make sure you have them greater than 3' from the back wall. 4 is better.
I thought they sounded better with absorbent material on the back of the baffles (not covering the drivers!). what are you driving them with?
have you seen the t-bass thread? I wonder which driver would be best to use with that device, the alpha 15 or the beta 15.
you are probably too busy enjoying the speakers now to take in a bunch of other questions. I know I was.
I thought they sounded better with absorbent material on the back of the baffles (not covering the drivers!). what are you driving them with?
have you seen the t-bass thread? I wonder which driver would be best to use with that device, the alpha 15 or the beta 15.
you are probably too busy enjoying the speakers now to take in a bunch of other questions. I know I was.
Crossover Suggestions
Paul,
They look great! I can see you routed all the edges, makes for a very professional look (hope you used a respirator).
With respect to the crossover, MJK selected the slopes and frequencies based upon a specific listening position and using the acoustical properties of the baffle/drivers to work with a simple set of components.
Since you are using active crossovers you have a lot more latitude. You can add filter coefficients to shape the two drivers response to have an acoustical alignment equivalent, just like the passive folks do. Alternatively, you can add eq. to the individual drivers to make them flat an octave or two beyond the crossover frequency; then just use a normal filter alignments that match for both sides, e.g. LR4. I have done both and prefer the latter, it's easier to do initially and allows quick changes to the crossover frequency. You will likely prefer the sound of an LR4 (even up to LR8) as it unloads a lot of displacement requirements from the full-range. Of course, you can move the crossover frequency around. My guess: you'll like the sound the best when pushing the frequency down while increasing the slope. With the Vifas and the slot loaded woofer 220Hz was the most cohesive sound. I now have an LR4 alignment, but will try an LR6 or LR8.
Since you have the mini-Sharc crossovers you can go for a linear-phase 100+ dB/octave using rePhase. (And don't believe the "noise" about pre-ringing. Google "Perceptual Study of Loudspeaker Crossovers Filters" you'll find a Thesis where they did double blind testing up to 700th order (!) filters with delay (to simulate non-coincident drivers). Actual science! One result- keep your crossover below 300Hz and even super steep FIR filters can't be heard. It's a good read.
Again, really good looking! Are you going to add the posters or shellac?
Z
Hi everyone, I spent yesterday cutting and gluing MDF... luckily the gluing wasn't because I'd cut to much off
The build I've gone for is the basic MJK OB design, will be using an active 2-way system for XO and power... From MJK's pdf, the Eminence Alpha 15A XO is 2nd Order at 200Hz, the FR unit's XO is 2nd Order at 500Hz.
Paul,
They look great! I can see you routed all the edges, makes for a very professional look (hope you used a respirator).
With respect to the crossover, MJK selected the slopes and frequencies based upon a specific listening position and using the acoustical properties of the baffle/drivers to work with a simple set of components.
Since you are using active crossovers you have a lot more latitude. You can add filter coefficients to shape the two drivers response to have an acoustical alignment equivalent, just like the passive folks do. Alternatively, you can add eq. to the individual drivers to make them flat an octave or two beyond the crossover frequency; then just use a normal filter alignments that match for both sides, e.g. LR4. I have done both and prefer the latter, it's easier to do initially and allows quick changes to the crossover frequency. You will likely prefer the sound of an LR4 (even up to LR8) as it unloads a lot of displacement requirements from the full-range. Of course, you can move the crossover frequency around. My guess: you'll like the sound the best when pushing the frequency down while increasing the slope. With the Vifas and the slot loaded woofer 220Hz was the most cohesive sound. I now have an LR4 alignment, but will try an LR6 or LR8.
Since you have the mini-Sharc crossovers you can go for a linear-phase 100+ dB/octave using rePhase. (And don't believe the "noise" about pre-ringing. Google "Perceptual Study of Loudspeaker Crossovers Filters" you'll find a Thesis where they did double blind testing up to 700th order (!) filters with delay (to simulate non-coincident drivers). Actual science! One result- keep your crossover below 300Hz and even super steep FIR filters can't be heard. It's a good read.
Again, really good looking! Are you going to add the posters or shellac?
