Distance between compression driver / horn and mid |
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Teunos
Old Croc Joined: 23 November 2008 Location: The Netherlands Status: Offline Points: 1799 |
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Think you have got the main points listed very clearly. One sidenote i would make on this post, is that when you get slightly above or below the crossover frequency, especially above the actual crossoverpoint, with typical x-over slopes, the problem will be there as well. It is not just a single frequency that is affected, but actually a band of frequencies around the crossoverpoint. If you make the slopes steeper, the phase changes around the xover point will become much bigger off axis then when the slopes are less steep. The suckout in amplitude off axis where the primary null is located will then become deeper, but over a smaller interval since the slopes are steeper, and indeed the source that is outside of its passband will reproduce less sound already. So steep slopes, you will have a suckout that is pretty intense, but along a narrow frequency content. With verry slow slopes, you will have suckout that is less intense just outside crossover, but the notch will be much wider and comb filtering can also occur way outside the xover region. Therefore, both very steep slopes and very slow slopes are not that great. 18dB slopes is generally sufficient to crossover any driver imaginable. If you increase the distance between the drivers, the angle at which the cancellation will occur will decrease. With the calculated example of Pfly at 20-30 degrees, this may not sound like a bad thing, but consider that this means that at this angle, the xover frequency and the region around it, will be completely NOT reproduced. (well, with directivity and all, some sound will still be reproduced). If you thus put your tops on your subs and angle them down about 10 degrees to give the front row better coverage, the people halfway around the room will experience a nearly completely missing band of frequencies, deadsmack in the center of the important hearing range. Increasing the distance simply makes the problem bigger as the null shifts closer towards the forward axis. Increasing the xover point again makes it worse as the phase change around crossover will grow faster due to the shorter wavelengths involved. Now this whole theoretical derivation that Pfly has given, and i support, basically means;
So yeah, if you can, move the logo. |
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Best regards,
Teun. |
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AndyWave
Registered User Joined: 30 March 2008 Location: Finland Status: Offline Points: 380 |
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Why don't you put the logo on the middle of the 12" grill. It would act as a high range diffuser. That would help having more identical radiation patterns between drivers trough crossover region.
How many times I have used gaffatape on my guitar cabinets to achieve the same. |
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torturing electrons since ......
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Cheif_Stringer_
Registered User Joined: 26 April 2016 Location: Northumberland Status: Offline Points: 119 |
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Thanks for the advice everyone, ive decided im gonna build the seperate hf and low boxes as meantioned before, and test them close together and with abit of distance and see what i make of it, listening to the sound in various areas, if i do add the logo between them i will keep the distance less than i said but yeah im gonna test it, it means buying an amp and processor before finishing these cabs but itll be worth the wait since there is some concern there, if i think theres a big enough difference in sound ill not add the logo, if i notice it but its not a massive deal ill use the logo with the less distance (i could make it 70mm rather than 85), ill be building two cabs at the same time two so i can play with the angles on them too etc.
The idea i have had for the logo will make the midtops look really special imo, im not gonna try too hard to describe it with words but itll be a bold logo thats cnc'd not just like a little one what would look fine anywhere, so again im willing to make a compromise to sound for it, just not a one that defeats the purpose of using such quality components, so yeah thanks to all the comments ill do something i should have wanted to do but wasnt going to and thats do some testing first, thanks people :) |
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Cheif_Stringer_
Registered User Joined: 26 April 2016 Location: Northumberland Status: Offline Points: 119 |
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Btw just while were on the topic am i right in saying that the most ideal place for a hf among to mids would be in the middle of them?
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Steve20131
Registered User Joined: 28 July 2013 Location: Northants Status: Offline Points: 411 |
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Lol no 2x12 together is so they couple and help dispersion, always hf above or to the side if it's a array
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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Well, it depends. Plenty of mid / top / mid boxes out there - both in vertical and horizontal planes. As has been said, dual drivers means they're different distance from HF so cancellations and such will be made worse than having drivers either side of HF and at equal distance. If HF is crossed sufficiently low, then they will still couple in varying amounts up to crossover frequency so long as they are workig within 1/4 wavelength distance. Edited by toastyghost - 25 September 2016 at 11:47pm |
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Steve20131
Registered User Joined: 28 July 2013 Location: Northants Status: Offline Points: 411 |
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But surely for the 12's to be more than 1/2 wave apart means a crossover too low for a 1.4" cd. If they're chassis to chassis you can squeak 1.5-1.8k without too much honky sound.
Personally I'd rather wideband mids and crossover distortion than polar problems or going 4 way. But yes toasty ghost is correct it depends lol
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bob4
Old Croc Joined: 29 February 2004 Location: Finland/Germany Status: Offline Points: 1843 |
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http://https://en.wikipedia.org/wiki/Midwoofer-tweeter-midwoofer |
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Claer
Registered User Joined: 18 September 2012 Status: Offline Points: 161 |
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Please stop saying you're willing to compromise sound for looks, especially if you are investing a lot of time and money. Sound first Sound second Sound third Then looks An awesome logo will just make them more memorable as poor sounding speakers |
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Cheif_Stringer_
Registered User Joined: 26 April 2016 Location: Northumberland Status: Offline Points: 119 |
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Well i am willing to compromise 'some' sound quality for looks to 'some' extent, im not willing to make something that sounds bad because i think it looks good either, thats why im going to do some tests before deciding, to find out how much of a difference there is and go from there, im not trying to build the very best sounding system possible within a certain price bracket, and ill no doubt be on here asking about different testing methods or whatever when i have to cross that bridge.
Im not trying to copy their design just have a similar style / placement logo with abit of a different approach but the system i heard that made me wanna build a system with front radiating midtops was the Electrikal Sound System at a festival this year using thier smaller front radiators, and im limited in expereince but i think they sounded pretty f**ken good, would there sound better if the horn was closer? according to answers here yes, but the system wasnt anywhere near bad, at all. http://www.thebongoclub.co.uk/wp-content/gallery/electrikal-end-of-fringe-13-party-white-belly/Electrikal-48-of-117.jpg I am investing what for me is alot into it and i appreicate your concern buddy, again, im going to do some tests and that will tell me what happens next, its not something i was gonna do before (stupidly), but until then im just waiting, thanks mate |
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bob4
Old Croc Joined: 29 February 2004 Location: Finland/Germany Status: Offline Points: 1843 |
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i don't want to sound condescending, but for two pages now people have tried to explain the physics of why your idea is acoustically not viable. Some of those people are sound reinforcement professionals with years/decades of experience. THIS:
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toastyghost
The 10,000 Points Club Joined: 09 January 2007 Location: Manchester Status: Offline Points: 10919 |
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The Electrikal tops are a rear ported dual 10" box using high end Faital drivers and horn - I did their settings and acoustic centre was lower than the logo and gain / filter placement was adjusted to compensate
Edited by toastyghost - 05 October 2016 at 12:20pm |
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