Let's discuss horn preferences

[Ian Mackenzie]

Ted,

The LF anomally is a glitch in my measurement system regards gating the LF artifacts.

I would suggest this horn is a near/mid field device.
I have no experience with the 2310 lens

Now, we have played the with and without lens scenario tonight and without a doubt in this instance the exponential horn alone is a non starter!.

Firstly, we compared in the near near field with/without lens and could not detect any degradation of acoustic transmission.

In the near field secenario without the lens it could be likened to a very listenable 604 duplex with the honky effect as soon as you moved slightly off axis without the lense.

We then changed out the lens a number of times with the complete JBL 4345 monitor system operational.

The effect of the lens was more of the spatial imaging (realism of presentation) than of tonality. Without the lense it as likened to a 1950's radio!!

With the lens in place, the overall accuracy, imaging and sound stage improved remarkably in IMHO.

So from the data presented above, it would appear that response measurements alone are not a deciding factor of system subjective performance.

Clearly, there is much to learn about the application of horn loading.

Theses are the impressions gained from a JBL engineered monitor and may not apply to other specific applications.

Ian

[aust-ted]

Ian

Thanks for the further insights. Your listening experience with and without the lens is most interesting but I suppose comes as no surprise as JBL must have put a lot of thought into the design at the time. Would have been very surprised if the horn functioned better without the lens.

Perhaps someone can explain why the lens contributed so much to spatial imaging. I assume you tried this with both horns in a stereo pair.


I believe your response measurements are valuable, and from my limited capacity to comprehend, probably support Dr Geddes' conclusions.

On the other hand it is probably unfair to consider the 2307 without the lens as a useful horn in its own right. As you probably know better than I there would be a number of other measurements you would have to undertake (eg off axis response) to determine whether a 2307 sans lens is useful for home listening. I am not suggesting these tests be done as it appears from your subjective listening that the off axis results, for example, would probably be woeful.

On the other hand I am confident that a properly designed and used conical horn or waveguide would be a different game altogether. I am hoping that there are other members of this forum who have first hand experiences with them.

Regards
Ted

[Ian Mackenzie]

TEd,

Here are the JBL specson the 2307/2308 combination.

Like most thongs there is a trad off somewhere.

In this case the horn does not have a constant power response with increasing frequency liek the new bi radial horns. Thus it its not possible to equalise for flat on axis and off axis response with this design.

JBL played to this shortcoming when the 4430/35 monitor was development with the then new 2344 bi radial horn in a white paper in the AES in the early 1980's. The design features of this monitor and the new horn were attractive at the time for reasons of studio acoustics and equalisation preferences. Interestingly JBL never marketing the 2344 horn in a consumer design to the home market.

There is much debate as to how important flat power response is in in the home listening environment. I suppose again its a preference thing but the ability to control and direct a sound field with a horn has a lot of merit.

Ted , I look forward to hearing more about your project

Ian

[aust-ted]

Hi Ian

Would not mind getting a pair of 2344 to play with. Perhaps I should try to replicate a pair in wood as I believe Jon Fairhurst has done with his beaut pair that I saw in this thread. I suppose you really need a live one first though to copy accurately.

BTW I believe you forgot to attach the JBL specs on the 2307/2308 to your last post. Would not mind looking at them if possible. They do not appear to be on the JBL pro site.

The relevance of flat power response to the home listening environment is something I am not qualified to comment on.

I would appreciate any advice contributors this forum could provide on it though. I assume the Constant Directivity (CD) horns such as the 2360 and 2380 have a similar objective.

All I can comment is that my 2380A horns coupled to the 2450 drivers provide a pretty good midrange sound but I do not have the experience to compare them to other horns discussed in this thread. I have read in other places both positive & negative comments about the 2380 in the home environment. Virtually nothing about the huge 2360s which must have a poor spouse acceptance factor but which can easily go down to 500Hz . Has anyone on this forum tried them?

I would be happy to keep you in touch with my proposed conical horn project but you will need to be patient as I have yet even to decide on how to attack it.

Regards
Ted

[Ian Mackenzie]

Horns specs

Sorry, operator error.

Ian

[Robh3606]

Hello Aust-ted

One of the things I like about a horn with flat power response is the balance of the speakers does not change as you change positions on the room. I have a Urei based coax 801C center channel that uses an "exponential horn?". Their is some EQ built into the crossover but the majority of the on axis balance is from the result of the increasing directivity of the horn. It has a very well defined listening window. If you move both inside and outside the window you can hear the balance change. On the the 2344's I use on my mains you have to go way off axis to hear this. It is also much less pronounced. I have not compared the 2344 to the 2307/H94 set-up I have but will shortly once I get my cabinets done. I will post my impressions when I do.


Rob

[Guenter]

[QUOTE]Originally posted by aust-ted
[B]Hi

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

Hi Aust-ted, you may want to check this forum for posts by
'Dieter' who has the 2360 horns and appears knowledgeable in that he has successfully, apparently, implemented them in his near-field environment.
I am myself dithering with my home brew system with midbass
and without and am now also - seeing that Dieter seems to have implemented them without problems. I particularly like the aspect of minimizing the system's electronics overall. specifically I believe to implement a 4-way system successfully needs much skill - which sadly I don't believe I have even with my impulse-type measuring system.

- cheers, Guenter

[aust-ted]

Guenter

Thanks Good tip. Had a good read of Dieter's posts to the forum. Gave me some hints re my earlier post about designing passive xovers for CD horns. Will try to contact him to see what his latest developments and listening impressions are.

Dieter's speakers certainly look good and are one way to get an acceptable SAF. I am really surprised that more people on this forum have not used 2360s. They can be picked up cheaply on eBay even thgough I gather they were originally very expensive.

I actually bought a pair on eBay along with a pair of 2450s from a guy in LA but had to leave the horn bells behind because shipping to Australia would have cost much more than the horns were worth. I have the throats and have not completely given up on fabricating a pair from wood.

The difference between Dieter' bass speakers and mine are essentially mine are close coupled, both close to the floor with the top of the cabs less than 2 ft from the floor. I chose this configuration hecause I had spots wide enough and I want to be able to have the horns centred at my ears in the horizontal plane if possible regardless of whether I go the 2360 or conical horn route.

Has anyone tried mounting a HF driver (eg 2405) in the centre of the mouth of a large format horn?

Regards
Ted

[Guenter]

[QUOTE]Originally posted by aust-ted

Has anyone tried mounting a HF driver (eg 2405) in the centre of the mouth of a large format horn?

Excellent idea!! ... never thought of it .... when I get my 2460's I will definitely try to do just that.

cheers

[aust-ted]

Originally posted by 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

Widget

I just found a web reference to a paper describing Charles Hughes " Quadratic - Throat Waveguide which helped spike my interest in conical horns. It is at http://aa.peavey.com/downloads/pdf/qwp1.pdf

Because they are straight sided, I have assumed these waveguides are essentially conical horns.

It also gives a summary of other horn types and constructional details which I am tempted to try.

My apologies if it is well known to members of this forum

Regards
Ted