Help with a possible ATC mid project?

[Virtalahde]

People,

for over a year I've been circulating around different ideas for the ideal speaker for my work. I am a mastering engineer, which means that I need something that is dynamic, transparent, honest - but still a pleasure to work with for extended hours.

So far I haven't heard anything commercially available that pleased me, so I see no other option that DIY. My equipment is DIY too, so it's a natural following.

I will not go into details why I have dumped all the previous ideas, but mostly it has been the usual problems with power handling and/or distortion, dispersion..

Slowly, I've came to the conclusion that I need to go with something that has a good, reputable history (especially in my profession), quaranteed support for years to come.. And thus the ATC mid came in to play.

I like the sound of dome mids - the bigger Questeds in our second studio use something that is probably the Vifa mid - and they do sound good, although a little lean in lower midrange right where the two Volt 8" woofer come into play.

I have a working history with Dynaudio & Morel tweeters, and I see no reason to break it. I think the Morel MDT33 will be perfect to complement the ATC mid - for crossover frequencies between 3k to 3,5k I could go for smaller domes, but I like the dynamics the Morels give and would actually prefer to have a slightly dark presentation from 10k to up since I have a working habit that sometimes makes me to do a tad too dark sounding records.

So we have the Morel MDT33 and the ATC SM75-150, quite possibly the S version.

It is going to be an all active speaker.

This is where I start getting to the point.

I think the cross-over between the dome mid and the woofer is going to be a problem. The Quested VS3208's (as discussed previously) sound lean to mid in the lower midrange, and the current set of two-way VS2108's I use sound way better to me in that department. Same 8" Volt woofer going to 1,25k.

ShinOBIWAN, amongst other in here, has said that the ATC mid is really picky when it comes to the woofer pairing, and I want to get this right from the beginning.

Oh, did I mention that the strict requirement from the beginning is: woofer in a acoustic suspension (sealed) cabinet?!

This is where it gets tricky.

I need a 12" or 15" woofer that is dynamic, low in distortion, relatively sensitive (although it goes hand in hand with bass response) , goes flat (-3dB) to around 50Hz AND pairs well with the ATC mid, so I need clean response around 400Hz and preferably no nasty things going below 1k or so.

The 15" ATC SB75-375SC seems to be a logical choice, filling the requirements, but does anyone else know of other options to consider? Possible falls using this ATC woofer?

From my previous brain-storming, I have a pair of 10" SS 25w8565-01's: I could use two of these per side, but I am just not so sure they can keep up with the ATC mid, and they start showing trouble around 250Hz, and at 600Hz they go worse. And I'd actually like to have just one big woofer since we're playing the midrange too.

Sorry for the too long a post, and please step in.

[Keruskerfuerst]

Planars (like from B+G) do sound very transparent.

Woofers from Isophon do sound very good and have a flat frequency response.

[el`Ol]

In order to retain the dispersion advantages of midrange domes compared to (larger) cone midranges I wouldn`t go beyond 10" when a typical 800Hz x-over is used.
Personally, I can`t understand the current comeback of dome midranges in the DIY scene. I heard the ATC at the Highend in Munich this year. Sounds very clean and detailed but lacking substance for my taste. I would rather think about the Accuton 44-8 for a concept with small upper mid driver, but you said you like dome midranges, so I`m not going to persuade you.

[Virtalahde]

Originally posted by el`Ol
In order to retain the dispersion advantages of midrange domes compared to (larger) cone midranges I wouldn`t go beyond 10" when a typical 800Hz x-over is used.

I am most likely going for 380Hz or so - this is what ATC uses and people have reported to sound the best, even if it seems insane spec-wise.

I would actually love to use a 12" driver instead of a 15" one, but I haven't really seen any paper cone drivers that would be a good match to the ATC midrange and go down to 50's in a SC.

I would rather think about the Accuton 44-8 for a concept with small upper mid driver, but you said you like dome midranges, so I`m not going to persuade you.

Well, the use these speakers are going to get is a bit different. I need to have a good, clean insight to the music, but they also need to engage me to do the right decicions and help me to work for long hours. Transparency (whatever that means) is actually not as important as translation - whatever I do on the speakers NEED to sound good pretty much everywhere. They're a tool.

This is why mastering engineers in general stick to few well-known brands.. B&W 800 series, PMC's, ATC's, Dunlavys & Duntechs..

What I would build for home listening? Something that has tons of colour, good bass, exciting sound.. Maybe I'd just buy a pair of old , big JBL's.

[el`Ol]

The 12" Eton comes into my mind (the one used by Avalon). Sensitivity would match.
http://www.eton-gmbh.de
By the way, what do you think about Geithain monitors? They have a good reputation in Germany.
http://www.me-geithain.de
Manger also build an active monitor.
http://www.manger-msw.de

[tinitus]

Fostex makes very nice 12" with low Fs

But maybe you should get a pair of active ATC

http://www.atc.gb.net/domestic/scm150slat.html

[Ap]

As you want a sealed alignment for the bass.
I would choose a woofer with Qts of at least .4 - not sure how much volume you have to play with, but I would offer up Aurum Cantus as a candidate. They appear to be extremely well made for the price, the AC-250MkII is a carbon fibre sandwhich on foam core, If you remember the (highly regarded) Kef B139 useda foam core, and from what Ive heard carbon fibre sounds great for bass.
Well worth checking out....
http://www.partsexpress.com/pe/showd...number=296-434

[Virtalahde]

Originally posted by el`Ol
The 12" Eton comes into my mind (the one used by Avalon).

