The sh34-76 Tweeter

ATC & other manufacturers design parameters, technical queries etc
Posts: 16
Joined: Tue Dec 20, 2011 8:33 pm
Location: North Devon, UK

The sh34-76 Tweeter

Postby mademe2 » Mon Oct 24, 2016 5:30 pm

Dear All,

I seem to have a set of these sh34-76 tweeters, however I can not find anything out about them?

Anyone know anything about them, or have a spec sheet?

Thanks for your help.

Mademe2

User avatar
Posts: 195
Joined: Sun Aug 30, 2015 9:47 pm
Location: UK

Re: The sh34-76 Tweeter

Postby studioman » Mon Oct 24, 2016 5:43 pm

I have them too. Mine were in some PA65's, now converted to SCM150ASLT's.
What are yours fitted into?

Here's some info for you anyway:

Image

Image

Image
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

Posts: 16
Joined: Tue Dec 20, 2011 8:33 pm
Location: North Devon, UK

Re: The sh34-76 Tweeter

Postby mademe2 » Mon Oct 24, 2016 6:25 pm

Hi,

Same as you!

So the question is are they still in production? Do they use them today in the SCM200 and 300s? Any idea how they stack up against the New S Tweeter?

I can find much about them at all, anywhere!

Mademe2

User avatar
Posts: 195
Joined: Sun Aug 30, 2015 9:47 pm
Location: UK

Re: The sh34-76 Tweeter

Postby studioman » Wed Oct 26, 2016 8:40 pm

I know that the PA65s can be ordered still.

ATC's website shows the 200 and 300 series as having the 25mm tweeters now, whereas until recently they had the SH34-76....

But when I talked to ATC about the performance of my SCM150ASLT Anniversary conversion recently, I was told that the 34mm tweeter should do them proud and would be almost as good as the 25mm tweeter.

I am sure that the S Spec SH25-76S would be a further improvement but I am very happy with the delicacy of the sound of my ATCs already.....especially when supported by the Townshend Maximum tweeters. Here are my girls on holiday this week, in the back streets of Naples....

I remember the back streets of Naples, two children begging in rags, both touched with a burning ambition, to shake off their lowly-borne tags (as PA65s)....oh yes they do, haha haha.....

Image






(just a bit of fun on Photoshop.....) :-)
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

User avatar
Posts: 195
Joined: Sun Aug 30, 2015 9:47 pm
Location: UK

Re: The sh34-76 Tweeter

Postby studioman » Tue Nov 01, 2016 9:48 pm

This might be helpful to anyone interested in the SH34-76.

I was asked a question about why I had added a super tweeter into my redesign of a PA65 into SCM150ASLT style cabinets.

The reason is the SH34-76 tweeters that were in the PA65s.

This is my reasoning, in its entirety, I have copied it from a post in the thread entitled PA65 in the HiFi area of ATCForums.

Here we go......




"Thanks for that!

Yeah....this might be difficult but I'll try to explain my though process....

It's like this....electrical current, synapses and ganglions, blah blah blah.....ending up with 'I think, therefore I AM a loudspeaker designer.' :lol:

OK....serious now...get tech. Here goes....

Firstly, I already had my Townshend supertweeters. I had bought them used, but in perfect condition. I used them in my Office system on top of some old Rega Xels. At first there was very little coming from them and I couldn't understand why. Then I tried the tightness of some of the external casing screws and found they were loose. I assumed therfore that the internal ones might be loose too. I dismantled them and found LOADS of play in everything. Once I had tightened everything up, they worked a treat. Lovely metallic sheen to cymbals, etc.....you could REALLY hear the breathing clearly on some close-miked voices, etc....
I also have a pair of wonderful old Celef RT-1 speakers with ATC bass units, KEF B200 used in an open backed format as a midrange, and with unbelievable Decca Ribbon Tweeters. So you can see that I am quite enamoured with a ribbon here and there. Including on thighs, but that's another story. :oops:

When I bought my PA65s, for a short while before I dismantled them for the parts, I tried the PA65s without and with the supertweeters. And they did make a small but noticeable and worthwhile difference.
I was lucky that my PA65s were in good condition, driver and amp wise, and they had been serviced and updated regularly by ATC. The drive units all had stickers on showing the dates that they had been installed, replaced, modded etc. The same went for the AmpPack.

