Studio Monitor Project - In Need of Advice - diyAudio
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Multi-Way Conventional loudspeakers with crossovers

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Old 12th August 2008, 02:31 AM   #1
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Default Studio Monitor Project - In Need of Advice

Good day to you all,

I am in the brain-storming stage of a project. My goal is to build a modest set of near-field studio monitors. Though I have a background in electronics and some experience in acoustics, I would really appreciate to hear the opinions and suggestions of the regulars here – from which it would seem I have much to learn of loudspeakers.

Here is what I have managed to decide upon so far (though my decisions are often fluid to the detriment of confidence!): The design will be 2-way, and likely sealed for improved transient response. Final Q would be on the order of 0.60 or perhaps lower, as maximum power handling is not as much an issue (though growing enclosure size is a concern, but an acceptable casualty). I would like to use a larger diameter mid-bass, of either 6.5 or 8 inches. I find larger diameters such as this seem to suffer less from ‘beaming’ in the midrange, and tend to sound more natural with subtle textures such as voice. But perhaps this is a preconception from which I suffer. I will likely stick with either treated paper or polypropylene for the mid-bass cone material, as this will simplify cross-over design in the hopes of minimizing cross-over phase distortions. For the tweeter I would like to use a dome, possibly with a wide angle wave guide, or perhaps not. Either way I would prefer a textile dome to a metallic type. I should mention that I need an F3 of 65 Hz or lower if possible, at which point a subwoofer will take over.

I have not yet decided on an HF driver, though it will probably be something from Morel. However, after a lot of consideration (and really a lot of getting nowhere) I have some interest in a Vifa mid-bass, namely the P21WO-20. Of most interest to me is the 91 dB sensitivity, and extension beyond 4 KHz. The impedance curve looks nice enough as well. The FR graph shows some step anomalies, which seem to occur at regular intervals indicating a resonance and subsequent harmonics, but I suppose no driver is perfect.

Anyway, all my babbling brings me to my main questions at this point in the project (certainly there will be more if you are up for it!): What do you think of the P21WO-20 as a mid-bass for such an application, and what design suggestions might you have? Cross over points for example – this mid-bass has a wide bandwidth, but should I make use of that and cross-over at a high point to the tweeter? I would think the higher you crossover to the tweeter the more the two drivers will ‘appear’ separated to the ear, and this is a near field application.

Thank you in advance for anything you might have to contribute!

J.Freeman
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Old 12th August 2008, 03:51 AM   #2
Jay_WJ is offline Jay_WJ  United States
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If you're looking for the best possible passive 2-way studio monitor in a sealed enclosure with good enough bass extension, look no further than the following variation of Zaph's ZRT 2-way.

Build Zaph's ZRT 2-way in a sealed .5 to .75 cu ft enclosure with his reduced baffle step compensation option: L10 = 2.0 mH and R8 = 5 or 6 ohms. No problem obtaining an F3 of 65 Hz. You won't be able to find a lower distortion, compact 2-way design than this, which also satisfies your other condition (sealed F3 of 65 Hz or lower).

-jAy
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Old 12th August 2008, 07:35 AM   #3
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Or you could buy a studiomonitor

Passive>
http://www.sweetwater.com/store/detail/ANF10/

powered>
http://www.sweetwater.com/store/detail/A7/

cheap>
http://www.sweetwater.com/store/detail/Rubicon5a/
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Old 12th August 2008, 09:04 PM   #4
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Thank you Jay,

Zaph's ZRT looks interesting. The Revelator series of drivers are very nice looking, that's for sure. However they might be a bit out of my price range. Certainly worth a second look, however. I will check it out more tonight.

Nur, thank you for the links to commercial monitors. The ANF10 caught my eye. However this is a DIY forum, is it not? I'm hoping that I will be able to build something nicer than I could buy for the same money, if that makes sense. Plus it's just fun

So thank you for those thoughts guys. But would anyone have comments regarding the P21WO-20, or related suggestions etc?

Thanks,

Jim
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Old 12th August 2008, 09:04 PM   #5
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Can I say however again? :P I must be tired.
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Old 13th August 2008, 12:10 AM   #6
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Gotta love those Vifa P-drivers! Anyway, looking at the off-axis response, I am reminded of Wayne J's article on choosing the right crossover point.

http://www.speakerbuilder.net/web_fi...xpointmain.htm

You'll notice that the on-axis response goes WAY out there, and remains flat (again, those wonderful P-cones!). But the off-axis response drops off after 2K. Hence, I would choose an XO point around (or below) 2K.

This limits your choice of tweeters, but there are still definitely some goodies at a reasonable price that can cross between 1.6-2 KHz: Vifa D27, Vifa PL27, Vifa D25AG, Peerless HDS, Seas 27 T__C series, Dayton RS28a, or if you want to jump up in price, then there's the Scan Speak 9500 (9700 also might work, but that's even MORE money. Still, that absence of ferrofluid can make a really magical sound)

As far as proven designs go, I'd highly recommend Dennis Murphy's MBOW1 2-way project. The woofer he used on there isn't exactly known for deep bass, but it does everything else well; and it sounds like you're not worried about anything below 65 Hz. And that tweeter, gah!

