PAP Trio style DIY OB with PRV drivers

atharva

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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.


IMG_20210116_170801_01__01.jpg

Videos used for MiniDSP eq


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Attachments

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  • left-right-woofer-jan16-night.jpg
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yogibear

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These need just the right amps to sound perfect. A Tube amp for the FR and with those woofers at narrow baffles, a good SS amp crossed at 200hz. A little boost around 32-35hz will set everything just right. No sub needed. They will move the house. Those 15” monsters together make 103dB sensitivity.
 

arunkvivek

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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.
 

yogibear

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Dont route the FR through the minidsp. Use DSP only for woofers to cross and boost. Placing the FR in middle will give more baffle / acoustic length to FR and make it sound warmer. But what it does to bass, I am yet to experiment and find out, though I prefer the woofers to close enough to work in unison. The big legs of the build seem to be raising the whole build pretty high. Good for big rooms though where you can sit far from the setup. Its another experience.

If you have a 3 way stereo minidsp then cross it 2.5 way. Much better for narrow baffle builds.
 

atharva

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@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.

WhatsApp Image 2021-01-17 at 3.27.12 PM.jpeg
 

yogibear

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Try boosting 6dB around 32-35hz. These drivers are very accommodating to boost. I tried 12dB with absolutely no audible distortion and they dug very deep, articulate bass. Though am not sure as how rigid the chassis behind is. It may transfer vibrations to the FR.

You are surely blessed with a huge room to play with them. They are surely going to shock you with what comes out of them after some iterations.
 

baswamin

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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

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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.
 

atharva

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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.
 

yogibear

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Well yes, miniDSP DAC is not great. But then if you boost bass on the woofers, it has to be routed through miniDSP as boosting it through your player may do harm to FR sonics.

However with two 15" woofers I never found any need to boost the bass but in your case the baffles are small hence the low end suffers.

Freeing the FR from the miniDSP brings out great sonics.

Once you get accustomed to dipole bass, yes its takes some learning and de-learning and when you go back to boxed bass, its very hard to live with it. In short, the "conversion" is permanent !!!

Enjoy your time with OBs. They are very easy to experiment and bring out great joy tinkering with them. Its an emotional connect with music.
 

sbfx

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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.
 
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