Woofer Enclosure Help

[rplace]

I want to build a custom box to house a woofer (not subwoofer) to function for the low end of my 2-way center channel in my HT system. It will be an active set up so no crossover needed. I have an existing 10-inch driver I'd like to use. I have a full range, 8-inch driver this will be mated to so it only needs to handle says 500Hz and below.

 

In searching around a bit I gather there are various parameters you need to know from the driver to help build the correct dimensions of the box. All I know about the existing driver is that it is an Vifa 10" driver. It is currently in an Oken enclosure. I can open it up to get the model number. What other specs do I need to get you all to help me figure out the box's specifics?

 

Up to this point I've only ever built Open Baffle speakers. For this particular project simpler is better than complex, I think that means a sealed box...but open to the idea of being ported/vented if that is not too difficult. If ported the port has to be in the front as I plan to "sink" this back into my front wall below the screen as much as possible.

 

My one constraint is that the box will need to be very shallow, height and width is not an issue.

 

How to proceed?

[PrestonTom]

By all means get the driver ID and T/S data. Google is your friend.

 

First look at the Qts value and that will give you a rough idea whether the woofer is best for a closed, ported, or open design. If the design is a closed box, you can be a bit sloppy about the box geometry. However, if you are going for a ported cabinet (and it will extend lower in bandwidth, but with a possible compromise on some time domain behavior), the box geometry and porting will require a more careful design (based on the woofer specs). There will be other specs also, Qts, VAS, Fs are some of the more critical parameters. 

 

The program I like to use is WINSID, it is freely available and there will be a ton of help on how to use it. 

 

Please remember that his is a design issue and is calculated and  not "designed" because someone on the internet said it "sound good"

 

Good Luck,

-Tom

[ClaudeJ1]

9 minutes ago, PrestonTom said:

By all means get the driver ID and T/S data. Google is your friend.

 

First look at the Ts value and that will give you a rough idea whether the woofer is best for a closed, ported, or open design. If the design is a closed box, you can be a bit sloppy about the box geometry. However, if you are going for a ported cabinet (and it will extend lower in bandwidth, but with a possible compromise on some time domain behavior), the box geometry and porting will require a more careful design (based on the woofer specs). There will be other specs also, Ts, VAS, Fs are some of the more critical parameters. 

 

The program I like to use is WINSID, it is freely available and there will be a ton of help on how to use it. 

 

Please remember that his is a design issue and is calculated and  not "designed" because someone on the internet said it "sound good"

 

Good Luck,

-Tom

I'm compelled to say, EXCELLENT, ACCURATE, response.

[rplace]

I've been trying to get the specs. No actual PDF or anything, but seems like I'm close based on multiple foreign sites.

 

 

Here are some links:

http://site.diy-loudspeakers.com/32-loudspeaker-datasheets/vifa-datasheets/64-vifa-drivers

 

http://www2.audiokit.it/ITAENG/Altoparlanti/VIFA/Vifa.htm

 

And I found this on another site. Not sure it is accurate, but no reason to think it is false:

Currently using a Vifa M25WP-09-08 10" woofer, Fs = 28Hz, Qts = 0.29, Sensitivity 92dB/W.

 

 

This from a translated German site: 

I had it in 40 L CB, it sounded very crisp, not equalized, the f3 is then around 50 Hz (half space). I can send a Simu. Then, of course, if you actively equalize, you will reach further down, of course. In larger BR boxes (60L), Onken-BR or TML you reach very far down, 30 Hz are no problem.

TS parameters and data are:
Z 8
RE 6.8
LE 1.3
Qes 0.34
BL 10.4
Fs 29
Freq 28-2000
Qms 2
Rms 2.81
Mms 36
Cms 1.01
Vas 145
Xmax 6.5
Sd 337
Vd 438
Qts 0.29
dB 91
 

UK for sale site:

Specification

Drive units: Vifa M25WP-09-08 10" woofer

Resonance frequency Fs = 28Hz

Total Q factor Qts = 0.29

Sensitivity = 91dB/W

Frequency response = 28-2KHz

Max Power = 120W

Nominal impedance = 8 ohms

Dimensions: 72cm (H) x 36cm (W) x 51cm (D)

 

another non-english site:

 

M25WP-09-08低音,10", paper,鎂合金框,新長衝程28　　　
28 - 2k0.29812091

MODEL

說明

Fs Hz　 Freq Resp.

Qts

Gap Height mm

Power Walt 功率

SPL Sen. 1W/2.83V

 

M25WP-09-08

低音,10", paper,鎂合金框,新長衝程

28　　　 28 - 2k

0.29

8

120

91

[PrestonTom]

This is progress.

 

The Qts indicates that an open baffle design is not a good idea. If you port it, choose a vent tuning that is a bit below the Fs (probably not less than 75-80% of the Fs). When you do the simulations, there will be a graph of the excursion. Your Xmax is only 6.5 mm, be careful not to run it too hard (or tune the vent too low), 

 

BTW, this is not a very efficient driver, keep that in mind before you dig yourself in too deep. 

 

Good luck,

-Tom

[rplace]

6 minutes ago, PrestonTom said:

BTW, this is not a very efficient driver, keep that in mind before you dig yourself in too deep.

 

This + the fact I'd rather build a sealed box (easier for me I think) makes me think perhaps I should explore a different driver...but I actually have two if that helps in efficiency department.

 

Can we back into "best" driver if we start at a 10" depth, height/width unlimited within reason? And since it's a center channel does not need to go way deep.

[rplace]

Should add amp/power is not a problem. Carver TFM-25

[PrestonTom]

The driver you spec'ed is 120 watt max.

However, there are plenty of woofers out there. Some are even affordable.

 

[rplace]

1 hour ago, PrestonTom said:

The driver you spec'ed is 120 watt max

 

Only because I have 2 sitting around doing nothing. I'm cool with a different driver but figured it is really not a make or break piece of gear. The 8 inch full range driver will be doing the Lions share if the work.

 

Still sealed appeals to me more than reusing an unused piece. I'd go open baffle if my desire was to not recess it into the front wall. Folded horn too complex for a few movies a month. No interest in multi channel music.

 

So let's go driver shopping. What do I look for? Besides qts or whatever it's called under .45. Needs to be a simple project. Sick if looking at a huge box laying on its side.

[PrestonTom]

Try some shopping over at Parts Express. They have recommendations that have been built using drivers at various price points.

[JohnA]

Should be an easy design, with all the T-S parameters.  But, it is an engineering design  The size of the box may not be to your liking if you don't have a suitable woofer.  You need a woofer to go down to 40 Hz, f3, to cover the typical music range.  I like BassBox Pro.  I've found it easy to use and its operation encourages comparisons.