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Discussion Starter · #1 ·
Hello people, I hope for my first thread here someone can help with my first DIY build. I have posted similar questions on AVForums, where I first started my build, but I thought I'd post here as well with my problems as I think I may need a fresh perspective on things.

It's been a bit of a frustrating journey so far to be honest, starting with the 5 months it took for my drivers to arrive. I built my subs with the aim of them being something really special, so I built two boxes each containing two AE AV15-H drivers - so 4 drivers in total. The drivers are dual 2 Ohm drivers, with the VCs on each driver being in series (so each driver is 4 Ohm) and then the drivers wired in parallel within each box, so each box is a 2Ohm load. Each box is sealed 95L with some stuffing to bring up the apparent box size to around 120L. This is wired up to a Behringer EP4000. That size box models very well in Win ISD, when a BFD is used with a 4dB boost at 20Hz and a 15dB cut at 55Hz.

I initially had an issue with the wiring where I had stupidly accidentally put a sort of jumper across the VCs on the drivers, so a tiny tiny noise came out, and it was obviously clipping the amp with minimal input as there was effectively a near zero Ohm load. Once I figured that out I removed these jumpers and it all started working.

Now at first I thought that the sound was quite good, and working normally, but as I have listened to it over the last week or so I have come to realise that the upper bass is very 'thumpy' and there is very little by way of low bass - i.e. anything under about 35Hz. It just seems to cut out below that level, and I think it's my turning it up to get that low bass that has made the upper bass too loud.

I have tried, so far:

1. Various different filters on the BFD, and bypassing it entirely.
2. Connecting up only one box, and then even disconnecting one driver so that only one driver is playing.
3. Using a Samson S-Convert to get the line levels matched, as at one point I thought there may be a problem with the line levels not being matched.
4. Changing the dip switches on the EP4000. The switches for the HPF were set to 'off', but in order to check the manual was correct I tried turning them to 'on' to see what happened - and where before I got something below 35Hz ish (although very quiet), I now got nothing.
5. Getting someone else to come over and check my wiring, and they are fairly happy I've wired it all up correctly too.

I honestly can't think of anything else that could be the problem. There is no EQ on my AV amp (Denon 2307) and my BK Monolith, in the same position a week ago with the same AVR and same settings on the AVR played just fine down to 20Hz.

I'm really tearing my hair out as I wanted to build something absolutely awesome, and it turns out, at the moment, to not be as good as my previous £430 subwoofer, despite everyone along the way telling me this should be an incredible sub.

Does anyone have any other ideas? Could I have damaged the amp when playing into an effectively zero Ohm load for a short period, in such a way that it just damages it's low frequency output? Is there any way it could be the drivers themselves?

Help! Thanks,

Alex
 

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I remember a surprising rolloff when looking at the AV15Hs, but you should still get good output. So sealed box, models pretty well in WinISD... Hmmm.

Have you tried test tones (20-25-30 hz) w/a DB meter to see if you can get a better idea of what works and what doesn't?

I can't think of anything immediately wrong. If you put a load like that on the BFD, I believe that it's protected enough that you shouldn't have damaged it. I know some EP2500s had the labels for the filters backwards, but I don't believe the 4000s have any problems. You tested that too..

How is the amp wired? Stereo? Bridged?

If you have a multimeter, you could check the speakers too, make sure that they read the approx number of ohms correctly (that would verify the wiring job)
 

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Welcome to the Shack,
We have a program called REW which allows you to plot the response of your driver using your pc's sound card. http://www.hometheatershack.com/roomeq/
All you need is an appropriate mic or spl meter as per the instructions. This will tell you exactly what is going on with your sub.
 

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4. Changing the dip switches on the EP4000. The switches for the HPF were set to 'off', but in order to check the manual was correct I tried turning them to 'on' to see what happened - and where before I got something below 35Hz ish (although very quiet), I now got nothing.


If it's anything like my QSC, the hypass filter cuts the bass below 35hz. You do not want this on to get bass below 35hz, ie make sure this is off. That's why you're getting nothing below 35hz.

Check to make sure everything is wired in phase, positive to positives and negatives to negative.

Run REW or manually take frequency graph with a RS meter to check, then plot. There is an excel sheet that will make the correction for you. I'm sure someone here knows where that's at, sorry I do not.

Can you post the theoretical graph for the drivers from your model? If your box is too small, maybe they're rolling off early and you're not getting any room gain.

How big is your room?
 

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Discussion Starter · #5 ·
Apparently I can't post links or images yet as I don't yet have five posts, but basically the WinISD graph, with a 4dB boost at 20Hz and a 15dB cut at 60Hz shows flat to 25Hz, then -3dB at 20Hz, -9dB at 10Hz.

What REW shows I'm getting is reasonably flat to 40Hz at 73dB, then a 13dB drop between 30Hz and 40Hz, and then flat at 15-30Hz at 60dB, 13dB below the rest of the bass.

What I don't understand is that my previous sub, a single ported 12" sub, which according to WinISD has less bass than my current subs even at it's tuning frequency of 20Hz, had solid bass down to around 18Hz, so it can't really be a room issue. My room is 7 x 4 x 2.8 metres.
 

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I modeled it in WinISD. I used the values from here: http://www.aespeakers.com/phpbb2/viewtopic.php?f=4&t=2697 (Not sure if they're 100% accurate)
Yellow is 95L sealed, red is 120L sealed. Each with 2 AV15H drivers.

The SPL is w/1000w.
Note: I didn't apply any EQing.

I know the EP4000 is good down to about 5hz, since I've seen 8 hz w/my subs. Tripped a breaker too! :)
 

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What REW shows I'm getting is reasonably flat to 40Hz at 73dB, then a 13dB drop between 30Hz and 40Hz, and then flat at 15-30Hz at 60dB, 13dB below the rest of the bass.
If you're using an RS meter, you might want to make sure that you are using a calibration file for the meter (I had to google for one last time I looked). I know that some of the offsets are 5-20db from what the meter reads. I found REW values basically meaningless without the calibration.
 

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Discussion Starter · #8 ·
I need to get an RS one as I only have a cheapish one from Amazon. That said, what REW shows sounds like what I think I'm hearing...
 

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How air tight are the boxes?

Just trying to see if we can rule out anything.. Not that I really think that air leaks would have that amount of impact.

And do both boxes perform exactly the same if you play them one at a time?
 
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