Planar Speaker Asylum

Welcome! Need support, you got it. Or share your ideas and experiences.

Return to Planar Speaker Asylum

Message Sort: Post Order or Asylum Reverse Threaded

Subwoofer behind the head

68.2.179.78
Posted on October 19, 2016 at 21:03:29
hasank
Audiophile

Posts: 2
Location: Phoenix
Joined: October 19, 2016
 I don't feel too crazy telling everyone that are in the "asylum" that the best location for my subwoofer (Relt9) to complement the magnepan 1.7's is about a foot behind my head. Short of multiple subwoofers, or listening in free space, this is the only way to get bass that sounds reasonable. So I got the maggies in front and a subwoofer breathing down my neck, but if calibrated right, it just sounds like good bass coming from nowhere.

OK, I am gonna go take my medication now.

 

Hide full thread outline!
    ...
RE: Subwoofer behind the head, posted on October 19, 2016 at 21:51:59
zulugone
Audiophile

Posts: 98
Location: Seattle, Washington
Joined: August 31, 2013
 Curious....how did you "calibrate"? my sub is about 8 feet behind me with an Oppo set distance of 22 feet with the mains set at their actual distance. All of the base sounds like it's coming out of the front soundstage right down to the position of an instrument.

 

RE: Subwoofer behind the head, posted on October 19, 2016 at 22:36:12
hasank
Audiophile

Posts: 2
Location: Phoenix
Joined: October 19, 2016
 There are only two dials to play with, the crossover, and the volume. When the subwoofer is inches away from your head, you really need to turn it down. That is what makes it good, since it does not bounce off walls and creates standing waves. It is basically near-field listening of the sub.

 

RE: Subwoofer behind the head, posted on October 20, 2016 at 05:52:33
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 No phase adjustment?

Is it a 2nd order XO? or 24db? What is the freq you ended up with?

I am wondering if sitting on the sub is getting you close to time alignment - how far are the speakers?

 

No different than being in a pimped out car. Not that I own one. (nt), posted on October 20, 2016 at 11:39:50
Jonesy
Audiophile

Posts: 3156
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since: March 1, 2018
 nt


"I know just enough to get into trouble. But not enough to get out of it."




 

RE: I like it!, posted on October 21, 2016 at 04:11:59
BigguyinATL
Manufacturer

Posts: 3475
Joined: April 10, 2002
 I once make a custom band pass subwoofer for a customer's home theater that was the the width of a sofa and the ports were on the top 5" surface of the "trapezoid".cross section. When cranking, you could feel the air move!
four 8" drivers inside, I'd pretty much forgot about it until your post!




"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

 

This is actually a great technique, posted on October 22, 2016 at 08:25:46
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 It seems that a sub right at the listener is minimum phase, which means you can equalize for flat response without bass traps -- and of course you'll get higher output from the sub and are less likely to disturb the neighbors. It's on my list of things to try, though I think I'd put my sub behind my chair rather than behind my head!

I'm also curious about the possibility of putting my midbass panels near my chair for the same reason. I'm not really sure where I'd put them, though, they have to be against a wall and there's a big opening in mine.

 

For those that know of it..., posted on October 24, 2016 at 09:47:16
grantv
Manufacturer

Posts: 7724
Location: B.C.
Joined: January 15, 2002
 A reviewer of UHF magazine used to swear by this method. As long as the subwoofer is set up right, it should work great.

 

RE: For those that know of it..., posted on October 25, 2016 at 09:06:54
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 I gather it can work for midbass as well, though you'd need two of them above 80 Hz.

 

RE: This is actually a great technique, posted on October 25, 2016 at 11:59:11
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 At midbass frequencies, won't localization become an issue?

 

RE: This is actually a great technique, posted on October 25, 2016 at 14:26:32
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Definitely, which is why you need two of them -- the issue is with lateral localization, not depth. As an experiment, I currently have my Tympani bass panels in front of the mid-tweeter panels and they work quite well there:





 

RE: This is actually a great technique, posted on October 25, 2016 at 19:20:50
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 Damn Josh, that seems like a great idea! As long as the distance between them is the same, it matters not whether the bass panels are in front of or behind the M/T's. The M/T's can then be positioned for best imaging. Love it!

