Forum developed GR-R WAW speaker

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Danny Richie

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Re: Forum developed GR-R FAST speaker
« Reply #40 on: 6 Jul 2018, 07:05 pm »
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MDF’s only reall asset is that it is cheap. Cheap to buy, cheap to finish, cheap to work with.

And it's denser, less resonant, and more readily available.

Other than plywood being stiffer, making it better for braces, I so no other advantage. And stiff is easy to achieve with bracing.

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I can/have built subwoofers with 15mm ply and push-push drivers that do not have any resonance until the amplifier is well into clipping and it is WAY louder than it would ever be used… why go to more effort & expense to build something that may (or may not) work as well?

Some of us like to take things to another level. I for one can't go back to using un-controlled drivers for low bass response. It's hard to go back from servo control. And then using servo control in an open baffle is in a different league.

planet10

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Re: Forum developed GR-R FAST speaker
« Reply #41 on: 6 Jul 2018, 07:09 pm »
And it's denser, less resonant, and more readily available.

Dense is not an asset, less resonant is questionable, and the last is unfortunatly true for many (not here thou).

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Some of us like to take things to another level.

But if you get the same result with less effort, over the top is just stoking the ego.

Servo is certainly nice, but all the same issues are involved in the box design.

dave

Tyson

Re: Forum developed GR-R FAST speaker
« Reply #42 on: 6 Jul 2018, 07:12 pm »
I much prefer elegance of design over brute force. And if you can achieve the same result with less effort, why not.

dave

I agree with your first statement.  It's the second sentence I'd dispute. 

You act like you're the only one that has ever thought of a well braced cabinet.  You're not.  IMO, a well braced cabinet is the starting point for a design, not the ending point. 

I also tend to dislike push-pull subs from a sound quality standpoint.  Which is hard to measure but is easy to hear.  Just like going to the time/effort of building a box with differing mechanical resonance points won't measure much better but it will sound better. 

That's the whole point of DIY - to experiment.  Try something out.  Does it sound better?  Great!!  Does it sound the same (or worse)?  Well only a bit of time and some materials costs are lost. 

Folsom

Re: Forum developed GR-R FAST speaker
« Reply #43 on: 6 Jul 2018, 07:55 pm »
I suspect this project will be successful with any cabinet material. It's small, easy to brace, easy to line and stuff, and has cancellation properties.

But I will say I prefer nice plywood. MDF is easy but gross.

Folsom

Re: Forum developed GR-R FAST speaker
« Reply #44 on: 6 Jul 2018, 07:56 pm »
I also tend to dislike push-pull subs from a sound quality standpoint. 

Ah, Good, because they aren't part of this project.

planet10

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Re: Forum developed GR-R FAST speaker
« Reply #45 on: 6 Jul 2018, 08:12 pm »
I also tend to dislike push-pull subs from a sound quality standpoint.

Push-Push is not the same as push-pull. Push-pull cancels 2nd harmonics, probably enhances 3rd, and as has been pretty well established, the ear/brain prefers 2nd harmonics to be higher than 3rd, and everything that follows (hard to generate too many higher orders).

I am a big fan of push-push, it solves a lot of problems, push-pull not something i would build.

dave

Danny Richie

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Re: Forum developed GR-R FAST speaker
« Reply #46 on: 6 Jul 2018, 08:14 pm »
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Dense is not an asset, less resonant is questionable, and the last is unfortunatly true for many (not here thou).

I lively more resonant box is typically not desired.

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But if you get the same result with less effort, over the top is just stoking the ego.

Getting the same result is questionable. Sound quality in subs really revolves around a solid and non-resonant box regardless of configuration. And opposing drivers can have some advantages, but it doesn't solve all box design issues or exclude any considerations. A solid non-resonant box is still necessary.

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Servo is certainly nice, but all the same issues are involved in the box design.

Yes, just as I said above. The same issues exist with all configurations. But servo control is beyond nice. It is the pinnacle of low bass reproduction.   

planet10

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Re: Forum developed GR-R FAST speaker
« Reply #47 on: 6 Jul 2018, 08:31 pm »
I lively more resonant box is typically not desired.

True. But i am not building resonant boxes. Any potential resonances are pushed up high enuff that they never get excited, so the box does not resonate. The other option is to try to push potential resonances below the DUT’s bandwidth, but that isn’t going to happen in a subwoofer.

dave

Folsom

Re: Forum developed GR-R FAST speaker
« Reply #48 on: 6 Jul 2018, 08:49 pm »
ANYWAYS how about back to the speaker.

Dave, thoughts on crossover, with these drivers?

The LGK has a good Xmax, so it isn't really necessary to go over 200hz, but I suspect it'll be easier at 300-400hz. Is a low order on the LGK not advisable, with a steeper one on the woofers? Again I want to have a 3 way switch for the woofers for 0 -3 -6db, to adjust for room size.

The LGK will be bypassed by a 5uf 9ohm RC regardless of everything but my sims show that does nothing more than lower the highest registered slightly, which may make it a little more on-axis friendly anyways.

