Open Baffleless

[Ali Tait]

I had the opportunity to visit Vic of Trans-Fi fame the other night to have a listen to his OB's,which I'd discovered whilst having a mooch around the net looking for info on my Bastanis. Thanks are due for hosting me and allowing me to listen to his creations - thanks Vic!

Short version - Wow. Just wow..

Long version - Vic took me upstairs to his living room, quite a large space, around 30ft. by 15ft. so room for speakers to breathe. We had a chat about the construction of the speakers and the various earlier iterations that are scattered around the room. Some photos below, but basically he uses some miniature scaffolding parts from a company near Huddersfield I think it is - total cost for all the parts and for them to cut the tubing to length was £99 delivered, so a bit of a bargain there. I'll try and find a link. The bass drivers are bolted together facing each other using some spacers of around 4-5", and hang in a cradle of the scaffolding supported by some small loops of cable. This seems to work really well - I checked to see if any vibrations were making there way from the drivers to the scaffolding and couldn't really detect anything, so this arrangement appears to work really well. The PRV mid/top drivers are hung from a U shape bracket, again with a loop of cable under the top drivers' magnet. Vic made some fish plates, more or less the shape of a dog bone to connect the four drivers together, all just hanging there from the top driver. The weight of the drivers keeps them steady. They are connected series/parallel a la Edingdale stylee.

It was all digital files we listened to, one particular track that struck me was a live version of Man/Machine. I can honestly say I've never heard a speaker in a living room get closer to how a live gig sounds ( or at least how I imagine it would sound not having been there). The scale, dynamics and sheer drive to the bass has to be heard to be believed - I've certainly never heard anything like it in a living room, it really is like being at the gig. The funny thing is though, the bass is in no way overblown, nor does it interfere with the mid/tops in any way, it's just there when it needs to be, and boy is it there! As Vic commented, you can't really appreciate music like this until you hear it with the full frequency range reproduced, and having now heard this for myself, I have to agree.

The 4" PRV drivers appear to be quite a bargain- I think they are around £75 each?

Mids and tops were very well reproduced, huge soundstaging too. Very clean and clear, and I didn't miss a tweeter at all.

Further details - The bass drivers are Dayton Audio UM18, crossed at 275hz to suit the PRV drivers, using the DSP in the Behringer amps. I was surprised to learn there is no DSP used to tweak the low bass response due to the lack of baffle, these drivers are so capable that none is required - I can certainly vouch for that. Only caveat is sensitivity is not great, but as Vic again commented, watts are cheap - he's using a couple of 6000w NX Series Behringers which he paid £300 each- all he does is up the gain by 10db to match levels with the PRV's. Other than that they are run open, as I believe are the PRV's - they are run with a pair of Temple Audio boards, powered with a pair of supercap power supplies.

Well that's about it, just like to say thanks again to Vic, it was a pleasure to meet you. My plan now is to copy the bass side of this and use it with the Bastanis mid and tweeter.

https://i.imgur.com/223oAwZ.jpg

https://i.imgur.com/Dlwg18W.jpg

https://i.imgur.com/KW8Gf3T.jpg

https://i.imgur.com/nohGUnq.jpg

https://i.imgur.com/KW8Gf3T.jpgEDIT - link to the metal store - https://www.themetalstore.co.uk/

[hificricketboy]

Thanks for the write up.

They look a bit industrial for someone's lounge but look interesting as well. No chance my wife would accept something like that!

There's been a pair of baffleless speakers on eBay for a while which always catch my eye on my feed. I think they had bigger bass drivers from memory. Is Vic commercialising them?

I quite fancied a play with the Bastani open baffles but my wife thinks they look like toilet seats :rolleyes:

[ToTo Man]

Excuse the pun, but I'm baffled as to how anything remotely resembling a typical house curve frequency response (-10dB slope between 20Hz and 20kHz) can be achieved, without EQ to apply an inverse gain curve to counteract LF roll-off from using the bass drivers open baffle. Unless the face-to-face arrangement prevents the rear-wave from being cancelled? Is that how it works? I'd love to hear that setup!

[Ali Tait]

You have to hear these, it’s hard to describe how good the bass is.

There is some EQ, Vic has it tailored to give more bass at low volumes. The huge Xmax and power handling go a long way to compensate for the lack of baffle. Theory may say this doesn’t work, but I can categorically say these produce the best domestic bass I’ve ever heard from a speaker.

[drSM]

OMG looks bloody amazing . I am sure those twin 18'' woofers per side will do the business.
No baffle even. Baffling !

[paulf-2007]

That tubing and fittings are not scaffolding, they are used for handrails on steel platforms, stairs and balconies.

[Pharos]

I think it may be "Key Clamp" tubing.

[Halfway Tree]

Thanks for posting this Ali. Fascinating build. The bass arrangement reminds me of Celestion's SL6000.

http://www.audiodesignguide.com/doc/cel6000.jpg

[Made in 1968]

I remember the review using those '6000' Dipole subs with Quad '63' stats

[Ali Tait]

Aye me too, these put me in mind of them. Never heard any though.

