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bose cylindrical radiators

Postby twotoedsloth » Thu Sep 20, 2018 4:50 pm

Greetings,

Does anyone here have experience with the Bose Cylindrical Radiator line of products?

I work at a university, and a few of the faculty members are suggesting that we take a look at these. My only exposure to this system was a tightly controlled demo many years ago. I remember the product rep telling us that due to some fancy physics, the sound volume on stage was exactly the same sound volume, and quality, at the back of the hall, and this obviated the need for monitor speakers.

The largest ensemble that we work with is a Jazz orchestra. Would two or four of these with the appropriate bass modules work in a hall with good acoustics?

Right now we are using 15 inch dual concentric Tannoys, and Yorkville monitor speakers, and we are getting very good results. Would the Bose system represent an upgrade?

Many thanks,

Peter
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Re: bose cylindrical radiators

Postby twotoedsloth » Sun Sep 23, 2018 3:10 pm

Hmm, it looks like nobody is using these. I guess that says something on it's own.

Thanks for taking the time to read this, even if you don't have a connection to this rig.
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Re: bose cylindrical radiators

Postby Wonks » Sun Sep 23, 2018 4:51 pm

I've never used one but they are mini line-array speakers. They are fine in the right environment but they aren't particularly loud. They have a tight vertical pattern and a wide horizontal one so being a bit more more focussed, the sound level doesn't drop off quite as quickly with conventional tops and subs, but it still does drop off.

It's difficult to compare the Bose L1 systems with other types of speakers as Bose don't quote any power or maximum SPL. They always seem to be best matched to fairly quiet acoustic groups and in venues where you don't want too loud a sound.

Because of the line array, the sound doesn't disperse much vertically, so if you've got a hall with a balcony or tiered seating, then above a certain height above stage, the sound level is going to drop off very quickly. So they are more suited for smaller halls with a level floor.

Jazz orchestras can be pretty loud, and I'm not sure that the Bose would be powerful enough to overcome a loud brass section. You'll need four Bose units to get twice the volume, and that will also mean pushing them to their maximum where the sound may get a bit ragged.

Without knowing the size and arrangement of your hall, I'd suggest that your best upgrade would be a purpose designed line-array system with sufficient units to fully cover the hall. But it's not going to be cheap.

If your hall isn't particularly large, then you could ask to trial the Bose speakers. They offer a 30-day risk free trial on their UK website, so if they do the same, you can always speak to your Bose rep and arrange a loan for a week or so at a time when you have a chance to test them in a non-pressured way, at a rehearsal or similar.

It could be that a couple of the Bose systems at the back of the stage could act as monitoring for the stage without the need for monitors at the front, but still using your existing FOH speakers.

I know some people (singer/songwriter types) on the forum have a single Bose column as their PA and monitoring system and haven't had feedback issues, even with the mic in front of the speaker. But you can't beat the laws of physics and once the overall gain of the monitoring system exceeds one, then you will get feedback. Instrument mics facing the speakers will suffer most from this as their cardioid rejection pattern is facing the wrong way.

But if your current system already sounds fine, then there's no pressure on you to upgrade at all, so you can afford to take your time.
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Re: bose cylindrical radiators

Postby twotoedsloth » Sun Sep 23, 2018 6:44 pm

Hello Wonks,

Many thanks for your reply.

The concert hall I most commonly work in has exceptional acoustics, and as such I prefer to use as little reinforcement as possible, so that the musicians can balance themselves without too much difficulty. With a full Jazz orchestra I usually only put mics in the piano, and then in the saxes, trombones and trumpets for solos. And if there is a featured soloists, or vocalist, I'll put out a mic for them as well.

Probably a full proper line array is overkill in a hall that seats 500. As I said, we are getting very good results with mounted speakers for mains, and floor wedges for monitors, with the guitar and bass providing their own amps (and keys if a synth is called for).

It might be disingenuous to demo the Bose speakers as we're not likely to purchase them, especially as we would need to buy at least four, and up to eight of them.

What would represent an upgrade from a pair of Tannoy dual concentric 15 inch mains? I am not too concerned about the monitor speakers. We rented some Meyer Sound speakers earlier in the summer, and they sounded quite good to me, but I'm not sure they are in the budget.
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Re: bose cylindrical radiators

Postby Sam Spoons » Sun Sep 23, 2018 7:16 pm

I have demoed the L1 Compact and echo much of Wonk's findings. They are not very loud, remarkably feedback resistant and produced the best vocal sound I had heard at the time. I suspect it is more to do with fancy DSP than physics as the line array effect can't go very far down into the mid range with a short array and small drivers but they do do certain things very well.