Tyson

Re: Forum developed GR-R FAST speaker
« Reply #49 on: 6 Jul 2018, 08:54 pm »
Push-Push is not the same as push-pull. Push-pull cancels 2nd harmonics, probably enhances 3rd, and as has been pretty well established, the ear/brain prefers 2nd harmonics to be higher than 3rd, and everything that follows (hard to generate too many higher orders).

I am a big fan of push-push, it solves a lot of problems, push-pull not something i would build.

dave

You are right, and I mis-typed.  I did mean push-push, not push-pull.  Push-push configurations just sound odd to me (although not as bad as push-pull configs).

Anyway, Folsom is right, we've gone way off topic from his thread.  Sorry man!

Folsom

Re: Forum developed GR-R FAST speaker
« Reply #50 on: 6 Jul 2018, 09:11 pm »
I think sometimes with push-push speakers people forget to do some room correction. That will definitely give it a lot of bass. When it comes to fullrange it's a different kind of sound. I don't think it's bad at all. In some ways it is nice because there isn't much of a sweet spot and toe-in and speaker placement doesn't change much of the sound so long as it isn't against the wall. But it is different. I don't think it's quiet as intimate with fullrange push-push.

Danny Richie

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Re: Forum developed GR-R WAW speaker
« Reply #51 on: 6 Jul 2018, 10:28 pm »
Folsom, you can use a first order high pass filter on the LGK with no issues.

And if you are wanting to make the low end variable keep in mind to never use a resistor inline with a low frequency driver.

Folsom

Re: Forum developed GR-R WAW speaker
« Reply #52 on: 6 Jul 2018, 11:12 pm »
I certainly wouldn't use a single series resistor that couldn't handle the load.

It does look like a high pass filter along with your baffle step filter (guessed values from pics) does create a little bit of a 4khz dip. It's not enough to be bad, and not nearly as bad as the ragged response of other fullrangers either.

Danny Richie

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Re: Forum developed GR-R WAW speaker
« Reply #53 on: 6 Jul 2018, 11:29 pm »
I certainly wouldn't use a single series resistor that couldn't handle the load.

Even if it is a bundle that can handle the load it's still never a good idea to do that. You'll be changing the damping and control of the driver. it will also be converting output to heat instead. There are better ways to vary the output. 

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It does look like a high pass filter along with your baffle step filter (guessed values from pics) does create a little bit of a 4khz dip. It's not enough to be bad, and not nearly as bad as the ragged response of other fullrangers either.

Where are you seeing that?

planet10

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Re: Forum developed GR-R FAST speaker
« Reply #54 on: 6 Jul 2018, 11:36 pm »
thoughts on crossover, with these drivers?

I have seen the midBass, but am not at all familiar with the FR.

At the frequencies involved going active makes things way easier… and depending on how you do it, could even be cheaper. The size of the passive parts is significant, and good ones are not cheap — ie in our A12pw/A7.3 MTM XO @ about 250 Hz, there are a couple 240 uF caps and some equally big chokes. Even the 450 Hz passive on Tysen V2 has a 240 uF cap.

We design to be able to use 1st order PLLXOs which have minimal parts cost and no electronic haze. Some HT receivers have built in XOs that use channels 6&7 to be able to bi-amp. Something like miniDSP has huge flexibility, but the analog sections in the cheapest ones may not be up to your standards and the best ones avoid ADC at the front end (but sort of restrict you to digital sources). Often people will use something like miniDSP to work out whta filter is best and then try to implement that pssively or in an anaog line-level XO (ie the modified FirstWatt B5 Nelson is working up for the Linkwitz LX-mini).

A PLLXO can be 2 Cs and an R, and if you want to minimize one of those Cs can be the input cap on the HF amp. A series R & shunt cap are the LP filter (one assummes when Danny says no series R in the LP he is talking about a passive XO). At least 1 amp (usually the LF amp) needs a gain control to set levels.

A passive XO is much harder, as one has to deal with the variable impedances of the drivers particularility down around their resonance frequency where the XO is being placed.

When choosing the XO frequency one has to take into account driver centre-to-centre and baffle step F3. Ideally one targets the XO at less than a quarter wavelength of the centre to centre, and within the range BS (F3) times (the range 0.707 to 1). No BS is then needed on the midTweeter.

As the XO approaches 200 Hz the greater is the need to go active.

Do you have a 2nd amp already?

dave

Folsom

Re: Forum developed GR-R WAW speaker
« Reply #55 on: 6 Jul 2018, 11:39 pm »
Even if it is a bundle that can handle the load it's still never a good idea to do that. You'll be changing the damping and control of the driver. it will also be converting output to heat instead. There are better ways to vary the output. 

Where are you seeing that?

Yes, I wouldn't do it to change the response in that way. HOWEVER if the speaker was made into a TL I'd use in series resistor to move the QES up a bit because TL lines don't like well damped woofers. It would be good it move it to .45-.55 range.

I use BoxSIM. I put the LGK in a baffle & box size approximate to what this would be with a smaller front on one side. Then I put in the BSC filter you have (approximate) and a 66uf cap to see how it would do. Phase is pretty good, impedance fine, but response does have bit of a dip at 4khz. I suspect that a 66uf cap inline with a 1mH~ inductor could be at 4khz, but I have not checked. The overall response is pretty good, if not maybe a touch lower than expected in the midrange region. How much attenuation did you shoot for to balance it?

