National Audio Show Whittlebury Hall 2014

[Alan Sircom]

We did consider using a Trinnov Amethyst to help counter room gain, but there's a couple of fairly unique problems with demonstrations and DSP; listener position and the ever-changing number of bodies in the room, which have a fairly big influence on the sub-200Hz performance. If you have a room full of fleshy, walking bass traps, the bass performance is very different to a room where there is just one or two people in the room.

The other relatively insurmountable problem with DSP is if you create a sweet-spot in the 'listening zone' of the room, you invariably do so at the expense of the sound outside that sweet spot, which often includes people at the door and people not sitting down. There are a lot of 'architrave audiophiles' at a show, who hang around at the door frame of a room and never venture further in (it's why some companies go for ticketed demonstrations), and using DSP can undermine that door frame experience, pushing away casual listeners in the process.

On a more pragmatic level, if you are an electronics company that doesn't sell DSP room EQ, using it is like saying "our gear isn't good enough". That's less of a problem if you are a loudspeaker maker, but there's still the potential for accusations of 'cheating' by visitors.

Instead, we went with passive room treatment, creating a mostly LEDR (live end, dead end) environment with a lot of GIK Acoustics traps... but in hindsight still not enough traps. We also went with positioning the loudspeakers firing across the room and too close together for minimum room gain at the expense of imagery. Although we took out a lot of irregularities in the room, there was still a lot of room gain at around 50Hz, and the air-conditioning ducts set off at about 35Hz at anything above conversation level (about 60dB in room). In retrospect, I would have tested the theory that you can never have enough bass traps, by packing a whole Luton van full of the things.

The larger rooms were noticeably worse this year than last because of a slight change to Whittlebury's room management. Last year, rooms were allowed to store their boxes in the 'en suite' store rooms, while the non-allocated rooms were locked chair storage. This year, they changed to having the non-allocated rooms as box stores, and the 'en suite' was a locked chair store. Many remarked last year that the rooms sounded better if they left the door to the box-filled 'en suite' storage room open, as it acted as a form of Helmholtz resonator. This year, that option was closed to us, and the room gain problems in the larger rooms were far worse across the board, IMO.

None of this should be viewed as making excuses for rooms, more an explanation of how much goes into trying to make a silk purse out of a sow's ear, and we still don't get it right. However, what was worrying for me was that this year even fewer manufacturers and distributors were using room treatment in rooms that are notoriously poor in this respect. The larger ones are almost a lost cause unless you bring about a tonne and a half of traps and treatment, but the smaller ones are rock wall and concrete cubes, and can do with all the help you can bring. They are also small enough to treat relatively easily and cheaply; the dynamics of the room precludes great sound, but the potential improvement makes the difference between 'lousy' and 'fairly good'. Treatment also allows the system to show what it's capable of, instead of having to hide behind safe music. I do cop to playing an hour or so of safe music on Sunday morning, but I was badly hungover, and an Elvis and Nurophen cocktail was required.

[YNWaN]

Hi Alan, I hope you don't mind me answering your post in sections but you raise a number of equally valid, but different, points.

We did consider using a Trinnov Amethyst to help counter room gain, but there's a couple of fairly unique problems with demonstrations and DSP; listener position and the ever-changing number of bodies in the room, which have a fairly big influence on the sub-200Hz performance. If you have a room full of fleshy, walking bass traps, the bass performance is very different to a room where there is just one or two people in the room.

Yes, I accept all of that; but in this case the people numbers were pretty low compared to the room volume (air volume). I believe that you were upgraded at the last minute and there isn't much you could have done about that.

The other relatively insurmountable problem with DSP is if you create a sweet-spot in the 'listening zone' of the room, you invariably do so at the expense of the sound outside that sweet spot, which often includes people at the door and people not sitting down. There are a lot of 'architrave audiophiles' at a show, who hang around at the door frame of a room and never venture further in (it's why some companies go for ticketed demonstrations), and using DSP can undermine that door frame experience, pushing away casual listeners in the process.

Yes, but an element of that exists whatever you do - a sweet spot exists irrespective of the use of DSP.

On a more pragmatic level, if you are an electronics company that doesn't sell DSP room EQ, using it is like saying "our gear isn't good enough". That's less of a problem if you are a loudspeaker maker, but there's still the potential for accusations of 'cheating' by visitors.

I suppose. I hadn't considered the 'cheating' claim but I can certainly see that it isn't commercially easy to use components by manufacturers that aren't part of a companies portfolio.

Instead, we went with passive room treatment, creating a mostly LEDR (live end, dead end) environment with a lot of GIK Acoustics traps... but in hindsight still not enough traps. We also went with positioning the loudspeakers firing across the room and too close together for minimum room gain at the expense of imagery. Although we took out a lot of irregularities in the room, there was still a lot of room gain at around 50Hz, and the air-conditioning ducts set off at about 35Hz at anything above conversation level (about 60dB in room). In retrospect, I would have tested the theory that you can never have enough bass traps, by packing a whole Luton van full of the things.

As you say, there was a lot of 50Hz gain and passive room treatment has to be massive to do much at these frequencies. Personally, I have used DSP to address a 50Hz room mode and it was very effective. True it will be not be universally effective in every part of the room but then nor will any other solution.

