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-   -   Bass blocker sizes? (http://www.wakeworld.com/forum/showthread.php?t=791916)

corerider 02-21-2012 6:21 AM

Bass blocker sizes?
So I'm helping my brother out on a stereo project for his boat and basically I'm having to rewire the entire system because the "Stereo shop" that preveiously installed the system had their heads up their arses evidently. We are trying to re-use everything we can, but when it came to the speakers I've run into some questions...

1) He has 4 sets of Clarion CM1632's. I haven't had much luck finding info on these, but it looks like they cut out a bass blocker or cross-over and just wired the mid-ranges speakers to 2 channels and the tweeters to the other 2 channels. (1ohm loads on the amp... yeah!) What little I can find these don't look to be componet speakers, just separates with a bass blocker for the tweeter. Is this right? If so would this be the correct blocker to use? http://www.hifisoundconnection.com/S...id/0/SFV/30046

2) Anyone with knowledge on these speakers that could verify what I'm seeing?

I wish I had taken pics of the install these people did. I'm talking wire nuts, 1 ohms loads on amps, etc. There is no way this shop coulds still be in business.

david_e_m 02-21-2012 8:30 AM

5 kHz sounds about right on the tweeters. Just because the midbass drivers are 4-ohms doesn't necessarily mean that the tweeters are 4-ohms also. I would check this to be certain. I would also find out for sure what the exact mfd. value of that capacitor is and confirm the half power frequency for a particular impedance. Its better to be a little thorough and avoid expenses later.

Earmark Marine

corerider 02-21-2012 11:43 AM

David, is there any way to look at the capacitor and tell what the value is like you can by reading the stripes on resistors? He managed to find only one of the factory capacitors/crossovers whatever they are. I haven't really had any luck find info about these speakers online as they are discontinued. It is just a little plastic white box that clips to the midrange speaker and has a pair of wires coming out of either end.

I did read the resistence on both the midrange and tweeter. They were both 4 ohms each.

david_e_m 02-21-2012 1:17 PM

We usually grow our capacitators in between the turnips and cabbage and we don't normally label them. But the value is always screened by an alpha-numeric designation when they are identified...like 3.3 mfd...unless for some reason the vendor wants to keep it a mystery.

Earmark Marine

mikeski 02-21-2012 2:31 PM

The online manual for those speakers states the factory crossovers are 12db/octave so they would have a capacitor and inductor included with the original crossover. The bass blocker (capacitor) will only taper at 6db per octave so you have a decent chance of blowing the tweeters. That said I might go by the local electronics shop and start with 2.2uF caps inline to the tweeters and see how they sound. Maybe drop down to 3.3uF if the tweeters don't seem to be doing much, keep dropping until you like the way they sound but each time you go lower the crossover you are reducing the power handling capacity. Both are common, the 2.2 provides more protection. If the tweeters are 4, 8 or 16 ohm it makes a big difference. Unfortunately Clarion does not list the tweeter impedence. You will need to utilize NON-POLARIZED capacitors.


basic info:
http://www.bcae1.com/ scroll down to capacitor or passive crossover on the right column.

corerider 02-23-2012 5:55 PM

Mike, I finally got back to his boat and took apart the one crossover he could find.
Looks like it has a 4.7uF cap. I've learned that the coil of wire is an inductor, but I'm not sure what the little piece to the right of the cap is. The tweeter is a 4 ohm load. From the lesson I learned on bcae1.com I guess the inductor keeps high signals from the mid-range while the cap keeps low signals from the tweeter. I don't feel comfortable enough to put something like this together and have told him to start looking at buying some new speakers, but if I were to just put a cap on the tweeter would I be okay?

david_e_m 02-23-2012 6:46 PM

That is not a 1st order highpass and 1st order lowpass crossover. There is no inductor nor any element on the midbass speaker. Its a 2nd order highpass (tweeter only) with a series capacitor followed by a parallel inductor. Try using a .15 mH inductor with the 4.7 mfd capacitor. The smaller yellowish disc is probably a tweeter protection device.

