rog statement about 1850 horns

PD 184 driver instead of the PD 1850 driver in short folded horns

Drivers like the PD 184 will work in a short folded horn because the cab is not really a horn. For the driver to be properly loaded by a horn means a horn length of over 5.5 feet, something none of the Turbo or Funktion bins have. When the horn is less than 5.5 feet long we have what I call a horn assisted design. Basically the horn just adds a bit of gain from around 80 to 150 Hz, the cab will produce notes above and below these frequencies, just at a lower volume. You want a driver with a low resonance a powerful motor system and good damping, the PD 184 has all of these. Most of my short horn designs will work down to 50 Hz because I design them to be sealed boxes first that just have a bit of extra gain and kick from the horn in the 80 to 150 Hz range. Below the horn cutoff most of these short horns will still produce a useful output down to the cutoff point of the sealed box. It's a hard thing to design, do you go for a driver with high EBP that you know will work well in a horn and have the output from 80 to 150 Hz controlled and fast, or do you use a driver with a lower EBP and make use of the lower sealed box cutoff point. Drivers like the PD 184 are ideal because they sit somewhere in between the two. They are reasonably controlled and fairly fast and also have good extension. The 1850 has a higher resonance and more powerful motor system, so has a much higher EBP. This will always make the 80 to 150 Hz range more prominent when it is used in a short horn, hence the sound will have more grunt. If you change your 1850 drivers for 184 drivers you will get that smooth Hi Fi sound and a lower cutoff point, but you will lose quite a lot of efficiency, will gain more power compression and not have such a high power thermal limit. So all in all you might lose up to 3 dB per cab of SPL. Whether or not you can live with that only you know, but I guess not seeing as you said you already don't have enough power to drive the cabs with and would like an even higher SPL from them. If you have lots of these short horns, like over 8 per stack then the effective horn length will appear to be longer, so the use of a driver like the 1850 will pay of because the stack will work as a true horn and so need drivers with a high EBP. You will find that that most of the grunt to the sound will disappear if you can use big enough stacks. If you used the 184 driver in very large stacks then the sound may become very slow and heavy. So, it might pay to keep the 1850 drivers but just use more cabs per stack to achieve a bigger and longer horn, because if you go with the 184 option then you will have to use a lot more cabs anyway to get the desired SPL, so you might as well use the 1850 if you have a bigger stack and have a lot higher SPL.

Bass drivers for horns should have an EBP of over 130, how important is this?

I did say that a driver that would be good for use in a horn usually has an EBP (efficiency bandwidth product) of greater than 130. This is not the rule though, it is only a guide. EBP is Fs divided by Qes and gives a rough approximation of how well the motor system can control the cone. It doesn't always follow that high EBP figures automatically make the driver suitable for horn loading, there are so many parameters that dictate which driver to chose for a particular horn and so many different horns for different jobs.

Take the 186 horn on this site, the best driver to use for this horn i.e. the driver it was designed around, is the PD 1850. You have to make the rear chamber smaller when fitting this driver as the plan shows measurements for the PD 186 driver. With the PD 1850 fitted the cab produces one hell of a bang, the transient response is tight and the sound fast and detailed in the upper bass range, but the sound has a hard edge that can lead to listener fatigue early on. If you want the loudest noise from that horn fit the PD 1850. If you want a sound that is a lot more listenable then fitting a driver with a lowish EBP improves things. The PD 186 has an EBP of less than 100, so should not work too well in a horn loaded situation, but by making the rear chamber slightly larger than is dictated and opening the throat up a bit the PD 186 will make beautiful noises in that box. It will not ever be as loud and will never have the detail in the upper bass range and will not have the transient response of the PD 1850 in this horn, this is because the stronger motor system in the PD 1850 is better able to move the cone against the column of air in the horn. So the lower EBP PD 186 will not be as fast because of it's lack of ability to control the cone well, but certainly makes for a really good sound. You also asked whether the sound of a driver with an EBP of less than 100 in a horn would sound less Hi Fi, well it depends what you call Hi Fi. For me the PD 186 with it's lower EBP in a horn sounds more Hi Fi because the sound is smooth, warm, doesn't have too big a peak around the horns cutoff point and has a lower F3 than the driver that should sound better in that horn. The PD 1850 does not sound as Hi Fi to me in the 186 horn, you really now that you are listening to a horn, it's a more in your face sound and draws attention to it's self. The PD 186 doesn't do this, it integrates well with what ever mid top cabs you are using and doesn't sound like a horn. So, which driver do you chose, if it's for a PA where you want the biggest noise for the size of enclosure then higher EBP drivers tend to win out. For the home where 130 dB is not so important, then for me a lower EBP figure wins out.

With short folded horns, or bandpass horns like the HD15 the effect is even more pronounced. A short folded horn with horn length of around 85 cm and a mouth area of 3300 sq cm, so a horn with an 85 Hz cutoff (quarter space) will sound really hard with high EBP drivers in them. The PD 1850 will rip your head of in one of these bins, but lower EBP drivers (though not as low as the PD 186) will smooth the sound out and make it more listenable.

So as I said EBP is not the final word on whether you should put a driver into a certain horn or not, but for a very quick reference will stop you from choosing a driver with a very weak motor system that will not drive the air column at all well. For 12" drivers in horns for mid use an EBP of over
180 is a good starting point. You will not find many 12" drivers that are this tight, so to save you looking EV has some that are around 180 and there are 3 PD 12" drivers that are above 180. One has an EBP of 235 and it does sound awesome in a horn.

Edited by Keen - 31 July 2024 at 12:05am

Why do you even bother with that completeley outdated design?

Many better free designs in the internet.

Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713

https://forum.speakerplans.com/scoop-design-with-hornresp-throat-size_topic9518_page2.html#top

Check this link.. he's talking about the number of scoops he had in mind when designing

Bogdan85 wrote:

https://forum.speakerplans.com/scoop-design-with-hornresp-throat-size_topic9518_page2.html#top

Check this link.. he's talking about the number of scoops he had in mind when designing

Thank ypu for the pointer, interesting thread!! Clap