Jonathon Janusz

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Re: Forum developed GR-R WAW speaker
« Reply #56 on: 6 Jul 2018, 11:40 pm »
Well, if the initial sketch is the basic design which we are allowed to work with...

I know the aperiodic venting will mess around with the "rules" regarding how big a box should be used and how it will be tuned, but if I'm remembering correctly from the last designs I heard from Danny that use a pair of M165 (or comparable) boxed (the x-static and the x-cs sealed, the x-mtm ported):

Isn't the box a little big to be ideal for a sealed box (where the aperiodic venting would allow one to "cheat" and make the box even smaller, which is more or less backwards from what we see here)?

Isn't the box significantly smaller than ideal if going ported (the x-mtm is a lot bigger than most realize until it is sitting in front of you, and even then I know from way back in the day that folks often struggled to get that speaker to play nice in the low end because of the amount of bass a pair of M165 ported could put out)?

All this is maybe to ask, would a pair of M130 be a better plan for the intended application?  They could be moved around the baffles more because they are smaller around, use a lot smaller optimum box no matter how you cut it (sealed or vented), and considering the LGK isn't super sensitive nor moves a lot of air, what one loses taking away the M165 seems to be suggested will be made up for with the strengths of the intended design (frequency extension through porting and output through using a pair of drivers) with the benefit of getting both speed and the ability to play better (relative quality versus quantity) higher up the frequency range if the goal is to basically use the LGK as a (sort of?) really low crossing tweeter?

To close, might I suggest checking out Santiago's prior threads showing his skinny-six builds for inspiration on how to build out the boxes for this project; his seemed an elegant and clever solution to beefing up the box (in this case for the woofers) without compromising the narrow baffle width for the LGK.

planet10

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Re: Forum developed GR-R WAW speaker
« Reply #57 on: 6 Jul 2018, 11:47 pm »
...and considering the LGK isn't super sensitive

reminds of a point i forgot to make. If one is going for a passive XO, the woofers need to be some 3-5dB greater sensitivity than the midTweeter. This allows for choice of XO such that the extra sensitivity gives the BSC needed. If you go active sensitivities are way less important.

dave

Folsom

Re: Forum developed GR-R WAW speaker
« Reply #58 on: 6 Jul 2018, 11:50 pm »
Dave, active will come second to passive is the plan. Any able to fiddle with a MiniDSP can cross them over themselves with little to no trouble.

240uf would be huge. I'm getting 66uf at 300hz as a workable figure. At 44" we're looking at 11" distance for a quarter. It looks like that might be a bit to close while using separate internal enclosures. Where as at 200hz and 16.5" should be pretty easy. The M165's would just be close to the top. The price of a Solen cap does jump a good amount to get there from 60uf to 100uf. (almost doubles the cap price,  but still not that bad)

Folsom

Re: Forum developed GR-R WAW speaker
« Reply #59 on: 6 Jul 2018, 11:58 pm »
Isn't the box a little big to be ideal for a sealed box (where the aperiodic venting would allow one to "cheat" and make the box even smaller, which is more or less backwards from what we see here)?

All this is maybe to ask, would a pair of M130 be a better plan for the intended application?  They could be moved around the baffles more because they are smaller around, use a lot smaller optimum box no matter how you cut it (sealed or vented), and considering the LGK isn't super sensitive nor moves a lot of air, what one loses taking away the M165 seems to be suggested will be made up for with the strengths of the intended design (frequency extension through porting and output through using a pair of drivers) with the benefit of getting both speed and the ability to play better (relative quality versus quantity) higher up the frequency range if the goal is to basically use the LGK as a (sort of?) really low crossing tweeter?

The vents really don't help you change the speaker box size. What it really does is changes the Q, in terms of measurements. You still need volume for output. While the vent maybe could allow a driver to play in a smaller box than usual, you still throw away bottom end as you shrink. The intention of them in this case is purely for the sound. Ported would work away from the sound intention. A TL technically could be used with an Ape vent and may be very pleasurable with one. I personally prefer a TL over a port, but the obvious work load is extensive to pull it off. In this case I think it'll just be sexy enough to have the Ape vent. Consider that the M165's won't have any baffle step loss, and they'll need to be brought down to the sensitivity of the LGK at 85db, and then will have a switch to lower them even farther because the straight forward no BSL may leave the bass too strong. The way crossovers work this should give very nice bass extension, lower than the regular bookshelves that are ported because you're huffing off sensitivity that will also flatten the response below the crossover.

The M130 cannot play nearly as low without a port. It also has a VAS difference that makes it more demanding on box size for low output.

reminds of a point i forgot to make. If one is going for a passive XO, the woofers need to be some 3-5dB greater sensitivity than the midTweeter. This allows for choice of XO such that the extra sensitivity gives the BSC needed. If you go active sensitivities are way less important.

dave

As Luck would have it the M165 is 89.9, and the LGK is really more like 85db.

You don't thhink the LGK needs any BSC at 200hz+ ?