I've been trying to read up on bi amping.... What is it, how does it work, what advantages and/or disadvantages does it give to speakers. My understanding is that bi amping is done through wiring of the crossover, correct? My current setup is a jbl px300.4 running boston pro60's in the front, and the rears are left as stock. Will this be safe to run with my setup? Because, i'd rather try to hear the difference between different wiring setups then just word of mouth. Thanks much for your help in advance
bi-amping means you use one amp to power the component speakers' tweeter and another amp to power the components' mid/woofer. In order to do this the passive cross-over must be capable of bi-amping. It should have two seperate inputs. The advantage of bi-amping is that you get better sound quality. However if you've got a decent quality amplifier that has lots of extra headroom (power) then bi-amping is probably not necessary. But it can't hurt You can also bi-amp through an active cross-over network, but the connection is a bit different.
If you have a decent knowledge of car audio (including the gain setting) then bi amping can give very pleasing benefits. The benefit of using multiple speakers is to gain cleaner reproduction of sound at all frequencies. Unfortunately, each speaker has a different sensitivity. Meaning that the lower sensitivity speaker (normaly the woofer) will get louder slower than the higher sensitivity speaker. Have you every noticed your highs sounding ballanced at lower levels, only to become harsh at higher levels? This can be fixed through bi-amping the speakers. Most crossovers will have a tweeter attenuator that does the same thing. The only problem is that they are very inefficient and tend to taint the sound of your tweeter. If you have a extra amplifier, then I highly suggest experimenting with the bi amping. Your bostons are a very nice set of comps and should benefit nicely. I had a pair of JL xr650's that greatly benefited from bi-amping. Here is the difficult part. Do you know how to correctly set gains? The 3/4, by ear method is not going to work here. You will need three sets of test tones, a multimeter, and possibly a spare speaker. You can purchase a decent multimeter at sears. I bought mine on sale for nine dollars. The test tones can be purchased on a test cd from places like crutchfield or sounddomain.com. If you have high speed, you can email me at mikegett@msn.com and I will send them to you. One test tone is a sample of a clipped sine wave. This will be used to find the clipping point of your HU. This is very important and often overlooked by installers. Simply play the clipped tone in your cd player at low volume to get a idea of what your good sine wave will sound like. Next, you will place in the good sine wave (I use 2khtz) and raise the volume till it clipps and sounds like your previous example. You should also have all external amps gains set to the lowest point. You may blow a speaker other wise. This will be the max point you want to raise your volume. I haven't checked my 2007 camry, but I will bet it clipps around 30. Possibly higher with the speed-volume adjustment on.
After finding your HU clipping point, it is time to set the speaker gains. Here is the key. Lower frequencies require more wattage to be reproduced. This means that at the same volume a 30htz will use more wattage than a 15,000khtz. So you will want to set your mid and woofer gains to there fullest possible point. The tweeter gain will then be matched by ear to your preferance. The JBL is listed to produce 123 watts rms at 4 ohms. Your bostons provide a unique 3 ohm load. The JBL is not listed to be stable at 2 ohms but I would imagine that 3 ohm should work. Just be sure to check it for over heating. Judging by your JBL's 4 ohm bridge point of 358, 2ohms should be close to 178 per channel. That means that you amp shouldn't produce any more than 150 watts RMS at 3 ohms. The square root of (150x3) is 21.21volts AC. So 21 volts is what you will be trying to set your woofer gains to with the multimeter. In order to do this another test tone will be needed. Here is a tip. If you are setting gains with a test tone, use a tone closer to the frequency played to maximize your efficiency. For example, a sub playing frequencies around 60 hz should use a 60hz test tone. If a 200 hz test tone is used then the amps gains will be too high as the sub hits 60 hz and will cause clipping. If 60 hz test tone is used for a mid range driver running 200 hz, then the amp will not produce its highest rms rating. Even though the bostons are rated to play fairly low, I would suggest setting the gains for a modest 100hz. Most mid bass is all in the 100-200 range. Place the 100 hz test tone into the cd player. Ensure your gains are set to the lowest point. If you use any bass boost on the cd player or amp, then turn it on as well. Place your multimeter into the ac voltage setting. Now place the positive end of the multimeter onto the positive speaker terminal of the amp used for the midbass. Do not do this at the crossover. You must do it at the amp to ensure you have the correct resistance. Your speaker must be hooked up to ensure the proper resistance. Next place the negative wire of the multimeter to the negative speaker terminal of the same amp. If you place the multimeter terminals under the speaker screw it will hold it in place for you and free up your hands. Now, ensure your multimeter is on and in the ac voltage position. Turn on the car and cd player. Play the 100hz test tone and place it on repeat. Increase the HU's volume to just under the clipping point you found earlier. As the test tone plays, raise the amps gain until the multimeter reads 21 volts AC. Do not go higher. One volt will make a difference of 11 Watts. Once the multimeter reads 21 turn off the cd player and unplug the meter. You have successfully set your mid range gains to the most affective point.
Most likely the tweeter will never use the full 150 watts. I have never used over 50 watts rms on my tweeters. It becomes extremely painfull to the ears. You can do the same approach to the tweeter amp to get its fullest potential. You will just need a higher test tone. Use a 1khz test tone if possible. Once again, play the test tone and have the volume set to your determined clipping point. Your multimeter will be on the speaker leads of the tweeter amp this time. Raise them till you achieve the 21 volts AC on your multimeter. I am going to bet the volume became way to loud. This is the point that I decrease the tweeter gain till it makes a pleasing match with the midrange. Good luck and enjoy your bostons. Mike Gettinger.
