OB compact 3way nearfield monitor

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
This topic started over in the thread EVA foam for performance speaker enclosures but we decided to split it off into a separate thread over in the multiway section. Although I will be building with the excellent EVA foam, several friends (xrk, jcarr) who are also interested in similar designs may build with more conventional materials and slight variations of the theme. If you want to discuss the merits of EVA foam, please join into the discussion over in that thread.

Nearfield monitors are used in studios for detailed listening during the mixing, composing, recording process. Nearfield is usually defined as a listening distance of 0.4-1.6 meters. Longer listening distances than that are classified as midfield and farfield and require different design optimizations. Most DIY speakers are designed for living rooms and home theater applications and are not optimized for nearfield use.

A few things are important when designing nearfield monitors

  • reducing center-to-center spacing of drivers. If this is not minimized, this will lead to lack of integration of the drivers (not sounding like one speaker but instead hearing each driver separate) and less than desirable lobbing in the crossover region.
  • controlling directivity and dispersion. nearfield monitors are usually placed on top of mixing decks or with keyboards and other equipment very close by and often in smallish studio spaces.
  • nearfield monitors are usually designed for improved clarity and imaging, flat frequency response, but less for max SPL because of the short listening distances. They must sound good at lower SPL levels.
  • compact size is important because it needs to fit into a studio space at about 1meter listening distance.
For my version of the 3way I am going to focus on using the Peerless TG9FD10 or ScanSpeak 10f/8424 as the midrange driver, along with a small neo-magnet dome tweeter and woofers in the 8"-10" range (Sd 200cm2-450cm2 range). I will start with the Vifa DQ25 tweeter but maybe explore others. For the woofers I am starting with the very inexpensive GRS 8PF but if the design works, I will upgrade to better 8" drivers with more xmax and better motors (maybe peerless 830667). This first design is going to focus on an open baffle arrangement with slot-loaded woofer.

I am also building a 2way 1"+6" monitor based on the SB Acoustics Satori MW16p-04 and Dayton RS28f. My feeling is that even though there are a few excellent 1"+8" 2ways, the 8" and 10" woofers are better suited to 3way designs.

I am starting this thread as a place to log my experiments and explorations as I build these nearfield 3way monitors and a place for others to explore similar builds. I will be asking the moderators to move the relevant discussion from my other thread over here.

But here is a DQ25 + TG9 open baffle test platform for the start of this compact 3way project with XRK.

508185d1444467813-eva-foam-performance-speaker-enclosures-p1110610.jpg

My idea here was to test an open baffle with the TG9, and also test if I would prefer the TG9 alone or with a small neo tweeter. I choose the DQ25SC15-04 since zaph gives it really high marks and uses it in several of his speakers. It is also a titanium dome so might be quite different to the silk dome RS28f that I already have. I have put it into a relatively simple EVA rectangular open baffle and have just offset the drivers slightly to try to control the baffle diffraction.
508186d1444468415-eva-foam-performance-speaker-enclosures-dq25-tg9-ob-straight-response.gif


The center to center spacing of the drivers is only 77mm so I can do any crossover under 4800hz. I decided to aim at a 4000hz LR2. After a little EQ I was able to hit the LR2 target really well with excellent summing. I time delay the tweeter by 0.06msec to get the drivers time aligned. Somehow manged to get a linear phase and near perfect step response. Maybe because of the really high 4khz crossover?
Should be easy to mate this to a woofer maybe around 250-350hz. All measurements at 0.5m and approximately 80db at 0.5m.
508179d1444469646-eva-foam-performance-speaker-enclosures-dq25-tg9-ob-lr2-4khz-xo.jpg

508180d1444469646-eva-foam-performance-speaker-enclosures-dq25-tg9-lr2-4khz-dist.jpg


508182d1444467723-eva-foam-performance-speaker-enclosures-dq25-tg9-lr2-4khz-fr.jpg

508181d1444469799-eva-foam-performance-speaker-enclosures-dq25-tg9-ob-lr2-4khz-impulse.jpg



I may have over eqed this, but I will start with this and see how I like it. Getting the DQ25 to hit the LR2 4khz target was pretty easy. TG9 was a little lumpy in the rectangular open baffle.
508184d1444469799-eva-foam-performance-speaker-enclosures-dq25-tg9-ob-raw-drivers.jpg


dq25
peak 1900hz -8db q0.5
BW6 7khz 0.06msec delay invert phase
tg9
LR2 4khz
low shelf 400hz +7db q0.7
peak 3400hz -2db q5
peak 1540hz -6db q10
peak 880hz -5.5db q2
not sure I would want to do this with a passive crossover though.

