An idea for studio monitoring

[Consul]

I'm slowly wading through the mass of information out there on how to design speakers, and how to account for what features. I still have a long way to go, but I think I'm getting somewhere.

I started investigating full-range speaker possibilities. This can go everywhere from small Aura speakers at $10 apiece, all the way up to these things called Mangers, which cost $1200 apiece. Fortunately, there's a range of option in-between.

Rather than getting into the details, though, I wanted to discuss some ideas I had. In my quest to avoid putting a crossover in the critical 200hz to 2khz range, I started looking at full-range drivers as an option to cover the mids and highs, while handling the lows with a woofer, using an active crossover plus biamping. I ran this by some folks on the DIYAudio speaker building boards, and they think I may be onto something.

Since I know there are a few speaker builders around here (ahem**KEV**ahem :green: ), I thought I'd run this by a few of you. I'm still thinking about what drivers to actually try (the Visaton B200 modified with phase plugs keeps coming up on that other board, but I'm not so sure at the moment), but I'll keep looking. I don't have to buy just yet.

One of the issues that keeps coming up that I still get confused on is on-axis vs off-axis linearity and distortion. I understand the basic idea, but I still don't know how to read all of those fancy graphs to divine the necessary information.

 

[mhelin]

Do you have read these threads already:

Diy Monitors - to build or not to build:
http://www.groupdiy.com/index.php?topic=5837&highlight=studio+monitors

Diy Monitors - to build or not to build PART II:
http://www.groupdiy.com/index.php?topic=12511&highlight=studio+monitors

In my quest to avoid putting a crossover in the critical 200hz to 2khz range,

What makes that range more critical than 20 Hz -20 000 Hz or anything else?

I started looking at full-range drivers as an option to cover the mids and highs,

Wide-range ("full-range") drivers are very poor as tweeters. Actually they are poor at all frequencies. However, if you like their sound they can give you somewhat "musical" sound at less than moderate levels. Also some wide-ranges (about 3" - 4" like the CSS drivers) make nice nearfields for tracking vocals or as PC-speakers.

 

[pstamler]

The things that make almost-full-range-but-not-bass drivers so difficult to design and use...well, there are several, but two biggies are response at high frequencies and off-axis response.

Simply put, it's not easy to make a speaker with enough moving surface to produce decent SPL levels down around 200Hz that will also produce response out beyond about 8kHz or so. 8kHz has a wavelength of about 1.7 inches in air, somewhat more in solid materials (IIRC). Up around there, you start to get cone or dome breakup modes, which produce peaks in the response, then rolloff, plus some distortion as well.

Off axis is also an issue; the driver gets more and more beamy as frequency increases, so the off-axis response is typically seriously rolled-off compared to on-axis. It'll also have different funny peaks and dips due to cone/dome breakup.

It's doable -- just -- but with significant compromises, particularly in the top octave. The good examples are bloody expensive.

Peace,
Paul

 

[mikep]

have you looked into planar transducers? Some people have sucessfully made DIY electrostatic planar speakers. If it is big enough you can get true full-range sound out (ie, real bass). do a google search.

mike

 

[Svart]

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-712

?

500hz-20k

 

[Svart]

I'm interested in this as well. I would love to use something that didn't crossover right in the middle of the midrange. My 2 way monitors cause me to mix my midrange strangely.

But I want to use bigger woofers, 8 or 10 inches. these 6 inches just don't give me the low end I need to hear.

maybe:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-368

?

 

[mhelin]

Better build 3-way, use these drivers crossed at 700 Hz and 3.5 kHz:
Tweeter:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-555
Midrange:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-550
Bass:
http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=297-447&DID=7

Basically like Jon Marsh's project for Hi-Vi M8a + Vifa ringradiator @htguide.com forums ( http://pwp.t-3.cc/ttriff/M8aArticle/ ) but with a separate midrange driver. Crossover doesn't have to be that steep though. Like ATCSCM50 ( http://www.lasvegasproaudio.com/scm50asl.html ).

 

[NewYorkDave]

EV SP-12 :grin:

 

[Svart]

Not to hijack the thread and not to go against the great suggestions of others but the extended freq range tweeter interests me. I have some computer speakers, monsoon something-or-others, with planar mid/tweet with a sub and they sound wonderful in the high and mids. I would love to investigate a purpose built studio monitor with this technology.

I might just try to build my idea of the planar tweet and the paper cone woofer to see how it actually sounds... When I get some money of course.. :green:

 

[Svart]

any problems with crossing over around 800hz between the planar driver and the woofer?

 

[Consul]

Nice to see I started a discussion! :grin:

I'm seriously considering re-starting the old idea of a DIY reference speaker, except I'm not qualified to design it. I do know I have some criteria:

1) Designed specifically for soffit-mounting
2) No cross-over in the critical mid-range (which I'll put at 200-2000hz, although some folks designate it differently)
3) Active crossover with one amp per driver (bi-amping, tri-amping)

I'm curious to see where we end up. Those planar tweeters look like they have possibilities.

 

[Consul]

Oops, almost forgot one:

4) Usable in a small room.

That's the most limiting criteria of all, actually.

 

[Consul]

That Neo8 planar is showing response down to 200hz or show, and 220 is one of the recommended crossover points. I wonder how well it could actually take that.

500hz fails my second criterion, but done with an active crossover and a good woofer, it would probably still work pretty good.

