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Gordon Steadman
12-07-2015, 10:16
There is a thread on DIY Audio that talks about the old B&O idea of having an additional midrange filling in between the normal two way speaker, leaving the crossover as usual.

As I am in a playing mood, I though I'd see if there was anything to the idea. Being me, it has to be a very simple way of doing it so I just stuck a spare pair of 5" midranges onto open baffles and wired them in series to my old bitsas. These have a Chinese 12", Celestion HF1300 and KEF T27 as supertweeter. I have always felt that asking as 12" to adequately cover the midrange a big ask - this includes (gasp) certain rather popular big dual concentrics.

I have just been listening to some Paco Pena Flamenco and the Bacarisse Guitar Concerto. Stunning clarity now in the mid range whilst keeping the depth and crispness. Thoroughly enjoyed it. They are only driven by a NAD 7020 so it will be fun to try some better amplification too.

Definite possibilities here. I am tempted to try putting all the units on an open baffle and seeing how it works out. As a lover of the Quad ESL, I have always found boxes, no matter how good, to have a certain sound to them that doesn't quite gel for me. The baffles will probably have to be the same size as the Quads to get bass without any equalisation but we will see what we will see and hear. Gilbert Briggs back in the 60's used to reckon open baffles were some of the best he had heard. Nothing new huh?
https://farm1.staticflickr.com/433/19437259700_22f2ee646c_z.jpg

PaulStewart
12-07-2015, 10:46
Back in the late 70s I built a system using a 2way open baffle with a free running mid with an l-pad to control the mid level. I used Audax units, 8 inch bass, 4.5 mid and 1 inch silk dome tweeter, the whole lot was driven by a pair of Alex Shackman modded Quad 11s. The clarity was stunning, turning down the mid level till you wern't aware of it as a source on it's own was one of the best SQs I had heard up till then. The problem for me was the baffle size I was using meant the bass was lighter than I liked. I solved this by making a mono sub using 2 12" Goodmans units isobarically loaded and driven by a Phase Linear mono amp.

As you said Gordon, Gilbert Briggs did it much earlier, and this lash up was bassed on ideas from one of his books. The best way to get rid of the box sound is as you suggest, get rid of the box, much as I love the Tannoy/Lockwoods, I miss the various electrostatics and open baffles I have had over the years. FWIW the system above was bought by Mike Craig, one of the DJs at Cavern Club (yes the one in Liverpool), as far as I know he still uses it at home.

walpurgis
12-07-2015, 10:56
I wonder if anybody here uses Tannoy duals on open baffles? I'd expect a pair of early Golds to work well enough or even IIILZs could be OK.

PaulStewart
12-07-2015, 12:59
I wonder if anybody here uses Tannoy duals on open baffles? I'd expect a pair of early Golds to work well enough or even IIILZs could be OK.

In the 60s a mate of my dad had a single 15" Red on a 4' x 5' curved open baffle driven by a Quad 1 and the original Accoustical mono pre. A 301 grease bearing/Decca arm and pickup were the main front end. Sounded pretty bloody awesome

Barry
16-07-2015, 18:29
In the 60s a mate of my dad had a single 15" Red on a 4' x 5' curved open baffle driven by a Quad 1 and the original Accoustical mono pre. A 301 grease bearing/Decca arm and pickup were the main front end. Sounded pretty bloody awesome

I can well believe it. Not sure though if a pair would work quite so well for stereo.

Reffc
19-07-2015, 10:32
There is a thread on DIY Audio that talks about the old B&O idea of having an additional midrange filling in between the normal two way speaker, leaving the crossover as usual.

As I am in a playing mood, I though I'd see if there was anything to the idea. Being me, it has to be a very simple way of doing it so I just stuck a spare pair of 5" midranges onto open baffles and wired them in series to my old bitsas. These have a Chinese 12", Celestion HF1300 and KEF T27 as supertweeter. I have always felt that asking as 12" to adequately cover the midrange a big ask - this includes (gasp) certain rather popular big dual concentrics.

I have just been listening to some Paco Pena Flamenco and the Bacarisse Guitar Concerto. Stunning clarity now in the mid range whilst keeping the depth and crispness. Thoroughly enjoyed it. They are only driven by a NAD 7020 so it will be fun to try some better amplification too.

Definite possibilities here. I am tempted to try putting all the units on an open baffle and seeing how it works out. As a lover of the Quad ESL, I have always found boxes, no matter how good, to have a certain sound to them that doesn't quite gel for me. The baffles will probably have to be the same size as the Quads to get bass without any equalisation but we will see what we will see and hear. Gilbert Briggs back in the 60's used to reckon open baffles were some of the best he had heard. Nothing new huh?
https://farm1.staticflickr.com/433/19437259700_22f2ee646c_z.jpg


One issue I can think of Gordon is that it could well mess up phase response, and will have "interesting" field lobing effects placed where it is too, especially due to the distance between tweeter and mid centres. How are you determining the blending...by ear?

Gordon Steadman
19-07-2015, 11:48
One issue I can think of Gordon is that it could well mess up phase response, and will have "interesting" field lobing effects placed where it is too, especially due to the distance between tweeter and mid centres. How are you determining the blending...by ear?

My ears and some guesswork is all I have!! As far as blending is concerned there is no adjustment as it's all just wired together to see how it sounds. The results make me want to do it properly so the next stage is a big open baffle a la Gilbert Briggs, about the size of the ESL57s with the mid range in a more conventional place. I might even do the tweeters facing up as Briggs suggests.