The tweeters, I was overjoyed to find, were the new (in 2011) 'ATC made' SH34-76 models. So they were very worthwhile having.
However, if you check the spec of some of the current range of 'larger' ATC speakers, like the SCM150 ASLT, you will find the following:

SCM150SE: (with 25mm SH25-76S), Freq Response +/- 2dB is 60Hz to 17kHz, Freq Response +/- 6dB is from 25Hz to 25kHz
SCM150ASLT: (with 25mm SH25-76), Freq Response +/- 2dB is 60Hz to 17kHz, Freq Response +/- 6dB is from 25Hz to 22kHz
PA65: (with original SEAS or VIFA tweeter) Freq Response +/- 2dB is 60Hz to 12kHz, Freq Response +/- 6dB is from 25Hz to 22kHz
The difference between the original PA65's high frequency response and that of the Studio designs is largely down to the difference in the choice of tweeter. But in the case of the PA65 which was designed for nightclub use (ie high volume & high quality), the reduced range of linearity in the frequency response curve was not a major issue. In fact it was the efficiency of the tweeter that was more important in that application. Otherwise folk would believing nightclubs not only pissed and naked, but also with tinnitus.

HOWEVER.... mine had been re-fitted with the SH34-76 model tweeters in 2011. Lucky, eh? Larger domes such as a 34mm dome are known to not 'go' as high as smaller (25mm or 19mm) domes. But these were efficient and had to be reliable in a nightclub. You couldn't have tweeter domes falling out all over the place. They proved to be both efficient AND reliable, as well as having great clarity. So they were perfect for nightclub use.

When I had my amp-packs re-capped, I asked ATC's advice about setting up the levels on the amp-pack (using the internal trimmers), and was told it would be best to set up the bass for a 150 litre cabinet instead of a 65 litre one, and to set the mid and treble levels to match the bass output. So the levels were going to be ok, but the frequency response would fall a little short as the 34mm tweeter only goes up to 18kHz compared to the SH25-76 which goes to 22kHz and the SH25-76S which reaches the dizzying heights of 25kHz.

So my supertweeter is positioned to supplement the SH34-76 where its response starts to fall off, and bring the overall response closer to that of the studio models that my design aspires to be.

I asked for and received advice about this from Max Townshend and from two of the ATC staff, which gave me the confidence to proceed.

I hope that all sounds sensible!"
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

Posts: 16
Joined: Tue Dec 20, 2011 8:33 pm
Location: North Devon, UK

Fuses SR Black!!!

Postby mademe2 » Fri Mar 03, 2017 12:53 pm

Morning,

Over the last year we have exchanged comments over building a set of PA65s into Tower 150s. Both of us with pleasing results. (Love them).
I have been using them for around a year or so and enjoying the music not the HI FI. A few months ago a friend of mine who is all into his tweaking and valve amps and so on loaned me a set of SR Black fuses and said 'try them in your speakers'. Why not? He just left them with me and i did nothing with them for a month! So i put them in and (now I don't believe I am going to say this and have no idea how it works, impedance i guess??) But the difference is rather large!!!!!!!!. Cleaner, deeper cleaner base, great imaging and just real music. Its like you can hear into the music. Great!!

Bad bit is they are ridiculously expensive (£99) but are better than any cable change i have made at whatever price and better than most bits of equipment change (new CD, bla bla bla). Now before you tell me I am mad am a HI FI nut that has been sucked into the marketing and all that, have a try of them and let me know what you find. I think they are available on money back if you don't like them kind of deals so nothing to lose.

As i said. i can't believe i am writing this but it is just what is have heard.

Let me know your findings!

User avatar
Posts: 195
Joined: Sun Aug 30, 2015 9:47 pm
Location: UK

Re: Fuses SR Black!!!

