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Horn-Loaded Speakers
Topic: The "open baffle" means everything.

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Posted by manisandher on 05-16-2010

Thanks for all the suggestions. As it happens, there were no exhibitors at the Flemings Hotel this year. But I did pop into the Stax stall before listening to anything else.

In general, I was pretty disappointed with what I heard. Most of the ‘conventional’ direct-radiating speaker systems just sounded ‘dead’, at best – what I call ‘cardboard’ sound. Many sounded positively objectionable – and I’m talking about well known high-end brands here.

I did have one interesting experience though. I was walking down a corridor and heard something coming from around the corner that I thought sounded really good. I walked speedily down the corridor and turned the corner to the sight of a live acoustic band playing snare drums, double bass and guitar!

I have to say that absolutely none of the systems I heard came even close to this live sound. Could it be argued that this had much to do with bad rooms? Maybe. But it’s interesting that a live band can still sound ‘right’ from down a corridor and around a corner.

I have absolutely no desire to write negatively about anything that I heard. So here are a few systems that I had a positive experience with.

1948 Western Electric Theatre speakers
Driven by Silbatone A-845 mono amplifiers and C-100 preamplifier. 2-way system crossed at 800Hz.
Nice ‘alive’ sound. No real top or bottom to talk about though. Not sure how long I could listen to these – they seemed to have a bit of an edge to them.
Western Electric 1948.jpg

Stax SRM-007tII/4070 electrostatic headphones
Really nice. Probably my favourite sound at the show.

MBL 101 X-treme
Very sweet top end – one of the best I’ve ever heard. However, things got progressively worse further down the spectrum. The mid-range seemed thin. There seemed to be a lack of upper bass. The lower bass, although substantial enough, was totally disjointed. But what a top-end!

In summary, although I didn’t hear anything at the show that approached what I consider the ‘real McCoy’, I’m still really glad I went. When I returned, I listened to some music on my speakers and realised that I’m not doing too badly after all. Yes, I have ‘cardboard’ sound too. But mine is in no way objectionable - just a bit ‘lifeless’... but listenable nevertheless.

Mani.

Posted by Romy the Cat on 05-16-2010

Thanks, Mani. My comment is about the 1948 Western Electric I generally do not like those types of the speakers. There is a community of people who use those open baffles, insisting that they are the only speakers that decay 6bB per octave under the bottom. The absolutely fanatical about their Western Electric or Klangfilms or whatever and they are absolutely blind to many fundamental problems of the topology. Unfortunately the fetish that they created in own heard pretty much disqualifies them from an ability to endure any cretinism or even questioning.

The Cat

Posted by Markus on 05-17-2010
fiogf49gjkf0d These speakers were not open baffle. I would agree with Mani's description of their sound, except for the 'edge' bit. That depended on where you were sitting/standing.

Posted by KLegind on 05-17-2010

Markus wrote:
These speakers were not open baffle. I would agree with Mani's description of their sound, except for the 'edge' bit. That depended on where you were sitting/standing.

Then they would be baffle extenders which are not without problems. Perhaps a resonating panel can be used to tune the sound of the speaker, but in that case I would have used a set of large round-overs that would make the transition to 4pi space very gradual. Possibly integrating these into one large enclosure. Edge diffraction is not to be trifled with (in my experience).

kindly
Kris

Posted by el`Ol on 05-17-2010

manisandher wrote:
Thanks for all the suggestions. As it happens, there were no exhibitors at the Flemings Hotel this year. But I did pop into the Stax stall before listening to anything else.

The Hifi Deluxe was in the Le Meridien.

http://www.hifideluxe.de/

Would have been interesting what you think about the Duevel (and whether you like the MBL top end for being omnidirectional only).
Martion and Ecouton were around the corner as every year, the new Ecouton Transar seems to have a horn-loaded Mundorf AMT, would have been nice to hear it, the earlier Versions had ESS AMTs I think.
From what I have read in forums so far the only really interesting room for me would have been Audionec.

Posted by Romy the Cat on 05-17-2010

Markus wrote:
These speakers were not open baffle.

