Forum developed GR-R WAW speaker

Folsom · « **on:** 4 Jul 2018, 12:08 am »

Hey everyone.

I've been wanting to get started on something like this, but I don't have the wood shops available that I did to me any longer. I thought I'd pass on the concept and see if maybe some people on the forum would be into it. I know Danny is rather busy, too, so it may be up to us for a moment to expand on some possible projects.

What I've been wanting to do is make a capable speaker that is a WAW, woofer assisted wideband. Maybe that's the right acronym, I'm not even sure! The point is to use a fullrange driver with a bass driver.

What I'm proposing to do differently is use Bipole drivers for bass because of how they act. Even small drivers in bipole can produce powerful bass, surprising bass. I've heard 4" drivers absolutely pound before in Bipole. What is unique is that is doesn't have baffle step loss because both drivers are opposite firing in phase. What also is unique is the vibrations for the cabinet cancel really well - spikes and such don't do a lot for them so you can just use some felt pads or extend the base in some fun way with woof. The bass spreads well in a room.

The other component is I want to really make it sound surprisingly natural. So The fullrange will use an aperiodic vent. The bass drivers will sound very natural also with aperiodic vent, but they could also be converted to a transmission line if someone is skilled enough. A TL line will put out very impressive low bass.

Now onto what it looks like. I drew a simple box to show you. I would line the midrange with no-rez and stuff it decently. The stuffing is good because in this case the driver can use extra dampening. The ape vent should help keep the resonance of the internal chamber down to keep the sound natural. The bass with the ape vent will be very natural sounding.

The reason the bass drivers (M165) are side firing is that the LGK needs as narrow of a baffle as it can get. At this point the narrowest is approximately 6". All edges should be rounded over, and felt would be pretty trick in a patch around the LGK. The LGK could be offset to one side some.

The crossover isn't completely decided yet. But it's looking at Danny's baffle compensation should work (I took a guess at the values), along with a 60mf Solen bypassed by a 6uf Gen1 Sonicap in series with the LGK & BSC - and my own little change following that. The M165's will need a 2nd order around 300hz. Keeping the LGK slope a little more gentle is intentional because the M165's should be setup to be on a 3 way switch to adjust for bass. As is at 89.9db they will be too sensitive for the nominal w/ BSC 85db LGK, so the M165s will have to be attenuated down to 85db, but in small rooms the gain may still be too much. For that reason a switch could be used to drop it down -3 and -6db. The details aren't fully settled on that, yet. I'm not certain if a 300hz first order will roll the LGK off better than in simulation yet or not, for example.

The FR response I'm seeing has a little bit of a dip at 4khz, but is actually surprisingly smooth otherwise. It looks like the baffle size at 6" wide may smooth the higher end of the LGK. Granted it may be a minor blurring, but that may not be a problem at all for the type of listener who wants smooth, natural sound, with expensive sounding bass.

Right now It's looking like the box would do well at 42" H x 6" W x 12" D w/ a 6" x 6" chamber for LGK on top. This gives around 1 cubic foot for the woofers. With them adjusted to 85db and a touch of room gain, you should be getting appreciable bass into the 40's, if not some into the 30's albeit quieter than a real sub. The LGK would end up about ear level for recliners and such. The ape vents need 4.3" cut outs, so this is right at the max with .75" depth walls.

I thought about placing the M165's towards the bottom but I'm worried too much floor loading won't sound as natural.

Anyways, this project will get my support to work on the electrical side. I suspect that while Danny doesn't have time to build boxes, were someone near him to bring one to measure he might have some say so in crossovers (probably will have some say so period).

Whelp, I guess now we see where this goes, if anywhere...

gab · « **Reply #1 on:** 4 Jul 2018, 02:44 pm »

try the free book

http://grailloudspeakers.com/

http://www.enjoythemusic.com/magazine/manufacture/0418/Grail_Loudspeakers.htm

https://forum.audiogon.com/discussions/grail-t5-speakers

Oscillate · « **Reply #2 on:** 4 Jul 2018, 03:05 pm »

Two things that Danny did with his LGKs might be useful here...

