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2 Subs...same specs necessary?


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#1 of 16 toddbigeasy

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Posted October 16 2012 - 03:19 AM

Hello, I apologize if I have over simplified this question.. my current sub spec is 10" @ 250w, if I add another ( AVR is Onkyo TX-SR608 7.2) sub, would it matter if I go with a larger sub, 12" or even more watt spec, say 400w? or should I shoot for the same spec sub? Just curious, before I go shopping for my second sub, I appreciate your input! thanks, Todd

#2 of 16 Jason Charlton

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Posted October 16 2012 - 04:09 AM

Generally speaking, one good sub is better and easier to set up than a mix of two different subs.


Certainly, if you are not satisfied with the frequency response/low end of the current subwoofer, adding a second identical subwoofer will not magically make the system go any lower.


Also, it's important to realize that the ".2" is a misnomer - all it really means is that the receiver has an internal splitter for the soundtrack's MONO LFE channel (the ".1" in 5.1 and 7.1).  There are no modern digital soundtrack formats that encode a stereo LFE track.  Any ".1" receiver can be converted to a ".2" receiver with a simple RCA splitter cable.  So don't assume a ".2" setup is "twice as good" as a ".1" setup.


Subwoofer performance is very dependent on placement and room geometry.  Proper placement and setup/calibration would be the FIRST step in trying to improve your system's performance.


Placement is key because every subwoofer is going to have peaks and null were you to plot the SPL/volume versus frequency response.  Proper placement can help "flatten" the curve - reducing the boomy peaks and boosting the missing nulls to provide an even response.


Adding a completely different subwoofer to the mix (with different size driver, different frequency response) could potentially add a whole new slew of peaks and valleys (different from the first sub) that will need to be dealt with.  Proper placement of the second sub, may also adversely affect the performance of the first sub and vice versa.


What is your budget for the new sub?  What is the current subwoofer?  You may be better off selling the current sub to boost your budget.  There are some very good performers that will work for small to decent sized rooms for ~$200 and up.


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#3 of 16 schan1269

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Posted October 16 2012 - 04:10 AM

The .2 on your Onkyo is "window dressing". You only have 1 control over subs. (that is like "every other" piece of AV equipment not priced $2500+ and called Integra though) No, it "does not matter" if the sub specs match. But... It will very likely mean the "bigger sub" will make the smaller sub "useless". Unless you run a x-over network between them and make your "original" sub a MBM(get to that here in a second). There is a school of thought(we don't know what crossover you are using...nor your mains) where you add a MBM to complement your sub. Most subwoofer than can "dig deep" to 25hz and under tend to "chuff" around 60hz. Chuff is bad. So, you add in a MBM(mid-bass module) to carry off at 50hz to 80hz(or whatever the crossover is that your mains need).

#4 of 16 toddbigeasy

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Posted October 16 2012 - 04:25 AM

Thanks for the replies, very imformative! I will cut and past to keep that in my files. It's not that I'm unsatisfied with my current performance, Just thinking of 'next steps' , recently completed my all Klipsch Icon series 7 speaker system. (added the 2 tower KF-28s yesterday, they all sound wonderful together, very 'at the theater' like...I'm happy) The sub is a Klipsch Synergy SUB-10 200 watts (quote:The subwoofer's built-in, steep-slope (24dB/octave) low-pass crossover is continuously adjustable from 40 to 120Hz.) I realize there are better performers out there within my foreseable future budget (maybe next spring). Just pondering... If I get a 'better performer', should I add it to my current sub, or ditch it.. I have plenty of time, to re-position, re-calibrate, etc.etc. in the mean time thanks again! Todd .

#5 of 16 schan1269

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Posted October 16 2012 - 04:33 AM

When it comes to subwoofer, there is "never too much"... It is why they come with gain knobs...

#6 of 16 Robert_J

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Posted October 16 2012 - 06:23 AM

Adding an identical sub will just give you the potential 3db to 6db of headroom depending on placement and a little less distortion. But it won't play any lower than what you have now. If you want better performance (lower extension) then ditch the Klipsch and go with a better sub. And like Sam says, there is never too much sub in a properly calibrated system. You just have additional headroom and lower distortion.

