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Speaker box design without specs?
- Thread starter Katalyst
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Considering how much work you will do building two (I presume) cabinets, I suggest you buy new speakers from Parts Express that can provide a complete list of Thiele-Small parameters with it. Someone else here can show you how to proceed and select the correct one.
nexus
Super Member
it helps to know the Qts too at least. with a t-line it's VERY complex to design but you can experiment with different lengths of sonotube and stuffing...i am talking a a lot of experimenting.
with a sealed box it's much easier. if it winds up too small you can even turn it into an aperiodic by making small holes in the back and covering them with foam or Fiberglas.
but you will not get as much extension.
that's it.
with a sealed box it's much easier. if it winds up too small you can even turn it into an aperiodic by making small holes in the back and covering them with foam or Fiberglas.
but you will not get as much extension.
that's it.
bowtie427ss
Lunatic Member
Once you have all the T/S parameters precisely in hand for the driver you want to use, the precision ends there unless you have the ability to measure/analyze your final product.
The best box modeling software out there still only provides you with a prediction/estimate of system performance. To create a truly great speaker system, analysis and adjustment continue well beyond the modeling stage.
The best box modeling software out there still only provides you with a prediction/estimate of system performance. To create a truly great speaker system, analysis and adjustment continue well beyond the modeling stage.
mhardy6647
Lunatic Member
DISCLAIMER: all of the following opinions are decidedly non-modern and are, in fact, merely opinions not immutable facts!
Well -- it's actually fairly straightforward to measure (estimate) Thiele-Small parameters with fairly simple tools (even simpler, given that nowadays a computer or probably even a cell phone can be one's "Signal Generator"):
http://sound.westhost.com/tsp.htm
Armed with T-S parameters, one may calculate a box and crossover with simple tools. As implied in another post above, build according to the models and you'll likely get something akin to the Toyota Camry of loudspeaker systems -- perfectly competent and unprepossessing, but doubtless lacking the spark of greatness.
That said, one upon a time the understanding of dynamic loudspeaker driver performance was more empirical/holistic than the Thiele-Small model (which, it should be borne in mind, is a model -- using a few simple parameters to model the complex frequency-dependent behavior of an electromagnetic motor wiggling around a diaphragm to make noise!). Indeed, in the old days, speaker cabinets were fairly generic, and tuning was done by ear -- or the "system builder" simply took what he/she got, and liked it!
Look at 1950s/1960s catalogs and you'll see that drivers and enclosures were often sold separately, and enclosures were meant to be generic, accommodating a broad range of typical drivers (woofers) available at the time. www.radioshackcatalogs.com www.alliedcatalogs.com and www.hifilit.com are all good sources for such "information".
Now, back to the OP's driver -- what is it, by the way?
In the absence of ANY other information about the speaker driver -- look at the woofer. Is the magnet big (heavy) or small? (Note, all bets are off with a neodymium or other 'rare earth' magnet; they're very strong magnets per unit mass)
If it is small, the Qts of the driver is probably fairly high, and could be accommodated on a open baffle or a large, sealed box ("infinite baffle"). Would it be optimal? heck, no -- but it might sound ok, or even very good.
A vented enclosure is tricker, but, again, in the absence of any other information, one could guesstimate an enclosure tuning based on Fs and then tune by ear. If one uses a cardboard (or plastic) tube or pipe as a port, it's pretty easy to change the length and listen again. I'd opine that more "response anomaly harm" is done putting a driver in a too-small enclosure than a too-large one.
Well -- it's actually fairly straightforward to measure (estimate) Thiele-Small parameters with fairly simple tools (even simpler, given that nowadays a computer or probably even a cell phone can be one's "Signal Generator"):
http://sound.westhost.com/tsp.htm
Armed with T-S parameters, one may calculate a box and crossover with simple tools. As implied in another post above, build according to the models and you'll likely get something akin to the Toyota Camry of loudspeaker systems -- perfectly competent and unprepossessing, but doubtless lacking the spark of greatness.
That said, one upon a time the understanding of dynamic loudspeaker driver performance was more empirical/holistic than the Thiele-Small model (which, it should be borne in mind, is a model -- using a few simple parameters to model the complex frequency-dependent behavior of an electromagnetic motor wiggling around a diaphragm to make noise!). Indeed, in the old days, speaker cabinets were fairly generic, and tuning was done by ear -- or the "system builder" simply took what he/she got, and liked it!
Look at 1950s/1960s catalogs and you'll see that drivers and enclosures were often sold separately, and enclosures were meant to be generic, accommodating a broad range of typical drivers (woofers) available at the time. www.radioshackcatalogs.com www.alliedcatalogs.com and www.hifilit.com are all good sources for such "information".
Now, back to the OP's driver -- what is it, by the way?
In the absence of ANY other information about the speaker driver -- look at the woofer. Is the magnet big (heavy) or small? (Note, all bets are off with a neodymium or other 'rare earth' magnet; they're very strong magnets per unit mass)
If it is small, the Qts of the driver is probably fairly high, and could be accommodated on a open baffle or a large, sealed box ("infinite baffle"). Would it be optimal? heck, no -- but it might sound ok, or even very good.
