Best woofer and tweeter for ATC SM75-150

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LouisPhil

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Joined 2023
#1
Hi.
First post here. Not so new to DIY but new in the forum.
Already partially discussed but that was some long time ago and may need an update. I have purchased a pair of SM75-150, willing to pair with a woofer and tweeter. I am targeting around 100l. Will be built with minidsp, active crossover to 3 amps. Purifi for the woofer and 2x Sabaj a30a for mid and tweeter.
Design is ported.
Similar to a SMC100 ATC, a clone.

My candidates for the woofer are:
- ATC SB75-314 I can purchase from a dealer in Canada (fs 21Hz, Qts 0.24 and Vas of 360l)
- Scan Speak 32w/8878t01 (fs 19Hz, Qts 0.33 and Vas of 234l)

The Scan Speak is a little bit more expensive but is better on paper and can go lower in a 100l box. The ATC seems to be the original design but some say not so deep. The Scanspeak seems to be a beast and very very good woofer. ATC is also excellent I suppose.
Any recommendation?

On the tweeter, candidates are (with more or less integrated waveguide):
  • T25CF001 Seas excel, same as previously used by ATC. Can get a pair used.
  • Scanspeak D2905/990000 Revelator. Doesn't seem to be widely used. I don't see a lot of reviews but one of the few scanspeaks with waveguide.
Other good candidates? Morel?

Crossover points will be 380Hz and around 3000/3800Hz. Some say the mid can go up to 3800Hz, others say maximum 3000Hz. ATC goes up to 3800Hz.

I am interested in your feedback, recommendations. Thank you ! Louis
 
#4
Hi, I have Volt RV3143 12" woofer in a 75l cabinet ( BR with 7.5 x13 cm port )and a separate "head "with ATC 75-150 16 ohm and SS 99000 Revelator tw.
Crossover is passive 380-3500 Hz The shallow waveguide of the revelator 99000 helps a little. Sounds good to me. Have fun with level adjusting!
 
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#5
 
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#6
Just going by weight which is mostly determined by the magnet size the ScanSpeak (7.5kg) is downright puny compared to the ATCs 12kg.

The ScanSpeak woofer weighs no more than an ATC 3" dome.

Personally if you can get the ATC for less than the ScanSpeak I would not hesitate and grab the ATCs asap.
 
#8
Both of your woofer candidates are very good. The ScanSpeak is for sure one of the best 12" drivers you can get. I don't know the ATC driver but they seem to be very good and probably can take more power and are more robust? But that's just a guess.
You could use 2 SB34NRXL in closed volumes - that's what I do and I'm very happy with the results.

You only need a T34 for very high levels (one 12" can't do that) or deep cross over frequencies. I use a T25B - for me a better driver as the Seas or rather old ScanSpeak. I also prefer to cross over lower as 3kHz with these tweeters - you can do your trials with an active crossover.

And MiniDSP ... you will have a hard time to get a better result with MiniDSP + power amps as with just a Hypex active plate amp. Hypex software needs a bit to get used to but sound is very good, esp with digital input.

Some measurements of the SB34NRXL: https://www.diyaudio.com/community/...rxl75-8-vs-sb29nrx75-6-vs-sb29nrx75-8.402671/
 
#10
That big ATC mid done needs a decent metal dome to compliment its primary acoustic signature, which can be on the colder side.

The best "all-round" tweeter for this mid is the Seas T35C002. Yes, its a soft dome but it sounds much more accurate than most larger domes I've heard. The T34b would be slightly warmer despite being a Be dome and it makes a big difference in the tonal balance. Both tweeters are very good, but the Seas has the better rear chamber design, easier to cross lower while not sounding as fatiguing in the lower mids.

For LF, my first choice (ported or sealed), I'd go with the SB34NRXL. 85 - 90 ltrs ported is a good size. You will however cut it close pushing the LF up to at least 350 hz so the mid dome (as gutsy as it is) doesn't run out of xmax down low. You won't get around a 3rd order network if you want to go passive.
 
#12
@Kwesi Those Grahams mainly use Volt drivers, but they were smart having chosen the large Seas domes. They also make Alnico motor versions of the T35. All incarnations of T35s sound great, although I wouldn't want to deal with the issues of remagnetizing Alnico when it gets weak.

