Folks:
I think this 2-channel area is a great idea!

I have separate HT and music areas in my house. For my music system, I have:

Magnepan 1.6s
B & K Reference 4420 Dual Mono Amp (350 watts @ 4 ohms)
Outlaw RR2150 using preamp outs
Pioneer DV 45A disc player (DVD-Audio, SACD, CD)
Techics SL 1210 MK II Direct Drive Turntable with a Shure M97xE cartridge

My current dilemma is that the Magnepan speakers do not seem to do justice to the low end. They are rated down to 40 Hz (for whatever that's worth) but a stand-up bass (for example) doesn't come across with as much authority as it should. So, I'm thinking of a subwoofer to "reinforce" the low end of the Maggies. The Outlaw receiver has a subwoofer out and a bass management filter that will send everything below 60 Hz to the subwoofer. The room this is set up in is BIG - 17' X 30'.

What I need is a subwoofer that can do 60Hz to 20 Hz quickly enough to keep up with the Maggies. I have been looking at subwoofers (slowly, as I don't live in an area with high-end bricks & mortar stores) and from what I have heard so far, REL (not sure what models to even think about) and the Vandersteen 2WQ are contenders.

What I don't need is an HT subwoofer that booms. I've got a HSU VTF 3 MK II in my home theater and I tried it out in the music system but I was having real problems getting it to "reinforce" - it either seemed too loud or didn't seem to make any difference at all.

FWIW I have tried this in the subwoofer forum but got sheer nonsense from HT-centric folks. I also tried the Asylum but their advice was not helpful either. Hopefully here I will get someone who also has Magnepan 1.6 speakers or else someone who can refine my search (e.g., which model REL to focus on listening to...).

If you wan't bass that blends well, you also need to evaluate the room[acoustically] for placement. There is no quick fix here with a single model or placement. Room treatment and or EQ can go a long way with many brands and models, and box type.

Thank you hun. Room treatment is always important.

However, my concern is with which subs to start with and I was hoping to hear from someone who knew more about the design criteria for different brands/models of subwoofers and/or someone who had experience addressing the same concern for reinforcement of the bottom end of planar speakers like the Magnepan 1.6.

This may not be a solution for you, but the only sub that I found to blend with my Maggies (3.6R and 1.6QR) was an IB that I built myself. The IB is nearly a perfect match with the Maggies in my room. I've been told that a dipole sub is an even better match, but I've never actually heard one myself.

dg:
Thanks for the suggestion. I have been reading about IB for a couple of years. My problem is that my house is a split ranch and all the spaces surrounding my HT room are either impossible to employ (e.g., below the room is six inches of concrete and then dirt) or else there is another room. The cost of re-doing two rooms to create enough space for the IB is prohibitive.

How about in the ceiling? That's where I put mine and I did the work myself. I'm not all that handy, or all that bright for that matter, so just about anyone should be able to put one together. :D If that's not an option, take a look at some of the DIY dipoles. I would have gone with a dipole if I had the floor space.

It's no secret that the wonderful midrange of maggies comes with the sacrific of good solid bass. When I had my MG-20s, I started out with a pair of 15" woofers that were just plain to slow for the fast action of the maggies. An aquaintance of mine, who also owned maggies suggested the need to always stay with 10 inch or under drivers for subs....even if you have multiples of them in one cabinet. His subs were custom built with 4 8 inch drivers per cabinet The sound was pretty much what I was looking for so I had some custom built as well...though with smaller cabinets. That was a while ago.

With all the subs on the market today, there's bound to be one that will work for you. I'd be careful though not to assume a sub will work great in an audio system just beacuse it gets rave HT reviews. That being said, with 1.6s, you probably don't need much to fill in the bottom end if it's done right. I would look at the low end of SVS as a place to start. Second, I would look at some of the pre-HT era sub mfg's such as Bag End, Velodyne, or the older cylindrical Hsu subs of say the mid 90's. Some of those old subs are still around and can be had for pretty good prices today. I really don't think you'll need much more than that.

How and where you cross-over is going to be a big big factor. At the time, I used a Bryston 10b. I believe I was doing 12dB/octave at about 120Hz. Anything lower than that always left a hole on the mid-bass.

Thank you hun. Room treatment is always important.

However, my concern is with which subs to start with and I was hoping to hear from someone who knew more about the design criteria for different brands/models of subwoofers and/or someone who had experience addressing the same concern for reinforcement of the bottom end of planar speakers like the Magnepan 1.6.

