subs for diy ATC scm50

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lejockey

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#1
Hi guys. I am looking to build 2 subs for my recently completed diy version of ATCs scm50. I want 2 subs, so I can have one each side and use the atc's as a small but ultra high quality pa system. Each sub would have twin 15s. Question is, which 15s. Any recomendations? Fane collosus 15xbs have my attention, but are there any alternatives? Maximum of 300 per drive unit ideally.

Thanks in advance
 
#2
SCM50ASL (Active)/SCM50SL (Passive)

SCM50 | ATC Loudspeakers
Frequency Response -6dB: 38/40Hz & 22kHz
Sensitivity (sine wave): 85dB @ 1W @ 1m
Max continuous SPL @1m: 112dB SPL
Drivers: HF 25mm Mid 75mm LF 234mm Super Linear

Hi,
Maybe you are barking up the wrong tree, maybe not. 😀
The 15" Fane Colossus 15XB is not exactly a sub driver but more of a mid driver. I mean, I wouldn't call a 100Hz ""PREDICTED BASS RESPONSE" a desirable sub for your purposes whatever they will be. 😉
Fane COLOSSUS 15XB

What is the volume (net) you are about to use (200 L or more?) and what's the use you are going to give it, PA or home use for LF extension?
http://www.fane-acoustics.com/downloads/Cabinets15inch125L.pdf

The drivers used (in any application) are directly related to the internal dimensions of the speaker/sub they are in. So what is the available internal (net) volume/footprint you have available on each side for each pair of drivers, 100L, 200L, 300L?! Just make mention of it, so that we can start somewhere, you and us. :scratch:
 
#4
Maybe my memory fails me, but I have but I thought the fifteen inch collosis xb was the 15 inch bass diver they made for subs. I have built before but ten years ago. Anyways, I was just after some ideas for alternative drive units, fifteen inch drivers which produce good quality bass. In my original post I did say that it was so I could use the acm50s as a small but ultra high quality pa system. The volume of the cabinet would be appropriate for the drive unnit.
 
#7
"a small but ultra high quality pa system"

A speaker with 85 db absoluely cannot be used as a PA system - you'll fry the voice coils (which would be a pity considering how nice they are) if you play them at anything approaching the dynamic range of PA.

I would really, really recommend against this. Removing the bass will reduce excursion on the woofer, but will do nothing for the tweeter, and so the whole thing will burn out.

I would absolutely, unreservedly, not attempt to use 85db speakers as a PA.

Just my $0.02, but there's a lot of money at stake here with those speakers.

cheers,
-Tal
 
#8
Hi,

Double 2x15 PA subs in nowhere near whats needed
for a pair of ATC SCM50's, it is way over the top.

At home one LAB12 in a 100L tuned to 22Hz and
around 300W (BASH ?) will do the job. 2 of them
x/o a bit higher will make a system that will go
pretty much as loud as the ATC's can take.

Can be used as as a high quality low volume PA , for the
right sort of music, but will be hopeless for the wrong sort.

rgds, sreten.
 
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#9
@tal they can produce 112db continuous? That's enough for a small, high quality pa surely? ATC already make PA cabs using the same mids and tweeters anyway, used in Venus like Ronnie Scots. Twin 15s would be fine surely, able to move enough air without being driven very hard. ATC make cabinets with twin 15s and the same mid and tweeter, but it isn't possible to buy them individualy.
 
#10
If you're going to insist, use 1x15" a side. Seriously. I'm part way through a 1x15" cab that's ~120L, and will do 125dB@1m in 2pi space (At driver Xmax). One of those a side would be more than enough. -3dB point is just below 40Hz.

112dB is very quiet in PA terms. That said, what's the peak output (and survivable duty cycle) of the ATCs?
I they'll go to 122dB peaks a few times a minute without issue, you're heading in the right direction.

NB: 122dB is a 10-fold power increase on 112dB, so I'd be really impressed if they manage this.

After all this, though, do you really want to even run the risk of blowing the ATCs?

Chris
 
#11
This is only going to be for a 40 person marquee. Its going to travel around festivals, offering the smallest but best sounding stage at various events. 122db at 1m is far too loud for this purpose. Perhaps a single 15 each side is okay then. I was just after some sugestions for very high quality 15s really. My thoughts were more drivers moving less would mean them operating n a more linear fashion?
 
#12
I'd take a decent 1x15" a side for this sort of thing. Two cheap drivers might have lower distortion than one good one for a given SPL. Maybe.
But your 2x15" cabinet is going to be much larger and heavier than the 1x15" cabinet.

Here's what I'm using.
http://www.beyma.com.ua/wp-content/uploads/2014/02/15P1200NdN.pdf
Cabinet's almost done (just waiting for T-nuts), so will have some impressions shortly.
B&C also do some very good drivers. Download WinISD (or Hornresp) and run some simulations.

It sounds like you're going to be using the speakers for live music. Is this the case?

Chris
 
#13
Goinng to be playing experimental electronic music mainly, soundscape and 'found sound' based. Bass has to be deep, so perhaps a single 18 each side instead? The Bayer drive unit looks nice. If money was no option though, what would you buy?
 
#14
No option, or no object?

If I could spend as much as I wanted, I'd get the best 15-18" drivers I could, and design a cabinet that'll go down to 35-40Hz with enough SPL for what you're after. Then make it as compact as possible, sacrificing maximum SPL according to how small it needs to be.
1x15" per side would probably be plenty, but 18" drivers would probably be best set (in terms of T/S parameters) to hit the low-30s.