Actually they are. They might not look like open baffle but they have all negative conceptual characteristics of the open baffle. I think to properly evaluate what those type of the speakers they need to be viewed like nothing else then the open baffles. It was very popular design in that time for film theaters; there were many manufacturers who do the same….

The Cat

Posted by el`Ol on 05-17-2010
fiogf49gjkf0d Weren't these speakers (at least in Germany) normally used built-in (infinite baffle situation)? And I don't like the word "open baffle" because it can mean anything. It reaches from quasi-IB like proposed by PHY-HP up to that more and more crazy constructions at diyaudio.com that need massive boosting over the largest part of the frequency range.

Posted by Romy the Cat on 05-17-2010

el`Ol wrote:
Weren't these speakers (at least in Germany) normally used built-in (infinite baffle situation)? And I don't like the word "open baffle" because it can mean anything. It reaches from quasi-IB like proposed by PHY-HP up to that more and more crazy constructions at diyaudio.com that need massive boosting over the largest part of the frequency range.

I disagree. The "open baffle" term means very specific and very definitive thing. It means that baffle is finite and it has a frequency where the dipole acoustic shortage kicks in. that is the whole point of baffle to be limited/finite in a contrary to infinite baffle where the back way never see front wave.

The infinite baffle and open baffle VERY different topologies conceptually. It is like US Space Shuttle vs. Russian Space Shuttle – both are very same aircrafts but they operate on very different fundamental principles. I do not know how these speakers were used in Germany. If they were built-in to the walls of the theaters then the large front baffle is necessary but I think that were used in stand-alone configuration (Klangfilm Eurodyn or Bionor) as they are used today by their admirers.

The Cat

Posted by Joe Roberts on 05-17-2010

The Western Electric L-9 in Munich was/is an infinite baffle design. The 754B woofers are in a sealed enclosure with a front horn. There is no possibility of cancellation between front wave and back wave of speaker, so I wouldn't call it an "open baffle" in any way. Don't be fooled by the wings.

We were always clear to point out that this is a "second class" WE theater speaker. The Alnico components are quite good (although I am suspicious of the cast aluminum KS-12025 horn). The HF driver was the phenolic 713 good to 13k which sounds better (smoother) than the aluminum diaphragm version. The earlier field coil stuff is in another league entirely but this system is very interesting.

The goal was to provide something from a different age and mindset to listen to and also to destroy the mini-monitor market. The presentation is so far from magazine audiophile expectations and guidelines that this demo had tremendous shock value. If you survey show reports many called it the best sound there...and this coming from a 62 year old speaker.

A lot of people remarked in amazement on the thin original wire which looked like it came from an old doorbell system. Pretty funny since we had tens of meters of Audio Note Litz and Nordost silver around the room on the speakers we were not playing. This is not the thing that would jump out at me but obviously people are wire-mad these days.

I occasionally heard a slight edge to the sound depending on listener position, how loud it was turned up, and how many people were in the room to absorb reflections from the hard side walls and glass. On the whole, I would say it erred on the side of being overly soft and creamy rather than harsh. It was a success in musicality and impact rather than ultimate refinement and sophistication.

Most of all, the idea of bringing this old speaker was to get people thinking. It was a subversive plot.

Posted by el`Ol on 05-17-2010
fiogf49gjkf0d In one point you win, obviously the speaker panels were not really infinite indeed. http://www.thomas-schick.com/Siemens.htm But when the frequency where the dipole acoustic short circuit "kicks in" is clearly below the Fs of the driver, everything "dipoly" that can happen are rear wall reflections with the wrong phase, and that danger is also reduced by huge baffles.

Posted by Romy the Cat on 05-17-2010

Joe Roberts wrote:
The Western Electric L-9 in Munich was/is an infinite baffle design. The 754B woofers are in a sealed enclosure with a front horn. There is no possibility of cancellation between front wave and back wave of speaker, so I wouldn't call it an "open baffle" in any way. Don't be fooled by the wings.