Well that figures, then why don't you seek out subs with low Q and short spectral decay, those should be able to "keep up" with the Maggies just fine.
You find those on "small" sealed designs mostly.

I suspect your booming problem has a lot to do with sub placement and stacking room modes at the listening position. There's nothing wrong with what're stereotypically considered HT subs considering that depending upon your music, you can have substantial low frequency energy. However, I think a sensible approach at this time would involve learning how to better integrate your HT sub into your listening environment. That's going to take software, a microphone, and a learning curve. The knowledge you glean from that can then be applied to your 2-channel setup.

How about in the ceiling? That's where I put mine and I did the work myself. I'm not all that handy, or all that bright for that matter, so just about anyone should be able to put one together. :D If that's not an option, take a look at some of the DIY dipoles. I would have gone with a dipole if I had the floor space.


dg:
Above the room are bedrooms and there's little space... Thanks for the suggestion though.

Folks:
Thanks much for the comments. I think I have a better idea how to proceed now. hun's suggestion of low Q and short spectral decay focused my thinking. And, of course, I'll use my BFD to help me position it and analyze room treatments. I'll let you know...

I had the ACI Titan 2 LE and it had 2 12db/octave crossovers which you could set independantly to craft your own overall crossover curve. This enabled excellent integration into my speakers. I compared the ACI to B&W ASW675, James EMB1200, and a few other subs, and for the money, I decided that ACI was the way to go for sound quality, extension, and cosmetic reasons. Perhaps, you can shoot ACI an email to see if they answer your questions the way you want them to :)

Their website is www.audioc.com

Jonomega:
Someone from ACI contacted me about their products (including a review where the speakers were Magnepan 1.6s!) and I have added them to my "short list." Thanks for your reinforcement of that path.

Hello Mnilan, I have the same speakers as you 1.6QR, and I have been extremely happy with my Velodyne DD-12. It blends very well with the Maggies and is simple to set up thanks to the auto calibration. I just plug the video into my laptop to set up since I don't have a monitor in the room. Good luck!

Magnepan does have their own magneplanar woofer coming out soon...

http://www.audiojunkies.com/blog/247

I have the 1.2 maggies.I run it with a B&W sub.Set the sub crossover a 40hz.Mine seems to blend fairly smoothly.I bought the sub for musicality not boom.Tried quite a few before I came on this one.Ussually if it's good with music it's not good with HT.Since I'm more into music I went with that one.

I have the 1.2 maggies.I run it with a B&W sub.Set the sub crossover a 40hz.Mine seems to blend fairly smoothly.I bought the sub for musicality not boom.Tried quite a few before I came on this one.Ussually if it's good with music it's not good with HT.Since I'm more into music I went with that one.

Actually, if the sub is good with all types of music, its good with HT. If its good with HT, it is not necessarily good with music.

Nice system, mnilan.
You might check out the Velodyne DD series. They have ultra-low distortion, servo control for fast response and built-in software-based parametric EQ. I have 3.6's with a DD-18 and they mate very, very well. If you don't need <20 HZ response, the DD12 or DD15 might do the trick for you. They aren't cheap but they are top rated subs.

I agree that REL's are also supposed to work well with Maggies. I have listened to a REL mated with 1.6's but have not owned a REL.

I'd pass on the DefTech Supercubes. Too boomy and too much distortion at higher output, and real response does not equal what the claimed specs say. This is from personal experience with a SC I. The Velodyne is a MUCH better choice IMO.

Since my system does double duty for music & HT, I use the sub for multichannel music and HT, but just the Maggies for 99% of my 2 channel listening. I don't have the flexibility for multiple X-overs. If I did, then I'd X-ver the sub at 40-50 Hz for the 3.6's and 80 for the Maggie surrounds and 100 for the Maggie center.

Good luck,
ss9001

Magnepan does have their own magneplanar woofer coming out soon...

http://www.audiojunkies.com/blog/247

Luke:
Thanks but that Magnepan is not really a subwoofer. It is intended for their satellite-like speakers which don't really have much bass. So it is really more of a "woofer" for speakers that have almost no bottom end. I think my MG 1.6s would provide better bass all by themselves.

ss9001:
Thanks for the input. hifiskipper also advocated for the Velodyne subwoofers. I will give a listen to them (they are easier to find for a tryout than some others). I have always assumed that the Velodynes were HT subwoofers (albeit very good ones) so I didn't consider them for my music-only system.

Outlaw had an "ICBM" bass management system which, unfortunately, they no longer make which would work for your "multiple x-overs" problem. You may be able to find one used as people buy new receivers with integrated bass management...

