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Discussion Starter · #1 ·
first...please excuse the number of questions i have been asking...but i am in that inverse exponential phase of learning the different factors of designing a diy sub...

i have just come across room gain and how it can "change" the low end response of a subwoofers output...i understand that there are numerous factors involved in how room gain will affect the frequency response as heard by the listener...but typically it can add several decibels to the low end response below some frequency...

taking into account room gain...should i be modeling my design such that the FR plot is not so flat down to the mid to lower 20's before it starts to fall off...by that i mean should my frequency response graph be gradually falling...lets say below 80 Hz...and let the room gain essentially make up for the loss in dB below 80Hz...thanks...
 

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Always ask, that's how you learn the less-hard way :bigsmile:

Yeah your assumption is correct. That's why as a generalization, sealed subs are better for smaller rooms since the shallow roll-off will play nice with the room's effects. "Ruler flat" ported/PR subs would be best suited for larger areas that don't see any significant room gain. You can always start shrinking the volume of a ported sub and watch the range in the roll-off go from a sharp elbow to a gradual change, that could be your control factor for guessing room integration. Keep in mind that ported and sealed subs also have different final roll-off slopes.
 

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Discussion Starter · #3 ·
thanks for the confirmation fusseli...

assuming i am understanding room gain correctly...i feel like the designs and FR plots i have seen are starting to make much more sense...i have seen so many FR plots where the response is nowhere near flat...which i always assumed to be the ideal...actually...the flat response is in fact still the ideal i believe...but flat when measured in room...not necessarily in WINISD...

i guess if the room is very large...then the FR should be designed to deliver a fairly flat response because the in room FR will not be much affected by room gain...and if the room is small...the FR does not need to so flat because the in room response will benefit from room gain below some frequency (dependent on many factors im sure)...

i also assume that this is more of an issue for those without the equipment to flatten out the in room response...

thanks once again...
 

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I agree with all of the above but for myself, I wouldn't mind anything lower then 30hz being a bit louder or flat because our hearing is not as sensitive down low. Especially for effects, more of it! :D
If you want a 'measured flat' response, you can get that, no problem but it's purpose is to 'listen' to it, so why not let your ears decide. ;)
You can always turn down the EQ. Turn it up too, but that's not as good I think. Because now you have to push is.
So my preference is to over-design the sub in the first place.
 

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Discussion Starter · #5 ·
thanks bart west...i think i may do exactly that...design to be fairly flat (within reason as the port resonance, length and air velocity may come into play)...and use EQ to tone down the low end if necessary...
 

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Ah, yes, EQ. A flat reaching ported sub can easily be evened out with some measurements and EQ (like REW+BFD or a receiver with Audyssey).

And to be fair, what I find most enjoyable isn't exactly flat down low :)
 
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