[Nyal Mellor]

It makes a difference.

Let's take a single speaker in the room. We want a good polar response, good horizontal dispersion, and even response across the board. Why, because we hear the interaction with the room and we want side wall and ceiling reflections to be in direct relation to the on axis response and not a peaked or dipped reflection.

All of the sound from 20Hz (full range speaker) and up comes from one point in the room (same example). So the reflections in the room do cause a peak or a dip somewhere and at the listening position we can treat it with room treatment etc, to minimize it all.

All this is a given, you knew it all already...

Now we split from 100Hz or so away and position it from somewhere else in the room. Now we have the same thing to contend with before but from two sources. So on top of a peak or a dip that we get from the room response, we also get a secondary peak and/or dip from an out of phase cancellation from some of those reflection points. And remember 100hz and up starts getting directional so you hear it.

Just because the amplitude measures fairly flat at the listening position doesn't mean it will sound right.

Years ago there was a system showed with Tech audio gear (something like that), maybe it was Tec Audio. Anyway they separated the 200Hz range and below and sent to to subs that were corner loaded. And they relieved the mains from 200Hz on down.

They took in room measurements and made digital room correction and all of that so it was flat as can be from the listening position. The corner loaded subs may have evenly loaded the room, but the music was very disjointed. You could clearly hear the bottom end firing out at you from the corners of the room.

I still don't see why that is important, when you can use time delay to align the drivers AT THE LISTENING POSITION and avoid peaks or dips due to phase interference. Generally it is only the first peak or dip that we need to worry about, and that is the one you can fix through time delay. On top of that using multiple subs will smooth out the frequency response anyway, since there are many reflections contributing to that frequency response.

Could please elaborate on why a flat frequency response would not 'sound right'?

I understand your last point, but that is why you don't run subs physically separated from the satellites up to 200Hz, as we can localize the sound. 80Hz XO is normal in HT, I might try 100Hz but that would be about the top I think, based on what I have read e.g. from Toole.

[Nyal Mellor]

Why do you want it to be a 2-way? (Sorry if I missed it.)

To avoid complications. In a two way mid/tweet like the Orion it seems that you can fake true dipole radiation pattern through running a driver into the frequencies when it starts to become directional and running the driver over its dipole peak. If you want to avoid this then it seems that you need a three way; which for my situation when I also want subs, would mean a four way.

[Nyal Mellor]

My open baffle speakers are further out into the room and mine occurs lower in range.

I then add gain with the one band EQ and fill it back to flat again.

You can't effectively EQ a phase cancellation null. It is not just possible. You add more power to the direct wave, that is met in turn by the same increase in power from the reflected wave, result - cancellation is still the same.

[Danny Richie]

Could please elaborate on why a flat frequency response would not 'sound right'?

Sure, here is a simply example that I often see.

I guy has a 2kHz or 3kHz peak in the room from a side wall reflection. So he uses some type of room correction or EQ to reduce the output in that range. Now he has a flat in room frequency response relative to what it was. However, he didn't fix the problem. There is still a reflection, and it still does not sound right.

You can't effectively EQ a phase cancellation null. It is not just possible. You add more power to the direct wave, that is met in turn by the same increase in power from the reflected wave, result - cancellation is still the same.

If bass radiated in only one plane then that would be true, but it does not.

Bottom line is that if you are playing the subs that high (100Hz) then you need to keep them within 5 feet or less of your main speakers to avoid various problems.

[Nyal Mellor]

Danny, this thread has gone off topic.

We were talking about frequency response as it relates to low frequency reproduction, not specular reflections like the example you gave in response to my question. Of course I understand that decay time also matters at low frequencies, but again not in the context of what we were talking about which was physical separation of sub from satellites.

And I don't understand your point about bass radiation into multiple planes.

May I suggest we cut our losses and get back to the thread?

So let's try - what suggestions do people have of suitable midrange drivers that could be used in an open baffle project to cover the range 100Hz to around 1.5kHz.

[Danny Richie]

I'm sorry. I tried to make my examples as simple as possible so application could be made.

You might have a look at this example to see how bass output really works:

http://paws.kettering.edu/~drussell/Demos/rad2/mdq.html

While you can have a delay front to back that causes some cancellation in a given area, you do not get a full 15db dip (from full cancellation) because the radiation pattern also allowed output at that frequency to reach the ear (or mic) that reflected off of side walls (both front and back sides) and those have a different delay than the front or back wall reflection and are not out of phase.

