What is special about horn loaded drivers?

[Floyd Toole]

Concert halls minimize absorption - except for the audience/chairs which are a given. The reason is that the voices and musical instruments have finite sound output, and it is the task of the concert hall to sustain that energy through reverberation (but not too much) and reflections (for diffusion to deliver the sound to all parts of the hall). Technically, concert halls are elaborate comb filters that sound wonderful - I go to about a dozen symphony concerts a year and no stereo recording is in the same league.

So, the acoustical design of concert halls has nothing to do with fiberglass. It has a lot to do with scattering. Sound reproduction is a different thing. Unlike your ballroom, the reverberation time in a home listening room is probably less than 0.5s, more like 0.3s in a well furnished room. You will also very likely be in a dominantly direct sound field at middle and high frequencies, so transients will be well delivered.

 

[Floyd Toole]

Concert halls minimize absorption - except for the audience/chairs which are a given. The reason is that the voices and musical instruments have finite sound output, and it is the task of the concert hall to sustain that energy through reverberation (but not too much) and reflections (for diffusion to deliver the sound to all parts of the hall). Technically, concert halls are elaborate comb filters that sound wonderful - I go to about a dozen symphony concerts a year and no stereo recording is in the same league.

So, the acoustical design of concert halls has nothing to do with fiberglass. It has a lot to do with scattering. Sound reproduction is a different thing. Unlike your ballroom, the reverberation time in a home listening room is probably less than 0.5s, more like 0.3s in a well furnished room. You will also very likely be in a dominantly direct sound field at middle and high frequencies, so transients will be well delivered.

 

[Floyd Toole]

Highfigh: Our contributions passed in the ether

Now I think I understand - you are trying to reproduce sensible sound in a staggeringly reverberant space. Unfortunately there are some things that are simply impossible. That said, the best you can hope for is to use directional loudspeakers, or a distributed sound system, or both to do the best you can to put the listeners in a strong direct-sound field. And probably keep the bass levels down because the bass will very likely boom forever.

Sorry, I did not read the earlier entries thoroughly.

 

[Floyd Toole]

Highfigh: If you cannot change the visuals in the room, you are fighting a losing battle. If you can modify any of the tapestry covered surfaces to have some fiberglass under them, that would be a great help. Any amount of carpet with felt underlay that can be sneaked in. Maybe a creative interior decorator can integrate some suspended absorbers from the ceiling. Without more absorption, I don't think you can hope for much in the way of "highfigh". Sorry.

 

[TLS Guy]

TLS Guy – Speaking of Fat Ladies, thanks for the youtube video of Grande Dame in Pink. What is her name? She was enjoyable, even if I don't care for opera.

The satirist was Anna Russel.

 

[TLS Guy]

A state-of-the-art home theater is better than any cinema. But a good cinema can still be very good.

Part of the problem in both venues is the unpredictable quality of the soundtracks, which are mixed in x-curve calibrated dubbing stages (HF rolled off, bass insufficient). There is a fundamental incompatibility between cinema sound and the rest of the audio industry - read my paper!

Added to this is the unreliability of the cinema, dubbing stage, calibration process that follows an obsolete and flawed process. Lots of cinemas have been made to sound worse by the calibration process.

If movies don't sound great in your system, don't necessarily blame the system.

Thanks for joining the discussion Floyd.

You are absolutely right about a good home theater sound besting cinema sound. Mine certainly does, and we always wait the the BD.

However I don't think this is all the fault of the cinema. Loudspeakers tend not to do well in large spaces as they are poor connectors too the space.

I have spent quite a bit of time with pipe organ builders. They point out one of the big differences between a loudspeaker driven electric organ and a pipe organ. The electric instrument is very loud close to the speakers, and falls off in intensity quickly as you move away from the speaker stacks.

A pipe organ however fills the space and the volume is very uniform throughout the space. Organ builders have a term for this phenomenon. They call it encircling. I don't think the physics if this is well understood at all. One of the results well known to organists, is that a congregation will sing much more lustily to a pipe organ than an electric one.

I have long felt this issue is a neglected avenue of research.

 

[TLS Guy]

I wish I could have JBL M2 as my LCR, from all accounts its the be all end all of speaker design. But I can't.