If those speakers in Munich had woofers in sealed enclosures then they were the infinite baffle design. I might be “fooled” by the wings but if it was sealed enclosures then why the wings were there? Undoubtedly the wings have a huge negative effect the MF and HF so why the “stupid” WE engineers even did the wings? I do not know certainly how the Western Electric L-9 was made but I think it is not sealed enclosures. Some of the drivers of the period used the semi-transparent cloth enclosures that you, Joe, might recognized as sealed. In reality the cloth damp a bit HF but near transpired at the lower end and here is where the duty of the wings kick in – pure open baffle.

Joe Roberts wrote:
Most of all, the idea of bringing this old speaker was to get people thinking. It was a subversive plot.

It is not. I know very well the mind frame of the people who bringing the old speakers to the show and those who “admire” them. There is no thinking in any of them but only a desire to make splashy hype, nothing more. The individuals who what to get people thinking bring to the shows Proper Sound and very seldom or even come from the “old speakers”. It is a whole different subject however…

The Cat

Posted by el`Ol on 05-17-2010

el`Ol wrote:
In one point you win, obviously the speaker panels were not really infinite indeed.

http://www.thomas-schick.com/Siemens.htm
But when the frequency where the dipole acoustic short circuit "kicks in" is clearly below the Fs of the driver, everything "dipoly" that can happen are rear wall reflections with the wrong phase, and that danger is also reduced by huge baffles.

With larger baffle compared to the wavelength the figure eight becomes fatter and most of the room is pressurized again, just one half in the wrong phase.

Posted by Romy the Cat on 05-17-2010

el`Ol wrote:
But when the frequency where the dipole acoustic short circuit "kicks in" is clearly below the Fs of the driver, everything "dipoly" that can happen are rear wall reflections with the wrong phase, and that danger is also reduced by huge baffles.

Your logic is correct but you refuse to see the whole picture - this is the biggest mistake the admirers of the open baffles do. Let trace the entire process. You grow the size of the baffle in order to keep the speakers to enter the “dipole mode” at the level where acoustic pressure under Fs is dropped. If you are at 1000Hz or 500Hz or even 200Hz then it is doable and it work very nice. However, if you are at 50 Hz or at 30Hz then the size of the wake grows significantly faster and ne you need truly huge baffle. Let forget the LF acoustic shortage due to the reflection while the huge baffle are being used. The very large baffles would require very large rooms, this is understandable. The very large rooms would require more and more acoustic pressure injected into the room in order to reproduce the relatively low frequency. Pressure might be built up only by surface and exertion. The driver’s surface is fixed, so to get more pressure at LF in the very large room we need to exert the drivers further. Unfortunately the drivers in the past were not made to work in heavy exertion mode. The best older woofers are hard-suspended drivers and they did VERY good tonally in limited dymick ranges. Drive then a bit harder and this coils will run out of their very short saturated magnetic gap and their wonderful tone get converted into very severs distortion. Take for instance the best Klangfilm woofers and play them louder then mezzo forte – they dive into very sever distortions. It is not to mention that ALL open baffle driver at the bottom sound absolutely the same…

So, it shall not be said that I am against the open baffle for bass. The lower octave un audio might be reproduced by only infinite baffle and sealed enclosures are the subordinates of the infinite baffle, the subordinates that in my view have even some advantages over the infinite baffle.

Rgs, The Cat

Posted by el`Ol on 05-17-2010
fiogf49gjkf0d In principle a higher air gap for more linear excursion goes hand in hand with lower flux density (weaker motor) for a high-Qts driver when the amount of magnetic material is fixed. No market, however.

Posted by Romy the Cat on 05-17-2010

Mani, BTW, if Silbatone-pimping Joe Roberts showed up in here then it had to be the Aporia speakers with the back-loaded single Manger were presented in the show. Why would Silbatone otherwise to drag to the show that big and expensive mastodon from 1948?

http://www.romythecat.com/LatestPosts.aspx?ThreadID=9376

So, how the single-driver Aporia sounded back there? I am sure that Mr. Roberts would feel that Aporia was wonderful and will tell a story that after listing of them the entire contingent of Munich Philharmonic requested to rename their band to Sound Practicing Orchestra. Still, how Aporia Sound? Anything remotely positive?

