fenderiko Posted October 5, 2009 Share Posted October 5, 2009 Hi Folks , Just a question which Im raising only to satisfy my curious mind as Im not purchasing anything new in the near future . can any of you tell me the difference in sound between rear port amps and front port ? ? ? I am not talking about the physical difference as I know that the ports are located in 2 different places but is there any difference in sound ? ? thanks very much you clever ones , Rache, Quote Link to comment Share on other sites More sharing options...
alexclaber Posted October 5, 2009 Share Posted October 5, 2009 [quote name='fenderiko' post='617279' date='Oct 5 2009, 12:21 PM']can any of you tell me the difference in sound between rear port amps and front port ? ? ?[/quote] Assuming its correctly implemented, then it doesn't matter whether the port is on the front, back, side, bottom, etc. Alex Quote Link to comment Share on other sites More sharing options...
51m0n Posted October 5, 2009 Share Posted October 5, 2009 Well to a point I agree with Alex, However a rear port does rely on a certain amount of space behind the box to work well - if you work in small venues alot and squeeze you cab right against a back wall the a rear port can suffer as a result.... Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted October 5, 2009 Share Posted October 5, 2009 [quote name='alexclaber' post='617296' date='Oct 5 2009, 12:31 PM']Assuming its correctly implemented, then it doesn't matter whether the port is on the front, back, side, bottom, etc. Alex[/quote] Fairly sure putting the port on the botom is going to fail the implementation bit automatically. Quote Link to comment Share on other sites More sharing options...
fenderiko Posted October 5, 2009 Author Share Posted October 5, 2009 already replying !!! wow you guys are good !!!! thanks alot for that , However , if there is no difference in sound then why the option is there in the first place ? ? ? why bothering with such design ? a good example would be the Aguilar cabs (GS and DB ) would you suggest that there is no difference in sound between the two with relation to ports ? Alex , to your opinion, are those ports badly placed ? ( or ports in the mass production cabs for that matter ? ) (apologies for being a total ignoramus ) R Quote Link to comment Share on other sites More sharing options...
alexclaber Posted October 5, 2009 Share Posted October 5, 2009 [quote name='51m0n' post='617328' date='Oct 5 2009, 12:46 PM']Well to a point I agree with Alex, However a rear port does rely on a certain amount of space behind the box to work well - if you work in small venues alot and squeeze you cab right against a back wall the a rear port can suffer as a result....[/quote] A rear port only needs a port diameter behind it to work well and most heavy-duty speakon cables force you to give the cab that much clearance at the back - literally only 3" or 4" is required for the vast majority of cabs. [quote name='Mr. Foxen' post='617342' date='Oct 5 2009, 12:53 PM']Fairly sure putting the port on the botom is going to fail the implementation bit automatically.[/quote] With feet of the correct height you get a lower tuning with less internal port volume. I've seen this used on one nice DIY bass rig. Alex Quote Link to comment Share on other sites More sharing options...
obbm Posted October 5, 2009 Share Posted October 5, 2009 [quote name='alexclaber' post='617355' date='Oct 5 2009, 01:02 PM']A rear port only needs a port diameter behind it to work well and most heavy-duty speakon cables force you to give the cab that much clearance at the back - literally only 3" or 4" is required for the vast majority of cabs.[/quote] Except when you're playing outdoors old boy, when your LF content disappears into the field behind you. Quote Link to comment Share on other sites More sharing options...
fenderiko Posted October 5, 2009 Author Share Posted October 5, 2009 "With feet of the correct height you get a lower tuning with less internal port volume. I've seen this used on one nice DIY bass rig." Ive seen a clarus or acoustic image ,, or one of the little ones, with a port at the bottom , , Quote Link to comment Share on other sites More sharing options...
fenderiko Posted October 5, 2009 Author Share Posted October 5, 2009 [quote name='obbm' post='617362' date='Oct 5 2009, 01:06 PM']Except when you're playing outdoors old boy, when your LF content disappears into the field behind you.[/quote] so you are suggesting that cabs with a rare port are no good for outdoors gigs ? ? ? surly the amp/cab makers would have thought of that when designing the cab ? ? please correct me if Im wrong R Quote Link to comment Share on other sites More sharing options...
