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Phil Starr

1x12" Cab Design Diary

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[quote name='LawrenceH' timestamp='1398694049' post='2436615']
Making it a little longer will initially put the wood under tension, which will act to further stiffen the panel, but after a while the tension element will be lost so it has no benefit over a brace that's exactly the right length - unless the brace is long enough to put a significant curve into the panel in which case there is a geometric stiffening effect (like an arch) but this is separate to the tension/stress element.
[/quote] I am wondering how significant that curve would have to be... but then you do move away from the easy to build idea!
When I was idly thinking of building my own cab (which would involve designing one too - I researched a bit about this, spoke to some of the guys here and quickly realised it was a bit out of my depth.... and went and bought a cab!) I did find a picture a bit like this

and wonder, for a self build - given I can put in more time than a commercial cab can, wondered if building something from a inner frame outward might allow for enough stiffness.

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[quote name='LawrenceH' timestamp='1398694049' post='2436615']
Making it a little longer will initially put the wood under tension, which will act to further stiffen the panel, but after a while the tension element will be lost so it has no benefit over a brace that's exactly the right length - unless the brace is long enough to put a significant curve into the panel in which case there is a geometric stiffening effect (like an arch) but this is separate to the tension/stress element.[/quote]+1, but that arch would have to be significant. If significant enough you may employ 6mm and even 3mm plywood panels,as I do in my Jack Lite series.
[quote]BFM and I think Phil favour the dowel approach but I'm not convinced it's sufficient on a thin-walled full-range cabinet because there will be multiple vibrational modes where the brace sits at a null, or where opposing panel attachment points are vibrating in phase, cases where sufficiently stiff axial braces ought to be more effective. [/quote]I've never found axial bracing to come even close to the effectiveness of panel to panel braces, so I only use them in the rare instance where a panel to panel connection isn't practical.

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There's a lot of compromise in any speaker design and where you end up depends upon opting for a design philosophy as well as doing all the tests and calculations. We haven't debated this in public yet but one of the issues we are looking at is tuning. I want to tune the cab for the lowest excursion at low frequencies, something that will handle low B fundamental at a couple of hundred watts. Stevie wants it tuned higher for maximum power handling. For most people neither of these would be the issue you might expect, I doubt you'd be pushing these speakers to the extremes they would get in testing or be able to hear a difference.

The same is true of cab rigidity past a certain point. Bracing of whatever sort follows a decay curve, a little bracing will dramatically improve the sound of a cab, adding an extra brace to an already well braced cab, hardly at all. Sooner or later you will reach a point of diminishing sonic returns at a cost in time, effort and weight.

The philosophy behind this cab is to make it easy to build, whilst sounding as good as possible. I'm thinking of a first time builder who wants a practical cab at a better price than an equivalent commercial cab. At the same time there will be no secrets so it is open to anyone to go for a 'better' driver or better bracing if they have the inclination. I hope a lot of you will be very happy with the sound of the basic cab.

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[quote name='JTUK' timestamp='1399633092' post='2446059']
Wouldn't mind a punchy lightweight 12 or 15 sub...
[/quote]

My original idea was to pump out some simple designs that people could build themselves. Stevie and Lawrence have persuaded me that we need to build and test our designs extensively before publishing them. If you want a sub, or anyone wants a specific design and is prepared to share their build with other people them i'm sure we could give dimensions easily enough.

For example building this speaker into a box twice the size (110l) and with a 4.6cm long 10.2cm dia port would give you a sub which would deliver 120db dropping to 116 db at 40Hz. That took me 5 mins to calculate and you could build a cab with that information.

I'm sure there are plenty of people here who would help you, or anyone else design a cab, it just wouldn't be one we had built and tested.

If not we should be able to come up with 2-3 tested and developed designs a year.

Edited by Phil Starr

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What peaked my interest was trying out an HK Elements system and whilst it ultimately failed
from our POV as it wasn't versatile enough for the gigs we do, it was interesting in that the
subs were very easily to carry and the seperation was enough on small gigs. Larger, you have to double up
on the subs and carry 4... and if you carried 4, size-wise, you might just as well carry 2 conentional ones.

We quite fancy very pokey hi quality tops...like Martin f10, or Nexo PS10's and we then feel we could
get away with 1 sub most of the time... maybe an LS500...and add the second for bigger gigs.
The 2xPS10 plus LS500 would do a pub very well, I think.

Anyway, with that thinking, I would be interested in passive subs with performance in a compact and light shell.
By that I mean 60/70lbs max in weight....pref lighter. Basically that P.A needs to carried in a decent hatchback..