MIkegett thanks a lot for your help, it is much appreciated...i might need more help further on because the information was a bit overwhelming to me. But basically to my understanding. If i have a a 2 way component set, then i would would need to get two test tones along with the sample of a clipped sine wave. After i would set gains at their lowest possible and turn the volume up till i hear the resemblence oif that cliped sound example. this is where i am confused. Now once i hear that sound should i tone the volume just bleow that point or leave it at the clipped point? Once that is clear, then i get the multimeter and plug it up to the possitive point and then the negative point. PLay my cd until i hear the clipping point, and adjust gains till the multimeter reads 21 volts. and then i'm set for the low end of my 2 ways. Then move onto the tweeter adjust to the 21 volts, and tone down to my ears liking. But before this i need to wire my my facotry boston crossvoers to bi amp mode. But once all this is done...then i'm done?
Lastly, why would i need an extra amp and speaker? i would imagine the the spare speaker would be for testing the clipping point(does it have to be the same model speaker being used). and not really sure about the spare amp.
Sorry about any confusion. Here is a link to JL's website. They have a nice tutorial set up as a slide show. http://mobile.jlaudio.com/support_pages.php?page_id=143
Ignore the extra speaker. I use it while doing the clipping test so as not to blow my other speakers. When testing for your HU clipping the volume will go quite high. And be sure to wear ear plugs. Every amplifier has a point that it will produce the maximum wattage continuously. Otherwise known as the RMS rating. When the amp goes beyond this point it will do burst of wattage up to its given max rating. The clipping point is when the amp continuosly stays past the RMS range. The prolonged clipping will cause the amp to distort the signal being produced. This distortion is very audible in upper frequencies. Lower clipped frequencies like your bass notes can be virtualy impossible to hear. Your HU's internal amp and its preout amp will have a clipping point just like your external amplifier. The best method to determine the clipping point is on a o-scope. Since we do not have one, it can be done by ear. The reason I suggested downloading a clipped sine wave is to let you know how it will sound. If you can't find one, then simply use a 1khz test tone. Ensure any bass or loud feature used is on. Play the test tone and increase the volume till you hear a audible change. It will go from being a long beep to a very speratic pulse. Your volume will have to get pretty loud, but this is going to tell you how high your HU can be turned up till it starts to distort your music. Once you have found that clipping point don't every increase your volume beyond it. You will only be feeding your speakers distorted music and it will shorten the life of your HU. Be aware that every manufacturer will have different degrees that the HU can go till it clipps. Some cheaper HU's (like OEM's) will clip at 1/4 volume. Most will clip at around half to 3/4 volume. My high end Eclipse HU's have gone as high as 90-100 percent without clipping. This is very rare and not to be expected from most brands. The gains of your amplifiers will be set just under this clipping point. After you have attached the multimeter, and your gains are at zero, the HU volume will be raised to just under your clipping point and left. Your desired test tone can then be played while you rasie the amps gains to match the 21 volts needed. I do need to warn you. A continuous test tone can and will send your amp into protection very quickly. A 30hz test tone can burn up a voice coil in under a minute. This is why they only supply them in 20 second bursts. I suggest having a friend start the test tone so you can be in the trunk raising the gains. It will take four to five attempts before you hit it correctly so give the speaker time to cool between. I just wait a minute for midrange speakers. A sub may require more time. This is also a good reason to have a spare speaker handy. If you do use a seperate speaker for setting the gains then you must ensure that it is the same ohm rating. Since your bostons are 3 ohm it will be nearly impossible for you to find one. What I meant by seperate amp is your 4 channel JBL. Channel 1 and 2 are actually a entirely different amp from channel 3 and 4. This is why you must set gains for them seperately. Good luck and I appologize for any more confussion. It seems a bit overwhelming at first, but it is worth knowing. Why have a great system if it is not tuned properly.
totally understandable....seeems a bit difficult if i don'tr have a friend to help me out or a remote to set the cd player. So do you recomend that i do this as quickly as i can? And if i can't find the clipping point or forwhatever reason its taking me a long time to finsih. would you recomend that i just rest the speakers for a couple mins if i can't infd that point then continue on the amp gain that i'm on, then move on? Thanks a lot for your help..i'll be sure to check out the jl website and let you know how it turns out.
What car and year do you have? I have a 2007 camry and a 2004 corolla. I tested the camry and it clips at 50 with the bass and treble all the way up. With the ASL on high and driving at 55 it clips as soon as 38. What is your email and I can send you the test tones?
So the Hu clipping point is the volume that i should NEVER exceed. but coming close to is okay? Lastly....what is the difference between biwire and biamp, i mean i understand the logic behind the prefix bi...but does bi amping mean i am wiring each part of the component directly to a certain channel? for instance, ifi have a 2 way component system then each tweeter gets a channel, and each midrange gets a chanel, correct? So then bi wiring according to my boston manual, is the negative and the possitive of each tweeter spliced into each midrange wire then going straight to the amp..thus having only 4 wires total to the amp(2 positive and two negative). Please clarify
Your correct about the clipping point. Once you have found it, just try to avoid go over. Alpines have a shorter range of volume control. My previous DVA-7996 clipped at 22 and 25 with loud features on. Without the loud on, it went up to 33. You can probably expect close to the same. I honestly don't know what bi-wiring is. Bi-amping means that your tweeter will be powered by one channel of your amp (left and right front) and you woofer will be powered by another (left and right rear). I will send you the sine waves. If you have a link to the boston manual or a pdf then email it to me.
Sorry about that. I just checked and my copies stored on the computer won't work either. I must have done something to them when I imported it. I will find the cd and pull the files for you directly off of it. Later, Mike.
mikegett..thanks again...i will let you know how everythign turns out as soon as i pull some money to get more wiring, and pull soime more time, lol. ANyways thanks alot for your help...i'll let you know if the sounds clips work or not
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You can also bi-amp through an active cross-over network, but the connection is a bit different.
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