Testing the DSpeaker Anti-Mode 8033 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 79 Old 06-21-08, 05:09 PM Thread Starter
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Testing the DSpeaker Anti-Mode 8033

Testing the DSpeaker Anti-Mode 8033

The DSpeaker Anti-Mode 8033 is an automatic subwoofer EQ device, it aims to simplify the process of equalising a subwoofer whilst employing advanced algorithms to generate precise filters to counter room modes. It is supplied complete with a measurement microphone. Given my long-standing interest in EQ I bought one to see how well it performs.

The device is very compact, just 126 mm x 80 mm x 28 mm. It has a separate “wall wart” power supply. The front panel has a 3.5mm connector for the measurement microphone; 2 buttons to activate the EQ process, bypass the device or select two bass boost profiles, “Lift 25” and “Lift 35”; and the on/off switch.



The rear panel has a power input, an RCA connector for the sub output from your AV procesor and two RCA connectors for the output to your subwoofer, one of which is inverted (equivalent to setting your sub's phase control to 180 degrees). Usually only one output would be used, though both could be used to drive a passive sub in a bridged configuration with a stereo amp.



The 8033 is for use with subwoofers only. It operates at a 4kHz sampling rate and has a frequency response that is -3dB at 3.3Hz and 100Hz. The response is only relevant when the device is in bypass mode, as it internally applies EQ to give a flat response when it is active. The graph below shows the bypass response.



The processing delay through the unit is 2.7ms, equivalent to 0.9m or 3 feet on a processor's distance setting. Note that the unit has 3dB of gain (the output level is about 1.5 times the input level) even in its bypass mode, remember to recalibrate your sub level after inserting it. THD when fed a 0.5Vrms 40Hz test tone was well below 0.1%.

Operating the unit is very simple. Just connect it up, plug in the microphone and place the mic in your listening position, then press and hold the 2 buttons for a few seconds to start the EQ process. The unit begins with a few seconds of adjusting the level for the mic then starts its sweeps. There are 4 sweeps in total, each lasting 1 minute. Once the sweeps have completed the job is done. It does allow multiple measurements to be taken in addition to the primary position, and according to the manual combine the measurements to deliver EQ that works over a wider area than from a single measurement, though I didn't test that.

I tried the unit out in my lounge, feeding an REL Stadium II sub in one corner of the room, which gets down to about 20Hz in-room. This was the first time I'd measured the sub in there since the room was extensively rearranged. I compared the results of the 8033 with those I got using a BFD (DSP1124P) applying manual EQ. The room itself is L-shaped, with patio doors right across one end.

Here are the results with no EQ (red), the 8033 (green) and then the BFD (blue). Graph axes are from 35dB to 95dB vertically and 15Hz to 200Hz horizontally.



The 8033 has nicely levelled out the two areas of major resonance.

Here are the spectral decay plots for each case, first no EQ, then the 8033, then the BFD.







Finally the waterfalls, no EQ (red), the 8033 (green) and then the BFD (blue).







The 8033 does a reasonable job overall, though I had hoped for a little better. In fairness, this is a very difficult room to deal with. The L shape combined with the effect of the patio doors in one wall and a large window on the wall opposite result in two clusters of closely spaced modes spanning about 23 – 31Hz and 52 – 65Hz. To get the results in the manually applied BFD EQ I spent about 3 hours tweaking, remeasuring and re-tweaking the settings, using all 12 filters and the benefit of many years investigating EQ for subwoofers. I applied no filters above 65Hz as there were none left in the channel I used, although another 12 can be had by looping through the other channel I'd kind of had enough by then . To get the 8033 results I pushed two buttons and made a cup of tea. I would expect that in a more conventionally shaped room it would perform even better.

The 8033 worked well and is very easy to use. I would still strongly recommend that anyone wanting the best from their subwoofer spend some time measuring its performance in the room and seeing the effects of changing its position and/or where you sit, as devices like the 8033 or the BFD can only really help with countering the boost from resonances, they cannot correct the dips that all too often occur at certain positions. Having done that though, the 8033 offers an easy way to get the modal EQ aspects covered.
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post #2 of 79 Old 06-21-08, 05:47 PM Thread Starter
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Re: Testing the DSpeaker Anti-Mode 8033

For the sake of completeness, here are the filter settings for the BFD:



Note that it took 7 filters to correct the 20 - 35Hz region, and in that area a change in filter frequency of less than 0.5Hz can be the difference between working and not working.
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post #3 of 79 Old 06-21-08, 06:16 PM
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Re: Testing the DSpeaker Anti-Mode 8033

Good review John.

