So Thorsten has broken cover ...

[Stereo Mic]

Classier yes.

All my own work too, you sell out

As I mentioned, those are not mine, although I did build the sub enclosures- modified aestetically

The drive units are only 15" and my main speakers have 15's anyway.

Nice motor assembly....

Anyway, size doesn't matter as they say.

 

[Paul L]

Can I just say what a pleasure it is to read 18 pages of mutual respect?

No, oh well, never mind.

In the background, the attempt to keep a parallel thread of a genuine thread is commendable. Nick, did you really berate SME decks on here somewhere? Come on, wake up from the stupor, stand back and ask yourself if you really think SME is average or if you're merely succumbing to a personal spat. I don't believe my SME10 is merely average, not the best I'm sure but it's no toy. I don't think I've seen El Diablo on this much medication before either, he must have had some very boring shifts this week to keep this up.

 

[KUB3]

SM, now that is a motor. Vmax? In metere's?

I want to build a coffee table with one of those!!!

 

[ShinOBIWAN]

Sub appearance can be very misleading.

I used to own a stonking great matt black 15" celestion bass driver, with a HUGE magnet assembly and vast cast frame. The thing looked like an ATAT's knee joint.

To my absolute amazement it was well and truly thrashed by a tiny 10" JL pip squeek, with a mere pressed steel chassis and tiny magnet. The JL half pint cocked a leg up and wee'd all over it, in terms of out right volume, depth, accuracy, you name it.

Forget voice coil diameter, or magnet size. IME, it's the motor's vmax that make the difference.

Agreed.

Its got the TS credentials too though, definitely no all show no go driver. Motor strength looks hefty with a BL product of 25 and moving mass is low.

It isn't intended to be an absolutely depth charge, but will reach happily into the upper teens. The main goal was a tight and very nimble sub that gets around the problem of drivers with a low resonance frequency.

This design is the results of a collaborative effort between me and Scott - a bright audio enthusiast from the US.

Here are the primary goals that Scott quotes:

Specifically I was looking for two *basic* properties in the design:

Low compression (..meaning a volume that easily exceeds the driver's VAS yet is still "small".)

A specific impeadance curve that fits within the low compression/small volume requirement. In this instance an operating passband that is mostly "mass" controlled and therefor current controlled - which all else equal is more linear operation. Moreover I wanted the driver in-box resonance above the passband as much as possible and then back down to that resistive impeadance that is "mass" controlled as quickly as possible.

In addition to those 2 requirements it needed LOTs of force from the drivers motor and this means a very high BL product.

Ultimatly for the given design it isn't that in-efficent for a system capable of extending to 17 Hz relative to other drivers.

And when asked why we'd choose a driver with an Fs of 42hz to build a sub:

Trust me, they go surprisingly low. I was running them in yesterday and the performance was pretty exciting. Bearing in mind that I've had 15" ATC's, 15" Volts and Stryke AV15's before these little 12's then it takes something a little out of the ordinary to get me excited.

Its all in the implementation, the aim is to move away from driver resonance distortion by sacrificing output at the bottom end and using EQ to drop the upper range to level match to the output at 20hz. I say sacrificing, this design will still do a 80dB 1w/1m @ 20hz anechoic. Put it in a room and you can expect that to rise to around 85-86dB, then consider that the drivers handle 1000w continuous under strict AES 2 hour testing and your looking at a peak SPL figure at 20hz of 110dB anechoic/~115dB in-room. Then build two and your looking at 120dB+ @ inroom at 20hz or 118dB+ at 16hz.

Considering that I mostly listen at 90dB at the most and 120dB is perceived as 8 times louder than that, there's plenty of headroom.

Just to show how well this design does; Model the Tumult 15D2 in a 300ltr sealed enclosure and the BC 12TBX100 in ported 63ltr/19hz tune and look at the max SPL figures - they're identical at 20hz. And that's a 15" Tumult with nearly 3" excusion vs. a 12" pro driver with less than 1".

Here's some pics of the enclosure design that I drew up:

Plan view from the front:

Side view:

They're exactly the same height as the mains I built with just a little less depth and very slender(about the same as the mains) when viewed front on. They'll be two of these BTW, one for each loudspeaker.

