Beachtek DXA-8

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Alan Craven
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Joined: Jan 26 2001

Does anyone have any experience of using this XLR/3.5 mm adaptor? It offers various extras above the usual DXA-4, but the thing in which I am most interested is the limiters.

I would use it mith a K6/ME67 combination. With my new XM2, this is fine for relatively loud sounds, using the mic attenator and gain controls on the camera, but it is impossible to deal with a sudden loud sound intruding. A learnt this whilst filming some wigeon, which were whistling quietly, with the levels set to give about -12 dB, when a mallard suddenly let rip at close quarters. The results are horrendous.

From the figures I have the limiters can reduce the gain by about 21 dB with only 0.5% THD. This distortion rises quite rapidly after this.

The problem is cost, around £385 here, but a mere $385 in the States!

They are available from LTF, who at present have no stock.

Dave R Smith
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Joined: May 10 2005

This thread deals with post production side:
http://forums.dvdoctor.net/showthread.php?t=35031&highlight=attack
but from this I learnt from Reds that 'Attack' is the control to quickly come in and reduce level for Donald Duck.

I can't see attack on your selected model.
http://www.beachtek.com/dxa8.html

I suspect the answer maybe 2 mikes, so await feedback with interest.

Alan Craven
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Joined: Jan 26 2001

Thanks, Dave,

but I want to sort this out at the recording level, I have tried various tactics with Audition, which improve matters, but Donald still is distorted.

I have got the manual for the DXA-8 and this certainly will do what I want. This is confirmed by several threads from users on the DVinfo site.

My sole concern is, is it worth the extra cost over the DXA-4, which would enable me to control the gain so that the XM2 inputs are not overloaded by Donald (the XM2s own gain controls do not do this, they only control the output of the pre-amp). This will make Donald OK, but the background chorus would be at -45 dB.

Alan Craven
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Joined: Jan 26 2001

Well, I have taken the plunge. My DXA-8 arrived from LTF this morning, and I have been playing with it under controlled conditions with various of my recorded sound tracks. The camera/Microphone/Century teleconvertor/Beachbox looks most impressive! Fortunately it sounds just as impressive.

Edited tracks with Mallard calls normalised at -3dB can be recorded on the XM2 via the ME67 with the limiter on so that they are still limited to -3dB, but the background chatter level in the XM2 can now be as much as 12dB louder than on the recording, without overloading the XM2 inputs on the peaks. With the limiters off, the Beachbox gain has to be backed off or the camera audio is clipped with clearly audible distortion.

Another big plus is that I can now use the K6 with the XM2 MIC Attenuator off.

Now to try it in the field!

Dave R Smith
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Joined: May 10 2005
Alan Craven wrote:
Edited tracks with Mallard calls normalised at -3dB can be recorded on the XM2 via the ME67 with the limiter on so that they are still limited to -3dB, but the background chatter level in the XM2 can now be as much as 12dB louder than on the recording, without overloading the XM2 inputs on the peaks. With the limiters off, the Beachbox gain has to be backed off or the camera audio is clipped with clearly audible distortion.

Are you saying that the limiter slider switch always suppresses over-modulated sounds to -3db, or you have personally set it to -3db?
For a true test, the Donalds will hopefully come in abruptly, to see if the Beachbox re-acts near-instant or cuts in a tad too late to avoid distortion. I believe having the response/attack too high (which I guess is buit-in non-adjustable hardware here) can affect the rest of the sound - like you wigeon.

You may have to reduce levels when you let rip with your Purdey.:D

Alan Craven
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Joined: Jan 26 2001

No, what the limiter appears to do is offer variable control of the maximum output voltage of the Beachtek. Peaks are indicated by a red LED flashing. It is just visible with an output of 4 mV and fully bright at around 10mV. This suits the XM2 with the mic attenuator off.