So first impressions are really good. So far I am fairly certain I prefer it with the dome tweeter compared to just the TG9, but the eqed TG9 sounds pretty good. Easy to mute the DQ25 and remove the XO to hear the TG9 fullrange.

Still playing around with setup. It's also my first open baffle build so leaning. But I live with acoustat electrostatic speakers so I know how a dipole open baffle speaker sounds. 4000hz is really high even for such small drivers, so I might also try an LR2 in the 3000-3500hz range. But so far I am impressed how well these two drivers sound together in an open baffle. Might be one of the smallest 2way open baffles out there :)

Also built an MTM version with a pair of 4ohm TG9FD10-04 (post #128). Still evaluating which I prefer. Might prefer the simpler TM version but the MTM does seem to have lower distortion, it can play louder, and I also like the look of the MTM better.
515298d1447897208-ob-compact-3way-nearfield-monitor-p1110632.jpg
 

Attachments

  • DQ25-TG9-OB-LR2-4khz-XO.jpg
    DQ25-TG9-OB-LR2-4khz-XO.jpg
    106.1 KB · Views: 1,826
  • DQ25-TG9-LR2-4khz-dist.jpg
    DQ25-TG9-LR2-4khz-dist.jpg
    104.7 KB · Views: 1,832
  • DQ25-TG9-OB-LR2-4khz-impulse.jpg
    DQ25-TG9-OB-LR2-4khz-impulse.jpg
    67.4 KB · Views: 1,831
  • DQ25-TG9-LR2-4khz-FR.jpg
    DQ25-TG9-LR2-4khz-FR.jpg
    76.6 KB · Views: 1,779
  • DQ25-TG9-OB-LR2-4khz-CSD.jpg
    DQ25-TG9-OB-LR2-4khz-CSD.jpg
    104.7 KB · Views: 101
  • DQ25-TG9-OB-raw-drivers.jpg
    DQ25-TG9-OB-raw-drivers.jpg
    102.8 KB · Views: 1,706
  • P1110610.jpg
    P1110610.jpg
    101.7 KB · Views: 2,079
  • dq25-tg9-OB-straight-Response.gif
    dq25-tg9-OB-straight-Response.gif
    51.1 KB · Views: 1,800
Last edited:
This white foam is defintly looking fine !

Does it need a low pass after 20 K because the resonance peak of aluminium ? maybe not seen by the ECM-8000 because above 20 K ? What happens if you apply such electronic EQ with a steep LP ? Nicer at the ear... The passive filter is correct enough ?

Having an aluminium, I can say I like it a lot but there is not the savour of a T33 tweeter (SP1191) from Kef in the 80s' 104/2 ref ! While the aluminium have a greater sound precision with piano, some guitars ! cymballs ! Hey metalic instruments.

The Seas 27TBFCG seems smooth and loved by a lot of people.

Nice looking than your OB, Hey maybe better than sealed ?!
 
Jeshi, I have please an off topic question : do you know the max spl output your 6.5 Satori is enable to throw ?

Someone said to me most of the dynamic peaks in the modern disc are not higher than 3 dB above the average listening volume ! I was surptised of that but if true I have to reconsider the choice of the design I want to sketch with the 6.5" PHL Audio 1040 (100 dB efficienty - 500 hZ 6 Khz range !).

Is there a good method to know the max spl a driver can output ? Is there a formula with cone size and Xmax e.g. ?

Sorry for the off topic ! Btw thread subscribed with this new design !Tomorrow, listenings for round 5 :) !
 
The DQ25 resonance peak is above 20khz and not so large and it doesn't really ring. From zaphs measurements
Vifa_DQ25SC16-04-FR.gif

Vifa_DQ25SC16-04-CSD.gif


In comparison the 27TBFCG rings a lot more, but it is at a higher frequency. Also the 27TBFCG is a large device (not a small neo) so I would not be able to get such a close 77mm center-to-center distance with this design.
Seas_27TBFCG-CSD.gif


So far I am impressed with the little DQ25 and I can see why zaph calls it "The DQ25 is one of the best neo domes out there in anywhere near 4 times it's price range".
I don't need to do any filtering in the 15khz and up region. Although I felt I needed to do that with the SB65, I don't feel that need with the DQ25.

I am not sure yet if I like sealed, aperiodic TL or OB yet with my small drivers. But the sealed RS28f/Satori is still without any doubt the best speaker in my collection and one of the best 6+1 monitors I have heard.