 

RE: For those that know of it..., posted on October 26, 2016 at 06:51:54
grantv
Manufacturer

Posts: 7724
Location: B.C.
Joined: January 15, 2002
 I don't know... anything with directional cues (higher xover point) would likely draw attention to themselves. I think this would only work well with SUB woofers.

 

RE: For those that know of it..., posted on October 26, 2016 at 08:35:12
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 That's why you need two rather than one. The lateral cues are more significant than the front/back and height cues. As an experiment, I'm currently running my IVA's with the woofers in front of the tweeters and it works very well:



With your eyes closed, you wouldn't know that the woofers are almost at my listening position:



Also, people don't seem to have any trouble with the DWM's, which also cross over above 100 Hz.

 

RE: This is actually a great technique, posted on October 26, 2016 at 14:09:53
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 It works really well, too -- with only the 18" panel to block the reflected backwave the imaging is the best I've ever had it. It isn't all that practical in my room, though. I think my next experiment will be to separate the mid and low bass panels, then put the midbass panels on the wall to either side of the M-T panels and the put the low bass panels side-by-side near me. That would make for a more practical room arrangement.

 

RE: For those that know of it..., posted on October 27, 2016 at 09:19:48
grantv
Manufacturer

Posts: 7724
Location: B.C.
Joined: January 15, 2002
 100% agreed on lateral cues being most critical.
You need a nicer chair. :)
Nice room / set-up though. I tried hard to find TYIVA's before finally settling on my new then 3.6's.

 

RE: For those that know of it..., posted on October 27, 2016 at 12:42:37
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 LOL, if I get a better chair, I won't have an incentive to stop listening and get up. :-)

Actually, for a wooden chair, this is surprisingly comfortable. But I'll be laying in some real furnishings once I figure out where the speakers are going to live.

IIRC it took me something like six months to score those IVA's. They were an absurd bargain considering how good they are. But I wouldn't complain about 3.6's!

 

RE: For those that know of it..., posted on October 27, 2016 at 17:18:11
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 I wasn't looking for T-IVa's, but a pair of T-IV's (no "a") became available near where my sister lives, so I thought if the seller would take them across the river (from Portland to Vancouver) I could get them without the cost and danger of shipping. He agreed, and I now have them! I got them to use only as woofers, knowing that double Tympani panels reproduce bass and mid-bass like no other speaker or sub. What I didn't know, not having kept up with the wonderful world of Maggies for many years, was that the T-IV mid and tweeter drivers are still competitive with more contemporary speakers, including my own. When I get them set up I'll be listening to them both as woofers and as full-range speakers. Can't wait!

 

RE: For those that know of it..., posted on October 27, 2016 at 17:27:56
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 I've been delighted by the mid and tweeter on my IVA's. I bought them with the intention of upgrading the mids to Neo 8's, and I already have them, but I can't say I'd be unhappy with the IVA's as they are.

IIRC, you were thinking of doing Satie's Neo mod as well?

When I put in the Neos I may end up repurposing my IVA mids for surround. They really should have a rebuild -- there's some delam at the dividers -- and I could rebuild them with foil.

Right now, I have to lay in some more amplification so I can tri amp, get my Mini DSP up, and finish repairing the bass panels which have some delamination at the ends.

 

RE: For those that know of it..., posted on October 27, 2016 at 21:55:16
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 My T-IV's were at the Magnepan factory fairly recently, and had the bass drivers reglued and the other drivers replaced. Better than new! I didn't start reading this forum until after the NEO drivers had been discontinued, but found the discussion of Satie's mod very interesting. I've discussed the matter with him in pm's, and if the new NEO 8's turn out to be as good as the old ones, will seriously consider doing mine. First, I have to set them up as is, and determine if my new room here in Vancouver can accommodate Tympanis.

 

RE: For those that know of it..., posted on October 28, 2016 at 05:14:06
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 How big is your current room?

 

RE: For those that know of it..., posted on October 28, 2016 at 14:13:40
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 It's the smallest I've had in quite a while, only 13' x 14.25' with an 8' ceiling, and carpet over a suspended wood floor. The room is symmetrical, with a single 5' wide window in the middle of the long wall. It is actually a good sounding room (from what I can tell so far), much better than the 10' x 13' x 17' with bay window room I just left in California. I drew out a diagram of the room to scale (1" representing 2'), trying different layout arrangements. Placed on the long wall and firing across the width, I can get the Tympani's 5' from the wall behind them, and the tweeters 8' apart. But that will require the bass panels to be right up against the side walls. At that location they are 8' from the listening position, which will have to be only 1' from the back wall. Time for Owens Corning 703!

