Subwoofers & DSP or nearly bye bye room

[Reid Malenfant]

Ebay very kindly supplied me with some vouchers recently that gave me 15% off of anything over £100 & up to a maximum of £100 reduction

This happened to cover six categorys & luckily for me one of them was "consumer electronics" So naturally i went looking about on the off chance that i might see something interesting & oh boy did i just...

Cutting a not too long story down to the bone i found a DSP device that is designed to be connected between a pre amp & subwoofer. This device feeds the sub with swept test tones & listens to the results & then modifies the output to the sub to get rid of room modes & tighten up the transient response. Or if you like it near as damn it gets rid of the room Now this is only suitable for active or if you like powered subwoofers which operate below 150Hz.

It can't be used with a standard pair of passive speakers, though it could be used with a passive sub if you found a suitable power amplifier or plate amp if building your own...

Introducing the Antimode 8033c Subwoofer EQ...

Now while i haven't installed the pair of them yet (yes Mark needs two of them with two active bass units) i have absolutely no doubt that these are going to make a real difference to proceedings. These things do not boost output at any frequency (though they have an overall 3Db of gain), they only cut & cut out room boom by EQing in the digital domain where a lot more can be done than with any analogue filter

As soon as i'm strong enough to change out the Behringer CX3400 for the pair of DCX2496 i'll install these as well & see what they do, they should eliminate the room mode i have at about 40Hz & tighten things up nicely

Here are few reviews just incase you are interested..

http://www.hometheatershack.com/foru...de-8033-a.html

http://www.avforums.com/reviews/DSPe...EQ-Review.html

Oh, cheers ebay for saving me over £64

[HighFidelityGuy]

Nice one Mark. I'll follow this with interest as I've fancied trying one of the Antimode EQ's. I'm also planning on experimenting with a sub-harmonic synthesizer soon. It adds in extra harmonics below those already present in the music to add that extra infra-sonic feeling you get at gigs. I'm guessing that sort of thing is up your street. I'll start a new thread once I've got all the equipment together.

[Reid Malenfant]

Hi Dave, i'm not too sure about that in all honesty, the added (sub) harmonics thing i mean Not sure i'd need anything like that in all honesty as i have quite a bit of music with heavy sub 25Hz content & a lot of that is sub 20Hz, so in certain respects i don't need to make what isn't there as it already is

Besides which if you are going to try this thing out you'll need to use a speaker that can actually reproduce whatever frequency it is producing. If you are going to run some kind of reflex speaker then make sure it's tuned really low (like an LLT) or you may find that you are just moving the cone & cancelling via the port.

More on LLTs (large low tune) in the future

More on the 8033 as well once i feel up to pulling a load of kit out of my rack & fitting them in...

[HighFidelityGuy]

I know what you mean, I too have a lot of music with a lot of very low bass. The sub harmonic synthesizer is more for the music that doesn't have it on the recording but probably would have it live. I have a pair of sealed 10" subs that I already run with a crossover at 35Hz. They're 250W each but I have a spare pair of 550W mono blocks to play with too. It's just something I've fancied trying out for a while as a daft experiment.

If it works out my subs will be getting more signal more often, so that got me wondering if I would then need to add some finer EQ control over the sub frequency band to keep things under control. I'll see how it works out.

[Reid Malenfant]

Well i guess most depends on the room, but to a certain extent on the bass drivers you are using. If they are something like the 10" Peerless XLS then they are very low Q & room modes will predominate. drivers with a higher Q that result in a closed box Q of more than 0.6 (definately over 0.7) may well benefit.

What i'm interested in is getting rid of the room modes & speeding up the bass due to much faster decay, which is exactly what it appears to do. Bass this way is no slouch either so it should be very interesting indeed

[Reid Malenfant]

Dave, you'll be interested to know that i have have the pair of these installed, working & calibrated

I'm not going to give too much of an opinion right now as i have literally just settled down, i hurt rather a lot & i have only spun a couple of tracks so far...

What i can say so far is that the difference is in no way subtle & the reviews appear to be dead accurate The room modes appear to have gone, i can hear clearer differences in bass tones & things are even faster & less ponderous in the bottom end.