A little family picture for everyone
508201d1444478307-eva-foam-performance-speaker-enclosures-p1110613.jpg


I may have to try the DQ25 with my Satori at some point but the RS28f works so well in that speaker that I don't really want to change it.
 

Attachments

  • P1110613.jpg
    P1110613.jpg
    136.6 KB · Views: 1,833
Last edited:
no worry about off topic in this thread as long as it is related to something I have posted. This is really more a "jeshi's various builds with EVA" thread.

The way I calculate max SPL is to put the driver into unibox and raise the level until I hit the xmax. UniBox - Unified Box Model for Loudspeaker Design - Kristian Ougaard
for example here is my satori in a sealed box with a linkwitz transform (close to my current one) and the model says my max SPL is probably 90db. My design goal for the satori is a nearfield monitor for my home studio so I will listen at 1m distance and usually around 82db, so the 90db max is more than enough headroom. And in practice I find the sealed-LT Satori can play louder than I need and definitely louder than my focal CMS40 speakers.
508202d1444479038-eva-foam-performance-speaker-enclosures-cb-response-sb-acoustics-satori-mw16p-4-10l-39hz-q0.7-sub-39hz-90db.gif


For this I am using an xmax of 3.5mm since I read in several places that even though the satori has a published xmax of 6mm, the kipple data seems to indicate that it is more linear in the under 3.5mm range. So this is a very conservative estimate of max SPL for the satori. If I use the 6mm xmax then is shows 94db max SPL.

The Satori MW16P-4 is amazing in the midrange and does enough bass. The best way to increase your max SPL is to add a subwoofer (roll off the 6" at 80hz and add a 10" sub to handle the 30-80hz range). For example in the plot above, you can see that the Satori can do 100DB before the conservative 3.5mm xmax if you roll it off at 100hz.
 

Attachments

  • CB Response SB Acoustics Satori MW16P-4 10L 39hz q0.7 sub 39hz 90db.gif
    CB Response SB Acoustics Satori MW16P-4 10L 39hz q0.7 sub 39hz 90db.gif
    22.6 KB · Views: 1,615
Last edited:
Founder of XSA-Labs
Joined 2012
Paid Member
Dual TG9FD & DC28F in OB

Ok, I am going to try to follow your experiment but do it a little differently as I already have a setup with dual TG9FD's and a DC28F silk dome on an 18in wide plywood OB ready to go. So mostly a DSP XO topology experiment...

I am going to take a slightly different direction on the XO, sort of aiming for Harsch style or other asymmetric transient perfect design.

Here is a photo of the setup:

508211d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-ob-photo.png


Here are the raw responses (an 18in baffle gets you a lot more bass extension before falloff):

508204d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-raw.png


Here is raw and EQ'd response for TG9FD:

508205d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-raw-eq.png


Here is raw (700Hz 2nd order Bessel HPF for protection) and EQ'd response for DC28F (with 2nd order Bessel at 4kHz):

508206d1444480615-eva-foam-performance-speaker-enclosures-dc28f-raw-eq.png


And here is the combined acoustic response with 4kHz LR4 on the TG9FD LPF and 4kHz Bessel on the DC28F HPF, resulting in 3850 Hz acoustic XO frequency as demonstrated by null from positive polarity and zero delay. However, adding 0.16ms of delay on tweeter (close to Harsch value with acoustic offset of TG9FD) and flipping to all positive polarity we get a nice integration:

508207d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-xo.png


Here is the phase which is pretty looking linear:

508208d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-phase.png


Here is the corresponding impulse and step response - transient perfect like yours:

508209d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-ir-sr.png


Here is the distortion - which says that when I add the woofer for a 3-way, if I cross above 400Hz, distortion should not be an issue:

508210d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-hd.png


So, it appears that a transient perfect can be obtained from an electrical LR4 and a Bessel. Probably in acoustic domain if I over-laid the textbook functions we are close to Harsch's BW4 and BES2 recommendation. However, the sharpness of the rise on the SR is better than what I normally achieve with the Harsch, so this may actually, be different. The key is to keep all polarities positive and adjust delay until integration is smooth and null dip goes flat.

I listened to one song and it sounds quite good - characteristically transient perfect. Bass is a bit thin :)

One may ask, why not just use the TG9FD all by itself, it seems to look pretty good after EQ? Well here is the TG9FD only phase:

508214d1444481264-eva-foam-performance-speaker-enclosures-tg9fd-only-phase.png


And here is the TG9FD only IR and SR - not as good as the combined 2-way sysem - mostly because such a steep cutoff is acoustically imposed on the driver at the high frequencies. Byrtt has shown electronic experiments that show this causes the overshoot and ringing in the IR and leading peak on the SR.