The Cat

PS: I have isolated the Munich Show subject in own separate thread.

Posted by manisandher on 05-17-2010
fiogf49gjkf0d I visited the room on six different occasions throughout Saturday and never once heard the Aporias playing. The reason that was being cited was that people wanted to listen to the WEs. Strange then that the Aporias should be there at all. FWIW, I sat/stood in a different location on each occasion - the WEs definitely had an edge as far as I'm concerned... Mani.

Posted by manisandher on 05-17-2010

el`Ol wrote:
The Hifi Deluxe was in the Le Meridien... Would have been interesting what you think about the Duevel (and whether you like the MBL top end for being omnidirectional only).

I didn't know this, which is a shame as I definitely would have popped in.

Maybe an omnidirectional top end works well. If the hyper-expensive MBLs are anything to go by, omnidirectional mids and upper-basses definitely don't. But I would have liked to have heard the Duevel to find out.

Mani.

Posted by Romy the Cat on 05-17-2010

manisandher wrote:
I visited the room on six different occasions throughout Saturday and never once heard the Aporias playing. The reason that was being cited was that people wanted to listen to the WEs. Strange then that the Aporias should be there at all.

Hm, the Silbatone did not even make an attempt to demo Aporias? This is very odd. I might understand the desire of the people to hear WE but Silbatone in a business of selling amp, speakers and the rest and the entire objective of the Silbatone’s trip to Germany was to expose their products to public. I guess if the Aporia was there but was no demonstrated then it was ether broken or performed so bad that Silbatone folks desired do not jeopardize the bad rep for a new model. This in fact characterize Silbatone folks quite positive in my view.

Rgs, The caT

Posted by Joe Roberts on 05-17-2010

I do not know certainly how the Western Electric L-9 was made but I think it is not sealed enclosures. Some of the drivers of the period used the semi-transparent cloth enclosures that you, Joe, might recognized as sealed.

The L-9 enclosures were wood on all sides. Sealed box. No ambiguity here.

Wings were common on theater speakers for mid-bass reinforcement. Plainly audible improvement on these and, for example, A-7/A-5 VOTs. It is equivalent to in-wall mounting down to a freq determined by the width of the extensions.

There is no interference with MF and HF from the side baffles because those frequencies come out of the 60 degree horn on top of the cab, obviously.

There is nothing mysterious or technically-special about the L-9, it is just a competent Alnico WE system. Typical late 1940s pro sound engineering.

----------------------

We had the Aporias set up but we only played them at the end of the day on appointment because the WE was a very popular exhibition. We usually had 25-50 people in the room and they were digging the show so we went with it.

Also the room was huge (15x15m) which is too big for most speakers, Aporias included. How many speakers can impress in a 50 ft. square room with 50 people in it? The sweet spot can only fit three or four listeners and the other 47 would be screwed, even if it would play loud enough to overcome conditions, which it didn't. The size of the room is why we brought the WE horn.

For those really interested in Aporia, we gave them semi-private demos where the speaker had a chance to perform.

The Aporia is very limited production and we are not worried about sales, so 99% of the time we went with the antique demo that seemed to be catching peoples attention and interest.

We successfully demonstrated the Aporias at three shows already, so it was fun to switch to something offbeat. We had a great time and so did many of our visitors.

Yeah man, pimpin' is hard work...you got to be ready to adapt, improvise and, overcome! Plus you have to have the right hat.

Posted by moreart on 05-18-2010

Hello,
i constructed a Mangerhorn 1984,
manger bought the lizence 1994

what i don´t understand by silbatone Manger horn
NO measurement, No IMP

Data:• 8 ohm, 93 dB/1W, Max. SPL - 120db

i never get more than 95 dB max.
and 1W1m 90 dB

and the lense IMHO can´t make no colourations

my Horn called BASSTUBA
measurements, plan, feedback and i am only DIY
http://www.hm-moreart.de/18.htm

Posted by Romy the Cat on 05-18-2010

Joe Roberts wrote:
The L-9 enclosures were wood on all sides. Sealed box. No ambiguity here.

