Doug_M_Fraser
Grip
- Joined
- Jan 31, 2003
- Messages
- 23
I have posted this here because I believe that the subject of EQ can be treated as an advanced topic if persued with rigour. I have been very interested in EQing my set up for some time now. I have lurked here for several years and occasionally posted. Now I would like to give back and present some activities and views on EQing.
My sub experience…..
I have a Stryke 15.2 sub driven with a Crown K2 amp. This link http://members.cox.net/frankcarter/T...e Sub Data.htm documents the Tom Nousaine’s test results for the Power 15.
Before EQing the sub, it sounded real bad. I purchased Doug Plumb's ETF http://www.etfacoustic.com/ software, swept my room and found I had a 30dB resonate peak at 38 Hz (plus a bunch of other anomalies). Thanks to Sonnie Parker and his BFD set up guide http://www.snapbug.ws/bfd.htm and Wayne A. Pflughaupt for his advice and guidance and many posting by Ken Bruce, I managed to tame the in room response and add a house curve. So all is now good in Sub Land.
With respect to EQing a sub here are some idea's that I think are important and haven't been discussed in detail on this forum (to the best of my knowledge) . The Tag Mclaren Audio site http://www.tagmclarenaudio.com has a great tutorial on using ETF to EQ a room. Go to the Club area. You need to log in, however, they don’t seem to send Spam. Go to the TMREQ project and look at “Room Resonances their Visualization in Measurement Systems”. If you take the time to follow through the diagrams, what is apparent is that one needs a very narrow bandwidth EQ to remove room resonances. The BFD is such a device! It is very clear that you need to accurately pick the centre frequency dead on. In addition, the bandwidth of the filter is very critical too. This needs to be done using test equipment and luckily, ETF is available in a demo version for free. Therefore I recommend that you are serious (or should I say anal - like me) that you reveiw the tutorial and understand why it is important to have the correct centre frequency and bandwidth.
As side note, the Tag tutorial refered to above presents an interesting procedure as to how to EQ your Sub. They suggest you should measure the response curve of your crossover and use it as a target curve for your subs in room response. This means injecting the ETF test signal before the crossover. Something that is easliy done if you use the crossover in your SSP (Surround Sound Processor). I originaly used the techniqe as described by Sonnie in his document, however I plan to give the Tag technique a try in the future. The beauty of the BFD is that you can save differant EQ curves for comparison.
It seems that in most cases, even a 31-band graphic EQ would not be up to the task as it has fixed centre frequencies and bandwidth. So my advice is get the BFD. It is inexpensive (about $120 more or less) and it works!
Now on to the other speakers….
A local audio store here in Vancouver, BC called Speaker City http://www.speakercity.ca/index3.html (not to be confused with Speaker City USA) had built some speakers using drivers from another local Vancouver company AVI http://www.avisound.com/ . I auditioned the speakers and fell in love with them. Their mid's and highs sounded very close to my B&W 802’s. Now Speaker City seems to have a soft spot in their heart for DIY guys. They sold me the drivers, crossovers and provided plans. I ended up building 7 speakers including dipole surrounds. Speaker City even redesigned the crossover to compensate for the two-tweeter design (for the dipole design) instead of one tweeter.
Now bitten by the speaker building bug I started to notice that some crossover designs try to equalize out bumps in the combined response curve of a speaker. If you go to here http://www.linkwitzlab.com/reference_earphones.htm you can see that Siegfried uses passive components to equalize earphones. In addition Siegfried invented the Linkwitz Transform circuit to boost the low frequencies for subs in a sealed enclosue. http://www.linkwitzlab.com/filters.htm#9 This is simply an application of very specific equalization.
This got me thinking, why not get a good parametric EQ and have a go at my other speakers. So at this point I have purchased two Behringer DEQ 2496 EQ’s http://www.zzounds.com/item--BEHDEQ2496. This is quite the piece of gear. First of all, it samples at 96Khz with 24 bit words. The DEQ2496's provide the following functionality, all done digitally: stereo 12 band parametric EQ’s, stereo 1/3 octave graphic EQ’s, a real time audio analyzer, auto configuration of the graphic EQ by using a calibrated mic http://www.zzounds.com/item--BEHECM8000 and a plethora of other functionality that I will never use.
So with ETF and a pair of DEQ2496's I now have the ability to correct for very narrow band anomalies as well as wide band tone shaping for my 3 front channels. I only intend to EQ the three front channels, as my receiver, an Integra 9.1, does not provide access to the signal between the internal pre amp and power amp for the surround or back channels.
