Big Ol' Pile of Bass

Dedicated to those large boxes at one end of the room
Post Reply
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#1 Big Ol' Pile of Bass

Post by chris661 »

So I thought I might post this up after all.

This is the latest step in the quest for a really good PA system that sounds excellent, even at high SPLs. The mid-high section is a pair of 2x10" point-source cabinets. I don't like line arrays, for a variety of reasons. Without going to midrange horns (which are complicated to build and often put serious limitations on the low-frequency extension of the main speakers), they're about as loud as such a thing can go. Each 10" driver is rated for 600w RMS, and each pair of 10"s shares an amplifier capable of around 2.5KW, so they've got some headroom.

So far, I've got away with 4x 15"s in sealed cabinets, but they are by far the weak link in this system, even with 1KW per box (each one has a Beyma 15P1200Nd).
Image
According to the guys at ProSoundWeb, you want a subwoofer section capable of 10-30dB more output than the tops, depending on the musical genre etc. Those sealed subs were capable of the same SPL as the main speakers at 55Hz, and lost out below. It's obvious, then, that something bigger is needed.

After posting on diyAudio for a while and messing with some simulations, a quarter-wave transmission line was suggested and gave really good performance for it's size.

Here's a prototype:
Image

Shortly after that, I found someone selling 4x Faital Pro 15HP1060 drivers for a good price. They simulate identically to the Beyma units, so I went for it. I realised when I got the two different drivers next to each other that, actually, there's a 2.5" difference in mounting depth and there's no way the Faital drivers would go into the transmission line cabinet. Bugger. Happily, with the removal of a couple of internal panels the transmission line could become a ported enclosure, and keep a similar tuning frequency, phase curve, etc etc.
I've got the MDF for a second prototype because I want to make absolutely sure it'll be okay before committing to building eight of the things.

Just now I've connected up each of the Faital drivers in turn, and given them a quick thrashing. The suspension feels noticably looser now, and no wonder. The program material used for break-in had a lot of sine-wave-like content, and the amplifier I was using had the -6dB light lit pretty often, which indicates a minimum power of 250w. The drivers were free-air, and hit in the region of 35mm p/p travel. There was a lot of wind noise from the air vents, but there was no indication of things getting warm.

The Beyma drivers are still in their boxes (and in use at gigs), but here's the four Faital units:

Image
Image
Image

When I've got them all built, I plan on either using stacks at each side of a stage (plus plenty of loadstraps), a really big centre cluster, or experimenting with cardiod arrays. It's going to be a fun few weeks while I get these built.
According to the simulations, the pile of subwoofers will have 15dB of headroom over the main speakers. That's going to be plenty for me.

Chris
Cressy Snr
Amstrad Tower of Power
Posts: 10552
Joined: Wed May 30, 2007 12:25 am
Location: South Yorks.

#2 Re: Big Ol' Pile of Bass

Post by Cressy Snr »

Terrifying ! :D

Those Faital drivers look bloody good.
Generally speaking, I like the build quality of their drive units.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
User avatar
Scottmoose
Needs to get out more
Posts: 1802
Joined: Sat Sep 08, 2007 11:03 am
Contact:

#3 Re: Big Ol' Pile of Bass

Post by Scottmoose »

No surprise -they're pro units, so built like tanks. Nice piece of casting for the basket. Good tolerances usually too.
'"That'll do," comes the cry of the perfectionist down the ages.' (James May The Reassembler)
Website www.wodendesign.com
Community sites www.frugal-horn.com & www.frugal-phile.com
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#4 Re: Big Ol' Pile of Bass

Post by chris661 »

Scottmoose wrote: Wed Apr 12, 2017 11:30 pm No surprise -they're pro units, so built like tanks. Nice piece of casting for the basket. Good tolerances usually too.
Tanks with some HiFi features, like a demodulating ring in the magnetic structure. There's also dual spiders to keep the voicecoil in alignment when you put some power down.

I'm hoping to get the set of eight done in time for this year's festival season. Prototype is being started today, and then there'll be a lot of testing, albeit a little more carefully than last time where one of the Beyma drivers was subject to around 500w of 15Hz sine waves (well below the ~38Hz tuning), which bottomed it out and folded the cone. The 2" peak-to-peak travel was impressive to watch, but a recone wasn't cheap. I'll certainly know better for next time.

Chris
User avatar
cressy
Shed dweller
Posts: 2906
Joined: Fri Aug 03, 2007 7:07 pm
Location: the great white space
Contact:

#5 Re: Big Ol' Pile of Bass

Post by cressy »

Ive been impressed with the faital range too, my idea for my next spekaer build uses a 6fe200 and sb acoustics tweeter on an o/b and a 10fe200 in a sealed box at the bottom. I figure as the sb and 6" driver are about 92 db and the 10" driver is about 96db, hopefully the efficiency loss from the sealed box should bring them all about into line. With a sealed box of about 50l (vas is around 53l) I should get quite a fast transient response from it to match the 6" driver. Thats the thinking anyway.
Think the metronome tapered frontal aspect, the sealed box at the bottom with the bass driver on the front and low to get some floor reinforcement, and the 6" and tweeter on the o/b above it so it looks abit like a magneplanar static
User avatar
Scottmoose
Needs to get out more
Posts: 1802
Joined: Sat Sep 08, 2007 11:03 am
Contact:

