High SPL on older hardware

[Wired]

Greetings,

I have a vanilla Foreplay III and a couple of original 2A3 Stereomours. I'm very happy with the hardware, but have been running speakers with ~89db sensitivity and am looking to step up to something with more SPL. To accomplish this, I have (4) OB-A15Neo woofers from PAP that have 94.6 SPL and have on order a pair of Eminence N314x-8 compression drivers that have 110.5db sensitivity. The speakers will be bi-amped with the Stereomours.

This is my first foray into high SPL horns. The horns are on backorder, so I have no first hand experience as to what to expect from the Foreplay/Stereomour. I'd be happy to hear from anyone in the community that has experience with high SPL/older hardware setups like this and any gotchas I should be aware of.

[Gerry E.]

Hi Rick:

I run a custom Pure Audio Project (PAP) system with a pair of BH Paramount amps (see photos below).  I also bi-amp but at a very low crossover frequency using a pair of subwoofer plate amps.  In order to get you moving in the right direction, I/we need answers to these questions:

1.  Is it correct to assume that you are going to run the drivers on an open baffle?  If yes, do you have PAP frames?
2.  What are you going to use for a horn for the Eminence compression drivers?  Eminence has at least two options for 1.4" throat: a line array wave-guide or a exponential horn.
3.  If you have PAP frames, are you going to have PAP custom cut a center baffle board for the wave-guide or horn?
4.  What is crossover frequency?  It looks like 800 - 1200hz would work well.
5.  What are you going to use for a crossover?

Obviously, you will have to deal with the SPL mismatch of the woofers and compression drivers but the answer to question 5 will help determine this.  Since you have identical stereo amps, I would recommend horizontal bi-amping vs. vertical.  This way, depending on your setup, you could have the amps very close to the speakers.  This would allow very short speaker cables which is what I have.   

This is enough to think about for now!

Gerry

[Wired]

Hi Gerry, thanks for your reply

1) Yes, the intention is to run them open baffle. I don't have PAP frames nor their baffles. I bought the raw OB drivers directly from PAP back when they were still available as a line item.

2) I have the Eminence 60x40 exponential wave guides.

3) Once I finish prototyping, I have all the wood, equipment and needed skills to make the frames/baffles myself.

4&5) I happen to have an 800Hz active crossover.

SPL Mismatch:
I've been bi-wiring the Stereomours hoizontally and using their attenuator to match SPL. I don't usually consider vertical bi-amping because in my environment it would mean line level runs in excess of anything I'd be comfortable with. 
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Other questions I have with regard to high SPL speakers include: What can I expect in terms of background noise? Will the choice of interconnects/lengths become more critical? Will I need to pay more attention to power conditioning? Device placement? Cable runs? Does microphony become an issue?

Right now, I'm at the prototyping stage and looking at various configurations. 

[Larpy]

Other questions I have with regard to high SPL speakers include: What can I expect in terms of background noise? Will the choice of interconnects/lengths become more critical? Will I need to pay more attention to power conditioning? Device placement? Cable runs? Does microphony become an issue?

A few years ago, I swapped out a conventional high-powered PP tube amp and low-efficiency speakers for a Kaiju and Lii Audio F-15s in an open baffle configuration (96 dBs or so SPL).  I did hear heater hum with the stock Kaiju kit, but the DC heater upgrade took care of it.  Otherwise, I didn't experience anything unusual with my new set up.  No need for power conditioning, etc.

As you probably know, open baffle speakers need a good 3' between them and the wall behind them to sound their best.  That's one difference I did experience: my speakers are now further out in the room than in the past.  But the dramatically improved soundstage is worth it.  I'm an OB convert now.

[2wo]

Larry,  can I see a picture of your F-15's?

I too have circled back to OB speakers. I have a set of F-15's, "  temporary" mounted to some thin particle board. I am still recovering from a bike accident in June, so any project requireing two arms is on hold but looking at options...John

[Wired]

@Larry, thanks for sharing your experience.

I haven't really had much issue with speakers that have SPL in the mid 90s. I should mention that I have tested the PAP OB drivers and an ESS Great Heil (they're both ~ 95 SPL) and both were quiet to the point I couldn't hear any noise from my listening position. The compression drivers I want to use, however, add another 15.5dB of sensitivity.

I'm still optimistic. I'm aware that the Stereomour's 2.5v AC heater can't be converted to DC, but new DC circuitry can be added in. Or a new amp... Or just live with it

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Regarding the OB speakers I'm building, here's a new pic.

This OB design will have minimum baffle width across the front. The baffle is instead wrapped around to the sides. In the pic, the width is about 16" and it's 55 1/2" tall to the top of the speaker. I'm liking the proportions, it kinda reminds me of a floor standing clock.

If there's interest and if it's allowed, I'll start a proper build thread.

[Larpy]

Larry,  can I see a picture of your F-15's?

Sure.  In fact, I'll show you three, in the order of their evolution in my listening room.

First photo: in their initial large barrel shaped baffles made from 3/4" Baltic birch ply.  Sounded great but not much bass below 60 Hz.

Second photo:  considerably slimmed down baffle set atop open baffle subwoofers (which are powered by plate amps),  Limited bass extension addressed. Plenty of bass now down to 30 Hz.

Third photo:  solid cherry baffle (1 1/2" thick) with added "supertweeters" to augment frequencies above 8K Hz.  This is the current configuration and I'm pretty happy with it.

[2wo]

Hi Rick,
I have used a number of drivers in your SPL range including the Heil's with 2A3's and mostly 45's and have been able to null the hum with AC heating and the hum pot, to the point that I have not felt the need for D.C..

Not sure about those +15db compression drivers but consider, the residual hum is 50/60Hz...John

[2wo]

Thanks Larry,

I am very familiar with Randy's barrels. My last setup was Betsy's over a pair of  Hawthorne 15" woofers and was thinking about something similar with the F-15's...John

[Wired]

I run a custom Pure Audio Project (PAP) system with a pair of BH Paramount amps

I've been meaning to circle back with you and fire off a barrage of questions I have about those very cool custom speakers you have I don't think I've seen another PAP with dual drivers mounted on a single baffle before. They look great

What wood are the baffles made of?
Are those the original PAP drivers I see there, or another of the Eminence Neos?
What drivers do you have on the mid-baffle?
Xover points?
Impedances of speakers/amps?

I kinda have a soft spot for the PAP. I ran across the project back when I was still doing basic research on OBs. At the time, their drivers were still available as line items and so I picked four of them up, as they seemed an easy OB bass solution.

I'll move further build details to a proper thread. Hope to see you there!   

[Wired]

I'll show you three

That's very interesting being able to see the design progression. What's the time frame? That cherry block is beautiful!

[Wired]

but consider, the residual hum is 50/60Hz...John

Thanks for reigning me in John, I think these other guys were gonna let me run with it for a while yet lol

Interesting that you mention the 45s, I've been wanting to convert one of the Stereomours over for a long time and SPL matching with the OBs could be the trigger. I'll leave further discussion for the build thread.