Taming the ferals!

[prickears]

Hi all,

I guess it had to happen, after some months of listening, it's apparent, the ferals need taming. The main problem is, a bit of port noise and the xo to the mid (@ 600Hz) is less than ideal. At the moment, the design is:

Vifa (x1) p22 (4 Ohm, 8 Inch), 23 ltr box, port (Rectangular) 5x8x22 cm. 1st order b/w filter (1 mH)

Response 2 inch dome mid (6 Ohm), 2nd order b/w filter (L 2.2mH, C 33uf).

ATM, They are truely ugly (like a bulldog licking p**s off a stinging nettle!). See attached photo's!

So I'm thinking of a more eye (and ear!) pleasing design, wmtw seems to me, a more attractive alternative.

The design I seem to have the most trouble overlooking is a double 35 ltr BR (70ltr total), Woofers in series, (for 8 ohm), 2nd order b/w filter, again @ 600 Hz (L 3mH, C 22uf+1.5uf). 10x10cm square port per chamber.

I THINK these changes will cure the port noise, and hopefully, tighten the bass, and smooth out the WM XO.

My main concern is, What is the likely effect these changes will have on bass output from an SPL point of view?, as I would like to try to retain the O/A tonal balance.

If there is something I'm overlooking and need a heads up on, feel free.....

Thanx, Mick.

[R-Carpenter]

Do you have a mic to measure port and the drivers?
Holmi Impulse is a free and easy to use soft.

[J.R.Freeman]

Neat looking project!

Where did you find Vifa P22's? I've only ever seen P21's available here in North America on the regular DIY haunts, however there is a good chance I have missed them. Aren't the P22's used in the beautiful Mackie studio monitors?

Jim

[prickears]

Thanx guys,

Carpenter, I only have a radio-shack spl meter and test discs, I badly need to up date my pc and get decent sound cards and mic etc. before i can do more vigorous testing, a little way out of my financial grasp ATM.

I'm only guessing, but, I think I may lose a dB or two by going to a box that is effectively 50% larger. I don't think I will gain any dB by running 2 drivers in series as opposed to 1 driver, but i'm not entirely sure. I can't get Holmimpulse to work due to lack of sound card compatability.

J.R., Those are the mackie drivers, I purchased four of them through Jaycar, I since scored another 2 on ebay. They pop up every once in a while downunder. I first used them in a wtw set up a few years ago, running in parallel, they are a sure fire way to wake the dead!, but amps tend to get a bit hot under the collar with that configuration!
Trust me when I say this, seen in the flesh, this is NOT a nice looking project, They truely do look totally FERAL. In fact i reckon if we ran a comp for the most feral looking speakers this side of the black stump, these would win hands down! But, Thanx all the same.

Thanx again guys, Mick.

[Moondog55]

Not Feral? look tamed to me.
Have you tried listening to them turned up the other way with the dome mid on top? Then the tweeter? I have assumed the tweeter is in the box on top, I had a go a couple of times trying to integrate that Jaycar dome into three-way speakers and it never sounded any good to my ears, it is a good driver but needs a bit of work on the XO to get the integration right

[prickears]

G'day Moondog,

Just trust me on the feral in the flesh thing!

From top to bottom it goes, mid, tweet, woofer. The mid and tweet are in the raw box on the top of the painted one. The painted box houses the p22 and a d25ag3506, the d25 is only stopping air leaks!

I have turned the top box upside down, turns to mud, dunno, can't work out why it makes such a differance, also the tweeter is reverse polarity, again the other way it sounds like s**t. Then just to top it off, if I even think of changing a resistor value on either the tweeter or mid they sound like crap again. I'm starting to think I fluked it!

The tweeter is a SEAS 27tff and they are XOed @ 4400 hz 1st order BW (6uf .22mH). I couldn't get that mid to cross well with the d25, so your quite right, very difficult to intergrate. However, as far as the woofer to mid xo goes, I only used what I had lying around, so the values are only closeish, not ideal.

It has that sound that says 'I want to intergrate, but your just gunna have to try a little harder'. Challenge accepted!

Just out of curiousity, what were you using with it, if you don't mind my asking?

Cheers, Mick.

[chris661]

With series linked speakers, you get 0dB gain - you lose 3dB due to the inductance rise, but gain it back because of extra cone area. Parallel gives 6dB gain.

Might be an idea to put the tweeter in phase, then go to TMW, see how that goes.

Chris

[prickears]

Thanx Chris,

Thats about what I thought might be case with the series idea, What i'm not so sure of how ever is how the 50% bigger box will/will not, cut bass. In short, what is to be gained by series configuration other than an easier amp load? Does port output increase or stay the same?

I tried the tweeter in phase and flipped the other way, again, sounded like mud.
I can't, for the life of me, explain whats going on there, but, believe me, the difference is staggering! Even tried 'em leaning back and leaning forward!

Some kind of 'wtf' phase thing?

I'll bet there is someone out there laughing at me right now 'cause I can't nut it out

Mick.

[Moondog55]

Originally Posted by prickears

G'day Moondog,

Just trust me on the feral in the flesh thing! closeish, not ideal.

It has that sound that says 'I want to intergrate, but your just gunna have to try a little harder'. Challenge accepted!

Just out of curiousity, what were you using with it, if you don't mind my asking?

Cheers, Mick.

First off with the cheap Jaycar 8 inch polycone, somewhere around 600 Hz ( because that was the Jaycar recommended ) RS/ then with the Jaycar 6inch carbon fibre 4R not bad but I had to pad the dome right back and I really hate doing that and lastly with the Jaycar 6inch polycone at 1500 which was OK but after a while it grated So I sold them on Ebay; lost a packet too.

What I do have on my shelf waiting for a project is a pair of the 32mm ( inch &half ) Jaycar dome mid-range which should make a decent low crossing tweeter.
i'm gunna try that combo with the Jaycar 6inch polycone some day.
Problem with the 2inch dome is the FS, if it was an octave ( or even half an octave) lower I think it would be a breeze to work with, 350 is just too high to make it easy.

[prickears]

Funny you should say that Moondog, I bought these off ebay and they too were grating!
(by grated I assume you mean sound like the voice coil was grinding in the gap?) I pulled them apart and with a steady hand and some 100 mile an hour tape, pulled out a heap of metal shavings! put them back together and presto, better than new!

The bloke who owned them before me tried to pack the chamber with long fibre wool, wasn't you, was it?

I have them padded back 2.5 dB, 1.5ohm-18ohm with the SEAS @ 4dB 2.2ohm-10ohm.

The SEAS are still available on ebay for 49.95 ea, they are a cinch to xo @ 4400hz & have a beautifully flat response up to 25K.

I certainly agree those jaycars would be easier to cross with a lower fs. But i'll roll up me sleeves with this project and see how I go!

That other jaycar project sounds like a cheap but effective little setup, make a great PC setup I reckon.

Cheers, Mick.