Popping Sounds on my woofers.

[Psyphre]

Hey, im making my first pair of speakers with a tweeter and 6 B&W mid/bass drivers (Each speaker: 1 Tweeter, 1 Mid, 2 Woofers). Currently I havent put them in the enclosure, they are just wired up on my living room floor. I was testing them out, tried playing some games, fantastic (the bass is great for counterstrike). Music, also great. Movies? Not so much. When playing explosions, the woofers (at the peak of the sound) make popping sounds (like when u hold a piece of card rigidly, and bend the centre so it makes that "pop"). This is only if go over (roughly) half way on the volume bar. Im not sure what the cause is since i'm quite new to all this. Im thinking maybe its because the drivers dont go very low (down to 75Hz) and maybe the explosions are below that threshold? I looked at some other woofers on the internet and saw on a couple frequencies that went to 30hz. But I dont know if this is normal, for all I know around 70 is standard, and going down to 30 are for higher end drivers?? Or maybe this is just what happens when its not in its enclosure?

If anyone can help me I'd greatly appreciate it.
Thx

 

[knobturner75]

Since these are not in an enclosure, the popping noise you are hearing is something bottoming out. Either the voice coil or the cone is bottoming out and hitting the base plate for the coil or the basket for the cone. You are overdriving your speaker. I would strongly suggest not doing that anymore. Also, if you are running these in this way without a crossover, you need to stop that as well. You can ruin your nice speakers. The crossover will HELP to protect your drivers from being overdriven, but I know from experience , they will not totally protect them. It is very important to remember that distortion is the enemy. It is easier to destroy speakers using low power driven to distortion, than doubling or even tripling their power capacity with clean power.

 

[Psyphre]

Ah thank you very much, that sounds like its the reason. But what I dont understand is that im not actually playing these speakers very loudly (btw they are connected to a crossover). I tried watching a film with average sound levels and it still occurs, which means I have to watch action films quietly . Conversly I can play all my music quite loud with no problems.

 

[knobturner75]

When you get them in an enclosure, the enclosure will help to "suspend" the speakers. The air inside the enclosure will provide resistence to the speakers so they will not bottom out as easily. This is one reason why it is so important to figure out the correct size enclosure. Also, it is extremely important to get your port tuning correct, if you are using one. If it(port and/or enclosure) is too large, the speaker will act as if it is not in an enclosure. Which you know now how well that is. And if it(port and/or enclosure) is too small, then you are going to limit the low end performance of your speakers.

Another thing you can do. You didn't mention which receiver you have, but you should be able to go into the setup menu and set your speakers to small. The newer ones will allow you to set your crossover point for the sub, which will limit the frequency going to the mains. If you can set the frequency, I would set it at 80hz. Of course, if you have a sub, it will take up the slack below 80hz. That way you can continue to "experiment" without damaging your speakers. Once you get these in their enclosure, you may be able to go back in and change the setting to large, if you don't have a sub, or lower the frequecy a little for some more bottom end.

 

[tubesaregood]

Also, if you have the woofers cone facing up while they're playing, gravity acts on the cone/VC assembly and drags it down closer to the back of the magnet assembly. That's probably another factor in this situation.

 

[Psyphre]

Thx alot for the helpful replies. Both of you have made some really good points. Ive turned down the bass levels and they arent lying on the floor anymore. For the most part it doesnt pop anymore, it only occurs when I play loud music (that has alot of bass). Unfortunately this now means that there is so very little bass coming from my speakers. I hope this is simply because its not in an enclosure. Does putting woofers in an enclosure make a huge difference? Cos im a little worried these are going to be pretty 'weak' speakers.

 

[catacon]

You will be able to hear the woofers much better when you get them in an enclosure. Unless you put you ear right next to the woofer, you won't be able to hear it when it's outside of an enclosure. I believe this is because the lower frequencies cancel out much faster than higher frequencies do (I could be wrong, though).

 

[tubesaregood]

The reason you can't hear much from a speaker in free air (without a baffle) is that the waves off the front and back of the cone cancel each other. It happens with every frequency, just more so with bass. From http://www.polyplanar.com/installation.asp - "As a speaker cone moves forward, it creates positive air pressure in front of the cone, which eventually reaches your eardrums and enables you to hear the sound. At the same time, the forward movement of the cone also creates a vacuum behind the cone."

Don't worry, your speakers will sound MUCH better once they're in an enclosure.

 

[Psyphre]

Thx again. I tried experimenting. Ive screwed the drivers into the front MDF panel and to see how it might sound inside an enclosure, I sandwhiched it against the corner of the wall. WOW. Alot louder and alot more bass. In theory should sound much better once the woofers have the right volume of air. I believe this was the reason for the popping. Because when the speakers were on the open, it wasnt so loud, I therefore had to really drive the speakers hard to get decent sound. Now that they are much louder, I dont need to drive them so hard.

 

[tubesaregood]

Yup! Just be careful not to drive speakers hard in free air in the future (unless they're designed for it).