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Post by norpus on Oct 1, 2006 18:12:14 GMT -7
Have any/many of you built a second IB sub to supplement first or to tame room nodes? Has anyone built a second IB in the rear of the room also, a la Harman white paper? I am considering making another hole in my floor at the rear wall centre to assist the 2x18" Avalanche in floor sub at the front (centred between mains, in floor). As I have plenty of output from the front IB, the second would be smaller (Avalanche drivers not avail any more) and I was thinking 2x12 (18mm xmax) or 2x15 What pitfalls should I watch out for? (apart form the dog catcher hole in the floor ) I have experienced a nicer response (unfortunately not measured) earlier on (prior to IB) with 2 boxed subs (versus 1) when the room was configured very differently. I had read the Harman paper and tried it out - one sub at centre front and 2nd at centre rear. www.harman.com/wp/pdf/multsubs.pdfMy family room in 2ch critical listening mode. Most people can't find the IB when asked where is it www.dtvforum.info/index.php?s=&showtopic=29168&view=findpost&p=496015I currently crossover using a Behringer CX2310 at 60Hz at which it has been measured and EQed. I'd be happy to take it down to 44Hz also (the CX2310 limit) as it also sounds good there. A Recalibration will obviously be necessary when 2nd IB completed at a range of listening positions. Hopefully the sweet spot for listening in 2ch will have beeen widened also. HT oomph may also be assisted but that is not the primary goal.
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Post by ThomasW on Oct 1, 2006 21:01:44 GMT -7
This is one of those situations where you're pioneering fairly new territory. I'd start off build a sealed box sub and play with it in the back. If you like what it does and you get what you want then to go for an IB.
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Post by norpus on Oct 1, 2006 21:30:02 GMT -7
This is one of those situations where you're pioneering fairly new territory. I'd start off build a sealed box sub and play with it in the back. If you like what it does and you get what you want then to go for an IB. Yippee the final frontier! Noone else has done it? Mmmm I did have my old B&W ASW1000 set up in the same position for a very short time, but there were two problems. 1. the 12" box sub couldn't keep up with the big IB and sounded muddy - it is only good for 30Hz in room response from curves I have seen from others. 2. there was a hum loop generated somewhere in the system when the rca was run under floor to the back sub - which I couldn't stand so disconnected the experiment fairly quickly. Thanks for the response Thomas. You have now added a straw to the back of my mischievous camel. Its got to be done now. Gotta love being a pioneer ;D
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Post by jman on Oct 3, 2006 21:36:02 GMT -7
Phase alignment will be critical.
My friend has a pair of contrabass subs. One time he tried 1 at the front, 1 at the back and they weren't in phase. In the LOTR TTT, in the scene where they smash the battering ram into the doors I watched as his 400W x 2 amp meters both hit 0db but we heard almost nothing.
1 IB at the midpoint of each wall would be the ideal according to the Harmon Kardon whitepaper. They used sealed subs but the results are just as valid for IB.
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Post by norpus on Oct 4, 2006 5:25:25 GMT -7
Thanks for the reply jman Yes that is the positioning of choice I'm kinda surprised if noone else has done this with IB before
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Post by jagman on Oct 5, 2006 11:18:36 GMT -7
There has been a lot of talk on various forums but nobody seems to have the stones to try it. I'm one of those people . The Harmon white paper is rather convincing. My take is it is absolutely worth doing if you can find a way to control the phase of the rear sub (continuously variable 0-360) vs the front end (Ave IB and mains). I'd also cantact Chad to see if you can get your hands on a few more Aves. Even if they are 15's or even 12's they are more likely to be sonically similar to the 18's up front. Who knows... you may become the envy of everyone here!
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Post by norpus on Oct 6, 2006 4:31:06 GMT -7
Yesterday at 12:18pm, jagman wrote:There has been a lot of talk on various forums but nobody seems to have the stones to try it. I'm one of those people . The Harmon white paper is rather convincing. My take is it is absolutely worth doing if you can find a way to control the phase of the rear sub (continuously variable 0-360) vs the front end (Ave IB and mains). I'd also cantact Chad to see if you can get your hands on a few more Aves. Even if they are 15's or even 12's they are more likely to be sonically similar to the 18's up front. Who knows... you may become the envy of everyone here!