I started on the cabinets yesterday so haven't done much but here a shot of the driver bracing:

And that's all the MDF needed to build just a single sub

 

[ShinOBIWAN]

As I mentioned, those are not mine, although I did build the sub enclosures- modified aestetically

The drive units are only 15" and my main speakers have 15's anyway.

Nice motor assembly....

Anyway, size doesn't matter as they say.

Driver porn!

Here's a couple more of the 15" Volts I also tried out:

 

[JonR]

Nick, did you really berate SME decks on here somewhere? Come on, wake up from the stupor, stand back and ask yourself if you really think SME is average or if you're merely succumbing to a personal spat. I don't believe my SME10 is merely average, not the best I'm sure but it's no toy.

Paul, this is the same guy remember that thinks a Kondo M77 preamp, no less, is neither accurate nor can handle most of his record collection. Go figure!

 

[ShinOBIWAN]

shinobiwonk bores again.

Oh god, I said something very slightly bad about ATC and now bud is stalking me.

P1ss off won'tcha, you pest.

I'm exchanging stuff with S&M. If he or anyone else says I'm boring them then I might take notice.

 

[ShinOBIWAN]

You are terribly dull, and you keep on using naughty words. It doesn't make you look very pleasant.

"Every action has an equal and opposite reaction - Dolly Parton

If your so easily offended then quit the stalking and get over the fact I spoke ill of our lord god ATC.

I can see that now Thorsten has left, you'll need someone else to make yourself forget about how crap things are your way.

I'm not really very tolerant of idiots.

 

[Tenson]

Have you had a chance to listen to the B&C's yet Ant? I pondered between a pair of B&C (not those ones) and the Eminence but went with the Eminence as it seemed to have the advantage in the midrange performance which gave me more design options.

How well do you think those B&C's work up to about 300Hz / 400Hz?

Also why are you going for a double wall on the sub rather than just thicker MDF? Are you not tempted to try other materials that don't need to be so thick? Aluminium / honey comb aluminium for example? Maybe form the main body from concrete with lots of PVA mixed in then skin with MDF when nice and dry. I even wonder about thick Nomex as a non-resonant cabinet.

 

[ShinOBIWAN]

How well do you think those B&C's work up to about 300Hz / 400Hz?

They've got a fair amount of VC inductance(Le is 1.6mH) so don't work up very high at all. I'd only use them to 150-200hz at the most. I'll be crossing them around 40-50hz so its a non issue.

Also why are you going for a double wall on the sub rather than just thicker MDF? Are you not tempted to try other materials that don't need to be so thick? Aluminium / honey comb aluminium for example? I even wonder how thick Nomex would work as a non-resonant cabinet.

Subs rely less on fancy materials and more on sheer mass, stiffness/rigidity, heavy bracing and damping. The idea being to shift the resonances up higher with a narrow Q so that they're out of the subs passband.

I'd completely agree if we're talking about a midrange enclosure but MDF has a good low end resonance profile with the more major problems at 400, 700 and around 1Khz. Its ideal for subs in other words.

The panel thickness came about through the desire to sub divide the larger panels into many smaller ones that had higher resonance frequencies. This required the use of 'skinning' techniques whereby you have a cabinet within a cabinet.

All this is just another way that works well, with a minimum of fuss. Scott(who drew up the rough idea) originally wanted a cabinet with a 4" cavity all the way around which was filled with kiln dried sand and a 3" thick concrete baffle. I'm quite sure that that would have been *the* most inert cabinet but the fact was that it took up 170ltrs with a 63ltr internal volume!

 

[Tenson]

The idea being to shift the resonances up higher with a narrow Q so that they're out of the subs passband.

Surely something light but very, very stiff would do that best? I agree MDF is great for ease of build though! 18mm MDF seems to have a major resonance around 170Hz.

But anyway it looks like a killer sub! Too big for me though and another big finishing job

 

[ShinOBIWAN]

Surely something light but very, very stiff would do that best? I agree MDF is great for ease of build though! 18mm MDF seems to have a major resonance around 170Hz.

