 Yamaha GQ-1031 1/3 octave Graphic Equalizer EQ US $59.99 
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 Ashley GQX Series Model 3101 Third Octave Graphic Equalizer FAST SAME DAY SHIP! US $259.99
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 PylePro PPEQ215 Dual Channel 15 Band 2/3 Octave Graphic Equalizer US $82.21
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 Alesis M-EQ230 Dual Channel 1/3 Octave 30 Band Stereo Graphic Equalizer US $59.00
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 ART HD 231 GRAPHIC EQUALIZER DUAL 31 BAND 1/3 OCTAVE US $79.99
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 YAMAHA Q2031A 31 BAND DUAL CHANNEL 2 2CH RACK MOUNT OCTAVE GRAPHIC EQUALIZER EQ US $126.90
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 Electro Voice EQ-131 1/3 Octave Graphic Equalizer US $120.00
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 Peavey RTD-31 Equalizer 31 band 1/3 Octave Graphic Equalizer US $47.00
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 Audioarts 2700, 2700B , Third Octave Graphic Equalizer Rack mountable US $10.00
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 Neptune Electronics 2710 Vintage 1/3 Octave Graphic EQ's Two-For-One! US $380.00
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 Ashly GQ131 PRO 1/3 Octave 31 Band Graphic EQ US $31.00
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 Samson E62 1/3 Octave Dual 31-band Graphic Equalizer US $25.00
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 JBL Urei 5547A 5547 A 1/3 Octave Graphic Equalizer EQ US $224.99
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 Audioarts 2700, Third Octave Graphic Equalizer, Eq, Vintage Rack US $405.00
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 DBX 3231L Dual 1/3 Octave 2 x 31 Band Graphic EQ Equalizer Rack Mount NR #3 US $299.99
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 DBX 3231L Dual 1/3 Octave 2 x 31 Band Graphic EQ Equalizer Rack Mount NR #2 US $304.99
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 Klark Teknik DN360 Dual Channel 1/3 Octave Graphic Equalizer ** Very Good Cond** US $454.00
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 Klark Teknik DN360 Dual Channel 1/3 Octave Graphic Equalizer US $700.00
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 Peavey EQ 31 -1/3 Octave Graphic EQ rack mount US $59.99
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 Peavey EQ 31, 1/3 Octave Graphic Equalizer,Vintage Rack US $315.00
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 TOA E-1231 1000 Series Graphic Equalizer 13 OCTAVE US $106.25
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 Behringer FBQ 3102 Ultragraph Pro stereo 1/3 octave graphic equaliser - Nice! US $139.00
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 WHITE 1/3 OCTAVE 4004 GRAPHIC EQUALIZER BROCHURE US $15.00
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 WHITE 1/3 OCTAVE 4500 GRAPHIC EQUALIZER 4 PAGE BROCHURE US $15.00
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 Audio Centron Eclipse GE-131 1/3 Octave Equalizer 31 Band Graphic EQ ge131 US $79.99
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 Neptune, NEI 2711, 27 Band, 1/3 Octave Graphic Equalizer, Eq, Vintage Rack US $405.00
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 Klark Teknik DN360 Dual Channel 1/3 Octave Graphic Equalizer | GREAT BUY US $599.00
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 Rane Graphic Equalizer GE27 GE 27 1/3 Octave 2 U Rack Mount US $124.99
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 Rane ME60S ME 60 60S Dual 30 Band 1/3 Octave Graphic Equalizer Stereo 2U PRO NEW US $599.00
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 Yamaha Q2031B Graphic Equalizer, Dual 1/3 Octave US $629.95
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 STEREO-GRAPHIC OCTAVE EQUALIZER PROFESSIONAL SOUNDCRAFTSMEN US $70.00
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 PYLE Dual Channel 20 band Octave Graphic Equ PPEQ200 US $125.00
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 Rane DEQ 60L 1/3-Octave Graphic Equalizer US $863.59
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 RBPPEQ Dual Ch 31 Band 1/3 Octave Graphic Equalizer US $149.99
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 Dual 31-Band,1/3 Octave Graphic EQ (IRP TEQ #DG-4023) US $299.00
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 ARX EQ60 Constant Q 1/3 Octave Graphic Equalizer, (Australian manufactured) US $350.00
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 MXR 171 Dual 2/3 Octave Graphic Equalizer, Vintage Rack US $265.50
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 MXR 170 Dual Octave Graphic Equalizer, Vintage Rack US $247.50
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 Samson E30, 2/3 Octave Stereo 15 Band Graphic Equalizer, Rack US $225.00
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 YAMAHA Q2031B 2CH 31-BAND 1/3 OCTAVE GRAPHIC EQUALIZER US $275.00
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 MXR 172, 1/3 Octave EQ, Graphic Eq, Vintage 80s Rack US $265.50
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 Samson E31i 1/3 Octave Graphic EQ US $50.00
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 Klark Teknik DN360B Dual Channel 1/3 Octave Graphic Equalizer US $1,549.00
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 Klark Teknik DN360 Dual channel 30-Band 1/3 Octave Graphic Equalizer US $1,399.00
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 Phonic i7600 Dual 30-Band 1/3 Octave Digital Graphic Equalizer with RTA US $299.00
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 SAMSON E30i 2/3 OCTAVE STEREO 15-BAND GRAPHIC EQUALIZER US $155.00
