Outlaw Audio home shop products hideout news support about
Topic Options
#5531 - 01/24/04 02:03 PM Crossover Repair / Alternatives
bestbang4thebuck Offline
Desperado

Registered: 03/20/03
Posts: 668
Loc: Maryland
All of my “full-range” speakers are the same three-way model. For a quite a while, I have noticed that the center speaker has been sounding different that the others, more “boxy.” I did a one-by-one comparison test with a tone generator set to sweep through the crossover points, plus one and minus two octaves. For a crossover of about 800Hz between the woofer and the midrange, I swept from 1600Hz to 200Hz, and noted the acoustical output of each transducer. Surely enough, on the speakers sounding normally, as the sweep approached 800Hz, the midrange output began to decrease and had fallen off significantly by 400Hz and below. On the boxy-sounding center speaker, there was only a partial fall-off starting at 800Hz for the midrange, while there was a mild boost at about 400Hz before roll-off became significant about 300Hz.

I surmise the following:

1) Prior to acquiring Outlaw processing and amplification, I came home to find my youngest son playing music of his choice to the point of mild clipping. He was in a Pro-Logic mode, so the center speaker was taking the brunt of this torture. Because crossover capacitors in series with the signal are meant to restrict low frequencies to the midrange and tweeter, and because clipping produces nasty high frequency spikes which the capacitors pass, my guess is that one or more of the capacitors’ dielectric in the crossover has partially or wholly failed, behaving as if a low value resistor has been placed in parallel with whichever capacitor or capacitors have been affected. This would allow frequencies lower than intended to reach the midrange driver.

2) Typically, in the design of a mid-range loudspeaker section, there should not be significant resonance of the mid-range cavity until at least an octave below the intended low crossover point. For the loudspeakers with properly operating crossovers at 800Hz, the electrical energy at 400Hz is low in the midrange section. Assuming the cavity would be allowed by the designers to have some resonance at 400Hz or below, the lack of signal energy at 400Hz means the resonance effect has less energy to drive it acoustically, and so there is little 400Hz range boost in loudspeaker output. However, if the crossover has partially failed, and is allowing significant signal in the 400Hz range to reach the mid-range driver, a formerly less significant resonance now has plenty of acoustical energy to drive it. As a result, I see a rise in the loudspeaker output curve around 400Hz.

Next steps:

1) Swap the problem speaker out with a normal one and see if the problem follows the speaker. This rules out anything prior to the speaker. This I have done.

2) Not yet done: partially disassemble the loudspeaker exhibiting the boxy sound. Remove the capacitors one-by-one from the crossover, checking for a value approximating the value printed on each capacitor.

Solutions:

1) Replace any capacitor that fails this check.

2) Forget the passive crossover(s) altogether, go with active crossovers plus true tri- amplification!

My “enthusiast” soul with a love for “tech” wants to try the second solution, even if it takes more time, money and work. Meanwhile, does anyone have a suggestion for obtaining high-quality crossover capacitors without "highbrow" cost?



[This message has been edited by bestbang4thebuck (edited January 24, 2004).]

Top
#5532 - 01/24/04 03:22 PM Re: Crossover Repair / Alternatives
soundhound Offline
Desperado

Registered: 04/10/02
Posts: 1857
Loc: Gusev Crater, Mars
I would certainly go with the active tri-amp option. You will never want to go back to inefficient and distortion producing passive crossovers ever again. Some nice solid state amps for the woofers and tubes for the mids and highs.....

If you go the repair route, this is a local to me company that sells good crossover components.

http://www.speakercity.com/

Top

Who's Online
0 registered (), 117 Guests and 3 Spiders online.
Key: Admin, Global Mod, Mod
Newest Members
Hedoboy, naowro, BeBop, workarounder, robpar
8705 Registered Users
Top Posters (30 Days)
patm1198 1
Helson 1
Forum Stats
8,705 Registered Members
88 Forums
11,326 Topics
98,691 Posts

Most users ever online: 476 @ 12/28/22 08:54 PM