So if I have a 3 or 4db dip in a given area (as per my open baffle speakers in my room) I can EQ that dip out easily with my amp.

What you are asking for in a single mid-range is not practical. You will have to add gain to the range below 200Hz then brick wall (steep slope) the output below 100Hz to keep it from getting beat up. You can do that with a lot of EQ but sensitivity and output capability will be fairly low. There are easier and less expensive alternatives that will give you better results.

[Nyal Mellor]

I'm sorry. I tried to make my examples as simple as possible so application could be made.

You might have a look at this example to see how bass output really works:

http://paws.kettering.edu/~drussell/Demos/rad2/mdq.html

While you can have a delay front to back that causes some cancellation in a given area, you do not get a full 15db dip (from full cancellation) because the radiation pattern also allowed output at that frequency to reach the ear (or mic) that reflected off of side walls (both front and back sides) and those have a different delay than the front or back wall reflection and are not out of phase.

So if I have a 3 or 4db dip in a given area (as per my open baffle speakers in my room) I can EQ that dip out easily with my amp.

You have lucked out on the path length differences if you are only seeing a 3-4db dip. Often I am seeing 10-15dB. All depends on where you, the speakers and the room boundaries are. Yes, if you are not seeing full cancellation then EQ will be effective.

[Nyal Mellor]

What you are asking for in a single mid-range is not practical. You will have to add gain to the range below 200Hz then brick wall (steep slope) the output below 100Hz to keep it from getting beat up. You can do that with a lot of EQ but sensitivity and output capability will be fairly low. There are easier and less expensive alternatives that will give you better results.

But Linkwitz has done it in his Orions! What alternatives would you suggest? More like what we were talking about earlier with two smaller midranges in a MTM or 2.5 way type design?

[Danny Richie]

But Linkwitz has done it in his Orions!

Sure, and it's easy to do, and it's a great sounding speaker, but look at the limitations.

You have a mid playing down to its physical limits in that arrangement and at 85db sensitivity it has limited output capability, and very limited dynamics. Even the lower woofers are very limited. Those low Q woofers hit their physical limits real easy and I think the latest transform circuit used on them limits the first octave output and rolls them off so that they are -3db down at 40Hz with a second order slope, or something like that.

I have Orion owners adding our open baffle servo subs to them to get that solid bottom end extension.

http://www.audiocircle.com/index.php?topic=70370.0

What alternatives would you suggest? More like what we were talking about earlier with two smaller midranges in a MTM or 2.5 way type design?

There are a lot of things that you could do. The tough part for me is giving you suggestions without mentioning anything of my own, but I'll give it a shot.

1) You don't have to go to smaller drivers, but going to a pair of 16 ohm woofers in an MTM design will bring your output levels up when you want them to be, and still be an easy load to drive. With two woofers sharing the load evenly, each works less to give you the same SPL levels. That in itself minimizes distortions caused when pushing a driver hard. This will bring dynamics up some too.

2) You could consider a well design passive network for the upper drivers and save a lot on amplifier cost. Then instead of 4 channels needed and having to settle for cheap amps, you can put you money into a single higher quality one. That can be a big improvement.

3) There are better options in the bottom end as well. That's a whole new discussion.

Another real limitation to avoid if you are reaching for the top level of performance is the use of digital crossovers. The quality of the D/A conversion for most of those is just not there yet. If you even went with one of the least expensive DAC of the top performers, like a Tranquility DAC, you'd need three of them for six channels. That would cost you about $4,500 just for the DAC's. Of coarse if money is not a factor then by all means have something built.

[D OB G]

Hi Nyal,

I'd be interested to know what DSP solution you are using.

Some three way systems can be configured to do sub and woofer from the same channel, thereby allowing a four-way.

I'm still not quite sure if you are looking to "rebuild" the Orions i.e. find a better solution to a single 8" only, or if you're looking at a clean slate.

BTW  I agree with you're position on the ability to get a flat low freq response at the listening position with distributed subs, near the main speakers and EQd (but only in the MODAL region, as all DSP manuals emphasise, as I'm sure you're well aware).

Regards,

David

[Nyal Mellor]

I'd be interested to know what DSP solution you are using.

I'm still not quite sure if you are looking to "rebuild" the Orions i.e. find a better solution to a single 8" only, or if you're looking at a clean slate.

