equalizers and crossovers

[jmschnur]

I have a very difficult postioning problem for one of my Clarity'sin my HT 7.1 video room and have resorted to an equalizer to help. It is an old SoundCraftsman. While most of my 25 years old equipment still works fine, the equalizer is a bit noisy. However it did fix a resopnance a 125 hz that I could not solve by room treatment or placment. The results are an improvement. I use a Lexicon DC-1 as the preamp and have the xover for the sub at 80. Before I buy a new one equalizer, I want to get some feed back.

I am intersted to hear about forum members use of equalizers and or crossovers in their system. I would not expect these to be needed for good listeing rooms and the higher end of Martin Logan's product line-but I wonder if some of you have used either or both. If so, what has been your experience with them, and what have you used?

Joel

 

[JonFo]

....

I am intersted to hear about forum members use of equalizers and or crossovers in their system. I would not expect these to be needed for good listeing rooms and the higher end of Martin Logan's product line-but I wonder if some of you have used either or both. If so, what has been your experience with them, and what have you used?

Joel

Hi Joel,

Around here, I’m probably the most extreme in terms of use of EQ and external crossovers, so I’ll chime in. I’m sure you’ll hear a counterpoint or two as well

Fixing a room issue with EQ is indeed the last resort, but it is not evil in my book. For instance, my room was custom designed around my Martin Logan speakers and it is acoustically treated with RPG products. So I started from an ideal foundation. However, I do very meticulous room calibration with measurement software and a calibrated mic. As is true in even the best rooms, there are ‘issues’ at frequencies under 400hz. Addressing these ‘issues’ eventually will require some amount of EQ, usually some very judicious cuts, rarely a boost (and if boosting, never more than 2 or 3 db).

Besides frequency domain, there are time and phase issues that can be introduced with blending with the sub and other speakers. However, your DC-1 should let you carefully adjust delays, but does it let you adjust phase to the sub? If not, does your sub have phase controls? You might find that the 125hz issue is due to phase integration between the Clarity and the Sub.

Once you’ve ascertained that the sub to mains integration is adjusted as best as possible with the tools at hand, and you still have an issue, then yes, it’s time to consider some external help.

Introducing any kind of post-processing after the surround processor is a big leap, and given the revealing quality of these speakers, you want to use good equipment.

If you want to really enhance the system, I’d recommend the DEQX system. It will do not only the EQ but will also provide room correction (in phase and time domains as well). Not cheap, but incredibly effective. Hearing a DEQX calibrated system before and after is mind-blowing. Makes talk of cables and other tweaks seem totally irrelevant.
Or the ultimate is go to a Meridian G68 with their built-in room correction and a totally awesome surround sound proc (or step up to a Lexicon MC-12 v5).

If the gold-plated solution is not your cup of tea, then in descending order of cost, here are your alternatives:

External EQ/Crossover for the mains: This assumes you will also bi-amp your ML’s and go full active crossover (and bypass the passives in the speaker). Use a DBX DriveRack 260 speaker processor to perform mid to high crossover and to supply parametric EQ, delays and phase adjustments on each output. This is the ultimate in flexibility and really surpasses anything the factory can do with passives. You also benefit from bi-amping and can use your favorite type of amp for the bass and the panels.

A simpler approach is to simply EQ the mains with a straight up parametric EQ. There are many choices here. Most are from the pro-audio side, which works really well IF you take care to manage the unbalanced to balanced matching between consumer and pro gear. Some Jensen ISO-Max transformers are the key to success (and low-noise) here. Read upon this review of the Behringer Ultracurve 2496
You could also look into other pro-audio effects units that feature parametric EQ (some from lexicon, see the MX series).


The pure analog (and cheap) route is to just get two of the PreSonus 3 band parametric EQ’s some RCA to TRS (unbalanced) cables and give it a shot. For under $300 total, you can determine if the fix for the frequency domain is worth the penalties (albeit very slight) in terms of S/N ratio.

To see what I’ve done, go read up on how I use a speaker processor over on my site. The results are amazing.

 

[lugano]

I have a very difficult postioning problem for one of my Clarity'sin my HT 7.1 video room and have resorted to an equalizer to help.I am intersted to hear about forum members use of equalizers and or crossovers in their system.l

Hi Joe !

Your question is very straightforward and it deserves a similar answer. Let's make things clear: purists will tell you that an equalizer is like wearing a condom, practical people like me will try to convince you that it's a good idea. First of all, IMHO, an equalizer should sport a spectrum analyzer. This helps a lot, because you actually see what kind of garbage you're feeding in. Once you see that above 10k (Hertz) there's no music feeded to your 10k (dollars) gear, you can better understand what's going on and you won't rush to sell your ML's on ebay starting at 1$. GIGO, it's called. Next, a microphone is a must - your ears are good, but a calibration mike is even better. I have such an equalizer, and I use it after every mod to my equipment, even if it's only a cable between the preamp and the power amp. It can always be excluded, but it really helps - with prices around 150 $ for a used Technics SH-8066 like mine on ebay, whay shouldn't you try it ?

 

[lugano]

notice the difference

Same gear, same position for the mike, I changed the LS cables from Monitor Audio to Kimber 8TC, see the difference in the pink noise spectrogram... p1.jpg with monitor audio, p2 with kimber, dimmed color is left channel superimposed to right channel (undimmed).

 

[jmschnur]

Thank you both very much for your responses. I will indeed be careful with equalization.

I do not have a phase ajustment -other than + or _ for my sub woofer so that could indeed be a factor. I am now moving it around a bit. I am also playing with the crossovers (the lexicon gives me 120, 80, 40) as well. However, I think I will be forced to some sort of correction. This room is for TV and video and was modified from a bed room. I thought about video but not sound when we did it so there are several places whch can provide several resonances. I have been liberal with Auralex on several of the walls but there are several troubl spots in the room.

I spent some time lookng at the Rives web site and bought their test CD. That coupled with a Radio Shack level meter gives me a sense of what the problems are. It is nowhere as easy as a spectrum analizer but after calibration it can give me a reasonably accuate data.

I am using the Clarity's for this room (my listening room has B&W 801s (series 80). That room had had some forthought for sound. There is aproblem because we play piano and have a baby grand in the room but it is manageble. The Clarity's do fine for DVD's with a Cinema I, dipole surrounds, and a HDU 1225 sub. THe problem is at 100-300 hz which affects the timbre of voices. I am working hard to solve these and still keep the vribrance of the system. Crossing over at 125 has done 1/2 the job- Now it is just the 160-300 region that needs fixing.

I do like the ML sound and may well change my 26 years B&W's for Summits at some point.

Thakns again for all the good advice.

Joel