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naked OB speaker
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Author:  ratbagp [ May 29th, 2019, 11:29 am ]
Post subject:  naked OB speaker

I posted recently about the curious naked speakers with the PRV 5MR450-NDY along with 18" woofers. Scroll down to the end of the following.

https://www.trans-fi.com/ob-speakers

More about the PRV here
https://www.parts-express.com/prv-audio-5mr450-ndy-5-midrange-neodymium-woofer-8-ohm--294-2705

I'm thinking of doing something like this but without the very heavy 18" woofers. 44 pounds per woofer is way too much for me these days. And I don't play music that loud and mostly I listen to classical. I would just use one PRV per channel.

Instead, I am thinking of two options. I already have a couple of the Goldwood 18" woofers that Roscoe also used. I could get a couple more.
https://www.parts-express.com/goldwood-gw-1858-18-pro-woofer--290-386

Or I could try the GRS 15" units with 4 for about $100.

https://www.parts-express.com/grs-15pf-8-15-paper-cone-foam-surround-woofer--292-415

Both Goldwood and GRS speakers have a high QTS suitable for open baffle and they are relatively lightweight. I suspect that mounting the woofers facing each other creates some sort of SLOB effect which I seem to remember is supposed to lower the fs.

Suspending the speakers should not be too difficult. Certainly, I would not be doing all the steel pipe stuff. The speakers would be visually interesting and different.

In a small room it would not require too much power to run the PRVs and the woofers could be handled by a separate more powerful amp. Crossover with a Minidsp or similar.

Any comments or ideas.

ray

Author:  Stuart Polansky [ May 29th, 2019, 12:02 pm ]
Post subject:  Re: naked OB speaker

S.L.O.B. would require that they be wired anti-phase.

Author:  Roscoe Primrose [ May 29th, 2019, 1:27 pm ]
Post subject:  Re: naked OB speaker

Stuart Polansky wrote:
S.L.O.B. would require that they be wired anti-phase.


Not if they're mounted facing each other...

Roscoe

Author:  Stuart Polansky [ May 29th, 2019, 2:13 pm ]
Post subject:  Re: naked OB speaker

Roscoe Primrose wrote:
Stuart Polansky wrote:
S.L.O.B. would require that they be wired anti-phase.


Not if they're mounted facing each other...

Roscoe


That wasn't my image of what was suggested. My bad!

Remedial reading comprehension for me! Ray did write that in plain English!

Author:  mix4fix [ May 29th, 2019, 2:39 pm ]
Post subject:  Re: naked OB speaker

Could you use tweeter and midrange instead of a full-range driver?

Author:  Roscoe Primrose [ May 29th, 2019, 3:04 pm ]
Post subject:  Re: naked OB speaker

mix4fix wrote:
Could you use tweeter and midrange instead of a full-range driver?


Yes, but:

1: Most midrange drivers don't go down low enough to meet the large woofers needed for this type of design. A "midbass" driver would probably be a better choice.
2: Most tweeters have sealed backs, to you won't get the dipole radiation pattern you'd get with a full-range driver unless you mount a second tweeter pointed backwards and wired out of phase. You may want to pad the second tweeter down a bit as well.

Roscoe

Author:  mix4fix [ May 29th, 2019, 3:18 pm ]
Post subject:  Re: naked OB speaker

Just asking. I want to use those drivers I got from Tom.

Author:  ratbagp [ May 29th, 2019, 3:43 pm ]
Post subject:  Re: naked OB speaker

I am thinking that using two woofers per side makes exceeding xmax less likely than just having one. It may also make suspending the woofers easier. I was wondering if there was a special distance needed between the woofers, but since there is no SLOB effect, then I presume it doesn't matter.

Possibly I could use pvc pipe for the frame and possibly fill it with sand. A triangular shape comes to mind. Any other ideas? I would use some sort of dowel or long bolts to separate the woofers and then suspend the set of two woofers by a piece of one of those exercise bands. The yellow would be quite fetching.

Each PRVs could be suspended by a heavy-duty rubber band.

This might be worth playing with.

ray

Author:  Stuart Polansky [ May 29th, 2019, 4:06 pm ]
Post subject:  Re: naked OB speaker

Roscoe Primrose wrote:
mix4fix wrote:
Could you use tweeter and midrange instead of a full-range driver?

2: Most tweeters have sealed backs, to you won't get the dipole radiation pattern you'd get with a full-range driver unless you mount a second tweeter pointed backwards and wired out of phase. You may want to pad the second tweeter down a bit as well.

Roscoe


Or

Attachment:
Opposing-Tweeters.PNG
Opposing-Tweeters.PNG [ 52.43 KiB | Viewed 904 times ]

Author:  mix4fix [ May 29th, 2019, 4:10 pm ]
Post subject:  Re: naked OB speaker

That's not going to work.

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