Designing mid-high speakers to match SUB

**Spadez** · **10-20-09, 11:05 AM**

Wow. Thank you so much for all the good information! I will make a cylinder then since you said it gives better results. Is 1.28L the optimum inside volume based on your findings then?

**Yad** · **10-20-09, 11:11 AM**

notice, cylinder is worth than cubic (((( sphere is the best! (use 2 half-square IKEA's dishes )) ) or you can make cubic with rounded facets (R10-R20 routed) and use soft carpet/wool to finish design of the box.

1.1 -1,28 of net. liters range is OK. Closed box.

smaller volume wil make "boom's - colouration" in sound )

**Spadez** · **10-20-09, 11:15 AM**

Im not sure I can make a sphere without buying dishes from Ikea!

If I go for rounded cubic, do I need to make the internal space rounded as well as the external facets for it to sound better?

Also when you say R10-20 routed, are you saying use a radius of 10-20mm?

**Yad** · **10-20-09, 11:22 AM**

no. just external. internal shape is not so critical and does not cause difractoin. Anyway, you will use wool-fibered damping inside.
Don't worry. )

yes, i mean Radius in mm. Bigger one - is more effective

**Spadez** · **10-20-09, 11:33 AM**

Can you tell me one final thing. If I keep with the cube with rounded corners of 20mm, what effect does lowering the internal volume from 120 to say, 80 have? Is it a big difference or a very small change?

**Yad** · **10-20-09, 11:39 AM**

oh, i forget to specify, that you should rout front panel (which carries a driver) at first. sides may be routed or may be not.

**Yad** · **10-20-09, 11:50 AM**

Quote:

Spadez wrote:

Can you tell me one final thing. If I keep with the cube with rounded corners of 20mm, what effect does lowering the internal volume from 120 to say, 80 have? Is it a big difference or a very small change?

you have to keep net inside volume (without driver's magnet volume) not less than 1.1 liter. a material for your box is 12-14 mm for sides and 18-20 for front. driver is better to make flush mounted. Inside part of the hole is better to rout 10x10 (45 degree router bit)

PS your dimensions may change a little (130x130 x ....) or like this

**Spadez** · **10-20-09, 11:55 AM**

On the website it says it can be 0.75, is that bewcause it is stuffed, or will 0.75L just give very bad results?

Im a bit concerned, because now this speaker box is getting big again, maybe too big to be on my desk.

EDIT: Ive done a little mock up of the speaker size, and while its size is still bigger than I had hoped, if 1.1L will give me the best results then I will go for that.

EDIT2: Will this size box allow me to go down to around 90Hz?

**Yad** · **10-20-09, 12:07 PM**

well, less volume will give you approx 150 Hz at lo end ; bigger-lower. And you may notice some rising of mid-bass frequencies. it s better to try 2 boxes.

**Yad** · **10-20-09, 12:09 PM**

Quote:

Im a bit concerned, because now this speaker box is getting big again, maybe too big to be on my desk.

ok. try to do less.

**Yad** · **10-20-09, 12:15 PM**

it will give you about 100 hz LF-end

PS R10 routing will be ok.

**Spadez** · **10-20-09, 12:23 PM**

1.1L internal will give me 100 hz LF-end?

If so, that sounds pretty ideal. Im going to do with this.

**Spadez** · **10-21-09, 09:03 AM**

A quick bump. How come people can design mids like this:

http://i32.photobucket.com/albums/d4...DSCF0156-a.jpg

At the top, the speaker isnt even in an enclosure. What type of speaker is this and why wouldnt it work for my application?

EDIT: Dipole or open baffle it seems. When I was suggesting tiny mid speakers, how comes nobody suggested these to me? I could make these tiny

**Yad** · **10-21-09, 12:20 PM**

This is open baffle. You may also call it "dipole", because driver radiates in to both sides with 180 degrees of phase difference (between front & rear sides). That's why it is also a problem. Lowest frequencies are canceling out. The lowest freq. that you can reach - is nearly F=340/d (F-freq. 340 (meters per second) - sound speed in air, d - is a 1/4** of the distance (in meters) between the middle of driver & edge of the baffle). So, for your 100 Hz at -6 db point you will need approx 3.4 x3.4 meters baffle.

Furthermore, your driver in the open enclosure will not work properly at the lo end ('cause of it's Thiele-Small parameters)

** sorry, i wrote 1/2 at first. if you will use the "1/2" coefficient, you should mean the width of your baffle.

**Spadez** · **10-21-09, 12:33 PM**

Hi Yad,

Thank you for your reply. I just dont understand this, because you obviously know the maths behind this, but so many people seem to be building these small OB systems and they claim that their responces and frequencies are very good.

http://www.hometone.org/entry/jamo-s...ffle-speakers/

This one above doesnt have anywhere need 3.5m baffling and yet its specs are very good. Is there a way to get it working well, or these people lying about the performance of their speakers?

**Yad** · **10-21-09, 12:49 PM**

Jamo R909 & other speakers have a specific LF drivers with very big square + very high sensitivity of them. Those speakers have very complicated networks. This is necessary to correct lo-end frequency response. And they also very demanding for listening room and your position.

For small drivers 1 or 2 with 8-10 inch diameter it' impossible to realize it without deep electronic correction and loosing of the resulted SPL. For smaller drivers - this is impossible even with electronics. ... or you will loose more than 20 db (may be much more) of SPL while flattering the frequency response ((

note, i gave you a true mathematics formula

**Yad** · **10-21-09, 01:36 PM**

I made a calculation for you.
the - picture - is the 3D math. model of enclosure 1x1 meters sides.
graphs are:
green - SPL at 1-2 mm distance from the driver
brown - resulted SPL at 1 meter or more
black - is not interesting in this discussion

don't worry about highs freq. the idea was just to show you LF. And I took not wide range 3" vifa driver (anyway, it does not matters in this example)

**Yad** · **10-21-09, 03:08 PM**

Quote:

Spadez wrote:

... or these people lying about the performance of their speakers?

It's not an a lie exactly. But they don't tell you some truthful details. It calls "the Marketing Tricks".

**Spadez** · **10-21-09, 03:09 PM**

Yad, I hold my hands up to you, you clearly know a lot about speakers and you have given me loads of useful information, im not going to fight you on it anymore! If you feel that the best way to get good mid range performance in this size is to go for a 1.1L sealed container then I will do this.

I had a phone call with the people at madisound and the mentioned this driver is good for small space, is it worth looking at:

SB Acoustics SB12NRXS25-4

**Yad** · **10-21-09, 03:20 PM**

Dear Spades, I did not fight with you ))) I'm just trying to help you.

**Yad** · **10-21-09, 03:23 PM**

about the least driver. It seems to me, that it needs 2 way construction with volume that bigger, than 1 liter. Do you really need it ?

**Spadez** · **10-21-09, 03:31 PM**

Hi Yad, its a figure of speech, I was only joking about fighting

I was recommended that driver, so I thought I would mention it. If the one you suggested is better, I will use your suggesion.

**Yad** · **10-21-09, 03:36 PM**

i know. my english is not so bad

**Yad** · **10-21-09, 03:43 PM**

This driver is pretty good, but look above

**Yad** · **10-21-09, 04:42 PM**

Quote:

Spadez wrote:

A quick bump. How come people can design mids like this:

http://i32.photobucket.com/albums/d4...DSCF0156-a.jpg

At the top, the speaker isnt even in an enclosure. What type of speaker is this and why wouldnt it work for my application?

EDIT: Dipole or open baffle it seems. When I was suggesting tiny mid speakers, how comes nobody suggested these to me? I could make these tiny

Looks very interesting. I think, the LF-MF x-over point is about 300 -600 Hz. One interesting thing: OB application of midway driver allows you * to use lower order (6 db per oktave) cut off electrical filters. It is very good for impulse response and "group delay" factor.

* because you will almost have an acoustical hi-pass filter.

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