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Thread: JBL 4355 clone with different woofers

  1. #91
    Senior Member Odd's Avatar
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    Nice work.
    43XX (2235-2123-2450-2405-CC 3155)5235-4412-4406-4401-L250-18Ti-L40-S109 Aquarius lV-C38 (030) 305P MkII

  2. #92
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    hello, the work, albeit slowly continues. I fixed the supports for the 2445 and the reflex tubes. Before screwing the cones, I have to insert the sound-absorbing material; they recommend the 3 cm high ashlar polyurethane foam, what do you think?
    Giuseppe

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  4. #94
    Senior Member RMC's Avatar
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    Giuseppe,

    RE "sound-absorbing material; they recommend the 3 cm high ashlar polyurethane foam, what do you think?"

    I looked at a few web sites to see what your foam is, saw an italian and a german site too. Assuming i got the right foam, it seemed somewhat compressed materials, more like closed cell than open cell for example. Didn't appear like a very proper material, again if i got the right ones.

    Damping material has to be soft, fluffy, easily "spongy" = absorptive. I tried a foam in the past (see 1" foam pic) and when tacked in place it didn't meet these adjectives anymore due to some compression from tacking. Glueing it wasn't better having to cover and hold on braces for e.g. So the result wasn't good and i removed all of that.

    You're possibly better using 3 cm thick fiberglass wool, its easier to install inside. Then to prevent fibers from flying in the box or vent tubes, you simply spray a VERY LIGHT coat of spray paint on the fiberglass, this will contain the fibers. Some prefer using hair spray fixative, but in my view spray paint might last forever, maybe not hair spray? You can also cover the fiberglass with some cheese cloth for similar result.

    Another option is to use Polyester damping instead of fiberglass, since it has no flying fibers. I'm switching my LF cabs from fiberglass to Polyester, and exit the airborne fibers issue. Some don't like it as much, true it has little less density, but the one i purchase from Solen and others is 1.5" thick, i guess that compensates for fiberglass density but only 1" thick.

    At low frequencies it matters less with regards to preventing midrange sound reflections in the cab. In a bass only cabinet, or in an enclosure compartment where the woofer is crossed over pretty low (e.g. 290 hz), there aren't really mid frequencies involved, therefore no such reflections in that section. Moreover, here the low-mid driver's back wave is isolated in a sub-chamber and the mid freq driver is actually a horn (not a cone with a radiating back wave).

    Therefore, i think one has to examine the precise situation before condemning either fiberglass or polyester. In any case, i've attached a pic of JBL's own suggestions with regards to damping material in a speaker cabinet. Note that polyester isn't mentioned, probably because at the time of this older document it wasn't used as today...

    Richard

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  5. #95
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by RMC View Post
    Another option is to use Polyester damping instead of fiberglass, since it has no flying fibers. I'm switching my LF cabs from fiberglass to Polyester, and exit the airborne fibers issue. Some don't like it as much, true it has little less density, but the one i purchase from Solen and others is 1.5" thick, i guess that compensates for fiberglass density but only 1" thick.
    Years ago I also looked for alternatives to fiberglass. I compared egg-crate foam, polyester batting, and 1 inch “non-shedding” fiberglass. It was years before I had access to any precision measurement equipment so all of my experiments were performed by subjective evaluation.

    That said, I did notice audible differences between the different materials. I tried all three materials both as wall lining as well as completely internally stuffed cabinets. I preferred the fiberglass in every comparison. The egg crate foam was a very close second and the polyester batting was obviously inferior at reducing mid frequencies being reflected back through the woofer cone. Using more of it helped, but only up to a point.

    I have used fiberglass ever since.


    Widget

  6. #96
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    Hi Widget,

    Thanks for the insight.

    Fiberglass i have bundles from replacing the house insulation in the attic (10" thick there, yup cold Canada).

    I also like the soft open cell egg-crate foam, when i can find some locally at reasonable price, mostly used in my small satellite boxes. I don't go for the more rigid type or closed cell. (Btw Solen, egg-crate acoustic foam, 1.5" X 40" X 80" (say 2 sq. y.), $73. + ship + tx = $100. i use a fair amount so $$$). My foam stock is almost depleted. Shipping companies (Amazon, etc.) use a lot so i don't see much around. But I'm not yet at the point of doing the garbage cans around town to find some, lol.

    RE "polyester batting was obviously inferior at reducing mid frequencies being reflected back through the woofer cone."

    There are no mid frequencies reflected in my bass only cabs, 24 db xo 250 hz or so, on to two-way satellites, bi-amp systems. LF box doesn't see the MF nor HF, and the satellite doesn't see the LF. MF reflections might occur in the satellite, however its absorbed by the soft egg-crate foam inside. The OP's situation is similar in my view, as previously explained. (I don't deny the merits of Fiberglass, its one of my suggestions to the OP).