I have 13 ASC Tube Traps (9" to 16") and a DSPeaker Anti-Mode 2.0 Dual Core to deal with room modes, which will surely be necessary. What I would love to do is have the room enlarged, pushing the long wall out at least 6', making for a 14.25' wide by 19' long room. I'm going to look into what that would cost to have done.

This will be my final room---I moved up here to live out my remaining years in this house with my two sisters, their husbands both croaking recently, and me just wanting to hear as much J.S. Bach and Bluegrass music as time allows before I too do! So this room will have to do; if the Tympanis don't work in the room, it's alright---I have ET LFT-8b's, Quad original ESL's, and GR Research OB/Dipole subs that will suffice ;-).

 

RE: For those that know of it..., posted on October 28, 2016 at 15:01:30
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 The good news is that they'll definitely work -- my room is the same size as yours. As logn as you can give most of the room to them they're quite happy. :-) The main problem I've found is that in a small room like that they can block the back wave. I've tried several approaches with varying degrees of success, all involving splitting the woofers from the mid-tweet panels -- woofers behind and against the wall as in the manual, woofers in front as I have them now, and woofers in line but with some separation.

From an imaging perspective the best I've heard is the way they are now, with woofers in front. The mid-tweet panels image spectacularly when they're out on their own. I have a MiniDSP which I'll be using to correct the timing at which point I'll play around more but I have to la in another amp so I can biamp them. This will also allow me to tame the midbass which gets pushed up in this small room.

Something else I've been planning to try for a long time, splitting the low bass and mid bass panels. In that case, I'd try:

WALL|MIDBASS......MID TWEETER....MID TWEETER.........MIDBASS|WALL

with the bass panels joined at the back of the room, facing me from the side. This should allow plenty of room for the backwave.

And, as you say, you have plenty of backup with the dipole woofers and the LFT-8. I'm really curious about how everything compares.

BTW, I'm in the same boat you're in, sitting about a foot from the wall -- have been considering absorption there as well. I also have some QRD diffusers which I've used to good effect at the first reflection point at the front wall. I've also found that the magic position for the mid-tweet panels in my room is the point at which I'm on axis and the first reflection points at the side null out. (Of course you can do that at any position by adjusting toe in but then the crossover gets funny so I'll have to wait until I have the Mini DSP and lots of channels of amplification to try other positions.

 

separating T-4A low bass panels, posted on October 31, 2016 at 07:37:23
guitar slim
Audiophile

Posts: 168
Location: Washington DC suburbs
Joined: May 24, 2012
Hi Josh,

I'm interested in the idea of separating the low bass panels from the mid-bass. Please explain about the placement you are considering. I don't follow joining the low bass panels, placing them at the back of the room facing you from the side.

 

RE: separating T-4A low bass panels, posted on October 31, 2016 at 08:21:22
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Sorry, I knew I wasn't being very clear but it was kind of hard to explain. :-)

Anyway, my problem is this -- my room is narrow and the bass panels block the backwave, which impairs imaging. I just doesn't sound right. But I have plenty of room to fit a *single* bass panel on either side of the room.

OK, so the panels are designed to be used together to maximumize baffle width. The low bass panel is in the center and the midbass panel is on the outside. The crossover between the bass panels is acoustical, determined by the hold downs and diaphgram mass/tension.

If you separate the mid-tweet and bass panels, the bass panels are only two wide, which reduces bass extension and output. However, if you put the two bass panels against the wall, the baffle width is effectively increased, making up for the fact that they're only two panels wide.

Similarly, you should be able to put the midbass panel against the wall and still get adequate midbass output. The gap between the panel and mid-tweeters would be plenty of room to let the backwave through. But what about the low bass panels?

Since bass below 80 Hz isn't directional in a listening room, it doesn't matter where I put the low bass panels from the perspective of localization. So I can put the left and right low bass panels adjacent to one another to create a baffle width of two panels, and then put that against a wall to further increase the effective baffle width. And in my room, the convenient place happens to be off to my right, facing me.

I will have to adjust the timing between the various panels using the MiniDSP. Also, I've been calling them low bass and midbass panels, but they aren't designed to be used in this configuration so I may have to use an external crossover and bi amp them, or cobble together a high-level crossover. But for now I'm just going to run a wire between them and experiment.