I set the gain on the Beachtek so that the LED flashed brightly when the Mallard yelled - I chose a track where this occurred repeatedly and has a sharp attack (viewed on Audition).
I then used the XM2 audio gain controls so that this gave a -3 DB peak on the XM2 meters. The levels indicated on the XM2 meters suggested that the background bird chatter was around 12 dB higher than on my original - which was recorded withthe same set up, minus the Beachtek.

In practice the Beachtek has zero gain with the gain control at its mid-point. The spec gives a range of -10dB to +15dB. I used it at zero gain for my tests.

It uses a PP3 battery and will provide phantom power to both channels.

Dave R Smith
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Joined: May 10 2005

Right - got you - good luck with the field test.
I'd also be interested in any feedback on human voice which is suppressed by the beachtek on loud spots. If the resulting sound is 'off' in any way, it will be more apparent than the mallard, so will give a better measure of the beachteks capability.

Alan Craven
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Joined: Jan 26 2001

Even though my edited stuff never has a human voice on it, I should be able to tell you what the voice situation is once I use the gear in an RSPB hide. The majority of birdwatchers clearly believe that since birds have no visible ears, they cannot hear!

When I first started 35 mm photography in their hides I used a 400mm lens. I now have to use the equivalent of 1600mm to get the same size image, the birds are so much further away.

As you say, The mallard is more or less a repeated "bark", and whilst serious clipping is obvious on 'phones I doubt lower levels of distortion are evident.

Apparently the limiter is capable of reducing the gain by -21dBV with ca. 0.5% THD, but this rises rapidly for higher level signals and if the input is too high it can clip the signal. Not surprisingly, they say that the lower you set the channel gain, the higher the input signal it can accommodate.

Dave R Smith
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Joined: May 10 2005

Feedback noted - thank-you.

Alan Craven wrote:
When I first started 35 mm photography in their hides I used a 400mm lens. I now have to use the equivalent of 1600mm to get the same size image, the birds are so much further away.

Because hides have to be buit further away allowing for noisy twictchers - or the birds habitat is further out in estuary?
I would have hoped better technology meant better pictures.
What convertor do you use - is resultant picture noticably darker and what's depth of field like. I have an Xm2, but haven't used it to-date for distant/small wildlife.

Alan Craven
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Joined: Jan 26 2001

When I posted I was thinking of two or three particular hides, which have not changed significantly over the years. The birds are simply further away. If you get into a hide in the early morning, the birds are often up close, but you can watch them move away as people enter and the noise builds up.

Untl a month ago I used the Sony 1.7X convertor that I have on offer in Classifed. I have just bought the Century 2X convertor. This is a better lens design and better resolution and apart from some chromatic aberration at maximum zoom, out-performs the Sony comfortably.

The downside is that due to the smaller diameter lens elements it suffers far more from vignetting. With the Sony you can use maybe 60% of the zoom range, but with the Century it is more like 40%. This means that the lens has to be removed and replaced more often. Unfortunately this is one of the Century lenses that is screw mount rather than bayonet using the Lenshood mount. Not good news for the plastic 58mm thread on the Canon's lens. You also have to remember that the recorded field of view extends well beyond what you see in the viewfinder.

The Sony did not affect the exposure value noticeably. It is too early for me to judge the Century, but my remarks above about the diameter make me wonder if it will have the same light gathering power. Depth of field is difficult to judge at these focal lengths as it is small anyway. The IS is far less effective - I sometimes think it does not work at all - with the convertor in place. A pity, when the extra focal length makes it more useful.

Dave R Smith
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Joined: May 10 2005
Alan Craven wrote:
If you get into a hide in the early morning, the birds are often up close, but you can watch them move away as people enter and the noise builds up.
Quote:
A suggestion for the hide owners - Put rubber matting down - as well as reducing sound of boots it should reduce cold. On the doors stick some foam draught strip. As well as keeping draught out is stops door 'thudding' when it shuts.
I have glued rubber pads to the corners of kitchen cabinet doors to stop them banging when they close on the spring.

I'm assuming the century's 40% effectiveness is at the upper end - otherwise it would be useless.