posted
While playing a sine sweep, I noticed that near 250Hz, there is a weird change of sound, as if the speakers are wired out of phase at that frequency, then the sound returns to normal around 300Hz.
Does anybody have a suggestion how to combat this?
I have 8" midbass in the doors @ 60-150 Hz, and 6-1/2" mids in the kicks @ 150-3k Hz.
Thanks in advance.
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Posts: 95 | From: PA then IL then TX | Registered: Oct 1999
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posted
A wierd sound? As in what? If there was a change of phase, it would be wierd yes, but the most noticeable effect would probably be a loss of volume and a left/right "wiggle" to the sound.
Honestly, my first quess would be that the enclosure of your 8's or 6's is resonating at the 250hz frequency. Use a real sine generator or specific frequency discs (that have real 250hz tones and tones near it), disable the speakers and isolate the problem.
Try it with just the sixes, and try it with just the eights. I would start with the sixes because they are the prevalent output speakers in that freq. range.
If it is not a real resonance issue, return to the forum and smack me around :-)
ShadowStar
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Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
The sound is exactly what you describe: a loss of volume and a left/right "wiggle".
I've a hunch it may have something to do with the path-length difference of the mids :-( The left mid is about 8" closer to my left ear than the right mid is to my right ear.
I'll do some disconnecting and snooping around and post back the findings.
Thanks.
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Posts: 95 | From: PA then IL then TX | Registered: Oct 1999
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First thing to check in this case is that all speakers are wired in phase. That is, all negatives are wired to negative terminal on speaker and positives are wired correctly as well. It wouldn't take but one wrong wire to throw it off.
After assuring yourself that all the speakers are wired correctly, are you using crossovers? Crossovers attenuate aound by changing signal phase (I'm not *too* sure about the specifics so don't quiz me) and your crossover could be messed up or degrading.
ShadowStar
------------------ ShadowStar
143db Standard Cab Ranger
Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
What you describe can be caused by many things, some of which are mentioned above. I have to throw this in, consider the possibility that your mids "beam" at that frequency. Anyway, passive crossovers do cause phase shifts of all kinds. The more components in a crossover, the more phase shift problems you'll discover. Look at your system on an analyzer and see what your "weird sound" looks like.
------------------ STILL waiting to hear a GOOD pair of HLCD's!!
If it dont fit, force it... if it breaks, it needed to be replaced anyway...
posted
You may also be experiencing standing waves in your particular vehicle at that particular frequency area. Things such as vinyl, glass, plastic, and such can cause reflections reacting with waves from the furthest driver. What a wonderful world car audio is applied to. Just imagine if we could coat our entire inside of the vehicle with notched foam. Would sound great but boy that look may not fit well with contemporary vehicles. Maybe if we were in the 70's again... hmmm... shag carpet all over???? what do you think???
------------------ Brian Obara Metro Audio Dynamics Omaha, NE
Can you smell what the Griz is cookin'???
Posts: 732 | From: Omaha, NE | Registered: Aug 1999
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First I disconnected the 8" midbass and did the sine sweep - no problem. I disconnected the 6" midrange and re- connected the 8" midbass - no problem. I re-connected the midbass and ran the sweep again, this time listening from the center console (midway between left and right side speakers) - no problem.
So it had to be some sort of weird interaction between the 6" and 8" around 200-250Hz at the driver's seat listening position. Thing is, even though I have the 8's crossed over at 150, they have a very pronounced midrange ripple, which would explain the interaction.
Luckily, my Audio Control 24xs has a speaker wave alignment adjustment which I tweaked to try to solve the phunky phase problem... and it worked! Thanks for all your suggestions. The drive to work tomorrow morning is going to take a little longer ;^)
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Posts: 95 | From: PA then IL then TX | Registered: Oct 1999
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