Definately look into the REL's. I have heard nothing but great reviews.

ss9001:
Thanks for the input. hifiskipper also advocated for the Velodyne subwoofers. I will give a listen to them (they are easier to find for a tryout than some others). I have always assumed that the Velodynes were HT subwoofers (albeit very good ones) so I didn't consider them for my music-only system.


Guys were using Velodynes in audio systems long before HT.

Martin Logan seems to disappear with the 1.6's. Currently have a Velodyne HGS-18 THX that is 'quick' enough imo.

guy80:
Which model? I saw some new Grotto subwoofers on Audiogon for just above $700 but I haven't listened to them and don't have a dealer in the area...

I am also exploring Rythmik Audio's sealed 12" kit which is VERY reasonable in price. I'm not in a panic but living in the sticks has its disadvantages in this hobby 8^)

Folks:
After an extended conversation (via email) with Brian at Rythmik Audio, I've decided to try out Rythmik's 12" direct servo sealed subwoofer kit with a 24 dB low pass rolloff. I need to find a local cabinet maker who will build a down-firing enclosure for the kit.

why 24 dB roll-off?

Folks:
After an extended conversation (via email) with Brian at Rythmik Audio, I've decided to try out Rythmik's 12" direct servo sealed subwoofer kit with a 24 dB low pass rolloff. I need to find a local cabinet maker who will build a down-firing enclosure for the kit.

Did you determine that your speakers drop off with that 24db roll off to necessitate a 24 db low pass slope? Reason I ask is *perhaps* your Magnepans start to have "trouble" with bass below 160 hz, but dont have serious "issues" until 80hz. If this was the case, I would be considering gentler slopes so that the subwoofer can help fill in just a little bit in the 100hz range (maybe a 12db slope?) while still maintaining the cutoff point that you set (maybe 80hz?). I dont know how steep your magnepan drops off though...?

Did you determine that your speakers drop off with that 24db roll off to necessitate a 24 db low pass slope? Reason I ask is *perhaps* your Magnepans start to have "trouble" with bass below 160 hz, but dont have serious "issues" until 80hz. If this was the case, I would be considering gentler slopes so that the subwoofer can help fill in just a little bit in the 100hz range (maybe a 12db slope?) while still maintaining the cutoff point that you set (maybe 80hz?). I dont know how steep your magnepan drops off though...?

The recommendation of the 12db vs 24db is based on 1) if one already has a processor (bass management), and 2) which frequency to xover? If one does not have bass management processor, by all means, uses 24db. It will give you the most reliable phase alignment within the xover overlapping band. Slower 12db roll-off, not only gives us slower roll-off (meaning larger xover overlapping band) its phase can transition to 180 degrees which means out of phase between front speakers and subwoofer. 24db/oct actually give us 360 degrees and that becomes in-phase.

If one has bass management, but would like to set the speaker as large, he would also need 24db/oct. It will make the phase adjustment easier.

Brian

Rythmik Audio

The recommendation of the 12db vs 24db is based on 1) if one already has a processor (bass management), and 2) which frequency to xover? If one does not have bass management processor, by all means, uses 24db. It will give you the most reliable phase alignment within the xover overlapping band. Slower 12db roll-off, not only gives us slower roll-off (meaning larger xover overlapping band) its phase can transition to 180 degrees which means out of phase between front speakers and subwoofer. 24db/oct actually give us 360 degrees and that becomes in-phase.

If one has bass management, but would like to set the speaker as large, he would also need 24db/oct. It will make the phase adjustment easier.

Brian

Rythmik Audio

Thanks, i didnt know the phase angle was off by set amounts do to crossover order. Learn something new everyday!:)

Brian:
Your view reinforces insight I garnered from the planar phreques over on the Asylum. Even though my preamp (Outlaw RR 2150) has bass management, I will be bypassing it. (The Maggies go down to 40 Hz and the lowest setting on the Outlaw's bass management is 60 Hz). Others who have tried to blend in a subwoofer with Magnepans have felt that the Magnepan bass is quite good as far as it goes and the main problem is blending the subwoofer in with the Magnepan. The blending is easier with a steeper roll-off at a level at or below the lower limit of the Magnepans.

Although the metaphor may be weak, in my mind, I see what I'm doing as backing up the subwoofer high end to the Maggies low end - I don't want to run into them but I do want to get very close. Thus the steeper roll-off.

So, although I may be completely crazy, I don't think Brian is.

Thanks Brian.

Anyone in Iowa with Maggies want to experiment with dipole subs? Please PM me.