I'm looking at an 8-incher, rather than a 10-inch, though. Small room and all that. http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-366

I'm with PRR on this. I can look at graphs until I turn blue in the face and not learn anything about actually getting something to work.

 

[pstamler]

200 - 2k is probably going to work nicely as a midrange, but 2k is a little low for most tweeters to cross over at. Maybe 2.5k, and make the crossover steep to keep lower frequencies out of the tweeter (their extra excursion will add distortion.) Check out some of the classic papers by Siegfried Linkwitz on designing active crossovers which correct for driver response anomalies.

Peace,
Paul

 

[Guest]

I love this:

 

[Viitalahde]

[quote author="pstamler"]200 - 2k is probably going to work nicely as a midrange, but 2k is a little low for most tweeters to cross over at.[/quote]

These days I'm working with Quested VS-2108s and the tweeter crosses at 1,25kHz LR4. :shock: It's a Morel tweeter. Not a hint of distortion and the upper midrange/lower treble area I previously had problems with (Dynaudio BM6A) is working for me now. Already thinking of a DIY solution though. I have a sound in my head I need.

 

[mhelin]

[quote author="pstamler"]200 - 2k is probably going to work nicely as a midrange, but 2k is a little low for most tweeters to cross over at. Maybe 2.5k, and make the crossover steep to keep lower frequencies out of the tweeter (their extra excursion will add distortion.) Check out some of the classic papers by Siegfried Linkwitz on designing active crossovers which correct for driver response anomalies.

Peace,
Paul[/quote]

Linkwitz uses crossovers at 120 Hz and 1440 Hz (both LR4 24 dB/oct) for his Orion dipoles. Obviously the distortion will be problem with cheap drivers. Rule of thumb is to cross at least one octave above the resonance frequency of the tweeter. However, main factor for selecting the crossover frequencies is the off-axis frequency response.

200 Hz - 2kHz is a reasonable area though but you must use rigid metal cone drivers which don't have those midrange break-up modes. At 200 Hz there's plenty of energy so you'll need at least 6.5" driver. Seas has a driver with excellent motor, the L18RNX/P (H1224),
http://www.seas.no/Prestige%20Basser%20PDF/L18RNX_P-H1224-08.pdf

Matching tweeters are 27TBC/G (H1147), it's ferrofluided version H1212 27TBFC/G or the soft cone 27TDFC (H1189). These drivers have low Fs below 600 Hz and are quite inexpensive.

Below 200 Hz use Peerless SLS or XLS series drivers.

Here's a passive 2-way using the Seas drivers mentioned above: http://www.humblehomemadehifi.com/DD8-MkII.html

Get the Behringer DCX2496 digital xover and it will be easy to set up an active system.

Edit: Now that Jaakko mentioned Morel this might be nice kit for people who need more bass but want good midrange and high frequencies too:

http://www.partsexpress.com/projectshowcase/angelf1/angelf1.htm

 

[mikep]

[quote author="Viitalahde"]
These days I'm working with Quested VS-2108s and the tweeter crosses at 1,25kHz LR4. :shock: It's a Morel tweeter.[/quote]

yeah, isn't it a sweet tweeter? I worked with a pair of H108's for a couple of months. That is one of morel's cheaper units too. though I think quested takes it apart and adds some damping behind the dome (so Ive been told, might be BS). Ive been wanting to hear the supreme 110. If I was going to build monotors it would be 2X 18cm Audio Technology + supreme 100 in a sealed MTM. recessed tweeter surrounded by felt (similar to dunlavy SC-I) w/ 1st order line-level passive x-over and a hypex 180 for each driver. oh, and a pair of 12" servo subs.

anyone ever do a DIY servo subwoofer?

 

[Viitalahde]

[quote author="mikep"]yeah, isn't it a sweet tweeter?[/quote]

It sure is, I love it.

The Vifa XT25 is great too. I have my eye on these:

http://www.aos-lautsprecher.de/english/studio24E.htm

(the XL version at the bottom of the page). These things should be awesome, the tweeter is expensive and improved version of the XT25. My dream speaker is a pair of these crossed to a sealed woofer system somewhere below 250Hz - maybe even ~100Hz if the Scan-Speak woofers integrate..

 

[usekgb]

The Vifa XT25 is a wonderful tweeter, but I think I like the sound of the Vifa DX25 more. It just sounded smoother to me. Also, the BG planer tweeters do a great job. The biggest draw-back to them is their off-axis response. This is the case with any flat planer tweet. They beam badly if you don't have some sort of waveguide on them. Even with the waveguide, they are pretty beamy.

In my opinion, for small room nearfield monitoring, it will be tough to beat a good old small two way monitor. I know you are trying to get the x-over out of the 200 to 2k range, but this may be pretty tough for practical 2-way nearfields. Not many 8 inch woofers perform cleanly up to 3k, and if you find one, you may get some beaming from them as the wavelength of the higher frequencies starts to get smaller than the diameter of the woofer. This causes poor off-axis response. The wavelength of a 3k tone is about 4.5 inches long. This is close to half the size of an 8 inch woofer. This means that the dispersion of the woofer at these frequencies will not be very good. The maximum frequency you should try to operate an eight inch woofer at should be 1674 Hz. (Correct me if I'm wrong here).

Cheers,
Zach