    I remember reading that R.H. Small, in his monumental work, mentioned a minimal amount of damping material should be used. On the other hand, Eargle says low mass material, and Dickason says low density. Well its pretty much the same since they're related by Mass = Density X Volume. In that context polyester isn't bad. Regards,

    Richard

  7. #97
    Senior Member Sootshe's Avatar
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    Thumbs up

    Quote Originally Posted by Mr. Widget View Post
    Years ago I also looked for alternatives to fiberglass. I compared egg-crate foam, polyester batting, and 1 inch “non-shedding” fiberglass. It was years before I had access to any precision measurement equipment so all of my experiments were performed by subjective evaluation.

    That said, I did notice audible differences between the different materials. I tried all three materials both as wall lining as well as completely internally stuffed cabinets. I preferred the fiberglass in every comparison. The egg crate foam was a very close second and the polyester batting was obviously inferior at reducing mid frequencies being reflected back through the woofer cone. Using more of it helped, but only up to a point.

    I have used fiberglass ever since.


    Widget
    My experience as well.

    I changed my fibreglass lining to polyester & it changed the sound of the bass quite dramatically....not for the good.
    I ended up putting the fibreglass back in & covered it with black grill cloth stapled over the top of it to prevent the “flying fibres”.

  8. #98
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    Hi friends. The prototype is finished, I mounted the four components but I’m in delay for the test and the crossover verify. I was very busy during these days, I think after Christmas, next week, I will go to my friend for the final job. I want to biamp the speaker, woofers + three other ways and I’m looking for a good second hand balanced active crossover. I did a research on line but I’m not expert 100% and these are my options:
    Bryston 10B STL (my first choice)
    UREI 525
    Pioneer D-23 (too much old and not balanced)
    Inkel DIV-23
    Fostex EN3020
    Rane AC 23S
    The problem is that living in Italy It is very difficult for me to find a Bryston; I know the Bryston 10B STL because a friend in Italy drives his JBL 4333 whit this crossover. What do you think about the list of crossover?
    Giuseppe

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    Add to your list the BSS FDS360. The best and most flexible analog electronic crossover ever commercially produced.

  10. #100
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    If you find a Bryston it may be pretty expensive.

    I use the Rane AC 22, good quality gear from the 1990s. Beware of more recent Rane stuff. What they made in the 80s and 90s was nicely made. However around 2000-2003 Rane was purchased by the In Music Group and they moved production from the US to low cost manufacturing China. Therefore recent Rane is not at all what it used to be...

    Each Rane unit i have (3), balanced on 1/4" TRS, has a small manufacturing date sticker (month and year) at the back and this should be your guide to separate the good ones from the so so China stuff.

    You might also want to consider the Ashly XR-1001 i have too, 3-way mono though, and its distributed in Italy by Etabeta Electronics spa according to the Ashly web site. As for the others on your list, Pioneer and Inkel might be cheap gear, the Urei and Fostex i'm not familiar with.

    Good luck in your search.

  11. #101
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    It depends on your aspirations.

    With shipping costs, used or dated equipment and the need for some flexibility with your project a kit may be a better option

    https://www.xkitz.com/collections/ac...i-amplifiers-1

    The company above has some quite professional pre assembled building block boards with balanced and unbalanced inputs and outputs. They use the latest TI audio chips, circuits and the crossover points can be adjusted. The performance will most likely exceed the above mentioned pro crossovers with more modern parts and engineering.

    There are superfluous circuits in these pro units that you just don’t need unless your a PA Roadie. They have all gone Dsp in the pro audio world. So the focus on high quality analogue crossovers has not been pursued with in volume manufacturing.

    Small boutique companies like the above are worth looking at. Marchland custom crossovers are working considering. Although a recent review of technical performance was not impressive. Pass labs and First Watt stopped making active crossover because it was too labour intensive and they hardly sold enough for volume manufacturing.

    The application of balanced audio inputs and outputs has crept in hifi and hi end in recent times. For the most part it’s a marketing ploy to dress up the product so you believe it’s better quality in the consumer audio scene. It’s not. What the consumer is lead to believe just isn’t true. But that’s hifi beware marketing.

    In practice balanced audio connectors are used in PA equipment for long cable runs where noise and interference can be a problem. But it’s not going to be quieter than an unbalanced connection over short cable runs of less than 10 metre unless the input and output impedances have been carefully matched to less than 1% so the CMRR actually works. CMRR refers to the balanced input rejection of noise or common mode noise to signal ratio.

    To get around this low cost manufacturing use high impedance circuits to reduce CMRR problems. But this add circuit noise and there is nothing to be gained at the end of the day for the consumer. A good balanced input should have a S\N ratio of less than -110db and preferably -115db and have CMRR is at least -70db across the audio frequency range. That is expensive. For that reason true balanced studio equipment is quite expensive with elaborate circuits or custom built Jensen input and out transformers.

    In domestic hifi or home audio stay with unbalanced cables. It’s going to save you money and it’s going to give you a better result. If your power amp has only balanced input simply short the negative signal input pin (3) to the ground pin(1).