On my setup, I use the crossover on my Velodyne sub instead of the crossover built into my preamp as I feel it is probably much better in quality. On my preamp, I just have the crossover bypassed and it works great. Just make sure and don't use both crossovers at the same time. I'm not sure why exactly this reduces so much output, but maybe someone hear can explain it better than me.

On my setup, I use the crossover on my Velodyne sub instead of the crossover built into my preamp as I feel it is probably much better in quality. On my preamp, I just have the crossover bypassed and it works great. Just make sure and don't use both crossovers at the same time. I'm not sure why exactly this reduces so much output, but maybe someone hear can explain it better than me.

The rule of xover is that you want to get the ball park of the following two at the same time: 1) amplitude response is about equal at the xover frequency, and 2) the relative phase of the two is about the same (that means 360 degrees difference). When one sets the front speakers to large, it relies on the natural roll-off which is 2nd order for sealed, and 4th order for vented for attenuation. That is 90 degrees phase "lead" for sealed fronts, and 180 degrees phase "lead" for vented front. If someone uses a 24db/oct roll-off for the subwoofers, it gives 180 degree phase "lag" at the xover frequency. If someone likes bass heavy tuning (like me), the actual corner frequency can be a bit lower than the actual xover frequency. For instance, I like bass to be 5db higher (a nice bottom shelf-up curve). So even though my xover point is still 80hz, the actual roll-off (corner frequency) for the sub is at something like 60hz and when it reaches 80hz, it has an amplitude response to match the front speakers. The consequence is the phase shift at 80hz will be larger than 180 degrees (or like 270degrees). Even if something does not do the shelf-up curve, there is only 90 degree phase lagwe need to add to the sub (this is the time to use phase adjustment control). On the other hand, for the vented box fronts, the room for phase adjustment is not that good. It will become a little bit more difficult if ones use use a bottom shelf-up bass. The solution is to bring the subwoofer closer than the front.

Brian
Rythmik Audio

The rule of xover is that you want to get the ball park of the following two at the same time: 1) amplitude response is about equal at the xover frequency, and 2) the relative phase of the two is about the same (that means 360 degrees difference). When one sets the front speakers to large, it relies on the natural roll-off which is 2nd order for sealed, and 4th order for vented for attenuation. That is 90 degrees phase "lead" for sealed fronts, and 180 degrees phase "lead" for vented front. If someone uses a 24db/oct roll-off for the subwoofers, it gives 180 degree phase "lag" at the xover frequency. If someone likes bass heavy tuning (like me), the actual corner frequency can be a bit lower than the actual xover frequency. For instance, I like bass to be 5db higher (a nice bottom shelf-up curve). So even though my xover point is still 80hz, the actual roll-off (corner frequency) for the sub is at something like 60hz and when it reaches 80hz, it has an amplitude response to match the front speakers. The consequence is the phase shift at 80hz will be larger than 180 degrees (or like 270degrees). Even if something does not do the shelf-up curve, there is only 90 degree phase lagwe need to add to the sub (this is the time to use phase adjustment control). On the other hand, for the vented box fronts, the room for phase adjustment is not that good. It will become a little bit more difficult if ones use use a bottom shelf-up bass. The solution is to bring the subwoofer closer than the front.

Brian
Rythmik Audio

Let me see if I understand you correctly :)

If I have ported mains using natural roll off (lets say 40hz which also coincides with the main's port tune) and my subwoofer is between my mains and the same distance from the listening position as the mains, if I use a 24db/octave slope on the subwoofer at 40hz, most likely my ported mains will lead my subwoofer by 180 degrees? (and I would then have to set the subwoofer's crossover to 180 degree phase angle?)

Also, if something is 360 deg phase angle off, is this different from 0 degrees off in terms of time domain (signal hits ear at different times or same time?)

Let me see if I understand you correctly :)

If I have ported mains using natural roll off (lets say 40hz which also coincides with the main's port tune) and my subwoofer is between my mains and the same distance from the listening position as the mains, if I use a 24db/octave slope on the subwoofer at 40hz, most likely my ported mains will lead my subwoofer by 180 degrees? (and I would then have to set the subwoofer's crossover to 180 degree phase angle?)


