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Old 5th October 2012, 01:48 AM   #1
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Default How to choose a speaker?

Well guys, I was trying to find some good drivers under 100$, so far I've found those 2 drivers to be quite interesting

Speaker Building Supplies from Madisound

Speaker Building Supplies from Madisound

IMHO the first one looks like a better driver... But as I know that parameters are not everything in this world of so many speakers (even tough both of them have a low qts and FS, good xmax and high sensitivity but unfortunately they also have a very large VAS value.)

The thing is, is there a way to know if a driver is as good as it seems to be by the parameters? What should I consider while choosing a driver for a 2way bookshelf?

Thanks in advance for the answers.
Cya!
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Old 5th October 2012, 03:17 AM   #2
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the parameters are similar for these two drivers, the main difference is in their cone material, so you'd probably decide based on personal preference, which tweeter, & crossover freq & slope. If you can find any distortion tests that may be helpful too.
I'd probably go for the paper ('papyrus') cone, stiffer than poly, so slightly lower distortion, the trade off is that it won't be quite as smooth higher up, but that would be outside the passband if crossed over ~2-3kHz
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Old 5th October 2012, 02:41 PM   #3
tvrgeek is offline tvrgeek  United States
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The SB's look like very good value. I intent do try one myself soon. For a little more, I am most pleased with the SEAS 18rnx-h1456-7 The HDS and the Usher are also quite well respected. There is an Eaton with tempting specs, but the reviews I have read snuggest it is not as good as it looks. I have not been a fan of poly, but I need to revisit it as they composites they use are better than when I first tried them. OTOH, my Kef Q1's, mica filled poly, I though were not very clean.

How do you know? Well, that's a the $64,000 question now isn't it? The not so helpful answer is "experience". Pete makes some very good general points. I might add, If the motor has a copper shunt in it, that makes a difference. I find most metal cones just too hard to deal with the breakup, but my RS150's worked out pretty well. Look at the response to see where the breakup is, and if it is far enough away from your crossover, depending on slope, that it can be tamed by a notch. Many breakup as low as 5K, which makes them very hard to deal with. You might also go read the comments on the driver tests over at ZAPH, and then look at the spec sheets for the ones he tested to get some general ideas.

The only correct answer is, you know after you spend your money and see how hard the driver is to integrate with the tweeter you pick. The SB ring-radiator tweeter looks to be a tempting pair with either of the ones you mentioned. It looks easy to use as it behaves very low where something like an XT25 does not.
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Old 5th October 2012, 10:44 PM   #4
system7 is offline system7  United Kingdom
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SB Acoustics make some interesting bass/mid drivers. Characterised by vented magnets, copper polepieces and low inductance. Also high mechanical Q. Joachim Gerhard, who knows a thing or two, is doing some design work for complete SB systems at the moment. SB Acoustics Satori Monitor

I rather like the look of the smooth sounding polycone with a 5kHz notch as suggested. But if the livelier sound of a papyrus/paper cone appeals to you, look no further than the SB Acoustics published Eka kit:
SB Acoustics :: Eka

Looks like a doddle!
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Old 5th October 2012, 11:30 PM   #5
mikje is offline mikje  United States
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Have you thought about going with a proven design? There are thousands of speaker designs available that have been designed by folks with a lot of knowledge. I've built several and love them all. What are you looking for in the speakers you plan to build? Music, movies? And what are you looking for as far as budget for the completed project?
Mike
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Old 6th October 2012, 12:44 AM   #6
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When people discuss the 'sound' that different cone materials posses I think that this is largely down to how different cones go through break-up. Cross over before any severe break-up occurs and the sonic signature that that cone might impart is going to be reduced.

The stiffer the cone and the lower its self damping properties are the worse the break-up will be. Manufactures seem to be moving further in the direction of making slightly stiffer variations of paper and poly that remain break-up free to slightly higher frequencies, but when they break-up they do so more severely.

Is this a good design choice to make? It really depends on if the break-up imparts its presence into the harmonic distortion and then to the skills of the designer working with said driver.

The paper SB driver is a classic example of a stiffer paper cone this brings on an associated region of break-up that is fairly severe. One other aspect of this driver is that it shows a mild resonance at around 1.5kHz. Both the main break-up and this little bobble at 1.5kHz affect the harmonic distortion to a degree.

In Zaph's measurments these are clearly visible.

Click the image to open in full size.

We can see the hiccough in the second order products (green trace) at 1.5kHz and we can also see the break-up imposed in the third order (third) products as the uneven response above around 1.5kHz. Now these issues aren't going to be a problem in any which way, so the fact they are there is almost academic, but it is worth noting that they exist.

Now the poly cone appears to share the exact same motor of the paper version so it is going to have very similar harmonic distortion numbers, but as the poly cone appears to lack the resonance at 1.5k and has a less severe break-up it is going to have less impact on the distortion profile.

Even if you are crossing low, it is worth baring in mind that the break-up of the poly cone is going to be a lot easier to control then the break-up of the paper cone. Pick whichever you are more comfortable with. I am personally more interested in the poly cone because it would appear to have the same excellent motor of the paper driver, but doesn't share it's particularly ugly break-up. It will be easier to work with and more then likely require a simpler crossover to get the job done and this will end up costing less. Both drivers if used correctly will sound excellent though. The paper driver does have one small benefit though of being slightly more sensitive mind you and that shouldn't be ignored.
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Old 6th October 2012, 12:53 AM   #7
tvrgeek is offline tvrgeek  United States
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You know, you can't get to the SB kit pages from their menu. Sloppy.
Funny, I spent all day today picking my next build. Decided to do a 29RDC / 17NRX with a second order in a sealed box to target as an AVR-based (80 Hz) set.
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Old 6th October 2012, 01:45 AM   #8
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The tweeter I'm going to use is this one http://www.akronaudiotec.com.br/kbt25.pdf
It's a very good tweeter, The crossover will be a 2nd order Linkwitz-Riley at 2,5khz
But the truth is, I don't know the difference between exactly the same speaker but with different cone materials.
The bookshelf will be mostyl used to listen to music but sometimes gaming and movies. I'll read everything again that you guys posted and make some research.
Thank you all for answering me. Also if you could try to explain what's the difference between the many materials used in cones, what them sound like, I'd be very thankfull.
Cya.
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Old 6th October 2012, 02:57 AM   #9
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Another question, should I consider the on axis curve while calculating the crossover value or the others?
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Old 6th October 2012, 05:27 AM   #10
balerit is offline balerit  South Africa
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Your two speakers must have the same sensitivity so that means you should use the SB17NRXC35-8. The impedance at the crossover point will determine your crossover values.

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