Replace a Bose bass-module?

Discussion in 'Speakers & Subwoofers' started by Fred.D, Apr 1, 2005.

  1. Fred.D

    Fred.D Auditioning

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    I bought a Bose Acoustimass 15 speaker system 3 years ago and for the most time I've been quite happy with it (I know it's overpriced and doesn't have the best sound quality, but I used it mostly for movies and it fits quite well into my room).

    The problem is, that one month ago the bass-module broke and Bose wants about 230€ for the repair which I think is a lot (considered that I bought it for 1900€ and expected service), but the shop guy said it was cheap compared to what Bose generally charges for repair (both woofers of the bass-module are damaged but they would replace them for the price of one!!). Since there is a newer series which has more power than my old one I asked if I could buy a new bass-module, but I was told that Bose only sells the complete package and the cubes don't work with other subwoofer (the cubes are plugged into the bass-module and not into the receiver). The shop guy told me he was sorry that he couldn't offer any options and advised me to take the repair offer.

    I don't feel good paying 230€ for the repair (especially when I would face the same problem again, when it breaks the next time) but I think I would feel even worse loosing my complete system. I've been thinking about getting a better system because I've been using the speakers more for music than for movies lately (and I am aware of the limitations of the Bose speakers), so this is another point against repair.

    Now my main question: Is there really no way to use the cubes with any other subwoofer?
    I don't think there is a big market for cubes with broken base-module so selling seems not an option either.
    If I were to buy a new 5.1 speaker system (not Bose) how much would I have to spend to get one with equal/better quality than my original system?
     
  2. SethH

    SethH Cinematographer

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    I'd guess you'd end up paying around $1000 to get a 5.1 system you're happy with, but maybe a little less.

    You could probably run the bose speakers with a different sub. Here's the catch though, you'd have to set the crossover on your receiver up to about 200Hz (if it goes that high) to avoid damaging the speakers. You'd then run into a problem because most real subwoofers aren't made to play up to 200Hz.
     
  3. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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  4. Charlie Campisi

    Charlie Campisi Screenwriter

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    Bite the bullet now or later. This is a problem of all all-in-one type systems, not just Bose, but the expensive repair is a bummer. You can fix it, but then know you will have the same choice in a few years when another component needs to be fixed. Sooner or later, the price it costs you to repair it will exceed what you would've spent on a better system. As a short term fix, I'd suggest ebay. Someone out there has your bass module but blew the cubes or the control center (or whatever it's called). By a used one for hopefully less than what it would cost to repair yours (you could probably even sell your damaged one to offset some of the cost) and then when you want to replace it eventually, you won't feel like you are walking away from a ton of money. Good luck.
     
  5. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Hi Fred,

    I was in the exact same position you are currently in. My wife pushed in the contour button on my Adcom preamp at high volume and blew the "bass module" sky high. I purchased the AM5 system many, many years ago now before I knew much about audio. The wife still likes the AM5 setup because of the size and I have setup for serious listening downstairs in my home theater so I set out to rebuild the bass module. When I pulled it apart, I was shocked to see just how cheaply made the so called subwoofers are. They are literally the type of woofer you might expect to pay $2-3 dollars for. They are also only 5 or 5.25". The "crossover" is not even worth talking about. Anyway, I checked out a website called speakercity and they turned me on to their house brand woofer called Versatronics that is supposed modeled after a Scanspeak or Audax woofer (I can't remember which). They are a 6.5" so a little bit of clearancing is required. They are a 4 ohm woofer, I wired them in series to present an 8 ohm load to the amp. The improved in low end bass response is amazing, solid in room response down to about 30Hz (subwoofer corner loaded) and my total expenditure was about $65 including shipping.
     
  6. Fred.D

    Fred.D Auditioning

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    Thanks for the replies.

    How do I find out about the maximum crossover of my receiver(and set it)? I have a Harman/Kardon AVR 2000.

    Eric: That sounds really good, but I don't know much about electronics. What exactly would I need to do and would it be difficult?
     
  7. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    I looked for your receiver on Harmans' website. Apparently it is no longer a current version so best source of info would be your owners manual if you still have it.

    As for replacing the woofers, it's really pretty easy. You would have to redrill the mounting holes and "clearance" the enclosure a little as the magnet of the Versatronics woofer rubbed the enclosure slightly. As for series wiring: the positive on the amp goes to the positve on one speaker. Take the negative on the same speaker and run it to the positive of the second speaker. Then run the negative on the second speaker back to the amplifier negative and then you have series wiring for two 4 ohm woofers resulting in an 8 ohm load at the amplifier. I also took the liberty of redesigning the "crossover" while I was in there but this is not something you would have to do. I notice Speaker City no longer sells the woofers I used so I will give you a couple of ideas here:

    http://www.speakercity.com/Peerless_files/wr165.shtml

    You would have make sure this would fit. This is an 8 ohm driver so wiring should be in parallel for this woofer meaning positive wire to positive on both speakers and negative to negative resulting in a 4 ohm load. If your amp can handle this and you have the clearance, this should be a startling improvement over the Bose factory woofers.

    http://www.speakercity.com/Peerless_files/wr130.shtml

    This would most likely be a drop in replacement requiring no modification on your part. Sound quality will not be quite as good as the above 6.5" speaker (but still a nice improvement over the Bose)but this would be a simplier path. These are once again an 8 ohm driver.

    If you have any further questions, let me know.
     
