say it as it is
pfm Member
I think your work is amazing kind of in aw as way above my skill level. I admit to getting lost in the details bit above my head. If DIY speakers are like DIY power amps I'd love a pair
Not just another speaker build.
- Thread starter Fatmarley
- Start date
Fatmarley
"It appears my intelligence circuits have melted"
You're making me blush
Obviously, the original plan was to build something that anyone could copy, but I can't imagine anyone slicing up drivers. Not only that, but the midrange frequency response changes a surprising amount, depending on the type and density of stuffing.
If they end up sounding like I hope they do, I'll happily let others listen to them to see if they think it's worth the effort to copy them.
More experiments to follow...
martin clark
pinko bodger
Completely agree with this, and appreciate the large amount of effort involved in disassemble, cut, reassemble, test measure; repeat- and all controlled enough to pick up the small nuances in each change.
Keep going Mat! It's great stuff. ATB.
Fatmarley
"It appears my intelligence circuits have melted"
Although not this design, there's something that others may find interesting because I know I did.
When I built a 3-way with a Scanspeak 10" woofer in a sealed enclosure, I fitted an exhaust in the side. It was a 2" X 9 plastic pipe with lots of holes drilled in it. Loosely covered in Monacor mdm3, and the covered in cling film.
Now this is the bit that surprised me, when bass heavy music was playing at very loud levels, you could put your hand over the exhaust, and feel NO air pressure coming out of the hole. You could visibly see the driver moving backwards and forwards a long way, yet feel nothing from the exhaust. I remember there was a single impedance peak when measured with my DATS, so that confirmed it was still acting like a sealed enclosure.
As I said earlier, it really opened up the low frequencies, so was well worth doing.
When I built a 3-way with a Scanspeak 10" woofer in a sealed enclosure, I fitted an exhaust in the side. It was a 2" X 9 plastic pipe with lots of holes drilled in it. Loosely covered in Monacor mdm3, and the covered in cling film.
Now this is the bit that surprised me, when bass heavy music was playing at very loud levels, you could put your hand over the exhaust, and feel NO air pressure coming out of the hole. You could visibly see the driver moving backwards and forwards a long way, yet feel nothing from the exhaust. I remember there was a single impedance peak when measured with my DATS, so that confirmed it was still acting like a sealed enclosure.
As I said earlier, it really opened up the low frequencies, so was well worth doing.
Fatmarley
"It appears my intelligence circuits have melted"
Thanks Martin. It's very messy, time consuming and drives the GF mad, but I find the results fascinating, and not always as expected.
cooky1257
pfm Member
Tumbleweeds go with the territory Matt, at least no one has hijacked on your thread by posting about their own project...
You looked like a man with a mission so I've chosen to step back and watch how it plays out though it did occur to me to maybe chose a tweeter that could come in a bit lower to mitigate the 2 mid hf peaks....
You looked like a man with a mission so I've chosen to step back and watch how it plays out though it did occur to me to maybe chose a tweeter that could come in a bit lower to mitigate the 2 mid hf peaks....
Also, DIYAudio might be a better forum to have interactions with more people who know what you're doing. DIY kind of seems like a vestigial appendage on the side of PFM. PFM seems to be more about British products, politics, how to throw away money on something new you didn't know you needed, and MQA.
Fatmarley
"It appears my intelligence circuits have melted"
The Wavecore TW030WA12 can be crossed surprisingly low, and I'm not sure if there's anything out there that can be crossed lower. Maybe the Seas T35C002 could? but it's not cheap. The datasheet says the Wavecore is usable down to 1.5khz, but although crossing that low helps reduce the Faitals breakup, it doesn't eliminate it.
I'll do some distortion and off-axis response measurements when I get a chance. Unfortunately I didn't do that to the unmodified drivers, but I can compare to Vance Dickasons measurements - https://audioxpress.com/article/test-bench-faital-pro-6rs140-midwoofer-midrange
Fatmarley
"It appears my intelligence circuits have melted"
Also, DIYAudio might be a better forum to have interactions with more people who know what you're doing. DIY kind of seems like a vestigial appendage on the side of PFM. PFM seems to be more about British products, politics, how to throw away money on something new you didn't know you needed, and MQA.