Very close, but not exactly. The front with ported will have 180 degrees lead (4 times 45) at the corner frequency relative to reference 0. The sub with 24db/oct will have 180 degrees phase lag relative to reference 0. So between the front and the sub, it is now 360 degrees, which is same as 0 degree. One can easily implement Linkwitz-Riley filters (they published a technical paper for it) using 4th order filters. The advantage of L-R filter is the phase between the front and subwoofer is always 360 degrees. That is why I say it is a very robust design. The fact that it is a 360 degree difference means the filter can tolerate error/deviation in both directions with equal margin. In other words, we need to be 180 deg off to create a null at xover. L-R was one of the milestones in xover filter design. But the concept is very simple.


Also, if something is 360 deg phase angle off, is this different from 0 degrees off in terms of time domain (signal hits ear at different times or same time?)

A 360 deg relative phase difference is same as 0 degrees. However, L-R is not a so-called "linear phase" xover filter. That means the time domain waveform will have ringing. However, the problem with true linear phase xover filter is they 1) they need to be very precisely controlled, mainly because the phase difference between main and front is not equivalent to 0 deg, which means it is more suceptible to phase error in one direction than the other, which means the lobes of the dispersion pattern is not symmetrical, and 2) they are very complicated in implemention (which is the main reason they didn't gain popularity), except the first order RC filters.

Brian

Rythmik Audio

Thanks Brian! Ill go search for that L-R Tech paper!

The rule of xover is that you want to get the ball park of the following two at the same time: 1) amplitude response is about equal at the xover frequency, and 2) the relative phase of the two is about the same (that means 360 degrees difference). When one sets the front speakers to large, it relies on the natural roll-off which is 2nd order for sealed, and 4th order for vented for attenuation. That is 90 degrees phase "lead" for sealed fronts, and 180 degrees phase "lead" for vented front.

Brian
Rythmik Audio


What does the passive crossover in the speaker do with regards to phase?

If your mains are set to large, and they are sealed speakers, and the lowest frequency driver is passively 2nd order crossed at 100Hz (LP), the natural rolloff is still 2nd order.

Does the passive 100 Hz crossover produce another phase shift in addition to the 90 degree phase shift produced by the natural rolloff, or is there still only a 90 degree phase shift relative to the input?

A 360 deg relative phase difference is same as 0 degrees.

Brian

Rythmik Audio



Only for a steady state tone. There is still a time shift there!

What does the passive crossover in the speaker do with regards to phase?

If your mains are set to large, and they are sealed speakers, and the lowest frequency driver is passively 2nd order crossed at 100Hz (LP), the natural rolloff is still 2nd order.

Does the passive 100 Hz crossover produce another phase shift in addition to the 90 degree phase shift produced by the natural rolloff, or is there still only a 90 degree phase shift relative to the input?

Thats interesting... Do you mean "what happens when you have a bass driver in sealled that natural rolls at (say 80hz) but a 12db/oct hi-pass filter is placed at 100hz to roll off the bass faster, what happens to the phase?" (Or did i misread your post)

If I didnt misread, would that imply that between 80hz and 100hz, would be 90 degree out of phase, then below 80hz would be 180 degree out of phase (can you even add them like that?)

Thats interesting... Do you mean "what happens when you have a bass driver in sealled that natural rolls at (say 80hz) but a 12db/oct hi-pass filter is placed at 100hz to roll off the bass faster, what happens to the phase?" (Or did i misread your post)

If I didnt misread, would that imply that between 80hz and 100hz, would be 90 degree out of phase, then below 80hz would be 180 degree out of phase (can you even add them like that?)



Actually, my sealed speakers roll off at around 40 Hz. They are LP filtered with a passive 2nd order crossover to the next driver in the speaker. The natural roll off below 40 Hz creates a 90 degree phase shift relative to the input, but I am not sure how the speakers internal passive crossover affects phase.

Is there an additional phase shift caused by the speakers passive crossover? If so, by how much and in which direction (lead or lag)? Theoretical calculations are a big pain.

Only for a steady state tone. There is still a time shift there!

Time shift is ok. There is a group of filters called "linear phase" filters which works only for LP. It delays signals in the pass band by the same amount of delay time so that there is minimal ringing (some may call them constant delay filters). You cannot tell a time shift in a phase linear filters because it is so perfectly aligned that it looked as if the input signal is delayed.

Brian

Rythmik Audio

Actually, my sealed speakers roll off at around 40 Hz. They are LP filtered with a passive 2nd order crossover to the next driver in the speaker. The natural roll off below 40 Hz creates a 90 degree phase shift relative to the input, but I am not sure how the speakers internal passive crossover affects phase.

Is there an additional phase shift caused by the speakers passive crossover? If so, by how much and in which direction (lead or lag)? Theoretical calculations are a big pain.

