I know this has been up before but anyway. Do cast aluminium horns have any sonic advantages (besides mechanical and esthetic) over plastic ones (ABS+fiberglass)? (I can see a potential "ringing" resonance problem with aluminium horns which maybe can be fixed with sufficient damping or????).

My project at hand is upgrading a pair of speakers (Eminence Kappa 12 + Motorola KSN-1141) with a compression driver and horn. I have been eyeballing the P.Audio BMD-440 (http://www.paudio-europe.com/products/db_product_2_6_bm-d440.htm) paired with a B&C ME45 horn (http://www.bcspeakers.com/compproducts/horns/me45.htm). The choice of driver and horn in this case is limited to what physically fits my boxes (the CD must have a diameter of less than 120 mm, the horn have to fit nicely on the baffle). Does anyone have comments on P.Audio stuff or even the CD/horn combo?

I was thinking of using a third or fourth-order network around the recommended crossover frequency of 2.2 kHz. It seems to me like most people are using third-order rather than fourth-order networks for this kind of thing. As an engineer but with limited actual audio experience I can see the time-domain benefits of 18dB/oct compared to 24dB/oct and also the potential problem of matching 2 coils and 2 caps in the latter but from an experience point of view, what tends to be the best for most applications and why? The woofer LP network is an impedance corrected ("Zobel") 12dB/oct Butterworth @ 2kHz.

Thanks
Magnus

Cast aluminum horns are generally much more resonant than properly designed horns made from less resonant materials (like plastic and wood), and will usually benefit significantly from efforts to damp them. Once damped, aluminum horns have a sonic signature that is a function of the horn shape/flare, the compression driver and the interaction of the two, just like good plastic and wood horns. I would suggest that you stick with horn/driver combinations that have an established reputation for performing well, and that will meet the particular needs of your application. Is this for a home music system or a commercial pro-sound application? How much amplifier power will be used?

If this is for a home system, you might consider a simpler, lower order network. At your crossover frequency, the Eminence horn/driver combination used in the Pi Theater 4's would work quite well at relatively low cost. Unless you are into head banging or live level train/helicopter sound effects, this combination can be used safely with a second order network (at 2 kHz). On the other hand, if you are more interested in getting there and less interested in how you get there, you could just use the Pi network that is the closest match to your drivers and adapt as needed with help from the folks on this forum.

Regards,

AstroSonic

thanks for your thoughts. I originally designed these speakers like 5 years ago as my "party speakers" for moderate SPL:s. I mostly use them for home listening and thus normally just a few watts of power at its most. However now and then a friend borrows them for his band, but I would no, rarely if ever are they cranked up all the way like pro speakers.

I have looked at the Pi series (looks very nice, but perhaps not available in Sweden!) the problem in this case is that the Eminence driver will not fit. That is because the boxes are divided into two sections with separate LF and HF chambers and the HF chamber is only 120 mm high so any CD must have a diameter of less than that.
But well I guess you are right, sticking with a proven driver/horn combination would of course be the best.

Regarding crossovers, as an electrical engineer that is the part of speaker construction I like the most. I usually use MATLAB/SPICE for simulation and a spectrum/network analyser for verifying the results so building a very accurate high-order crossover with any characteristics is no problem (and actually, part of the fun!) although at my normal power levels I guess a second-order network would perhaps be enough.

/Magnus

From what I remember reading - theres no sonic advantage to aluminimum. Some do ring, and they should be heavily damped. But not all do, such as when the manufacture has made the mechanical resonance lower than the flare rate.

The P.Audio stuff is pretty damn good IMO. I own a pair of P.Audio PA-D45's, and I love em. Even though I havn't compared to other comp drivers - only direct radiators, I can say they really are great. The BM series your looking at is also one thats very good for a "flat and open" sound using those descriptive words, but nonetheless thats what you'll get. I doubt you'll be disappointed.

Sorry I dont know anything about the B&C horn. Perhaps do a search of this forum I think I remember seeing it somewhere before.

High order networks reduce destructive interferance between point sources. The odd ordered ones tend to minmize anomolies caused by the time domain, but theres nothing wrong at all about 4th, 6th order networks etc. Just keep them high order and dont worry about phase shift too much from these as the max phase shift is when driver is already offline.

Hope I've been able to help out some.

Adrian

Magnus