Cheap Version of the famous Tysen speaker.

[chris661]

You can read the discussion of the Tysen speaker on this thread:

A thread for Tysen and variations on FAST

But I decided, instead of putting my project completely onto that thread, I should start my own.

Anyway, onto the project.

Seems appropriate that I start woth driver choice, so I will.

The FR driver is a Visaton FRS8 - these are (in terms of price to performance), fantastic speakers, which sacrifice (seemingly) sensitivity for a smooth run from 120Hz upwards (small, sealed box), with the only dip between 15kHz and 20kHz. With these speakers, cymbals sound metallic, you can hear the sound of fingers picking at guitar strings, and stereo imaging is the best I've heard (I haven't heard Mega Systems, but I've heard good ones), however, the only thing that lets these speakers down is the bass. Now, trying to integrate them with my subwoofer wasn't particularly easy when I attempted, so I looked at other ways of making bass. The idea of a FR driver with some kind of bass unit has always appealed to me, as the XO point is away from the sensitive area (3kHz), so you get the advantage of a FR driver, but with the bass of a larger, 3-way system, which brings us neatly onto the woofer.

I wanted something small (less than 8"), and cheap, but still went pretty low. After looking at various 6"+ Visaton woofers, I arrived at the W130S 8ohm, which models pretty well in a 17L box, tuned to 46Hz, and costs less than £10 each. Many of us know that cheap bass/mids often fall over on midrange if they model well (the manufacturer has to cut corners somewhere, right?), but the beauty of this design is that you can use even cheap aly drivers and avoid the ringing that is often associated with metal cones. So, bought two to make a test, make sure the go as low as winISD says, etc, and, lo and behold, they really go that low (f3 of 42Hz, f10 around 33Hz).

After discussing with Dave, it was decided that having two woofers push push, one on either side of the cabinet would be a good thing, as it would stop the whole speaker vibrating (a major thing for me, as I'm 15, so parents to please...), so, the (nearly) final design is as follows: 2x FRS8 and 2x W130S per cabinet, using a 20:1 MTL for the FR drivers, as the impedance spike at resonance is just one octave down on the XO point, and a 35.4L box (extensively braced) for the woofers.

Made one test box (just one woofer), and, after messing with phase issues etc, got a really nice sound out of it - better than expected. So, I need to make the other test box, then persuade Dad that they sound better than the Missions he lets me borrow (the old 760is), so he'll go and buy the other two.

The final cost for this design is less than £150, so it's ideal for people who are new to this, and those who want to try a new kind of speaker, without spending a fortune.

Thanks for reading, pics attached - please note - this is a test box, made of an old 3-way speaker. The cut outs are very rough, so no nasty comments on workmanship, please

[planet10]

Excellent... when you build the real boxes make sure you champher the back of the FR8 cutout,

dave

[chris661]

Last night (after posting the above), I made the other test box aswell, set them up with a half-decent 50W amp, plugged into a CD player.

For the driver size, the amount of bass and volume is surprising, but I suspect there's a reason...

Most bass drums are recorded around the 40hz region, and that's where the port is tuned. I can go to 200W around port tuning and the driver is still withing Xmax, but I suspect I'd hit thermal ratings first.

Anyway, listening to those speakers, the whole concept of a low crossover and a woofer to back up a FR driver does make sense. For those who want to try it, I'd suggest you go for it - it is hugely rewarding.

Good luck!

Chris

[rcavictim]

What about LF cabinet pressure modulation from the woofers working on the backs of the small front full range drivers??????

[901Fixer]

Originally Posted by rcavictim

What about LF cabinet pressure modulation from the woofers working on the backs of the small front full range drivers??????

It looks like the FR driver will be in a 20:1 MTL eventually. Will both drivers be in the same space or have their own, Chris?
The build looks great, I love the cost effective approach to your experimentation, surely Dad will agree and spring for the rest of the project.

What is your next project gonna be?

[chris661]

I just came to ask a question on the effect of the impedance peak, but I'll answer yours first.

1) Yes, the pressure from the woofer does move the FR drivers a little, but the Qms is high enough to keep that minimal.

2) The FR drivers will probably be in the same space (Dave used a 10:1 for one driver, so 20:1 for both sounds about right), as creating two MTLs one on top of the other would result in a more difficult build...

3) After this, who knows? I'm looking towards something that will give 2x100W of clean power (>1%THD at 100W kinda thing), that still sounds good. Apart from that, possibly a centre channel, maybe a pair of rear effects speakers (currently using a pair of cheapy bookshelf speakers). Talking of which, I have some Wharfedale speakers lying around........ Back on topic.

My question is this - will the 30 ohm speak at 150Hz affect the crossover a huge amount? I could make an MTL, but if the effect of it will be minimal, I could keep a small, sealed box instead. From what I can see on winISD, the impedance peak makes the roll-off steeper lower than the peak. This wouldn't be a particularly bad thing, as far as I can see.

Chris

[901Fixer]

Originally Posted by chris661

2) The FR drivers will probably be in the same space (Dave used a 10:1 for one driver, so 20:1 for both sounds about right), as creating two MTLs one on top of the other would result in a more difficult build...

My question is this - will the 30 ohm speak at 150Hz affect the crossover a huge amount? I could make an MTL, but if the effect of it will be minimal, I could keep a small, sealed box instead. From what I can see on winISD, the impedance peak makes the roll-off steeper lower than the peak. This wouldn't be a particularly bad thing, as far as I can see.

Chris

You are 15 years old, don't build the simplest enclosure, those are for old folks with miserable jobs and a family to support so there is no time for anything else. If the FR pair will work fine together in one MTL then thats what I'd do but if it would be better with each in its own then embrace the challenge, doesn't sound like you are skeerd to use your imagination. You might could build one 20:1 MTL enclosure with the option of installing a panel inbetween so as to experiment with each in its own then you'd know for sure.

[planet10]

Originally Posted by chris661

My question is this - will the 30 ohm speak at 150Hz affect the crossover a huge amount? I could make an MTL, but if the effect of it will be minimal, I could keep a small, sealed box instead.

Yes, the impedance peak will affect the XO. As can be seen from the impedance plot of FF85 in free air vrs the "aperiodic" midrange TL loading in Tysen, the box has a dramatic effect on impedance (note that no optimization has been done on the line since we went active)



dave

[chrisb]

Originally Posted by chris661

I just came to ask a question on the effect of the impedance peak, but I'll answer yours first.

1) Yes, the pressure from the woofer does move the FR drivers a little, but the Qms is high enough to keep that minimal.



Chris

Actually, even if that were the case, I think what Bob is concerned about would be IM distortion from the back wave bleeding through the FR cones due to their open back. If all drivers were running full range or on an open baffle, this probably would be much less of a concern.

[brig001]

Originally Posted by 901Fixer

...surely Dad will agree and spring for the rest of the project...

Oh no he won't.
But he might help at tool time.

Chris's dad.