I'd suggest trying a couple to see 'cos in situations where they do work they are very good but I suspect they won't be man enough for your space.

edit to reflect the OP's last post :- If your concert hall has acoustics designed for orchestras, choirs and such like then you probably don't need much amplification, especially if you only amplify piano and soloists. This is the kind of environment the Bose L1 systems are designed for and they would probably work for you but, as has been said, it doesn't sound like they would be an upgrade over your Tannoys.
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Re: bose cylindrical radiators

Postby James Perrett » Sun Sep 23, 2018 7:38 pm

twotoedsloth wrote:What would represent an upgrade from a pair of Tannoy dual concentric 15 inch mains?

I've never used the PA version of the dual concentrics but a friend of mine uses them extensively with very good results. Not knowing the venue we could suggest all kinds of alternatives (none of which would be cheap if you want the same level of quality) but you need to think about what you are hoping to improve with the upgrade. What are the shortcomings of the Tannoys?
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Re: bose cylindrical radiators

Postby BJG145 » Sun Sep 23, 2018 7:45 pm

twotoedsloth wrote:Hmm, it looks like nobody is using these. I guess that says something on it's own.

Not sure about that; you've posted up a pretty specific question and application.

I play with a ceilidh band which uses one all the time, and a Blues band which is about to switch over. The main advantage for us is portability, and for moderate levels in smaller venues they're fine.
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Re: bose cylindrical radiators

Postby Humble Bee » Sun Sep 23, 2018 7:57 pm

I've played through a number of those type of systems and I do like them for vocals acoustics and a Nord Electro f.ex. in smaller venues. The best and most powerful one that I have experienced was the RCF evox 12. Powerful and beautiful midrange and enough power to put a kick through it (there was 2 of them and 150 people big pub pretty loud).
I do much prefer our Yamaha DSR15s tho. They sound insanely good. And loud if needed. But we play rock...
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Re: bose cylindrical radiators

Postby Humble Bee » Sun Sep 23, 2018 8:08 pm

And, as said, they are incredibly resistant to feedback. How is that done? Crazy...
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Re: bose cylindrical radiators

Postby Bob Bickerton » Sun Sep 23, 2018 8:22 pm

Unfamiliar with the Bose, but some years ago got hooked on the Fohhn Linea systems having read Paul’s reviews in SOS.

The Fohhn are (apparently) quite a step up from the Bose, but the same principles apply. Very natural sounding, which is especially good for vocalists and acoustic instruments, very feedback resistant, narrow vertical dispersion (which contains reflections of the ceiling).

They are particularly good in challenging ‘live’ venues.

However, they are not cheap, and, at least where I live, are impossible to trial or hire, so you would not be able to compare with your current system. They do offer a modelling service though. We recently installed an LX220 system into a 300 seater hall which has astounding acoustics for chamber music - think challenging for amplified music - and I’m well pleased. A system like that would set you back US$15,000 maybe.

Bob
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Re: bose cylindrical radiators

Postby Janneman » Sun Sep 23, 2018 9:43 pm

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Re: bose cylindrical radiators

Postby resistorman » Mon Sep 24, 2018 4:37 pm

I've used the L1's in many halls and they work very well. It's true they don't "rock" but for the acoustic based music I usually engineer they are the right tool for the job. On a side note, I carefully raised and aligned QSC K12's just above them in one auditorium that had a balcony and not only did they reach up to it the system actually DID rock. Looked kind of weird though...
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Re: bose cylindrical radiators

Postby artzmusic » Mon Sep 24, 2018 5:46 pm

I have been using the Fishman SA220 which is very similar to the Bose but which some world class jazz artists are preferring over the Bose. The fact that the array sends the sound to the back of room without much drop in volume is a big reason I use it. There is no hot spot which can be irritating if an audience member is sitting there as with a traditional speaker setup. This is all I use when solo.