Also one more point I'd like some clarity on - there's a lot of talk about how 2ch music is so different from HT and requires different guidelines/speaker choices etc. But I don't listen to music in pure direct mode anymore (this is where I should get ready to be called a heretic ), since the music matrixing modes like DPL II etc sound much nicer to me. And with multiple speakers, doesn't dispersion become less of an issue? What happens to soundstage and imaging? I doubt if there are even any proper DBTs conducted on this?

I don't think the demands of HT and two channel audio are different. In fact in HT you have to up the game. The reason for this is that you are dealing with the human voice and having to produce clarity throughout the seating area with great uniformity. The low frequencies of the background music must be tight and not be resonant and mask the voices. For speakers systems this is a huge challenge.

The end result is that HT systems often tend to have a degree of shout for artificial voice enhancement/clarity. This is very irritating for music. Hence many end up with two systems.

If the overall design is correct, a system can be superb for HT and music.

 

[TLS Guy]

I think I have seen that video but in light of the room I'm working with, I'll ask this- how would you deal with reverberation times that exceed 6 seconds? Wood lath & plaster ceiling, plaster on brick over poured concrete basement walls and terazzo floor. I can't imaging why anyone would enjoy listening to music or speech in this room. The home was built in 1917 and this room was called the Ballroom. The front and left wall have a small moulding around the perimeter, the walls in the rear have smaller framed areas and the right wall has a fireplace. Nobody has been able to find photos of the room when the original family was there, but the large area on the two walls make me think they may have hung tapestries or some kind of fabric wall hangings. The reverberation is very even, though. With a room full of people, it wouldn't be as bad.

I have photos, if you're interested in seeing them.

I will do my best to answer the interesting points you raise. Of course you can have too much or too little reverb. Mainly chance gets it just right.

Now as to concert halls and churches it is not simple. Many of the old concert Halls do not need acoustic treatment. By luck or design they are perfect, like Vienna's Musikverein

Modern music halls are not like that and generally need a lot of treatment.

Halls can have too much and too little.

The Royal Albert Hall in London was a dog acoustically. Sir Edward Elgar said of it:- "That is is the only place in London where I can hear my music twice in one night!"

The hall is a round dome. They are a problem because of radial echo paths. The BBC hung the famous flying saucers in the dome which have been very effective.

The Royal Festival Hall on the South Bank, built in the early fifties is a dog because it is dead. Active resonators installed by the BBC were a partial success at best. An expensive building project to lengthen the building was only a small improvement to my ears.

At the Place Des Arts in Montreal the acoustics can be altered to the needs of the program. It can be changed in concert. It seems slow and when altered can cause significant delay between works.

Older churches are generally the Italian domes, or the Norman/anglo saxon long nave style. Both have a long echo, but different, with the dome mixing up the music the most.

Much historical research has been done on this. The music of the Italian high Renaissance contains intricate moving interwoven lines. Frankly in the domed cathedrals it Italy it does not sound all that good. So musicologists have carefully researched paintings of the era, and find that tapestries were hung all over the place and also huge banners on poles moved in. There is definite evidence of massive artistic acoustic treatment at the time.

So with your room there very likely were tapestries on the walls. I think you will need to pursue some highly sensitive and artistic wall treatments.

 

[Defcon]

That's very interesting! So even back then people either had a basic understanding of acoustics, which is not really surprising since many buildings must have been designed with acoustic goals, or perhaps someone found out by accident that acoustic treatments helped the sound.

My basic question was probably too broad so let me narrow it down - for a typical apartment setting - rectangular room with some openings, no room treatments, listening to both HT/music in multi-channel, which of these 2 would be the better choice -

1. high efficiency with limited dispersion, big woofers + horn
2. wide dispersion, i.e. normal speakers with smaller woofer + dome tweeters

Assume other things such as the quality of drivers/crossovers is the same, and any sound quality differences are due to the above 2 design choices.

I hope this question makes sense? If there is no clear answer then that's fine but I'd be happy if there was

 

[TLS Guy]

That's very interesting! So even back then people either had a basic understanding of acoustics, which is not really surprising since many buildings must have been designed with acoustic goals, or perhaps someone found out by accident that acoustic treatments helped the sound.

