Which speakers can the Crack drive?

[free]

Hi,
I understand that the Crack is a headphone amp, but since I cannot afford the S.E.X. and others and don't want to turn up the HD600 and misuse them for speakers and in maybe destroying them, I'm wondering which speakers the Crack can drive? I guess there's no list of speakers for the Crack, so how do I know which speakers are ok for the Crack?
Crack has 300mW output, S.E.X 2000mW?, so having smaller speakers because of that is ok.

edit:
Which speakers for classical music for the Crack would you suggest?

 

[Zimmer64]

I am not an expert, but I believe you would need to add output transformers for better impedance matching.

I guess others will chime in.

Best

Michael

 

[Paul Joppa]

Yes, you need a transformer to match the 4- or 8-ohm speaker to the 500-600 ohm impedance (which gets the most power from Crack). The most affordable transformers are called "line matching" and are typically used for small distributed sound systems such as the muzak in my chiropractor's office.

They come in 25-volt and 70-volt versions; for 25 volts look for a 1-watt tap, and a 10-watt tap if it's 70 volts. They should cost less than $10 each. Bigger is better, I'd look for at least a half pound.

 

[Paul Birkeland]

so how do I know which speakers are ok for the Crack?
Crack has 300mW output, S.E.X 2000mW?, so having smaller speakers because of that is ok.

Yes, the Crack will make a 1/3 of a Watt into higher impedances.  I'd expect less than half that if you use 600:8 Ohm transformer. 

So, I guess the question is - are there speakers that will run to reasonable listening levels with 1/3 of a Watt?

I believe there are, but generally you could buy 10-100 SEX amps for what they cost.

 

[free]

Thanks.

Yes, you need a transformer to match the 4- or 8-ohm speaker to the 500-600 ohm impedance (which gets the most power from Crack). ...

Sorry I'm newbie, do you mean I have to replace the original transformer from the Crack with another transformer?
--
The Crack delivers 0.3W to ~250Ohm (headphone) speakers? So I thought it then can deliver: 250:2:2:2:2:2, 5 divisions => 0.3*2^5 = ~10W speakers with 8ohm or ~20W with speakers with 4ohm? But I guess I'm wrong here.

Any 10-20Watt speakers the Crack can run without modifying the Crack? I don't to drive big speakers, something like this with 1/2 or 1/3 the wattage would be fine (so really 10-30Watt speakers).

 

[Paul Birkeland]

The Crack has a power transformer, and no output transformers (OTL is output transformer-less).

The division rule you're applying works the other way, and on solid state amps.  (100 Watts into 8 Ohms -> 50 Watts into 4 Ohms)

We can generally get 10V of swing pretty easily on the Crack.  If we use a 600:8 Ohm output transformer, that offers roughly a 9:1 step-down ratio.  That leaves you with about 1V across an 8 Ohm speaker, which won't give you much satisfaction. 


Now, if you have the true DIY spirit pumping through your veins, you would ask the question, "Can I build a pair of speakers to run off the Crack?"

The answer to this question is yes!  I believe if you made a 600 Ohm speaker of high efficiency, the Crack would provide a reasonable amount of output for near-field listening.  This would be 38 - 16 Ohm drivers per side, which is still horrendously more expensive than a SEX amp.  Do note that if you go to a 1200 Ohm speaker, you'd get even more power

 

[free]

Thanks. S.E.X. amp delivers 6,67 times more output, how can it be so much better? Can SEX drive any speakers? Is it OTL or works it somehow differently to be able to drive 8 or 4ohm speakers then? If SEX is for big/any speakers, then Crack must be able to run 10-30W near-field speakers.

Do note that if you go to a 1200 Ohm speaker, you'd get even more power.

That's interesting, because usually I see only 4 or 8ohm speakers.
Wired this.

