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View Full Version : differnt sized subs in the same box(running an 8" and 12" in the same box)



Jroo
12-03-2012, 11:39 AM
Any of you ever heard a box that had different sized subs in the same box and sound good? Over on PWK there is a build thead where a box has a ported 8" alpine and a ported 12" alpine in the same box pointed to the rear. Each sub looks like it has it own air space and port, but I thought you still could get some cancellation from this? Not worried on opinions about PWK as I know some think he sells snake oil and unicorns! Back in the day I remember a local shop tried this and said it didnt come out as planned, but dont know specifics on the box or subs they used.

If this works, it could be an answer to my issue of not being able to find a decent spot for some good hard hitting midbass. Im thinking run the 8" from 150hz down to 60hz and let the 12" or 15" run from 60hz down to 25hz. Two seperate mono amps for each and keep the same family of subs so you dont have a sound difference. I would run a good set of comps up front and let the box and some time alignment take care of the rest. You folks see any issues with this?

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brandon_s0854
12-03-2012, 11:41 AM
I believe if you have them covering different frequency ranges and separate airspace, it can work very well. I've never personally done it, but heard a system a few years ago with that type of setup that sounded quite good.

Jroo
12-03-2012, 11:46 AM
Yeah Im thinking it could work for me. I dont want to cut my doors or floor to try and get a larger midbass in. If I stay below 150hz, I dont think I would get any localization of the 8" playing in the rear? I guess that is more the question? I then could set my 5.25 play where they really want to play from.

brandon_s0854
12-03-2012, 11:50 AM
I would think there'd be very little localization in that range. Unfortunately, I can't give you a definite answer because I've never ran a setup like that.

Jroo
12-03-2012, 01:17 PM
Thats what I hope. Any of my box designers care to chip in.

ShowtimeCrAudio
12-03-2012, 01:25 PM
If they are in their own chambers, they are technically not in the same box are they?

Cancellation is not really an issue. People talk about cancellation but I think that is because they may not understand what is really happening.

When 2 sounds are present in the air at the same time, they may interfere with each other.
How they interfere depends on what sounds and how those sounds are produced.

Many systems have subs, mids, tweeters. These drivers are crossed over but some frequencies do overlap. There is not much cancellation with this but what does happen in some cases is a phase alignment issue.
This means that some frequencies can be louder than others and I think this is where the notion of cancellation comes from.
There are multiple ways to alleviate this.
1. Crossover at certain frequencies on each driver at a high slope. 24db Per octave for example.
2. EQ adjust each frequency carefully.
3. Phase/Time adjust each driver.
4. Tune a single woofer to a wider frequency range and do not use a mid-bass.

Jroo
12-03-2012, 05:14 PM
First let me be honest and tell you that I have always been a sealed guy, so I may have some ported questions. I am asssuming that the 8" has a higher port tuning and the 12" has a lower port tuning? I say this becasuse I assume you want the 2 drivers to peak around certain frequencies and start dropping off or xover below that to make this box work?

audiobaun
12-03-2012, 05:31 PM
I would think that for you needing Midbass, that it shouldnt be in the same location as the subwoofer,but more up front where the components are, or mid way from the rear, not at the rear where the sub is..Doesnt seem like very good staging,As far as Bass goes,why not??

Imtjnotu
12-03-2012, 05:50 PM
the 12 will drown out any midbass ur hoping to hear...

Jroo
12-04-2012, 10:36 AM
Im was worried like Audiobaun said about the staging issues but have been told you really cant localize from 150 down. I was told that over that when you start getting mid bass in the 200 and 300 range up, you can certainly tell where it is? Thats what I have been told and open to opinions. I dont think the sub would drown out the midbass becasue the sub is only picking up from lets say 60 down. Correct me guys, but the midbass and sub really shouldnt be fighting or competing against each other if the xover points are done right? At this point, its all theory until I build it or hear from the guy on PWK.

wickedwitt
12-04-2012, 11:13 AM
Originally it was thought there is no staging from 200hz down, but there are some SQ guys adoption the ideology that staging needs to be done all the way down to 50hz. Up to you though, I think the SQ guys are just splitting hairs (like the audibility of notes under 20hz, works for some not others).

TJ was right though, having them both back there firing in the same direction, the 12 wave is going to drown the 8 wave out. You will never hear the 8 even if it is playing a different frequency range. It needs to be brought up closer to the listener so that 12 doesn't demolish it's output.

04murdalanche
12-04-2012, 11:21 AM
no

mlstrass
12-05-2012, 03:43 AM
Without some TA I would imagine the 8" playing up to 150Hz would be very easy to localize. Other then that I think you could make it work. Not sure how the 12 would drown out the 8 when they're playing diff freqs. Assuming the 8" has enough power then that would be the least of my worries...

Bettr n' Revrse
12-05-2012, 03:46 AM
No

Jroo
12-05-2012, 10:18 AM
For those saying no, can you give a little more to your answer. I really want to learn on this one. So I am finding something funny about the answers I am receiving here and another place. The guys that are more into sq say it will work but just worry about localization of the 8". Guys who fall into the loud side say no it wont work.

Jroo
12-07-2012, 02:36 PM
So it looks like experiment time. Over xmas break, I will be forced to the shed to pull out my JL 18w6 and go buy a set of the JL ZR 800-cw's to use. People swear the midbass on those is stellar and I can find them online for 130 bucks now. I run both boxes sealed and play with xover points to see if I can get them to play together and sound ok. I mess with ported on the midbass later if I dont get output I like sealed. Rough Idea is run my 18w6 on my Rockford 800a2 from 50 down. Run the 2 zr 800s off my my JL 300/2 from 50 to 150 give or take. Then run my good old trusty JBL 504s GTIs in the door off my JL 300/4 from 150 up. All xover points subject to change based on how much this sounds like crap or sounds good. Ill throw in a little bit of T/A from my Eclipse 8454 and see how it works. What you think so far?