Just if it so happens that you would need it...look fore "frequency response leveller"...seems like a nice tool
http://www.lautsprechershop.de/english/index_tools.htm
http://www.lautsprechershop.de/english/index_tools.htm
I bought some 18mm MDF a couple of days ago. It was on offer (extremely cheap) at my local Arnold Laver. Less than £13 including cutting and VAT.
It should do nicely for my mk2 test baffles. The final version might use laminated, thicker MDF or birch plywood, if this mk2 proves good enough to warrant a "final" version. This "medite" is of very low quality - it's flaky when drilled.
I've decided not to make the unsightly cut-away in these baffles, but to locate the drivers in a good position to begin with.
I've made the baffle 30cm wide with 15cm side-wings. Considering how good the 4mm baffles sound I'm expecting something quite impressive here.
It should do nicely for my mk2 test baffles. The final version might use laminated, thicker MDF or birch plywood, if this mk2 proves good enough to warrant a "final" version. This "medite" is of very low quality - it's flaky when drilled.
I've decided not to make the unsightly cut-away in these baffles, but to locate the drivers in a good position to begin with.
I've made the baffle 30cm wide with 15cm side-wings. Considering how good the 4mm baffles sound I'm expecting something quite impressive here.
Attachments
OB design is as much empirical as theory so I always recommend knocking up cheap baffles before the final design. Chipboard (particle board) is free in the UK - you only have to look around at the tons of it being thrown away each day, and is fine for such experiments.
Bonded with some laminate flooring, and a little solid wood trim, it can make a decent finished baffle too. The example below cost me under £25 for the pair, including the grille material!
Bonded with some laminate flooring, and a little solid wood trim, it can make a decent finished baffle too. The example below cost me under £25 for the pair, including the grille material!
An externally hosted image should be here but it was not working when we last tested it.
Simon,
at least cut away some of the wings material in the upper part. Otherwise your mid will see a terribly wide baffle. I suggest beginning at the center height of the upmost woofer. Do a straight cut from there to the front edge at the top of the wing. The shape of Nuuk´s wings makes much more sense to me than yours.
You know that those wings would be prone to a pronounced quarter wavelength resonance at ~600 Hz - if you do not x-over them low enough? You will at least need 12 dB at 300 Hz or lower/steeper.
at least cut away some of the wings material in the upper part. Otherwise your mid will see a terribly wide baffle. I suggest beginning at the center height of the upmost woofer. Do a straight cut from there to the front edge at the top of the wing. The shape of Nuuk´s wings makes much more sense to me than yours.
You know that those wings would be prone to a pronounced quarter wavelength resonance at ~600 Hz - if you do not x-over them low enough? You will at least need 12 dB at 300 Hz or lower/steeper.
SimontY said:
No Simon - life isn't quite that kind! The Goodmans 201s originally cost me 25 pounds but I had them rebuilt for another 105 pounds - and they're still a bargain IMHO. The tweeters came off Ebay for a tenner, and the four 12 inch woofers (behind the grille cloth in W-baffles) were around 180 pounds.
Rudolf,
Thanks for the warning, but yep, I knew there'd be a resonance around there. I fully intend to cut the wings away behind the mid and treble drivers. I'll probably leave a little material in place, like an inch or two, for bracing purposes.
The crossover is about 250hz but I intend to bring this up a little as there's a bit of body missing. I think I'm quite far from 600hz though, fingers crossed. I don't want to start messing with 2nd order filters if I can help it.
Cheers
Simon
Thanks for the warning, but yep, I knew there'd be a resonance around there. I fully intend to cut the wings away behind the mid and treble drivers. I'll probably leave a little material in place, like an inch or two, for bracing purposes.
The crossover is about 250hz but I intend to bring this up a little as there's a bit of body missing. I think I'm quite far from 600hz though, fingers crossed. I don't want to start messing with 2nd order filters if I can help it.
Cheers
Simon
Nuuk said:
No Simon - life isn't quite that kind! The Goodmans 201s originally cost me 25 pounds but I had them rebuilt for another 105 pounds - and they're still a bargain IMHO. The tweeters came off Ebay for a tenner, and the four 12 inch woofers (behind the grille cloth in W-baffles) were around 180 pounds.
