What am I doing wrong in this box calc.???

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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...
 
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?
 
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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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???
 
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.
 
Vifa TC9FD-18-08 3-1/2" Full Range Paper Cone Woofer 264-1062
This is the driver I used for this speaker
http://www.diyaudio.com/forums/multi-way/217096-event-horizon-ambiopole-3.html
Vifa-TC9FD18-08-FR.gif

It does require volume, but not much.
 
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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) :)
 
Alignments are not chiseled in stone and you can fit just about any driver to any one.

Read the compliance scaling article on the ESP website to see how its done.

Unfortunately with the drivers you mentioned a QB5 I seems to be indicated, and this needs an active filter.
rcw
 
Wow-thank you for the response !!! Here's what i'm trying to do. These speakers are going into my garage stereo system. This is a three car finished garage that also contains my gym set up. I have 8 sets of speakers there driven by two amp/equalizer/CD setups using speaker/amp selectors to move between systems. I have all vintage equip. EV/Wharfedale/Cerwin Vega etc. (ranging from small bookshelf up to old 6cuft EV corner units. None were built by me. These speakers are also supported by two 12" and one 15" powered subs
This project is going to sit on shelves, 6ft off the floor and the backs will be against the rear wall.
They will fire across about 25' of garage over the cars toward my gym area. I want to use just a little bit of sub with them, not much. ( I use Paradigm X-20 sub control units to dial in the subs).
So thats where i'm at right now. Looking for nice bass extension in a hefty bookshelf speaker (which will be resting on the long side by the way) using some sort of two way design (the woofer w/full range seems to be the answer for me).
 
Hahaha! Wow, that's a lot of stuff :)
That's all in your garage?
Your a nut!
Well, seeing that they are going to be up against the wall, and they have to reach you at 25ft, I would suggest a waveguide of some sort, to control dispersion. If they are laying on their sides, maybe they can be long and kinda slender?
Maybe an MTM type, with a waveguide in the middle?
Let me think about this for a while, I'm getting sleepy :(
 
Thanks for your help Melo theory, I appreciate it very much. I have read a little about wave guides; I understand that you need a special crossover which has to be fabricated. I would have to have someone make them up for me as that would be well beyond my skill level-so that might be a problem. I would also probably have to consider a round WG horn as these speakers would be used on their sides now but perhaps upright later on.
Yeah--I have a lot of stereo stuff, but then I have been buying it for 40 years and never sold any of it (pack rat). After I retired I decided to set it all back up but my lovely wife said it was the garage or nothing. But then it's really a pretty nice garage; gear is neatly arranged, wires hidden, nice gray and black color scheme blah blah !!!
Again, thanks for your help and I look forward to any further suggestions you might throw my way. Regards.....James.
 
I suggest giving this program a try:

LinearTeam

The 'click and drag' approach is really cool, and I think a big benefit if you don't have a library of 'typical numbers' in your head yet. For fine tuning, yes, use the number entry. (I haven't had a problem with it being "alpha" - hasn't crashed yet)

Putting the T/S specs of the Dayton into WinISD, it spit out 1.3 cu ft for a ported Butterworth alignment, flat to almost 30Hz. Would a 292" long vent be a problem? Using a closed box, you can get a -3dB point of 50Hz if you can squeeze the speaker into a .06 cu ft enclosure.

My thinking is, this is not the easiest speaker for learning box design.
 
In the end it depends what you are after.

For instance this driver can be used in a QB5 II box that you can achieve its full voice coil dissipation with withought exceeding its cone excursion, this is a very loud rock n'roll speaker with a 60Hz. punch peak.

You can also go for an extended bass version which has less output and its limitation is cone excursion.

Typical garage people I know go for the first one.
rcw
 
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