Listen to Slam by Pendulum. 40Hz tuning covers all of the low-end on that track, to give you an idea of what's needed.

If money was a serious consideration, there are two options.

1 - a really big tapped horn, single 15", get as much out of that one driver as possible. Aim for 40Hz, but don't be disappointed with a higher cutoff. Use something like an Eminence Delta 15.
2 - if portability is a concern, you're going to lose out on low-end extension. Probably still use the Eminence driver, but tune higher with a smaller box.

Chris
 
#15
I am coming round to the idea of the single 18 on each side now. I don't think I would want to make a horn enclosure. I don't need much the effeciency of a horn, and to get a low 30hz response the mouth would have to be just huge! If i port the enclosure, it would just be to support the drive unit at its reasonance. I might just build a fairly large sealed enclosure with a single 18 so the roll off is gentle and the bass sounds as smooth as possible. I am not a big fan of emminence kit. In the past i have used PD, Fane and B and C, but am wandering whether there is something more high end i could use. If going for a single 18 per side, i would want to spend 500 to 600 per drive permit ideally.

Thanks, John
 
#16
Sealed 120L-220L

Here's a list for sealed (volume L is in reference 120.0 to 220.0 L):

1. Dayton Audio UM18-22 18" Ultimax DVC (190.0 L)
Dayton Audio UM18-22 18" Ultimax DVC Subwoofer 2 ohm Per Coil
2. Aurasound NS18-992-4A (220.0 L)
The Madisound Speaker Store
https://www.solen.ca/pdf/aura/NS18-992-4A.pdf
3. Stereo Integrity HT 18 (160.0 L)
Data-Bass
4. Dayton Audio RSS460HO-4 18" Reference (130.0 L)
Dayton Audio RSS460HO-4 18" Reference HO Subwoofer 4 ohm | 295-472
5. McCauley 6174 (210.0 L) / 6260-8 (180.0 L)
McCauley.com : Home
http://www.bodziosoftware.com.au/Subwoofer_Design.pdf
http://www.diyaudio.com/forums/subwoofers/106338-where-buy-mccauley-6174-a.html
6. BMS 18N860/2 (120.0 L)
http://www.bmsspeakers.com/fileadmi...neodymium/15_18/bms_18n860_t_data_2009_06.pdf
Welcome to Assitance Audio
7. Beyma 18LX60 (v2014 - 190.0 L)
Beyma Speakers - Beyma 18LX60 speaker - Beyma 18LX60 1200 watt 18" woofer for all bass applications. Beyma 18LX60 and other Beyma 18" speakers here.
8. McCauley 8251 18” (T/S parameters?)
From the R&D workshop at McCauley Sound - Blogs - Sound Forums Network
https://www.facebook.com/media/set/?set=a.10151984476924812.1073741825.238277524811&type=3
http://www.mccauleysound.com/files/M882_Cutsheet.pdf
Follow up: the McCauley 8251-8 18" Loudspeaker - Blogs - Sound Forums Network
 
#19
To get the kind of levels and extension you're looking for you don't need 18" drivers, this gives far more SPL than you need in a much bigger box than necessary.

A BMS 15N840 is much more appropriate, low distortion and plenty of SPL down to 35Hz or so in an easy-to-build 85l reflex box, see product data sheet here:

Overview
 
#20
lejockey said:
I am coming round to the idea of the single 18 on each side now. I don't think I would want to make a horn enclosure. I don't need much the effeciency of a horn, and to get a low 30hz response the mouth would have to be just huge! If i port the enclosure, it would just be to support the drive unit at its reasonance. I might just build a fairly large sealed enclosure with a single 18 so the roll off is gentle and the bass sounds as smooth as possible. I am not a big fan of emminence kit. In the past i have used PD, Fane and B and C, but am wandering whether there is something more high end i could use. If going for a single 18 per side, i would want to spend 500 to 600 per drive permit ideally.

Thanks, John
Click to expand...

Ah, so you were asking about cost-no-object.

I wouldn't recommend sealed subwoofers for this use. You need a lot of displacement to get down low. Most subwoofer drivers have Qts in the ~0.3 range, since this strikes the optimum balance between cabinet size and low-end rolloff. A Qts that low in a sealed box means you'll need a lot of eq (and therefore power, resulting in more distortion in the motor) to get down to 30Hz.

A quick simulation in Hornresp with this driver
http://www.beyma.com.ua/wp-content/uploads/2014/02/18P1200NdN.pdf (the 18" version of mine) gives a 175L (including port volume) ported box tuned to 30Hz.
That's 93dB@2.83v@1m at 30Hz, going up to 98dB@1w@1m at 100Hz. Its a fairly linear slope, so you could implement a too-low crossover point to drop the top end slightly.

Driving to Xmax within the pass-band, you're looking at 120dB from 30Hz, with the same slope upwards (ie, 125dB@100Hz). That's 65v rms input.

Note how much demand going to 30Hz is: my single 15" in a smaller cabinet will comfortably outrun this design by only aiming for 40Hz.
The 18" in a 40Hz box wins out, but not by an awful lot. I'd still put my money on 15"s. You lose out on a couple of dB, but the cabinet is considerably smaller.

Back to sealed for a moment, that 18" is 83dB@2.83v@30Hz. The 10dB to make up is a 10x power increase. That's a lot. Seriously.

Some things to think about.

Chris
 
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