[Barry]

I remember the review using those '6000' Dipole subs with Quad '63' stats

That set up was used by Noel Keywood, so you probably read about it in HiFi World.

[Halfway Tree]

Aye me too, these put me in mind of them. Never heard any though.

No, me neither.

Perhaps you could persuade him to bring these to NEBO? :)

[Made in 1968]

That set up was used by Noel Keywood, so you probably read about it in HiFi World.

No it was before Hi-Fi World. I remember the subs being in Flight Cases..

[Barry]

Are the two bass drivers fed in phase or in anti-phase? By in phase, I mean the two drivers move towards one another, squeezing the air between them and pushing it out the sides.

[Made in 1968]

In phase would be Bi-pole out of phase Di-pole..

[Barry]

Yes I know that, but I'm trying to work out how these 'baffleless' designs work and not suffer from wave cancellation. :scratch:

[Ali Tait]

No, me neither.

Perhaps you could persuade him to bring these to NEBO? :)

I tried. He was not keen, understandably so, the bass drivers alone are 80kg..

[Patrick Dixon]

Yes I know that, but I'm trying to work out how these 'baffleless' designs work and not suffer from wave cancellation. :scratch:

Fill yer boots - https://www.lencoheaven.net/forum/index.php?topic=31371.0


"In the next iteration I placed the woofers facing each other, simply because they were easier to mount as previously the rear speaker required longe standoffs to clear the frame. In this configuration, BTW, I had to reverse the polarity on one of the woofers to keep them acoustically in phase:"

[Ali Tait]

Are the two bass drivers fed in phase or in anti-phase? By in phase, I mean the two drivers move towards one another, squeezing the air between them and pushing it out the sides.

Out of phase electrically Barry, so the cones work in tandem.

[ToTo Man]

Fill yer boots - https://www.lencoheaven.net/forum/index.php?topic=31371.0


"In the next iteration I placed the woofers facing each other, simply because they were easier to mount as previously the rear speaker required longe standoffs to clear the frame. In this configuration, BTW, I had to reverse the polarity on one of the woofers to keep them acoustically in phase:"


Out of phase electrically Barry, so the cones work in tandem.

I'm not sure I'm any the wiser. Are both woofers wired in anti-phase, or just one? If just one then you'd expect almost complete cancelation to occur in the space between the two woofers?

EDIT - Thinking about it more, working in tandem probably does need one wired in anti-phase, so that the two drivers 'suck' and 'blow' in the same lateral direction and not against each other.

[Ali Tait]

Yes one wired out of phase with respect to the other, so that the cones both move in the same direction.

Yes you would expect cancellation in theory, but that's not what you get. I've never heard bass like it from a domestic loudspeaker.

[struth]

a push/pull arrangement i'd guess

[Ali Tait]

Yep

[Lawrence001]

I was thinking ordinarily it would be push push in a bellows type arrangement (like some Kef Reference models) but it's complicated by the open baffle situation. Why would this not work whereas a push pull would?

[Ali Tait]

There is no baffle though.

[Barry]

So if a cabinet were used, the arrangement would be called 'isobaric' (i.e. constant pressure between the two drivers).

[struth]

So if a cabinet were used, the arrangement would be called 'isobaric' (i.e. constant pressure between the two drivers).Think the space between drivers has to be sealed to be isobaric

[Barry]

Think the space between drivers has to be sealed to be isobaric

Yes, that is what I meant - as in the Linn Isobaraks.

[Ali Tait]

Yes same idea, just without the baffle.

[Halfway Tree]

I tried. He was not keen, understandably so, the bass drivers alone are 80kg..

Completely understand, Ali.

Still trying to get my head around how these work without a fair bit of EQ, though. I imagine there is some reinforcement from the floor perhaps....but still, has me puzzled.

With a V-shaped baffle, which does reduce vibration considerably and 20db of lift my LX521s will get to 96dB @30Hz (about 26mm excursion) so nowhere near what these seem to be capable of.

[Ali Tait]

There is some EQ Gordon, and he also adds about 10db I think of gain to match the small drivers. He's using 6000w on the woofers so no shortage of power, and the drivers can take 1000w RMS. The trick of hanging the drivers with some steel cable is a clever one and really contributes to the sound I think.

[paulf-2007]

Yes one wired out of phase with respect to the other, so that the cones both move in the same direction.

Yes you would expect cancellation in theory, but that's not what you get. I've never heard bass like it from a domestic loudspeaker.
In what way, more powerful bass or deeper bass or more detailed or more realistic bass. I know it's sometimes difficult to describe. Like my Lii audio crystal 10 now being driven by a Bakoon 11R, deeper bass but more importantly what I would describe as more detailed across the frequencies, the old " hearing detail I've not heard before " on familiar music.