My basic question was probably too broad so let me narrow it down - for a typical apartment setting - rectangular room with some openings, no room treatments, listening to both HT/music in multi-channel, which of these 2 would be the better choice -

1. high efficiency with limited dispersion, big woofers + horn
2. wide dispersion, i.e. normal speakers with smaller woofer + dome tweeters

Assume other things such as the quality of drivers/crossovers is the same, and any sound quality differences are due to the above 2 design choices.

I hope this question makes sense? If there is no clear answer then that's fine but I'd be happy if there was

I can give you definite advice about this. Don't be surprised if someone wants to give you different advice.

Whist Dr Floyd Toole has given testimony to some cutting edge technology making for much better performing horns, I don't think they will be available to you. Even if they were you are not going to able to afford them. It is also possible you would not be able to physically get them in your apartment.

I think there is consensus here, that while big 12 or 15" drivers mated to a horn might sound somewhat more like "cinema sound", they really are not the most accurate of speakers. In that event you are likely to get the urge to have an HT system and a music system. This is absolutely not necessary and you are better off putting funds to one good system.

I think there actually is consensus here that systems with wide dispersion, flat frequency response, with the dispersion mirroring the on axis response are most likely to sound best in an apartment. In addition to which I would add low Q bass system, to keep the bass tight.

A system broadly following those principles is most likely to work best for you. In addition your room is unlikely to need acoustic treatment.

I think there is consensus here that a dead room is not a good thing. Most domestic rooms, at least in my experience, do not have a troublesome reflection pattern, at least out of the bass decades. The latter can be a problem though, especially if the room does not have a definite long dimension. The worst situation would be a cube. The nearer a room fits that description the more trouble you will have in the bass frequencies. The more it looks like a small version of the Musikverein the better off you will be.

 

[Swerd]

My basic question was probably too broad so let me narrow it down - for a typical apartment setting - rectangular room with some openings, no room treatments, listening to both HT/music in multi-channel, which of these 2 would be the better choice -

1. high efficiency with limited dispersion, big woofers + horn
2. wide dispersion, i.e. normal speakers with smaller woofer + dome tweeters

I agree completely with TLS Guy. Go with choice #2.

On a purely practical level, consider these features of the JBL M2 and imagine them in your apartment. Each of them are:

46.5" tall × 20" wide × 14" deep
129 lbs
Recommended amp power: 1,200 watts at 8 ohms in the form of 1 Crown iTech 5000HD power amp per speaker
They can deliver up to 123 dB SPL
System tuning requires external measurement hardware and software, not supplied as part of an M2 system​

http://www.jblpro.com/ProductAttachments/M2_Brochure_Jan2013.pdf

I never looked up the prices for all this. Nor did I get a price for the audiophile grade forklift you will need .

 

[KEW]

I lust after having three across the front of my HT, and the L & R in stereo are absolutely killer. In blind tests they are not distinguishable from cone and dome systems - until you turn up the volume.

I just caught this on second reading. What happens when the volume goes up?
Are you referring to the non-horn speaker's inability to match high SPL, or does the horn start to take on a different character as it is pushed?

The point: a good speaker is a good speaker, horn or not. Most horns in the past had characteristic sounds - we believe we know why - we needed more science.

Cheers,

Floyd

Can you dust off your crystal ball and comment on this new science from an affordability standpoint?
What I am asking is - certain technologies like Beryllium tweeters are inherently expensive to implement. On the surface, it seems like the new science here is primarily the shape of the waveguide, which, aside from some upfront analysis, shouldn't cost more to produce than a poor waveguide (at least, that is my theory).

Thoughts or comments?
Thanks!

 

[highfigh]

I will do my best to answer the interesting points you raise. Of course you can have too much or too little reverb. Mainly chance gets it just right.

Now as to concert halls and churches it is not simple. Many of the old concert Halls do not need acoustic treatment. By luck or design they are perfect, like Vienna's Musikverein

Modern music halls are not like that and generally need a lot of treatment.

Halls can have too much and too little.

The Royal Albert Hall in London was a dog acoustically. Sir Edward Elgar said of it:- "That is is the only place in London where I can hear my music twice in one night!"

The hall is a round dome. They are a problem because of radial echo paths. The BBC hung the famous flying saucers in the dome which have been very effective.

The Royal Festival Hall on the South Bank, built in the early fifties is a dog because it is dead. Active resonators installed by the BBC were a partial success at best. An expensive building project to lengthen the building was only a small improvement to my ears.

