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Old 21st January 2008, 07:32 AM   #1
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Default RS 1197 center speaker ideas

Hey guys, I've been wanting to update my center and thought about using one of my virgin RS 1197 that I have laying around. I'd like to support the bottom end with multiple 5.25" or 6.5" drivers with a 1st order x-over around 300-400Hz. Would they benefit from tweeter help at the very top? I've been away from speakerbuilding for a few years, so I need some ideas.

My left and right are a SEAS 6.5"/Dayton 1 1/8" 2-way TQWT with dual 15" infinite baffle subs in the wall.
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Old 21st January 2008, 03:24 PM   #2
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I would not add any more tweet to the 1197 personally. But I would add help at the bottom.

Your center will not be timbre matched with the L and R but it will make sound. I would consider using a Seas+Dayton bookshelf monitor as your center too.

Save the 1197 for a dedicated two channel setup. Just my opinion.
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Old 21st January 2008, 07:18 PM   #3
TerryO is offline TerryO  United States
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I agree with the 'Zilla Guy.

Another factor to consider, if your Center Speaker is be mounted just above a regular CRT TV is that the 1197 doesn't have a bucking magnet, nor is it shielded in any way. If you don't mind strange colors, or ghosts drifting around your screen during your regularly scheduled programming, then you can ignore my advice.

Projector/Screens are, OTOH, not susceptible to the above and you can use any speaker you wish.

Best Regards,
TerryO
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Old 21st January 2008, 07:47 PM   #4
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I knew they wouldn't match up. Unfortunately, they don't make the midbass driver anymore. I may have to just have to do a whole new front/center set-up.

I have thought about the Pioneer B20 with tweeter for a budget set-up. I would use the 1197's, but I only have two of them and it's hard to find any more.

Thanks for your input.
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Old 22nd January 2008, 04:51 PM   #5
GM is offline GM  United States
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OK, let's experiment. These drivers have had various specs over the years depending on when/where they were made, so based on the specs I'm familiar with you'll need a ~0.24 - 0.44 ft^3 net cab for two, so make the large one and be prepared to reduce its Vb if it sounds too under-damped once the vent is tuned.

Physically couple the two together motor to motor to create a shielded bipolar driver assy. and measure the distance between the mounting flanges and subtract a little for gasketing, so that once mounted the motors are magnetically clamped/coupled.

This is your cab's outside dim. Now work out the other dims and assuming an 80 Hz XO to your sub, then experiment with different length 2" i.d. diameter vents to find the best blend. If you're using a lower XO point, then you'll need to add a lower Fs mid-bass driver on the rear and the bipolar 40-1197s will need to be isolated in a ~0.16 ft^3 sealed section.

You'll have to experiment with how much the rear driver's mids/HF needs to be rolled off to sound ~tonally flat with either acoustic damping in front of the cone or trying various inductor values. FWIW, being a believer in acoustic solutions for acoustic problems, I recessed the rear baffle so I could add damping without it being visible.

The stock 40-1197s I've used rolled off around 14 kHz, which for a CC is probably a good thing, but they beam enough that for a CC app a super tweeter is desirable to get a more uniform response over a wider listening area, so I recommend you use the same tweeter as your mains with a XO that best blends to your mains.

Of course if you have measured your drivers, then use these specs to design the cabs.

GM
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Old 22nd January 2008, 08:58 PM   #6
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Quote:
Originally posted by GM
Physically couple the two together motor to motor to create a shielded bipolar driver assy.
We built the GM designed self-sheilding ML-TL centre channel. It is a really clever design and works well, As the customer upgraded it became surplus. It is up for grabs at a song, That would leave you with 2 1197s (and if you need more i have a few kicking about) to use as mids in new LR mains.

We found that an 8 ohm "super-tweeter" with a 2 uF caps does a good job of adding air to the top of the 1197. There is quite a bit you can do to turn the 1197 from a value leader into a very serious driver.

dave
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