CurtPalme.com Home Theater Forum

rosenbush · Joined: 14 May 2010 Posts: 94 Location: Brownsville Texas

Let me explain, I'm planning to use two subwoofers, 18 and 12 inch, and was thinking to set the big one to cover 15 to 60 (or 70) Hz and the 12 inch sub take 70 to 120hz, I know I can set the xover frec for the 18, but how can I put the 12 just to receive from 70 and up ?
I think Velodyne did something like that on their 1812 flagship sub.
Does any one how to do it? does it make sense? worth the work? any feedback will be highly appreciated.

Ron W · Joined: 07 Aug 2009 Posts: 860 Location: Mississauga

rosenbush · Joined: 14 May 2010 Posts: 94 Location: Brownsville Texas

Hi Ron.
Yes, you're right. I'm on the basics that not every speaker can handle all the frecs. A 12" sub can not handle very well the extreme low frecuencies, for example a very low note as 30-40 hz will strain the 12" sub a lot more than an 18", It will try and sound good , but it can do even a greater job on frecs on the range 70 till 120 hz. The same will be for the 18", it will do a great job if you let him handle only the extreme lower frec's where is his especiality. As soon you set them free of the frecuencies that can not handle very well they will focus on theirs best. As happen on the rest of the speakers of the system, they will take the other frecuencies where the subs left them, they will play the range above 120hz.

I agree 2,3 or 4 sub's will sound amazing if you take care for placement, setting up etc. Just wondering what will happend if you let every sub in their best range performace.

greg_mitch · Joined: 03 May 2006 Posts: 5320

I don't think you should artificially put constraints on the subs. They will inherently have their own unique frequency response. Playing with placement and taking some pretty basic measurements you should be able to get a decently flat response all the way from the low tuning point of the 18" up through the crossover point to the main speakers.

There are hundreds of discussions about multiple subs on several forums. You will get 100 different opinions too. Wink

Ron W · Joined: 07 Aug 2009 Posts: 860 Location: Mississauga

[quote="rosenbush"]Hi Ron.
Yes, you're right. I'm on the basics that not every speaker can handle all the frecs. A 12" sub can not handle very well the extreme low frecuencies, for example a very low note as 30-40 hz will strain the 12" sub a lot more than an 18", It will try and sound good , but it can do even a greater job on frecs on the range 70 till 120 hz. The same will be for the 18", it will do a great job if you let him handle only the extreme lower frec's where is his especiality. As soon you set them free of the frecuencies that can not handle very well they will focus on theirs best. As happen on the rest of the speakers of the system, they will take the other frecuencies where the subs left them, they will play the range above 120hz.

I agree 2,3 or 4 sub's will sound amazing if you take care for placement, setting up etc. Just wondering what will happend if you let every sub in their best range performace.[/quote

Hello:

Since you will find that most subs of good-high calibre have 12 inch drivers, unless for some reason you are playing the movie and/or music at very high volumes, this size sub should handle frequencies in the 30-40hz range without any problem. All my subs have 12 inch drivers with 250-350 watt amplifiers and they will go at or below 20hz without any issues, IF the movie or music has sound in that frequency range. MOST DO NOT. As I mentioned before unless you have very small speakers in the other channels, setting the crossover at 120hz is too high. Just set the subs up like they were both the same making sure the volume is balanced with the same crossover and proper phase adjustments. That is the best way to go otherwise you are wasting the usage of the 12 inch sub in that setting an unusually high crossover will pinpoint where that low frequency sound is coming from. That is something you do not want. I mentioned earlier 80hz is the most frequently used because it is the THX standard for movies.

I must say having said all that, I doubt there is a sub out there that will enable you to do what you are trying to do. Generally all subs today are designed in order to best match the speakers in your other channels is to have variable crossovers to limit the high frequencies entering the sub, NOT limit the low frequencies. That is just defeating the purpose of why one has a sub in the first place.

rosenbush · Joined: 14 May 2010 Posts: 94 Location: Brownsville Texas

Updated: In theory, it may work put every sub in their best frec response. In real world, there are mayor issues that affect the performance and sound quality: location, calibration, volume, balance low frequencies when using two or more subs, etc, that reflect at the end in better sound, as some of you wisely comment.
After some experiments, there is no real change in sound quality putting the filters on low cut on the 12 sub, however, in my particular case, will help when you play loud and there is a significant change of volume, like on a movie explosion, crash or something like that. In fact the 12 sub suffer in a "Das-boot" scene in a very low notes. I played again the same scene with the filters on and there was a great positive change. There was no distortion and still the sound quality was great. At the end: Will not help on sound quality, but it help to avoid distortion in certain cases. Thank you all.