Closed vs Ported Woofers-
- Thread starter HomeBody
- Start date
Register to hide this ad
dc270
Now Off the Reservation
There are computer modeling programs available on the net that you can plug in the woofer parameters to see what a given responce will look like! This is very helpful in woofer selection so you can see the impedance & frequency responce curvers. The "curve junkie" Zilch would concur with this I bet!
Parts Express also has several software programs ( I use their Eminence modelong prohram!) and they also have woofer testers to actually measure what you have! I also use the woofer tester to verify what I find in various driver products. Software is nearly always money well spent!!
DC
Parts Express also has several software programs ( I use their Eminence modelong prohram!) and they also have woofer testers to actually measure what you have! I also use the woofer tester to verify what I find in various driver products. Software is nearly always money well spent!!
DC
HomeBody
Passion not Critisism
Ah- Haaaa....that rings a serious bell in my cob-webbed mind as I recall some reading of recent.:scratch2:
Coytee
Super Member
Best answer so far.
I would suggest doing this, paying the piper and know you're going to do it right from the git-go.
TerryO
Super Member
Like Dave and Coytee have said. If you want them to sound their best then you should get the drivers that will work best. Too many times people that have a vague understanding think that drivers can be swapped out because:
1. They're the same size
2. Have similar magnet weight
3. Look alike, or at least somewhat similar
4. Same color
5. A salesman told them it would work
6. Someone said it's a really good driver
The thing that's important is the implementation (in this case, box design) based on the driver's measurements, not the other way around.
Best Regards,
TerryO
Nope......it is not the opposite. I would add that closer to the .5 QTS is better for smaller Bass Reflex while .25-.35 is better in the larger volume cabinets.
karlo
Super Member
HomeBody
Passion not Critisism
Good Mornin' DC-
You wouldn't opt for a higher quality driver...?
Karlo had the same idea I was pondering.
dc270
Now Off the Reservation
I am sure the engineer had good reasons for that particular woofer in that box design!
If you want to redesign then be prepared for comprimises/ trade offs.
Measure the actual volume of the woofer/ cavity
Look at driver specs that would reasonably fit that volume & offer acceptable responce- here a modeling program would help.
How will the driver integrate with the network & other drivers SPL?
For me- you can only milk so much from a cow- then move onto another cow. The Mach I/II design lends itself only so far in reasonable modifications. I would rather spend my money in a ground up custom design, or perhaps a better platform like a Klipsch, etc that would allow mmore flexability, creativity as all the other components would allow. It is more than "what fits the hole" as it is why it fits the hole........to me anyway.
DC
dc270
Now Off the Reservation
That's my point. After studying a cabinet's current volume, looking at available speakers...you wouldn't opt for tweaking a cabinet's physical features to today's speakers sold?
Sure enough there may be better woofers out there- why not surround those better woofers with better drivers as well? The Econowave being a good example!!
DC
Nope. High compliance in Acoustic suspension is correct because the Sealed air in the box IS the compliance. Low compliance in what could be considered as APPROACHING an open back enclosure. Think of it as opposites attract.....a loose(high comp) speaker in a tight box or a tight(low comp) speaker in a loose box. Low QTS means that the combination of electrical and physical design causes the speaker to have a natural stiffness. Your verbal description is correct but you are assigning the QTS numbers incorrectly. .2-.4 is low compliance and .5+QTS is high compliance.
dnewma04
The Healer
One of the common ways to differentiate whether a woofer is more suited to ported or sealed enclosures is by calculating the Efficiency Bandwidth Product or EBP.
You calculate by dividing the drivers Fs by the Qes. The higher the number, the more suited to ported enclosures the driver becomes. Under 50 or so usually indicates good sealed box performance. Over 100 pretty well relegates the drivers to ported enclosures.
This EBP method is nothing more than a basic guideline and shouldn't be considered gospel.
You calculate by dividing the drivers Fs by the Qes. The higher the number, the more suited to ported enclosures the driver becomes. Under 50 or so usually indicates good sealed box performance. Over 100 pretty well relegates the drivers to ported enclosures.
This EBP method is nothing more than a basic guideline and shouldn't be considered gospel.
ken kantor
Fowl Humor
Finding the right woofer is a very complex task, as others here have pointed out. In my experience, there are no short cuts or rules of thumb that are particularly useful. By far, the best thing to do is pick a woofer that has been field-proven in the design.
In very general terms, the woofers used in sealed boxes usually have a higher Qts and a lower Fs, (higher mass, higher compliance), than those used in vented designs. But, so much depends on the desired response, the size of the box, the way the driver's suspension works, etc. Even if you try to go by the numbers and use modelling software, the predictions will be somewhat iffy. Specs like Fs, EBP and Qts are >small signal< parameters that don't tell you all that much about how the woofer behaves at even moderate levels. Further, they tell you >nothing< about how the woofer performs above the resonance region, or mates to another driver.
-k
"The Internet: Spreading Misinformation Since 1963!"