508215d1444481264-eva-foam-performance-speaker-enclosures-tg9fd-only-ir-sr.png
 

Attachments

  • TG9FD-DC28F-OB-photo.PNG
    TG9FD-DC28F-OB-photo.PNG
    471.6 KB · Views: 1,610
  • tg9fd-dc28f-hd.png
    tg9fd-dc28f-hd.png
    217.4 KB · Views: 1,611
  • tg9fd-dc28f-ir-sr.png
    tg9fd-dc28f-ir-sr.png
    85.3 KB · Views: 1,814
  • tg9fd-dc28f-phase.png
    tg9fd-dc28f-phase.png
    108.5 KB · Views: 1,714
  • tg9fd-dc28f-xo.png
    tg9fd-dc28f-xo.png
    115.8 KB · Views: 1,733
  • dc28f-raw-and-eq.png
    dc28f-raw-and-eq.png
    90.2 KB · Views: 1,613
  • tg9fd-raw-and-eq.png
    tg9fd-raw-and-eq.png
    88.8 KB · Views: 1,596
  • tg9fd-dc28f-raw.png
    tg9fd-dc28f-raw.png
    89.6 KB · Views: 1,618
  • tg9fd-only-phase.png
    tg9fd-only-phase.png
    105.7 KB · Views: 1,721
  • tg9fd-only-ir-sr.png
    tg9fd-only-ir-sr.png
    85.9 KB · Views: 1,698
Last edited:
Excellent work and fast too (as usual). Mine is bass thin also, but the plan is to add a woofer so it really doesn't need bass below 300hz. Yours is definitely flatter before EQ though and appears to need less EQ adjustments than my tiny OB. With the miniDSP this is not a problem, but if we wanted to do a passive crossover then the large OB (or sealed or dagger or TL) would probably make more sense.
The dual TG9 definitely seems to have lower distortion though in the 200hz and up region. I think I am at a lower SPL than you but the pattern seems to hold. Both builds highlight the extra distortion that shows up below 200hz when run without a woofer
508180d1444469646-eva-foam-performance-speaker-enclosures-dq25-tg9-lr2-4khz-dist.jpg

508210d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-hd.png


very cool!
 
Founder of XSA-Labs
Joined 2012
Paid Member
This white foam is defintly looking fine !

Does it need a low pass after 20 K because the resonance peak of aluminium ? maybe not seen by the ECM-8000 because above 20 K ? What happens if you apply such electronic EQ with a steep LP ? Nicer at the ear... The passive filter is correct enough ?

Having an aluminium, I can say I like it a lot but there is not the savour of a T33 tweeter (SP1191) from Kef in the 80s' 104/2 ref ! While the aluminium have a greater sound precision with piano, some guitars ! cymballs ! Hey metalic instruments.

The Seas 27TBFCG seems smooth and loved by a lot of people.

Nice looking than your OB, Hey maybe better than sealed ?!

The DQ's are titanium domes.
 
Founder of XSA-Labs
Joined 2012
Paid Member
Yes, I intend to add a woofer(s) too. Wondering if I should just make the TG9FD bandpass symmetric with LR4 HPF and then Bessel LPF on the woofers? The LR4 on the TG9FD as HPF will definitely control the distortion below the XO freq.

What is PSY smoothing? I don't have that option on my REW (maybe need to update?).

Psychoacoustic based smoothing?
 
Yes, I intend to add a woofer(s) too. Wondering if I should just make the TG9FD bandpass symmetric with LR4 HPF and then Bessel LPF on the woofers? The LR4 on the TG9FD as HPF will definitely control the distortion below the XO freq.

What is PSY smoothing? I don't have that option on my REW (maybe need to update?).

Psychoacoustic based smoothing?

Yeah it is Psychoacoustic smoothing. I am running v5.13 of REW. But the latest version makes the capture pictures smaller for some reason.

Getting late here in Japan, but I will try to duplicate your Harch crossover with my setup soon. A symmetric LR4 bandpass on the TG9 does sound like a good idea. Just to confirm when you say "4kHz LR4 on the TG9FD LPF and 4kHz Bessel on the DC28F HPF" is that the electrical XOs or the target acoustic? I think it is the electrical XOs you apply
 
Thanks Jeshi for the link and input about max spl ! The black enclosure has also an incredible pro looking : angular corners are "Something" (very very nice).