We are in the process of redoing our family room right now so I won’t get to the task for at least a month or so. When I do, I will post results, experience etc.
I welcome your thoughts on the above or topics associated with EQ subs, speakers etc.
Regards,
Doug
My sub experience…..
I have a Stryke 15.2 sub driven with a Crown K2 amp. This link http://members.cox.net/frankcarter/T...e Sub Data.htm documents the Tom Nousaine’s test results for the Power 15.
Before EQing the sub, it sounded real bad. I purchased Doug Plumb's ETF http://www.etfacoustic.com/ software, swept my room and found I had a 30dB resonate peak at 38 Hz (plus a bunch of other anomalies). Thanks to Sonnie Parker and his BFD set up guide http://www.snapbug.ws/bfd.htm and Wayne A. Pflughaupt for his advice and guidance and many posting by Ken Bruce, I managed to tame the in room response and add a house curve. So all is now good in Sub Land.
With respect to EQing a sub here are some idea's that I think are important and haven't been discussed in detail on this forum (to the best of my knowledge) . The Tag Mclaren Audio site http://www.tagmclarenaudio.com has a great tutorial on using ETF to EQ a room. Go to the Club area. You need to log in, however, they don’t seem to send Spam. Go to the TMREQ project and look at “Room Resonances their Visualization in Measurement Systems”. If you take the time to follow through the diagrams, what is apparent is that one needs a very narrow bandwidth EQ to remove room resonances. The BFD is such a device! It is very clear that you need to accurately pick the centre frequency dead on. In addition, the bandwidth of the filter is very critical too. This needs to be done using test equipment and luckily, ETF is available in a demo version for free. Therefore I recommend that you are serious (or should I say anal - like me) that you reveiw the tutorial and understand why it is important to have the correct centre frequency and bandwidth.
As side note, the Tag tutorial refered to above presents an interesting procedure as to how to EQ your Sub. They suggest you should measure the response curve of your crossover and use it as a target curve for your subs in room response. This means injecting the ETF test signal before the crossover. Something that is easliy done if you use the crossover in your SSP (Surround Sound Processor). I originaly used the techniqe as described by Sonnie in his document, however I plan to give the Tag technique a try in the future. The beauty of the BFD is that you can save differant EQ curves for comparison.
It seems that in most cases, even a 31-band graphic EQ would not be up to the task as it has fixed centre frequencies and bandwidth. So my advice is get the BFD. It is inexpensive (about $120 more or less) and it works!
Now on to the other speakers….
A local audio store here in Vancouver, BC called Speaker City http://www.speakercity.ca/index3.html (not to be confused with Speaker City USA) had built some speakers using drivers from another local Vancouver company AVI http://www.avisound.com/ . I auditioned the speakers and fell in love with them. Their mid's and highs sounded very close to my B&W 802’s. Now Speaker City seems to have a soft spot in their heart for DIY guys. They sold me the drivers, crossovers and provided plans. I ended up building 7 speakers including dipole surrounds. Speaker City even redesigned the crossover to compensate for the two-tweeter design (for the dipole design) instead of one tweeter.
Now bitten by the speaker building bug I started to notice that some crossover designs try to equalize out bumps in the combined response curve of a speaker. If you go to here http://www.linkwitzlab.com/reference_earphones.htm you can see that Siegfried uses passive components to equalize earphones. In addition Siegfried invented the Linkwitz Transform circuit to boost the low frequencies for subs in a sealed enclosue. http://www.linkwitzlab.com/filters.htm#9 This is simply an application of very specific equalization.
This got me thinking, why not get a good parametric EQ and have a go at my other speakers. So at this point I have purchased two Behringer DEQ 2496 EQ’s http://www.zzounds.com/item--BEHDEQ2496. This is quite the piece of gear. First of all, it samples at 96Khz with 24 bit words. The DEQ2496's provide the following functionality, all done digitally: stereo 12 band parametric EQ’s, stereo 1/3 octave graphic EQ’s, a real time audio analyzer, auto configuration of the graphic EQ by using a calibrated mic http://www.zzounds.com/item--BEHECM8000 and a plethora of other functionality that I will never use.
So with ETF and a pair of DEQ2496's I now have the ability to correct for very narrow band anomalies as well as wide band tone shaping for my 3 front channels. I only intend to EQ the three front channels, as my receiver, an Integra 9.1, does not provide access to the signal between the internal pre amp and power amp for the surround or back channels.
We are in the process of redoing our family room right now so I won’t get to the task for at least a month or so. When I do, I will post results, experience etc.
I welcome your thoughts on the above or topics associated with EQ subs, speakers etc.
Regards,
Doug