The AccuGroove Situation - I'd like an answer: Anyone else?

[Eric VB]

Pssst! Hey Dave. Look at my earlier post (#000007, or the 8th in this thread). I already did this analysis.

 

The problem with allowing the impedance of the drivers to vary is not so much that it introduces more variables, but that we only have two equations and one is non-linear. This makes for icky math.

[alexclaber]

Originally posted by Dave Sisk:

The problem is that you can't have 1.41 drivers.

 

So, I think it's theoretically possible have a switchable deal. It might end up being a ridiculous number of drivers. In practice, it could certainly be possible to find a driver with the right T/S parameters, then have the mfg build some with custom impedances.

With certain combinations of drivers and series/parallel wiring you could switch the impedance from 4 to 8 ohms. HOWEVER, in doing so you'll affect the power distribution between the drivers and thus both the tone and power handling. There is no way to get a cab to double or halve its nominal impedance through changing series/parallel wiring combinations without affecting the tone or power handling. Full stop (period).

 

The joy of modern bass amps is that they're very tolerant of impedance and will all drive lower than their rated impedance to deal with the sometimes nasty real world loads that bass cabs present, often going somewhat below their nominal impedance. And if they do get upset, which is less and less likely with the increasing headroom available, then they usually have decent protection circuitry to prevent damage.

 

Alex

[Gruuve]

LOL! RBG, I must have missed your earlier post. Should I venture to say that great minds (or would that be twisted minds?) think alike...

 

Well, at least we got pretty much the same answer.

[getz out]

Right.

 

I just don't expect this to be answered. It was interesting to see that Jim Bergantino commented on this topic on another forum, echoing Mr. Lewis' comments.

[Eric VB]

Originally posted by C.Alexander Claber:

With certain combinations of drivers and series/parallel wiring you could switch the impedance from 4 to 8 ohms. HOWEVER, in doing so you'll affect the power distribution between the drivers and thus both the tone and power handling. There is no way to get a cab to double or halve its nominal impedance through changing series/parallel wiring combinations without affecting the tone or power handling. Full stop (period).

True enough, although my 70 speaker design does just that, so let's say there's no practical way to do this?

 

Anyone have 70 identical 2.5-inch speakers I can borrow? [5.65 ohm each.] They should fit into a 3x3-foot cabinet frame.

 

BTW, thank you Mr. Claber for bringing this up. I honestly wouldn't have thought twice about "how do they do that?" and would have just taken such a claim for face value if it were not for you.

[Gruuve]

Originally posted by getz76:

I just don't expect this to be answered. It was interesting to see that Jim Bergantino commented on this topic on another forum, echoing Mr. Lewis' comments.

Actually, I think we will get an answer...just be a little patient.

 

Dave

[rumpelstiltskin.]

Originally posted by C.Alexander Claber:

Full stop (period).

you're so british. thank you for translating.

 

robb.

[alexclaber]

Originally posted by RicBassGuy:

True enough, although my 70 speaker design does just that, so let's say there's no practical way to do this?

Well, at your insistence that you've got the maths right, I decided to get involved in your sums, and indeed you have! Nice work - call Phil Jones and tell him to start working on a 70x5" cab!

 

Alex

[a boy named sue]

Originally posted by RicBassGuy:

Originally posted by C.Alexander Claber:

With certain combinations of drivers and series/parallel wiring you could switch the impedance from 4 to 8 ohms. HOWEVER, in doing so you'll affect the power distribution between the drivers and thus both the tone and power handling. There is no way to get a cab to double or halve its nominal impedance through changing series/parallel wiring combinations without affecting the tone or power handling. Full stop (period).

True enough, although my 70 speaker design does just that, so let's say there's no practical way to do this?

 

Anyone have 70 identical 2.5-inch speakers I can borrow? [5.65 ohm each.] They should fit into a 3x3-foot cabinet frame.

 

BTW, thank you Mr. Claber for bringing this up. I honestly wouldn't have thought twice about "how do they do that?" and would have just taken such a claim for face value if it were not for you.