    I imagine your friend would be able to set this kit up for you and you will get a very good outcome with a small investment in cost and effort.

    I have purchased some of these items but not had an opportunity to test them yet.

    https://www.xkitz.com/collections/ac...i-amplifiers-1

  12. #102
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    Quote Originally Posted by Ian Mackenzie View Post
    It depends on your aspirations.

    With shipping costs, used or dated equipment and the need for some flexibility with your project a kit may be a better option

    https://www.xkitz.com/collections/ac...i-amplifiers-1

    The company above has some quite professional pre assembled building block boards with balanced and unbalanced inputs and outputs. They use the latest TI audio chips, circuits and the crossover points can be adjusted. The performance will most likely exceed the above mentioned pro crossovers with more modern parts and engineering.

    There are superfluous circuits in these pro units that you just don’t need unless your a PA Roadie. They have all gone Dsp in the pro audio world. So the focus on high quality analogue crossovers has not been pursued with in volume manufacturing.

    Small boutique companies like the above are worth looking at. Marchland custom crossovers are working considering. Although a recent review of technical performance was not impressive. Pass labs and First Watt stopped making active crossover because it was too labour intensive and they hardly sold enough for volume manufacturing.

    The application of balanced audio inputs and outputs has crept in hifi and hi end in recent times. For the most part it’s a marketing ploy to dress up the product so you believe it’s better quality in the consumer audio scene. It’s not. What the consumer is lead to believe just isn’t true. But that’s hifi beware marketing.

    In practice balanced audio connectors are used in PA equipment for long cable runs where noise and interference can be a problem. But it’s not going to be quieter than an unbalanced connection over short cable runs of less than 10 metre unless the input and output impedances have been carefully matched to less than 1% so the CMRR actually works. CMRR refers to the balanced input rejection of noise or common mode noise to signal ratio.

    To get around this low cost manufacturing use high impedance circuits to reduce CMRR problems. But this add circuit noise and there is nothing to be gained at the end of the day for the consumer. A good balanced input should have a S\N ratio of less than -110db and preferably -115db and have CMRR is at least -70db across the audio frequency range. That is expensive. For that reason true balanced studio equipment is quite expensive with elaborate circuits or custom built Jensen input and out transformers.

    In domestic hifi or home audio stay with unbalanced cables. It’s going to save you money and it’s going to give you a better result. If your power amp has only balanced input simply short the negative signal input pin (3) to the ground pin(1).

    I imagine your friend would be able to set this kit up for you and you will get a very good outcome with a small investment in cost and effort.

    I have purchased some of these items but not had an opportunity to test them yet.

    https://www.xkitz.com/collections/ac...i-amplifiers-1

    Thanks for your reply. I own only Mark Levinson components, N° 380s + N° 331 (with N° 37 + N° 360s), I hope that these units are really balanced because if it were the opposite it would greatly discredit the image of this company. Now you give me a lot of doubts, I hope I don't have fake balanced ones in the house.
    I have probably found a Bryston 10B, I need to know how much shipping will cost. On Lansing Heritage I read that you speak very well about it.
    Giuseppe

  13. #103
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    If you have real Mark Levinson components the 10B is a reasonable option.

    But it’s dated and won’t give you pre determined crossover requirements without a lot of phone calls to the factory.


    The 4355 needs 18 dB crossover slopes @290 hertz But in current day you should try LR12 dB and KR24 dB filters.

    The rest are a step backward.

    DEQX an Australian Business that have made improvements recently.

    https://www.deqx.com/

    It would be worth looking at them.

    The active crossover is arguably the most important component in your signal path.

  14. #104
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    Quote Originally Posted by Ian Mackenzie View Post
    The application of balanced audio inputs and outputs has crept in hifi and hi end in recent times. For the most part it’s a marketing ploy to dress up the product so you believe it’s better quality in the consumer audio scene. It’s not. What the consumer is lead to believe just isn’t true. But that’s hifi beware marketing.
    While I agree with your premise, true balanced audio circuits and design can offer significant performance advantages in some situations. Having been in urban areas with lots of RFI and noisy electrical service, I have been able to greatly improve the noise floor in my system by going fully balanced. I too have a Mark Levinson front end, preamp and sources, that connect to a remote amp rack with balanced active crossovers and amplifiers. There are quite audible benefits to going fully balanced in MY system.

    That said, there is a lot of marketing hype out there and for most folks I agree with you that there is no benefit to going to the added expense of using balanced circuits.


    Widget

  15. #105
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    That’s right.

    If you are in an area prone to RFI break through then you have that option.

    Mark Levinson employee world class engineers and they don’t build to a price. So your getting a premium piece of audio equipment.

    Technically, equipment can be modified by a technician with ceramic capacitors or ferrite beds right on the inputs to attenuate the RFI. This kind of interference can in fact overload audio circuits due to limits on gain bandwidth which reduces with increased frequency. Alternatively a bandwidth definition filter is used to attenuate subsonic and frequencies above the audio spectrum.

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