Comp Upgrade: B&C DE250 or BMS 4540ND?

4540 is a screw fixing, the BMS  equivalent of the DE250 is the 4538. Either this or the B&C will be an improvement on the 1745's. The 1745 is not a bad comp it just seems to break-up early.

For a really nice horn that will not break the bank and would allow you to cross a bit lower have a look at the Faital STH100

I would try either of the above comps on the Celestion horns first.

Tony

Sorry.

Actually i think bms 4524 is what can replace DE250 :-).

Edited by MarjanM - 23 February 2012 at 11:16am

Naah, i just tested it against 4550 and 4552 and it lacked a bit the top high end compared to those two. And even more compared with 4524 which for the cost is a fantastic little bugger.

MarjanM wrote: Naah, i just tested it against 4550 and 4552 and it lacked a bit the top high end compared to those two. And even more compared with 4524 which for the cost is a fantastic little bugger. 4547 looks very promising but i didnt have a chance to use it yet.

Marjan,  it must have been the horn, the 4538 on a sutable wave-guide can sound fantastic, used on a OS type they just disappear and leave only the music.

Give the 4547 a go, you will not be disappointed, they are my > 1.2K "go to" comp driver now. Just a shame about the 3 hole fixing as it means I have to re-drill a lot of horns.

Tony

Although it is a bit of a vague term, what is usually referred to as horn honk, is generally considered to be caused by reflections along the length of the horn. Depending how well the mouth terminates with its surroundings, there can be an impedance mismatch at the mouth. This causes part of the wave to be reflected.

If this is the cause of your honk, changing the drive unit might not be as successful as you would think. Most horns seem to be over optimistic with their specifications with regards low frequency performance. Years ago, the general rule of thumb was to use horns from at least an octave above their cut-off frequency to eliminate honk.

The use of a cut-off frequency with regards horn specifications can be misleading. In horn theory, the cut-off frequency has a specific meaning. Below the cut-off frequency the horn loading is reactive. The cut-off frequency is dependent upon the flare rate; the faster the horn flares out the higher the cut-off frequency.

The fact that a horn has a low frequency cut-off does not mean that it is big enough to operate down to that frequency. With small high frequency horns the performance is more likely to be restricted by the physical size and shape of the horn rather than the actual cut-off frequency determined by the flare rate (an exponential horn with an 800Hz cut-off approx' doubles in area every 3cm)

If you do a search I have uploaded some graphs of the response of a BMS 4524 and the B&C DE250 on a B&C ME10 horn. This is rated as having a cut-off frequency of 1K5. The measured response shows that 2K5 is a more realistic cross-over point. Both drive units exhibit a peak at 4K which is absent from the measured response on a larger horn.