PAP Trio style DIY OB with PRV drivers

[atharva]

Hi all,

Hope you’re having a good Sunday. This post comes on the heels of FM @Fiftyfifty's Audio Nirvana OBs. I learnt about OBs very recently when looking to upgrade the Rethm Maarga. After doing some reading I was keen to try them. @Fiftyfifty had already ordered the ANs and suggested I speak to our @yogibear who gave me a good background of what to expect. A huge thanks to both of them.

It was almost unbelievable when a kind gentleman in Pune lent me his OBs to try at home. I'm sharing his DIY not mine. I jumped at the opportunity and got a MiniDSP 2x4HD and UMIK-1 to play around and tinker. The MiniDSP is awesome as it allows me to play with crossovers infinitely. It's just been a day since I set it up. So a lot to learn.

The configuration is 2x10" fullrange PRV 10FR300PR and 4x15" woofers PRV 15W1000V2. Frame dimensions are 5'2"Hx22"W and they dwarf my Maargas which I used to think were big! The fullrange are driven by a Valvet and the woofers by a NAD.

I tried three methods.
1. No EQ and Basic XO. I tried 80, 100, 140, 180, 200 Hz.
2. I did measurements (at listening position with the mic pointing straight ahead) and tried to eq the FR and woofers. I don't think I did the EQ right. I used the videos below as guides. I'm attaching my measurements so someone can suggest what to try. Unfortunately I can't attach the original REW file as it's too big. I'm using the House Curve as suggested.
3. Bypassed the EQ and XO for the fullrange.

Impressions..

The first thing I noticed is a 3D sound with a big soundstage. The bass is good and punchy. Quite enjoyable. The tonality of the full range is not quite right. The Maarga is much more refined and tonally accurate. For example, a piano or santoor sounds fine until you hear the Maarga. May be a super tweeter will help? There is good mid bass but it gets bloated towards the lower end. Need to try placement and/or H-frame. But heck, not bad at all. Honestly, not what I expected by slapping drivers on a flat baffle. In short I think there is a lot of potential if done right.

What next?

- Better drivers. I'm not sure if the PRV fullrange is considered on par with drivers like Fane/Beyma/Audio Nirvana/Tang Band. Woofers apparently are quite good. Lii drivers would also be interesting but shipping from China is presently an issue.
- Try H-Frame for the woofer
- Fullrange in the middle (WFW configuration). This will bring the FR at ear level.
- Hoping someone can guide me on the EQ front to fix some of the anamolies.
- Try a super tweeter.




Videos used for MiniDSP eq

.

 

[arunkvivek]

H frame does tighten up bass well.. I think you can bring the setup at least a feet or two further closer. H frames SW at my place sounded the best when they 1.5M behind them. The bass is bloated when I move them closer to the walls.

 

[atharva]

@arunvivek, I moved the speakers 5ft from the front wall and there is improvement. Don't get me wrong, the bass is excellent but if I can get it a bit more tight I think it'll be perfect. Will experiment more with placement.

@yogibear, I already swapped the drivers as you can see below. The FR is now at ear level and sounds much better. I'm going to take measurements again tonight when the noise floor is a bit low.

 

[baswamin]

Nice work @atharva. I think when bypass the FR from minidsp, it is better to disconnect the FR fully from minidsp and drive it directly from the amplifier. I think this is what you have done but wanted to check.
Plugged in and interested to see the findings.

Thanks
Balaji

 

[sbfx]

I've been a PAP OB user for a little less than a year. I've spend the full lockdown with them so I've really gotten to know them and have suffered the nasty break-in too.

A OB to me is unlike another speaker *if* you have the sufficient space from the front wall. I'm using the First order XO modified by better Mundorf Caps and Coils along with a Solid State amp. A lot of PAP users are excited about tube amps but when I tried a couple I was seriously disappointed they did not only suffer on micro detail but macro was missing too.

I use my OB around 5.5 ft from the front wall and have clean under 28hz bass, there is no compression regardless of SPL, this feeling is unparalleled. I've been using boxes since the last 15 plus years. The OB has been an mind bending experience for me in audio.

Next project for me would be to biamp with a analog active xo, need to find affordable great 4 ch's or maybe try and get another 2 ch of my current amps.

 

[sbfx]

1st Order Crossover Updates;

Mundorf Supreme Oil 66uf + Mundorf Supreme Silver Gold Oil 2.2uf total 68uf High-pass.