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 ART XL231 Dual 31-Band, 1/3 Octave, Graphic EQ US $369.00
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 Audio Centron Eclipse GE-131, 1/3 Octave Equalizer, 31 Band Graphic EQ, Vintage US $265.50
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 LA Audio EQ231G Dual 31 Band 1/3 Octave Graphic Equalizer US $619.99
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 Peavey RTD31 RTD 31 31-Band 1/3 Octave Graphic Equalizer Contractor EQ Processor US $149.95
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 Altec 1650, 1/3 Octave Center Frequency-Hz, 28 Band Graphic Equalizer, Vintage US $445.50
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 RANE ME 60 2-CHANNEL 1/3 OCTAVE GRAPHIC EQUALIZER US $179.00
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 Ibanez GE3101 31-Band 1/3 Octave Graphic EQ Equalizer Rack Mount Unit FREE SHIP! US $64.95
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 Peavey EQ 31, 1/3 Octave Graphic Equalizer, Rack Gear Unit FREE SHIPPING! US $334.95
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 Rane ME30S 1/3 Octave Graphic Equalizer US $369.00
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 Rane ME15S 2/3 Octave Graphic Equalizer US $379.00
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 ART XL231 Dual 31-Band, 1/3 Octave, Graphic EQ Standard US $369.00
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Octave Graphic
Next Gen Graphics Engine - The Octave Engine : DigInfo
Digital Room Correction with Digital Signal Processor (DSP)
The Problem
Mother nature gave us a lot of gifts, but a perfect acoustic space wasn't one of them!
Put it simply, acoustic theories are very complex to analyze, model and unless your room was designed by a world famous acoustician, it will always be an uphill battle against the laws of phisics. While a certain amount of audio filtering; also called room correction can help to perfect the audio performance, achieving flat frequency response by boosting the signal at certain frequencies will only solve the issue if problems are not time dependant (see more below). Of course, quality of your loudspeakers, amplifiers and any other devices on the audio chain matters, but in the end acoustic theories trump. Following this little disclaimer, let's have a look at what DSP board can do for you.
Let’s take as an example the Hifi system of a living room illustrated in the below picture.
Many elements will affect quality of the audio system, such as:
• The window that won’t absorb acoustic energy and will most likely reflect lots of high frequency energy from the left speaker
• The imperfect free field frequency response of your loudspeaker system
• The asymmetrical room layout which will affect the stereo field
• Or simply the listener’s position by the sofa. So close to the back wall, he will most likely experience more low frequency than he should from the so-called standing waves. All together, the end result is an imperfect acoustic space where even the best Hifi audio system will hardly produce a flat frequency response.
How MiniDSP kits can help?
So besides taking down walls, moving your sofa around the room 5 times or considering changing the color of your speaker cable, there are few tricks which can help you improve the overall system performance. Digital audio processors like our MiniDSP Kit are one of them. Thanks to their configuration flexibility, they provide a low cost option to configure audio filters, equalizers and signal monitoring from a simple software interface. However note that there is a limit to how much digital signal processing can solve acoustic issues. In particular, equalization will only solve amplitude related issues.While room modes and other comb filtering (cancelations of waves) issues will require either time alignement or acoustic treatment.
What miniDSP can do, is provide you with a set of filters to easily improve the performance of your speaker system:
• Graphic equalizer: This bank of filters will increase or decrease the signal at a specific frequency. Depending of the MiniDSP firmware configuration, you may have 31 bands (also called 1/3 octave) or 15 bands (2/3 octave) available. By boosting/dampening the signal at certain frequencies, speaker equalization is the most common tool for system tuning
• Parametric equalizer: Similar to the graphic equalizer, but this time with only a limited number of equalization bands that can easily be configured to better fit the needs of the application.
• Delay: In order for loudspeakers to produce constructive wave front and prevent as much comb-filtering effect as possible, time alignement of different loudspeaker are typically required. The delay blocks will also come handy in digital crossover applications.
So to summarize this application note, flat frequency response of a system will not happen by the magic of a DSP (no matter which brand it is). However, what our boards can do is help you improve the speaker equalization by boosting/dampening few specific frequencies your enclosure + driver combo may not be able to reproduce.
Our kits are also the perfect fit when it comes to digital crossovers. With their small form factor, one can easily place the board inside the enclosure of active loudspeakers. Hope this makes sense and send us an email if you have some comments to add.
About the Author
Tony is the co-founder of DSP4YOU and miniDSP, two companies dedicated to digital signal processing for audio applications. Besides his passion for audio, electronics and music, Tony loves traveling through out Asia Pacific, discovering one culture at a time what the world has to offer.
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