adjustable OHM ?

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Antispammer - 25 Aug 2006 03:50 GMT

I was looking for a pair of 8 ohm tweeters and stumble onto this.

Just not sure if there is such a thing such 4-8ohm(adjustable?).

need everyone's comments.

http://cgi.ebay.com/5-TITANIUM-HORN-SUPER-TWEETER-800-Watt-FREE-KIT-6650_W0QQite
mZ270016142878QQihZ017QQcategoryZ14943QQtcZphotoQQrdZ1QQcmdZViewItem

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KU40 - 25 Aug 2006 04:15 GMT

speakers can be made with more than one voice coil, each having their
own impedence. the user can then choose to use one or both, each
configuration giving a different set of properties for the speaker.

this one I don't know, it says "2.8" High temp kapton voice coil" which
would lead me to believe there is only one voice coil, which cannot be
interchangeable between 4 and 8 ohms itself.

what i think is funny is that right on the back plate is stamped "800
watts output power," as if the speaker itself sends power somewhere
instead of receiving it. I'd stay far away from it.

Signature

KU40

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MOSFET - 25 Aug 2006 05:01 GMT

> this one I don't know, it says "2.8" High temp kapton voice coil" which
> would lead me to believe there is only one voice coil, which cannot be
> interchangeable between 4 and 8 ohms itself.

I agree. Clearly there is one 2.8" voice coil. What I think they are
referring to is what type of amp it will work with, wich is silly because
the amp does not determine resistance in ohms (obviously), the speaker (or
load) does. But as often the case on Ebay, the seller is being fast and
loose with terminology in an effort to sell the product. He is trying to
imply that this tweeter will work for both home applications (where speakers
are typically rated at 8 ohms) and car applications (where speakers are
typically 4 ohms). What the REAL resistance in ohms of these tweeters are I
can't say. But it is DEFINATELY NOT BOTH 4 AND 8! It is one or the other.
I would ask the seller.

MOSFET

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Matt Ion - 25 Aug 2006 09:00 GMT

>>this one I don't know, it says "2.8" High temp kapton voice coil" which
>>would lead me to believe there is only one voice coil, which cannot be
[quoted text clipped - 10 lines]
> can't say. But it is DEFINATELY NOT BOTH 4 AND 8! It is one or the other.
> I would ask the seller.

I would tend to suspect the same, that the impedance listing simply means it
will "work" with amps designated for 4-8 ohm outputs.

Actually, the ebay listing's specs very closely (but don't exactly) mirror
others I found on the 'net. Example:
From
http://www.westcoastmall.net/shop/product_info.php?cPath=23_52&products_id=2762

* 4" Heavy Duty Titanium Super Tweeter (odd, the ebay add says 5")
* Die Cast Aluminum Frame
* Diamond Chrome Cutting Finish
* 2.8" High Temperature Kapton Voice Coil
* 130 Oz Magnet Structure
* 400 Watts RMS / 800 Watts Peak Power
* 4-8 Ohms Impedance
* Ferra Fluid Enhanced Voice Coil (FERRA? Correctly, it's "ferrofluid".)
* Sensitivity: 105dB
* Frequency Response 2K-25KHz
* Mylar Crossover Pack in Gift Box
* Single Pack

The specs appear to be pretty much cut'n'pasted from Audiopipe's website - they
don't list the 6650 specifically, but they do list three other "titanium"
tweeters with nearly identical specs (including "4-8 OHMS Impedence").
http://www.audiopipe.co.uk/Productlist.aspx?ChildID=47&SubCatagory=Titanium%20Tw
eeters

Interestingly, their subs don't like frequency "ranges", and their "other
tweeters" all list "Impedance: 4 Ohms (Can be used with 8 & 16 Ohms systems)".

I think I'll drop them an email...

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mfreak - 25 Aug 2006 14:16 GMT

> What the REAL resistance in ohms of these tweeters are I
> can't say. But it is DEFINATELY NOT BOTH 4 AND 8! It is one or the other.
> I would ask the seller.

Except it's not 'resistance', it's 'impedance'. I'm sure you know
this, impedance changes at different freq's, so technically, the seller
could be claiming that the impedance ranges between 4 and 8 across the
freq spectrum. I doubt it tho, that'd be a weird way to word it.. I'd
just call em 4ohm tweeters.

>From what I've seen, impedance is lowest at the low end if it's normal

freq response, like around 3kHz. It rises to 3-5 times that at 20kHz,
and the plot looks parabolic. Testing a tweeter for resistance, ie
sticking an ohmmeter across your speaker's terminals would probably
give you something close to the lowest impedance across the entire freq
spectrum.

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Antispammer - 29 Aug 2006 05:43 GMT

thanks everyone...

i better skip this.hehehe

>> What the REAL resistance in ohms of these tweeters are I
>> can't say. But it is DEFINATELY NOT BOTH 4 AND 8! It is one or the
[quoted text clipped - 13 lines]
> give you something close to the lowest impedance across the entire freq
> spectrum.

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