Z
@ Mor2bz : Living in an apartment I get worried about annoying the neighbours if I listen to late into the evening, normally switching to headphones between 20:00 & 21:00. Should get some quality listening time as the week goes on.
I had the speakers 4' from the rear wall initially, but noticed some slight blooming of the bass, moving them to 5' out cleared this up.
Obviously the drivers are brand new with only 3hrs on them, but I haven't noticed any positional changes as the instruments range traverses the XO point of the two drivers. So far the 200Hz 12dB/oct low pass and 500Hz 12dB/oct high pass is working well. I was wondering if I might need to add some delay to the Faital Pro, but so far the sound appears well integrated as is. I like Bob Brines acid test of using a Bach Cello Concerto to test driver integration...
Active 2-way is courtesy of a miniSharc & Curryman DAC's. I'm using two YJ 2.0 blue boards [TPA3116D2 Class D amps] to power these... set at the lower 20dB gain, I should be getting 32Watt peak per channel, enough for 105dBSPL peak. I may get a miniDSP 2x4 specifically for this set-up, output is ~3dB lower than the Curryman DAC, but the loss wont be an issue.
From MJK OB design document, the Alpha 15 unit works best with this particular baffle. The Beta 15 & Gamma 15 units have a nicer Transient Response, but his conjecture was that these two drives would require larger baffles, lower XO points and will probably still not extend as low as the cheaper Alpha 15...
|-O-|
@ Z : Thanks
Yes I did wear the correctly rated filter mask for dealing with MDF, plus vacuum attachments to the power tools used... the Marvel Comic posters I had my eye on were a few inches to short to cover the full baffle. Currently undecided on shellac or gloss red paint... either would work.
I understand that MJK's criteria were 90dB SPL @ 1m and at a height of 32"... his OB design document is a fascinating read and the data well presented...
Once the drivers have had more use, I'll measure them and have a play around with the XO points. Only had the briefest of looks at rePhase so... more time needed MJK's XO points appear to be a good starting point, but tweaking is always fun
I had the speakers 4' from the rear wall initially, but noticed some slight blooming of the bass, moving them to 5' out cleared this up.
Obviously the drivers are brand new with only 3hrs on them, but I haven't noticed any positional changes as the instruments range traverses the XO point of the two drivers. So far the 200Hz 12dB/oct low pass and 500Hz 12dB/oct high pass is working well. I was wondering if I might need to add some delay to the Faital Pro, but so far the sound appears well integrated as is. I like Bob Brines acid test of using a Bach Cello Concerto to test driver integration...
Active 2-way is courtesy of a miniSharc & Curryman DAC's. I'm using two YJ 2.0 blue boards [TPA3116D2 Class D amps] to power these... set at the lower 20dB gain, I should be getting 32Watt peak per channel, enough for 105dBSPL peak. I may get a miniDSP 2x4 specifically for this set-up, output is ~3dB lower than the Curryman DAC, but the loss wont be an issue.
From MJK OB design document, the Alpha 15 unit works best with this particular baffle. The Beta 15 & Gamma 15 units have a nicer Transient Response, but his conjecture was that these two drives would require larger baffles, lower XO points and will probably still not extend as low as the cheaper Alpha 15...
|-O-|
@ Z : Thanks
Yes I did wear the correctly rated filter mask for dealing with MDF, plus vacuum attachments to the power tools used... the Marvel Comic posters I had my eye on were a few inches to short to cover the full baffle. Currently undecided on shellac or gloss red paint... either would work.I understand that MJK's criteria were 90dB SPL @ 1m and at a height of 32"... his OB design document is a fascinating read and the data well presented...
Once the drivers have had more use, I'll measure them and have a play around with the XO points. Only had the briefest of looks at rePhase so... more time needed
MJK's XO points appear to be a good starting point, but tweaking is always fun
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Burn-in
I can't find it, but I had a reference that showed how drivers burn in with different signals: they took samples every few hours and looked how the parameters changed with various sources. The end conclusion was a single tone near resonance with travel near x-max produced the fastest burn in; driver parameters stopped changing after about 6 hours. Having to use noise or music at different levels is folklore. (Don't get me wrong, I like folklore, but not in speaker building.)