A vented enclosure is tricker, but, again, in the absence of any other information, one could guesstimate an enclosure tuning based on Fs and then tune by ear. If one uses a cardboard (or plastic) tube or pipe as a port, it's pretty easy to change the length and listen again. I'd opine that more "response anomaly harm" is done putting a driver in a too-small enclosure than a too-large one.
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mhardy6647
Lunatic Member
If the OP is really content to "hit and hope", I'd probably "pretend" the Utah twincones (depending on which precise model they be) are EV LS-8s and use the nomograph in Tech Bulletin 10A to build a reasonable vented enclosure ;-)
http://www.electrovoice.com/downloadfile.php?i=970838
-- or, maybe mimic a Jensen (EDIT) "Duette" or Heathkit (EDIT) SS-1 vented box
http://www.tubebooks.org/file_downloads/Jensen_spkr_plans.pdf
http://www.heathkit-museum.com/hifi/hvmss-1.shtml
EDIT: actually, the more I think about it -- I'd "build" a JE Labs open baffle and start there with a darned good single-ended DHT amplifier. I suspect the drivers might be pretty beguiling so deployed
http://jelabsarch.blogspot.com/2012/06/open-baffle.html
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The drivers are realistic Americana 8" whizzer part #40-1187. Utah made them. http://www.radioshackcatalogs.com/catalogs/1967/ page 48. The frame splits into two separate sections. The frame will be open but the sides sealed . The height will be 38" to center of driver. Thanks.
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PR Audio
Super Member
TL's are not easy, but you don't always need the T/S Parameters if you have the Fs, which we know is 55 Hz. Then all you need is the Surface Area of the Cone (Sd) in Square Centimeters (cm2), that we don't know, but for our purposes we can approximate it. As we know, it is an 8" dia. driver (4" Radius). You can figure out a TL enclosure by using Sd or Radius (Bailey's) of the driver. You also need, as mentioned above, Fs, and the width you are planning your enclosure to be; remember that the line opening area needs to be equal or somewhat larger than your driver's Sd.
So, going the easy route, and using a calculator for TL and a calculator for Bailey's TL, we can figure out the size of our enclosure and length of TL, you still have to design how you will fold/route the TL as to keep the enclosure within a manageable size.
This might sound elemental to you, but just want to be sure you got it right...To calculate Sd you have to obtain your cone Radius; just measure cone Diameter from center to center of the cone surround, then divide by 2. Then it just a simple formula of Sd = 3.14 (pi) X Rad. So, if you have 8" (using the nominal dia.), your Rad is 4", and your Sd is 324.32 cm2. And, to keep a manageable width for the enclosure, let's say it has an Internal Width of 9.5" (24.13 cm).
Using our calculators, we have a TL with a length of 48-3/4" (classic), and a Bailey's TL with a length of 43-1/4". The TL calc will even give you a reference drawing with measurements, and the Bailey's TL will give you a generic drawing, but it will tell you the size of the "throat" opening.
I believe you have the driver parameters you need for a TL. Now, for the future, if you have the funds, any of these PE or MCM tools will be of help to you. Contrary to some suggestions, YOU DON'T HAVE TO GO OUT RUNNING LIKE A CHICKEN WITHOUT A HEAD AND BUY NEW DRIVERS FROM PE OR MCM OR MADISOUND.
MJ King, a regular AK member, has some very good info at Quarter-Wave, which you should read. There are other resources that I found useful, but doing the math I've found that the calcs are pretty good.
Keep us updated as to how your project progresses.
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gkimeng
Forum Mod, ClassicSpeakerPages.net
Amen to that. When I was a kid my dad and his contemporaries would prowl the shops on Radio Row and come home lugging cabinets bought empty and then used as rolling shopping baskets they filled with components. Some were the "latest and greatest," some were factory seconds that made their way from the electronics companies on LI to the job shoppers (you didn't think they actually threw their rejects away, did you?), and some were painted olive drab or desert tan and were clearly military surplus. From these they would cobble together all sorts of Frankenspeakers in our basements, trading their leftover parts back and forth as they went, then proudly hauling them up the stairs to show off at the neighborhood barbeques. Some of them actually sounded pretty good, while others were only listenable in the imaginations of their builders. I'll bet that even now some of those old cabinets are lurking in peoples' attics or basements, waiting to dragged out again for an estate sale.
mhardy6647
Lunatic Member
A - freaking - men to that!
meh. Science was/is my day job; this is a hobby (or me, and presumably for you, too)
PR Audio
Super Member
It is for me too, that's how it starts, then it grabs you, and you want to do other projects, next thing you know is that you are researching a lot. Calculators help a lot, and make life easier. I don't take too serious, that's why I advised you didn't TS Parameters, that would have been serious. Want to have some fun with those drivers? Cut a carton box or duck tape together a frw carton panels to an 18" W x 42" H rectangle size and do cheap Open Baffles, until you finish your TL's, or use 1/2" Thk Foam Core Board, it will be a great speaker. As a model, You can also do your TL enclosure using 1/2" Foam Core Board glued with wood glue or hot glue. I did a pair of desktop enclosures with FCB as to try them prior to building a wood enclosure, it's been 2 yrs and I haven't build the wood cabinets, as the FCB are working just fine...Enjoy!
Sent from my iPhone using Tapatalk
nexus
Super Member
Amen...
