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Three way speaker with R45" ribbon
Three way speaker with R45" ribbon
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Old 26th September 2018, 01:03 AM   #11
Gwho is offline Gwho  United States
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Join Date: Oct 2008
Damic,

I will likely build the bass part of the speaker first. I can try it up to 1Khz to see how it sounds. I'm not optimistic as I have read somewhere that the RSS256HF has issues around 1Khz and was suggested to cross at 350hz or lower.

Regards,
gwho
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Old 29th September 2018, 02:28 PM   #12
lowmass is offline lowmass  United States
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Originally Posted by Gwho View Post
Lowmass,

One last question. Have you tried an array of inexpensive mid woofers. For example, the GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer ($8.50 parts express) or MCM 55-1240 - Cone Woofer, 8", Clear Polypropylene, Low Frequency ($13.99 Newark) would seem to work in a sealed enclosure and provide possible 100hz cut off. Any idea if this would be worse or better than a single or dual point source (higher quality woofer) since it would provide the same array radiation pattern as the ribbon. My concern would be that the an array of lower quality woofers may output lower quality sound (at this time I would not want to pay for 12 or 16 $150 mid woofers for this experiment).

Best Regards,
gwho
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Old 29th September 2018, 02:43 PM   #13
lowmass is offline lowmass  United States
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IMO this is a very good question.

Yes I have done it in "cheap" woofers BUT not the ones you mention. I used some really cheap 5, 6 inch and 8 inch plastic woofers I bought from radio shack during some closeout sale many years ago.

They all had simple motors, basic foam surrounds, and poly cones. Nothing at all exotic.

They worked surprisingly well. All of them.

They were all well behaved up to about 3-4 khz and I was crossining between 400 and 1 khz. The sheer number of the drivers meant that they did not have to move much at all and therefore a good motor and suspension simply was not needed.


So yes if it were me and I was going to do a "line" of cones, and my cross was 1K or lower, I would find a decent 6-8 inch "cheap" cone with a smooth response out past 2-3 khz AND that gives the desiered lower freq perf in the size box I want.

When theres a bunch of small cones that hardly move at all and are not taken to the upper midrange , theres a big advantage. You can go cheap and still get ALL the perf of the really expensive cones. In fact IMO its often better. The cheap cones are often very light small motor etc, when in the right setup and not being asked to do anything up high in mids or to make big peak to peak swings in bass, they seem to have an advantage over even the exotic cones. Especially in mid bass dynamics.

Last edited by lowmass; 29th September 2018 at 02:51 PM.
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Old 29th September 2018, 04:58 PM   #14
lowmass is offline lowmass  United States
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Quote:
Originally Posted by Gwho View Post
Lowmass,

One last question. Have you tried an array of inexpensive mid woofers. For example, the GRS 6PR-8 6-1/2" Poly Cone Rubber Surround Woofer ($8.50 parts express) or MCM 55-1240 - Cone Woofer, 8", Clear Polypropylene, Low Frequency ($13.99 Newark) would seem to work in a sealed enclosure and provide possible 100hz cut off. Any idea if this would be worse or better than a single or dual point source (higher quality woofer) since it would provide the same array radiation pattern as the ribbon. My concern would be that the an array of lower quality woofers may output lower quality sound (at this time I would not want to pay for 12 or 16 $150 mid woofers for this experiment).

Best Regards,
gwho
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Old 29th September 2018, 05:22 PM   #15
Bfpca is offline Bfpca  Canada
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Three way speaker with R45" ribbon
I had newform 645s for a few years. Here is some of what I learned about them through several years of experimenting. The best way to go is to bi amp with a low level cross over IME. The stock 645 had 2.7 ohms of resistance in series with the 2 paralleled SS 8545 drivers to match the sensitivity to the ribbon. Not a real good use of a high quality driver IMO. Big improvements were had using low level cross overs and bi amping. The ribbon driver itself weighs something like 45 lbs and is basically a long steel tube open on one side. If you fasten it directly to the top of the box it tends to ring IIRC at about 220hz. Some isolation is definitely needed.
Although rated to go down to 1khz I had better luck with higher crossover points. I always heard a coloration at lower crossover points. I think a first order crossover is too shallow for high output levels when set at 1khz. I used a Marchand Electronics 4th order LR crossover which seemed to work better, but I never really got the sound I wanted in my mid sized rectangular room. Eventually I sold them and moved on.
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Old 29th September 2018, 06:40 PM   #16
Gwho is offline Gwho  United States
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Lowmass,

Once again, thank you for the input. I am glad you saw merit to a line array of lower cost midwoofers. In reading about line arrays it seems there are many that do not like them, especially in a short array. I also did not want to buy 16 $150 > woofers just to try it out. So your input was invaluable to me.

I know this is a kluge but I tried the ribbon with a couple of speakers just to see how they sounded. I used an Ashly analog crossover (24db/octave) to cross the ribbon to two different speakers. I first crossed the ribbon to an old Snell Type C speaker at 1K. I believe the Snell uses Vifa drivers (4" and 10").

The other speaker is more of a HT speaker. It is a Mirage OS3-Fs. I don't believe it is a line array but it has two 4.5" midwoofers and (5)-4.5" passive speakers to generate low frequency. The Mirage also has an omni tweeter/midrange that distributes sound in all directions under the top cap. I listened to the mirage with the cap covered by cloth and open (as there was output from this speaker when crossed at 1K.

I tried to match the gain of the speakers with a radio shack meter. They did sound different from one another. The Snell combination obviously had a lot more bass. Interestingly, I liked the Ribbon/Omni combination better which is why I asked the question about an array of sealed budget midwoofers.

Best Regards,
gwho
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Old 29th September 2018, 06:46 PM   #17
Gwho is offline Gwho  United States
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Bfpca,

Thank you for sharing your experience with the 645 Ribbon. I will definitely biamp or triamp with the final version of this speaker. You are correct that the ribbon is very heavy. I will play around with the crossover frequency per your suggestion. Also, you mentioned isolation of the ribbon to the box. How would you do this? Would you put some type of isolation material between the box and the ribbon mount?

Regards,
gwho
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Old 29th September 2018, 07:54 PM   #18
Bfpca is offline Bfpca  Canada
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Join Date: Feb 2007
Location: Nova Scotia
Three way speaker with R45" ribbon
I ended up building better braced boxes than the stock ones. The bracket is usually mounted to the inside of the box with silicone caulking to give some vibration isolation but given the heavy weight of the ribbon it still needs to be fixed securely. I put sorbothane under the ribbon and also between the ribbon and the mounting bracket. I also isolated the mounting bolt from the bracket with a rubber washer and I machined off the threads where the bolt would have contacted the bracket. So the bolt did not have any direct contact to the bracket/box.
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Old 29th September 2018, 08:07 PM   #19
Gwho is offline Gwho  United States
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Bfpca,

Got it. I will definitely attempt to isolate the Ribbon from the box to which it is mounted. I do like the sound of the Ribbon. Thanks for the help.

Regards,
gwho
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Old 30th September 2018, 07:04 PM   #20
Gwho is offline Gwho  United States
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Would appreciate any suggestions that people have tried on a budget woofer for a short line array that works in a sealed enclosure from 100hz to 1-2K.

Best Regards,
gwho
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