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Multi-Way Conventional loudspeakers with crossovers

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Old 5th August 2012, 05:11 PM   #1
CLS500 is offline CLS500  United States
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Default What am I doing wrong in this box calc.???

Hi all, well I decided to try and build it myself and I already have a problem. I am using the guide here (http://www.instructables.com/id/Buil...ereo-Speakers/) I am planning to use these same componets but want to use a ported cabinet in a larger size for better bass. When I calculate the box volume for the 10" Dayton woofer (DC250-8) using the Qts and Vas figures I keep getting a box volume of 5.9 Cu Ft. This seems much too large for a 10" woofer.. Vas,in liters is 111.4 this converts to 3.93 cu.ft.; using a mulitplier of 1.5 (Qts-0.45). Where am I going off the rails ?? Can this woofer really require a box of 5.9 cu.ft. ??? By the way--I am an absolute, first time beginner at this so please keep it simple. Thank you...
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Old 5th August 2012, 06:09 PM   #2
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Yup, that's the box it needs.
That is a poor design anyway.
You will need to cross much lower for a smooth polar response.
Even with a sealed design, that box is too small. (the one in the picture)
The woofer can't even make it to the xover point.
It should be used as a sub or the bottom of a 3 way.
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Old 5th August 2012, 06:35 PM   #3
CLS500 is offline CLS500  United States
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Thank you Melo theory !!! I think I will dump that idea and try something else maybe using the new Dayton DS-270-8 10" woofer. They have the ported box calc. already done so I can live with that. However, I would prefer using a two way design. Is there a HF driver out there that can crossover smoothly with that 10" woofer?
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Old 5th August 2012, 06:51 PM   #4
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I wouldn't cross any tweeter to a 10" woofer.
I guess you could use a waveguide.
Read about it here.
Zaph|Audio
You basically want the waveguide to be the same size as the driver.
But, if I were crossing to a 10" driver, I would use a 3" full ranger and cross at 600 Hz.

Last edited by Melo theory; 5th August 2012 at 07:00 PM.
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Old 5th August 2012, 07:16 PM   #5
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Quote:
Originally Posted by CLS500 View Post
I am planning to use these same componets but want to use a ported cabinet in a larger size for better bass.
The problem is that any given woofer has a narrow range of useful ported and sealed designs. It isn't possible to improve things over the optimum calculated designs by using different size boxes or ports. In this case you're optimal ported box really is about 5.6 ft^3 and a useful sealed box would be 1.3 ft^3. That sealed box really isn't too bad. I used a Q of 0.9 instead of the (IMO flat sounding) 0.707 standard. The thing will be -3 dB at about 48 Hz.

IMHO, there are a lot of drivers out there that just aren't optimal for home speakers. Also, as said previously, it's hard to get from most 10" woofers to most tweeters. The success of the famous 2-way systems from AR, Advent, Dynaco, Genesis and others, was managing that crossover region. They had the advantage of custom parts to do so.

I usually don't make a bigger leap than tweeter to 5" or 6" driver, and then something larger for the bass. It's hard to DIY a 2-way with extended low frequency response.

IMHO again, it's really educational to look at the response curves of every driver size, from 1" to 15". We tend to have some fixed ideas of what should be crossed to what, but they're often wrong. Having a mid bass driver below the tweeter solves a huge number of problems, other than complexity. The old Dynaudio 17W75 midbass was magic, but expensive. Not sure what's a good solution today.
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Last edited by Conrad Hoffman; 5th August 2012 at 07:22 PM.
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Old 5th August 2012, 07:18 PM   #6
CLS500 is offline CLS500  United States
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I had not thought of the small full range idea !!! Let me look at those and attempt to educate mayself a little. I'm trying to get very good bass extention out of a not overly large cabinet and without the added work of getting into a 3 way set up. But--does a small full range require it's own cabinet volume???
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Old 5th August 2012, 07:30 PM   #7
CLS500 is offline CLS500  United States
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I just need a largeish bookshelf speaker that has very good bass without getting too complicated; that's why I choose the 10" size. If I use the 6"-8" woofer then I am right back into the HT type of three speaker set up using a powered sub; I already have that and would like to go in a different direction. Sounds like I am looking for something that does not really exist.
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Old 5th August 2012, 07:33 PM   #8
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Vifa TC9FD-18-08 3-1/2" Full Range Paper Cone Woofer 264-1062
This is the driver I used for this speaker
The "Event Horizon" (an ambiopole)
Click the image to open in full size.
It does require volume, but not much.

Last edited by Melo theory; 5th August 2012 at 07:42 PM.
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Old 5th August 2012, 10:00 PM   #9
CLS500 is offline CLS500  United States
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My God !!! The "Event Horizon" is just over the top !! Very cool indeed. I won't even try to ask a technical question--way over my head, but it looks bad *** !!
Well I am STILL having a problem understanding this box volume thing. OK--using the Dayton DS270-8 10" woofer as an example-Qts-.44/ Vas-2.99cu,ft,(84.6ltr.) I calc. a box of 4.48 cu ft. But-- Parts express/Dayton says it needs 1.5 cu ft. box measuring 23'' high/14 1/4" wide/8 3/4" deep. See data here: Dayton Audio DS270-8 10" Designer Series Woofer 295-432
What am I missing??? ( This project is a gift to me for my 72nd Bday in a couple of weeks--old dog,new tricks-what ever)
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Old 5th August 2012, 10:28 PM   #10
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Hey, thanx a lot!
As far as PE's box recomendations, Well, it's simple.
They are using a small box. That's why there fb is 40hz.
In the appropriate box, this driver will get down to 26hz.
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