Open Source Monkey Box

Wired up a cd player and an old amp (hyped ucd) today for a first listen. First without the port pipes installed, then with them, but not having cut them to size yet. Speakers in the same position as in the picture above. Tweeter Rt2 is 1.0R.

Mids and highs very coherent. I had heard that tweeter before at a show, in the Serhan Swift mµ2 Mk II. That speaker put the tweeter on a pedestal and it sounded very impressive, but I was wondering how I would cope with that long term. The OSMC seems to emphasise integration and the tweeter is less obvious, even at 1.0R.

I will have to wait for the burn in to finish and for the speakers to be placed correctly with the correct ports installed to be sure, but it sounded like there was a peak somewhere in woofer territory. Maybe I will need more stuffing/damping. Unfortunately I don’t have measurement equipment so I will have to work something out.
 
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I have now moved the speakers to the living room. Although the family acknowledges the vast difference in sound (we had modest 6+1 bookshelves before), they are found as too big for our home. I see where they coming from, I need to find a way to move them back by 20cm or so, then we should be good.
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Stupidly I cannot fit the crossovers into the stands because of the speaker terminals. Not sure how to solve that… either saw off the rear top crossbar, or change my cables to speakon and get rid of the terminals. The latter limits cable choices so that’s not so good.
 
Regarding sound, I am still using 1.0R on the tweeters so I haven’t fully dialled in the sound, but I now have a first impression:
  • The first thing I noticed was a relaxed very clear sound, just as has been described for the XA252 amp - the low distortion makes you turn up the volume more because it doesn’t sound loud. Whether that is from the controlled directivity or from the high quality of the mid and tweeter, or more likely both, not sure.
  • To my ears the tweeter and the Volt are on par, their smooth clarity even at really low volumes is a delight. They have detail without sounding analytic or overbearing.
  • They don’t need cranking up to sound good. The woofer sounds more subdued than the other drivers if average volume goes beneath, say, 65db at listening position, at least with my hypex ucd400hg based amp. With my Yamaha B-2 this is not the case, but that amp already delivered bass on my old 6+1 bookshelves that I thought they were not capable of.
  • Their relatively high efficiency and mild horn loading of the mid and tweeter does not result in an overly lively presentation as you would get from a large horn system or 15” tannoys. Obviously. The OSMCs are smooth and relaxed, but not boring. At audio shows I often found low efficiency speakers (<90db) boring.
  • Opera, classical of any complexity or jazz - this speaker is a delight. It can render the atmosphere but does not sound analytical. On modern pop I sometimes find the synth percussion overbearing. Is it that the mix was intended for Bluetooth speakers, or do my enclosures need a bit of tuning? I cannot tell at this point.
For reference, my chain is:
Opticalrendu v1 playing Qobuz via LMS/squeezelite > T&A Dac 8 DSD > Yamaha B-2 > OSMC. Interconnects are diy silver wire, speaker cables are Nordost Solarwind.
 
Thanks. They are now broken I believe, it only took 5 days max on the FryBabies for them to sound settled. I just have to dial in the tweeter resistor and maybe stuffing. But other things are now more urgent, so this will happen in the next few months or so.
 
Is it that the mix was intended for Bluetooth speakers, or do my enclosures need a bit of tuning?

I would not recommend any fine tuning without measurement capabilities. If you have working measurement equipment and learned how to do measurements right, the only thing I would recommend is to confirm your built met the design goals of the OSMC, which is a pretty thoughtful design. I don't see how it could be improved and I would strictly stick to it, only using the component values of the original design.

Re your previous remark about a suspected bass resonance: this could be a room issue. Room correction makes a lot of sense. If only room correction is the task, a USB microphone like the UMIK is a simple way to improve the sound. Understanding Speaker Boundary Interference Response (SBIR), room gain in bass, and the placement of the speakers will help you with that.

In general, if you are not a trained listener, subjective impression and actual frequency response rarely match. I am not a trained listener and I thought I heard the most beautiful presentation when I in fact had totally screwed up the transfer function on my DSP speaker, which was revealed only in the measurements. With a new speaker, it takes a good while until the brain accepts a presentation and gets used to it, even if it is objectively a great speaker. It's best to get used to the speaker for at least a month of regular listening before you want start to improving things. Room correction can be done from the beginning, but then again, you might not accept the very good sound either. Go slowely.

A last remark: if you are running Qobuz on LMS with piCorePlayer, you can install CamillaDSP. There is a most convenient solution created by user @JWahle, available from his github repository and explanations in his thread here: https://www.diyaudio.com/community/threads/camilladsp-for-picoreplayer.402255/


This works reliably and can be used both for room correction, but also to create toning filters. Not all recordings will sound right on a given speaker at a given level, and you might want to implement filters bass and treble toning, or even slope adjustment filters. This, toning filters, however, I can only recommend doing after you got accustomed to the speaker sound.
 
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Thanks a lot for this detailed write-up! Unfortunately I do not have any measurement equipment but I have accepted that I won’t succeed without. The resonance issue didn’t survive the burn in so we are good on that front. With enclosure tuning I merely meant adjusting the stuffing. At the moment I have Basotect roughly as described in the manual plus 100g of unicorntail per enclosure instead of the wool. Maybe I need more stuffing, maybe not. No way I would modify the crossover. But I agree on the need for measurements, right now I’m flying blind.

I am currently running LMS on the opticalrendu itself but I do have a pi which I use to stream to my desktop speakers. So I can have a go at CamillaDSP, it will be a good experience anyway as I have never worked with DSPs.
 
I see where they coming from, I need to find a way to move them back by 20cm or so, then we should be good.
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I am not quite sure about the photo, but the speakers look like they are not rectangular. Are they? Is the photo distorted?
To make them look a bit less "big", I'd suggest using another speaker stand. Something that's a bit lighter on the eye. I like these.
You could also try to hide the xover boxes, for example behind the TV screen.
 
The photo is indeed distorted. The protective frames are bending slightly inward in the middle, that could also confuse the eye. If you hold a rule to the sides you see some imperfections in flatness, due to sanding and clamping during gluing, but I would not be able to tell from just looking at them.

The main issue, which cannot be fully appreciated from the photo, is that they project too far into the room.