# Two different subs co-located- same frequncy response - possible?



## tdamocles (Sep 23, 2006)

I co-located a BIC h100sub and a new eD sub and found that the frequency response mirrored each other exactly. Is this possible because of room acoustics?


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## tdamocles (Sep 23, 2006)

*Re: Two different subs co-located- same frequncy respone - possible?*

Wow...I should proof read my stuff....


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## Sonnie (Apr 11, 2006)

I would say it is very possible and probable. I symmetrically located my two SVS subs in the front corners of my room and got exact response out of both of those.


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## tdamocles (Sep 23, 2006)

On both graphs the the FR takes a dive at 20hz identically... Is there some sort of subsonic filter on the BFD? Could this be room acoustics screwing with the response?


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## brucek (Apr 11, 2006)

> On both graphs the the FR takes a dive at 20hz identically


What is the low end response of your two subs?



> Is there some sort of subsonic filter on the BFD?


No

brucek


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## tdamocles (Sep 23, 2006)

brucek said:


> What is the low end response of your two subs?
> 
> 
> No
> ...


The subs are stacked. The h100 is on top of the eD. The H100 is front firing/rear port and the eD is bottom firing/rear port. They were both plumbed through the BFD in the bypass mode when these tests were taken. The first is the h100 and the second is the eD. Any comments?


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## tdamocles (Sep 23, 2006)

Not quite identical but close....



The H100 stated specs are 24hz(+-3db)- ?

The eD stated specs are 18hz(+-3db)- ?


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## brucek (Apr 11, 2006)

Did you do your response checks with each sub independently. (one off and the other on)?

Is the stack in a corner?

The response of the H100 seems normal, but the other should be a bit better in the bottom end I would think.

brucek


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## tdamocles (Sep 23, 2006)

brucek said:


> Did you do your response checks with each sub independently. (one off and the other on)?
> 
> Is the stack in a corner?
> 
> ...


Both are stacked in a corner and were tested independently. Seems odd that the FR follows a crossover of 80hz when I have all crossovers disabled.


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## brucek (Apr 11, 2006)

> when I have all crossovers disabled.


Why is that? Normally you measure with the crossover enabled...

Can you expand on your reason or expectation for using two subs - one of which has a lesser response than the other?

brucek


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## tdamocles (Sep 23, 2006)

brucek said:


> Why is that? Normally you measure with the crossover enabled...
> 
> Can you expand on your reason or expectation for using two subs - one of which has a lesser response than the other?
> 
> brucek


Normally I have the receiver doing the duty of a crossover. Since I was testing I just bypassed the receiver and plumbed it into the BFD.

I expected the bigger sub with better specs to be better. Thought I would add the H100 since I had it.


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## brucek (Apr 11, 2006)

> I expected the bigger sub with better specs to be better. Thought I would add the H100 since I had it.


Unfortunately, that's a situation that results in the two subs combining for an overall response that matches the worst sub.

The two subs tend to re-inforce each other at those frequencies that share an equal response between the two. This offers increased headroom at those frequencies. This re-inforcement forces you to turn them down in volume. Unfortunately, the frequencies that don't re-inforce are the ones that are exclusive to the better sub and so the new 'overall' response more closely resembles the challenged sub.

Never combine subs that don't boast the same specifications. It's a loser every time.

brucek


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## tdamocles (Sep 23, 2006)

brucek said:


> Unfortunately, that's a situation that results in the two subs combining for an overall response that matches the worst sub.
> 
> The two subs tend to re-inforce each other at those frequencies that share an equal response between the two. This offers increased headroom at those frequencies. This re-inforcement forces you to turn them down in volume. Unfortunately, the frequencies that don't re-inforce are the ones that are exclusive to the better sub and so the new 'overall' response more closely resembles the challenged sub.
> 
> ...


Yes, I understand......Is it just a coincidence that both subs tested similarly when tested separately? They were not 'both' on when tested...


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## brucek (Apr 11, 2006)

The better sub does show better in the test, but from its spec you posted, it should test a bit better than it did.

Perhaps try moving it around (if possible) and retest. Try for a better bottom end.

Are you using the correct calibration file for your meter?

brucek


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## tdamocles (Sep 23, 2006)

brucek said:


> The better sub does show better in the test, but from its spec you posted, it should test a bit better than it did.
> 
> Perhaps try moving it around (if possible) and retest. Try for a better bottom end.
> 
> ...



Yes, used the Cal file for the old meter since that is what I have. The sub is hard to move around, it is 106lbs with spikes. I'm limited to one spot.....where it is.


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## tdamocles (Sep 23, 2006)

tdamocles said:


> The subs are stacked. The h100 is on top of the eD. The H100 is front firing/rear port and the eD is bottom firing/rear port. They were both plumbed through the BFD in the bypass mode when these tests were taken. The first is the h100 and the second is the eD. Any comments?



The sub(eD sub or the H100) unequalized does not get the 20hz that I hoped for but it does get some in this room. So what I did was set the target response curve to just above the 20hz area(66db) and cut everything to that curve. In the end the sub's volume was reduced but I just turned up the amp to compensate. Will getting my 20hz this way have any ill affects on the sound output? The eD sub is equalized below.


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## brucek (Apr 11, 2006)

Your approach is correct, and will usually work fine as long as the sub in question has the ability to reach as low as you're attempting to equalize. By this I mean that you can't successfully equalize a sub to produce 15Hz if its +/-3dB specification was 25Hz. But, it the sub is designed to go that low and is not realizing its potential because of a poor location, then this method of pushing higher voltage at low frequencies can certainly work.

You've gone about it exactly the correct way of *cutting* the highs and then compensating by increasing amplifier gain. As long as the headroom is available in your sub amp, it should all be fine. The alternate method of applying boost at the BFD is simply a bad idea.

brucek


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