Help required on 2 way book shelf for a total Noob - diyAudio
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Old 19th March 2012, 02:30 PM   #1
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Location: Kerala , India
Default Help required on 2 way book shelf for a total Noob

Hi,
Since i couldn't find any speaker kits in my place and importing drivers form abroad costs a huge sum (transportation + customs duty which some times go more than the cost of Kits ) i am thinking of making a Bookshelf with locally available drivers . i am a total noob to speaker building i hope speaker building Gurus will help me in the process .

these are the two drivers i am offered

Tweeter --- Peerless India T25 AN ( around 18USD)
https://picasaweb.google.com/1046008...45/19March2012


Mid/Woofer ---Peerless India M13NH (around 15USD)
Products - PeerlessAudio.com

i used an online calculator and got these values for the box
internal volume : 7.07 lit
Fb 52.67
port lenght 2.24inch
port dia 1 inch

are these ok ?

and what type of a crossover should i go for ?
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Old 20th March 2012, 12:48 AM   #3
MCPete is offline MCPete  United States
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The peerless M13NH certainly is more suitable in a vented rather than a closed box. That is,

EBP = Fs/ Qes = 45.5 Hz/ 0.41 = 111

An EBP or efficiency bandwidth product close to 100 means more suitable in a vented system.

That said, a vented system is more difficult to make work properly than a closed-box system. This is the case because the Q of the system of woofer in the box is difficult to predict. In the Loudspeaker Design Cookbook it is suggested to make the box 25% larger than what the equations say interior volume should be according to the alignment that you choose. Then you can make the box smaller by filling it to get the correct alignment, if necessary.

If you truly are a beginner, a closed-box system is a lot easier than vented.

For the crossover, I do believe that there is a tutorial available here at DIY-Audio for designing them without making measurements, which I suppose is what you would want.

Regards, Pete
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Old 20th March 2012, 01:34 AM   #4
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by MCPete View Post
Then you can make the box smaller by filling
it to get the correct alignment, if necessary.

Regards, Pete
Hi,

Unless you've monumentally screwed up reducing box volumes
to hit a "target" is a very bad idea / concept. Simple port retuning
is all that is needed to get the best out of a better bigger box.

The driver will have very restricted bass in a closed box.

rgds, sreten.
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Old 20th March 2012, 01:46 AM   #5
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I'd go slightly larger, ~ 10L tuned in the high 40s. But this depends on how accurate the given parameters are, ideally you'd break the drivers in for a while in test boxes, then measure the parameters yourself using Arta or some similar software & recalculate.

The tweeter link doesn't work, so can't recommend a xover freq, but looks like the woofer will be good up to ~2-3 Khz, & will need some sort of notch to deal with the peakiness. 2nd order Linkwitz-Riley is probably a good place to start for the xover.
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Old 20th March 2012, 03:06 AM   #6
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Thanks for the suggestions , here are the tweeter parameters
Click the image to open in full size.
T25AN1 by Madhu_kannan, on Flickr
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Old 20th March 2012, 03:07 AM   #7
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Click the image to open in full size.
T25AN2 by Madhu_kannan, on Flickr
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Old 20th March 2012, 03:52 AM   #8
MCPete is offline MCPete  United States
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Quote:
Originally Posted by sreten View Post
Hi,

The driver will have very restricted bass in a closed box.

rgds, sreten.
If the OP were to go along with the idea of tackling an easier build, that is, closed box, then I gave him the means for selecting a different woofer that would be more appropriate in a closed-box.

Regards, Pete
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Old 20th March 2012, 04:05 AM   #9
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Another noob question what if i go wrong with the calculations and if the volume becomes larger than actually needed hows its going to affect the sound quality ?
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Old 20th March 2012, 04:13 AM   #10
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Peerless seem to recommend using this as a midrange, 200 and up, so a sealed box and no bass seem inevitable with only one driver.
Vented box is your only real option as a 3-way is more difficult to get right; especially first time, nice specs for a decent midrange tho
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