Horn-loading the "new breed" of pro sound 6.5-8'' drivers

[Swedish Chef]

I have been eyeballing some rather new drivers from Beyma and B&C (especially Beyma 6MI90/100 & 8MI100 and B&C 6PEV13 & 8PE21) and wonder if anyone has any experience with them.

I am planning for a front-loaded conical midrange horn for (mostly) home use in ca the 400 Hz - 1.5 kHz range. Will use a JBL 2205/2226 (and perhaps a Fane Studio 12B) below that and Beyma CP385/Nd + JBL 2405 to cover the HF range. The whole system will be active powered and although I will probably end up using a digital EQ like the Behringer Ultracurve smooth fq response on and off axis is pretty much one of the goals.

The B&C 8PE21 look very interesting 'coz they use a copper shorting ring like the JBL's to reduce distortion.

Any input appreciated!

/Magnus

[rcavictim]

Magnus,

Great idea. You want a set of solid hardwood horns like the 450 Hz black walnut ones made for 8" drivers that I manufactured last week. I have an adaptor on them now to play with a 4" W4-656S Tang Band driver but am looking for a nice 8" to try as well. I was looking at the Fostex FF225K as a possibility.

[synergy]

currently developing some ideas along these lines for my PA system

there's a 6.5" from PHL that looks good (modelling within 1dB 300Hz - 5KHz)

and i've just found another from ciare which i've not had chance to do anything with yet

on the 8" front there's also a neo driver from P.Audio which has a similar response to the PHL

they all need a really small rear chamber (0.5-1L) practically making it a sealed unit so i've got to come up with a DIY way of doing this but things look promising

i'm covering a wider bandwidth than you cos i don't want a crossover in the vocal range but i'd be interested in hearing how you get on

dave

[Swedish Chef]

rcavictim (aren't we all!),

Awesome horns! While I have access to most of the stuff one would want for building electronics I have nowhere to practice my woodworking skills so solid hardwood horns are unfortunately out of the question for now. Planning on building the horns out of plywood and/or the "Edgar" way.

Dave

Will have a look at the stuff from PHL too. I am usually more worried about crossing a driver too high (breakup distortion) rather than crossing in the 300-3000 Hz range but both sides have their merits. And I am opting for a home system rather than full-blown PA so crossing the compression drivers a little lower isn't much of a problem.
It would sure be nice to hear more on your design!

/magnus

[synergy]

yeah a big part of my problem is at the levels we play crossing low on a comp driver starts sounding really harsh going as high as this on a paper driver will hopefully allow me to play a 1" comp from there all the way up

i just hope using a 6.5 will at least allow me to get reasonable distance up the scale before breakup problems arise and figure i'll deal with them at the time

i'm yet to cut any wood in this (finance as always!) but i'm willing to give it a go and see what happens as i'm really still in my infancy when it comes to speakers and will learn a lot from doing it

[Tim Moorman]

Hey Guys,

I can't offer much with regard to any of the newer mid units out there other than a few observations.

If you can find them, the JBL 2123 10"(discontinued) may offer a lower crossover from, say 250 Hz up to perhaps a 1" at 1200 cycles. The unit is dead flat to almost 4K Hz at about 100dB.

The little JBL LE-5 5" was used extensively and still sounds good horn loaded.

From the ordinary to sublime, here is Adrian Mack's horn design of both tractrix and conical expansions for the lowly Eminence Alpha 6. Nice work here from a design standpoint:

http://www.geocities.com/adrian_mack/homepage.html

The newer 6.5" - 8" designs that look interesting to me are the B&C, Beyma offerings you mentioned, S. Chef, plus a couple from P Audio. Namely, the new product HD series MD 720, and the neo SN-8MB (bottom of SN page). The SN-15MB has amazing response for a 15"(midbass horn?), and the "new products" 21" woofer is interesting.

http://www.paudio-europe.com/products/db_1_12.htm

http://www.paudio-europe.com/product..._53_md-720.htm

For great looking 15", this BMS looks as well made as they come:

http://www.assistanceaudio.com/12_L15N620.html

The JBL 2226 15" is still a real workhorse with very low distortion.

I use 2" compression drivers for mids, 15" straight 80 Hz midbass, 1" HF horns. Subs below.