I do this single tone burn-in using a signal generator/amp before assembly with the magnets in a vice(s) so it's quiet(ish). (Did this for the Auras and the Vifas.) 8-hours of this is worth months of high volume listening. Now that they are together you are probably reluctant to do this, but if you are anxious to hear them in their final state...
Glad you are protecting your pulmonary system.
I can't find it, but I had a reference that showed how drivers burn in with different signals: they took samples every few hours and looked how the parameters changed with various sources. The end conclusion was a single tone near resonance with travel near x-max produced the fastest burn in; driver parameters stopped changing after about 6 hours. Having to use noise or music at different levels is folklore. (Don't get me wrong, I like folklore, but not in speaker building.)
I do this single tone burn-in using a signal generator/amp before assembly with the magnets in a vice(s) so it's quiet(ish). (Did this for the Auras and the Vifas.) 8-hours of this is worth months of high volume listening. Now that they are together you are probably reluctant to do this, but if you are anxious to hear them in their final state...
Glad you are protecting your pulmonary system.
I see a lot of people judging the OB-worthiness of a driver based on Qts, sometimes dismissing great drivers based on Qts alone.
A high Qts driver is preferred when one is using a passive crossover as it takes advantage of the driver's resonance at Fs in order to raise the bass lost due to dipole cancellation, and therefore reduces the crossover's parts count as no additional shelving is needed to raise the bass (and all the efficiency lost along the way)
If one is using a digital crossover (miniDSP, Nadja, etc...) with enough headroom for level correction, a high Qts becomes a non-issue (and might even become a disadvantage)
I might also add that with the prices of good quality DSPs being what they are today ($99 for the 2x4 miniDSP), they are cheaper than 2nd order passive crossovers with decent parts, yet they are infinitely adjustable.
Regards
Nick
I have no affiliation whatsoever with miniDSP except the fact that I am a happy miniDSP 2X4 board user
A high Qts driver is preferred when one is using a passive crossover as it takes advantage of the driver's resonance at Fs in order to raise the bass lost due to dipole cancellation, and therefore reduces the crossover's parts count as no additional shelving is needed to raise the bass (and all the efficiency lost along the way)
If one is using a digital crossover (miniDSP, Nadja, etc...) with enough headroom for level correction, a high Qts becomes a non-issue (and might even become a disadvantage)
I might also add that with the prices of good quality DSPs being what they are today ($99 for the 2x4 miniDSP), they are cheaper than 2nd order passive crossovers with decent parts, yet they are infinitely adjustable.
Regards
Nick
I have no affiliation whatsoever with miniDSP except the fact that I am a happy miniDSP 2X4 board user
+1, I agree that the miniDSP (or other DSP) and bi-amping is the way to go - my total cost for a 2x4 XO with dual 50 watt/ch amps is $110. Much more cost effective than passive XO and infinitely adjustable on-the-fly.
Regarding low Qts drivers - they can work fine with EQ via DSP and I have heard that they provide tighter response but beware of sufficient xmax to achieve the desired SPL's at the low bass extension. I have run into this before so high efficiency PA drivers with low Qts but small xmax often cannot work in OB as bass is really dependent on moving a lot of air and the only way to do that is via stroke.
Regarding low Qts drivers - they can work fine with EQ via DSP and I have heard that they provide tighter response but beware of sufficient xmax to achieve the desired SPL's at the low bass extension. I have run into this before so high efficiency PA drivers with low Qts but small xmax often cannot work in OB as bass is really dependent on moving a lot of air and the only way to do that is via stroke.
True that, but low Qts doesn't always equate to low Xmax (expect for the pro woofers as you have already mentioned)
Which brings up another issue, I have always found that the simulated X-max of a woofer in an OB setup always seems to be overrated.
I currently mostly use MJK's worksheets, and Xmax at 1Watt can sometimes be as high as 10mm in the simulation, but in real life builds (I have already built no less than 3 different OB prototypes) I barely see the woofer moving than a millimeter or two, and that's with bass heavy music and 200 watts of amplification.
Does anyone happen to have the same observation?
Thanks Z & Nick... all good info...