  8. Fred.D

    Fred.D Auditioning

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    I found the manual for my receiver but it doesn't say anything about crossover.

    www . hci-services . com/tech_doc/documents/harman%20kardon/Home/Electronics/AVR/AVR%202000/Owner%27s%20Manual/AVR%202000%20English%20om.pdf
    (URL without the blanks, of course. The forum wouldn't allow me to post it the usual way.)

    The receiver delivers 40W per channel into 8 ohms. Is it correct to wire the 8 ohm drivers in parallel then?
    Also is there a difference with respect to drivers and wiring between the AM5 and AM15?
     
  9. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Interesting your owners manual does not address the crossover issue... HK receivers are typically rated on the conservative side. Your receiver will probably drive a 4 ohm load with no problems. You may find the AM15 to be a 4 ohm load anyway. Grab an ohmmeter and measure it and let me know what you find. Many BOSE products are 4 ohm. You could also very easily take apart your bass module and see what is inside. From what I can tell, they should be two 5.25" drivers.
     
  10. Fred.D

    Fred.D Auditioning

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    I'll have the shop return my bass-module and then check what's inside.

    Thanks again, Eric.
     
  11. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Sounds good. Let me know what you find.
     
  12. Fred.D

    Fred.D Auditioning

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    I finally got my bass-module back (it took a bit longer because two days after I told the shop to return it, they called me and said Bose had offered the repair for half of the original price...)

    So after I had opened the box (which was quite difficult to do without causing too much damage to it) I found two 4 Ohm woofers wired in series. They are 5,5" and there's definitely not enough space for anything bigger. The box is small anyway and since only the back can be opened, working inside is a bit difficult.

    I'll try to get some fitting woofers and put them in tomorrow.
     
  13. brentl

    brentl Cinematographer

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    Probably worth getting fixed properly if it's half the price!

    My thought anyways.

    Brent
     
  14. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    Hello again Fred,

    Give the 5.25" speaker I gave you a link to a shot then. What did you find as far as the quality of woofers currently in the bass module?
     
  15. Fred.D

    Fred.D Auditioning

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    Hi Eric
    I wanted to buy the woofers in a local shop. It would be easier and faster than ordering and having them send it to europe (though the dollar rate is good..)

    What do you mean about the quality of the woofers currently in the bass-module? Can you tell the quality by just looking at it? It looks like they are made of cardboard and a foam rubber ring on the outside.
    It's the first time I took a speaker apart so I don't know what they should look like.


    Hi Brent
    Half price is still 115€. I would certainly have accepted that if they had offered it in the first place. But now it's more about learning something than about the money.
     
  16. John Garcia

    John Garcia Executive Producer

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    The big problem you are going to run into by swapping any old driver in there, is that particular cabinet arrangement, crossover and amplifier are designed specifically to work with those drivers. You are going to get unpredictable results at best. Maybe you'll get lucky and it will work out though.
     
  17. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    John has some valid points. You cannot put just any driver in there. As far as I know, the bass module is passive not powered. It is a bass reflex design. The crossover is an inexpensive capacitor.

    By the quality of the woofers, I was referring to the fact that they weigh very little. The surround is such that the Xmax (excursion of the driver) looks to be very low.

    Fred, first measure the mounting depth of the woofer. Then see how much depth is actually available in the enclosure. You will probably have a bit of extra depth and be able to put something a bit larger in its place. Look for a woofer with a good crompromise of Fs and sensitivity (low Fs, high sensitivity) which is kind of an oxymoron but still doable. Find a woofer that is suitable for use in a bass reflex design. If you can do these things, (not as hard as it sounds)you should be very pleased with the results.
    [​IMG]
     
  18. John Garcia

    John Garcia Executive Producer

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    I thought the AM-15 was powered, but may be mistaken. Unfortunately, I'd expect it to be all but impossible to get any specs out of Bose so you could locate a 100% comparable replacement driver, but if this is now just an experiment, it can't hurt to try a few out and see what you get.
     
  19. Eric Hargrove

    Eric Hargrove Stunt Coordinator

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    John, I just rechecked and you are right, the AM15 bass module is powered. Should not affect things too much as long as Fred stays with an 8 ohm load it should be an easy load to drive. If I remember correctly, the passive unit was tested in a magazine years ago and had an efficiency of 84-85db with 1 watt input. Granted the powered version is a bit different animal. but, just about anthing nowdays is higher than that. I believe Fred has the potential to be very impresses with the results as long as he selects some quality drivers.
     
  20. Fred.D

    Fred.D Auditioning

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    I bought some woofers from a local shop. I can return them if they don't fit or sound good. Unfortunately, they had only one series of woofers that are suited and they are either 130mm or 165mm and the Bose woofer is 150mm in diameter. I took the 165mm but it seems like I'd have to cut a hole in the top and bottom to put them in. It seems impossible to put them in from the opening in the backside due to these pipes with flares that are in the bass-module.
    Eric, you said you put something like 165mm in - how did you do that?

    Here is the data sheet for the woofers I bought (it's the DS 060i):
    www . produktinfo.conrad.com/datenblaetter/350000-374999/369047-da-01-en-Alu-Cone_Subwoofer_DS-060.pdf
    (delete blanks in url. I can't post url right because I have fewer than 15 posts.)
    Res Freq is 38.0953Hz - is that good?

    The bass-module is definitely powered. The weight of the original woofers is 1100g. The new ones weight 1900g.
     

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