First look at a high performance PR test sub. - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 13 Old 08-25-2019, 10:16 AM - Thread Starter
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First look at a high performance PR test sub.

Here are a few pictures of a new PR design we're trying out.

21 inch Ipal woofer
dual 18 inch PR

Trying a few different amps with this right now and just beginning the tuning process. So it will be a bit before we can make any determination on this making into production.

The thought process behind it was similar performance to the TV36ipal at about half the size. Someone mentioned it reminded them of the sunfire true subs. I can see that. These are quite a bit larger of course...about 8x in fact.

So 8x larger, maybe 4x more expensive, but around 20x more powerful.

The PRs are mounted inverted now so I can add weight easily. Any final design will have them oriented normally.

Right now I can only get the tune down to 19hz. I purchased a 2.5" dimeter, foot long lead rod and cut it down. But it's not enough mass. I'm getting a 3.5 inch diameter lead rod here this week. That should do it.

Tom V.
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post #2 of 13 Old 08-25-2019, 10:54 AM
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Looks awsome Tom

How much weight are we talking about pr PR here?

Dual AVR 13.1.8 SWAtmos - Atmos 13.1.8/DTS X 9.1.8/Auro 3D 13.1 - Denon AVCX8500H+AVRX7200WA - Klipsch+KEF - 4xSI18" - 12x12" w/6xSLAPS M12 VNF - 4x12"HB+2x18"CLHB - 6x Crowsons - 4xBK-LFE - 2x12"BB - 2x "4DX" fans- 6xNU6K - Minidsp 10x10HD-Vertex2-Oppo UDP203-XB1X-ATV4K-JVC RS600-Dreamscreen V2 120"-Samsung QE82Q60.
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Last edited by Tom Vodhanel; 08-25-2019 at 11:15 AM.
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post #3 of 13 Old 08-25-2019, 11:04 AM
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Quote:
Originally Posted by Tom Vodhanel View Post
Here are a few pictures of a new PR design we're trying out.

21 inch Ipal woofer
dual 18 inch PR

Trying a few different amps with this right now and just beginning the tuning process. So it will be a bit before we can make any determination on this making into production.

The thought process behind it was similar performance to the TV36ipal at about half the size. Someone mentioned it reminded them of the sunfire true subs. I can see that. These are quite a bit larger of course...about 8x in fact.

So 8x larger, maybe 4x more expensive, but around 20x more powerful.

The PRs are mounted inverted now so I can add weight easily. Any final design will have them oriented normally.

Right now I can only get the tune down to 19hz. I purchased a 2.5" dimeter, foot long lead rod and cut it down. But it's not enough mass. I'm getting a 3.5 inch diameter lead rod here this week. That should do it.

Tom V.
Team Power.
Hi Tom,

Love the idea of a 21” sub, great work! Have you considered using an internal or external SpeakerPower 4000W Amp? Would it add too much to the final cost?

I would love to add a pair of these to the rear of my room.

Thanks,
Jerry

Main: 3 x JTR 212RT | Surrounds: 2 x JTR 110HT | Subwoofer: 1 x JTR Captivator 4000ULF-LP | 2 x Crowson Motion Actuators w/ Crown DSi 4000
Amplifier: DAC 5-Cherry | Processor: Monolith HTP-1 | Projector: JVC DLA-NX7 | PJ Screen: SeymourAV 130" W 16:9 Center Stage XD
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post #4 of 13 Old 08-25-2019, 11:14 AM - Thread Starter
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Originally Posted by pitchcut29 View Post
Hi Tom,

Love the idea of a 21” sub, great work! Have you considered using an internal or external SpeakerPower 4000W Amp? Would it add too much to the final cost?

I would love to add a pair of these to the rear of my room.

Thanks,
Jerry
Using a 4000w torpedo(sp) on it now.

I've never found passive+separate rack amp demand to be worth pursuing. Going all the way back to the svs b4+ sub(circa 2003?) there's just never been much there. The watt/dollar ratio gets worse, you have more end support, etc.

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post #5 of 13 Old 08-25-2019, 11:15 AM - Thread Starter
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Originally Posted by Nalleh View Post
Looks awsome Tom

How much weight are we talking about pr PR here?
I'd have to double check but IIRC there's about 1275g per right now(just in added lead).