Now that I'm thinking of it, since you plan on sealing these speakers and using them with a sub, you might want to consider a different, smaller midwoofer. That way, you can cross higher, and have a larger choice of tweeters.
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Old 13th August 2008, 12:25 AM   #7
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I've had recommended to me a combination of the Hi-Vi RT1-II planar pseudo-ribbon tweeter, Dayton RS52 dome midrange, and Hi-Vi D6.8 or Usher 8955 - both of these will go down to 40hz, but the Usher might do it a bit better and with more headroom. 4khz and 700hz crossover points with a DCX2496 active crossover and tri-amplification will give you a frequency response within 1dB of flat and stellar off-axis response.

If you do want to build a 2-way, the D6.8 is a very good choice as well. It has less high-frequency distortion and beaming than most 8" drivers, but is capable of playing down to 40hz in a ported enclosure. A notable use is the Cliffhanger Audio Bulldogs - I own a pair, and despite their rather small single woofer they produce the sort of bass I'd associate with a sub.

Alternately, if you do want to build an 8" 2-way, a low crossover point is a must. The Seas 27TDFC/G is a very good and reasonably priced soft-dome tweeter that can be used as low as 1.6khz with a 4th-order crossover.

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Old 13th August 2008, 10:37 AM   #8
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You could always build this :

diyAudio reference speaker project


Sounds good , not too expensive..

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Old 13th August 2008, 10:11 PM   #9
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Hi Undefinition,

Thank you for your detailed response! I just finished reading the article you provided - very interesting. I didn't know that off-axis response was a consideration when chosing a crossover point. Interesting stuff - I'm learning already!

Hmm, I see what you mean about the roll-off around 2 KHz. Your suggestion of a smaller diameter driver may be the ticket. I would like to try the P21 - it seems like such an elegant driver. But the P17 is nice to, maybe I should give that a look. Not a fan of Morel? I must say I have little experience with tweeters, and my first Morel experience was a reasonable one, so perhaps I am falling back on old habbits. With that in mind, I will check out some of the HF drivers you mentioned. Armed with my new crossover vs resonance knowledge!

***

Spasticteapot, thank you also for your feedback. I have been looking at Hi Vi items now and then, but I'm a little afraid of them as I haven't heard much. How do they stack up in terms of quality and tested numbers vs advertised? The D6.8 looks nice, but there is one thing that concerns me most with this style of driver (such as with the Dynaudio's) - those little windows around the dust cap - what happens when this driver is placed in a sealed enclosure? If those vents lead into the voice coil gap, would they not leak air through the pores in the spider? I wouldn't imagine this would have much of an effect but it must be something of an issue.

I will check out the Seas tweeter you mentioned, and maybe give the D6.8 another look. It is mean looking, not that that should sway my interest (but between us it does )

***

Andrew01 that is a nice looking project! I must admit I do like the look of a smaller driver with a 4" flange tweeter. Very pro looking. Nice and clean, and as a monitor space would not be an issue with such a box. But, I'm not sure about the low end response. Maybe if I give up on my sealed idea, I could go with a smaller driver like that, but that would constitute a paradigm shift in my design ideas. Such as they are!

***

Thanks for the help guys, I will do a little more research and then perhaps unload some more of my semi-noobie questions :P

Jim
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Old 13th August 2008, 10:37 PM   #10
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Quote:
Originally posted by J.R.Freeman

Spasticteapot, thank you also for your feedback. I have been looking at Hi Vi items now and then, but I'm a little afraid of them as I haven't heard much. How do they stack up in terms of quality and tested numbers vs advertised? The D6.8 looks nice, but there is one thing that concerns me most with this style of driver (such as with the Dynaudio's) - those little windows around the dust cap - what happens when this driver is placed in a sealed enclosure? If those vents lead into the voice coil gap, would they not leak air through the pores in the spider? I wouldn't imagine this would have much of an effect but it must be something of an issue.

I will check out the Seas tweeter you mentioned, and maybe give the D6.8 another look. It is mean looking, not that that should sway my interest (but between us it does )
The D6.8 is a surprisingly good driver - although it is much cheaper than its nearly identical counterparts from Morel and Dynaudio, it has much less harmonic distortion. Hi-Vi is relatively new to the audio scene, but their drivers have a strong reputation for quality.

Your worry about the vents is unfounded, as they only allow air to move under the dustcap and around the pole piece, which is separated from the cabinet by the woofer's spider. It's a bit like giving a speaker a phase plug in that it keeps air from being compressed under the dustcap and allows greater cooling of the voice coil.

While distortion and energy storage are both a little higher than many similarly priced drivers, there is a trade-off: Bass. The D6.8 will give you a F3 of 65hz even in a very small sealed box.

Of course, there are many other excellent tweeters, including the Dayton RS150. Although you would need a larger, ported box for the same F3, it would give you slightly less distortion - at half the price!

The Seas 27TBFC/G is a top-notch tweeter. I haven't used it, but Undefinition (who is honestly much better at this than I am) has: it's found in his Aether design, which won the under-$250 category at a recent DIY event.

Andy G. also has a rather interesting design that might appeal to you.

http://members.optusnet.com.au/~grad...GOS/Stacks.htm
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