Dubs Posted October 5, 2009 Share Posted October 5, 2009 (edited) With a poorly designed rear-ported cab there is the possibility for slight cancellation, which basically means it's gonna have a lower SPL within a certain frequency range than a front ported equivalent. I'd guess this is unlikely with modern cab designs though. Edited October 5, 2009 by benwhiteuk Quote Link to comment Share on other sites More sharing options...
alexclaber Posted October 5, 2009 Share Posted October 5, 2009 [quote name='obbm' post='617362' date='Oct 5 2009, 01:06 PM']Except when you're playing outdoors old boy, when your LF content disappears into the field behind you.[/quote] No, that's completely wrong! All cabs lose bottom when outdoors, wherever their ports are located or if they're sealed or horn or bandpass etc. LF output is omnidirectional due to the large wavelength vs source size. Alex Quote Link to comment Share on other sites More sharing options...
alexclaber Posted October 5, 2009 Share Posted October 5, 2009 [quote name='benwhiteuk' post='617425' date='Oct 5 2009, 01:58 PM']With a poorly designed rear-ported cab there is the possibility for slight cancellation, which basically means it's gonna have a lower SPL within a certain frequency range than a front ported equivalent.[/quote] What's your thinking behind this? Alex Quote Link to comment Share on other sites More sharing options...
obbm Posted October 5, 2009 Share Posted October 5, 2009 [quote name='fenderiko' post='617372' date='Oct 5 2009, 01:11 PM']so you are suggesting that cabs with a rare port are no good for outdoors gigs ? ? ? surly the amp/cab makers would have thought of that when designing the cab ? ? please correct me if Im wrong R[/quote] Just personal experience with the pair of Ashdown Mini 4x8s I had 6 years ago. Fine indoors, especially in front of a wall. Useless outdoors in the middle of a stage. That's why I sold them. Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted October 5, 2009 Share Posted October 5, 2009 [quote name='benwhiteuk' post='617425' date='Oct 5 2009, 08:58 AM']With a poorly designed rear-ported cab there is the possibility for slight cancellation, which basically means it's gonna have a lower SPL within a certain frequency range than a front ported equivalent.[/quote]That would require that the distance from the cone on the front of the cab to the port opening on the rear of the cab be 1/2 wavelength at the cab resonant frequency. As that amounts to some 8 to 10 feet it's not a major consideration. Quote Link to comment Share on other sites More sharing options...
alexclaber Posted October 5, 2009 Share Posted October 5, 2009 [quote name='obbm' post='617458' date='Oct 5 2009, 02:27 PM']Just personal experience with the pair of Ashdown Mini 4x8s I had 6 years ago. Fine indoors, especially in front of a wall. Useless outdoors in the middle of a stage. That's why I sold them.[/quote] That's simply because those cabs don't have much ability to move air (cone area x excursion) and therefore really need the boundary reinforcement to cope. Common problem - amplifying bass outdoors is tough! Alex Quote Link to comment Share on other sites More sharing options...
obbm Posted October 5, 2009 Share Posted October 5, 2009 [quote name='alexclaber' post='617481' date='Oct 5 2009, 02:42 PM']That's simply because those cabs don't have much ability to move air (cone area x excursion) and therefore really need the boundary reinforcement to cope. Common problem - amplifying bass outdoors is tough! Alex[/quote] Thanks. Point taken and understood. Quote Link to comment Share on other sites More sharing options...
Dubs Posted October 5, 2009 Share Posted October 5, 2009 [quote name='alexclaber' post='617435' date='Oct 5 2009, 02:04 PM']What's your thinking behind this? Alex[/quote] I was told it once by someone who I thought new what they were talking about. I guess it's not the case Quote Link to comment Share on other sites More sharing options...
jonny-lad Posted October 5, 2009 Share Posted October 5, 2009 Isn't one of the main benefits of a rear port that the port doesn't take up any space on the front of the cabinet?...although this doesn't take into account how well designed the cabinet is. Having said that, I've heard plenty of rear ported cabinets that I like the sound of, like the Bag End 1x15 that is really compact and seems to just have a circular hole cut in the back right behind the speaker with no tubing. Quote Link to comment Share on other sites More sharing options...
