Newbie DINAS questions – polarity, damping, PSUs

[dewd]

Hello, everyone! I’m in the process of building the Lepai powered / active DINAS and I am looking for a couple of clarifications from the build plans which I couldn’t find in the forums

* the plans indicate the tweeter & woofer are wired with reversed polarity. possibly for phasing? is that the correct wiring?

* there isn’t any mention of internal damping, either for the full range driver (sealed internal enclosure) or the woofer. Has anyone tried damping materials and are they beneficial?

* there are 3-4 reports in the forums of audible hum (60hz) which are traced to either bad or mis-matched switching PSUs. Is this common and should I consider running both speakers from a single PSU (with a pigtail to split the feed to each speaker)

FWIW, I’m leaning towards having the plate amp on an external mount (separate enclosure on the rear) so that if I change my mind and go with the passive setup in the future I don’t have to fill in a big hole where the amp was mounted.

Thanks in advance for any help!

[123toid]

First of all welcome to the forum and congratulations on the build! That is a fun build, you will love them. Let me see if I can help a little.

1. The wiring diagram in the plans is correct and yes it is due to phasing.

2. I don’t use any internal damping, however others have and have had mixed feelings on how beneficial it is. I would say feel free to add it if you want. It is not going to hurt anything by adding it.

3. There have been some people who got bad power supplies. Typically they ended up returning them and getting a different one that didn’t have the ground loop issue. Unfortunately, it is impossible to say what will and will not have it without trying it. The way Amazon lists a product is under a generic name with multiple manufacturers making the “same” power supply. So when it goes out of stock, they restock it with a new supplier, who may or may not have properly grounded it. It is a pain, but I don’t know of any other solutions. You can try to pigtail it if you want, but you would loose out on power.

4. You didn’t ask, but I’ll throw this is there as well. If you feel you aren’t getting enough bass, you can bridger the RCA’s on the back of the plate amplifier. By doing this you will double your bass output.

I think that is a great idea of mounting the plate amps like you said.

[dewd]

Thanks for the guidance – very helpful! I’m really enjoying your content and already thinking about the “next project” (probably a DAC or amplifier).

While I hadn’t really expect #4 (not enough bass), I had thought about bridging the RCAs and deferred that as an easy later change.

My deployment plan was, based on the Lepai supporting RCA stereo in and out was going to be:

[source – stereo] –> RCA pair –> [speaker A] –> RCA pair –> [Speaker B]

…solely for the convenience of only having to connect the source to a single speaker and wanting to experiment with a few different sources.

Bridging the RCAs would combine L & R channels into mono (I think) so I’d then change it to the more “normal”

[source – R] –> RCA R –> [Speaker A]

[source – L] –> RCA L –> [Speaker B]

…and probably insert a switching source / preamp to manage multiple sources.

Parts should arrive today so looking forward to getting everything hooked up in the next few days!

[dewd]

Quick update…build completed (99%, still waiting on one set of magnets to hold on one of the grilles)

Impressions:

* I’m reminded how much I prefer working with real wood vs MDF, especially for finishing. I kept it simple as a first speaker build…just painted & lacquered MDF…but would veneer or use hardwood exterior next time. Painting, sanding & matte lacquer finish took well over half the build time.

* The DINAS were pretty simple to build from plans that are really clear and easy to follow. Definite 👍 for the documentation!

* The two real deviations I made were a) I used 3/4″ MDF for the exterior, instead of the 1/2″ MDF (which I used for the port), with a corresponding adjustment to the interior port length to keep it consistent with the tuning in the plan, and b) I added grilles made from $20 aluminium screen door frames I purchased at a big box store + speaker cloth from a fabric shop.

* a suggestion I’d make for those people who are thinking about building these, is to extend the leads from the tweeter before installing them. This will allow you more flexibility in how you connect them to the plate amplifier, and minimize the size of any holes needed to route the leads.

* Sound quality is good, quite full and enjoyable — and I do not need a subwoofer with these 😀. Called DINAS for a reason. I find the higher frequencies a little bright to my taste and the tweeter, especially, to be quite directional. Not sure how much of the brightness is the plate amp vs the drivers. Definitely *much* better than the $100 desktop speakers these replace!

* I purchased two Nobsound 19v 4.7a power supplies and my initial impression is positive. None of the feedback hum other builders have reported with other switched power supplies, and they are dead-quiet when there is no input signal. The output volumes are sufficient to the space I have, without bridging the two channels, so I will forego that.

Anyway, just wanted to give props to 123Toid and JoeNTell for the design and I’m looking forward to enjoying these, at least until I decide to do something more ambitious!

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