#7 of 16 BraveHeart123

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Posted October 16 2012 - 10:23 PM

I would also like to add my 2 cents here.....Pls diffuse the myth that two subs must be identical should you choose to go this route. Your room is your biggest nemesis. Even the best of subs perform below average coz they are at the mercy of room acoustics. I am using two poles apart subs in my room. Um running a Klipsch Sub-12 and a DIY Pioneer (TS-W2502D4 800watts rms and 3000watts peak 10 inch) in slot port design. Both have different FR, driver size, wattage, etc. My bedroom is one of the most unforgiving in terms of room acoustics. My problem was that I had only two potential spots in my room to place the sub i.e. left and right corners of front wall. If I put SUB-12 in left corner, the low FR (50Hz and below) was all cluttered with dips and peaks but mid bass region (50Hz to 80Hz) was smooth. If I moved the sub to the right corner, I would have strong and smooth FR in low and ultra low regions, but mid bass would be all ruffled up. So I decided to go DIY route and that too with 10 inches sub. BTW Robert_J helped me a lot in my project; though it was different sub and a sealed box, but I used the same knowledge and used Pioneer sub instead in an L-shaped slot ported design. I put the DIY pioneer in the left corner where mid bass region is smooth. And put SUB-12 in the right corner where low / ultra low bass was smooth. I am firing Pioneer with Crown XLS-1000 in High-Pass bridged mode with HP filter set at 50Hz. Also, I've set the low pass filter on the back of SUB-12 at 45 Hz. I crossed the mains at 90Hz on AVR (Onkyo 809). So, effectively what's happening here is the avr routes 90Hz and below to the subs, but Pioneer plays from 90Hz till 50Hz and below is filtered with 24dB per octave Link-Witz Riley built in HP filter in Crown XLS-1000. Klipsch SUB-12 is only playing frquency below 50Hz, though I set the LP filter to 45Hz on the back of the sub. The reason is there was a huge dip at 50Hz, where SUB12 and Pioneer crossed. So I moved the crossover to 45Hz and effectively reduced the dip quite a lot. Now the transition is as smooth and silk and the bass is so strong; it can knock down the walls. For your info, um attaching the combined FR of both subs; Combined Response of SUB-12 & Pioneer in REW Green line is the smoothed out House Curve response of both subwoofers using BFD filters. Other is the raw response. See the transition between both subs in (45-50) hz region. It is as smooth as silk. There is a dip at 73hz, but that's coz my DIY box design is far from perfect. Bass Energy Distribution In Room (REW) Look at how evenly the bass energy is distributed accros the low end; Note: I had to use ART CleanBox Pro line level converter to bump up voltage on Onkyo 809 sub-out (200mV) to match input sensitivity of Crown XLS-100 (1.4Volts) coz it's pro amp and works at its best on a minimum of 1.4Volts. Result Robert_J is right. He is a big proponent of DIY subs here, but i wasn't too sure untill I heard it. The bass slam is so hard and strong that you feel it will damage your rib cage. Also, there is no hint of boom at beyond reference volumes. And mind you this model of Pioneer is not at all suitable for home use as it has 1/3rd the xMax (linear excursion), but Crown is literally pushing the cone to extreme limits. Also I've hooked up both it's voice coils in parallel for 2-ohm load. Crown pumps out 1100 watts in bridged mode for 4ohm load. But still the bass is massively huge and tight. Also, do not worry about the necessity of same specs on multiple subs. It all boils down to what you want. If you want great music, you need a fast sub i.e. 10 inch max. If you want great movie experience, u need 12 inch or bigger drivers to give u depth and control. If you want the best of both worlds; add a 10 incher for mid bass and (at least) a 12 incher for sheer depth. Both subs should handle different frequency spectrum. I knew exactly what I wanted and um extremely happy with the results. I reckon u go DIY route and I'm sure Robert will be more than happy to help u out on this.

#8 of 16 Jason Charlton

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Posted October 17 2012 - 01:28 AM

Originally Posted by BraveHeart123 

Pls diffuse the myth that two subs must be identical should you choose to go this route.


Faisal - thanks for your input.  Your "story" on this forum has been a fascinating one to follow, and there's a LOT of great useful information to be gleaned from reading it.


However, I just want to reinforce that I don't believe anyone (myself included) suggested when adding multiple subs to a room that they must be identical.  It was simply pointed out that when it comes to multi-sub setups the implementation of two different models is likey to be a much more involved and technically challenging proposal.


Use of BFDs, "tuning" of in-room responses, multiple crossover settings, using one sub as a mid-bass enhancer, etc. while all very valid and useful tools that should absolutely be considered for squeezing every ounce of potential out of a system, we need to keep in mind that not everyone (the OP included) is necessarily interested in going that far.


Ultimately, it's up to Todd how far he wants to go with this - but I do think it's valuable for him to know the extent of his options either way.


Cheers!


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#9 of 16 toddbigeasy

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Posted October 17 2012 - 01:48 AM

Thanks everyone! This opens up a whole new world to me when I venture into 'next steps' for my HT. Looks like fun. This will most likely not occur until next spring or so, so I have a little while to research, and read, and plan, all fun stuff for sure! I will copy and past this info into my HT folders for reference for sure. I watched Battleship last night and my new system sounds great to me, but I am lacking that really deep rattle your rib cage that I would like to achieve, but I'm happy enough for the time being... Talk to you soon thanks again! Todd oh... btw, I noticed Robert is in Southaven, I'm in Bartlett!