As regards stage monitor: when working with a group I put the Fishman in the center rear of the stage and it serves as a guitar amp and a vocalists monitor with no feedback at all. With a large noisy crowd I do take a line out from the Fishman to a PA with 2 pole mounted speakers. At the last gig our lead vocalist said it was the best sounding setup she's ever had, and believe me, she's been singing for a long time professionally.

You may enjoy those aspects of the Bose if it fits with your group.

Rick
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Re: bose cylindrical radiators

Postby twotoedsloth » Tue Sep 25, 2018 3:56 pm

Thanks for your replies.

The Tannoys really don't have any shortcomings at the moment. To me, they sound full and natural with depth and clarity. So we don't need to upgrade at the moment. As I said, some faculty members are really interested in the Bose system. Probably they won't go loud enough for some of the more enthusiastic trumpet players.

Yes, our concert hall is designed for chamber music, getting a full Jazz big band on the stage is always tricky. I don't mic every instrument, just the piano, and soloists.

Maybe it is worth getting a pair of the Bose systems, for quieter concerts, for example classical guitar quartets or small Jazz ensembles.

I should ask the powers that be if there is budget, and if so, maybe I can arrange for a demo of the Bose units. If I understand correctly, they come with their own 4 channel mixer, so most of the time I'll need to provide another mixer. How many bass units do you think would be sufficient?

Again many thanks,

Peter
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Re: bose cylindrical radiators

Postby Wonks » Sun Oct 07, 2018 10:43 am

I'm now part way into reading the Mater Handbook of Acoustics as recommended by Hugh and I now understand line-array speakers a bit more. (The following is a bit rambling, but I'm just trying to sum up the differences that I know about between main + HF driver PA speakers and line array speakers).

As well as better controlling the vertical dispersion of the sound, a line array approximates to a line source of sound, rather than a point source (as with a single main + HF driver speaker).

With a point source in 'free space', sound is dispersed in a spherical manner (think of the surface of an inflating balloon). Though the HF horn introduces some directivity into the sound, its wavefront is still spherical. This means that the SPL drops by 6dB for every doubling of distance from the speaker

A line source in 'free space' disperses sound along a wave front with a cylindrical pattern (think of like the side of a tin can that is increasing in diameter but not in height). This means that the SPL drops by only 3dB for every doubling of distance. So to get the same theoretical SPL at a point towards the back of a hall, the sound level by the stage can be quite a lot lower.

E.g. (all theoretically and for 'free space') in order to get a SPL of 90dB at a point 32m away from a speaker at the front of the stage, a point source speaker would need to provide a SPL of 120dB at 1m, whilst a line source would only need to provide an SPL of 105dB at 1m.

That's the theory. 'Free space' is a theoretical environment, only really encountered in good anechoic chambers, or for a speaker suspended in mid-air, a long way from the ground - as the listener would also have to be.

In reality, even outside, there is always going to be the ground to reflect sound, and in a room/hall, there are the walls, floor and ceiling plus any fitments within the space. So there's always going to be reverberant sound that will increase the sound level at any given point. So the 6dB per doubling of distance for a point source in an enclosed space is going to be less, making the loss normally between 4 and 5 dB.

For a line source, that effect will also reduce the loss per doubling of distance in an enclosed space, though because reflections from floor and ceiling are minimised because of the more cylindrical dispersal pattern, the gains from reverberant sound are less.

But a line array speaker like the Bose isn't a perfect line source as it has a finite length, so its performance will be somewhere in between the point source and the infinite line source, getting nearer the true line source the more sections of vertical speakers are used in the speaker design. The spacing of the speakers in a line array is also critical; the speakers can't be too far apart compared to their diameter, otherwise they stop interacting to produce a cylindrical-style wave front but become spaced point sources instead. So to make a line array bigger, you need more speakers in a taller array; you can't simply space the same number of speakers further apart.

Another consideration with a line array is going to be the sub unit. This is going to remain a point source, so its sound will drop off as a point source, and the sound balance as you move away from the stage will vary, with less bass in the sound as you move further away. So there will need to be some compromise with the relative levels of the sub and the line array, so that the best mix is found somewhere around halfway down the hall, with it being a bit bass-heavy near the front and a bit bass light at the back.

But with bass frequencies, you are also going to be open to the effects of resonant room modes, so the levels of bass are always going to be patchy anyway depending where you are in the room/hall, unless the space is so large that the main resonant frequencies are below the frequencies emitted by the subs.