1) Placing a top firing fullrange driver very close to the front firing fullrange to add ambience and output.
The response was particularly sensitive to placement (proximity) of the top foring full range driver.

2) Using a like just 1 resistor or 1 capacitor to shunt only the higher range frequencies to the second full
range driver, while the (first) full range driver played the full range.

Peter J · « **Reply #3 on:** 4 Jul 2018, 04:16 pm »

I'd be up for building a prototype or two, and perhaps drawing in SketchUp. Two constraints would be 1. I'm in Idaho which is a little ways from Texas 2. I may not be able to get to it straight away.

It might make a good teething project for big CNC router heading my way soon.

mlundy57 · « **Reply #4 on:** 4 Jul 2018, 04:36 pm »

Quote from: Peter J on 4 Jul 2018, 04:16 pm

It might make a good teething project for big CNC router heading my way soon.

That is also green with envy

Mike

Danny Richie · « **Reply #5 on:** 4 Jul 2018, 04:53 pm »

If you guys power the lower woofers with a separate plate amp, with a variable phase control, crossover, and gain, then it makes the whole thing really easy to pull off.

Also, adding another full range driver to the rear covering only high frequency ranges really makes an improvement in imaging and sound stage layering.

Basically a Skinny 6 design but with powered lower drivers....

http://gr-research.com/skinny6s.aspx

Folsom · « **Reply #6 on:** 4 Jul 2018, 05:26 pm »

The Grail probably has a dead spot in frequencies. At the crossover frequencies the woofers will be nearly beaming straight out. BUT it looks like it uses bipole so that's probably the magic people are finding, or at least in the bass and a different sound in the higher registers.

Peter I'm in Spokane so maybe I could come visit... We could do a bit of measuring.

Using a plate amp means it has to be mounted on the side. Not the most attractive, and I think the naturalness of the sound is better suited to people's regular amps... (largely because they'll be playing much higher than subs) But I don't see any reason why an optional GR-T3 rear mounted below the Ape vent couldn't be a decent option. Yet of coarse this can go any direction. I'm just going to argue for a nice speaker that is accessible for people that don't have impressive custom dedicated rooms and such, something that can be a bit more casual while still impressing anyone.

Danny Richie · « **Reply #7 on:** 4 Jul 2018, 05:55 pm »

I tried a side firing M-130 with the LGK driver. My issue with it was the phase relationship. It worked out really well when the side firing woofer was pushed forward of the LGK driver instead of behind it slightly with the centered side mounting. But I couldn't figure out a way to make it look right with the side firing woofer centered nearly 8" ahead of the LGK driver.

The other thing I realized was that the crossover parts for a really low crossover point made the values really big and in the end cost more than crossing the M-130 to a tweeter at 2kHz or so. And I felt like crossing the M-130 to a tweeter actually sounded better and had higher sensitivity.

The advantage of the Skinny 6 came from the thin baffle and next to nothing surface reflections. And with the rear mounted driver it really excelled in imaging and sound stage layering. And they sound big. They sound so big and layered that it is hard to believe they are so small. Also the more limited off axis response of the 3' driver make them more ideal for rooms with limited to no room treatment. I'm loving them in my small home theater system.

Folsom · « **Reply #8 on:** 4 Jul 2018, 06:58 pm »

Danny, what did you try to cross the LGK and M130 at?

There will be some big caps. I'll be spec'ing Solen caps bypassed by Sonicaps.

Some of the goals for this, that I've got in mind, are a bit different than the spatial ones.

Danny Richie · « **Reply #9 on:** 4 Jul 2018, 11:03 pm »

Quote from: Folsom on 4 Jul 2018, 06:58 pm

Danny, what did you try to cross the LGK and M130 at?

There will be some big caps. I'll be spec'ing Solen caps bypassed by Sonicaps.