From an ideal point of view, I think the Unity horn design by Tom Danley has a lot going for it. Have a look at the Yorkville-Licensed version with twin 15"s as direct radiators, but with 3 mids and a single 1" Hf unit on the same horn:

http://www.yorkville.com/products.as...&cat=38&id=268

Solves a lot of problems this way in terms of dispersion.

Hope this will give some food for thought.

Tim

[Tim Moorman]

rcavictim,

I just wanted to add that your round horns turned from walnut are truly beautiful. Just killer good looks and my sincere compliments.

I'll be very interested in the outcome, once their placed in the system with the 8s.

Question for you: Did you use a tractrix flare?

Also, you probably know this already, but mounting the TB on the horn my cause some irregularities in response from the mouth to throat ratio changing. Still, its fun to swap stuff in and out on the same horn.

Tim

[Swedish Chef]

Tim,

I followed the development of Adrian's midrange horns over at Pi Speakers/Audioroundtable.com and they were pretty much what inspired me to go with my own!

The Unity horn looks very interesting too. Pretty much the only disadvantage as I see it to these "big" systems where you use a 1'' or 2'' compression driver and throw in a 12'' or 15'' to cover the bottom is off axis response. It can be pretty messy and thus not very good in small reverbant rooms. So my goal here is to have as controlled dispersion and off-axis response as possible.

I pretty much love all of the JBL Professional drivers (who wouldn't?) but they can be pretty hard to get in my small cold northern country where very few people have discovered their performance.

I can get Beyma, B&C and P. Audio drivers at killer prices from the UK (www.proaudioparts.co.uk). And now it seems that at least B&C have incorporated the copper shorting ring in their designs possibly lowering distortion to be on par with JBL.

Which 2'' and 1'' compression drivers are you using?

/Magnus

[Tim Moorman]

Swedish Chef

The 2" are M200 Community, and the old 2440 JBL. BTW, the 1.4" Altec 288 and 290 are good, too, on the right horn(big), maybe better than the JBL. All need help above 8K-9K Hz, the Community above 4K, though they go to 8K.

1" drivers are TAD 2001 and Altec MR902. The 902 has a small peak around 2K Hz, but pretty good on average. The TAD more extended to about 16K.

Recently, a friend who's tried them all, it seems, changed to the Beyma CP21F, a wide dispersion compression tweeter. He finds it very nice sounding. Maybe it's because of the unit 's wide dispersion (140 degree), but it has eliminated some of the harshness he found present in other types.

I also modeled a Selenium Pro 15", the SW1P (on their site in the subwoofer index, which it is not), but this looks like a good bass provider for high SPL in a small box (100l).

Copper shorting rings help keep inductance in check and extend response. One reason I posted about the new neo BMS 15" woofer is attention to these details. Low distortion.
Their 4590/4592 2" coaxial compression drivers look good, too, go low, and offer a lot of bandwidth for the money. Probably a good choice.

The unity has both the 1" high freq driver and the 3 cone midrange drivers arrayed on the same horn, so the mids can be time (phase) aligned with the highs. Nothing else does this, currently, and uses the same horn. Theoretically, the blend should be great and the dispersion of the mid/high horn is matched with the 15".
I have dual JBL 2226 woofers in the same box (JBL4648), and they match up fine at the crossover (500 Hz) for the 2" mids.

For home use, the differences between the JBL products and others are probably small, so long as both have similar response and phase. I wouldn't worry about that too much. Pro applications are different, where they are under severe stress most of the time. But if you handle a TAD or JBL product, you see immediately why the cost is high(too high, maybe). Very well made.

I remember a post on AA High Efficiency forum where Tom Danley(unity designer) made a few suggestions to Adrian for his design, namely using the conical flare, and properly sizing the rear chamber and throat/mouth ratio. Came out well.

Tim

[Swedish Chef]

Yes, the Beyma CP21F is good - and it should be since it is almost a copy of the JBL2405 which is excellent. While some but certainly not all 1'' drivers sound good in the top octave I find the narrow dispersion kind of irritating. I found a pair of the 2405 second-hand for $190 and have not regret it! Give it a try if you can!

And yes, the quality that goes into a JBL pro driver is just amazing.
Regarding the conical flare, I was thinking Tractrix at first just like Adrian. But his findings along with that of several others (Wayne Parham for example) got me into the conical flare for a midrange horn.

/Magnus