You do have 3 surfaces of your cab to place speakers on without affecting stackability...heck we could just have 35 isobaric pairs 6x6 speaker pairs on the front with room for a logo!

 

And why not use different sized baffles inside the cab. as well? "these 20 speakers act as as a midrange..."

[tnb]

BenLoy said:

I'm stayin' way, way out of this one.

For the record, I have one of Andy's Acme cabinets and love it to death. It's been with me to hell and back and people always comment on how great it sounds.

I second that! HOWEVER, I am waiting to hear how this plays out. Like Maury said

They might be great speakers, and that is what one should buy based on; however, if the above is true, I would by reluctant to do business with a company that would employ such marketing tactics.

I am hoping for a peaceful and non-incriminating resolution to this issue.

[getz out]

Originally posted by tnb:

Like Maury said

Stop agreeing with me, Thomas. I can't be held accountable for you lack of judgment!

 

I also own an Acme and have dealt with Andy. I am happy with his product, partially because he advertising it very honestly. I know for a fact he has turned away more than one customer, recommending other cabinets, after they have described what they were looking for.

[tnb]

Hey, if my own judgement was worth a damn, I wouldn't need you fine ladies and "gentlemen".

[getz out]

This is from another forum. Earlier, Dave Funk accused the folks at Bass Player of being deaf. He also attacked Andy Lewis' product. Strange.

 

Comments from Dave Funk of Thunderfunk Amps

If you don't like the AccuSwitch, or think it's a fraud, then don't use it. AccuGroove didn't charge you extra for it. But you have to ask yourself. How could someone engineer the best sounding cab I've ever heard, make it light weight, make it durable, make it project properly, and then try to pull a "scam" on you? Especially a "scam" on someone who doesn't own one, or perhaps even seen or heard one? What would the purpose be? To get you to buy a great cab under false pretenses? They don't need to scam anyone. Top players are BUYING them.

 

Everyone here is focusing much to much on one small and trivial feature of a wonderful series of cabs. I'll even bet that if you want, you can get Mark to build you one WITHOUT the AccuSwitch if you feel that strongly about it.

 

Also, for arguments sake, let's say it's "only" a cap. Yes, that's still patentable.

 

And from a technical standpoint, let's say that the cap's only effect is to increase the impedance of the second woofer ONLY at low frequencies. Do you have a problem with that?

 

Let's take the cap out and just make it a switch that cuts the second 8-ohm woofer out of the circuit to set the cab at 8-ohms out of one woofer. Throw the switch to 4-ohms and the second woofer gets connected. Basically two 8-ohm cabs in one box. Is there a problem with that? Since the power bandwidth center is 300 hz (50% of the power is below 300, 50% above) I can accept cutting out the second woofer, leaving the mid and tweets connected, increasing the LOW FREQUENCY impedance, reducing the LOW FREQUENCY load, and thereby reducing the amount of LOW FREQUENCY current drawn from my amp. Since the amp is now putting out less power, we don't need the second woofer.

 

NOW, do all of this without affecting the tonality of the cab, the frequency of the crossovers (based on the load impedance), and you have some really trick engineering. The complaint? It's ONLY a cap. Sounds like someone is jealous they didn't do it first, or it's not fair BECAUSE it was so easy. But as I've explained, getting it to work and sound great isn't easy.

 

These "complaints" sound to me like someone's mad because they got TRICKED into thinking the cabs sound great. Much ado about nothing.

 

Now let me close by saying that we're all just guessing at how this works. We don't know how it works. And we don't have a "right" to know how it works. We probably have a right to know IF it works. But as I've heard, "I only believe half of what I read, and none of what I see." So if you read the BP review and only believe half of it, the question remains, "What half is correct?" That's for you to decide.

