vance Dickason; (b) one of the online loudspeaker enclosure calculators; or (c) purchase and/or download loudspeaker design software. In addition to obtaining a copy of the Loudspeaker Design Cookbook, I highly recommend that you download one of the free loudspeaker design programs (such as WinISD Pro) to which I’ve provided links* in the resources listed below. You may also try using the Eminence Designer Loudspeaker Enclosure Design Program though you may get better results using one of the other software applications. Using procedures (b) or (c) simply plug in the Thiele-Small parameters obtained from the manufacturer’s spec sheet (or better yet from your own measurements) into the enclosure design calculator or software as necessary.



I recommend that you allow multiple Eminence Kappa 12 drivers to share a single internal enclosure volume. If you’re using tables then multiply the calculated internal enclosure volume (V.sub.B) for a single Kappa 12 driver by the total number of Kappa 12 drivers sharing the same enclosure volume, i.e., the enclosure volume for two Eminence Kappa 12 drivers will be double that of a single driver. (Note: 112.1 liters is NOT the recommended internal enclosure volume for a single Kappa 12 driver however it is used to calculate the proper internal enclosure volume.)



Depending on how much internal bracing and sound absorption you use you should increase the total calculated internal enclosure volume (V.sub.B) by approximately five to ten percent (5-10%) in order to compensate for any reduction in volume due to internal bracing and components as well as an added margin of design safety. It’s important to note that when starting with an over-sized enclosure it is much easier to optimize the internal volume of the ‘box’ (V.sub.B) by gluing carefully fabricated blocks of MDF, plywood, or rigid closed-cell foam material inside the enclosure in order to (incrementally) reduce the internal volume. Consequently this allows you to fine tune the enclosure resonant frequency whereas an undersized enclosure would make fine tuning extremely difficult. However if you build a prototype from MDF as I have suggested below then you can neglect over-sizing the internal box volume for the final plywood loudspeaker enclosures.



The following are a few more loudspeaker design and construction notes for your consideration.



If you’re assembling loudspeakers for (portable) pro sound use I highly recommend using the industry standard 3/4-inch (19mm) or 18mm high-grade, void-free, 13-ply, marine or Baltic birch plywood to construct your loudspeaker enclosures. If need be you can prototype a single loudspeaker using medium density fiberboard (MDF) before proceeding to the more expensive plywood material. Do not skimp on internal bracing, which should be fabricated from no less than 1/2-inch (13mm) Baltic birch or marine plywood. Braces are not intended to be partitions and therefore should contain ample cut-outs to allow air movement; dado and glue all bracing in place. You should have at least one wall-to-wall brace between each driver in your enclosure. (Please see the resources listed below for a link to an example of internal, wall-to-wall bracing.)



When choosing vents I recommend using individual vents no smaller than 4 inches in diameter with flares at both ends of the vent duct. (Please see the resources below for more info.)



IF you intended to use flat-head sheet metal or woodscrews, IN ADDITION to glue, then I recommend carefully countersinking the holes (using a special countersink bit with adjustable pilot and depth stop) for each s***w in order to recess each s***w head. This allows you to hide the screws using tight-fitting wood plugs glued in place over each recessed s***w head, which can be cut (if necessary) and sanded flush with the surrounding surface.



Using the appropriate low- or zero-VOC adhesive¹ cover the majority of the largest surface areas inside your enclosure with 1-inch to 1-1/2-inch (38mm) thick (flat) flexible, open-cell acoustical foam. If you wish you can cover (the acoustical foam and) all other remaining exposed interior surfaces with a roughly 1-1/2-inch to 2-inch (38mm to 50mm) thick layer of polyester fiber batting. ¹(If all else fails, in a pinch you can use 3M’s commonly available Super 77 or FoamFast 74 Spray Adhesive as an alternative.)