Not bad at all. Checking it out.. Datasheet suggests higher 3rd order distortion (than 2nd order) right above 250hz, but who knows.

Originally posted by tinitus
maybe you should get a pair of active ATC

This is where cash come into play. I don't have $20,000 to spend on a pair of speakers..

Originally posted by Ap
not sure how much volume you have to play with, but I would offer up Aurum Cantus as a candidate.

Now this is an interesting one, definately worth checking out I think. Thanks!

The volume is not a factor. 150 litres to 200 litres is perfectly OK.

[ralphs99]

Hi Virtalahde,

I've tried the ATC mid with three different woofers, the 10" Volt B250.8, 12" JBL 252, 15" JBL 2235. Of the three I like the match to the Volt the best. I agree that matching a woofer to the ATC mid is tricky. The ATC does sound best crossed low (I'm currently using 340Hz). This then requires a steep filter to avoid stressing the small diapragm too much. However I'm not using the system at extreme SPL's so pushing the lower boundry isn't a problem for me. Hence the sound of the upper range of the woofer needs to be a good match due to the abrupt change to another driver. I feel that a smaller diameter woofer minimises the audibility of the crossover point. I understand your desire for a response down lower than a small woofer in a sealed box allows. For me the solution was to add subs. This offers the additional benefit of managing room modes through careful placement of the subs.

I'm always mindful of drawing too many conclusions when evaluating monitors. Often low mids are influenced by room modes, and often a perceived deficiency in one part of the spectrum is caused by an emphahsis somewhere else.

The ATC's need a lot of EQ to get them sounding their best. I guess it's no coincidence that most speaker manufacturers using the ATC mid are active. So your decision to do the same is sound. This also offers the possibility of EQing the woofers to extract the best from them. So a slightly thin sounding woofer can be corrected to get the sound you expect. The character of the woofer sound is most important. To this end I feel a smaller paper coned woofer is your best bet to match the ATC mids. Then adding subs to get the really low bass.

As an aside, I've been most pleased crossing the ATC mid at around 2.5-3kHz to a dome tweeter rather than the 3.8kHz that ATC uses in their monitors.

I've documented tests of the ATC SM75-150S and Volt B250.8 here: http://www.aeronet.com.au/projects.htm

Cheers, Ralph

[Virtalahde]

Ralph,

thank you! Excellent information in your site. I was prepared to the fact that the SM75 needs equalization.

Originally posted by ralphs99
Hence the sound of the upper range of the woofer needs to be a good match due to the abrupt change to another driver. I feel that a smaller diameter woofer minimises the audibility of the crossover point. I understand your desire for a response down lower than a small woofer in a sealed box allows.

This is exactly the thing that worries me, too. Going from 3" dome mid to 15" woofer is indeed a pretty big step.

To tell you the truth, I have thought of another bass alignment - the transmission line. Can't say I have any experience with them, but some have said them to have similar sonic quality to a sealed box, they just go lower. I've heard some critizing, too - but must be because of different designs. There must be good BR designs out there I could enjoy. Dunno.

http://www.aos-lautsprecher.de/engli...dio100tlE.html

The AOS Studio100TL uses a custom 6ohm ATC woofer, which doesn't seem to be too much apart from ATC SB75-234 woofer. It'd be pretty interesting to build the Studio100 cabinets and use the custom woofer and see how it'd work with the dome midrange.

I need to do some researching about power handling of TL alignments.. I know I'm driving myself for an overkill in maximum SPL since I'm working in medium sized rooms. But in a sealed cabinet, most single 10-inchers don't just seem too happy around 50Hz in cone excursion if cranked up.

Originally posted by ralphs99
I'm always mindful of drawing too many conclusions when evaluating monitors. Often low mids are influenced by room modes, and often a perceived deficiency in one part of the spectrum is caused by an emphahsis somewhere else.

If you were pointing at my comments on the Quested VS3208's, the room definately has its signature - that room simply isn't as good as my room. But somehow I also suspect the Vifa dome mid Quested uses isn't up to the par around the cross-over point, which is (IIRC) 450Hz.

Originally posted by ralphs99
As an aside, I've been most pleased crossing the ATC mid at around 2.5-3kHz to a dome tweeter rather than the 3.8kHz that ATC uses in their monitors.

I thought about this too. In my previous ideas for the workhorse speakers, I was crossing the tweeter pretty low, 1,5kHz-2kHz. I bet the Morel would be a nice sonic match to the SM75 mid around 2,5Khz-3kHz.