Let's discuss horn preferences

[Bernard Wolf]

[QUOTE]Originally posted by Jan Daugaard
[B]I have a 4.0 surround sound system composed of 2 pairs of S3100, and they contain a 2426H compression driver mounted on a H2600 horn.

The H2600 is asymmetric and is intended to provide a large sweet spot, but the opposite is the case in my experience. "

I have to correct you on this statement Jan - I too have the 3100 and the CD lens is meant to provide a large listening area wherein which it is possible to get a stable image off axis. This, the 3100 it does admirably. Nothing worse - especially in a home cinema set-up - than to only hear what is coming out of the speaker directly in front of you. The sweet spot is still for one person only though, as in every other speaker in existence.



"There is, however, one significant advantage to the asymmetry, namely that they can be placed in corners to boost the bass -- the horn has so little radiation to the one side that there will be no annoying reflections from the adjacent wall".

I like to listen to mine set up out in the room and away from room boundaries but there is no dening the advantage they posses in confined quarters.

Bernard

[Bernard Wolf]

Originally posted by Robh3606
Hello Jan

Wow so they don't throw a large image?? I wonder how they compare to the Everest horn. Can see they look similar. How is the imaging in the sweetspot?? Can you get up close or does the image fall apart in close?? How far away are you?? You can move around some what right??

Rob

Hi Rob - as I have the s3100 I can answer some of these questions for you. They throw a sound stage as least as wide as they are apart which in my case is 9' center to center. Also, as I fire mine across a corner and about 10' out from the corner I also get at least that much stage depth. When I kick in my side/rear mounted hafler rear speakers - which is a small 2-way grundig speaker - I get a 15-20 ' soundstage !! The imaging is fantastic, and don't take my word for it. For what it is worth, Dominic Baker who now heads up JM labs development dept. in his July 1996 Hi-Fi World review of the S3100 said " it (3100) has qualities that place them on par with Quad ESL 63s in my opinion. They are completely different from the Quads, their strengths lying in other areas, but the level of fidelity is similar. Both the 3100 and the Quads image especially well; both are a reference to others in this respect". I concure having owned ESL 57s.

I can get as close a s a 3-4' before the image dissapears and as I mentioned in a previous post I can sit well off center and still enjoy a credible soundstage. A great accomplishment. I'm surprised they stopped using this design. The only dowside I can think of is that because of the directionality of the horn one does not hear as much of the room. Many would find this to be a plus but I am experimenting with rear firing ambience retreaval super tweeter to quite good effect to offset this for my taste.

Bernard

Bernard

[aust-ted]

Hi

I have read this thread late but have found it most interesting as I was intending to construct a pair of conical horns to go with a pair of 2451s.

Currently my system is comprises

Dual 2235H in
2450/ 2380A
2404

with active xovers at 800Hz and 5Khz

This is my first JBL system and I have been impressed by it. However I have yet to try other mid horns.

Firstly has anyone else tried the 2380, or its big brother the 2360, CD horns in a home environment?

Secondly I want to get the bass/ mid xover point out of the critical listening range if possible. Therefore I intend to build conical horns with a 500 Hz capability and even try 300Hz with 2482s as Maron has raised. However I have been advised that to minimize mouth distortion I should aim at around 30 inch for the mouth width for 500Hz .

The objective behind the conical horns is to reduce mouth distortion and frankly they should be easier to construct.

Any suggestions/ comments?

Ted

[Ian Mackenzie]

You may wish to email or pm to Steve Schell, he is a horn fanatic.....

Ian

[Robh3606]

Hello Aust-ted

Well if you can't do the horn for size look at the 10" drivers in that range. Either a 2122 or a 2123 could get you through that 300hz-1.3k range without the space issues.

Thanks Bernard


Rob

[aust-ted]

Rob

Thanks

I am aware of the benefits of using the 10" or like as an upper bass etc especially if you make it a 4 way like some of the better JBL monitors.

However space should not be a problem. I have made my twin 15" cabs fairly deep (about 4ft) and low (about 2 ft high) so I can put the horns on top and keep their centre at ear level. The cabs are about 15 cu ft ea. They are made out of 1 1/2" veneered particle board with a lot of internal bracing.

I am keen to retain high efficiency which was a main reason for going to twin 15" drivers as I am using a mimiscule fraction of their power handling. However I am currently using a Perreaux 6000B commercial mosfet amp (500W at 4 ohm) for the bass and a 17w triode wired Leak St 50 tube amp for the mids. I suspect I rarely put more than a few watts into any of the drivers.

I have a copy of a construction article on conical horns which I believe originates from Peavey. Another option is to make a pair of2360 wooden CD replicas (I have the throats). Or make a Tractrix like the Edgarhorn salad bowl. As I am a relative novice, I would appreciate any advice or suggestions on these or other options.

Regards
Ted

[Ian Mackenzie]

Ted,

There are many ways you can do this.

An option as per a Kilipsch modifcation to change out their mid horn was to use 2 x 2123 drivers , this gives very high sensitivity, over 100 db. You could still use your tube amps and maintain accuracy of a cone.(The 2123's do turn up on ebay a bit) .

Ian

[aust-ted]

Ian

Thanks

I have heard very good things about the 2123.

However at this stage I would like stay with three ways and 24xx series compression drivers for mids as I have acquired some.