Cool, thanks so much for the reply jagman. Very encouraging. I have a week off from now and it is earmarked for diy HT jobs (mounting new pj, assembling and mounting a diy constant image height anamorphic lens, trace and remove an annoying hum loop) So even if I don't have the drivers, I'll be building a manifold and prefitting it next week. I'm excited
Regarding the phase control, I guess there will be a behringer unit that can help me. Any ideas which one? (I currently use MX882, CX2310 and FBQ2496)
I'd like to contact Chad as you suggest. What is the best way please? Can you pm me his contact details please?
Sorry once again I hit the edit button instead of the quote...
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ken
Full Member
Posts: 187
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Post by ken on Oct 6, 2006 15:09:03 GMT -7
Norpus......l have chads phone number.l'll pm you on dba with it ok...cheers Ken
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Post by ThomasW on Oct 6, 2006 17:05:38 GMT -7
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Post by jagman on Oct 6, 2006 17:30:53 GMT -7
A far more expensive option would be to get the Velodyne SMS-1. It comblines an auto parametric EQ with independant control, including phase and time delays, for up to 3 mono subwoofers. It would be very easy to implement, but it doesn't have the EQ flexability of the Behringer FBD. You can check out a very thorough discussion of it here. It has it's own share of problems, but like I said, it's easy to use and with dual IB's you may not need much room correction (especially if you have passive acoustic treatments in your room). One thing of concern is it has a rumble filter at 15 Hz. I've read in places that may be changed, but I don't know if the change has been implemented.
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Post by norpus on Oct 9, 2006 15:16:15 GMT -7
I have listened to peoples advice here re the current power and lack of phase control on my front IB. Thankyou. I also had a smart young electronics engineer who builds amps (SGR) around last night who explained time alignment of drivers to me in language I could grapple. Based on this, I will be likely now upgrading the Behringer A500 to 2 x 500w class A/B monoblock sub amps with phase control www.dtvforum.info/index.php?s=&showtopic=41138&view=findpost&p=491830So that should feed the 2x18 Avas the good oil with plenty of dollops of cream The A500 will now see rear action duty and I'll need to work something else out for phase alignment of that as has been suggested. Maybe another behringer unit such as the DCX2496 or something else. Will build this week and see what's needed
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Post by norpus on Oct 10, 2006 5:28:39 GMT -7
Bought 2 Tempest 15D8 today and will be making manifold starting tomorrow. Not much choice of available drivers here in Melbourne at short notice - only really the Venom 15" and these
will see how they go, and if need better drivers later, can always swap out
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Post by jagman on Oct 10, 2006 9:24:27 GMT -7
Keep us posted!
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Post by jagman on Oct 10, 2006 10:44:45 GMT -7
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Post by norpus on Oct 11, 2006 21:30:37 GMT -7
Yes, ken s (kesa) alerted me last week but I couldn't find said auction site. Also importing to Aust is slow and exxy, so went with Tempests as they were avail. Have chopped hole in floor today - ended up being bigger than designed (again) because found some bearers under the floor that got in the way of original side front to back firing config - so now side firing. Hole is now 510mm square. Need to build box tomorrow. too warm and the beer too inviting today
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Post by norpus on Oct 12, 2006 16:45:07 GMT -7
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Post by ThomasW on Oct 12, 2006 17:40:20 GMT -7
You of course realize you cut a doubled load-bearing joist?
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Post by norpus on Oct 13, 2006 0:29:35 GMT -7
Its not a problem, we built the room as an extension and its very solid - the doubling up just was for the join between old and new. Thanks for the concern tho. We have also replaced the floor joist alongside so box/floor will be braced well
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Post by norpus on Oct 13, 2006 19:46:38 GMT -7
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Post by norpus on Oct 15, 2006 4:44:46 GMT -7
New rear sub is installed
Initial observation would suggest a xover at 44Hz (running 1 rear sub only, no front) is quite musical and bass is not locatable
Need to get an extra amp to be able to power both at same time now. Will report effect of two soon when able
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