Diy Monitors - to build or not to build PART II

[mhelin]

The Proteus is based to the Wilson Audio CUB speaker:
http://www.wilsonaudio.com/products/cub/index.html

I think Tony just happened to have some drivers available which he used to make a similar one. Anyway, the point with this design is the great sensitivity you get with the drivers used. Tony used now obsolete CB17RCY/P's with 91 dB sensitivity. All new Seas 7" drivers CA18RNX etc. drivers have the sensitivity of 88 dB or less so they won't directly replace CB17. With active crossovers and biamping you can still use the less sensitive drivers; CA18RNX or L18RNX/P (with phase plug) could be used here with a success I guess. Regarding the in-wall mounting you just don't have to do anything with the baffle-step compensation. In passive crossover like used on Proteus it's a little bit more complicated. In an active speaker you just set the crossover point and tweeter vs. woofer levels. Can't go wrong easily.

If you want to use similar tweeter as in WA CUB you can still have a Focal (now gone) style inverted dome tweeter made by Celeritas here:
http://www.clofis.nl/nl/celeritas/celeritas_overig.htm


ps. This direct image link from page 1 sometimes freezes this thread:
http://img450.imageshack.us/img450/7527/SOFFITframesnewtannoypos.jpg

 

[Moby]

The Proteus is based to the Wilson Audio CUB speaker:
http://www.wilsonaudio.com/products/cub/index.html

I think Tony just happened to have some drivers available which he used to make a similar one

Yes, they look very similar, except Tony used Seas Excel T25-001 tweeter, 25mm fabric dome and Wilson tweeter is 25mm Inverted Titanium Dome. I think that can be absolute different kind of character :? Also mid-bass is The Seas CB17RCY/P paper cone, and Wilson looks like some Polly^%&*^%& :wink:
Personally, I would be happier with some Scan speak drivers inside. Tony is honest about drivers, and he comments that " They are not as good as the Scanspeak".

ps. This direct image link from page 1 sometimes freezes this thread:

I resized the pic, hope now will work better. :thumb:
BTW, I'm waiting for Tony's response, and hope we will have some nice news about project. Also, will be nice to hear more comments about :grin:

 

[Moby]

At last, here's some progress after few mails from Tony. In the meantime I contacted Thomas Barefoot, but he kindly explain that he is some big business with growing his company, so I wish him all the best and hope to hear some high-end news from barefoot-sound :thumb:
Anyway, I ended with Tony on the scan-speak drivers, MTM configuration, helped with Peerless sub-woofers. All boxes are sealed, mid section 2x 18W8545K-00 in the 15L for each driver and two separate sealed sub in the 80L, (XXLS-308-8+8 - Peerless 12" (830847). The double voice-coils should be wired in series on each driver (making a 16ohm driver), then both drivers wired parallel. The acceleration factor is much greater if this is done) per side. All units will be feeded active, crossed for tweeter SS D2905/970000 around 2200hz and sub will wait to measure baffle response... but around 90hz. I still wait to hear comments from Tony about my preliminary drawings , and here they are free to comment by you guys :green:

And yes, I was thinking about bad sides of time alignment like diffraction, so I'm not sure what to do? Physical misalignment between M and T is around 3cm, so that will be around 90us :roll: Some electronics line delay will be nice, but I'm not sure where to look about. Maybe Tweeter waveguide horn with 3cm depth can help, but also I'm not sure how to calculate that Any help about will be nice :thumb:

 

[mhelin]

Look for Monacor WG-300 waveguide. It's quite a large though (169 mm dia, 32 mm deep, see http://www.monacor.com/de/produktseite_suche.php?artid=5785&spr=DE&typ=full ). www.ts-audio.de at least lists them.

Also you could use pieces of felt around the tweeter for the configuration like in your first picture. See this page:
http://www.speakerdesign.net/felt_amelioration/feltssdescr.html
http://www.speakerdesign.net/felt/felt_ring_vs_blocks.html

 

[Moby]

WG-300 looks interesting. Of course, nobody knows what will do to the tweeter response, but maybe is worth of trying. With some modification to fit into 11cm tweeter area... :thumb:
Felt is option of course, but looks very ugly
I think that most elegant way will be to go with flat baffle, but with some active time compensation. So, all-pass delay circuit with 90us is option too. But I can't find schematics... :roll:

 

[kvintus]

If you go for a non-flat baffle, make sure that there are no sharp edges anywhere or else the edge-diffractions could ruin an otherwise good speaker design.