@ Xrk971 : yes, I meaned metal cone ;) (in the sense : non fabrik family sound !).

Did you guys try the Neo 3 planar tweet from G&B (with a face plate wave guide in its PDR version) ?

Will be pleased with the review of this DQ's vs the other ones of the collection !
 
And here is the combined acoustic response with 4kHz LR4 on the TG9FD LPF and 4kHz Bessel on the DC28F HPF, resulting in 3850 Hz acoustic XO frequency as demonstrated by null from positive polarity and zero delay. However, adding 0.16ms of delay on tweeter (close to Harsch value with acoustic offset of TG9FD) and flipping to all positive polarity we get a nice integration:

508207d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-xo.png

That is very interesting. So all you need is a LR4 LP and a BE4 high pass, ad .16ms delay, and you get that... :) Very nice. I suppose you could do this with an acoustic offset if you wanted to use a passive XO.
 
I am going to take a slightly different direction on the XO, sort of aiming for Harsch style or other asymmetric transient perfect design.

Here is the phase which is pretty looking linear:

508208d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-phase.png


Here is the corresponding impulse and step response - transient perfect like yours:

508209d1444480615-eva-foam-performance-speaker-enclosures-tg9fd-dc28f-ir-sr.png

I wouldn't call this STEP transient perfect but it has a good continuous flow in the phase. Transient perfect STEP would be flying higher for a longer duration.

My step on the same scale shows the difference:
transient.jpg


See how it's still way up in the air? The triangle theory is fine but you have to look at the scale it is plotted on. In theory with flat response (the above STEP is with a different target) my step "crosses" the zero line at about 15 ms. Now this is of coarse a highly manipulated result. But that's how it looks if you get a flat phase result that follows the FR. The results Barleywater and BWaslo showed are also still flying high at ~4 ms. Of coarse it also depends on the low end extension. But the example in Stereophile of the Dunlavy IV was actually a bad example. It was measured way to close to really see it's step response. The speaker was optimised for coherency at a much larger distance. Once John Atkinson realised that he published a measurement at 3 meter:
An externally hosted image should be here but it was not working when we last tested it.

which shows the step is still above zero at the 4 ms point (end of graph) and without knowing what the actual design distance would be the result could even have been better at 4 meter.

But the results you both are getting here show a smooth phase turn throughout the entire bandwidth. I.m.h.o. that is a good thing. It means the crossovers are smooth, the named targets are one thing, actually hitting them acoustically is key. This shows that EQ-ing to hit the target helps in getting a smooth transition from one driver to the next. It would also make it possible to straighten the phase with Rephase (for example) to get that transient STEP.

You might want to check the STEP at the listening position if you play with delay of the tweeter vs the woofer. The distances to the microphone are different if you step further back. I'd want it optimised at the listening position.
That's probably true in Jeshi's case with the small OB setup but I can't imagine listening to that rather big MTM at say 0.5 meter distance? So optimising and measuring the STEP at the listening distance would make the most sense. That's why you shouldn't measure the STEP of a big Dunlavy IV at close distances. The arched baffle, crossover and (passive) EQ are all optimised to hit target at that listening position. The big problem we have is room effects messing up the measurements to get it right...
 
Last edited:
Founder of XSA-Labs
Joined 2012
Paid Member
Wesayso,
Your SR is the most impressive of any speaker I have ever seen. How can we ever compete with you? To be fair, the TG9 here has bandwidth from 100Hz up vs your array 17Hz so of course it won't have much staying power beyond a few ms. Once integrated with a woofer that will take it down to 40Hz it will do better but will still be >2x less than your 17ms. So I am guessing maybe 7ms at best.

@GregB, the Bessel is 2nd order electrical. There is some EQ shaping to flatten things before the XO so it would take more of an effort to have a good baffle that is either offset, trapezoidal, or rounded edges to minimize diffraction and also flush mount the tweeter bezel - which I have not done here.
 
Wesayso,
thank you for that explanation. I understand the step response and the stereophile graph so much better now. From my previous reading of that article, I though the step was supposed to be a gently sloping triangle. Now I know what a really good step response should look like. I am very impressed, even more so knowing that this is your EQed TC9 array. Really shows what multiple drivers and EQ can do.

Also makes a lot of sense to optimize and measure at the listening distance. I may actually just start to build and measure the speakers in their final position and place the microphone in my siting position. Really optimize for the listening position.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.