But where's the damping on a material like that? Nice for a midrange enclosure but less good for heavy duty bass.

The resonances in 18mm MDF shift and change in amplitude depending on the panel size, bracing and thickness.

18mm on its own:

With bracing:

As you can see, with bracing it shifts the resonances well out of the subs operating range.

I'm using pretty extensive bracing as well as the subdivided panel technique I used with the Perceives which raises the resonances compared to a single large MDF sheet. The wall thickness adds mass extra damping and further stiffens the enclosure to raise resonances further.

It worked very well on the bass cabinet for the Perceives, so we'll see how it copes in a more heavy duty capacity.

But anyway it looks like a killer sub! Too big for me though and another big finishing job

Its not going to break any depth or SPL records but I'm really looking for something that can match the dynamics of the mains in the same effortless way. Hopefully its 4th time lucky for this sub attempt.

I think I'm getting to the stage now where I could spray an entire car in a day, blindfolded. I've had plenty of practice over the last year. Time is running out too! The weather will start to turn in a month or two so I better get my finger out on this one.

 

[Tenson]

Does MDF have that much damping? It certainly has a slight flexibility but I wouldn't think it has much way to convert the energy, just store it. Obviously bracing to the opposite panel will help huge amounts as they will be out of phase and cancel each other.

I would think, and certainly like to try it one day, that something like 2 sheets of 1/2" aluminium honeycomb with a layer of latex painted on and pressed between them would do a great job. Very light weight, incredibly stiff and a very lossy self damping. Go to the effort of bracing it with aluminium as well, and it should make for quite a nice box with a resonance well out of any bass or even mid-bass drivers range. The problem is having the guts to try it out!

 

[anon_bb]

All speakers colour the reproduction - PMC included - that is true. It is also true that I find their colourations particularly easy to bear. However having said that they are more accurate than most and that is borne out by the fact that what I hear bears very strong relation to the live experience. Most speakers and systems don't. Some - like kondo et al - don't even try.

Bub - go and listen to some real hifi.

It seems I have woken the valve brigade form their opium induced slumber. Tbe kondo system sounded "nice" however it was neither accurate nor broad in its ability. Let's stick the clash on it and hear it utterly fall apart.

Shin - what did you think of the volts?

 

[murray johnson]

Good morning BBV,

What loudspeakers did you make your considered assessment of the Kondo electronics on? I suspect that you haven't heard it with speakers intended for reproducing the higher spl's you seem to crave but maybe I'm wrong.

I have heard an active PMC system but I didn't think it was at all comfortable playing at high levels. Actually it was rather unpleasant.

 

[anon_bb]

As memory serves it was Living Voice

I dont always play at high SPL The option is nice though

 

[The Devil]

It's a good thing your room is soundproofed, perhaps?

 

[Stereo Mic]

I'm using pretty extensive bracing as well as the subdivided panel technique I used with the Perceives which raises the resonances compared to a single large MDF sheet. The wall thickness adds mass extra damping and further stiffens the enclosure to raise resonances further.

I'd agree. My cabs had substantial bracing, and were constructed from 1" MDF with a 2" MDF sandwich for the front baffle. Here's an early picture showing the bracing, which is recessed 6mm into grooves in the main cabinet walls.

These will not win any prizes for ultimate extension- they were originally designed for use in a Tact controlled sub/sat set up crossed over to the mains at 350hz. Low distortion was therefore of more importance. For a pure subwoofer, I would use a very different drive unit. I did play with the radial volt in the same cab and it's a punchy little sod! Again though, for pure sub bass, it really doesn't cut it IMHO.

 

[Stereo Mic]

Murray,

he really is beyond help. Maybe you'll come back in 10 years and find him in big trousers and owning an M77. I doubt it though - he needs to buy a house, get a larger living room, and fork out for his therapy before he considers upgrades - and all three are likely to stretch the finances.

 

[wadia-miester]

Nick, really does need to experiance some quality systems before passing comment I feel guys
Shin, you obviously didn't see my previous post, when constructing your transducers (nice craftsmanship btw), did you use your chord amp in the voicing of them?