 

[Paul Birkeland]

Thanks. S.E.X. amp delivers 6,67 times more output, how can it be so much better? Can SEX drive any speakers? Is it OTL or works it somehow differently to be able to drive 8 or 4ohm speakers then? If SEX is for big/any speakers, then Crack must be able to run 10-30W near-field speakers.

You are comparing an amplifier designed and optimized for an output transformer/speakers (the SEX amp)to one that was never intended to operate with either (the Crack).  The SEX will make 2 Watts into a variety of impedances. The Crack will not make 2 Watts into any impedance, and its power output varies considerably with the load impedance presented.

At 8 Ohms, as I said, you get about 1/8 of a Watt through a 600:8 transformer.  The 2 Watts of the SEX amp are then 16 times more powerful. 

 

[free]

Ok.

It would be nice if there would be a kit for the Crack so it can drive the typical 4ohm and/or 8ohm speakers too. I'd be happy if it could drive 10-30W speakers then. I like how the Crack is smaller, (less expensive) and looks better. +$100 for the kit would be ok. S.E.X. is too expensive for so many people and Crack has the biggest community.
S.E.X. has different transformers, I guess the middle one is for headphones and the side ones are for speakers, so in the end I would have to replace the original transformer of the Crack to drive some low impedance speakers? This is unfortunately not an option for me and my Crack  ;D Thanks anyway for the great Crack 

Grainger49,
Yes, more watt than input cannot come from output, otherwise we wouldn't have any energies problems  (so the low impedance speakers would only be 2*150V*0.035mA=10.5W which would be I guess still enough for me)

 

[Mike B]

Crack is only going to output one third of a watt no matter what you do.

It's not designed to drive speakers.

You would be better served getting a small SS amp like this;

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-380

And connecting the Crack output to it.  That will drive speakers.

 

[free]

Crack is only going to output one third of a watt no matter what you do.

It's not designed to drive speakers.

Ok

That would be a SEX amp.

Yes I know, that's the whole point of this topic

The impedance is impossible with the power the Crack produces and the impedance it needs connected to it.

This is sad to hear so no $100 kit for the most popular Bottlehead product :\

 

[PassionForSound]

The impedance is impossible with the power the Crack produces and the impedance it needs connected to it.

This is sad to hear so no $100 kit for the most popular Bottlehead product :\

This is said politely and is not intended to upset: I think you're missing the point here. The Bottlehead kits are priced so well because they are designed to be simple and are focussed on certain uses in order to keep them simple and the price down. My guess is that the kit required to DIY a modification for the Crack to drive speakers would very quickly bring the price up to something near the S.E.X.

By the time you fiddle around with add-ons for the Crack, making it more expensive and probably an ugly mess of cables, it would be better to go with the S.E.X. in the first place.

I understand your points about the price and size, etc. but you're asking a deliberately simple, low-priced, specifically designed amplifier to become so much more (electronically speaking). That would defeat the purpose of it's simplicity and purity as a high impedance headphone amp and it would then no longer be small and cheap.

 

[Paul Birkeland]

The impedance is impossible with the power the Crack produces and the impedance it needs connected to it.

This is sad to hear so no $100 kit for the most popular Bottlehead product :\
[/quote]

Having the Crack in the equation means you can remove the volume control from the SEX amp, nothing more, nothing less. 

You can buy a T-amp for under $50 that might meet your needs.

-PB

 

[free]

Ok. I just thought it would be possible for a bit cheaper than the S.E.X., but it's ok if not, S.E.X. is I guess still very well priced (just not as compact and nice looking as Crack in my opinion but still good looking).

You can buy a T-amp for under $50 that might meet your needs.

Do you mean a tube amp or this? If the latter, it's by far not as nice looking as the S.E.X.
--
If the S.E.X. puts out 2Watt, how can it power 100W speakers then? I guess it would need something else?

 

[PassionForSound]

You need to buy speakers with high sensitivity >90dB (recommended is 97dB I think)

There are a number of DIY kits that come close (using drivers like the Fostex 3" / 4" full range) and some of them are listed on the S.E.X. page in the Bottlehead store. There are also suggestions of pre-built speakers like the Blumenstein Orcas.