#6 Re: Big Ol' Pile of Bass

Post by Scottmoose »

FWIW Ant, transient response up to the mass corner (aka the acceleration BW) is dominated by system Q; to keep ringing low ('fast' response) this needs to be < 0.707 (maximally flat) with 0.5 being optimal, or as optimal as is possible at any rate. From a brief gander at the data sheet, 50 litres sealed for the 10FE200 gives a peaking Q of roughly 0.85 - 0.95 depending on your damping coefficients (up to a point more will lower Q) so it may (may) not sound as fast as you'd like; you might want to consider a larger box, or a leaky sealed alignment to give you some extra alignment damping. The latter has its own compromises of course, but can work well.
'"That'll do," comes the cry of the perfectionist down the ages.' (James May The Reassembler)
Website www.wodendesign.com
Community sites www.frugal-horn.com & www.frugal-phile.com
User avatar
cressy
Shed dweller
Posts: 2906
Joined: Fri Aug 03, 2007 7:07 pm
Location: the great white space
Contact:

#7 Re: Big Ol' Pile of Bass

Post by cressy »

Im sure i'll be back picking brains when i get around to them :D
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#8 Re: Big Ol' Pile of Bass

Post by IslandPink »

cressy wrote: Thu Apr 13, 2017 10:21 am next spekaer build uses a 6fe200 and sb acoustics tweeter on an o/b and a 10fe200 in a sealed box at the bottom.
Interesting units - & thanks for prompting me to visit the Faital site, as I think I've found an even better driver for the folded horn ( 8FE200 ) with Fs of 80Hz and low Rms of 0.6 :D
"Once you find out ... the Circumstances ; then you can go out"
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#9 Re: Big Ol' Pile of Bass

Post by chris661 »

Prototype number 2 is gluing in the garden. Top, bottom, and back gluing to one of the sides. Driver is mounted to the baffle, and the glue on the t-nuts is drying too. Another couple of rounds of glue to do the rest and then I'll let it dry overnight.
I'm hoping to give it a test tomorrow, though it won't be anywhere near full power. We're on good terms with the neighbours, and I'd like to keep it that way. These cabinets are capable of well over 120dB without any room gain.

I'll be testing impedance and frequency response for both the Faital units and the Beymas. I'm hoping they come out as close as the simulations suggest (so I can mix and match with no ill effects), but a touch of EQ either way isn't a big deal.

Chris
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#10 Re: Big Ol' Pile of Bass

Post by chris661 »

It needed a bit of work to test, but I've just tested this cabinet to do 125dB (groundplane) when the amp clips. Looked like the driver had more in reserve, too. No nasty noises, it just sounded like thunder.

All of them working together would theoretically produce 143dB, which is a whole different level and would be a lot of fun on the occasions all of the volume will be needed.

Chris
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#11 Re: Big Ol' Pile of Bass

Post by chris661 »

So, a big pile of birch plywood has just landed. It's sorted into piles, so now I need to start drilling, cutting, routing, sanding and then staining.

There's a big gig on the 3rd of June. I'd like to have all 8 done for then, but I'm not sure I'll get them all done in time so it might just have to be four. Should still be quite a racket, though.
If I do get all 8 done I'll probably need a seperate mains feed just for the subwoofers, which will be run on a pair of Behringer NU6000DSP amps, for about 1KW peaks per box.

Chris
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#12 Re: Big Ol' Pile of Bass

Post by chris661 »

Well, I got four built for the festival last weekend. Outdoors for a few hundred people, and you could feel the bass at 40'. Not bad for 2x15" a side.

Image

Image

There's a couple of big events in August that I'd like to have all eight for, but this is good for now.

Chris
User avatar
Dave the bass
Amstrad Tower of Power
Posts: 12273
Joined: Tue May 22, 2007 4:36 pm
Location: NW Kent, Darn Sarf innit.

#13 Re: Big Ol' Pile of Bass

Post by Dave the bass »

Every-time I see this thread come up... I think I've put weight on!
"The fat bourgeois and his doppelganger"
User avatar
andrew Ivimey
Social Sevices have been notified
Posts: 8307
Joined: Mon Jun 11, 2007 8:33 am
Location: Bedford

#14 Re: Big Ol' Pile of Bass

Post by andrew Ivimey »

I thought it was your thread -well, you would... but I didnt see why Chris kept on posting and posting and ne'er a personal comment to the bassbikeking of Dartford - funny that...
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
chris661
Shed dweller
Posts: 2556
Joined: Mon Feb 22, 2010 7:29 am
Location: Sheffield

#15 Re: Big Ol' Pile of Bass

Post by chris661 »

Oh, look, Photobucket has decided to stop hosting images for me.
I'll upload them to my website from now on.

I'm rather pleased with the PA system as a whole. Had a very big event last Thursday, covering a rugby pitch. I was a bit worried.

I won't repeat it all - here's a link to the blog post: http://www.grimshawaudio.com/single-pos ... l-and-more

After that test, I was grinning for the rest of the day.

Chris
Post Reply