I owned a pair of Dynaco A25 clones with this Seas tweeter. The first time hearing them actually startled me how clean and open the treble was, despite the large dome and lightly dampened motor design.
These drivers are sleepers. Even with just a simple cap and resistor as crossover, they go low, loud and stay pristine sounding, even at higher output levels without the slightest of change in character. Just to experiment, I tried an LCR notch at Fs, which did improve dynamics and top end a little but not by as much as I expected. Its just a very well engineered tweeter all around and the only larger soft dome tweeter I've heard which didn't need to be EQed flat on the top end (aside from the Audax TW034, but it didn't have close to the low level detail).

With the Jantzen WGs you can comfortably cross the T35Cs below 1.7k 12dB or 2.0 - 2.2k 6dB. Thats enough to let you exceed 105 dB average in room at an 8ft listening distance. The VC on this tweeter will easily take 15W continuous input.

The T34B is my next favorite. It doesn't have the even spread of overtones as a properly dampened soft dome, but makes up for it with better clarity and slightly lower HD, even at blistering levels, without a WG.

I wouldn't run the T34B without a WG period, as it hurts phase linearity around the HP. The T35C has a clever dampening chamber design which I believe retains the midrange purity at lower levels and doesn't get as congested in the upper treble as the T34B when the levels go up.

Mind you, this is splitting hairs with hand made $300+ drivers, but its nice to know the difference between these already low compromise designs. I wish they made a 35mm HF dome with the top end smoothness of Be and the natural sound of a higher end soft dome.
 
#13
Hi ! First, thank you so much for your feedbacks and recommendation. Very friendly to take the time to respond. Highly appreciated. Maybe a little bit more of context. I am trying to reach f3 at approx. 27Hz. I am now using the mid with a Dayton Audio reference RS270-4 and it is a interesting positive surprise. I am reusing a DIY cabinet so it was a good fit. It goes low for a 10" vented. Impressive for the price. I am a big fan of Tandberg monitor with a sealed 12" woofer.

Here a summary of the different options mentioned for tweeters:
  • T34 Bliesma, seems to be a very good tweeter but seems it would require waveguide. So maybe on the too expensive side and not optimized for this project.
  • T35 Seas seems to be maybe the best match. Expensive at around $300 per piece. I might find a used pair if patient.
  • SS 99000 Revelator, another good candidate. Cheaper but close in price to the Seas T35. T35 seems to be a better option if close in price
  • Seas T25CF001 - Still an option if going for cheaper unit. Could get now a used pair for approx $200.
  • Forgot to mention another option SS D2608/913000 with waveguide. The same person who sold me the ATC has a pair with specific waveguide for approx $200. Maybe the Seas T25CF001 at the same price used is a better option. Both with ferrofluid...

For the woofer:
  • Scan Speak 32W still on the list. Expensive but goes low and very good.
  • SB34NRXL seems the "cheaper" gem here. But doesn't go as low as the Scan Speak even if very close. Half the price of the SS. My go to option I think for now.
  • ATC woofer, heavier for sure than the SS but doesn't go as low (maybe I am too focused on going low...)

And now the new question 🙂 ! a 15" woofer sealed with DSP boost?
  • SB42?
  • Acoustic Elegance 15"?
  • ATC 15" The do seem to be used ported, not sure about using sealed.

The first two have xmax that could support going low with a DSP boost. Not sure about the Xmax of ATC drivers... Not trying to go extremely low but close to a f3 27Hz, lower than sealed without boost. With the advantages of the sealed more clear sound and punch. I am starting reading about sealed boost with DSP. Seems to be a good option.

Another question. Why would a fusion amp be better than minidsp + amps? I have seen they have a 3ways plate, Approx $1200 a pair. Yes, that is cheap for DSP + no need for a DAC + 6 power amps.
FA503 has 2x250W + 1x100W. Impressive. Only downside may be that you are stucked with "cold" class D amplifications for the mids and tweeters...

Hope it is interesting for you too to go through this. Against, thanks for your feedback and support.
 
#14
If you made a search on our forum, the expriement of ATC mid is almost done to death, the best way to utlitse atc accurate mid is to match its dome radiation , and freqency slope profile.

From our old memeber obi-wan reported that the best matching woofer is atc 15 inch woofer, so from my deduction the other promising woofer should be tad tl 160x series whcih have similar characteristic of atc,
Also about going low, there has been many build that going low does not mean good, say tl1603 for example, there were user who tuned to 28hz and 32hz in a cabinet of 170 liter, at the end of the day 32 hz is better becasue of the bass volume. even ATC itself 150 liter cabinet claim it only goes to 28hz @6db not the usual 3db. On top of my head, comercail speaker that had aiming low like 20-25hz were diatone v9000 or khorn and for last 20 years no one is aiming that low, so low tuning does not mean quality.