At the Place Des Arts in Montreal the acoustics can be altered to the needs of the program. It can be changed in concert. It seems slow and when altered can cause significant delay between works.

Older churches are generally the Italian domes, or the Norman/anglo saxon long nave style. Both have a long echo, but different, with the dome mixing up the music the most.

Much historical research has been done on this. The music of the Italian high Renaissance contains intricate moving interwoven lines. Frankly in the domed cathedrals it Italy it does not sound all that good. So musicologists have carefully researched paintings of the era, and find that tapestries were hung all over the place and also huge banners on poles moved in. There is definite evidence of massive artistic acoustic treatment at the time.

So with your room there very likely were tapestries on the walls. I think you will need to pursue some highly sensitive and artistic wall treatments.

Modern venues are built to fit and look pretty, with the sound adjusted after the fact. Here in Milwaukee, the Marcus Center for Performing Arts was fitted with adjustable wall panels and 'cloud' panels that could be rotated to affect the sound in the way that was needed. They called it 'acoustically perfect' and it's the home of the MKE Symphony Orchestra (all of the local orchestras, actually) and many types of events are held there. I can't see how the seats at the end of the rows on the main floor would be particularly good, considering the overhang above.

http://www.marcuscenter.org/wp-content/uploads/2013/08/Uihlein-Hall-web-header_3.jpg

Domes are a special case- we have another venue that has an elliptical dome and the sound varies a bit from seat to seat but the "sweet spot" is fairly large because it's inside of the loci but it really needs to be filled, in order to make good sound possible.

I mentioned the possibility that tapestries had been there and I don't know if they'll hang the same, but because the rear of the room has smaller frames, I proposed replicating them on the left side, so it would seem consistent. I would place absorption in these, as well as behind the screen and I'm going to propose using acoustically transparent fabric since the projector isn't doing 4K. Some of the newer fabrics are said to be useful for 4K, but I would prefer to avoid jumping on that so early.

 

[highfigh]

I honestly wanted to find out if this is a better option for HT use and am still not sure - why is audio so subjective when its all based on science? It seems there are contradictory positions on nearly every aspect even from the experts in the field.

It has to be subjective- we're listening to the sound, not measuring it. The results of listening are subject to the differences in our ability to perceive sound. As Dr Toole has shown, people can have different hearing acuity, but still agree when the sound quality is good/great. However, our minds are the thing that can't be quantified.

 

[highfigh]

Highfigh: Our contributions passed in the ether

Now I think I understand - you are trying to reproduce sensible sound in a staggeringly reverberant space. Unfortunately there are some things that are simply impossible. That said, the best you can hope for is to use directional loudspeakers, or a distributed sound system, or both to do the best you can to put the listeners in a strong direct-sound field. And probably keep the bass levels down because the bass will very likely boom forever.

Sorry, I did not read the earlier entries thoroughly.

Thank you for commenting.

This is exactly the way I want to address the room- I also plan to limit the SPL (in the AVR's setup menu). When I was listening yesterday (I wouldn't want to try to design for this room, on paper), some of the modes that show up in the calculations were definitely rearing their heads. If I could move the speakers away from the wall, I would but that won't fly in this case. I turned my head 90 degrees and the reflection from the back wall was almost as loud as the direct sound.

 

[Steve81]

3) high-quality coaxial designs, like KEF's, can sound excellent. They do have controlled CD because of the coincident mounting of the drivers, but I don't believe the overall dispersion is as limited as many CD designs with wave guides.

Probably true. One example is the KEF LS50 versus the Ascend Sierra 1:
LS50 Measurements
Sierra 1 Measurements

Even at 30 degrees off axis, the LS50 is remains quite flat, while the Sierra 1 exhibits a moderate roll off in the top octave. Looking at the wide off-axis shots further demonstrates the difference in how the concentric driver controls dispersion versus Ascend's waveguide.

 

[highfigh]

Highfigh: If you cannot change the visuals in the room, you are fighting a losing battle. If you can modify any of the tapestry covered surfaces to have some fiberglass under them, that would be a great help. Any amount of carpet with felt underlay that can be sneaked in. Maybe a creative interior decorator can integrate some suspended absorbers from the ceiling. Without more absorption, I don't think you can hope for much in the way of "highfigh". Sorry.