Wings were common on theater speakers for mid-bass reinforcement. Plainly audible improvement on these and, for example, A-7/A-5 VOTs. It is equivalent to in-wall mounting down to a freq determined by the width of the extensions.

There is no interference with MF and HF from the side baffles because those frequencies come out of the 60 degree horn on top of the cab, obviously.

Hm, the sealed boxes – I am surprised – I would never guess. The wings are for the mid-bass reinforcement? That is a bold waste of speaker’s surface for a small result. BTW, I presume that 60 degree horn is only if you stay literally under the horn but from a reasonably listing distance the HF channel runs at much much lower angle. Unfortunately all, absolutely all with no exception speakers with open baffle (including with the “wings form mid-bass reinforcement”) suffer from the fact that the large vertical surfaces of their baffle flatten out the upper frequency. The upper frequency starts to be fluffy and reminds a fur of wet animal. To “cure” it people inject more amplitude in HF, overloading the initially sub-sized horns. This is what many Morns call “vintage sound”. Ironical to demonstrate the problem is very simple – juts to toss a hairy blanket/carpet atop of large baffle. Of course then the blanket will cover the WE logo and then many audio “writers” will have no subjects to write….

The Cat

Posted by Joe Roberts on 05-18-2010

Moreart, somebody sent me this link last year. You are surely the DIY pioneer of back loaded Manger.

As you probably know this is a touchy speaker to work with.

Rated at 91 dB/W input by the factory, we measure ~91 up to near 92 dB/1W/1m in our two most recent tests in room in a horn! These are the numbers we are now publishing in our brochures.

One would think that the sensitivity would be at least the same in a backhorn...but maybe there is a reason why not that doesn't occur to me. Your results are even lower than ours.

Otherwise, we have found that our speaker is so sensitive to room placement and wall reinforcement that it is difficult to come up with "standard" response measurements. We don't have an anechoic chamber and that wouldn't be very useful info if we did. I can say that we are getting 30hz in-room down about 3-4dB from 100hz. Low end response and subjective quality is very dependent on distance to walls. Measurements are not repeatable site to site for the most part.

As for comparisons between your back horn and ours, your construction is much smaller and a folded horn of the Lowther style. Our horn is 9 ft long, no sharp angles, and relatively unconstricted. I don't know how to compare these theoretically with regard to expected specifications. It seems to me that ours should be somewhat more sensitive and produce lower bass since it is larger.

Again, we found that this driver is very tricky to play with in a backhorn and small tuning adjustments have a large effect. Ver small changes to the diffuser or internal taps totally change the presentation. Consequently, all constructions will vary and it is impossible to generalize.

As for maximum loudness, we recommend low power amps such as 300B SE with the Aporia. I would not overpower the Manger in a backhorn since it is not specified for this application. With a 300B, we get adequate volume for home applications and enough to compete with the high noise level at audio shows. With 8W, the amp typically clips before the speaker runs out of juice. At that point it is quite loud for routine living room listening.

At Munich, we cranked the Aporias up with a 20w 845 SE and they did not catch on fire but our goal for the speaker is "big horn sound in normal sized rooms"--and 8W will do that.

Posted by Joe Roberts on 05-18-2010

That is a bold waste of speaker’s surface for a small result.

Yeah, but plywood is cheap and the result is audibly noticeable. Baffle extensions were recommended for all of the Altec VOT cabinets too. Make a big improvement for cheap if you have the space.

As the frequency decreases and output becomes more omnidirectional, the baffle provides a +3dB reinforcement like a close wall would. With 250hz around 5ft wavelength you can get a good mid-bass boost with a sheet of plywood.

Unfortunately all, absolutely all with no exception speakers with open baffle (including with the “wings form mid-bass reinforcement”) suffer from the fact that the large vertical surfaces of their baffle flatten out the upper frequency.

It is not "open baffle" and the upper frequencies come out of the horn which is above and apart from the baffle. 800hz crossover.