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[quote name='JTUK' timestamp='1399723878' post='2447017']
What peaked my interest was trying out an HK Elements system and whilst it ultimately failed
from our POV as it wasn't versatile enough for the gigs we do, it was interesting in that the
subs were very easily to carry and the seperation was enough on small gigs. Larger, you have to double up
on the subs and carry 4... and if you carried 4, size-wise, you might just as well carry 2 conentional ones.

We quite fancy very pokey hi quality tops...like Martin f10, or Nexo PS10's and we then feel we could
get away with 1 sub most of the time... maybe an LS500...and add the second for bigger gigs.
The 2xPS10 plus LS500 would do a pub very well, I think.

Anyway, with that thinking, I would be interested in passive subs with performance in a compact and light shell.
By that I mean 60/70lbs max in weight....pref lighter. Basically that P.A needs to carried in a decent hatchback..
[/quote] Have you looked at Bill's designs? might be a ready designed and tested solution for you PA wise there already

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[quote name='JTUK' timestamp='1399723878' post='2447017']
What peaked my interest was trying out an HK Elements system and whilst it ultimately failed
from our POV as it wasn't versatile enough for the gigs we do, it was interesting in that the
subs were very easily to carry and the seperation was enough on small gigs. Larger, you have to double up
on the subs and carry 4... and if you carried 4, size-wise, you might just as well carry 2 conentional ones.

We quite fancy very pokey hi quality tops...like Martin f10, or Nexo PS10's and we then feel we could
get away with 1 sub most of the time... maybe an LS500...and add the second for bigger gigs.
The 2xPS10 plus LS500 would do a pub very well, I think.

Anyway, with that thinking, I would be interested in passive subs with performance in a compact and light shell.
By that I mean 60/70lbs max in weight....pref lighter. Basically that P.A needs to carried in a decent hatchback..
[/quote]

OK that is beyond the scope of this thread, which is about bass speakers but I'm sure several of us would be happy to offer help if you wanted to build this and share your experience, if you want to go ahead then start another thread and we will chip in with ideas. A budget would be good.

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I have found some active Yam DSR12's to use as subs.
As long as they aren't completely flaccid...and by most accounts, they really aren't
then for the price, these need a careful look...

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Have any cab builders ever entertained the using of Volt drivers ? I got some blurb inside the box that my Beymas came in, and there's some wicked drivers in the pamphlet. Not cheap by any standards though

98.5db

50-3000hz

Maximum X-max 36mm !!!

http://www.voltloudspeakers.co.uk/loudspeakers/rv3153-12/

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Volt make some well regarded hi-fi drivers, the price has always deterred me from looking at them.

the one you link to is not really suitable as a bass speaker, it is an overdamped (Q 0.27) driver specifically designed to go into a satellite system for a PA. It rolls off in frequency above 80Hz so is designed to work with a subwoofer.

Oh and the Xmax is 4mm the higher figure is the maximum excursion before it destroys itself sometimes called Xlim Your Beymas go further before distorting.

Edited by Phil Starr

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Ah - right.

TBH, i didnt see any of the Volt drivers on the website that i saw in that pamphlet

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Having found the pamphlet, they dont seem to make a dedicated full range driver for us bass boys

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Hi Luke, I've been on holiday and then my computer crashed terminally so I've been off the boil Just to recap and bring everyone up to date I've built two prototypes out of 12mm lightweight ply and have been using them at practice. I've now installed some bracing which has tamed the rather alarming resonances of the panels and tightened up the sound. I quite like the way they sound now.

I've agreed with my co conspirators to do some testing before we release a final design.

Three issues need to be resolved, the cab tuning, the port area and the wall material. The current cabs are built with four pipe ports that can be blocked off and altered in length to achieve different tuning. basically I proposed a 40Hz tuning which gives us lower excursion at extreme bass and keeps it within the speakers damage limit up to 300W others have been suggesting a 50Hz tuning which gives a touch more bass and power handling above the extremes. we need to see if there is an audible difference and if it makes any difference in actual use.

the port area issue is about balancing the avoidance of wind noise against ease of construction. Big ports are quieter but can pose construction problems or we could buy expensive(ish) flared ports. If we can use something small and simple we will, but the best way of seeing how far we can push it is to try out different set ups.

At some stage i want to open up the chance to try the speakers to basschatters to feed into the design

Edited by Phil Starr

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How do flaired ports compare in practice? Obv the effective volume of a port is larger, and I read a paper on how the flairing on both ends of a port massively lowers aerodynamic resistance in the port - in practice I dunno if it makes didley squat difference

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How do flaired ports compare in practice? Obv the effective volume of a port is larger, and I read a paper on how the flairing on both ends of a port massively lowers aerodynamic resistance in the port - in practice I dunno if it makes didley squat difference

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Hi Luke, you'll have to wait until Stevie comes on for practical experience, I've never used them. I've not noticed chuffing as a problem with restricted port areas in PA sytems or bass speakers so I've given it little thought. However I roll off the lowest frequencies when I play to avoid room resonances and over excursion muddying the sound so I wouldn't expect to notice. It has been a problem in hi fi designs I've listened to though because of the more critical response to distortions in these speakers.