I would assume you have used programs for analysis and development, but you may also be aware of Room EQ Wizard. I updated mine and found that it now has a room modeling function, which allows selecting the position of the L/R main speakers, listener and up to four subwoofers. The placement can be moved in three dimensions and it shows the modes and calculated response, complete with comb filtering. In addition, the absorption of any surface can be varied from 0-90 and it was interesting to see how much more of an effect the front wall has, compared with the rest.

They are planning to have a large rug and I plan to recommend padding. Treating the wall behind the 100" screen should go a long way in helping and we have already discussed adding cabinetry below to house the speakers, rather than mounting them on the solid 20" thick wall. If I can, I want to find a way to treat some of the corners, too. That cured the problems in my room very nicely and decorative screens have been mentioned.

I would also like to change the ceiling, to allow the installation of some panels. Several of the other rooms have coffered ceilings and this would be easy enough to install (compared with completely gutting the kitchen and some bathrooms).

Thanks again.

 

[Swerd]

I lust after having three across the front of my HT, and the L & R in stereo are absolutely killer. In blind tests they are not distinguishable from cone and dome systems - until you turn up the volume.

I just caught this on second reading. What happens when the volume goes up?
Are you referring to the non-horn speaker's inability to match high SPL, or does the horn start to take on a different character as it is pushed?

Kurt

When I read Toole's comment, I interpreted it as meaning the JBL M2 speakers are indistinguishable from the cone & dome types in blind tests until the volume gets high enough to be beyond the capability of the cone & dome system. The cone & dome system could not match the high SPL of the M2 system, and those differences would be clear to a blind listener.

I don't believe he meant to say the JBL M2 speakers take on a different sound quality at higher SPL.

 

[AcuDefTechGuy]

But at what cost? The advantage of the 'pro audio' style speakers seems to be high efficiency which means they can be driven to insane volume levels by your normal AVR, no need for amps.

The cost is about the same IMO. Of course, some high efficiency speakers cost a lot more than traditional stereo speakers and vice versa.

Unless you are planning on buying some cheap $250 pro speakers (that definitely won't sound like the $24,000/pair (MSRP) JBL M2), you will be paying about the same for both speakers and amps.

Who is going to use a $20 amp in his system?

Most people will be using a AVR that is about $1000 MSRP or more.

Sure, we know the $24K JBL will measure accurately. But I've never seen any speaker measurements on JRT or Seaton speakers, so I can't compare to accurate speakers.

 

[Floyd Toole]

The distinction between pro monitors and consumer speakers is (a) color: black (b) high reliability: down time in a studio is expensive (c) quality control: they all must be as nearly as possible the same (d) output: recording engineers have a "deaf" wish. There is no difference in the sound - the performance target is the same (the "circle of confusion" for those of you who have read my stuff). Part of the cost of a pro product, and also of some high-end consumer speakers is the additional cost of end-of-line quality control and adjustment if necessary. Most products simply go into boxes and the consumer is the QA department.

With the M2 and the new smaller, more affordable 7 series (http://www.jblpro.com/www/products/recording-broadcast/7-series#.VuL2mMf5jww
there is dedicated electronics with equalization based on anechoic measurements. The M2s are spectacular, large, heavy and expensive, but the essential design elements are in the 7 series. Although I "lust" after the M2s, they are not very practical for my HT. The 7 series sound just as good, and play plenty loud for a HT. No sculpted, hand polished rosewood though :-(

If you think that M2s are "efficient", consider that they are delivered with a 1 kW power amp for the woofer and the same for the horn + DSP. The horn driver is 20 ohms so it really needs the voltage swing, not the current. But in a typical HT much less power would do the job.

And, yes, the difference between them and cone/domes is that there is no discernible power compression at high sound levels. The high level distortions in horns of yesteryear (still on the market) have been substantially reduced by better throat designs. The new, better, compression drivers do not use metal, much less beryllium, diaphragms. And they go to 20 kHz. I love science!

I think I will wait for the powered versions, which I hope are in the works. Powered loudspeakers, or those with dedicated electronics are so sensible. The only reason for those monster monoblock arc-welder power amps is to drive high-end loudspeakers that are incompetently designed and have impedances that drop to 2 ohms or less. When the power amps are matched to the transducers, everything is smaller, cheaper and better, and electronic crossovers beat passive ones any day.

But then what would the audio journalists have to talk about? Wires? Spikes?