One of my motivations with considering 2451s with conical horns is that I understand you can do away with the tweeter and go to a two way. From reading posts by Dr Earl Geddes on the DIY forum and from his book, I understand the use of conicals with their greater expansion rates give less throat distortion which from my layman's perspective I understand provides for a better HF response from a driver such as the 2451 on a conical horn, or have I got this wrong?

Regards
Ted

[Mr. Widget]

My understanding is that conical horns, that is horns with a conical rate of expansion as opposed to exponential or tractrix rates and not to be confused with the conically shaped exponential horns JBL used to use with the 10" slant plate lenses, have some theoretical advantages with lower throat distortion but they have a very high HF roll off. I haven't read Dr Earl Geddes' work, but he must be using significant equalization in conjunction with his horns if he is suggesting you can use a conical horn in a two way.

I will look him up and check out his work as you have piqued my interest.

Widget

[aust-ted]

Mr Widget Wrote in part >"My understanding is that conical horns, that is horns with a conical rate of expansion as opposed to exponential or tractrix rates and not to be confused with the conically shaped exponential horns JBL used to use with the 10" slant plate lenses, have some theoretical advantages with lower throat distortion but they have a very high HF roll off. I haven't read Dr Earl Geddes' work, but he must be using significant equalization in conjunction with his horns if he is suggesting you can use a conical horn in a two way. "

Hi Mr Widget

My understanding, which is limited at this stage, is that you are correct. Conical horns do require equalization as do the 2380 and 2360 Constant Directivity horns. However I thought the equalization was linear and easy to implement but I have not tried it yet. My JBL active xover has equalization in built for 2380 and 2360 CD horns

I must clarify that it was not Dr Geddes that suggested I try two way. However he has contributed to discussions on the DIY forum where he has discussed the issue of conical horns which he calls waveguides. He certainly discussed the question of throat distortion.

He also kindly responded to a query I emailed him on the subject and I have since purchased a copy of his book though I am yet to fully absorb it.

A local retired sound engineer suggested I try 2451s with conical horns as a two way. I understand that some of the more recent JBL horns are described as Progressive Transition Waveguides (eg PT- H95HF) and are essentially conical . These are discussed in JBL Technical Notes Vol1 #31 which I downloaded from the JBL Pro web site.

Also your observation re "conically shaped exponential horns JBL used to use with the 10" slant plate lenses" is spot on. Dr Geddes recently made a post on the DIY forum in which he referred to difraction horns negatively. Dr Geddes wrote "Diffraction horns sound the worst, being obviously flawed by all of the internal reflections and non-planar wave propagation that result from the diffraction points, this is widely acknowledged." I understand that the slant plate lenses are what he is referring to. Hope I got that right.

Regards
Ted

Regards
Ted

[Mr. Widget]

Originally posted by aust-ted
Dr Geddes recently made a post on the DIY forum in which he referred to difraction horns negatively. Dr Geddes wrote "Diffraction horns sound the worst, being obviously flawed by all of the internal reflections and non-planar wave propagation that result from the diffraction points, this is widely acknowledged." I understand that the slant plate lenses are what he is referring to. Hope I got that right.

Regards
Ted

Regards
Ted

Could be, but it is most likely he is referring to diffraction horns like the EV 8HD diffraction horn or perhaps even the JBL 2397 which is also a diffraction horn. I would agree with him about the EV and many others, but disagree about the 2397. I don't doubt that the theoretical disadvantages of the diffraction principle may be valid, but in practice the 2397 is a fine sounding horn.

The conically shaped exponential JBL 2307, 2311, and 2312 use the 10" slant plate lens that uses the principles of a diffraction gradient to guide the sound waves. These are not diffraction horns, but do have many reflections and do have their detractors.

Widget

[Ian Mackenzie]

To as spice to your posts, this is certain to cause some more replies.......here are some measurements of the 2307 exponential horn with and without the 2308 lense.

The measurements were done near field and all room reflections were time gated out of the near field. The horn is mounted in the 4345 baffle and feeb via the passive network.The other drivers have been padded fully down.

Note the straight horn is remarkably smooth with a slight rise after 6000 herts, the divisions are 6 db so this is very flat for any horn.

Ian

[Ian Mackenzie]

This curve is with the 2308 lense under identical measurement conditions.

The sensitivity overall is lower somewhat and there appear lots of ripples in the response. I have not done any detailed listening tests to confirm any audible difference yet. I will do that in the morning as Sunday is a JBL day.

Ian

[aust-ted]

Ian

Thanks Very Interesting

On a separate but related point, I acquired a pair of 2309 horns some time ago, unfortunately without the 2310 lenses. I am intending to play with them when time permits but was hoping to pick up the lenses separately or home make something that approximates them.

Just looking at the horns gives me the impression that without the lenses that they would be very long throw and not suited to home use. I assume the 2310 lenses purpose is to make the horns more useful for nearfield and off axis listening? I am aware these are different to the slant plates you are discussing but again I suppose the purpose is similar. Have I got that right?

Regards
Ted

[aust-ted]

Ian

I forgot to comment on the obvious lifted 2307 lower freq response you obtained with the lens even though, as you comment, the horn with out the lens has a much smoother response in the 1.5k to 9k freq range. I assume this lifted low freq response relates to an apparent larger mouth brought about by the lens.

Regards
Ted