Phase is always additive. LP is is always phase lag (that is why we can have linear phase or constant delay) filter. HP is always phase lead, that is why there is no so called linear phase (or constant delay) filter for HP.

If you have a LP filter, it is going to have phase "lag" at the corner frequency. This filter at 40hz may create a 20 degrees phase "lag", depends on the Q value of the filters. The phase change does not start until 3 octaves below the corner frequency and it also changes very little above 3 octaves. When we draw the "bode" plot, we normally draw a straight line between the frequency 1/10x and 10x of the corner frequency.

Passive filter works the same way as active, except passive filter is largely affected by the wavy impedance curve of the drivers. Therefore it is harder to predict.

Brian
Rythmik Audio

Time shift is ok. There is a group of filters called "linear phase" filters which works only for LP. It delays signals in the pass band by the same amount of delay time so that there is minimal ringing (some may call them constant delay filters). You cannot tell a time shift in a phase linear filters because it is so perfectly aligned that it looked as if the input signal is delayed.

Brian

Rythmik Audio



Then a purely linear phase shift is equivalent to a time delay?

I run my main R & L main sealed speakers (f-3 40 Hz) as large, and I fill in the low end roll off with the ported subwoofer (20 Hz HP plus 3rd order 50 Hz LP in SW amplifier). I use the speaker distance settings to send a signal to the subwoofer prior to main speakers (AKA delay mains), so I assume that would equate to a linear all band phase shift for the main speakers.

I can't figure out how much of that delay compensates for group delay, and how much for phase shifts. I guess that why it is easiest to just use a measurement device like True RTA so you can see what is going on via FR measurements.

Then a purely linear phase shift is equivalent to a time delay?

Only when it is phase lag.


I run my main R & L main sealed speakers (f-3 40 Hz) as large, and I fill in the low end roll off with the ported subwoofer (20 Hz HP plus 3rd order 50 Hz LP in SW amplifier). I use the speaker distance settings to send a signal to the subwoofer prior to main speakers (AKA delay mains), so I assume that would equate to a linear all band phase shift for the main speakers.

That is correct. However, after you put in the sub, the overall response will not be phase linear.


I can't figure out how much of that delay compensates for group delay, and how much for phase shifts. I guess that why it is easiest to just use a measurement device like True RTA so you can see what is going on via FR measurements.

I always use near field measurement to confirm the phase shift. I have a custom-made data acquisition system (2 channels). You can probably get the same result with some PC measurement system that does the MLSS measurement, not signal sweep. RTA does not give any information on phase relation.

Brian

I always use near field measurement to confirm the phase shift. I have a custom-made data acquisition system (2 channels). You can probably get the same result with some PC measurement system that does the MLSS measurement, not signal sweep. RTA does not give any information on phase relation.

Brian


You can infer phase relationships with multiple sweeps via True RTA. A single sweep will tell you little as far as phase relationships are concerned.

For example, my reference RTA sweep would be my main speaker's FR at the listening position. Then I add in the subwoofer, and do a second sweep. When you see abberations in the FR curves, you know there is a problem in time / phase.

Perform multiple sweeps, use multiple settings in time, frequency and polarity, and store each setting's FR sweep in memory. Repeat for multiple seating locations.

It is pretty obvious when you do a comparative RTA analysis what settings are wrong. For example, when I use the "as measured distance" settings in my receiver I get a major out of relative phase condition in the 30 Hz area between my mains and my subwoofer. The other frequencies also show different amounts of phase interaction.

At this point in time I look for a clean FR sweep in the 100 to 200 Hz area, along with no "out of phase" problems in the 30 Hz area.


You can also measure relative driver phase relationships with the dual trace oscilloscope portion of the True RTA program if you use two microphones. That is not an RTA, but it is part of the True RTA program.

You can infer phase relationships with multiple sweeps via True RTA.

Still it is not a clean solution. How accurate you can "infer" across the frequency? How many trial-and-error one has to go through before he gets satisfactory results? And MLSS measurements gets all information in two shots (one for main and one for sub), and the rest is just "paper" (actually computer is the correct term) simulation and the last validation measurement . The high resolution of phase response in MLSS also gives you the capability of "what-if" analysis. One should never skimp on analysis equipements. I remember one quote from an audio forum saying the debate in audio is the most heated because the stake is so low. I believe that is true in any audio forum. What if we are both wrong here? No one gets hurt. Imagine we go to a hospital to do a CT scan and the person comes back and say, well, our CT scan is out of order now, but we can do x-ray, would anyone take that? That is an example of high stake debate.