The larger rooms were noticeably worse this year than last because of a slight change to Whittlebury's room management. Last year, rooms were allowed to store their boxes in the 'en suite' store rooms, while the non-allocated rooms were locked chair storage. This year, they changed to having the non-allocated rooms as box stores, and the 'en suite' was a locked chair store. Many remarked last year that the rooms sounded better if they left the door to the box-filled 'en suite' storage room open, as it acted as a form of Helmholtz resonator. This year, that option was closed to us, and the room gain problems in the larger rooms were far worse across the board, IMO.

As you say, most rooms suffered from this problem - some even more than you.

However, what was worrying for me was that this year even fewer manufacturers and distributors were using room treatment in rooms that are notoriously poor in this respect. The larger ones are almost a lost cause unless you bring about a tonne and a half of traps and treatment, but the smaller ones are rock wall and concrete cubes, and can do with all the help you can bring.

I quite agree.

[Alan Sircom]

Hi Alan, I hope you don't mind me answering your post in sections but you raise a number of equally valid, but different, points.

No problems at all. It's all in the proper spirit anyway!

Yes, I accept all of that; but in this case the people numbers were pretty low compared to the room volume (air volume). I believe that you were upgraded at the last minute and there isn't much you could have done about that.

Agreed, and yes. Typically, the room had on average about eight bodies in there, three of them from the magazine, and at least seven at any one time had a pulse. At its best, we had about 20, at its worst we outnumbered the public four to one, and there were only three of us in the room!

Yes, but an element of that exists whatever you do - a sweet spot exists irrespective of the use of DSP.

Yes, but the peculiar part is that the more work DSP has to do inside that sweet spot, generally the worse it sounds outside. If you get a lot of phase cancellation at the door, you end up losing a lot of people who might otherwise enter the room.

I suppose. I hadn't considered the 'cheating' claim but I can certainly see that it isn't commercially easy to use components by manufacturers that aren't part of a companies portfolio.

The 'cheating' accusation is an odd one, I have to say. It completely blind-sided me when I heard it with regard to passive room treatment. I was expecting the usual 'divorce maker' and 'wife unacceptance factor' quips, but not "it's cheating". Apparently, it's a fairly regular grumble at shows, and why we don't focus on room treatment anywhere near as much as I'd like in print or online.

As you say, there was a lot of 50Hz gain and passive room treatment has to be massive to do much at these frequencies. Personally, I have used DSP to address a 50Hz room mode and it was very effective. True it will be not be universally effective in every part of the room but then nor will any other solution.

Agreed, but the last part is the problem. In a domestic environment, you are reasonably confident of the scope of DSP, in terms of a zone of width, depth and height where the listener is likely to sit. You know that the listener is likely to be in a seated position during most of the listening session. That really doesn't happen in a show: the attendees who walk through the door typically spend 30 seconds or so standing up clutching one of the middle chairs along the back row. If they like what they hear at that point, they usually either sit in one of the centre chairs, or walk up to the system, have a nose around, then sit toward the middle of the front row. If you don't nail the sound behind that back row at standing head height, they typically shake their head and leave. So, in terms of a DSP sound field, you need to create a reliable, good sounding zone across a fairly large space, especially in terms of listener height. That is difficult, IMO, and if you get that kind of outer regions of the DSP EQ field phasiness, you end up doing more harm than good to the cause.

The other plan for this was originally to show the effect of passive and active room treatment, by physically moving room treatment into and out of the room, and turning DSP on and off with something like the Trinnov or a Lyngdorf. That all went a bit pear-shaped when we got bumped up to a room the size of Norway with an RT60 of about a month. It went a lot more pear-shaped when I discovered we were sharing a room with a headphone demonstration and couldn't plan timed demonstrations as a result.

As you say, most rooms suffered from this problem - some even more than you.

Thanks. I tried as best as possible with that room, but as we both said, the cure here is a lot more treatment, and probably a lot more DSP too, despite the potential issues it might cause on room entry.

[Reffc]

We tried to calm down room reflections and a 40-50Hz bass boom issue by snaffling all the 1ft thick foam sound deadening panels that the hotel staff could muster (yes...they actually had a load in their stores!). What we found was that a happy medium was in reality hard to achieve because of the room dimensions. The boom could be tamed a bit but placing multiple panels on side walls to limit the effect of first point reflections (hence improve imaging and reduce phase distortion) plus some at the back behind the listeners just killed the room dymamics and made the room sound like an anechoic chamber.

The only happy medium we could muster was to leave one large panel behind the listeners (most didn't even realise it was there) and one on a side wall under a white sheet (ditto).

The reality was that without room measurement and targeted treatment (in particlular the ceilings) room treatment was pretty much hit and miss. Things could be improved (and were) but to do the job properly and create an optimally treated listening environment is not something that any of the really problematical rooms (some were much worse than others) could realistically achieve with an evening's set-up.

This was a point accepted by most visitors I think. We did receive some encouraging comments on the clean imaging we managed which was partly down to some targeted minimal treatment, but at the end of the day, hotel rooms are not the easiest of things to treat for all the points so far raised.

[YNWaN]

The DCS room had the best imagery of the show (but then it did have nearly 100K of gear in it) by some margin and they were using quite a lot of passive room treatment including some between the speakers. However, even then they were suffering pretty obvious room issues at lower frequencies.

I would also say that, at very much lower cost, Paul did a jolly good job of taming his room and the Rhapsody speakers did sound much more focussed than many.