Mundorf VSCU 8.2mH coils for Low pass.

This setup bettered my ex speakers that were around 6x the sticker price.

 

[atharva]

Thanks @yogibear and @baswamin.

I suppose the idea of disconnecting the FR from the MiniDSP (not just bypass it) is so we can use a better DAC - RME in my case?

In order to do that I have 2 options..
- parallel the outputs of the RME - one to the tube amp, the other to the MiniDSP analogue inputs. In this case it will be Allo (Coax) -> RME -> one to tube amp and the other to analog inputs of MiniDSP. In this case the MiniDSP will first do A2D then xo/eq and then D2A. I don't know what effects the additional load will be on the RME and the double conversion of the signal (although only for bass) but shouldn't introduce timing issues.

- parallel the digital outputs - one to the RME and the other to the MiniDSP. My Allo Digione Signature has Coax and BNC connectors. I've ordered a BNC to Coax connector and Coax to Optical converter. Then I will have
Allo (Coax) -> RME -> Tube Amp -> Full Range.
Allo (BNC) -> Coax to Optical -> MiniDSP -> Woofers. (Wish the MiniDSP had Coax input so I could avoid the Coax to Optical converter)

BTW, the bass of the OB is fantastic. I would prefer it to be more articulate and tight. I might get into trouble for saying this but right now the OB is more "fun" to listen to than the Maarga.

I will try @yogibear's suggestion to boost the bass but I'm still learning about how to do EQ with the MiniDSP. I should start a separate thread on that so some experienced people can tell me how to achieve that.

 

[Naveenbnc]

I would prefer it to be more articulate and tight.

regarding tight and articulate bass, recently Nishant achieved it without any EQ.
He shared some recorded videos, and its simply fantastic !!!

 

[jmascreen]

is there any isolation between floor and OB?

 

[sbfx]

I've not tried a dsp but passive network gets me around 27hz in room clean measured. Room size 12x24.

 

[Naveenbnc]

A little taste of what OB bass is about:

Damn good !!! couldn't ask anything more

 

[atharva]

Nice. What track is that?

@sbfx, it is interesting that you are using the passive with the Trio 15.

 

[sbfx]

Yes its a very simple 1st order XO. Total part count is 5.

Bass is a forte of the OB if big enough drivers are used along with enough juice from the amps. The interaction with the room is dramatically lower vs what a box would behave like therefore they reproduce bass with much less room interaction.

 

[malvai]

A little taste of what OB bass is about:

very 'closed' kind of sound.... don't mean to criticize... but, this is far... far away from live-sounding drums

 

[Naveenbnc]

very 'closed' kind of sound.... don't mean to criticize... but, this is far... far away from live-sounding drums

Criticism pushes us to improve further. I personally liked it, and I think regular sealed or ported home theater subs won't sound this good for drums. However since you are giving a different opinion, can you share any other recording which you think is better please ....

 

[jenson]

geat looking speaker atharva! those 15 inchers look amazing, must play like in concerts some videos would be droolworthy

 

[Fiftyfifty]

@atharva I see some glass windows behind the speakers and on the side. In my setup, glass has a higher huge impact on bass and soundstage.

 

[atharva]

@jenson thank you for the compliments but actually that was a pair on loan. Here is a pic of what I built..

This is with Tang Band 1808 full range. I tried FaitalPro 3FE25 and Mark Audio 12p but like this much better. I had the FRs mounted in the center but later learnt thats a bad idea as it causes symmetrical edge diffraction. I modelled this in Basta and chose a suitable offset. The lockdown forced me to get creative and I was able to use cardboard from really big boxes. Three of these together make it very stiff.



@Fiftyfifty, ideally we don't want any reflective surfaces. But the interesting thing with flat panel OBs is that the response to the sides (90 degrees off-axis) is completely nulled by the out of phase front and back. So there is little to worry about what we have at the sides. The glass window at the back is not exactly behind the speakers and much less after toe-in. IMHO it doesn't interfere much. Keeping the speakers as far from the wall behind (5' in my case) also helps reduce the interference of reflections with the direct sound.

But I'd love to try acoustic panels some time. Any suggestions in Pune?

 

[SwaroopKS]

How do Saadhanas compare with the open baffles? Given both have FRs at the core of their implementation, interested to know your impressions.

 

[jenson]

How do Saadhanas compare with the open baffles? Given both have FRs at the core of their implementation, interested to know your impressions.

Must be night and day kinda difference