Brian

Rythmik Audio

Still it is not a clean solution. How accurate you can "infer" across the frequency? How many trial-and-error one has to go through before he gets satisfactory results?




How accurate can you infer what across the frequency?

Most consumers measure nothing at all except SPL, and just guess at the correct phase match between the mains and the subwoofer as the one being the loudest of the 0 and 180 degree "phase" adjustment (AKA polarity adjustment). Phase is most likely neither in nor out in with that method of "phase matching".

As far as trial and error is concerned, it's not pure guesswork with no record of what was measured for in room FR. I can adjust individual channel crossovers from 40 Hz to 200 HZ in 10 Hz increments, plus the LFE high cut filter. The different adjustments sound different and measure different, so there is some trial and error involved (AKA analysis).

Same goes for large and small speaker size settings. Different BM, different routing of redirected bass, different setting for the subwoofer LP filter. Trial and error is involved (AKA analysis). New FR measurements is also involved with each new setting (if you care to know what the changes do in room).


Documented "trial and error" results can also be called experience. For example, I know how much to change the distance setting for the subwoofer when I change the LP filter setting on the subwoofer from 120 Hz to 50 Hz. If you make any LP filter change in the subwoofer circuit, the phase relationship with the mains changes. I know that if I make change A in the system, then I must also make change B (and C) at the same time in order to maintain correct phase relationships.





And MLSS measurements gets all information in two shots (one for main and one for sub), and the rest is just "paper" (actually computer is the correct term) simulation and the last validation measurement . The high resolution of phase response in MLSS also gives you the capability of "what-if" analysis.

Brian

Rythmik Audio


After you take your two MLSS measurements, how do you determine the correct distance setting that you will use for the subwoofer per your MLSS results? Does MLSS gives you that number? Via theoretical analysis of your results? Via real world as measured once in room analysis?

Do you take MLSS measurements of both working together as a unit measured at the listening position(s)? If something does not look right on MLSS, then what do you do?

Anyone (in theory) can take measurements. Knowing what to do with them is another matter.

Wow, interesting conversation.

Back to the thread topic. I used Mags for about 12 years. Before I had the 3.6's, I used a velodyne 12". I can't remember the model number as it was over 6 years ago. The theory at the time was that Velodyne was one of the few sub manufacturers out there quick enough to keep up with the mags. It worked great.

I'll keep it simple AND what you should do...

Magnepan older tympani 4, 4a, any current 3.6, 1.8 or any current product will benefit from:

Velodyne 10, 12, 15 inch drivers
Sunfire 8, 10, 12 inch drivers
Bag End infra 18 inch driver
Many other subs out there.....
A decent sub with built in amp and crossover retails around $1000.00.
You could go to guitar center and try any of the JBL with 18" self powered.

Raising the woofer off the floor 6", 12" may be upto 18" off the floor on any type of stand for experimentation.

In two channel or multi-channel:
1. place woofer facing either side wall in-between the main speakers and about one to two feet behind the speakers.

2. place woofer behind you on the rear wall about mid wall and change phase on woofer and play woofer at lower level.

3. Place woofer on left or right wall about 1/3, 1/2, 2/3 from front wall away from where main speakers are in front of speaker at 45 degrees either pointing to speaker or pointing into room in your direction and play with phase and gain on woofer.

4. Setting up your main speakers for best imaging, clarity and over all excitement to your listening chair, couch... then move woofer around room to find best blend or making the woofer seem invisible to mate with main speakers will only require about 30ft of cheap wire attached to woofer and move it around the room.

Good luck, try it, there is no magic to this only your perception to where the woofer will work in your room, wife acceptance factor and ultimately you will be the judge. You should have positive results over one weekend then an additional weekend or two to go back and try position A vs. position B.

I have the 1.6 and ACI TItan II and it integrates very well with my surround setup for HT and music. You may want to read more about maggies and subs at the audioasylum.com - planar speakers forum. Lots of great knowledge there.

I do not own Maggies, or stats for that matter, but I do own a pair of 2Wqs for my Vandy 1Cs. I love them - they are sonically invisible until the source has low bass in it and then - POW! - you feel the bass run through you. Tight, clean, deep and quick. They do not lag the mains speakers, even though they are placed outside and behind the 1Cs in opposite corners. They are the opposite of my DefTech PF15, which now does LFE duty in my combo 2-channel/HT rig. The Def Tech needs the Behringer EQ to smooth out room nodes. It is sluggish and seems to play behind the music - and I have the DefTech on the same plane as the 1Cs. The 2Wqs, OTOH, sound perfect without any help from any other electronics. My room is far from ideal, and I am still using the X-2 crossover (intended by Vandersteen as a temporary device that must be replaced by a fixed-value crossover once the associated gear is known).