The other benefit of line arrays is the reduced level of reverberant sound, due to far less sound being reflected off the floor and ceiling. The further away from the speakers you are is a room/hall, the greater the level of the reverberant to direct sound. At some point away (which will also depend on the listener's position relative to reflective surfaces) , called the 'critical point', the level of reverberant sound matches that of the direct sound. Beyond that point, the sound quality degrades significantly and good intelligibility in speech is lost and the quality of sound becomes generally muddy. Whilst line arrays don't stop direct reverberation from the sides and backs of a room/hall, they do limit the direct reflections from ceiling and floor, so that the critical point is moved a bit further back into the space. After the first reflections, there will be a certain amount of diffusion occuring, so

There are also the affects of the fixtures, fittings and occupants of the space, and the nature of the walls and coverings. Soft furnishings will absorb higher frequencies, as will people, whilst hard flat surfaces are going to reflect a lot more sound. A space full of people is always going to be a lot less reverberant than the same space with lots of people in. Air will attenuate higher frequency sounds more than low frequency sounds, so distance from the source also determines how much relative high frequency content the sound has to a listener.

Even the best line array will not provide the same sound level at the back of a hall as at the front, as the Bose rep was quoted as stating the Bose array could achieve, but it can (in theory) provide a more even level of sound within the space, with lower sound levels near the front of the hall.

Unfortunately, the acoustics book doesn't cover line array speakers (at least there's nothing in the index), so the above is cobbled together from what it does say and some existing knowledge.
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Re: bose cylindrical radiators

Postby Wonks » Sun Oct 07, 2018 12:22 pm

The larger 'line array' PAs are a bit different again from the cylindrical Bose types, as the individual module enclosures creating the array are often designed to be fairly directional, which means that they can be angled to address different areas of the concert hall, with their output adjusted to achieve a certain SPL in a certain section of the hall, with the modules pointed down at the front of the audience producing less output than those pointed at the back, so that there is a much reduced difference in SPL within the space, and all areas should (in theory) be at the design SPL ±3dB for a well installed and set-up system.

This is an area where well designed and good sounding individual modules don't come cheap, so for permanent installation are really worthwhile for the larger spaces or for use by professional touring PA hire companies. These systems will come with an associated software design package for setting up and optimising the speaker numbers, angles and power levels for the best sound possible. This is something that doesn't come with the low-end array systems.
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Re: bose cylindrical radiators

Postby Sam Spoons » Sun Oct 07, 2018 12:37 pm

As Wonks says WRT subs, the directivity of all speakers (both point source and line array) is frequency dependant and becomes more directional as the frequency increases. With line arrays the length of the array determines the frequency and the frequency that small line arrays like the Bose cease to be cylindrical radiators is fairly high while large LA rigs remain cylindrical radiators well down into the low mids. So Bose L series will probably only be cylindrical radiators in the high mids and up.
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Re: bose cylindrical radiators

Postby The Korff » Mon Oct 08, 2018 9:03 am

Reading this thread reminded me of another one from many years ago, in which Dan Mills contributed his theory about the Bose L series.

Original thread:

https://www.soundonsound.com/forum/view ... p?p=208782

Salient quote (third para especially):

dmills wrote:The inverse square law (for ANY speaker) only applies between the distance at which the wavefront approaches a spherical form and the critical distance at which the reverberant field matches the direct sound level.

A line source array works by being an acoustically long 'slot radiator' which maintains a cylindrical wavefront out to some reasonable working distance, hence only a 3db falloff with each doubling of throw. To do this it MUST be acoustically long (several wavelengths at least) at the lowest frequency of interest.

My guess (And it is only a guess) is that the L1 actually goes the other way and brings the critical distance right down by deliberately trying to drive the reverberant field, thus again getting a more or less flat level distribution in the room, at the expense of some very odd time domain effects. It might manage line behaviour in the top octave or so, but cannot (it is not physically big enough) behave as a line source array down into the mid band.

...which I think is why the Bose systems (unlike many/most others) splay their drivers alternately, as you can see here:

Image

Cheers!

Chris

PS. What became of dmills, I wonder? I haven't seen him post here in a while!
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Re: bose cylindrical radiators

Postby Wonks » Mon Oct 08, 2018 10:31 am

Interesting stuff. It would be interesting to get hold of one and do some level tests.
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