#10 of 16 BraveHeart123

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Posted October 17 2012 - 03:23 AM

Use of BFDs, "tuning" of in-room responses, multiple crossover settings, using one sub as a mid-bass enhancer, etc. while all very valid and useful tools that should absolutely be considered for squeezing every ounce of potential out of a system, we need to keep in mind that not everyone (the OP included) is necessarily interested in going that far.

Like I said in the beginning, "Just my 2 cents." I would love to go this far coz it's all fun. I am engineer myself, though in different field, but I hate black box theory. I love to disect stuff down to granular level and then do something different with it. I recently installed a USD 1800 SuperCube Reference for my friend. We had it shipped from Dubai coz we don't have this here in Pakistan. Apart from sc reference, he has exactly the same stuff as I do. My USD 900 sub duo simply blows sc ref out of the water. Anyway, on a side note all good sub companies cost an arm and a leg. If u just think deeply, it's just an mdf box, a driver, and an amp put together in certain unison and they charge exorbitant amount for covering such a tiny frequency spectrum. If they can do; so can anybody. All the DIY proponents talk about DIY route for a reason. It's easily doable. And there is no match to DIY sub performance. Just my opinion.... Also, I was a novice 2 years ago when I bought my first HT. Didn't know anything and was just groping in the dark. I learnt a lot on this forum. So, I feel pushed to contribute to this forum so others can also learn and apply a thing or two out of my experiences. Have fun

#11 of 16 Robert_J

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Posted October 17 2012 - 07:23 AM

oh... btw, I noticed Robert is in Southaven, I'm in Bartlett!

If you ever get down this way, let me know. I'll be glad to give you a demo of dual 15" subs that are flat to 15 hz. I'm closer to the Southaven / OB line than I-55.

#12 of 16 tubeman

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Posted October 20 2012 - 05:01 PM

Hi, I have used 4 subs for 15yrs plus , vel,willson,genesis,whise,revel and 18inch subs with Mal x driver x2.(built for me).always in 2,or 4 of the same sub. 1st you need to decide what you what to achieve,how low,how loud and size,s of sub,s.Generally you would not mix ported and sealed ,it can be done if a high quality ported sub.(wilson watch dog,s worked well with other sealed subs I have/had Revels/Genesis etc.For most go for 2 larger subs 15/18inch depending on your goals.(My system is flat to 10hz,but will add 2 tc LMS 5400 subs to the mix soon with a nice 4kw each to improve below 20hz.) I don,t recommend more than 2 subs unless you have a large budget,better to improve front stage,amps projector etc first . cheers.

#13 of 16 beatmixer0097

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Posted December 03 2012 - 03:13 AM

Hi there So I think you answered my question but I have two def tech tower speakers that have built in 10" subs. I "thought" my Sony ES receiver was a 7.2 but in fact only 7.1. I figured I would look to get an actual 7.2 product so my speakers sound better and I get more LFE. Well then I thought to myself, wait, what movie soundtracks are recorded in 5."2" let alone 7."2". I'm guessing there is no advantage to getting a .2 receiver - Thanks Michael

#14 of 16 Jason Charlton

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Posted December 03 2012 - 03:30 AM

Unless the price difference between the ".2" and ".1" receiver is less than the cost of an RCA splitter like this: http://www.monoprice...&seq=1&format=2


Seeing as how the splitter costs $0.39, it would be hard to justify spending any more on a receiver simply because it has that little doohickey on the inside...


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#15 of 16 Wayne A. Pflughaupt

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Posted December 03 2012 - 11:06 AM

I would also like to add my 2 cents here.....Pls diffuse the myth that two subs must be identical should you choose to go this route.

The reason your experiment went well is because your two subs are essentially functioning as a single entity – one doing low bass, one doing high. That’s an unusual situation that not many people do, so I wouldn’t say your experience translates to a blanket refutation of the “multiple subs should match” mantra. There indeed are problems when trying to use two mismatched subs – “mismatched” being one with excellent extension and one with poor extension. You can see the graphs in this thread that show how mismatching “dumbs down” overall response to the level of the lesser sub. Regards, Wayne A. Pflughaupt
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#16 of 16 BraveHeart123

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Posted December 03 2012 - 05:03 PM

Your are absolutely right Wayne.......I gave it a hard thot the other day and realized that both my subs are serving different frequency spectrums, so the fact that u experts reiterate on holds. My bad :)




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