Compression Drivers and Conical Horns

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Does anyone have experience with building DIY conical horn speakers using compression drivers? I am looking into building something like the OMA Imperia for my next project and have started researching compression drivers but don't know enough about it to make an informed decision.  I can find plenty of pro compression driver units on eBay from brands such as JBL, Beyma, B&C but suspect these drivers are built for reliability and not hi-fidelity.  If I look at RCA and Cogent style high end compression drivers these are phenomenally expensive like £2,500 a pair. 

My question is are there any alternatives with decent hifi performance at a reasonable price point and where to source them.

Second would be any advice or software to understand the throat dimensions and conical horn dimensions to arrive at a coherent sound output.

Has anyone achieved a good quality sound with conical horn speakers and could they recommend a DIY build thread to follow.


Edited by MelodyMan

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I am far from knowledgeable on the specifics of designing such a system but have a bit of experience to offer that hopefully helps. Firstly, I think compression drivers done well are the road to audio nirvana. if you want a better result you have to do something different, and for me, that's where CD's come in. I haven't heard a conventional system that can touch them for sheer dynamics, clarity and realism. I first played around with a TAD system about ten years ago now and what I heard from my DIY efforts was equally awesome and disappointing. I could hear the potential but completely lacked the skills to engineer out all of its shortfalls. This experience had led to me having a system built, you can read about it on this thread if you haven't seen it:

The Symphony uses a conical horn of Lenards design, I understand it was created by two very knowledgeable audio engineers and have no idea if modern software exists that can model such a horn. Probably so but who knows how effective it is in reality. You could buy a TAD or JBL horn clone, that would get you good sound with no risk. Conical is a good choice as it limits floor and ceiling interactions. Comprehensive testing of round vs conical horns for my system show for the given space constraints, the difference is negligible and of no consequence.

Good luck, it will be a fun project if you decide to take the plunge.


Edited by Mondie

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BMS compression drivers are very good, 

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On ‎07‎/‎04‎/‎2018 at 11:29, Mondie said:

Hi Mondie, thanks for that advice, I took a look at your project very interesting and went on to learn all about Lenards systems and really like their 4 way approach to sound reproduction makes a lot of sense.  That has inspired me to bring my own 3 way design up to 4 way to better cover the frequency range. I will keep an eye on your thread to see how the finished product looks, I love the look of your drivers all stacked up ready to rock, serious components those. Good luck. 

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I wouldn't agree that JBL compression drivers are PA only - if you go on Lansing Heritage you'll see that many of the classic "blue face" JBL studio monitors used the same compression drivers. If you do decide to try JBL drivers, try and have enough left over of your budget to install Radian diaphragms - I recently installed some in my pair of Urei 809s (compression driver is JBL 2416H) and they moved from very good to quite magical.

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I posess a set of 3 conical horns - all 'petal' constructed ( each petal glued to its neighbour and then a band of bracing slats are glued to the outside of the conical midway along it like the bracing on a barrel). The build (its DIY of course) was done by Speedysteve now found on Art Of Sound and residing in the New Forest.

The upper horn takes a 1" JBL CD, the midrange tales a 2" BMS driver and the bass horn (whose mouth has a 3 ft diameter) is loaded with Vitavox AK157 drivers. I replaced the 1" horn with a 1.5" JBL 2435Be driver on a smaller tractrix horn. This driver was specially imported from the US. The BMS unit Steve and I compared directly with his Modified Vitavox S2s on the same horn (or waveguide) and was within shouting distance of it SQ wise. That means its very good. Its the BMS 4592. (There's a coaxial version with a tweeter firng down the centre.)

The JBL slot tweeter (the 2405) was the basic tweeter in some of Kevin Scott's designs and a highly modified version I believe is still in the Vox Olympian - Im certain that the 2405 is the tweeter in the lesser LV 'Scout' model.

Beyma make good quality compression drivers as well. The creme de la creme brand is TAD - a japanese high end manufacturer. Thay are expensive hoever. It has been known for enthusiasts to buy TAD drivers with knackered diaphrams and turn to Radian diaphrams for little loss in clarity.

So, answering your questions in turn:

Existing 'PA' brands are good enough if you are selective and high end brands such as TAD and Vitavox (S2's for example) are pricier and better alternatives.

Second - Horn response is where you will find horn length, mouth size, and horn calculations based on the chosen drivers spec. Only certain types of bass driver suit horns. You will need to research that.

Speedysteve's build should be archived on this site under the title Big Boy 5 way horn system. (And very detailed and engaging it is.)

Steve himself wont build you these Im pretty sure. But, if you canget hold of him (and its a big 'but') he will offer help and advice. He is an excellent engineer and 'bespoke' craftsman.

My system will soon be up and running - look out for a Record Day/Bake Off in the next 6 months. I did demo it at Scalford a few years ago and there may be some pictures left in the Scalford archive. I used builders' podium steps as 'stands'.

Good luck with the build.


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