But I'm sure you knew that already.

/Anders

 

[Gerald Jansen]

[quote author="Moby"]WG-300 looks interesting. Of course, nobody knows what will do to the tweeter response, but maybe is worth of trying. With some modification to fit into 11cm tweeter area... :thumb:
Felt is option of course, but looks very ugly
I think that most elegant way will be to go with flat baffle, but with some active time compensation. So, all-pass delay circuit with 90us is option too. But I can't find schematics... :roll:[/quote]

Hi Moby,

Please have a look at the complete site of Sigfrid Linkwitz: http://www.linkwitzlab.com
The particular all-pass delay is shown in: http://www.linkwitzlab.com/images/graphics/allpass.gif
Somewhere on the website he mentions that 2 sections in series may be needed to provide enough delay.

Cheers,

Gerald

 

[mhelin]

[quote author="Moby"]WG-300 looks interesting. Of course, nobody knows what will do to the tweeter response, but maybe is worth of trying. With some modification to fit into 11cm tweeter area... :thumb:
Felt is option of course, but looks very ugly
I think that most elegant way will be to go with flat baffle, but with some active time compensation. So, all-pass delay circuit with 90us is option too. But I can't find schematics... :roll:[/quote]

Allpass:
http://www.linkwitzlab.com/filters.htm#4

The WG-300 looks similar to MCM wg tested here:
http://www.zaphaudio.com/hornconversion.html

 

[Moby]

Thanks guys, seems that unknown waveguide can do a lot of bad things without proper compensation.
Thanks for link about electronic compensation.
Anyway, I will continue to work on the project and let you know about.
Will be nice to hear some more thinking about waveguide from some "horn experts" ( I'm not) :wink:

 

[jsn]

It seems like a lot of effort is being made to align the tweeter with the woofer. Why not use a fullrange driver or something similar? That will certainly give you the best possible alignment.

I am currently building a pair of "monitors" (not sure what that means exactly) that use a Fostex fx120 for everything above ~400Hz and an 8" woofer usable in a nice small sealed box for everything below 400Hz. The crossover will just be a coil on the woofer since the fullrange naturally drops off under 400Hz or so.

These aluminum dustcap Fostex speakers are great. The fx and ff series. They are great for nearfield.

I am waiting for the big brown truck to deliver the woofers, but I'll post the results here.

jsn

 

[mhelin]

The point with the waveguides is that you get couple of dB more efficiency and can use lower crossover point that without it. Also a waveguide does make the directivity match the one with the woofer at lower crossover point, without it you have to use higher crossover frequency. With MCM and Monacor (~17 cm) waveguides you can use about 1.2-1.5 kHz crossover frequencies (with 4th order filter). These wg's are shallow exponential waveguides whereas the PE waveguides Krutke tested were much deeper with a little bit "horn effect" in the upper frequencies. If you are not using a wg you must cross over at about 2.5 kHz. With 6.5" driver that's a little bit high frequency as the 'mechanical crossover' thing (cone breakup) has already started working there (the whole cone is not radiating pistonic anymore). With good cone materials and surrounds it's not a big problem though (some coloration is unavoidable). Anyway, the allpass delay may have some problems (related to phase), so something like Behringer DCX2496 might be a better solution for delaying the tweeter signal, it will also make the design easier as it's very easy to change the crossover.

 

[Moby]

Efficiency is not so important in active crossover design, but time align can be. Ok, lover cross point will be nice, so that point me to the WG.
Yes, DSP crossover is nice solution but I never heard any good sounding product fro Beringher, maybe DCX2496 is exception. ( what I suspect).
There is more expensive products what can work much better, but they are over 1k euro.
So, some nice wood-crafted WG can solve much money. And looks cool :wink:
I don't think that calculating 3 cm WG is big problem, but for me as mathematic dumb is challenge. I'm sure that Lab is full of that kind of experts

 

[Gerald Jansen]

[quote author="Moby"]I don't think that calculating 3 cm WG is big problem, but for me as mathematic dumb is challenge. I'm sure that Lab is full of that kind of experts [/quote]
Hi Moby

There's this thread "New Wave Guide Study" over at htguide.com you might wanna read:
http://www.htguide.com/forum/showthread.php4?t=18242

Cheers,

Gerald

 

[Moby]

Thanks Gerald :wink:
Nice reading. Now I see that there is a few more guy looking for "WG formula". Unfortunately I didn't find any usable info except thinking about.
BTW, Genelec 1031 have crossover at 2.2k what is something like mine, so I'm thinking about measuring and maybe cloning that. What you think about? I have 1030, 8030, 1031, 1037 and 1038 genelec's ready to measure. Maybe that can help?