alexclaber Posted October 5, 2009 Share Posted October 5, 2009 [quote name='jonny-lad' post='617584' date='Oct 5 2009, 04:03 PM']Isn't one of the main benefits of a rear port that the port doesn't take up any space on the front of the cabinet?...although this doesn't take into account how well designed the cabinet is.[/quote] Yes, much better to put a big port on the back than squeeze an undersized one onto the front. If you look at Acme cabs the 2x10" has dual rear ports because there's no space on the front. The 4x10" has three ports, two on the back, one on the front because there's some spare space on the baffle. The 1x10" has one port which is on the side because there's no space on the front and if it was on the back there would be enough box depth with the port colliding with the back of the driver. Two things really matter with a port - how it's tuned (which is decision based upon the driver, enclosure size and target performance) and if it has enough cross-sectional area to handle full power without output compression, chuffing (air noises) or phase shift. There is one other detail which I'll cover below... [quote name='jonny-lad' post='617584' date='Oct 5 2009, 04:03 PM']Having said that, I've heard plenty of rear ported cabinets that I like the sound of, like the Bag End 1x15 that is really compact and seems to just have a circular hole cut in the back right behind the speaker with no tubing.[/quote] Great cab, bizarre porting! If you place a port directly behind a driver you end up with midrange energy escaping through the port, which when reflected by a back wall will recombine with the direct output from the driver out of phase causing ragged response. The Bag End 15" exhibits a big change in sound depending on where it is placed vs walls. I'm actually looking to place the port in a hi-fi cab on the top... Alex Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted October 5, 2009 Share Posted October 5, 2009 People like to see the front of a cab crammed with speakers, with the volume requirements of modern speakers, thats not usually ideal unless you have a very deep cab, fairly sure there should be space on the front. Quote Link to comment Share on other sites More sharing options...
fenderiko Posted October 5, 2009 Author Share Posted October 5, 2009 (edited) [quote name='benwhiteuk' post='617508' date='Oct 5 2009, 03:03 PM']I was told it once by someone who I thought new what they were talking about. I guess it's not the case [/quote] glad we're not in 01.09.1939 .... Edited October 5, 2009 by fenderiko Quote Link to comment Share on other sites More sharing options...
JTUK Posted October 5, 2009 Share Posted October 5, 2009 Trial and error thing over the years. Best single cab by a mile was a Goliath ll 4x10 ported at the back. Good everywhere, IME. Outdoors, a 15" inch cab comes into its own and it keeps that bass somewhat better than 10' IMV..so a 15 with a 2x10 works well. Both ported at the front as it happens Tried this just the other week and my best outside sound without huge stage monitoring. I'll be keeping that rig now. Quote Link to comment Share on other sites More sharing options...
jonny-lad Posted October 6, 2009 Share Posted October 6, 2009 [quote name='alexclaber' post='617604' date='Oct 5 2009, 04:14 PM'][quote name='jonny-lad' post='617584' date='Oct 5 2009, 04:03 PM'] Having said that, I've heard plenty of rear ported cabinets that I like the sound of, like the Bag End 1x15 that is really compact and seems to just have a circular hole cut in the back right behind the speaker with no tubing.[/quote] Great cab, bizarre porting! If you place a port directly behind a driver you end up with midrange energy escaping through the port, which when reflected by a back wall will recombine with the direct output from the driver out of phase causing ragged response. The Bag End 15" exhibits a big change in sound depending on where it is placed vs walls. I'm actually looking to place the port in a hi-fi cab on the top... Alex [/quote] I knew there was a reason that putting a port directly behind the speaker wasn't the best idea...As the times I've heard the Bag End have been when I've been playing guitar in theatres, there has always been lots of space and curtains behind the cab - it'd be interesting to see how well it performs in smaller venues. Having said that, I've never heard the owner say a bad thing about it...and he always has great tone IMO! I'll look forward to seeing some of your new designs! Cheers! Quote Link to comment Share on other sites More sharing options...
Etienne Posted October 6, 2009 Share Posted October 6, 2009 [quote name='obbm' post='617458' date='Oct 5 2009, 02:27 PM']Just personal experience with the pair of Ashdown Mini 4x8s I had 6 years ago. Fine indoors, especially in front of a wall. Useless outdoors in the middle of a stage. That's why I sold them.[/quote] I also used to run a pair of ABM Mini 48's a few years ago, and my findings were exactly the same! Couldn't handle lows at reasonable stage volume at all well IMO... Quote Link to comment Share on other sites More sharing options...
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