Postby studioman » Fri Mar 03, 2017 9:52 pm

mademe2 wrote:Morning,
Over the last year we have exchanged comments over building a set of PA65s into Tower 150s. Both of us with pleasing results. (Love them).
I have been using them for around a year or so and enjoying the music not the HI FI. A few months ago a friend of mine who is all into his tweaking and valve amps and so on loaned me a set of SR Black fuses and said 'try them in your speakers'. Why not? He just left them with me and i did nothing with them for a month! So i put them in and (now I don't believe I am going to say this and have no idea how it works, impedance i guess??) But the difference is rather large!!!!!!!!. Cleaner, deeper cleaner base, great imaging and just real music. Its like you can hear into the music. Great!!
Bad bit is they are ridiculously expensive (£99) but are better than any cable change i have made at whatever price and better than most bits of equipment change (new CD, bla bla bla). Now before you tell me I am mad am a HI FI nut that has been sucked into the marketing and all that, have a try of them and let me know what you find. I think they are available on money back if you don't like them kind of deals so nothing to lose.
As i said. i can't believe i am writing this but it is just what is have heard.
Let me know your findings!



I am constantly tweaking my equipment, and yes I agree that changing fuses DID make a difference.
Matt very kindly gave me a pair of high quality fuses, and they made a big difference.
Very much as you describe, cleaner and more powerful bass and better detail throughout the frequency range.
My internal wiring, cabinet damping, rewiring of the coaxial cable in the amp packs all helped too.

However, I think the biggest change was about 2 months after I had first torqued up all the bolts holding the drivers to the baffles, and the baffles to the cabinet.
I could not believe how loose they had become. I mean almost finger tight. That's loose. Check yours out!
So the biggest change was due to me retightening all the bolts up again! Everything improved when these bolts were tightened.
The loosest ones were the bolts around the perimeter of the baffle.

There must be at least 5 factors at play here...
1. The threaded inserts gradually pulling into the rear of the MDF. by slowly crushing it under torque.
2. The MDF actually shrinking thickness-wise with our central heating. Probably significantly.
3. The speaker gaskets slowly crushing. Probably a slow, moderate change.
4. The countersunk bolt washers slowly 'relaxing' into position. Probably slight.
5. The bolts actually expanding slightly due to the difference in temperature between the garage where I made my speaker cabinets, and the temperature in our home. Take me seriously on this. It was COLD in my garage when I built my cabs...probably varying throughout the day from freezing to 8 degrees Celsius. Our home is around 20 degrees. This will mean that due to the co-efficient of expansion over a temperature differential of 10-15 degrees, the bolts will be slightly longer when at room temperature, i.e. they will be looser in a warm room! Maybe not a lot, but it WILL happen.
Last edited by studioman on Sat Mar 04, 2017 10:33 am, edited 1 time in total.
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

User avatar
Posts: 6485
Joined: Tue Feb 23, 2010 5:46 pm
Location: Ireland

Re: The sh34-76 Tweeter

Postby MattSPL » Sat Mar 04, 2017 2:02 am

Yes the fuses and mains cable debate can be a painful experience which I tend not to get into these days, but I agree, these Ac fuses are a revelation in the Hifi world for me. It's like they act as filters on the mains. I don't know how to explain it.

I plan to try a mains regenerator at some point, this will give a precise 230v perfect sine wave and also provide a ups system. I intend to use this just for my Dac and sources.
Sony BDP-S790 > Matrix Quattro Dac > Digidesign RM2's with SB Acoustics drivers > DIY Dayton Audio UM18-22 Sub

Posts: 16
Joined: Tue Dec 20, 2011 8:33 pm
Location: North Devon, UK

Re: The sh34-76 Tweeter

Postby mademe2 » Sat Mar 04, 2017 1:38 pm

Chaps,

So this morning I looked at the bolts holding the drive units in. As you said they all needed a few turns! Many thanks!

Next I replaced the co ax with some 'Van Den Hul D - 102 III HYBRID' which i had in my box and yes a good step up. Again thanks for this.

What did you do on the speaker cable front? What cable did you use, which did you try and which worked out the best IYO? Did you use the block connector or come off the pins on the board? Any thoughts would be interesting. Doing the speaker leads is a bigger job so I only really want to do it once.

Try those SR Black fuses at some point there good.

Mademe2

User avatar
Posts: 195
Joined: Sun Aug 30, 2015 9:47 pm
Location: UK

Re: The sh34-76 Tweeter

Postby studioman » Sat Mar 04, 2017 10:18 pm

mademe2 wrote:Chaps,

So this morning I looked at the bolts holding the drive units in. As you said they all needed a few turns! Many thanks!