Hi David, it will be a DEQX. The design can be a complete clean slate, although one of the cool things about already having the Orion is that I can test some of my crazy theories to see if they are true with respect to improving sound quality. Like I said at the beginning, I'm definitely getting some grain in the upper midrange /lower treble, particularly with femal vocals, where it is quite annoying on some CDs such as Sophie Millman. Also I feel that although the bass is good, it is not comparable in terms of effortlessness and dynamics that I get with a home theater setup with separate subs or even a good monopole box speaker like an Avalon or Wilson. Although Linkwitz denies it, I believe that the baffle movement due to the woofers being in the same cabinet as the mid and tweeter causes some of the lack of imaging solidity that I observe.  So those are the things I am trying to improve, I love everything else about it.

[D OB G]

Nyal, I've always wondered about the overall outcome of the advantage of magnet mounting the mid, versus the negative of having that magnet on a vibrating woofer enclosure.  SL obviously believes that it is better than mounting to the baffle, but maybe another way could be found to mechanically "short the mid to earth" (separate legs behind?).  I always use separate baffles for mid and woofer for this reason.

Is the graininess the sound of a tweeter used too low do you think?  Could playing around with the crossover clarify the matter?

I too use a DEQX.  It is possible to run the bass output to your amp and then into a subwoofer amplifier (I use Rythmiks), use a 24 dB per octave slope between subwoofer and woofer, take the high level input to the subwoofer, and the high level output to the OB woofer.  The combination can then be calibrated in one go.

This gives two channels, for mid from, say, 200 or 300 Hz, and the tweeter.  i.e. the mid doesn't need to 8" (but with a smaller driver the baffle would need to be narrower).

So if you you use say four Thors crossed at 50 Hz, as SL now crosses, you could maybe take the H baffled woofers higher (DEQX will take care of any standing waves).  This would obviously destress the mid, or you could use a new mid that isn't chosen specifically to go to 100 Hz.

The mid chosen could go higher to destress the tweeter.

Just a few thoughts.

Regards,

David

[ronpod]

Nyal,

I am interested in your opinion of the Version 3.1 modifications to the Orion+. Could you post your impressions when you have implemented them and have a chance to listen?

I had a chance to go to a local microbrewery and listen to an acoustic jazz quartett with a standup bass. I compared that to well recorded jazz acoustic bass played through the Orions and thought that they compared well. It seems to depend allot on the quality of the recording.

I do like artificial boosted bass in my HT application for punctuation. But while listening to live acoustic performances, my opinion is that the bass isn't as prominent as reproduced on many of my friends audio systems. The beautiful aspect of this hobby is that your preferrences can be dialed in. My opinion is that the aliveness of the sound usually comes from the mid to high frequency reproduction. Hence my interest in what you think of the recent Orion mods.

[Nyal Mellor]

David

Those are some interesting thoughts indeed. I had not considered keeping OB woofers, I had in my mind crossing over from monopole subs to a dipole mid around 80-100Hz which would then run all the way up to the XO with the tweeter.

Maybe a much better way to do it would be as you say - that is to use monopole subs up to say 80Hz, then OB woofer to 200Hz, and then a OB midrange to the XO with the tweeter. That would make things a lot easier in terms of selecting a midrange driver, since one could get away with a much smaller driver given that the OB woofers are now taking on high bass duties. And XO'ing to the monopole subs at 70-80Hz is going to take away a lot of the excursion requirements of the OB woofers, maybe even one 12" is enough. I will have to do some modeling, but this is a more promosing way of doing it that I was thinking.

I wonder if Linkwitz had originally designed the Orion as a 4 way he would have come up with a different design. From reading his website it appears he intended it as a 3 way, then later added the Thor subs. Maybe if he had started off with monopole subs in the design equation, so to speak, then the XO points and drivers would have been different.

[lowtech]

Maybe a much better way to do it would be as you say - that is to use monopole subs up to say 80Hz...

It's called a Thor and it's designed to work with your speakers.  You can read about it here.

Most room modes occur below 80Hz, so running dipole in that region is generally beneficial.  If in doubt, measure your room response.

[Nyal Mellor]

It's called a Thor and it's designed to work with your speakers.  You can read about it here.

Most room modes occur below 80Hz, so running dipole in that region is generally beneficial.  If in doubt, measure your room response.

