[floobydust]

 All,

 New thread for enclosure types for the D-5nf. The ones I know of are:

 1- Feastrex own enclosures - but I have no real data on these.

 2- Scott's BVR enclosure (that Rich is using) - aka Freddie Chang

 3- Scott's new double BVR - aka Phat Freddie

 4- Ron's Carolina Audio TL

 5- The new Maiko design being worked on.

 Does anyone else know of additional designs? I'm working on a TL floor-standing design but that won't see a prototype until 2008.

 Regards, KM

[richidoo]

These examples are not single driver designs, but interesting nonetheless.

Using Feastrex' upgrade model D5 driver, and making its public debut at China audio show starting this weekend: Sonic Purity RS-5a

Also: Dick Osher's OB2 with D5nf driver and Augie woofer.

TL sounds cool KM.

[floobydust]

 Yes, good point... did not mention those. It would appear that the initial Scottmoose BVR is the base design most seem to build... first you, then Phil (IIRC) and now myself included. I think Phil made his in Birch.

 Also, Joe Cohen has a pair with the D9 passive radiator, so I guess that's another.

 Regards, KM

[richidoo]

It would appear that the initial Scottmoose BVR is the base design most seem to build... first you, then Phil (IIRC) and now myself included. I think Phil made his in Birch.

KM, is your Freddie made of birch ply also?

The factory Feastrex D5 cabinet is 2 layers of plywood, assembled very, very nicely. Built by a perfectionist. Sounds good too. I think the BVR might have a leg on it though. It would be interesting to hear a box optimized for the PR.

[floobydust]

 Mine are being cut from 3/4-inch solid red oak. I decided to use something pretty hard and will include the rear bracing as well. I am thinking about filling the lower section with sand or lead for additional damping. I plan on using them till next year when I'll hopefully have a TL to start testing in.

 Regards, KM

[richidoo]

  Thanks right, sorry I forgot. You will like them!

[jrebman]

Guys, also consider using BBs for ballast.  There's a thread over on the Horn Shoppe circle where Ed talks about doing this with his personal speakers, and liked the results.

Just a suggestion.

I'm staying tuned to all this stuff since I'll now be helping with a build, and able to listen to the final product, or products.

I'm also going to be working with Mike to try to get him setup with a decent SE amp.

Exciting stuff.

-- Jim

[floobydust]

 Hi Jim,

 I tend to use lead-shot... the Quads have been in Arcici steel stands forever and they are loaded with shot... really heavy and very dead. The TL design I'm working on has some areas where I can use some lead shot to dampen things a bit. It also adds some good weight for stability too.

 So, what is the definition of a "decent SE amp"? Is he looking to build or buy?

 Regards, KM

[jrebman]

I'm going to help him build something -- probably a tubelab SimpleSE, he needs something a 1970s vintage Denon receiver, and he needs it to be fairly cheap to build.  I'll probably be building one of these for myself as well, but will put some quality iron in it, which brings the price up quite a bit..

I also have a Vista Audio SE PCL 82 amp here that we can probably refit with a new transformer to better match the 16 ohm impedance of the D5nf drivers.  Right now the OPTs are single secondary 6 ohm.

-- Jim

[floobydust]

 Tell you what.... I'll start another thread... you can actually build a decent DHT amp without breaking the piggy.... Working on one of these with my Son as time permits. Nothing like a 45 triode and 2-watts.

 Regards, KM

[richidoo]

Now that sounds fun.

[jrebman]

That would be great.  I'd still like to build an SE KT-88 amp -- just because, and already have one of the Simple SE PCBs.  You can never have enough cool amps .

-- Jim

[Scottmoose]

Just to clear up any confusion, the double BVR for the D5nf and Maiko are one & the same & should be a big advance over the existing box. The latter was really only supposed to be a quick example rather than a hyper refined design (not that it does badly by all accounts & I wouldn't have suggested it if I wasn't sure it'd work well). This unit appears to like the BVR type of load, from a technical POV.

[JLM]

What's a BVR enclosure?

[Scottmoose]

BVR = Big Vent Reflex.

There is an argument (and a valid one IMO) that most BLHs can be regarded as small BR cabinets with huge vents (which provide the LF gain the chamber Vb is too small to allow itself). The term BVR typically applies to a more 'normally' sized reflex cabinet, which uses a short, rapidly flared horn / waveguide as the vent, rather than the more usual slot or cylinder. To be honest, if you subscribe to the aforementioned idea that all chambered BLHs are in fact no more than reflex cabinets with unusually large vents, then it's a bit of a misnomer, but there it is. Heavily simplified of course, and doesn't account for the different proprities a 'regular' type of BLH and a BVR usually have, but you get the general idea.

[jrebman]

Scott,

Thanks, and welcome to the AC SD circle.  Glad to have you here and willing to share your experience and expertise.

-- Jim

[Scottmoose]

Cheers Jim. Nice to see such an interesting circle developing.

[JLM]

So to me (a layman) it appears that BVR are a BLH adaptation for higher Qts drivers.

Can BVR be fully modeled into Martin King's MathCad application?  If so, what does it "say" when comparing BVR versus BR, TL, etc.?

(I own and love my MLTL that were based on Martin's work.)

[Scottmoose]

To an extent, though you can just as easily use a low Q driver with added series resistance or an amp with adjustable output impedance, just as was done in the 1950s - '60s too. In fact, some would argue the latter is preferable, as you still retain most of the advantages of the big motor despite the addition of resistance into the system. YMMV. Conversely, a mid - high Q driver can be used in a long-path horn, contrary to popular myth. However, you can end up with a tail wagging the dog situation, as their relative lack of motor power means they can't drive it as effectively, and they're more likely to suffer from HF drop-off because of this. Fine if it's being supported by a tweeter of course. Generally, I subscribe to the 'more powerful the motor, the better' take, as you can always loose what you don't need. Simplistic, and I regularly contradict myself, but it's a useful general guide to have.

You can easily model this sort of box in MathCad. As for what you can expect, depends who designs it and their objects, like anything else really. FWIW, the cabinets I do will give a modelled FR similar to what you'd get from a regular small-vent box, albeit typically with somewhat reduced excursion and a slightly wider cabinet passband. Sonically, they tend to give the relative smoothness of a regular BR or ML-QW box, with the directionality and scale of a horn. Martin heard a pair of Half Chang cabinets I designed, with 206s I believe, and he seems to like them: http://www.diyaudio.com/forums/showthread.php?postid=1336199#post1336199 They have different priorties to the more usual BLHs of course, which work over a wider passband (they have to), offer more gain, and theoretically reduced excursion at high SPLs (in practice, there often isn't much in the latter), at the price of a more uneven response. There's room for everything & it depends on your design objectives really.

Best
Scott