Some of the goals for this, that I've got in mind, are a bit different than the spatial ones.

I tried crossing them close to 200Hz.

Folsom · « **Reply #10 on:** 4 Jul 2018, 11:59 pm »

Ah, that would be harder to get phase the lower you go if I am not mistaken. I suspect there is a possibility to raise the crossover point if phase remains a harder target.

I think it may be ok to settle on phase that maybe could be slightly better but sounds right. I tune subs by ear for phase.

If the phase remains tought I also suspect that moving the woofers down and reversing polairty might be an option. No doubt there may be some expermintation. It might work best to start with removable side panels.

jparkhur · « **Reply #11 on:** 5 Jul 2018, 12:22 am »

Ill continue the theme. Why don’t you put the 165 on front baffle and at a 45 like the v2 subs.

Folsom · « **Reply #12 on:** 5 Jul 2018, 12:32 am »

There's two 165's per box. They need to be polar opposite. So I cannot follow how that would work.

Jonathon Janusz · « **Reply #13 on:** 5 Jul 2018, 01:56 am »

I think(?) JP is suggesting to open baffle the pair of M165 to get a dipole radiation pattern if that is what you're after, in this case building the section with the M165 like the bigger V2 that has the 12" Eminence drivers.

I know it is going way of script, but would a pair (triple? quad?) of M165 in an angled open baffle to keep it narrow, with a LGK up top, forward firing and itself in an open baffle work? Would this basically be a tiny V2? [insert Dr. Evil voice] I will call it... Mini-V...

Danny Richie · « **Reply #14 on:** 5 Jul 2018, 02:10 am »

Actually keeping the phase right is easier the lower they cross.

Folsom · « **Reply #15 on:** 5 Jul 2018, 04:22 am »

Quote from: Jonathon Janusz on 5 Jul 2018, 01:56 am

I think(?) JP is suggesting to open baffle the pair of M165 to get a dipole radiation pattern if that is what you're after, in this case building the section with the M165 like the bigger V2 that has the 12" Eminence drivers.

I know it is going way of script, but would a pair (triple? quad?) of M165 in an angled open baffle to keep it narrow, with a LGK up top, forward firing and itself in an open baffle work? Would this basically be a tiny V2? [insert Dr. Evil voice] I will call it... Mini-V...

None of that is applicable, or desirable.

Dipole is not the intention. Bipole is the intention because of what it does for bass and box vibrations. Open baffle would have no bass, and require a lot more space to sound ok. And I don't think open baffle is as good as ape enclosures - at least inside a house.

Folsom · « **Reply #16 on:** 5 Jul 2018, 04:24 am »

Quote from: Danny Richie on 5 Jul 2018, 02:10 am

Actually keeping the phase right is easier the lower they cross.

I dunno, you were moving a driver 8" on top of some other distance with the m130. If the crossover was higher it would take less movement.... so I guess it depends on definition of easy?

Danny Richie · « **Reply #17 on:** 5 Jul 2018, 02:12 pm »

The lower wavelengths are longer. So the same amount of distance offset is less of a phase rotation than if the crossover point is higher.

And while bipole loading does cancel moving force, the box vibrations are still the same. Pressure changes in the box are still the same and side walls are excited exactly the same regardless of which way the woofers are facing.

Folsom · « **Reply #18 on:** 5 Jul 2018, 06:10 pm »

I think you should build a box and see how much less vibration there is... I've played with multiple bipoles.

Danny Richie · « **Reply #19 on:** 5 Jul 2018, 06:43 pm »

Quote from: Folsom on 5 Jul 2018, 06:10 pm

I think you should build a box and see how much less vibration there is... I've played with multiple bipoles.

I've built some on the past. The four sides flex or resonant based on bracing and wall thickness. And they are excited by pressure changes in the box. Whether the woofers are on the same side or apposing doesn't change anything. Positive and negative pressure changes are the same.