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Old 2nd November 2004, 07:02 AM   #1
Danielb is offline Danielb  United Kingdom
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Default Graph shapes

Can some on show me a good example of a good graph ?shape? for a woofer and a bad example. Ive been using win isd. and looking through loads of woofers. Ive read it all now i understand what it all does but i dont no what chracteristics im looking for?

Thankyou.

Enclosure size im using is 80,000 CC or 0.08 m3 and cut off around 30 to 35.

EG: Which out of these is best

Click the image to open in full size.

My untrained eye says 1 is VERY good? and 2 is very crap?????

Also id say peaks are a bad thing? Am i right?
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Old 2nd November 2004, 12:12 PM   #2
Volenti is offline Volenti  Australia
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The first graph looks good, vented enclosure tuned low I presume?

The second is nasty
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Old 2nd November 2004, 04:11 PM   #3
Danielb is offline Danielb  United Kingdom
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Yeah first is vented perfectly. Its tuned to 30hz but it looks good at 28hz. So any graph tunely like that is good. Now all i got to do it find a cheaper alternative lol. 100 a woofer is a little out of my price range for the first attempt.
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Old 2nd November 2004, 07:15 PM   #4
Ryan_U is offline Ryan_U  Canada
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This is only my two cents but I'd rather have a graph that is flat until 100 hz and then have some drop. You're graph has a drop around 300 - 200 hz which is an area I think you could hear such a drop. I think you should give up some low end (30 40 hz) and have it roll off around 80 where a subwoofer could take over. I beleive that a two way speaker will always need a sub woofer to really balance perfectly.
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Old 2nd November 2004, 07:15 PM   #5
Ryan_U is offline Ryan_U  Canada
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I don't know if this will work... first time posting a picture. Notice that the first graph is dead straight until 70-80 hz where it then rolls off quickly. In my home theater setup, the sub would fill in the 25-80 hz region nicely. In the second graph using the same driver, I have more bass in the 30 -50hz but I lost a lot in the 80-300 hz. Also a subwoofer would still be needed but it would be harder to balance because the speaker is still producing some of these frequencies. Am I making any sense? I might be wrong but a the flatest line possible is what you are looking for. Some spekers though will actually peak in the bass so that they sound more "powerful" in the bass (is that correct?) but true audiophiles want the purest sound reproduction and no peaks or dips.
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Old 2nd November 2004, 08:05 PM   #6
Danielb is offline Danielb  United Kingdom
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Keep the opinions coming people
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Old 2nd November 2004, 08:59 PM   #7
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I tend to agree with what Ryan_U is saying.

If you let winisd calculate the optimum enclosure and tuning that should give you the flattest response. You can then play around with volume and tuning to try and stectch the bottom end a bit.

I try and get it as low as possible, without getting more than about 1/2 DB down anywhere between 100 and 300Hz.... if it only makes a difference of 1 or 2 Hz to the 3db point it probably isn't worth doing, and you are better off just sticking with the optimally flat curve

Tony.

edit: PS. If you post your T/S specs some kind souls might try them out too
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Old 2nd November 2004, 10:26 PM   #8
Danielb is offline Danielb  United Kingdom
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Yeah i see your point. I dont understand how much of a drop in gain is from red to purple line?
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Old 2nd November 2004, 11:01 PM   #9
Volenti is offline Volenti  Australia
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It does depend a lot on how you intend to use the speakers.

I have a set of nearfield monitors set up like the first graph, and for me the extra bass extension far out weighs the (modeled)slight drop in >100hz response (which I can't hear).

Likewise a set of mains that were intended to be used on their own I would tune in a similar manner.

There's exceptions though, you could have tuning to suit a particular type of music, or response taste, and some drivers just don't model well when you try and push the tuning point lower, and the use of a subwoofer as mentioned.

Also the very slight drop in response that's modeled isn't going to be audible simply because there's greater factors at work which affect this area that will swamp it in magnitude (baffle step,room reflections,box resonance ect).
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Old 3rd November 2004, 01:26 AM   #10
madinoz is offline madinoz  Australia
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I think all of the discussion seems to point towards a bit of experimentation. Set your woofer up in a reasonably sturdy MDF box which is bigger than the optimum size shown on the graph, set up a port with an adjustable sleeve to alter the tuning point. Then have a fiddle with it by adding some heavy objects of a known volume (bricks, half bricks?), plug the new volume into the application and alter the tuning point until it looks right. Then alter the port length until it sounds right.
Some times there will be a great correlation between the optimium theoretical
size and tuning points and sometimes there will be a difference. Use your ears and some critical listening material and listen for tune-fullness, timing, timbre and extension (this is the last priority unless you have a sub which you are intending to integrate the speake with).
P.S don't use the mule-box to do crossover tuning unless it is exactly the same size, proportions and shape as your intended finished design.
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