My understanding is dipole is theoretically meant to excite less room modes due to the radiation pattern, which is figure of 8 as opposed to omnidirectional for a monopole speaker. However any room I've put the Orions in I have still needed EQ to tame room mode resonances. I'm not going to go with the Thor design for my subs, I would like something that is flexible enough to be combined with other systems should I abandon the Orions entirely.

[lowtech]

My understanding is dipole is theoretically meant to excite less room modes due to the radiation pattern, which is figure of 8 as opposed to omnidirectional for a monopole speaker.

True.  Both in theory and practice.

However any room I've put the Orions in I have still needed EQ to tame room mode resonances.

Most rooms are not perfect and even a dipole radiator will excite room modes.  If you aren't convinced that your Orions in your room aren't providing smooth, uncolored bass response, try a simple experiment and measure a pair of sealed subs in the same location as your dipoles.  If my experience (and that of a lot of others') is any indication, your Orions will measure significantly better (smoother) through the regions where your room is being excited.

I'm not going to go with the Thor design for my subs, I would like something that is flexible enough to be combined with other systems should I abandon the Orions entirely.

Good luck with that.

[JohnR]

To avoid complications. In a two way mid/tweet like the Orion it seems that you can fake true dipole radiation pattern through running a driver into the frequencies when it starts to become directional and running the driver over its dipole peak. If you want to avoid this then it seems that you need a three way; which for my situation when I also want subs, would mean a four way.

I was under the impresssion that you already have a distributed subwoofer system that you like and want to use. You could use one channel of the DEQX to drive/equalize (freq and phase) both the dipole woofer/s and the distributed sub system to come in "underneath" it. Choose a larger driver for the dipole woofer with a higher Fs. Just a thought

[thomasjefferson]

This thread was going so well until the last page! 

Some good commentary, and I'll add a few thoughts as an OB builder. 

First, this question of a 2-way OB that covers from 100 Hz up.  It's true that Orion does this (above 120 Hz that is).  But it's problematic because it is hard to go that low with a midrange in an OB.  Using a larger woofer to better handle the depth, then it's hard to get high enough to reach a tweeter.  Crossing a tweeter as low as 1.4 kHz may be responsible for the "grain" that Nyal observed.  I'll make this wild guess, that the internal chamber for a dome tweeter can't adequately control resonances that low in frequency, and there is some impurity to the response as a result.  And crossing the 8" metal cone as high as 1.4 kHz is also a bit troubling because it's approaching the metal diaphragm resonance. 

The simplest solution here is to have the bass section extend higher, for example the way Danny has been doing with his servo woofers.  Moving the woofer low pass up to 200 Hz takes the pressure off the midwoofer.  There are plenty of ways to resolve a 2-way OB above 200 Hz.  The mid can be smaller than an 8", and better able to extend higher.  The tweeter can cross higher than 1.4 kHz, and everything behaves well. 

Note also, there are ways to build an OB bass cabinet that allow clean response higher than 200 Hz.  It's mostly a matter of decreasing the front-to-back depth, with either a flat baffle or a relatively shallow H-baffle.  The upper limit of the woofers just depends on how low the mids can go, so everything works together.

And, my suggestion is to use a closed box subwoofer only up to 50-60 Hz.  This avoids the issues with needing to locate the sub near the mains, and also allows the OB bass to cover most of the modal region.  Actually, this is a logical next step from the example of Orion--knowing that the woofers only need to reach down to 50 Hz means they can be designed to reach higher into the mid-bass region.  If Orion had been designed to work with the Thor subs, it could have had a different baffle design that would allow the woofers to go higher, which in turn would allow the mid to downsize, and the M/T crossover to move higher.  The 4-way system just works better from bottom to top.

[Nyal Mellor]

And, my suggestion is to use a closed box subwoofer only up to 50-60 Hz.  This avoids the issues with needing to locate the sub near the mains, and also allows the OB bass to cover most of the modal region.  Actually, this is a logical next step from the example of Orion--knowing that the woofers only need to reach down to 50 Hz means they can be designed to reach higher into the mid-bass region.  If Orion had been designed to work with the Thor subs, it could have had a different baffle design that would allow the woofers to go higher, which in turn would allow the mid to downsize, and the M/T crossover to move higher.  The 4-way system just works better from bottom to top.

Yeah I think a four way is the best bet, and with the topology that has been described.