I see that the 8033B is 225.00 €, which is about US$350. Not a bad price for something so automatic. I guess with the BFD, you're paid to do all the messing around.

The response is quite good, especially at the bottom end. It seems a lot of sub devices forget that many want that low end extension. I see the 25Hz switch lifts from 15Hz-25Hz and activates a digital filter for frequencies below 10Hz. That's a useful feature for the DIY guys.

I also like the input level warning, that flashes one LED at -3dB and then another at 0dB max. Then it has an anti clipper.....

It has 24 distinct anti-modal filters, so I doubt it would run out.

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post #4 of 79 Old 06-21-08, 06:56 PM
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Re: Testing the DSpeaker Anti-Mode 8033

Fantastic job John. Your time spent on the testing now justifies my purchase of the 8033. The one advantage that I like about the 8033 is that you can run more than one sub with the unit. I have four subs and have had no problmes with the bass.

Thank you, Bill

Last edited by bsoko2; 06-21-08 at 07:12 PM.
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post #5 of 79 Old 06-22-08, 05:33 PM
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Re: Testing the DSpeaker Anti-Mode 8033


All it all it seems like a pretty impressive device. Way simpler than the Velo SMS-1 and almost half the price (those people must be spitting nails right about now!) Not sure how one would do a specific house curve for it, though. On a thread at AVS, one of the DSPeaker company proprietors noted that the "lift" settings were house curve options. Not sure I would exactly call them that...

Regards,
Wayne



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post #6 of 79 Old 06-22-08, 11:57 PM
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Re: Testing the DSpeaker Anti-Mode 8033

Very nice work thank you! Very much appriciate it.

Sounds to me like this is a very good product if it took your experience + 3 hours to replicate what the 8033 does in a couple of minutes. Obviously not for the tweaker.

If you could do a multi position calibration and compare that to what you can BFD I would love to see it.
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post #7 of 79 Old 06-23-08, 08:11 PM
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Re: Testing the DSpeaker Anti-Mode 8033

I think you could use far fewer than 12 BFD filters to get the same or better graph.
post #8 of 79 Old 06-24-08, 03:06 AM Thread Starter
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Re: Testing the DSpeaker Anti-Mode 8033

Quote:
Nate wrote: View Post
I think you could use far fewer than 12 BFD filters to get the same or better graph.
I don't agree

To simply correct the overall level of the frequency response fewer filters could be used, but that would not correct the decay. To correct the decay the filters have to match the modal resonances, it is the resonances in the room that determine how many filters are required.
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post #9 of 79 Old 06-24-08, 05:02 AM
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Re: Testing the DSpeaker Anti-Mode 8033

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JohnM wrote: View Post
I don't agree

To simply correct the overall level of the frequency response fewer filters could be used, but that would not correct the decay. To correct the decay the filters have to match the modal resonances, it is the resonances in the room that determine how many filters are required.
Really?

Is this for to have effect exact resonance freqency more than frequencys around it?

For example I have room modes on both 50Hz and 45Hz. These combined makes quite nasty effect which I have tried to even out with as one big modal peak. Rosponse measurements before and after BFD treatment below.


Even though the responce is quite good when BFD is used, reverbation time is at 50Hz is 3 or 4 times longer than frequencys around it. Even with doublesubs I built after the response measurements above.
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post #10 of 79 Old 06-24-08, 08:00 AM Thread Starter
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Re: Testing the DSpeaker Anti-Mode 8033

You should use one filter for each modal peak. The spectral decay plot is the best tool to identify the centre frequencies of the peaks, the modal resonances show up more clearly in the later slices as the rest of the soundfield decays away. The decay plot also makes it easy to see the effect you are having on the decay time as you alter the bandwidth of the peak to get the best match to the mode, and to check you have the correct centre frequency by trying slightly higher and slightly lower frequencies and measuring the result. To accurately counter a mode the filter centre frequency needs to be within 1% of the mode's frequency. 1% corresponds to 1/60th of an octave, which conveniently is the step between frequencies of the BFD. Your "50Hz" peak might be 49.5Hz, or 49.0Hz etc. You will see the difference in the decay plot provided you have the filter bandwidth narrow enough, try starting at 2/60th of an octave on the DSP1124P (or 0.067 octaves on FBQ2496, which specifies the width differently) while identifying the correct centre frequency then vary the bandwidth once the centre frequency is right.
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