Small prices to pay for what I assume is a stunning speaker. I've heard the Goodmans 201 in a huge, ancient "boxed" speaker with cr@p tweeters and, frankly, I was blown away.
Simon
SimontY said:
Yes, they sound fantastic and as a bonus, they are an idiot's way to OB success! No crossover for the 201 and a simple cap in series with the the tweeter. A 4th order active filter for the woofers.
This begs the question, why, 40 years on, can't they make us drivers like that today?
The new baffles, although a large step forwards, revealed the frequency response aberations more clearly, so some tweaks were made to the crossover. The sound is getting quite good!
I adjusted the following because of how it sounded:
* Crossed tweeter in lower
* Crossed mid in lower and rolled off more top (was too near breakup?)
* Increased both tweeter & mid output levels
* Adjusted T-bass a little
I am attaching an up-to-date schematic.
Simon
I adjusted the following because of how it sounded:
* Crossed tweeter in lower
* Crossed mid in lower and rolled off more top (was too near breakup?)
* Increased both tweeter & mid output levels
* Adjusted T-bass a little
I am attaching an up-to-date schematic.
Simon
Attachments
Lee, Thomo of this forum, came round on Sunday and we had a long listen. This was, sadly, prior to some important tweaks that smoothed the top end and midrange.
Bass was generally good and exciting and we tested their ability to play low with some dub reggae - compilation CD "Heavyweight Rib Ticklers" compiled by Mr Scruff. One track, in particular, offered some notes that we agreed were in the 40hz region, and there's no way any ported speaker could've pulled that off so wonderfully in such a tiny listening room.
I later played some sine waves and while 30hz is audibly quite rolled off (bearing in mind the Fletcher/Munson curve effect) 40hz appeared to be fairly strong and 50hz very strong. T-bass is working here!
Also, this seems to be more anecdotal evidence for open baffles being able to produce significant output below the lowest axial room mode. Normal speakers just boom in this tiny bedroom!
Simon
Bass was generally good and exciting and we tested their ability to play low with some dub reggae - compilation CD "Heavyweight Rib Ticklers" compiled by Mr Scruff. One track, in particular, offered some notes that we agreed were in the 40hz region, and there's no way any ported speaker could've pulled that off so wonderfully in such a tiny listening room.
I later played some sine waves and while 30hz is audibly quite rolled off (bearing in mind the Fletcher/Munson curve effect) 40hz appeared to be fairly strong and 50hz very strong. T-bass is working here!
Also, this seems to be more anecdotal evidence for open baffles being able to produce significant output below the lowest axial room mode. Normal speakers just boom in this tiny bedroom!
Simon
T-bass
Graham,
I wonder if your recommendations for T-bass transformer and capacitor ratings are based on extreme SPL listening, because after extended healthy outputs I have no warming of the caps nor have I ever encountered very audible distortions due to having only 100VA transformers.
That's not to say I'm getting no distortion!! Playing those test tones loudly I think I heard some frequency doubling, which I know could be harmonic distortion of the cheap drivers, but could it also be caused by transformer saturation??
Simon
Graham,
I wonder if your recommendations for T-bass transformer and capacitor ratings are based on extreme SPL listening, because after extended healthy outputs I have no warming of the caps nor have I ever encountered very audible distortions due to having only 100VA transformers.
That's not to say I'm getting no distortion!! Playing those test tones loudly I think I heard some frequency doubling, which I know could be harmonic distortion of the cheap drivers, but could it also be caused by transformer saturation??
Simon
Bass response
Although the bass is pretty good (drums sound great!) I'm sensing a peak in the upper bass area. It's hard to guess quite where this is so I'm going to have to fire up ARTA and at least do a basic measurement.
The peak could easily be remedied by rolling off each of the woofers slightly differently as required.
I might order a couple of 2.2mH and 4.7mH to play with... but the microphone will have to come out to be really sure of fixing this.
Simon
Although the bass is pretty good (drums sound great!) I'm sensing a peak in the upper bass area. It's hard to guess quite where this is so I'm going to have to fire up ARTA and at least do a basic measurement.
The peak could easily be remedied by rolling off each of the woofers slightly differently as required.
I might order a couple of 2.2mH and 4.7mH to play with... but the microphone will have to come out to be really sure of fixing this.
Simon
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