Arrival of the Evil Twins, SUB1500 cabinets

[Robh3606]

Wow

Very Nice!

Rob

[MJC]

Are you using any kind of a filter on the 1500s?

[sebackman]

Hi all,

I have no idea why there are two identical posts above. I only submitted one.

Frode, I have tried to find a used LAB power amp at a decent price but compared to the competition they are still too expensive. Especially if you compare to used units in the US. If you have one for sale, please PM.

For us in Europe wanting to buy used US units, the introduction of switched power supplies is a blessing. From the Crown range of amps the K2, CE4000 and CTs series are all usable in both 120V and 220V environment. The K2 needs a different power cord, the CE4000 is just to plug in and the CTs need a jumper change in the PS.

MJC, the system is a HT system where I will use a digital pre-amp (Meridian 568 or 561) feeding 24bit@96kHz to an all digital crossovers with built in DACs and then feed my 14 power amps. The fronts are 3-way designs and the centre/rear are two-way designs plus the two Evil Twins. XO to the subbs will be 60-80Hz and an Urei 6290 will feed them. Two Urei 6230 will feed each of the rears and the fronts/centre will be fed by a Crown CTs8200 (8x200W). Below is a picture of the centre and the rears.


Regrads
RoB

[Frode]

No, I doesn't have a LAB amp. There seems to be some for sale here in Norway, but I haven't compared prices. The problem with many ebay sellers is that many of them won't ship to Europe. I'll just have to keep my eyes open, I guess.

Frode

[jcdahl]

Very nice work (Evil Twins)... What are the dimensions of each box?

I am considering 23" W x 23" H x 16"D made out of two layers of 3/4 MDF laminated using contact cement to isolate the inner MDF layer from the outer MDF layer (total 1.5" wall thickness) They will have an internal volume of 3.8 cu ft minus interior bracing and cone volume. I will fill them each with 2 cu ft of dacron wool (acousta-stuff from PE)

Covering them in cherry or walnut veneer and standing them on tapered spikes.

I like the look of exposed cones. I don'k know if it is a good idea or not.

I am going to use a Mackie M2600 (700 watts per channel into 4 ohms ) with mine. Also, I have ordered 4 pole Speakon 30 amp connectors for them from PE.

[sebackman]

Hi jcdahl

The cabinets are 450mm (17.7") wide, 400mm (15.75") deep and 600mm (23.6") high.

The volume is calculated to

Gross Material Net
Sub Outer Thickness Inner
Volume in mm Volume
With 450mm 40mm 370mm
Hight 600mm 40mm 520mm
Depth 400mm 40mm 320mm

108 litre 61.57 litre
3.81 cu ft 2.18 cu ft
Driver 5 liter
Brasing 3 litre

Net 53.57 litre
1.89 cu ft

The material is dual layer 2x20mm (4/5") MDF pressure glued together and with thick Oak veneer on the outside. The bracing is made out 1" MDF and done in both dimensions, side-to-side and back-to-front, for maximum rigidity. The bracing is screwed and glued.

They are currently filled with dual layer of 120mm fiberglass fill. It's called "Gullfiber" over here. It seems to be ok according to my initial measures. Maybe a little over dampened.

They stand on "stabilized soft (30 degrees) EPDM rubber" feet. They should limit the amount of vibration coupled to the floor.

I would avoid spikes unless you fancy the design aspect of them. From a sound perspective they can sometimes do more harm than good. You may get the speaker to be “coupled” to the floor but at low frequencies that may introduce all sorts of anomalies.

If you isolate the cabinet from the floor the bass gets less interference from the surroundings and hence much better definition. I have tried both on the Evil Twins and spikes were a disaster.

If you build a sub where there is no problem with interference between drivers or modulation, the cabinet can really move pretty much as it pleases as long as it does not mechanically transfer vibrations to the floor or has resonances in it self.

http://www.st-and.demon.co.uk/AudioM...nes/speak.html

http://www.sonicdesign.se/sdfeet.html

Let your ears be the judge for you.

I'm using an UREI 6290 (2x600W) to power them and I would not hesitate to use a bigger amp. -Maybe with some top end limiter.

Best regards

//Robert

[Alex Lancaster]

"They should limit the amount of vibration coupled to the floor and by the laws of physics increase the amount of energy transported into the room."