Have another look at the picture. You are confusing this L-9 with some other topology, I think.

The upper frequency starts to be fluffy and reminds a fur of wet animal. To “cure” it people inject more amplitude in HF, overloading the initially sub-sized horns. This is what many Morns call “vintage sound”. Ironical to demonstrate the problem is very simple – juts to toss a hairy blanket/carpet atop of large baffle. Of course then the blanket will cover the WE logo and then many audio “writers” will have no subjects to write….

That WE logo must be very powerful since at least 20 online show reports named this old junker "Best of Show"! Most of the German forum threads have a few guys who thought it was the best thing there.

We were quick to remind everybody that this was a second-rate WE system but they didn't seem to care. To my ear it was a bit more "vintage sounding" than the field coil WE gear and it wasn't "perfection" but at least it had some soul, which most of the plastic speakers at the show lacked.

Also, for many of the visitors this is the first time they heard a decent sized horn and that probably explains a lot of it.

We are tempted to bring a theater-type system that is a step above the L-9 next year, since this was such a hit.

Posted by Romy the Cat on 05-19-2010

Joe Roberts wrote:
Yeah, but plywood is cheap and the result is audibly noticeable. Baffle extensions were recommended for all of the Altec VOT cabinets too. Make a big improvement for cheap if you have the space.

As the frequency decreases and output becomes more omnidirectional, the baffle provides a +3dB reinforcement like a close wall would. With 250hz around 5ft wavelength you can get a good mid-bass boost with a sheet of plywood.

Is not about the cost of plywood bit the placement cost if the speakers have this type wings. Sure, for monophonic films in 40s and multitude listeners in this it was not a problems but for contemporary stereophonic sound it make the speaker positioning very difficult if even possible as this type of speaks even in very large room would have very limited option to placed them in the room.

Joe Roberts wrote:
It is not "open baffle" and the upper frequencies come out of the horn which is above and apart from the baffle. 800hz crossover. Have another look at the picture. You are confusing this L-9 with some other topology, I think.

From the prospective I described above it is the "open baffle". Take any loudspeaker, even contemporary monitor and pace a 3 feet by 5 feet untreated board between them. Listed how that surface dry out sound and kill imaging. Do not call it "open baffle" if you would like to, call it “oversized baffle”.

Joe Roberts wrote:
That WE logo must be very powerful since at least 20 online show reports named this old junker "Best of Show"! Most of the German forum threads have a few guys who thought it was the best thing there.

Ohl, here is the ultimate price! Are you one of the men who watch the Miss America shows? BTW, the fact that your German forums junkers find your WE as the Best of Show is not the indication of WE sound but the indication of level of the Show.

Joe Roberts wrote:
We were quick to remind everybody that this was a second-rate WE system but they didn't seem to care. To my ear it was a bit more "vintage sounding" than the field coil WE gear and it wasn't "perfection" but at least it had some soul, which most of the plastic speakers at the show lacked. Also, for many of the visitors this is the first time they heard a decent sized horn and that probably explains a lot of it. We are tempted to bring a theater-type system that is a step above the L-9 next year, since this was such a hit.

The fact that your Korean friends would like to expose the sound of this WE collection to public is not bad but there is concern of my in all of it as well. You and your friends are not in the business to facilitate better sound for the visitors but rather to build up publicity for audio yahoos. You might drag a few years some vintage gear to the show as some local folks did in the 2001-2002 in US but soon or later your Silbatone guys would need to build some kind of bridge between the hype you will be creating with your WE and the current Silbatone production. I do not see this bridge easy to build. Also, soon or later you will recognize that comments of online posters do not push sales figures. I wish your Silbatone people have enough perseverance and money to demo their WE gear with having any financial gratitude.

The Cat

Posted by moreart on 05-19-2010
fiogf49gjkf0d Hello, my Manger measurements are here: http://www.hm-moreart.de/76.htm my experience fullrange in the Basstuba shows ~5W are the max. input before it gets listenable worth. (volume control 11 a clock) good luck.

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