I'll need to remove the drivers from the OB at some point to paint/shellac the MDF, I may try the single tone burn-in you suggest & if you can find the reference for further reading, great
Had noticed that with the slot loaded designs, the Qts was more in the 0.6-0.7 range. Plus, a lot of the commercial designs that are using active XO, look to be using drivers with even lower Qts ratings. DSP does make driver choice much easier and EQ can get ride of some quirks... The miniDSP products are good, the front and rear panels for my miniSharc enclosure should arrive tomorrow
|-O-|
So far, have listened to:
Every Kingdom by Ben Howard
Morning Phase by Beck
6 Feet Beneath the Moon by King Krule
The '59 Sound by The Gaslight Anthem
Blunderbuss by Jack White
Like Clockwork by Queens of the Stone Age
Fur and Gold by Bat for Lashes
Am very impressed so far by the sound and imaging of these OB's. Overall levels sound fairly even with a very gentle roll-off as you get down to the 45Hz f3, beyond that is just not really there... Highs are there but not overly present [just how I like it]... Mid range is just gorgeous... So far, quite pleased with the 4FE35
Will do a first measures latter on. One of both speakers running at listening position and one speaker at 1m & 32" height [as per the design spec].
I'll need to remove the drivers from the OB at some point to paint/shellac the MDF, I may try the single tone burn-in you suggest & if you can find the reference for further reading, great
Had noticed that with the slot loaded designs, the Qts was more in the 0.6-0.7 range. Plus, a lot of the commercial designs that are using active XO, look to be using drivers with even lower Qts ratings. DSP does make driver choice much easier and EQ can get ride of some quirks... The miniDSP products are good, the front and rear panels for my miniSharc enclosure should arrive tomorrow
|-O-|
So far, have listened to:
Every Kingdom by Ben Howard
Morning Phase by Beck
6 Feet Beneath the Moon by King Krule
The '59 Sound by The Gaslight Anthem
Blunderbuss by Jack White
Like Clockwork by Queens of the Stone Age
Fur and Gold by Bat for Lashes
Am very impressed so far by the sound and imaging of these OB's. Overall levels sound fairly even with a very gentle roll-off as you get down to the 45Hz f3, beyond that is just not really there... Highs are there but not overly present [just how I like it]... Mid range is just gorgeous... So far, quite pleased with the 4FE35
Will do a first measures latter on. One of both speakers running at listening position and one speaker at 1m & 32" height [as per the design spec].
I use Akabak and find that my displacements are about of same order - around 0.5 mm to 1 mm max at 1 Watt - never 10 mm (that is huge). 10 mm is about xmax for many woofers so that would indicate max power is being applied which would be a lot more than 2.83 volts. You may want to double check that.
Great to hear that the 4FE35's are working out! You may eek out a few more Hz of bass extension with some rear facing extension wings on bass portion of the OB. Maybe 6 to 8 inch MDF on both sides tapering to nothing at top to keep dipole pattern of full range.
So it sounds like the YJ Blue "Danzz" amp is a winner in a bi-amp OB application then? Do you have enough power for the bass?
It's actually pretty easy to find 15" and 18" offerings with x-max in the 6-12mm range and moderate to low Qts (0.3-0.5) if you are willing to spend $200+ each. These beasts are fantastic drivers, especially some that have Cu demodulation rings and/or Neo magnets, most have very open frames, vented spiders and vented poles. Look at offerings from B&C, Selenium, RSF, etc.
These drivers are actually a great value, but this thread is now meandering very far away from it's roots using cardboard and buyout drivers. LOL
If you actually get a driver that big moving near X-max you will need sandbags to keep that simple baffle from walking across the room and significant bracing to keep the baffle from looking like a deck of cards being shuffled.
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Or arrange them in a slot-OB architecture to get the force cancellation - still need to reinforce baffle against air pressure flex though.
What would be the effect of setting up the bass to be a bi-pole rather than di-pole? Two 15 in woofers firing into a slot open on front and back? This would get rid of both inertial force due to cone and air axial movement as well as cancelling force due to pressure difference on front and back of baffle.
Yes we are veering away from the roots of the thread... For me, this build has been cheap enough to do, without feeling putout if I didn't like the results.