If you look around - especially on planar speaker boards at places like Audio Asylum - you will see that many opinions that few subs have the speed to keep up with Maggies besides the Vandys. The REL may be another one, as well as the Martin-Logan subs, and some have provided other brands here, too. IMHO, the Vandy 2Wqs offer value that is way off the charts for subs designed to be used for music. reproduction. They offer a unique crossover design that, Vandy claims, preserves the phase and other characteristics of the signal your main speakers get from the amplifier, which makes subs and speakers sing as one.

Sorry, I have been doing a bit of travelling (Vancouver, B.C., Seattle & Portland) and listening to subs... Thanks for the continued attention to my query. I am still leaning towards a Rythmik 2' but I did get a REL 201 to audition from a local audio fan. Sounded pretty good but I think it was a bit underpowered for the room...

I used a Velodyne F1800 sub with my Magnepan 1.5s in a stereo only setup and it sounded great. I found I was able to get better sound by using a 65hz inline filter between the Magnepans and the amp.

I had a Acurus RL-11 preamp and then a Adcom 700 something (balanced) both had dual line outs so I would run one set to the amp and the other to the sub.

I would recommend any of the servo Velodyne subs and personally I would look for a HGS-15 on audiogon unless you want to go for the DD series.

I used a Velodyne F1800 sub with my Magnepan 1.5s in a stereo only setup and it sounded great. I found I was able to get better sound by using a 65hz inline filter between the Magnepans and the amp.

I had a Acurus RL-11 preamp and then a Adcom 700 something (balanced) both had dual line outs so I would run one set to the amp and the other to the sub.

I would recommend any of the servo Velodyne subs and personally I would look for a HGS-15 on audiogon unless you want to go for the DD series.

I'm also using a Velodyne F1800 sub (with Maggie 3.6Rs), with the Maggies fed the full audio spectrum (per advice from the Maggie technical staff). Most would say that the Velodynes are "too slow" and could never "keep up" with the Maggies. This may be true if the Xover is set at 70 - 80Hz, but not if they are set at lower frequencies, such as 45 to 55 Hz. For most music, I find that the resonse can be greatly improved, even using a large sub such as the F1800, which is probably not ideal for the Maggies. Obviously, adjustments using test records and spl graphs are recommended to get the flatest response in your room and with your system.

Jim

Folks:
I think this 2-channel area is a great idea!

I have separate HT and music areas in my house. For my music system, I have:

Magnepan 1.6s
B & K Reference 4420 Dual Mono Amp (350 watts @ 4 ohms)
Outlaw RR2150 using preamp outs
Pioneer DV 45A disc player (DVD-Audio, SACD, CD)
Techics SL 1210 MK II Direct Drive Turntable with a Shure M97xE cartridge

My current dilemma is that the Magnepan speakers do not seem to do justice to the low end. They are rated down to 40 Hz (for whatever that's worth) but a stand-up bass (for example) doesn't come across with as much authority as it should. So, I'm thinking of a subwoofer to "reinforce" the low end of the Maggies. The Outlaw receiver has a subwoofer out and a bass management filter that will send everything below 60 Hz to the subwoofer. The room this is set up in is BIG - 17' X 30'.

What I need is a subwoofer that can do 60Hz to 20 Hz quickly enough to keep up with the Maggies. I have been looking at subwoofers (slowly, as I don't live in an area with high-end bricks & mortar stores) and from what I have heard so far, REL (not sure what models to even think about) and the Vandersteen 2WQ are contenders.

What I don't need is an HT subwoofer that booms. I've got a HSU VTF 3 MK II in my home theater and I tried it out in the music system but I was having real problems getting it to "reinforce" - it either seemed too loud or didn't seem to make any difference at all.

FWIW I have tried this in the subwoofer forum but got sheer nonsense from HT-centric folks. I also tried the Asylum but their advice was not helpful either. Hopefully here I will get someone who also has Magnepan 1.6 speakers or else someone who can refine my search (e.g., which model REL to focus on listening to...).
REL Strata III (or other S series depending on room size). I use with 1.6's. Excellent for music (high end connection to the amps), and for HT (low end connection from pre/pro).

I think I would have just bought a Totem Storm.

http://www.totemacoustic.eu/english/subwoofer/storm/storm_06.html

You would probably like one or a pair of offerings from Rel. Perhaps a pair of Brittania's?