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Old 4th October 2008, 03:47 PM   #1
contax is offline contax  Spain
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Join Date: Mar 2008
Unhappy Rogers LS2 a/2 help

Hello,

I own a pair of Rogers LS2 a/2 speakers. Tweeters have been damaged. They were manufactured in 1992 by Seas. In the magnet label I can read "H 418 6 ohm Made in Norway". The H418 isn't a standard Seas Prestige tweeter tweeter. Two similar Prestige series models are H0414 and H0532. They have the same chassis, aluminium diaphragm and size. The fit perfectly in the speaker cabinet.

The only problem is their impedance is now 8 ohm instead 6 ohm. Seas does not have a 6 ohm tweeter with the required diameter. I imagine H0418 specifications and response should be very close to the news H0414 or H0532.

In this brochure (http://www.mhennessy3.f9.co.uk/showp...rs/1991_p7.jpg) I can see the crossing over is at 3.5KHz.

The tweeter crossover circuit it's only a 1.5 ohm resistor and a 4.7uF capacitor in series with the drive.

My idea is to replace the tweeter by the H0532 (H0414 with double magnet) and to remove the 1.5 ohm resistor.

I know the speaker behaviour are going to be different, but very close to the original. Do you suggest to change the capacitor value also?.

What do you think about it?.

Thanks in advance for your help.

Best regards:-)
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Old 5th October 2008, 08:57 AM   #2
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Join Date: May 2004
Location: Sydney
It could be done but the effort involved in making it to work as well as it used to would be equivalent to designing and making a new pair of speakers. Given that second hand Rogers are very cheap these days, I would suggest to buy another pair of second hand Rogers.

I had a pair of LS2 and gave them away. I had two pairs of Rogers LS6/2a, which are better speakers, and I doubted if I could sell them for $350 a pair. The Rogers Studio 1A was very good, and I understood people could get a pair for $700. So I also gave them away to my cusion.

The Rogers were the best value for money speakers in the old days and they sound fairly good.

Regards,
Bill
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Old 5th October 2008, 10:19 AM   #3
qwad is offline qwad  Australia
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go ahead contax, give it a try, you have'nt a lot to lose, by trying it the way you think as the 1.5 ohm resistor is only there to output match the tweeter to the bass mid unit sounds as if its only a 1st order x/ over in the high pass: since a 6 ohm tweeter is a bit more efficient than an 8 ohm one, you may not even notice any difference at all cheers TC
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Old 6th October 2008, 01:59 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

If the crossover is a simple as you say then the crossover itself
depends on the rolloff of the tweeter as well as electrical roll-off.
6DB electrical + 12dB acoutic = 18dB/ octave acoustic.

The response of the tweeters need to match around 3.5kHz.

If so your plan will be fine, but you might need to add some
level setting resistors, likely the new tweeters are louder.

/sreten.
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Old 6th October 2008, 04:04 PM   #5
contax is offline contax  Spain
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This is what Seas answered to me. The H0414 or H0532 is a good replacement for Rogers LS2/s2, LS4 a/2 and LS8a.

H0414 and H0532 are identical to the original H0418, but 8 ohm.

-----------------------------------------------------------------------------
Dear-

Many thanks for email. You are quite right. These two are practically the
same tweeter, the only difference is that H0414 has a lense mounted to the
grille.

Best regards
SEAS Fabrikker AS

-----Opprinnelig melding-----
Sendt: 3. oktober 2008 11:02
Til: mail@seas.no
Emne: SEAS: Rogers LS2 A/2

This is an enquiry e-mail via http://www.seas.no

Hello,

I told you this in a previous message, but now I have more details about the
driver I am looking for.

The Rogers LS2 A/2 tweeter was manufactured by you in 1992. The part number
is H 418. It's very similar to the Prestige H 414. I would be very grateful
if you could tell me if the H 418 and H414 are equivalent. The magnet's
label tells also 6 ohm only. I don't know if it's the coil DC resistance or
the impedance.

Rogers cannot supply this replacement part because it's too old.

Looking forward to hearing from you.

Best regards:-)
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Old 6th October 2008, 04:04 PM   #6
contax is offline contax  Spain
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Join Date: Mar 2008
Thanks very much for all your answers.

sreten I would be very grateful if you could explain why the new tweeters are louder. Today Seas has confirmed me than the tweeters are identical, also the sensitivity.

My intention was to supress the 1.5 ohms resistor in series with the old tweeter. The impedance and the DC resistance is the new tweeters greater (8 ohms / 6.2 ohms) than i the old ones.
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Old 6th October 2008, 04:41 PM   #7
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by contax
Thanks very much for all your answers.

sreten I would be very grateful if you could explain why the new tweeters are louder.
Today Seas has confirmed me than the tweeters are identical, also the sensitivity.

My intention was to supress the 1.5 ohms resistor in series with the old tweeter.
The impedance and the DC resistance is the new tweeters greater (8 ohms /
6.2 ohms) than the old ones.
Hi,

IMO one should always set subtle final tweeter level changes
by ear. If they are the same senstivity leaving the 1.5R in
circuit is going to be nearer than leaving it out. Only if the
lower impedance driver is slightly higher sensitivity can you
omit it and get the same tweeter level.

Often manafacturer specific tweeters are made with lowish
senstivities (read smaller magnets) than generally available
types, seems not to be the case here.

Tweaking tweeter levels for the position and room furnishings
is surprisingly effective once you've dialed in the "correct" level.

/sreten.
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