Next I replaced the co ax with some 'Van Den Hul D - 102 III HYBRID' which i had in my box and yes a good step up. Again thanks for this.

What did you do on the speaker cable front? What cable did you use, which did you try and which worked out the best IYO? Did you use the block connector or come off the pins on the board? Any thoughts would be interesting. Doing the speaker leads is a bigger job so I only really want to do it once.

Try those SR Black fuses at some point there good.

Mademe2




Crikey you work fast!

Glad I could help!

I'm sure your VDH is a very similar upgrade to my Apogee cable...
Image

I also put some Poron vibration insulating foam around the two power caps that were closest to the coax cables, and carefully cable tied the cables so they were not going to vibrate against the caps.

Regarding speaker cable....I had some Abbey Road Reference speaker cables (now branded Studio Connections) and decided to use these. Biggest problem was that the multi-connector will only take relatively small diameter cable. I got hold of some of the correct ITT Cannon connector shells and pins from RS Components, and then to my surprise, whilst staring at the circuit board of one of the AmpPacks one day, I noticed that there were 6 ¼" male spade terminals soldered into the circuit marked Bass+, Bass-, Mid+, Mid-, HF+, HF-.
Image

I immediately got in touch with ATC who confirmed that I could use these terminals INSTEAD of the multi-connector to connect to the speakers. So that's what I did, using ¼" insulated FEMALE spade connectors on the 'amp-ends' of my Abbey Road cables. Just one important thing....ATC also told me that the 15" BASS driver had to be connected in ANTI-PHASE to the terminals in the SCM150. He said the multi-connector was pre-wired to achieve this, but if using the ¼" terminals, I needed to connect the bass driver's +ve terminal to the amp pack's Bass-ve, and vice-versa.

It worked well, BUT my wiring is a little on the 'tight' (ie short) side. I only had 2.4m of speaker cable to use, which gave me 0.8m to connect to each drive unit. I wish I'd had 3m in total, so I could have used 1m per bass, mid, treble.
Image

If you're interested, I have some genuine plaited Kimber cable available...I have some 8PR and some 8TC available. PM me if you're interested.

I also lined the inside of my vents with perforated leather. Any roughness inside the tube helps reduce turbulence inside the tube. The fact that it is leather, stuck on with contact adhesive, helps damp any resonance.
Image

I also applied some black non-setting plumbing material (available in a block, like plasticine) to smooth the rear chassis of the bass driver onto the rear of the baffle, and also along the legs of the chassis and smoothing the legs onto the base of the magnet, to reduce reflections, vibrations and turbulence.

Last thing I can recommend is using felt in specific places on/near the front baffle to reduce diffraction effects and reflections...a trick I learned from the BBC design for the LS3/5A...self-adhesive pure wool felt around the tweeters and also a line between the mid and bass units to reduce diffraction effects, and felt applied INSIDE of the grille frame to reduce reflections.
Image

Good to talk to you and share ideas!
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

Posts: 16
Joined: Tue Dec 20, 2011 8:33 pm
Location: North Devon, UK

Re: The sh34-76 Tweeter

Postby mademe2 » Sun Mar 05, 2017 4:26 am

Interesting stuff, thanks again for help.

Speaker cable next, any recommendations? easy to work with would be good. Do Van Damme or Beldon do anything that would fit the bill?

The other thing I have done down here is room analysis and acoustic treatment, well good, everyone should think about it!

Try those SR Blacks as well and tell me what you find.

Cheers

Mademe2

User avatar
Posts: 195
Joined: Sun Aug 30, 2015 9:47 pm
Location: UK

Re: The sh34-76 Tweeter

Postby studioman » Sun Mar 05, 2017 11:49 am

Personally I don't think there will be a lot of difference between the ATC cable and stuff like Belden cable.
My change of cable definitely made a difference. Why not try some audio level speaker cable like VDH or Kimber?
They say if you can remember the 60's, you weren't really there. Now somehow I have reached 62...oh shit, it's 63 now....How and when did THAT happen?....there's a lesson there somewhere if only I could figure it out...

Return to Technical area

Who is online

Users browsing this forum: No registered users and 1 guest