jtfoto Posted December 19, 2018 Posted December 19, 2018 I have just finished re-building the crossovers on a pair of TLX8 JBL's. I have just read that JBL speakers are wired out of phase compared to most other speakers. Can anyone confirm if this is the case? Cheers. A very merry xmas to all members and their families. :-)
Guest Posted December 19, 2018 Posted December 19, 2018 I recall (back when I worked in a studio) it was more of their P.A equipment, wasn't it? Not so much domestic gear. I could be wrong though.
andyr Posted December 19, 2018 Posted December 19, 2018 1 hour ago, jtfoto said: I have just finished re-building the crossovers on a pair of TLX8 JBL's. I have just read that JBL speakers are wired out of phase compared to most other speakers. Can anyone confirm if this is the case? Cheers. A very merry xmas to all members and their families. I'm wondering what you mean by "JBL speakers are wired out of phase compared to most other speakers"? In terms of "phase" there are 3 different things you need to be aware of. In order of "getting more esoteric": 1. relative phase - ie. L to R channel. you want the speakers connected the same way, left channel and right channel. If you don't do this, you won't experience a solid central image - and bass will be deficient. I'm sure JBL speakers leave the factory with the black and red terminals connected to the drivers in the same way, L & R! 2. a driver within each speaker is connected out of phase. this can happen depending on the XO slopes used. 6dB Butterworth and 24dB Linkwitz-Riley XOs require the 2 drivers to be connected with the same phase. however, mixed-slope XOs and 12dB L-R require 1 of the 2 drivers to be connected out of phase. This is all perfectly "correct", sonic wise. again, I would be surprised if JBL speakers left the factory with - as a matter of course - one driver connected in the wrong phase. 3. is the speaker connected with correct "absolute phase"? this is associated with the concept of (assuming #1 is correct) swapping around the '+ve' and '-ve' speaker wires on both speakers. in simplistic terms - if the recorded signal has a positive wave front ... then the speakers should be reproducing this (ie. the drivers move forwards). if the speaker is connected with "reverse absolute phase" then the drivers will move backwards, with a positive wave front. This profoundly affects the sound of, for instance, a trombone ... and it doesn't sound as good when the correct absolute polarity has not been maintained. trouble is with this concept is ... a. recording engineers don't always make sure that their mics are connected "the right way round" and b. amplifiers which have odd nos. of gain stages ... reverse phase. So it is very hard to make sure your signal chain maintains correct "absolute phase"! so it is entirely possible that JBL decided to build their speakers with reversed "absolute phase" to compensate for errors elsewhere in the music chain. Andy
tubularbells Posted December 19, 2018 Posted December 19, 2018 JBL professional model drivers suck inward if you apply a small DC voltage to the terminals. Someone once said to me it was a safety measure in the event of a catastrophic amp failure so that the cone wouldn't be blown off the basket and end up in the recording engineer's lap! True or not you decide
Full Range Posted December 19, 2018 Posted December 19, 2018 13 hours ago, jtfoto said: I have just finished re-building the crossovers on a pair of TLX8 JBL's. I have just read that JBL speakers are wired out of phase compared to most other speakers. Can anyone confirm if this is the case? Cheers. A very merry xmas to all members and their families. Yes this is correct But it depends on the model number of the driver So you need to check the model number information Also JBL has a list available somewhere on the WWWeb My JBL compression tweeters are black = positive & Red = Negative
44maloo Posted December 19, 2018 Posted December 19, 2018 Yes that’s correct some JBL drivers are black terminal is positive. Use a 9v battery to determine the polarity. + on battery if cone moves forward this is positive on the driver, my e 145 and 2405 are this way. Also is the system is wired wrong should hear it .
ray4410 Posted December 20, 2018 Posted December 20, 2018 How to Understand JBL Reverse Polarity - Speaker Exchange https://reconingspeakers.com/faq/how-to-understand-jbl-reverse-polarity/ Cached The use of these jacks required that JBL change their polarity to fit into what had become industry standards. Therefore, many of the older JBL speakers have How to Understand JBL Reverse Polarity In the golden olden days of speakers, the issue of whether the first motion of a cone was inward or outward, or polarity, was not uniform. Eventually it became standardized. Most speakers have an initial outward movement. When JBL started making speakers, they arbitrarily adopted reverse polarity and their speakers had an initial inward movement. This continued until JBL developed their musical instrument series speakers which used ¼” jacks. The use of these jacks required that JBL change their polarity to fit into what had become industry standards. Therefore, many of the older JBL speakers have reverse polarity, while newer models match what has become the industry standard. Does this really matter" You can equate this to taking a 1 mile walk. It really won’t matter if you start with your left foot or right foot. Remember, we stock or can order JBL Recone Kits and JBL Diaphragms and a variety of other speaker parts. JBL has published a technical bulletin regarding this. In it they define the terminology and list each specific speaker and its polarity. Terminology: Positive systems: A system or transducer is said to be positive if a positive-going voltage applied to its red (or non-black) input terminal causes a positive pressure at the acoustical output of the device. For cone transducers, the cone will move outward and can be easily seen. For compression drivers, a positivegoing pressure can be measured at the driver’s exit. Many systems and transducers do not have color-coded input terminals, and in these cases one terminal is usually labeled with a + sign. Consistent with the positive standard, a positive- going signal at the positive terminal will result in