The problem we're addressing here is twofold. Because we have chosen a high Xmax/excursion driver there is going to be more air moving through the port than most speakers of this size and the air speed becomes a significant fraction of the speed of sound creating turbulence. This leads to the practical problem. the cabs are small and have modest dimensions. if you increase the port area then the port has to be longer and it meets the back of the cab. You can bend the port but this was meant to be a simple build and a bent port introduces resonance problems. It can also increase the size of the cab.

The solution Stevie suggested is to use a flared port. the reduced turbulance means less noise from a smaller port. Its a neat solution but means more expense and sourcing problems for anyone building the cab.

What we hope to resolve with the prototypes is what port velocity we are prepared to live with. Mach 0.05 is the generally recognised upper limit (17m/s) but there are discussions between 15 and 20m/s. http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/24897-port-velocity-goals-aims-what-side-effects-high-port-velocity.html

This is a good illustration for the non-technical of the sorts of design compromises involved in any bass cab design. You can build a basic box and it will work, but there are all sorts of tweaks you can make to get a bit more undistorted sound out and problems at extremes of use that you can avoid.

Edited by Phil Starr

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Could this be resolved simply with a shelf/slot port, either a single or double ([url="http://www.markbass.it/upload_area/photos/0/Standard_104HF.jpg"]like this maybe[/url]) port slot arrangement?

I'm not really up to speed on the intricacies of port design, but could the testing results from the round port tubes you are using on the prototype be translated into dimensions for different shaped ports relatively easily based on area and length, or are there more complex factors that would prevent a mathematical transposition?

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if you use the same area and length the cab will be tuned to the same frequency. I'm using round ports for prototyping but the finished design will be slot ported to keep the construction as simple as possible.

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OK the latest update. The prototype speakers are now braced with a pair of braces across opposite panels andf rom the rear panel to the cross braces as there isn't anywhere sensible to fix them on the baffle. The cross braces are fixed to vane bracing which also stiffens up each panel. I've inserted some polyester damping between the rear of the speaker and the rear panel. All this adds a couple of Kg to the cabs.

The speakers have had a run out at their first gig. Also the first gig with the new band [url="https://www.facebook.com/pages/ReD-band-uk/246798508841316?ref_type=bookmark."]https://www.facebook..._type=bookmark.[/url] Here's what I found.

They got me into trouble in the first set. My preference is to keep bass off the stage and DI through the PA but my band like a very forward bass in the mix and lots of bass on stage. That's a silly thing to say to a bassist with a new rig! Initial balance out front is excellent, on stage bass was just far too loud. At the break my drummer complained he couldn't hear his own snare! I think I may have cured him of constantly asking for more bass all the time :). Anyway as far as the review goes a pair of these don't lack for volume. One would have easily coped, This was in a 250 people sized space with high ceilings not huge but bigger than most pubs or clubs.

If I had to summarise the sound in a word I'd settle on airy. The bass seems limitless (with my 4string Precision, American Deluxe). I know there is a 1dB midbass peak from the WinISD plot but it isn't really noticeable. I always roll the bass of quite steeply at 30Hz but the general feel of the bass is that it is limitless, no real changes as you run down the E string and no compression as you turn up the volume. That 7mm Xmax gives you plenty of reserves at very high sound levels and the frequency response is essentially pretty much flat. These aren't going to give you the 'punch' of an old school 2x15 or 8x10 without some serious signal processing but will give loud undistorted bass. Like I say, they shift a lot of air.

The top end is equally airy, The speakers claim a flat response up to 6kHz (-10dB) with only a minor break-up peak at 2kHz and that's pretty much what I heard. It's a bit like the sound you get DI'ing into the PA but rolled off at the top end so you don't get all the noise of fingers on strings, yeah I know, poor technique. That's the point though, without the usual midrange resonance and a bit of extra top end (without the extreme top of a horn) these are quite revealing of what you put in.

So pretty predictable really. These are fairly capable speakers for the price with a good clean bass with no bass compression at normal volumes and no real sonic nasties. Not the choice if you want a speaker with a strong character but a good modern voiced unit. One is enough for most situations a pair are seriously impressive. 14.5kg, 350W thermal, 98dB/W and about £150 for a home build including fittings and coverings. You could build one from this thread but I'll do a step to step guide once we finalise on a few details and build the final design. Cheap and cheerful 2x10 to come.

Edited by Phil Starr

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