That's it for now I'll be back

[Reid Malenfant]

Ok, i'm beginning to get a real handle on what these things are doing now so time to spill the beans a bit

One thing i can say with utter conviction is that room modes are eliminated! I have spun so many discs since installing them that it must be statistically nigh on impossible that i haven't spun something with approximately 40Hz output (which is where i had problems previously). Lets say it is very conspicuous by it's absence

While these little boxes only have the ability to cut certain frequencies (they can't boost anything to equalise) there is a rather surprising increase in deep bass right down to the cutoff of my Paradigm DSP-3400 sub. Actually it's not an increase at all, it was just that the room interaction was masking the deep bass notes, now every note is clean & easily heard

I'd go so far as to say that i'm quite frankly astonished at the difference these things have made considering the type of loading that the drivers are under, no reflex here - a 4th order coupled cavity gives a similar response to a sealed box

I find myself listening at a generally slightly higher level simply because there is not a tad of muddiness in the bass, in my system this is below 110Hz. One positive side effect of this is that i can clearly hear when one of the 12" drivers inside the enclosures runs out of excursion! Normally this would be masked by the overall volume/room effects etc. Now it's as plain as day, no way is it down to the amplifier clipping as i can feed the 12" Yamaha drivers with over 600W RMS of power each if called for from the Mackie amplifier They'll happily go with 300W RMS on peaks without complaining

There is no two ways about it, this is the cleanest bass i have ever heard fullstop!

I only put this thread in the AV section as the 8033 is only effective below 150Hz which is generally going to restrict there use to subwoofers. As i happen to run four way active speakers the opportunity was there for me to use a pair of them below 110Hz. I calibrated each one (one per channel) which is simply a case of positioning a microphone in what would be the centre of your head at ear level & pushing two buttons at once for a few seconds. The 8033s did the rest, oh boy did they

I'd more than happily recommend these things to anyone - in a big way! Perhaps anybody that is considering small stand mounted speakers might think about adding a sub & one of these or two subs (in a way similar to my system) & a pair of them. It might not appear cheap, but even if purchasing a pair you'll likely end up with deeper (only as deep as the sub can perform) cleaner bass than is possible with any loudspeakers without the same kind of DSP...

Or do you own the Albert Hall?

[Clive]

Some of my DSP journey can be seen here:

http://theartofsound.net/forum/showt...=system&page=2

Since then I've damped the corner of the room beside the left speakers, this dramatically cut the decay time. I've also suspected that my bass is better with the door to the room open and I now have the graphs to prove it!

I'm not too sure how well the Antinode auto setup does and whether you can tweak the results. The initial results with my XTZ room measurement kit are good but can be significantly improved on with some manual tweaking once a rough setup is done. I also had good results with a DEQ2496.

For those with less problematic rooms an analogue option look interesting, there's a kit http://sound.westhost.com/project84.htm

[Reid Malenfant]

Hi Clive, cheers for popping in The only way of tweeking the Antimode is to do a second "wide" area response. Frankly i'm not bothered though as this is very good indeed.

I can't measure it as i don't have a PC program etc but the response in room here should now match what the Paradigm sub is capable of, IE 15Hz -6Db & it's all clean

The Antimode starts off it's calibration at 16Hz, it's a pure sine wave but it's interupted/pulsed so that it can listen to how it decays in the room. I guess this is how come the waterfall images & sound decays so much faster than standard after the 8033 is calibrated. It runs a 16Hz to 150Hz pattern 4 times before it's happy, all these are at differeing volume levels & stuttering as i call it

I reckon it takes about 3 minutes to run through the lot, but at the end of it it's a new world of clean, deep bass reproduction!

[Clive]

That's fairly similar to how the XTZ combination works, though it's not quite automatic in that you have to upload the parameters from a PC to the DSP. My room is especially tough as it's 15' square with a bay tacked on at the rear. The ceiling is low at about 6' 9". The room modes are horrible hence my needing to tweak settings. DSP is great for the bass, I'm very much a believer in it!