 

RE: separating T-4A low bass panels, posted on October 31, 2016 at 11:05:28
guitar slim
Audiophile

Posts: 168
Location: Washington DC suburbs
Joined: May 24, 2012
Thanks for sharing your thoughts, Josh.

My listening room is longer, but the short wall behind my current speaker placement is about the same as yours, so it's pretty tight.

I'll mull over where the low bass panels might work in my room and hope to hear any more insights you get.

Maybe I could put the low bass panels the same distance behind me as the mid-bass panels are in front of me and not have to worry about adjusting the timing?

 

RE: separating T-4A low bass panels, posted on October 31, 2016 at 12:27:56
Norman M
 So you intend to separate the two 'bass' panels which come (physically) attached to each other by 'hinges'. Wouldn't you then need to improvise a method which allows for each panel to stand on its own? (Even though I'm pretty sure you are already prepared to do that, I have to wonder what they might then look like, not that looks are an 'end-all'.)

 

RE: separating T-4A low bass panels, posted on October 31, 2016 at 12:39:46
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Absolutely! As long as they're in time there's no issue. And at lower bass frequencies the timing requirements are pretty lax, because the wavelength is so long. That said, since there's no electrical crossover here, I'm not sure what will happen. I'll report back on what I find but won't be for a few days because I'm currently working on my closets!

 

RE: separating T-4A low bass panels, posted on October 31, 2016 at 12:45:39
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Yes indeed -- by my calculations, I'll be short two feet, since each freestanding midbass panel needs two but the low bass panels will be attached with the hinges so will need only two and there are a total of eight. Fortunately, Magnepan put in plenty of holes so no drilling is required.

Home Depot makes some corner braces with a hole that lines up so I got some of those as a temporary measure. This is just experimental so I'm not sure whether I'll do this long term. If I do, I can worry about nicer feet then. But I probably can't use all the standard feet anyway because in my room, the outer feet hit the radiator on the left and the mantle on the right, which is where the midbass panels will probably end up going (I don't have much choice in this room). I'll also probably want to angle the midbass panels towards me. So I'll actually end up with enough official feet and then I'll have to kludge something for those edges -- the corner braces may do the trick since they'll be behind the speakers and out of sight.

 

RE: separating T-4A low bass panels, posted on October 31, 2016 at 13:36:50
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 I am still skeptical of the idea of separating the bass panels from the midbass panels. Not just because of the loss of the reinforcement of the panels for each other but also because of low bass stereo effects you would lose.

I was very much surprised some years back when I took the infrasonic filter out from my XM44 XO. It was LR4 just under 20hz . So there is a question of how much of the problem was just phase and how much was the roll-off which was not that different - audibly - on bass instruments. What emerged as the main audible differentiator was in the hall sound and soundstage width cues, Localization of bass instruments was substantially enhanced even with just the bass panels playing (MT amps turned off).

This coincides with Linkwitz' more recent conversion about the significance of phase information in deep bass contributing to imaging. It also coincides with findings from Bodzio about the importance of timing and phase in bass as he worked his correction software to produce bass squarewaves from real speakers in real rooms. That is one of the things DEQX and Lingdorf correction software produce as well as they align time and phase.of the speakers along with room correction.

This also emerged in my own trials of wall loading the bass panels with a face forwards setup where the arrival times from the acoustic centers of the panels is spread over 200ms IIRC rather than time aligned in the arc setup and that was enough to restrict imaging performance rather significantly. Right off the bat, 1st order LP came off the table and had to be traded in for a B 3rd or LR4 to restrict the XO freq range. It just would not align well enough to contribute to imaging and made for a thick soupy sound no matter which area of the bass panel was targeted for time alignment and whatever 1st order fc was set (I had a calibrated pot for it).

Matching was much better with compensation with fc and or Q controls on the B3 LP., but I have allot of work to do with it when I do the wall loading again.
.
To summarize, I am just skeptical over the benefit of using a mono deep bass vs the possible benefit of letting through more of the back wave - which I found is quite minimal once you open up more than a few inches of slot between the bass panels and the wall, It mainly affects a sense of hall ambiance, which may be more important to you than it is for me, where I am trying to create a row 4-7 perspective on the orchestra. .

