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Multi-Way Conventional loudspeakers with crossovers

8" woofer for closed box
8" woofer for closed box
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Old 6th March 2012, 10:34 AM   #1
FilipeRocha is offline FilipeRocha  Portugal
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Default 8" woofer for closed box

Can someone tell me a 8" inch woofer for a closed box ? i would prefer non paper if possible.
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Old 6th March 2012, 12:23 PM   #2
Lojzek is offline Lojzek  Croatia
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Hi Filipe,

There is only one kind of drivers well suited for a sealed box and
these are the ones with high values of Qt factor. There really aren't
many out there to meet this basic criterium. You should be looking
for any kind of driver with whatever cone type you like with Xmax
value high enough for louder playing and Qt in the region of 0,8 .

This holds true for a passive box without any kind of active bass
boosting. Don't forget that published TS parameters are often
more toward lower values than actually measured one. For example,
the specs say Qt = 0,35 but you measure Qt= 0,5

This is perfectly normal because manufacturers often change some
materials in the production process which cause TS parameters
to slightly differ.
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Old 6th March 2012, 12:28 PM   #3
AndrewT is offline AndrewT  Scotland
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An 8" driver in a closed/sealed box cannot be a woofer.
The bass will be rolled off far too high to be an effective bass only speaker.

Look up Linkwitz transform to see how to create a bass only speaker.
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Old 6th March 2012, 12:42 PM   #4
FilipeRocha is offline FilipeRocha  Portugal
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i have 2 12" active subs i can cross with these
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Old 6th March 2012, 12:46 PM   #5
Lojzek is offline Lojzek  Croatia
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Quote:
Originally Posted by AndrewT View Post
An 8" driver in a closed/sealed box cannot be a woofer. The bass
will be rolled off far too high to be an effective bass only speaker.
Hi,

this will be only the case when one uses a driver with strong magnet
and accordingly low Qt factor. It seems to me that many diyers
are blinded by the common practice of building a box with low Qtc.
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Old 6th March 2012, 12:52 PM   #6
lduarte1973 is offline lduarte1973  Portugal
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i cant remember the model but a friend of mine had some JPW speakers with Vifa drivers 8" woofer and they had good bass for the size , cant tell exactly but around 30L sealed boxes.
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Old 6th March 2012, 02:26 PM   #7
John Busch is offline John Busch  United States
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Default 8" seal box woofer?

Curious, there are a few Polypro, aluminum and composite cone 8" woofers suitable for closed box applications.

It comes down to how you intend to use it. Will this be for use in a residence? Sub woofer duties, or part of a 2 or 3 way? Do you have a box size in mind? If part of a multi-way, how high do you think you need to go?

So, fill us in and I am fairly confident there is a 8" out there that will fill your requirements. You may have to consider a paper cone. A lot of strong technical reasons paper cones are the most often used.

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Old 6th March 2012, 02:31 PM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Lojzek View Post
this will be only the case when one uses a driver with strong magnet and accordingly low Qt factor. It seems to me that many diyers
are blinded by the common practice of building a box with low Qtc.
could you explain your reasoning, possibly with one or two examples?
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Old 6th March 2012, 02:36 PM   #9
speaker dave is offline speaker dave  United States
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Quote:
Originally Posted by Lojzek View Post
Hi Filipe,

There is only one kind of drivers well suited for a sealed box and
these are the ones with high values of Qt factor. There really aren't
many out there to meet this basic criterium. You should be looking
for any kind of driver with whatever cone type you like with Xmax
value high enough for louder playing and Qt in the region of 0,8 .
Where did this myth come from?

I hear it repeated from time to time. A sealed box design works with any woofer Q as long as it is a little below what you want the final Qts to be. The lower the starting Q the smaller the box can be (with diminishing returns).

Vented boxes are a little more particular about Q, but they too can be made to work over a wide range. They tend to be easier to achieve with low Q. Is that where the "high Q for sealed" myth came from?

David S.
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Old 6th March 2012, 02:58 PM   #10
FilipeRocha is offline FilipeRocha  Portugal
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I have subs below 80hz . itīs for use in my room from 80 to 250/300hz then crossed to a midrange or full range and tweeter, a 3 way . it will have itīs own box i can go maximum 45L
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