 

[Gerald Jansen]

At Htguide there are some real knowledgable people assembled on the study/ apllication of (DIY) loudspeaker technologie.

I would use Genelecs only as inspiration (eg fot WG use), but would't try to clone them. To me they sound liveless, possibly caused by the internal electronics. I know that the 1037B even has some sort of vactrol limiter build inside to protect the system/drivers. Which saved my ass once when a DAW went Awohl and threw out loud noise...

 

[mhelin]

Yes, Genelec waveguides are moderate and don't have the problems assicoated to the waveguides which try to maximize the efficiency and use high compression ratio which makes the air non-linear ( http://www.4sptech.com/version2/problems.html ). Also the Genelec WG termination is smooth. I think the 8030 waveguide might be fine, though it's only got 5" MW. Genelec WG is not very large though, it helps just a little bit to match the radiation patterns of the tweeter and the midwoofer and get a little bit more efficiency at crossover point. Also it helps with the time-alignment but actually not enough (it seems not to be a problem though, even less if you mount the high enough so that woofer is closer to youre ear than the tweeter).

However, I don't think that the form of the waveguide itself is important. It's can be just a straight line from the throat to mouth if it doesn't make the WG too deep and thus the compression rate too high. The mouth termination however should be very smooth so that the acoustic impedance when the air leaves the WG is low enough not to cause the diffraction ( http://www.4sptech.com/version2/diffraction.html ).

Btw. This is a very nice monitor:

http://www.4sptech.com/version2/timepiece2_features.html

Single 8" alu woofer (propably Seas) crossed over @750 Hz / LR4 to 1" textile dome in something like 10" waveguide. Sensitivity is "only" 85 dB, not much, but it goes from 30 Hz to 20 000 Hz flat. It hybrid ported / transmission line speaker ( http://www.4sptech.com/version2/timepiece2_specifications.html ).

 

[mhelin]

Almost forgot this source for Genelec-like (round and shallow) waveguides:
http://www.hifitalo.fi/shop/sivut/aw4.htm (sorry for the finnish content)
You can see also that the box in this kit uses combined transimission line + ported design.

This kit uses a 12 cm waveguide (picture of it is here:
http://www.audioavid.com/wbb2/attachment.php?attachmentid=1270 )
There's also a 14 cm waveguide. I guess you can order them from:
[email protected]

The 12 cm one is designed for 3/4 inch Seas and the 14 cm one for 1" Seas tweeters.

 

[Moby]

I would use Genelecs only as inspiration (eg fot WG use), but would't try to clone them. To me they sound liveless, possibly caused by the internal electronics. I know that the 1037B even has some sort of vactrol limiter build inside to protect the system/drivers. Which saved my ass once when a DAW went Awohl and threw out loud noise...

Gerald, I don't want to clone genelec monitor, just thae WG. :wink: I agree STK4036 inside is not challenge :grin:
Personally I don't have so great experience with genelec's at all , but WG is maybe the best part of the design.

 

[Moby]

[quote author="jsn"]It seems like a lot of effort is being made to align the tweeter with the woofer. Why not use a fullrange driver or something similar? That will certainly give you the best possible alignment.

I am currently building a pair of "monitors" (not sure what that means exactly) that use a Fostex fx120 for everything above ~400Hz and an 8" woofer usable in a nice small sealed box for everything below 400Hz. The crossover will just be a coil on the woofer since the fullrange naturally drops off under 400Hz or so.

These aluminum dustcap Fostex speakers are great. The fx and ff series. They are great for nearfield.

I am waiting for the big brown truck to deliver the woofers, but I'll post the results here.

jsn[/quote]

And yes, I almost forget to remember you to check Barefoot's comment from first page of topics (red letters) :wink

 

[Gerald Jansen]

[quote author="Moby"]

Gerald, I don't want to clone genelec monitor, just thae WG. :wink: I agree STK4036 inside is not challenge :grin:
Personally I don't have so great experience with genelec's at all , but WG is maybe the best part of the design.

Moby, sorry for my shorthand writing and thereby almost "accusing" you of cloning Genelecs. :? Good luck with your project :thumb: