need an opinion..... as is usual

[Madmike2]

Hi guys. i built a couple of speakers a week ago for a friend of mine who listens to nothing but choral and piano. I tried to build something with a 'live' cabinet baffle.

What i did was build the box out of 1 and 1/4 MDF and the front baffle out of 1/4 cedar. Baffle is a little wide. Tweeter is offset, not really relevant but....

I put a N205WR3308 peerless in there and the MDT30 tweeter from morel.

After a week of his playing them i decided to drop by his house for a listen today. They seemed pretty good with the Piano concerto we played but i found them to be sort of 'ringy' with the choral. Especially the boys choir.

It is an extremely simple crossover so i am inclined to think i would be better suited with another driver for the midrange.

Anyone have an opinion or idea or who might have built something similar for this purpose want to chime in at all?

Maybe i should rebuilt them and go 3 way?

 

[PeteMcK]

what xover freq are you using? perhaps try a 2nd order xover before anything else, seems that the Peerless has a bit of a peak at ~3KHz, the Morel can be crossed reasonably low
(unless of course the problem is in the recording...)
What do you mean by a 'live baffle'?

 

[Madmike2]

I mean it is not a dense low resonant frequency baffle which most would normally use. I put thinner real wood there like you would making an instrument.

It is a second order x-over now at 3700. I didnt know about that peak though in the peerless.

edit : to correct high frequency to low frequency.

 

[Inductor]

Sorry Pete,
Madmike2 try posting your xover. Your problem might be an absence of an RC damper on the woofer. Who knows?

 

[Madmike2]

Sure, the crossover is 2nd order and slightly different per side as the speakers all measured differently. One side is 10uf caps and 0.15 mh inductors (pretty close to 4 equal components, i measured.)

And the other side is 0.16 mh and 10 uf , again all components are measured.

 

[Inductor]

You mean same components for the woofer and tweeter(?!) Ok, now is that a parallel xover right. If series, I'm out of the game... Anything else?

 

[Tenson]

Umm... most unsurprisingly its probably the front baffle ringing!

Try making a new baffle from 1/2" or 3/4" ply or solid wood to your taste. Making a speaker is hardly like making an instrument, I'm not surprised it adds its own colouration.

Solid wood or ply is good, but you should still go for at least 1/2" and brace it if you can, or the resonant frequency will be in the critical vocal range.

 

[Madmike2]

Umm... most unsurprisingly its probably the front baffle ringing!

Try making a new baffle from 1/2" or 3/4" ply or solid wood to your taste. Making a speaker is hardly like making an instrument, I'm not surprised it adds its own colouration.

Solid wood or ply is good, but you should still go for at least 1/2" and brace it if you can, or the resonant frequency will be in the critical vocal range.

The intention was for the baffle to add to it. Like the old rogers speakers. The baffle is braced, and the cabinet is a 5 sided box.

I dont think the baffle sings though, not at that frequency. If it was a octave higher maybe. The piano does not make it do that, only sustained voices.

 

[Madmike2]

I think i will borrow the speakers back this week and try and take them to the lab and use real equipment to test out the baffle.

I have a suspicion that changing the mid wont fix it. Tenson might be right.

 

[Tenson]

Bracing the baffle may have raised the frequency.

Have you got a contact (tactile) mic to take CSD measurements of the baffle, excited by an MLS signal? That would help a lot in working out the problem.

You can make a cheap tactile mic from a piezoelectric speaker like in a b-day card.

Otherwise place a directional mic about 1mm from the baffle (not the driver) and transform to a waterfall plot. You should be able to see something in the decay.

 

[Inductor]

The intention was for the baffle to add to it. Like the old rogers speakers. The baffle is braced, and the cabinet is a 5 sided box.

The BBC's had that but not from the front baffle, from what I remember (white paper) was from the box itself. This baffle might be to weak. On the rogers/bbc the frequency emphasis is lower I guess 1 or 2K. I am leaning to the xover.

Check this my other post some days ago (peak at 3K):
http://www.diyaudio.com/forums/showthread.php?postid=1447881#post1447881

 

[Madmike2]

Ok. I will get them and take them to school and put them in the lab and measure them in chamber. Better yet i will get the physics kids to do it, they love problem solving, and they are afraid of me LOL.

 

[R-Carpenter]

what xover freq are you using? perhaps try a 2nd order xover before anything else, seems that the Peerless has a bit of a peak at ~3KHz, the Morel can be crossed reasonably low
(unless of course the problem is in the recording...)
What do you mean by a 'live baffle'?

I second that.
Crossing this woofer at 3700hz is quite a bit too high. I don’t have a complete T/S and measurements on it, but I would seriously consider crossing it much lower. It’s an 8-inch woofer?
Making a front baffle out of ¼” cedar is probably a bad idea also. God knows at what frequency it’s ringing.