As for for the tweeter, you are looking for unit perform exceptional well above 3khz. Again follwing atc dome tweeter seems to fit best whcih will creat a prcise in your face image, some people like ribbon tweeter to add airiness .so the choice of tweeter depends on you

During my serach to clone tad2402 (TMS 2) in a french forum there were promising proven 3 way build using audax woofer /atc/ tweeter.
Another build from late Jeff bagby, shown in his paper about atc scm 75, he was contracted using using ae woofer, atc mid and raal tweeter.HE claim the build was successful.

Yuichi (one of MJ Audio technology writer) also played around dsp after his pesudo clone of TAD 2402 build but I am against digital dsp, except from electronic crossover, This well docuemnt in his book " デジタル時代のホーンスピーカー製作" https://www.amazon.co.jp/デジタル時代のホーンスピーカー製作-試作不要-シミュレーションで実特性を完全予測-新井-悠一/dp/4416115318

In my opinion the digital domain you need a lot of porgramming signal processing konwedge in the digial domain.For example on our current commercail DAC units, currently only bricasti and boulder are decoding them correctly and their trick was processing the digital information (sampling and filter) before feeding to analogy device DAC chip. Other brand did not made any similar process and was feed to their ESS or r2r chip creating more elctronic junks. Bricasti and boulder are leading the industry because their engineering background in signal processing.

If you are going for digital dsp we have commerical product such as lyndorf amp or kali speaker which have dsp taking into account of room accoustic which turn two speaker sound like three way. So my adivce just go build a good speaker, Once you are there you can start your dsp joruney or just go for biamp like the atc did
 
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#15
LouisPhil said:
Here a summary of the different options mentioned for tweeters:
Click to expand...
The best sounding tweeter I know and ever heared is not mentioned here - Bliesma T25B! It's also the best tweeter for wavegudies available (no front plate and invers surround -> best behaviour >10kHz) and there are proven wg designs avaiable.
When you cross over at 3kHz SPL level should be totally fine and it goes as loud as other top 1" tweeters.

I would only chose a bigger tweeter if you need supermaximum SPL (e.g. meet ATMOS level in 5m) or cross over significant lower! I cross the T25B at 2kHz with a Bliesma 3" and it takes that with no problem at all.

15" - I would always prefer 2x 12" over a 15". You can position 2x12" to distribute some SBIR and room reflections, can even build a 3,5 way etc. 2x 12" have more membrane surface as 15" etc.


Crossing the 3" at >3000Hz ... you will get uneven off axis behaviour. ATC seem to don't care ... so it depends if you want to improve or stick to the original.
And it's no difference if you use a big or standard tweeter - they all have wide radiation at 3kHz, it's just a matter of how strong they narrow radiation >10kHz.

Hypex - try to do some listening if you are unsure. The newest generation of Hypex doesn't sound cold - they don't sound. Combined with a beryllium tweter you have a feeling of "truth", you can trust what you are hearing is what is recorded.
Compared to a small tube amp which produces some nice "glamor" that's probably pretty different, but listen longer and compare, you will hear what is real and what is the fairy tale.

You are experienced with measurements and crossover design? Have at least a decent measurement mic to do the setup? DSP makes experimenting quicker but the same rules for speaker design are valid.
 
#16
IamJF said:
15" - I would always prefer 2x 12" over a 15". You can position 2x12" to distribute some SBIR and room reflections, can even build a 3,5 way etc. 2x 12" have more membrane surface as 15" etc.
Click to expand...
Agree. The SS 32W is an excellent driver, but it is expensive. Four of them will be $2900 USD. If budget is an issue, four of SB34NRXL is $1250 USD, and the performance is very close to the SS.
 
#20
Hi everyone! Thanks so much for your different inputs. I was able to score a nice used pair of acoustic elegance td15h. Following more or less the same choice as Jeff bagby mentioned above by sagitis. Seems to be a very good woofer with nice mid bass and much cheaper used than ss or 4x12 woofer. I plan to use it sealed applying linkwist transform and logically behind able to go low with the attributes of a sealed woofer. I will follow the recommendations to cross lower the mid.

I will most probably follow one of the recommendations for the tweeter, will be a little patient and hopefully be able to find a nice pair used.

Cabinet will be close to 70l following an optimized qtc for sealed.

Thanks again for all the information. I took time to review and analyse. Very interesting. Will keep you posted for the tweeter! 😀
 
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