 

RE: separating T-4A low bass panels, posted on October 31, 2016 at 17:31:31
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 I remember a lecture Mitch Cotter of Ambiphon gave in the 70's at the AES in which he said precisely that -- that the ear can localize sounds down to 20 Hz using phase information. Studies find that subwoofers can't be localized below 80 or 100 Hz in a listening room, though, presumably because at those frequencies wavelengths are large(>= 10 feet) compared to the dimensions of the room. (Interestingly enough, low frequencies are also instrumental in front/back localization -- I don't remember the cutoff point.)

This really wasn't an issue in the days of LP since what bass there was was mono but it certainly could be in a digital recording.

That being said, you've hit the nail on the head -- loss of the backwave causes loss of hall ambiance and that does bother me. I'm actually listening right now with woofers on the side, in line, with some space on either side of the M-T but only 3' off the front wall (because I'm cutting that vinyl) and while the space lets some ambiance through I find the image very unnatural compared to what I get with the woofers out of the way. I think that does more damage to the image than loss of very low frequency bass information.

I have some other issues as well. My room is dual purpose and I'll need enough space between the speakers for the projection screen. Right now, my chair is about in the middle of the room so I have a good stereo spread, but I wouldn't be able to keep this arrangement because the screen would be blocked. So I'm pretty much forced into some kind of split configuration. Having the woofers behind the M-T panels interferes with the image, I've found, presumably because the midrange and highs are reflecting off the bass frames and panels. Pulling the woofers forward the way I had them the other day gives me wonderful imaging, but isn't very practical from a room layout perspective and the bass is a bit impaired because of the very acute angle.

If you remember, I was originally thinking of joining the M-T panels and the midbass panels and then combining the bass panels and putting them in the entrance arch. Well, I can't use the entrance arch because I now have to sit right next to it (or maybe I could, have to try) and I now think it's important to keep the profile of the M-T baffle as small as possible so that makes the sides the obvious choice for midbass, the midbass drivers should have sufficient output up against the wall. The low bass panels would be joined at the hip and hopefully adjacent to a wall which should also provide a sufficient effective baffle size. Since I'll likely have to add a crossover I expect some loss of maximum output but that seems inevitable given the limitations of the room, unless I can get conventional split configuration to work better than it has to date.

So -- a compromise, yes, but I'm aiming for the best I can do with the room I have, which even with this rough setup (no time correction) can be pretty spectacular. The only other thing I can think of is building dynamic dipole subs for the bottom octave and just using the midbass panels -- waiting to hear the results of BDP24's comparison. (I could try my little sealed sub at my chair -- it's there now, and I'll probably hook it up at some point -- but I think that will be a disappointment after the Tympani bass) In the meantime, more experimentation is in order. I finished installing my fireplace and the vinyl should be out of there in a few days, at which point I'll be able to play around more with the speakers and also try out try out the Mini DSP.

 

RE: separating T-4A low bass panels, posted on November 1, 2016 at 11:20:43
guitar slim
Audiophile

Posts: 168
Location: Washington DC suburbs
Joined: May 24, 2012
I think I understand your reservations, Satie.

In my case though, I could probably place the two low-bass panels directly behind the listening position, joined with hinges, with one panel angled somewhat to the right and the other to the left. If I keep the distance between all of the bass panels and the listening position close to the same, this seems to address some of your concerns. Possibly I could also have two edges of the panels against the rear wall of my listening room to get a reinforcement effect. This may not be needed, however, because I have another couple of subs that come in with a 40HZ crossover.

Just a thought experiment at this point, but maybe I should put it on the list of things to play with.

 

RE: separating T-4A low bass panels, posted on November 1, 2016 at 15:51:19
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 I am curious to find out what your experiments come up with on the balance of performance.
For my part, the separation of the bass panels is already undoing one of the benefits of the Tympani design I bought into in the first place.

Though I don't share the placement concerns over fitting a large screen (my 55"TV isn't even in the same room and I think that is plenty big) I do try to balance out imaging performance including ambient hall sound that is driving Josh to do the separation.

So far, in my own trials of the Reverse Split config (bass panels up front) imaging can get very good along with tonal balance and bass uniformity. I have not managed to get quite to the level of imaging I get in the equidistant arc and 1st order filters, but it is improving and getting closer. I will try again with the bass panels face forward on the sidewalls for wall reinforcement to see what that can do with letting through enough ambient field to retain realistic hall sound.

 

Page processed in 0.078 seconds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]