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#1 2006-05-15 19:27:01

Zero One
Member
Registered: 2006-03-27

active equalization for speaker tuning

There has been a good thread on taming the 103 over the past few days. I have made experiments with speakers using an old 10 band equalizer for correcting issues and to a point it works well.  The only problems are that it is really overkill size wise and my old unit adds distortion to the signal.  But is occurs to me that perhaps it is possible to build a small limited range equalizer to just deal with the mid range peakiness of small single drivers that is optimised for this application.

My redbacks work in conjunction with a little bass boost module that works brilliantly so it should be possible I imagine to do the same thing for the upper mids.

There may be flaws in this idea, but somehow it makes sense, as an example my redbacks sound magical on most music, but some recordings are just too poor or bright in the midrange to sound comfortable, but it seems a counterproductive to knobble the speakers and my listening pleasure with most recordings to make those poorer ones more listenable, why should my system pander to the lowest common denominator! Perhaps a tuneable active filter can do this. I had this very situation over the weekend, a Genesis complilation album (3 CDs) which somehow in the remixing/mastering has ended just blown out in the mid range on some tracks, it's pretty obvious compared to the original mixes. I have no idea why but I sure don't feel like changing the set-up just to take such sonic disasters into account.

I guess it would even be possible to build such a module into a pre-amp for those who DIY this end of things, and have it so it can simply be switched out if not needed.

BTW I am not suggesting we don't do everything we can to get the speakers sounding good using practical methods first, but rather I saying perhaps here is a solution that means we can optimise the system for good quality material and listening pleasure and then compensate for the crook stuff if needed.

So what do we think, it is possible, has someone done this, is anything actually available.

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#2 2006-05-15 19:42:21

Geek
Member
From: Rosedale, BC, Canada
Registered: 2005-11-09
Website

Re: active equalization for speaker tuning

Not a fan of active filters myself, but if those inevidible icky phase-shifts that accompany them can be tamed, I don't see why it couldn't work smile


-= Gregg "t3h GeeK" =-
http://geek.scorpiorising.ca
"Ratings are for transistors, tubes have guidelines"

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#3 2006-05-15 20:26:17

hitsware
Moderator
From: Sacramento, Ca.
Registered: 2005-08-06
Website

Re: active equalization for speaker tuning

Geek wrote:

Not a fan of active filters myself, but if those inevidible icky phase-shifts that accompany them can be tamed, I don't see why it couldn't work smile

The 'phase shifts' are attendent with the filter action.
A certain frequency dependant cut or boost operates
by 'shifting' (then summing the resultant) adjecent frequencies.
I prefer passive because I don't like the sound of alot of feedback
(usually used in active eq circuits).

Last edited by hitsware (2006-05-15 20:27:03)

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#4 2006-05-16 00:07:12

westend
Member
Registered: 2005-12-31

Re: active equalization for speaker tuning

I have a pair of Advents that have a three position toggle on the back. It shifts the signal to the tweets between simple crossover components. You could build a circuit similar to that but notching/unnotching the crossover to allow for brightness in certain program material. This is that simple circuit design: http://www.classicspeakerpages.net/dc/u … s/1288.jpg .

Last edited by westend (2006-05-16 00:07:36)

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#5 2006-05-16 00:40:29

ronbrady
Member
From: Ridgecrest, Calif.
Registered: 2005-07-27

Re: active equalization for speaker tuning

I have experienced essentially the same problem with a pair of Beta 12lt's that I have running in MLTL cabinets. The 12lt's have a 5db rise from 1khz to 3khz so I designed a parallel notch filter using a 0-8ohm rheostat which allows me to adjust the strength of the notch filter just by turning the knob on the cabinet. It works really well and is easy to adjust to suit different recordings. It is completly passive and when the knob is turned all the way to 0 ohms the filter is simply bypassed out of the circuit. This type of design also works well on BSC and allows easy adjustment for differnt recordings and/or room size.
Best wishes
ron brady

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#6 2006-05-16 02:16:09

karlsonkab
Member
Registered: 2006-03-21

Re: active equalization for speaker tuning

hey Ron Brady - what LC and conjugate are you using with 12LT?
(you make it into coax with phase plug and 3/4" dome?)

here's my 12lt without any LCR outdoors on a 2'x4' baffle and with 1ft wing propped up to give 3'x4' with driver offset.
12lt with no highpass jumps too much on my OB

12lt6th8gn.jpg

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#7 2006-05-16 02:17:31

GM
Member
Registered: 2005-07-31

Re: active equalization for speaker tuning

Greets!

Yep, in the 'good ol' days' it was labeled a 'Presence' control and a three or more way had one for the HF labeled 'Brilliance'.

GM


Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

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#8 2006-05-16 09:36:00

karlsonkab
Member
Registered: 2006-03-21

Re: active equalization for speaker tuning

Hey GM - wonder was this circuit on EV's  1960's EV SP15? (that one had a knob) Freddy

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#9 2006-05-17 02:08:17

GM
Member
Registered: 2005-07-31

Re: active equalization for speaker tuning

Greets!

Those were just variable L-pads IIRC.

GM


Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

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#10 2006-05-19 04:32:40

Zero One
Member
Registered: 2006-03-27

Re: active equalization for speaker tuning

Hi Ron
JUst looking at your idea

(The 12lt's have a 5db rise from 1khz to 3khz so I designed a parallel notch filter using a 0-8ohm rheostat which allows me to adjust the strength of the notch filter just by turning the knob on the cabinet. It works really well and is easy to adjust to suit different recordings.)

If one was building a purpose built amp to go with the speakers, would it work if this was actually integrated into the output on the amp and then controlled from the amp, or would it cause problems due to the effects of the cables.

Thanks
Brad.

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#11 2006-05-19 11:25:26

ronbrady
Member
From: Ridgecrest, Calif.
Registered: 2005-07-27

Re: active equalization for speaker tuning

Decent speaker cables won't  make any difference. You can mount the notch filter et. al. in or on the speaker enclosure or you could mount it in or on the amp. It doesn't matter. What does matter is the quality of the components. The lower the DC resistance the better, generally speaking, unless your fullranger would benefit from a little series resistance. I chose the ERSE super Q inductors and solen capacitors. The rheostats are actuall 8 ohm l-pads and I am using the 0-8ohm portion. Again, a quality part is suggested. Parts express sell good quality l-pads (260-252) is the one I used. ($7.50 ea) If you intend to include a BSC in your design you can also use the same l-pad in that circuit also. If you anticipate moving the speakers from one room to another or re-arrange the furniture and change speaker placement it makes it very convenient to dial in the BSC with just a turn of a dial. Parts express sells a speaker control panel (260-235) which contains two L-pads in one panel plus a series of LED's as a power monitor. At $17.00 ea they are a good value and it is fun to  watch the LED's run up and down with the big bass notes,
it's cheap entertainment.
Best Wishes
Ron Brady

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