# BFD redlines too easy..



## canaris (Dec 13, 2006)

First of all I has a 2 tempest IB.... which I was pretty happy with in my 275 sq. foot room,then I added another 2 tempest for a total of 4. I was running the 2 at 4 ohms at 750 per and now the 4 at 8 ohms at 500 a pair... the problem is the 4 are barely doing what the 2 were.. :hissyfit: I tried diffrent settings on the BFD ... but that didin't help much...I find it redlines way too easy..even tough the amp has lotsa of headroom left. 

The settings on my AVR for the sub are at 0 db..the attentuators on my Crest 2600 amp are at 2 pm.. I was thinking of running them in bridged mode 4 ohms at 2000 watts ..even tough in an IB they don't need as much wattage. 

What do you guys think?


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## brucek (Apr 11, 2006)

> find it redlines way too easy


Switch the input sensitivity to the higher +4dBu setting..............

brucek


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## Otto (May 18, 2006)

> the problem is the 4 are barely doing what the 2 were


Could something be out of phase?


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## canaris (Dec 13, 2006)

brucek said:


> Switch the input sensitivity to the higher +4dBu setting..............
> 
> brucek



Hey that seemed to work... no more redline..I must have checked those 100 times I always thought they were in the 'in ' position" so I never touched them.. 


I changed both input and output..is that okay...?


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## brucek (Apr 11, 2006)

> I changed both input and output..is that okay...?


The two switches are for the two channels. One for left and one for right.

They alter the operating range from consumer to PRO level, so the input and output maximum level changes to +16dBu (~+4.89vRMS) from +2dBV (~+1.26vRMS).

brucek


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## canaris (Dec 13, 2006)

Brucek..I just read in the BFD manual..to keep the setting to -10 ... is there any loss by putting it to +4?


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## brucek (Apr 11, 2006)

> to keep the setting to -10


Not if the BFD is clipping all the time.



> is there any loss by putting it to +4?


Not if the input level takes advantage of that operating range. If you have an input level that is always clipping the BFD, then you need more room. Hopefully the maximum level with this setting takes advantage of all the bits available. If you're only turning on the first few LED's at maximum input level, then you are losing resolution. Even if that's so, you can't use a setting that clips all the time.

brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

canaris said:


> First of all I has a 2 tempest IB.... which I was pretty happy with in my 275 sq. foot room,then I added another 2 tempest for a total of 4. I was running the 2 at 4 ohms at 750 per and now the 4 at 8 ohms at 500 a pair... the problem is the 4 are barely doing what the 2 were.. :hissyfit:


Not sure what you’re asking about here, why the extra subs are not adding anything, or why the BFD is clipping.



> I tried diffrent settings on the BFD ... but that didin't help much...


What does “different settings” mean? Different filters? That isn’t going to help anything, especially if your amps have headroom to spare. The BFD compensates for response problems, not output problems... 

If the two Tempests were performing satisfactorily, adding two more and doubling the power would have got you something like 6 dB more output. That would probably make them too loud, so you’d turn them down to compensate (maybe that’s why the four are “barely doing what the two were”). The main benefit then would be improved dynamics with demanding passages. And even then you’d only see an audible improvement if your 2-Tempest set-up was running out of steam at times.

But you didn’t double your power. You had 1500 watts total before, now you have 2000. That’s only a 25% increase in power. The rule of thumb with increasing amplifier power is that you have to double it to realize any audible benefit, or it’s not worth the trouble. That’s probably why you aren’t getting more performance than you were before.

Regards,
Wayne A. Pflughaupt


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## PeteD (Sep 9, 2006)

canaris said:


> I find it redlines way too easy..even tough the amp has lotsa of headroom left.
> 
> The settings on my AVR for the sub are at 0 db..the attentuators on my Crest 2600 amp are at 2 pm.. I was thinking of running them in bridged mode 4 ohms at 2000 watts ..even tough in an IB they don't need as much wattage.
> 
> What do you guys think?


If running at +4 creates noise floor problems, put it back into -10 mode, turn your AVR sub out down to the minimum (-10??) and crank up your Crest 2600. Like you said, you still have plenty of output left at the amp. I would not go +4 unless you have to - it sounds like you have plenty of room left at the amp to make up the difference and keep your BFD happy.


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## canaris (Dec 13, 2006)

Thanks guys...I would think that 1000 watts would be enough for 4 tempests in an IB configuration ,after all they are rated at 180 watts each in an IB...I don't want to over exert them but at the same time I don't understand why the 2 sounded better that the 4 ... before I was running the 2 in parallel at 4 ohms per side..now I am running them 8 ohms a pair ...maybe the amp is not optimised for 8 ohms..I will try to run them bridged 4 ohms.. for 2000 watts..thats like doubling them ..just have to be careful in not blowing them. 

I tried this filter settings... 20 +6
25 +6 
32 +6 
40 +4 
50 +4 

That seems to have given it a bit of punch..playing some "chemical brothers" 


I wil try bridged mode tomorrow and let you guys know....


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## PeteD (Sep 9, 2006)

Now I am confused. Are you clipping the input or the output on the BFD?

What did your initial plot look like?

It is not clear why you are using all boost, unless there are a bunch of other cut filters that you didn't share...


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## canaris (Dec 13, 2006)

I don't understand your question Pete about the input/output clipping.... If the BFD goes in the red ,isn't it the output? 

I am boosting to try to get this thing pumping..so I am trying the boost to see if there is any difference...cause running it direct... seems to lack punch.


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## brucek (Apr 11, 2006)

> I don't understand your question Pete about the input/output clipping.... If the BFD goes in the red ,isn't it the output?


The IN/OUT switch controls the filters and the VU meter indications.

Holding the IN/OUT switch causes the IN/OUT Green LED to flash.
Momentarily pressing the IN/OUT switch causes the IN/OUT Green LED to go on and off.

1. Green LED OFF - filters off, VU meter monitors output level.
2. Green LED ON - filters on, VU meter monitors output level.
3. Green LED FLASHING - filters off, VU meter monitors *input* level.

We try and optimize the input level as much as possible with the trim adjustment in the receiver for the subwoofer output to the BFD.

Gain filters will make the output higher, demanding a lower input to compensate to avoid clipping.

brucek


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## Wayne A. Pflughaupt (Apr 13, 2006)

> I am boosting to try to get this thing pumping..so I am trying the boost to see if there is any difference...cause running it direct... seems to lack punch.


As I noted previously, Mike, nothing you do with the BFD is going to fix output problems you may be having downstream.

Regards,
Wayne


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