Actually, quite the opposite, by the laws of physics.

Alex.

[4313B]

"laws of physics"

scofflaws abound

In any case I think the little feet are cute and I want some! When my wife finds out my loudspeakers have cute little feet, and that those feet can get cold, she might not want to kick them out of the house!

[Alex Lancaster]

And of course there are those "Audiophile" little feet socks, for only $99.99.

[4313B]

Yeah, but I'm not going to tell her about any socks, or shoes, or boots! She has to think they are bare feet. If she starts knitting or cobbling then my loudspeakers are done for!

[sebackman]

Hello,

Thanks Alex. -A careless use of words.

I have removed the "and by the laws of physics increase the amount of energy transported into the room." in post above to avoid misinterpretations.

The meaning was, besides the valuable WAF increasing side effect commented by Giskard above, to reduce vibrations transferred to the floor. And they do just that. They are soft enough to absorb vibrations and yet stiff enough not to be deformed.

Please see http://www.paulstra-vibrachoc.com/ for more info and calculations.

There are many far more educated and experienced individuals that have spend miles of text debating on the topic of soft or hard feet under speakers so I have no intention to get into that.

The only thing I can say is;
Try for your selves and let your own ears decide for you. I did.

Best regards
//Robert

[jcdahl]

Thanks everyone. The spikes will penetrate my carpeting and couple the boxes to the concrete (6" tick) floor. I will try both. I have some elastomeric rubber little feet used for vibration isolation for precision measurement equipment.

What is your opinion on the 3.5 cu ft sealed enclosure? should it be larger or smaller?

Thanks,

[Alex Lancaster]

Hi Robert and friends:

As stated, the cone as a diode depends on a perfect cone, impossible.

While it is important in various degrees to isolate components from vibration, specially in turntables, because they are so sensitive; Speaker cabinets, apart from internal rigidity, need to be as unmoveable as possible so the cone can compress and rarefact air to reproduce sound, otherwise they swing back and forth according first to Newton, and then others, when You have a hysterical coupling such as rubber; IMHO, speaker boxes should be as heavy as possible, and bolted rigidly to the floor.

If Your floor or walls are more elastic than concrete; Then there are WAF and neighbor factors, etc., which could be a lot more important.

Alex.

[Mighty Saturn 5]

[quote=sebackman]Hi all

Since there have been so much discussion on the SUB1500 driver I thought I would post some pictures on the "Evil Twins".

They’re just of the workbench and in final form except for amounts of fibre fill.

I have to do some testing to see where I come out.

My first impression is that YOU CANNOT HAVE TO MUCH POWER with these things. I tried my UREI 6230 amps and they started clipping immediately. Even when bridged.

Since the other SUB1500 thread got ridiculously long, I propose that all cabinets for the SUB1500 be posted in this thread.

Best regards

//Robert

....Bah...why use crown,urei or other average amps when you could just cut to the chase and for about the same money obtain an above average amplifier, the Crest CA 18 is a hell of an amp...although its not always about wattage these amps provide plenty-950 into 8 ohms, 1700 into 4 and an easy 2400 watts into 2 ohms-this is each channel @ 20-20 khz with less then 0.1%thd+N ... bridged into 4 ohms you're talking about 4,800 actual watts--of course it can draw up to 36 amperes of current from your homes electrical service but lets face it-real power requires "real power", the typical switching power supply amps out there are nice and work pretty well but if you are adament about quality of low frequency these just don't cut it.The CA-18 also has an excellent damping factor and a frequency response that dosen't reach its 3db down point until 150 Khz (at 20-20khz they are extremly flat) These amps are built to work fine in the hellish conditions of extreme heat,humidity,incompetent audio techs and of course dead shorts, In a "clean environment" such as a climate controlled home I can't see why they wouldn't last half a century or more, of course as with anything there are always a few drawbacks...as mentioned you might want to upgrade the outlet used by this amp to at least a 30 amp circuit (higher if possible)...there is also the fan noise to contend with (although not to bad) and of course you'd need a pretty sturdy support surface or rack due to the amps almost 80 lbs of bulk--this really is not too bad when you consider the mighty Crest 10001 which weighs in at about 140 lbs and will put 10,000 watts into a one ohm load all night (20-20khz, 0.1%THD+N)...but thats another story.
PS- Those are Beautiful cabinets-very impressed by the quality.