In other words, the S.E.X. won't rock with cheap bookshelf speakers from your local budget hi-fi store. It will sound OK with them, but (in my experience) the bass is a bit lean if the speakers aren't sensitive enough.

 

[free]

The Blumenstein Orcas is $800 which is way too expensive for me but look very nice with the wooden case.
They use Fostex driver.
Any other wooden ~$100-$200 speaker(s)? A FE83En isn't that much expensive by itself ($40). Maybe there is a pre-build good looking wooden speaker for like 100$ (max. $200 per speaker)?

edit:
Oh and it's not 90dB/W, nor 97dB/W but only 88. Is this enough?

 

[travisty]

Is this (88dB) enough?

No. Not really. Though again it could depend on the impedance of the speakers, the amp, and the music you listen to (string quartet chamber music might be possible, rock with any kind of bass and the answer may be no.

Efficient speakers are not (in my opinion) 90dB or better but more like 96-97dB or better. And even then, the quality of the bass can suffer if you don't have enough power (or damping factor) as bass simply can suck the life out of an amp - really strong good bass requires significant control of a large moving object. At 88dB and the S.E.X., string quartets might be possible but most movie soundtracks would be impossible to do well.

More efficient speakers require larger size. Larger size requires, at its most base case, more material to cover the outside of a larger internal volume, and often more consideration for bracing due to the greater flexibility created by larger surfaces. At the most basic level, more material requires more money. It can also require more work/time to do well, but if you DIY, it is a matter of materials (and plans). If you really want to go down the inexpensive DIY route for efficient speakers and can get materials cheaply, you might try a Sachiko (search "Sachiko" in this forum) or google "Sachiko speaker". They are quite efficient, by all accounts sound nice, and if you can get the material cheaply, shouldn't be that difficult to make.

 

[free]

Sachiko is just the case with still ~90dB Fostex drivers? How can it make the driver more sensitive?

This is fun: for the Crack I needed high impedance speakers (600,1200ohm). So now for the S.E.X. I have problems finding sensitive speakers? S.E.X. product page doesn't list too many speakers. Can you post some full range >=95dB speaker which you recommend?

 

[saildoctor]

FWIW - I use the Orca speakers with 45 output tubes (~2 watts) and get plenty of volume in the smallish room that I listen in.  I would only be worried about getting enough volume if you were going to set up in a really large room.

The reality is that tube amplifiers meant to power loudspeakers require heavy iron components (power transformers, plate chokes, and output transformers.) The output transformers are necessary to mate the high output impedance of the tube with the low impedance of the loudspeaker.  The Crack OTL (output transformer-less) amp is only as cheap as it is because it can dispense with the plate chokes and output transformers. It is intended only to power high impedance, low powered headphones.

If you look at most websites with $100-$200 dollar speakers you will notice that they are build with cheesy drivers and make no mention of what they're made of (particle board or cheap who knows what).  That's just how it is at that price point- the people selling them are not going to make something better with their labor and materials and sell them at a loss.  In other words you get what you pay for - to a point at least.  Good sounding equipment requires good design, good components, and good execution of the construction.  The beauty of Bottlehead products is that they take care of the first two ingredients and leave the third to the purchaser.  I'll give a big thumbs up to the value of Fostex drivers- you could try building your own cabinets and probably come away with something decent.  The SEX amp is a great product that you should seriously consider if you are interested in getting a high quality soundsystem - if you do some reading around this forum and the web you will read many testimonials that it's worth every penny. 

 

[Paul Birkeland]

This is the T-amp. 

Clark demos the Orcas with the SEX amp all the time (As do we in the office).  With a reasonable listening space, this is a very nice combination.

There are some inexpensive tube/FET hybrids available online as well.  I generally don't think too highly of these - they tend to either run way too much voltage across the FET's or not nearly enough voltage across the tube.