Earmark Marine

david_e_m 02-23-2012 6:56 PM

If you just want to use only a series capacitor that is okay. Because you will be using a 6 dB slope rather than a 12 dB slope you will want to use a higher crossover frequency for protection and make sure that the tweeter is sufficiently attenuated long before you encounter the tweeter resonance. So for a 1st order crossover use a single 3.3 mfd. capacitor in-line on the tweeter. It won't sound exactly the same as the original crossover but it will get you by without risk to the tweeter.

Earmark Marine

mikeski 02-23-2012 9:52 PM

If it were my boat I would just try to find all of the crossovers and put them back on the tweeters as the speakers were designed then run one speaker on each amp channel. Better yet add a subwoofer to the rear channels of the amp and let the front channels run the 4 boat speakers. Follow David's advice and go with a 3.3uF cap if you can't find the other crossovers. As the manual for those speakers lists them, they are 12dB/octave crossovers, they also have another electronic component but I can't tell what it is from your picture. Maybe a disc resistor to attenuate the tweeter a bit?

corerider 02-24-2012 1:16 PM

I will be bridging 2 channels of the amp we are using for a sub. Planned on wiring 2 sets of these speakers parallel on the other 2 channels for 2 ohm stereo. I'm just going to get the 3.7uF caps and hope for the best. He is not going to notice any differene in sound and doesn't want to spend a bunch of money getting new speakers seeing as he may get rid of the boat this year anyway. Thanks for all the help guys.

mikeski 02-25-2012 9:39 PM

Good plan. Once you get everything installed make sure you phase test the sub. I am surprised how often they run better out-of-phase. Just did a new sub in my truck, swapped the phase of the sub just for kicks, sure enough it eliminated that mid-bass hole in the frequency spectrum and smoothed out the low end making it sound 100% better. I was too busy to install it myself so I had a reputable shop do it. I did tell not to worry about tuning it since I knew I would be tweaking all of the settings anyway.

david_e_m 02-26-2012 9:02 AM

Phasing issues can get complex. In the simplist form you have a 180 degree polarity change by reversing the terminals. Then you have the high and lowpass crossover filters that create a gradual and opposing phase rotation through the crossover region. Then you have phasing issues related to the speaker and the cabin boundaries plus phasing issues related to the listener or point of perception and the cabin boundaries. Then you have the phase contradictions between the direct speaker radiation and the reflected radiation that reinforce at some frequencies and cancel at others. Then you have phasing issues determined by differences in distances.
Here is an example of what may be happening within a pickup truck cabin like Mike's.
In one scenario a woofer behind the rear seat is at one extreme of the cabin. The listener is positioned approximately in the middle of the cabin. At a bandwidth centering at one particular frequency based on the cabin dimensions the direct radiation and reflected radiation off the front of the cab reach the listener out of phase and cancel.
If you have a downfiring woofer in the center of the cab then its splits the cabin dimensions and the affected frequency may be twice as high.
Now the midbass drivers (whether components or coaxials) in the front doors may have the identical and therefore correct polarity as the woofer but given that the corresonding crossover filters change the phase, the phase of the midbass driver as it reaches the listener at the frequency of concern may be phase forward or phase retarded. Or, the crossover region determined by the frequency may or may not be coincidental with the frequency region most impacted by the vehicle.
Changing the polarity of the midbass driver as compared to the woofer can have a profound impact. But there is no surefire rule as the crossover frequency, speaker(s) locations and orientations, listener location and cab dimensions can combine to produce very different results with the same equipment.
The most experienced designer or installer may be able to anticipate and predict where conflicts will appear but there is no way to predict the exact correction in advance.
So having an educated ear like Mike and doing some trial and error can produce some significant results. And if the difference seems a wash then try re-adjusting the crossover frequency just a bit as this might put you over the line in favor of one polarity or the other.

Earmark Marine

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