I am also interested but I cannot say now the probability of me carrying the
idea through. If you go off-list perhaps you could cc me the emails? I
don't know anything about speaker design but is "best for ham radio" not
sufficiently specific. Perhaps, "best reproduction of human voice at
conversational volume levels." Does that differ from "understanding weak
signals w/a lot of noise"? Of course I haven't mentioned CW.
It is a project I am interested in. The issue may be project time available
and money.
On Thu, Feb 4, 2010 at 3:04 PM, Jim Barber <audio...@charter.net> wrote:
> Hi Joe,
>
> Since there haven't been many people interested I'll respond to that one
> here then we should probably move this offline if you decide to continue.
>
> The next step would be coming up with the best compromise of cabinet size,
> output SPL, (loudness) bass response and driver size/cost for your
> requirements. That can be a bit daunting or not based on your overall
> experience, but I can help fill in the blanks if you fill in others. Once
> you arrive at the right "blend" of parameters for your design you'll
> dimension it, get out the saws and screwdrivers and build it. Building small
> speakers in itself is simple, designing them to specification takes a little
> work.
>
> If the design process asks too many questions, we can also convert this
> into a "small, medium, large" kind of project, which would be much more
> straightforward, but reduce the opportunity to learn about the process
> itself. If so, you can safely ignore everything below this paragraph and
> just pick one of the three.
>
> ------------------- DESIGNING THE SPEAKER --------------------
> Cabinet size:
> Along with driver selection, cabinet size (and porting, which comes later)
> *generally* determines how low the freq response can go. If you're not sure
> just come up with a rough set of dimensions that would work well for your
> shack and we can take a look.
>
> Output SPL: (loudness measured @ 1 meter)
> Very modest 85-90db
> Average to loud 90-100db
> Rock the room over 100db
>
> Bass response:
> This parameter has the most impact on cabinet size, driver selection and
> overall cost. In general, a -3db response anywhere below 100hz will cause
> the overall cabinet size and driver size/cost to climb rapidly. That isn't
> necessarily a bad thing, but if you want flat response down to 40hz at 100db
> SPL your design will end up several times larger than placing that -3db
> point at 100hz. 150hz hits the "high value" spot on the curve, but higher
> than that generally doesn't gain much.
>
> Driver size/cost:
> Excluding highly specialized units, drivers run from 3" to 8" and cost
> roughly $12 to $185 each. As I mentioned before, I happen to like Tang Band
> drivers for high-value, relatively small full-range speaker designs.
> Limiting the range to $25 - $55 US will yield any number of truly excellent
> designs. You can use any brand or driver you want, of course, but I can only
> help model those that have published Thiele-Small parameter data ("TS
> parameters") available.
> ...
>
> References/sources:
> Selected Tang Band drivers: (this URL may be too long to work, sorry)
>
> http://www.parts-express.com/wizards/searchResults.cfm?searchFilter=&srchExt=MFG&perPage=27&sortBy=3&layout=GRID&page=1&srchPrice=&srchCat=576&srchMfg=276&srchPromo=&srchAttr=
>
> General drivers, mounting hardware, stuffing, port tubes etc
> http://www.parts-express.com
> http://www.madisound.com
>
> Free design software:
> WinISD http://www.linearteam.dk/
> FRD Consortium http://www.pvconsultants.com/audio/frdgroup.htm
> Many others! - Google "speaker design software"
>
> Disclaimer:
> Yes, I do DSP and audio design for a living, but my interest here is simply
> raising awareness of the benefits of quality audio in amateur radio
> equipment and operation. I will not benefit from this financially, but in
> turn I ask that any designs or models I generate assisting hobbyists not end
> up in commercial products.
>
> 73,
> Jim, N7CXI
>
>
> Joe Camilli wrote:
>
>> I would be interested in a project of this type. What would be the next
>> steps?
>> Joe N7QPP
>>
>> On Tue, Feb 2, 2010 at 3:02 PM, Jim Barber <audio...@charter.net <mailto:
>> audio...@charter.net>> wrote:
>>
>> Seems like a perfect, low-impact DIY opportunity to me.
>>
>> Tang Band (for example) makes a number of excellent full-range
>> drivers that work well in small, ported cabinets. For those in the
>> US, a trip to Home Depot for a quarter sheet of MDF, (Medium
>> Density Fiberboard, listed by them as a "hobby panel") perhaps some
>> rubber feet and a few inches of Schedule 40 PVC for a port tube
>> could yield a better quality speaker than you can easily buy on the
>> open market, regardless of price.
>>
>> If there's (A) a way of reaching consensus on desired size,
>> appearance and driver characteristics and (B) a few people actually
>> get interested enough to build one, I'd certainly donate a working
>> acoustic design. (and/or provide links to freeware design software
>> for those that want to learn for themselves)
>>
>> There's still a suitable power amp to deal with, but there are any
>> number of suitable (kit or assembled) amp modules available as well.
>>
>> 73,
>> Jim, N7CXI
>>
> [snip, for sanity's sake]
>
>
>
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