PFM just feels more like home to me.
But that’s like dropping your keys in a dark alley and looking for them under a streetlight.
... I sometimes think I might put up a pic of a project and then @booja30 shows us his Sansui rebuilt and I think 'maybe not'!
In all honesty I was using part recommendations from a thread on audiokarma.org!
Fatmarley
"It appears my intelligence circuits have melted"
No, it's another thing I made up, and I suppose it was just a lucky guess because it worked. With a sealed enclosure, you can model a leak in software, so I knew what to expect in that regard (lowers QTC and uses a bit of extra cone excursion).
I looked up how car exhausts and gun suppressors worked. The idea was to allow air movement, but also reduce noise. I can't remember if I measured the output with a microphone in the exhaust entrance though. There was going to be a mk2 version with a sleeve over the top, but I went on to build something else, and have been building ported speakers ever since.
Fatmarley
"It appears my intelligence circuits have melted"
It's not like that in the speaker section. There's only a small handful of knowledgable people, the large majority haven't got a clue. The partsexpress forum used to be excellent, but they changed the software, and now it's really slow and annoying. They also got more strict with the moderation, and don't allow talk of other loudspeaker sellers, so it's gone downhill.
cooky1257
pfm Member
I see Dickason suggests a 2.3khz xover point.
Fatmarley
"It appears my intelligence circuits have melted"
Troels Graveson crosses the Faital even higher at 2400hz, and that's 2nd order too (shallow slope for those who don't know), so maybe the breakup isn't that audible? It would be interesting to hear if there's any audible sibilance with Troels speakers because the 7 to 8khz area is where that problem occurs.
I personally wouldn't like the dip from 800hz to 2000hz in Troels design, but I know he's mentioned in the past that he hates a peak a that point, so it shows we all like different things - http://www.troelsgravesen.dk/Faital-3WC.htm
You've got that part spot on in my view, I did alot of practical testing and built quite a few open baffle speakers over the years and it's all about reducing the air load on the loudspeaker, all loudspeaker drivers work best if used well in their limits, they all get seem to get ratty.. one way or another at thier extremes.. so try not to go too wide band with them.
It's all about picking the best drivers and then matching them with the others to get a full and levelish frequency response.. its more down to trial and error and a little good judgement
Speakers that may look the part often don't sound that good. How a speaker copes with dynamics across its frequency range is an example.
Decent drivers are expensive, and then need other expensive drivers to match, it's a bit of a minefield really if you want high performance, but your really investing in your knowledge in the long run.
Fatmarley
"It appears my intelligence circuits have melted"
That was part of my reasoning for the hybrid open baffle design. I wanted all the benefits of open baffle, but with as little loss in low frequency output as possible. For those that don't know, here's a simulation of open baffle (grey line) vs sealed (Blue line). As you can see, put a driver on an open baffle, and you lose a lot of output low down. I just hope I have enough output low down to cross around 400hz. If not, I'm going to have to change either the midrange or woofer.
Fatmarley
"It appears my intelligence circuits have melted"
Some rambling thoughts - As I said at the start of the thread, I try to use drivers with low Q and low MMS for a high power to weight ratio, BUT perhaps with this hybrid open baffle design, higher Q drivers may be better, because now they are not fighting the internal air pressure of an enclosure, and the higher Q may allow a bit more low frequency output.
With the 2" x 8" slots, I just looked at the depth of the driver and made sure the slot was a bit deeper to be sure of no reflections coming back through the cone. It may be that a different sized slot would better. I may make the next one 1" to see if that does anything different. I did try covering them with duct tape but that just gave an odd response. Not only that, but I'm also going to try lining the inside of the slot with wool felt, because I'm concerned there may be reflections.
With the 2" x 8" slots, I just looked at the depth of the driver and made sure the slot was a bit deeper to be sure of no reflections coming back through the cone. It may be that a different sized slot would better. I may make the next one 1" to see if that does anything different. I did try covering them with duct tape but that just gave an odd response. Not only that, but I'm also going to try lining the inside of the slot with wool felt, because I'm concerned there may be reflections.