The 3.5 inch lead rod, cut to size, that's going to be another $400(ish) but it should allow me to add as much as needed and then some.

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post #6 of 13 Old 08-25-2019, 11:57 AM
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^^ Thanks Tom

Very exciting, can’t wait to hear more about this one

Dual AVR 13.1.8 SWAtmos - Atmos 13.1.8/DTS X 9.1.8/Auro 3D 13.1 - Denon AVCX8500H+AVRX7200WA - Klipsch+KEF - 4xSI18" - 12x12" w/6xSLAPS M12 VNF - 4x12"HB+2x18"CLHB - 6x Crowsons - 4xBK-LFE - 2x12"BB - 2x "4DX" fans- 6xNU6K - Minidsp 10x10HD-Vertex2-Oppo UDP203-XB1X-ATV4K-JVC RS600-Dreamscreen V2 120"-Samsung QE82Q60.
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post #7 of 13 Old 08-25-2019, 04:23 PM
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If this works- I'll be bringing you my pair of S3000i and taking home a pair of these.


I'll make the drive out and back to avoid shipping both ways.
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post #8 of 13 Old 08-26-2019, 03:55 PM - Thread Starter
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Size perspective shot. Makes a good MT110 stand.


Tom V.
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post #9 of 13 Old 10-11-2019, 03:06 PM
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Quote:
Originally Posted by Tom Vodhanel View Post
Size perspective shot. Makes a good MT110 stand.


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Any update as to the progress of this project? (wether it'll make it to production or not?)
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post #10 of 13 Old 10-12-2019, 12:21 PM - Thread Starter
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Any update as to the progress of this project? (wether it'll make it to production or not?)
The PR design got pushed way down on the things-to-do-list due to everything else going on(new 12 series upgrades and value lineup) combined with a 75% increase in sales versus 2018. We've added 4 new people in the last 5 months...probably a few more needed within the next 5 months as well.

Anyway, I don't know if there's ever been a PR sub tuned <15hz. As least not a viable commercial design. So there's some unique challenges involved in this project.

We had to make some major mods to the PRs just to get them to accept the mass involved tuning this low.

Progress is being made, but it's going to be a while before any decisions are made to bring it to the market or not. Best case would be 6-8 weeks, but first quarter 2020 is more likely.

See attached. Those little skinny washers are what is typically used for mass loading a home theater PR design. The 2 inch thick lead is what I used initially for ours. I had to move to 3.5 inch thick(!) lead to get what I wanted.

Tom V.
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post #11 of 13 Old 06-08-2020, 07:45 PM
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Given the relative small enclosure size for a 21" driver, do you guys incorporate much in the way of EQ filters in the circuitry to pump up the low end response to counter the smaller box sizes? This is a question I have for some of your other sealed designs also.
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post #12 of 13 Old 06-08-2020, 07:51 PM - Thread Starter
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Given the relative small enclosure size for a 21" driver, do you guys incorporate much in the way of EQ filters in the circuitry to pump up the low end response to counter the smaller box sizes? This is a question I have for some of your other sealed designs also.
This one wasn't that bad. It's actually a decent size effective volume for a 21. About 7 cu-ft iirc. But as with most/all subs there will be some digital work involved to get the final FR shaping to (what I would consider) perfection or nearly so..

I just started with the TV42 curves and made a couple of minor tweaks to get it in the ballpark.

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post #13 of 13 Old 06-08-2020, 07:55 PM
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Originally Posted by Tom Vodhanel View Post
This one wasn't that bad. It's actually a decent size effective volume for a 21. About 7 cu-ft iirc. But as with most/all subs there will be some digital work involved to get the final FR shaping to (what I would consider) perfection or nearly so..

I just started with the TV42 curves and made a couple of minor tweaks to get it in the ballpark.

Tom V.
Team Power.
That's pretty neat. I have always wondered about whether there was some DSP magic going on. Even in my s3600 I am blown away by the depth it can reach in what is a relatively small box for TWO 18" active drivers.

Can I assume that the EQ filters pushing up the low end is why there's a necessity for such powerful amplifiers, as it requires tremendous power to amplify the lowest of lows, especially when you're using an EQ to push its up beyond normal? As a relative "lamen", when I see a sub with an 1800 watt RMS amplifier, coupled with main speakers that 'only' have 100-200 watt RMS amplification, I always wonder what that extra power is for!
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