outward motion of the cone. Negative systems: A system or transducer is said to be negative if a positive-going voltage applied to its red (non-black) terminal causes a negative pressure at the output of the device. Polarity of JBL Professional systems and transducers: The following is a comprehensive listing of former and current JBL Professional systems and transducers by product category. Within each category models are indicated as positive or negative. The obsolete models included here are those that are still supported by company repair service and spare parts. Musical instrument transducers: The following models are negative: E110-8 E120-8, 16, E130-8 E140-8, E155-4, 8. The following models are positive: M121-8, M151-8 Control Monitors: all models are positive: Control 1, Control 1 Plus, Control Micro Control 1AW/70, Control SB Micro Control 5, Control 10L, R, Control SB-1, Control SB-5, Control 12SR Control Contractor Series Studio Monitors: All 4300-Series models (except models 4311 and 4312L, R) are negative. The following models are negative: 4406, 4408L, R, 4410L, R 4412L, R, 4425L, R 4430L, R, 435L, R. The following models are positive: 4206, 4208, 4311, 4312L, R, 4408A-L, R 4410A-L, R, 4412A-L, R 6208, DMS-1 LSR4300-Series, LSR-Series LSR6300-Series Compression Drivers: the following models are negative: 2402H, 2404H, 2405H, 2426H, J, 2427H, J 2446H, J, 2447H, J 2450H, J, 2451H, J Cone Transducers: the following models are negative: LE8T-H 2105H, 2118H, J 2123H, J, 2202H 2206H, 2220H, J 2226H, J, 2235H 2240G, H, 2241G, H 2245H. The following models are positive: 2012H 2020H, 2242H Coaxial transducers: the following models are positive: 2142H, 2152H, 2155H Cinema systems: 3000-Series systems; the following models are positive: 3622N, 3677, 3678, 3632, 3632T 3678-LF, 3639, 4000-Series systems; the following models are positive: 4622, 4622N, 4632, 4632T. 4000-Series systems; the following models are negative: 4670D, 4675C, 4675C-4LF 4765C-8LF 5000-Series systems; the following models are negative: 5671, 5672, 5672Bi, 5674. Cinema subwoofers; the following models are negative: 4642, 4645 Cinema subwoofers; the following models are positive: 3635, 4641, 4642A, 4642A-GS, 4645B, 4645C Cinema surround systems: the following models are negative: 8330, 8333, 8340. Cinema surround systems: the following models are positive: 3310, 8325, 8330A*, 8340A* (*Note change from previous model numbers) Enclosed utility systems: The following models are positive: SLT-1 4612OK, 8216A 8216AT. The following models are negative: 4660A, 4671OK, 4652. Application Engineered Series (Prefixes AM, AC, AL, ASB, SH): all models are positive. Architectural Series (Prefix AS): all models are positive Array Series (Models 4890A, 4892, 4893, 4894): all models are positive Cabaret Series (Models 4602, 4612, 4622, 4623, 4625, 4627, 4680, 4690, 4695): all models are positive. Concert Series (Models 4825, 4828, 4842, 4845, 4847, 4850, 4851, 4852, 4853, 4860, 4861, 4862, 4863, 3866, 4870, 4871, 4872, 4873): all models are positive Control contractor Series: all models are positive EON Systems (Prefix EON): all models are positive HLA Series (Prefix HLA): all models are positive JRX Series (Prefix JRX): all models are positive MPro Series (Prefix MP): all models are positive Marquis Series (Prefix MS): all models are positive MR Series (Prefix MR): all models are positive Precision Directivity Series (Prefix PD): all models are positive Soundfactor Series (Prefix SF): all models are positive Sound Power Series (Prefix SP): all models are positive SR Series (Prefix SR): all models are positive SR Series X (Prefix SR): all models are positive SR Series II (Prefix SR): all models are positive SRX Series (Prefix SRX): all models are positive TR Series (Prefix TR): all models are positive Venue Series (Prefix VS): all models are positive Vertec Series (Prefix VT): all models are positive VRX Series (Prefix VRX): all models are positive Leave a Reply Cancel reply You must be logged in to post a comment. 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davewantsmoore Posted December 20, 2018 Posted December 20, 2018 3 hours ago, Full Range said: But it depends on the model number of the driver This ^^^ No generalisation is possible.
Grant Slack Posted December 20, 2018 Posted December 20, 2018 (edited) 4 hours ago, Full Range said: Yes this is correct But it depends on the model number of the driver So you need to check the model number information Also JBL has a list available somewhere on the WWWeb My JBL compression tweeters are black = positive & Red = Negative Hello everyone. I support Mr Full Range here. It depends entirely on the specific driver model. It was limited to all pre-1990 models and some later models in their pro driver range. It relates to an old JBL system of labeling. JBL did not decide to be contrary: they were in the game right at the start of loudspeaker manufacture, before there were any conventions, and they chose a convention that turned out later to be in the minority. In 1990 they decided to change over to the majority convention. It does not apply to any current driver models. IIRC, the terminology used by JBL was not like "red = negative", but more along the lines of "for forward driver motion under a positive-going signal, connect earth to red". It is easy to determine on their cone drivers by applying a 1.5V cell battery, but much more difficult to do on their compression drivers. JBL have a very handy application note that lists all models affected. Link. However, be warned, if you buy a used driver, it might have been refurbished and its convention changed. Regards Grant (I see some related information was posted while I was typing this. Apologies for some duplication.) Edited December 20, 2018 by Grant Slack 1
bob_m_54 Posted December 20, 2018 Posted December 20, 2018 This is something I have wondered about a pair of Aaron Octet speakers I bought second hand. I was going to replace the crossover caps, and drew out the crossover schematics in preparation. But this is the result. As the speakers are second hand (off Gumtree), I have no idea if the drivers may have been disconnected and reconnected, or that I may have been a bit dyslexic when I traced out the diagram. 1
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