One final note: I do not recommend that you crossover the 12-inch Eminence Kappa 12 driver to the RCF N850 compression driver any higher than 1 kHz; and if you will be using a good quality, high performance (active) crossover, preferably no higher 800 Hz.



By the way, the Eminence Kappa 12 drivers fall a little short for a low-frequency driver and you shouldn’t expect high performance from such units particularly with respect to low-frequency output below roughly 80 Hz.



############ RESOURCES ############



Eminence Kappa 12

http://www.thielesmall.com/include/detai...



Eminence Kappa-12A American Standard Series

http://www.eminence.com/pdf/kappa-12a.pd...

Eminence Resources and Parameters

http://www.eminence.com/resources/params...

Eminence Designer Loudspeaker Enclosure Design Program

http://www.eminence.com/resources/design...

Eminence Kappa 12 Cabinet

http://www.eminence.com/pdf/cab-kappa-12...



RCF Audio N850 2-inch (exit throat) Compression Driver

http://www.rcfaudio.com/VediMacro.phtml/...



RCF Audio HF64 60°×40° Constant Directivity Horn

http://www.rcfaudio.com/vediMacro.phtml/...

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*Need help making my own speakers?

http://answers.yahoo.com/question/index?...

Does anybody know the meathod to work out the porting for my bass cabenet? [sic]

http://answers.yahoo.com/question/index?...

What is the best enclosure for sub woofer speakers?

http://answers.yahoo.com/question/index?...

Speaker assemble?

http://answers.yahoo.com/question/index?...

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Loudspeaker Design Cookbook

http://www.audioxpress.com/bksprods/prod...



Free Online Loudspeaker Calculators

http://www.madisound.com/services/hifisp...



Steve Ekblad’s Free Audio Software and On-Line Enclosure Design

http://www.audiogrid.com/audio/



JPO’s SpeakerBuilding LinkList

http://web.telia.com/~u87124019/software...



HiFi Speaker Design © mhSoft 2008

http://www.mhsoft.nl/spk_calc.asp



Vented Ported Subwoofer Box Equations Formulas Design Calculator

http://www.ajdesigner.com/phpsubwooferve...

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Loudspeaker Compliance Scaling

http://sound.westhost.com/articles/cscal...



JBL Professional Enclosure Guide

http://www.jblpro.com/pub/manuals/enclgd...



EAW Professional Audio Technical Paper: How It’s Made

http://www.eaw.com/info/EAW/Technical_Pa...



Volume Filling a Reflex Box

http://sound.westhost.com/articles/boxst...



DIY loudspeakers series - Part III: Get Stuffed!

http://www.tnt-audio.com/clinica/speaker...



Loudspeaker Construction

http://www.silcom.com/~aludwig/Loudspeak...



Loudspeaker Builder DIY - (Speaker Enclosures)

http://www.members.shaw.ca/LoudSpeakerBu...



Article containing good examples of shelf-style internal bracing

http://www.hilberink.nl/codehans/tannoy1...



######## ADDITIONAL RESOURCES ########



Audio Engineering Society Sound Path Labs

First Basic Audio Workshop 1992

http://www.drewdaniels.com/BINDER.pdf



JBL Professional Technical Library

http://www.jblpro.com/pages/tech_lib.htm  

JBL Professional Sound System Design Manual - 1999 Edition (Part 1)

http://www.jblpro.com/pub/manuals/pssdm_...

JBL Professional Sound System Design Manual - 1999 Edition (Part 2)

http://www.jblpro.com/pub/manuals/pssdm_...



Davis, Gary and Ralph Jones

Sound Reinforcement Handbook, 2nd Edition

ISBN-13: 978-0881889000

ISBN-10: 0881889008

http://www.yamaha.com/yamahavgn/CDA/Cont...



Eiche, Jon F

Guide to Sound Systems for Worship

ISBN-13: 978-0793500291

ISBN-10: 079350029X

http://www.yamaha.com/yamahavgn/CDA/Cont...