Bass reflex standmounts 10.3 / 10P

[Scottmoose]

I did these some time ago, but they were buried in a couple of large threads; seemed sensible to put them into a dedicated place where they're more easily accessible. Two modest sized standmounts for the Alpair 10.3 & Alpair 10P. Volume & cabinet dimensions are identical for both, as is damping. Only change is to vent length to alter tuning as appropriate for each unit. Quite straightforward, nothing fancy. Lightly damped alignment so they're a better match to room gain and / or high output impedance amplification. If you want to add bracing, do whatever floats your boat (don't ask, I'll simply repeat this sentence). Damping should be acoustic fiberglass, ultratouch, natural fibre carpet underlay of xyz type, Monacor MDM-2 or MDM-3 or similar lining all internal walls; I'd suggest avoiding foam however (ditto).

Please note: these designs are my property and supplied for DIY use only. Any other purpose, please contact me.

http://wodendesign.com/downloads/simpleReflex-103-10p-plan-100214.pdf

 

[McDark]

Thank you very much Scott, very interesting, gotta try these. Just wondering, why MDF is suggested instead of usual BB? 19mm ok?

 

[cogitech]

Thank you very much Scott, very interesting, gotta try these. Just wondering, why MDF is suggested instead of usual BB? 19mm ok?

I think this is a case of "lost in translation."

The sentences are:

"Bracing not shown; may be used if desired. Recommended if MDF is used."

(emphasis is mine)

This should be interpreted as:

"Bracing is not shown, but may be used if desired. Bracing is recommended if MDF is used."

(Because MDF is an inferior material and will benefit greatly from bracing.)

Scott, please correct me if I am wrong.

 

[Scottmoose]

Spot on.

If MDF is used, then panel bracing will be necessary. If a quality ply or similar is used, you might get away without it. Although it wouldn't hurt if you did add some anyway. Note on the 10.3 drawing, incorrect Fb & F3 frequencies are stated -they should read Fb = 40Hz, F3 = 44Hz. I forgot to alter them from the 10P drawing (such as it is). The dimensions etc. listed are all correct however.

 

[McDark]

Thank you guys I've missed it probably because BB recommendation is common for other designs, guess it's just became assumed at some point.

Also noticed freq stuff, thanks for correction.

Btw did I missed, is there same charts for 10.3 and 10p pencils somewhere?

 

[Octavia]

Scott, thanks for putting this thread on with the charts. It's nice to see all the data together in one post. As I said before just brilliant to have the same enclosure with a simple port change for either 10p or 10.3. Do you happen to have a preference for dampening material and thickness?

 

[Scottmoose]

No problem, glad you like them.

Not especially; the examples given are all decent enough. 1/2in - 1in thick should be fine; just leave the driver some breathing room and should be good to go.

 

[budcar]

Hi guys, I know I'm displaying my ignorance and I don't want to ruffle anyone's feathers, but I have a nice new pair of 10.2's that I was lucky enough to purloin during the run-out.

I've been delaying doing anything with them because I would really like to do bookshelfs, for various reasons.

Would either of these incarnations suit the 10.2's?

Cheers

 

[planet10]

With suitable adjustment of the length of the vent (would need tobe longer)

dave

 

[budcar]

Thanks Dave..

Perhaps an additional 1/2 as much again the difference between the 10p and 10.3 as a guesstimate? (say 180mm or so??).

 

[planet10]

Let's wait till Scott weighs in, it is his design.

dave

 

[budcar]

No worries... I understand.... thanks.

 

[Scottmoose]

Yes, you can, but with the 10.2 it's approaching a QB3 alignment which is rarely practical. I'd aim for an Fb of 36Hz; assuming a 50mm diameter vent that's going to be 250mm long, which is a bit OTT for my taste. An alternative may be to line the vent with damping, i.e. roll up some felt damping material and insert, like this, courtesy of Troels Gravesen's site:

 

[Octavia]

sometimes stuffing a vent with drinking straws works pretty well too

 

[Octavia]

Scott in a previous thread you showed the port on the rear, so a question about the port placement, given proper clearance how would you describe the sound differences in placing the port front, rear, or perhaps even out the bottom with suitable feet to raise the speaker up and give bottom clearance?

 

[budcar]

Thanks Dave, Scott,Octavia... OK, just did a crash google course of QB3 (how did we do this pre-internet???). So wandering into a QB3 alignment can produce boominess and an under-damped sound in the search for an 'artificial' level of bass... correct?

No, not my taste either.

So I assume the damping in the tube is to reduce that boominess and give more damping?

That's what I'll do then, start off with the longer port (180 I think) and play around with lining it, given that that's an easy retro-adjustment.

(or, just as a red herring, I was also looking at the Erich Hartmenn box for the 10.2.. if anyone has an definite opinion here I'd love to hear it, otherwise I'll start building... smile)

Thanks everyone.

 

[Octavia]

One more thought on port placement, does it effect group delay?

 

[11opas]

Scott or Dave,

I'm going to build a simple BR speaker for my Dad. My question is, should I go with the Alpair 7.3 or Alpair 10P? LF should be similar for both, around 50hz for fb. Obviously both drivers are proven and sound great, but do you guys prefer one over the other in a BR enclosure?

My Dad mainly listens to easy listening, choral and classical music...

Thanks

 

[planet10]

A10p vrs A7.3 is a very personal question. They are 6 of one, a half-dozen of another. The question comes down to what set of compromises is most appropriate.

What source? What amp? how big the room? How loud?

dave

 

[planet10]

BTW: another box toadd to the list, i finally got the CGRs done.

http://p10hifi.net/FAL/downloads/CGR-MarKen103p-plan-040414.pdf

dave