The joy of lack of knowledge is that I have no pre conceived ideas about right and wrong:D

Firebottle
19-07-2015, 11:57
The Joy Of Lack Of Knowledge :scratch:

Liking it Gordon :cool:

Gordon Steadman
19-07-2015, 12:16
The Joy Of Lack Of Knowledge :scratch:

Liking it Gordon :cool:
:lol:

Knowledge can come from experimentation as well as education. Someone had to do it first:)

I didn't get where I am today................

Reffc
19-07-2015, 15:55
There's no doubt that a good OB done properly can make for a very impressive sounding loudspeaker, so best of luck with it. Knowledge and experience does not have to imply preconceptions by the way. Such thinking in itself can be viewed as narrow mindedness of a sort often levelled at those with that knowledge and experience :lol: Knowledge can allow for a more guided approach of course which is the other way of looking at it. People only tend to impose the constraints against their own goals imparted by their own limits and preconceptions, and not by those of others :cool: At least that's the way I view things. Limits can always be unshackled and are rarely fixed in life. There's little new in loudspeaker design that wasn't known about decades ago, hence the knowledge is there, ready for the tapping. Briggs is an excellent source for that tapping.

Gordon Steadman
19-07-2015, 16:09
There's no doubt that a good OB done properly can make for a very impressive sounding loudspeaker, so best of luck with it. Knowledge and experience does not have to imply preconceptions by the way. Such thinking in itself can be viewed as narrow mindedness of a sort often levelled at those with that knowledge and experience :lol: Knowledge can allow for a more guided approach of course which is the other way of looking at it. People only tend to impose the constraints against their own goals imparted by their own limits and preconceptions, and not by those of others :cool: At least that's the way I view things. Limits can always be unshackled and are rarely fixed in life. There's little new in loudspeaker design that wasn't known about decades ago, hence the knowledge is there, ready for the tapping. Briggs is an excellent source for that tapping.

All agreed. You mustn't take anything I say too seriously. Nobody else does:lol:

However, I have always been a suck it and see type of man. My first guitar should have been a Torres copy but I did it my way and have stuck to that ever since with just a few refinements. As far as loudspeakers are concerned, I have the constant reference of the Quads to compare to. The little KEFs with the LS35a metal grilles and felts come closest. I don't expect my bitsas to get that close but it is fun just trying stuff anyway.

I have never liked buying things that I could make myself but my brother stole all the electrickery genes the family (he designed rocket guidance systems) had so I find the whole area a total blank. I'll stick to woodwork.

Reffc
20-07-2015, 08:17
All agreed. You mustn't take anything I say too seriously. Nobody else does:lol:

However, I have always been a suck it and see type of man. My first guitar should have been a Torres copy but I did it my way and have stuck to that ever since with just a few refinements. As far as loudspeakers are concerned, I have the constant reference of the Quads to compare to. The little KEFs with the LS35a metal grilles and felts come closest. I don't expect my bitsas to get that close but it is fun just trying stuff anyway.

I have never liked buying things that I could make myself but my brother stole all the electrickery genes the family (he designed rocket guidance systems) had so I find the whole area a total blank. I'll stick to woodwork.

Funnily enough, I've just finished reading some articles written by Briggs on OB design V's sealed and reflex designs and whilst dated, his observations stand, however limited in absolute detail. When Briggs was writing his books back in the day, there was an abundance of 15, 12 and 10 inch woofers to choose from with the suitable parameters for sealed box use...the shame of it today is that they are few and far between. I laughed at his comments regarding matching cabinet and cone resonances for a ported enclosure using a 12 inch woofer...he says "...It is a fruitless exercise as something the size of a telephone box would be required".

One clever experiment resulting in very good corner speakers was simply to make them from a flat baffle placed across the brick wall corners of the room with a top added. Genius.

Quads remain a decent reference Gordon, I'm with you there.

Barry
20-07-2015, 11:34
My first encounter with hi-fi was experiencing the system the father of a school chum of mine had. It used a pair of Wharfedale SFB3 speakers.

https://sp.yimg.com/ib/th?id=JN.DljV%2bz1tiRnKWVcvJDMeXQ&pid=15.1&P=0 https://sp.yimg.com/ib/th?id=JN.vpByYLMyQT%2f3xo3R7PmeBg&pid=15.1&H=252&W=160&P=0

SFB stood for 'sand filled baffle'. The design largely consisted of a 12" woofer and an 10" midrange unit mounted on an open baffle, consisting of two sheets of plywood (?) separated by about an inch, with dry sand filling the gap. The baffle was about the same size and area as that of the Quad 57. There were two side panels to give the speaker some stability and to allow it sit on the floor. A 3" tweeter firing upwards was mounted on a top panel, though I don't think this was sand filled.

https://sp.yimg.com/ib/th?id=JN.cBPY5p1U4FBpG%2bPKX3nz1A&pid=15.1&H=153&W=160&P=0

http://www.inner-magazines.com/news/28/72/Whaferdale-SFB3/

They were driven by a Leak Stereo 20 valve pre and power combination, with the front end being a Shure M44E in a Garrard SP25. It was all very impressive to a 16 - 17 old boy.

I believe the SFB3s are now keenly sort after by Japanese enthusiasts.

walpurgis
20-07-2015, 11:36
Apart from the TT that would have been a prestige system back then.

struth
20-07-2015, 11:40
be interesting to make a set of these speakers with modern parts and see how well it works nowadays

Barry
20-07-2015, 11:56
The 12" and 10" drivers were wired in parallel (presumably they were both 15 Ohm impedance) and the 3" tweeter was driven via a 4uF capacitor.