Help: Beyma 12G40 vented options?

[oLjud]

Hi all,

I'm going to build a pair of speakers with Beyma 12G40 and I would need some help to figure out what internal volume to use.

My windows-copy just ran out from activate-dates so now i can´t longer use windows on my Macbook. therebe i need help testing some volumes...

The box can't be to big, max 70L, but a response down to 40Hz are a goal!

the 12G40 will be match up with the driver Beyma CD10Fe with the 194-horn.

Grateful for any suggestions!

Best regards
Mikael

 

[GM]

OK, then 70 L tuned to 40 Hz/~77 Hz F3 it is since it really wants a smaller cab tuned higher if the published specs are reasonably accurate and a very low total output impedance is used. Power is Xmax limited to 200 W, so based on this, (2) 10.2 cm diameter vents 36 cm long gets it close to 5% mach, but you can always damp them a bit if they are noisy.

GM

 

[oLjud]

I know it wants to tuned higher up, but I planed to used them for rock/metal-music and I read that a lot of the drums and bass are inbetween 40-50Hz. Maybe I can go for 45Hz "tune" instead.

The cabinet I sketch now have the internal volume of 55-60L, what recommended bassreflex whould you recommend for that size??

Maybe there's some other box-designs that are better then Bass reflex for 12g40?

 

[David_Web]

You could do something like this.
Tapered Quarter Wave Tube

Ether use the port forward or put it on adjustable feet so you can tune it.

Requires a bit of brainpower in hornresp or MJKs worksheet to get right.

A TL could be used as well. You have the option to tweak the port contribution to give a flatter response instead of a "hump" at tuning.

You run out of space quickly though.

MLTL is also an option, close to BR but according to some sounds better.

The problem with BR in this case is that you get a small port or way too long. And little control over the "hump"

 

[oLjud]

TQWT seems like an option, seen an option for the 12G40 on the swedish forum "hififorum" by Ingvar.

Since I doesn't have windows I can simulate anything, maybe I can borrow a PC someday and run some simulations then.

I've built a pair of TL earlier and I like the sound from them, atleast the bass-area.

So you guys doesn't really suggest to go BR with 12G40?

 

[David_Web]

I was actually thinking about that exact speaker. QW-1 by HAD.
Ingvar Ahlberg knows what hes doing so it can't be a bad alternative.

Make a thread there as well.

 

[kenpeter]

70L=2.5Ft^3. 40 is optimistic... You will probably hit hard down to 80 and
then drop -10db even if cabinet tuning extends a shelf to 40 before falling
like a dead air-conditioner pushed off the roof.

If you are willing bigger box, I think that would work well in a Karlson K15.
Plans 1955 Radio Electronics... I've used with Eminence DeltaPro12, and
I do play bass guitar... Also nothing on Earth reproduces kick drum better.

 

[oLjud]

I'll simulate later this week in Hornresp. on BR, TQWT and TL...

No one used 12G40 for any speakers?

I'm very thankful for every comment!

 

[oLjud]

I'll go for the QW-1 with Beyma 12P80Nd.

Now I just have to figure out how to design the crossover..

 

[GM]

Maybe there's some other box-designs that are better then Bass reflex for 12g40?

Higher tuning just means the driver will go non-linear quicker if there's no high pass filter to protect it.

Less net cab volume (Vb) just means less bass and a larger/longer vent for a given tuning.

Yes, a ML-horn (aka ML-TQWT), but can't do anything worthwhile in 70L much less 55-60 L.

GM

 

[GM]

70L=2.5Ft^3. 40 is optimistic... You will probably hit hard down to 80 and
then drop -10db..........

If you are willing bigger box, I think that would work well in a Karlson K15.

Not if the published specs are reasonably accurate, see post #2.

Your performance prediction of the BR sounds more accurate for the K15 and while I agree that it's a good choice for the intended music genres, the high XO point to the HF horn means lots of highly resonant mids and many folks don't like that much 'color' through this BW or it wouldn't have been audio's premier outcast for >50 yrs now, so could potentially be a lot of tedious woodworking to make firewood.

WRT the 70 L/40 Hz tuning, trading some efficiency for LF gain BW will flatten it to 40 Hz in-room, but going with a larger MLTL or TQWT makes more sense to me if enough height can be tolerated.

GM

 

[GM]

I'll go for the QW-1 with Beyma 12P80Nd.

Plans?

0.15 Qts?! Is this for real?

GM

 

[Scottmoose]

Knowing Beyma, there's a chance it could be. Just opened the pdf -if you look really closely, you can see where they've crammed in the 426 Hemi.

 

[oLjud]

Here's the plans: http://www.seaside.se/~manoviia/QW-1draw.pdf

And I found them in this thread on hififorum.nu: HiFiForum.nu - Två Halmstadflyttar och en björn i Nissan

According to the builder of the org.speaker it sound very great with 12P80Nd along with cd10fe+td194.

what do u guys think about it?

 

[GM]

I assume you mean the magnet material: 12P80Nd

Apparently I've missed something in my driver design studies though. VC length Vs gap height implies a 4 mm Xmax, so how do they get 7.5 mm?

GM

 

[GM]

Here's the plans:

Thanks! Don't have time ATM to figure out the design's acoustic dimensions, i.e. path-length, etc., so please post the HornResp or similar simming details. Otherwise it could be awhile if no one else does it. IME though, low Qts drivers typically need a lot of series resistance to perform well down to Fs if not in a half WL pipe horn.

GM

 

[Scottmoose]

Looking over the pdf, down in the bottom right, it looks like they've taken Xmax as (Lvc-Hag)/2 +(Hag/3.5)

 

[GM]

Right, I meant how can we reuse Hag? They're adding the equivalent of a pipe end correction in its magnetic stroke. If we can, then is the 3.5 constant valid for any traditional motor design?

Frankly, seems like ** to me since at least with the Altec, JBL, RS, etc. drivers that I have good specs for are already audibly compressing at the (Lvc-Hag)/2 value if tuned to Fs.

GM

 

[GM]

Interesting! New and more restrictive censorship.

GM

 

[Scottmoose]

Hmm. I see what you mean... I can't even describe my new avatar (HMS Hannibal) as a British Steamship.

Agreed, you won't hear me arguing about their Xmax calculation being dodgy at best. Probably trying to make it look good to the pro market.