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OldCarNut 8th December 2004 11:22 AM

8" mid woofer--suggestions???

My 1'st post here! I'm mostly experienced w/car audio, but I'm currently involved with some home speakers I recently upgraded.

I have old Yamaha 8" 3-way bookshelf speakers I purchased from Rogersound Labs back in 1988! Believe it or not, I had them in my first car, have been kicking around all this time, and I recently returned them to home use. I currently refurbished them as 8" two-ways with Vifa 1" dome tweeters crossed over apx. 3000 Hz, and Rockford Fosgate Series 1 subwoofers from 1994 (specs on RF's website). These little 8" 8 ohm woofers produce GOOD mids, and blend well with the tweeters. I use a 150 hz cap for a hi pass (reportedly cuts lows off at 133 hz) becuase I also use a pair of Fisher speaker cabinets that I reinforced, and fortified with 1 MTX 8 ohm subwoofer in each cabinet (w/8.2 mH coil for a reported 150 Hz lowpass in each).

The problem with the 8" woofers is under heavy bass loads, they make LOUD "clacking" sounds on hard bass hits when playing certain tracks loud. I have found if you push the pistons in far enough, they will "bottom", like two hard things contacting (voice coil against the magnet?). I think I am hearing these things "bottom-out" on these instances!

I know my caps in line with the 8" woofers are doing something because I tested with one song I knew would cause the problem, and ran with and without the capacitor back-to-back on the same song, and you can see a slight reduction of cone excursions.

What do you guys think? Should I redo the crossovers to a higher high pass point for the 8"er, or get rid of the RF 8" woofers and get a real quality 8" midbass that will blend well with my Vifa tweeters and handle the heavy signals as well?
I like strong lower mids, as well as what should blend well with the tweeter. I'm listening to trip-hop, downtempo stuff and a variety of rock music.

Thanks for reading and I'm open to any suggestions!

Oh yeah, and I'm on a budget!


ERICSPEEd 8th December 2004 11:36 AM

I use a 150 hz cap for a hi pass (reportedly cuts lows off at 133 hz)

Are you refering to the x-o's used for caraudio, I mean to say the "easy to install" in-line type (usually just a cap). If so, being a 6dB slope I would use a 2nd order (12dB slope) or higher.

Your using the orig 8" right? Also trip-hop can have some serious bass (in the 50HZ range and lower of course). That poor old woofer is getting the beaten to death. And it is bottoming out. The vc former is hitting the back plate. Not good.

If you like the sound of the woofer with the new tweeter. Get a higher order hi-pass x-o.

sbolin 8th December 2004 12:16 PM

Ok, I just wanted to reminisce about RSL. I loved that place growing up (yes, I am dating myself, so what!). They had the nice equipment (not super high end, but quite good), and even had their own line of decent speakers. Very sad when they went out of business.

As far as your speakers are concerned, a couple questions:
1. Did the 8" act as a woofer before or a midrange? If a midrange, move on. If it was the woofer before, it doesn't really make sense that it would be bottoming out now, when it handles less power (presumably) than when it acted purely as a woofer. :confused:
2. Do both speakers bottom out, or just one? If one, try switching the pair and playing the same song that caused the problem, and see if it happens again. If the same speaker is having a problem, the speaker itself may have a problem and need to be replaced.
3. If both, I would first try changing to a higher order filter crossed at a higher frequency before going to a different speaker. Adding a couple inductors and caps should be cheaper than a whole new speaker.
4. Tough to recommend anything, how high/low is your budget?

OldCarNut 9th December 2004 08:29 AM

8" mid woofer........
Thanks for the replys!

I want to clarify a mistake I made--on my hi pass capacitor for my 8" RF woofer, I'm using a 150 MICROFARAD (not Hz) cap, by itself, inline w/the positive feed. I guess I would call it an "easy-to-install" inline, but I bought those and my tweeters from Speaker City in Burbank, where they are now shifting their emphasis to home audio exclusively, and phasing out of car applications. I would think you could use the caps in any application?

The RFosgate woofer was a woofer 1'st. Even the documentation states they should have a 100 Hz low pass used with them. They have some significant cone travel!

I recently aquired an Onkyo M5150 amplifier (reportedly 150 wpc), and driving my speakers with that instead of the amp in my old Pioneer sx 727 is where I noticed the RFs bottoming out while in full range. That was the time I realized if I could remove them from the duty of working as subwoofers, I could still get some use out of these RFs in the old Yamaha boxes. I'm apalled that my "severe-service" speeakers behave in this way, even with a high-pass crossover. And they BOTH bottom out. It sounds ugly, and is pretty damn alarming when it happens!

But I think this is a reasonable consensus. Go with at least a 12 db/octave x-over--I gather that simply provides further "cleaning up" of any bleed-through of lower frequencies?? Agree to that being cheaper than buying new drivers. Maybe cross the RFs at 150 hz, 2'nd order since my subs are low-passed at 150 hz.

And yes, RSL was just a CANDY STORE, further embellished by two-page ads every week in the Calender section of the LA times! How could you stay away?!


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