The YJ Blue 'Danzz' amps are certainly holding their own. Have more than enough headroom to play about with bass EQ.
Measurements...
My main room is split into a living area and kitchen area, and is 6m by 3.4m. With the speakers situated in the living area they're sat 5' from the rear wall. When in the kitchen area they're ~8' from the rear wall
-- 5' proved to be the better overall position, boosting the bass without making it to overpowering or creating to much distortion in the mid/high range. I tried the LR24dB/oct @ ~200Hz, this worked nicely but the bass level needed dropping by 3dB witch nocked off the XO slightly... and I was getting hungry so stopped for the day
-- 8' proved better for detail but below 100Hz things weren't to good, the 4FE35 really showed off what it can do here.
Pic 1: IR at 1 meter & 34.5" height, speaker 8' from rear wall ... quite open position
Pic 2: Levels & harmonics at 1m & 34.5", 8' from rear wall. Original XO of 200Hz LR2 & 500Hz LR2.
Pic 3: Levels & harmonics at 1m & 34.5", 8' from rear wall. XO of 200Hz LR4 & 250Hz LR4.
Pic 4: From seating position, both speakers at 8'. Original XO.
Pic 5: From seating position, both speakers at 5'. New XO and bass levels dropped 3dB. Need to move the HP XO from 250Hz to 200Hz and this should be OK.
Measure were taken at -34dB to get ~70dB SPL listening level... Though I think the first one was set a little lower. No EQ done.
The YJ Blue 'Danzz' amps are certainly holding their own. Have more than enough headroom to play about with bass EQ.
Measurements...
My main room is split into a living area and kitchen area, and is 6m by 3.4m. With the speakers situated in the living area they're sat 5' from the rear wall. When in the kitchen area they're ~8' from the rear wall
-- 5' proved to be the better overall position, boosting the bass without making it to overpowering or creating to much distortion in the mid/high range. I tried the LR24dB/oct @ ~200Hz, this worked nicely but the bass level needed dropping by 3dB witch nocked off the XO slightly... and I was getting hungry so stopped for the day
-- 8' proved better for detail but below 100Hz things weren't to good, the 4FE35 really showed off what it can do here.
Pic 1: IR at 1 meter & 34.5" height, speaker 8' from rear wall ... quite open position
Pic 2: Levels & harmonics at 1m & 34.5", 8' from rear wall. Original XO of 200Hz LR2 & 500Hz LR2.
Pic 3: Levels & harmonics at 1m & 34.5", 8' from rear wall. XO of 200Hz LR4 & 250Hz LR4.
Pic 4: From seating position, both speakers at 8'. Original XO.
Pic 5: From seating position, both speakers at 5'. New XO and bass levels dropped 3dB. Need to move the HP XO from 250Hz to 200Hz and this should be OK.
Measure were taken at -34dB to get ~70dB SPL listening level... Though I think the first one was set a little lower. No EQ done.
Attachments
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It's pretty easy to get distortion figures that low at 70dB. Can you repeat what they look like at 90dB?
Z
That's something I can certainly do later in the week, 90dB levels will be of more interest I guess... However, the A7.3 were also measured at ~70dB as that represents the level I listen at. IIRC, with the A7.3, as the SPL level increased the THD increased by roughly the same amount... keeping ~45dB below the fundamental
Just figuring out the measure levels required for 90dB, should be -15dB for the 4FE35 and about -11dB for the A7.3 or 1Watt and ~2.6Watt respectively... I think.
Just figuring out the measure levels required for 90dB, should be -15dB for the 4FE35 and about -11dB for the A7.3 or 1Watt and ~2.6Watt respectively... I think.
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Buildmesomething,
I would be interested to see if the Faital Pro 4FE35 has the peaks and dips above 10khz. That efficiency gain already looks like a nice advantage for folks with flea watt amps.
If you have time, can you also get a 15 deg and 30 deg off axis measurement with just one speaker?
I would be interested to see if the Faital Pro 4FE35 has the peaks and dips above 10khz. That efficiency gain already looks like a nice advantage for folks with flea watt amps.
If you have time, can you also get a 15 deg and 30 deg off axis measurement with just one speaker?