Response from Jim Bergantino of Bergantino Audio Systems

Dave,

 

Your post is as ignorant as it is laughable. To insult our intelligence by saying they didn't charge us for this "technoloogy", therefore why should we care, is outrageous! What about profits from the sales of these products based on these claims? If you want to do their "bidding" do it at your own peril, but your only kidding yourself. This is not a question of sonic qualities, this a pure question about technological claims - an impedance switch that doubles a 4 ohm cabinet's impedance into an 8 ohm cabinet, without effecting volume or tone. It's quite interesting, at least from my perspective, that you, as a supposidly technical member of this community, believe in this "technology", or at least are trying to explain it away, or justify it. You should also be called into question for your other post stating that because the editors at BP are pros, they must be deaf, and therefore insinuating any opinions formed by them are baseless.

 

Is a capacitor patentable? Possibly. But it would be a design patent with such a narrow scope that it wouldn't be worth the paper it's written on. In other words, they could file for a design patent and claim they are using a 1000uf cap in parallel with a 330uf cap such that when inserted in series with an 8ohm woofer in a 2 - 8 ohm woofer design, parallel configuration, it doubles the DC resistance of the cabinet. So what! If someone was dumb enough to want to implement this design, all they would have to do is, rather than pay Accugroove a royalty, just use say 6 - 220uf capacitors in parallel. End of story! Again this is all meaningless "babble". In fact, I'm waiting anxiously to see if their "cabinet within a cabinet" patent is approved. I'm just not sure what to do with all the "millions" of dollars in royalty money I've put aside from my HT322 and NV425 sales!

 

As for disconnecting the second woofer in the 8 ohm configuration, what do you do with all the extra cabinet volume that was put there for the second woofer, and how does it effect the first woofer? What about the fact that the disconnected 8 ohm woofer is going to act like some kind of passive radiator and completey screw up the tuning of the cabinet? And why would you want to eliminate one of the woofers in one cabinet just so you can lug another cabinet to the gig and use it? You shouldn't talk about things you don't understand. It only serves to confuse things even more, and distract from the issue at hand.

 

And finally Dave, let me say here that we DO know how it works (or doesn't work). There is no more guessing. It is only a capacitor. I'm an engineer, and like any engineer, I don't take things at face value. I do my own research and form an opinion based in fact, which is supported by the evidence. Your attacks on the messenger (BP) are common ploys used by "guilty" people.

[g.]

Regardless of the outcome (and conflicted camp viewpoints) engendered by the appearance of the Acmeswitch page, one thing remains: Accugroove has products that meet a need. There was a niche for small and large cabs that traded off size or low extension that were more efficent than Acmes - that also shared the wider, smoother polar response that cabs with dedicated midrange drivers can offer... Some people just like that character and the coverage it gives on stage better than what two-way and semi-crossovered two-way provides.

 

If more qualified people actually examine the Accuswitch and find out the truth (one way or another) and the proper actions taken, there will be less to be alarmed about for all but a few of us. Hopefully this will not discourage the recently accelerated pace of [relatively speaking] non-traditional R&D introduced into the bass playing marketplace.

 

Those without the technical background to understand the issue from that standpoint should at least appreciate that a level playing field for manufacturers is in the best interest of all. Hopefully this can finally be resolved without the loss of any people who have helped bring us more and better choices.

[g.]

I should again add that I think it would be real peachy if bass gear manufacturers could go the SR route and adhere to inustry standards for specs definition and testing as well, and perhaps give some thought to stating efficiency at frequencies that matter to bass players as well as well as marketing people. SR subwoofer manufactuers don't just state what their designs do on averaged freqs, or at whatever KHz the highest peak is at: they often actually give figures for at least one or two bands that matter for the application, and/or provide meaningful graphs.

 

But I expect it would shock many of us to find that any new graphs made to industry standards would not in the least resemble specs that were previously published in the Brave Old World ; }

[g.]

bumpy

[jeremy c]

I'm still surprised (and saddened) at the anger and insults (some mentioning names and some implying names) that are directed over the use of what might be a network of capacitors in one of the best sounding speaker cabinets available.

 

It seems to me that a builder (or politician or preacher or anyone for that matter) should talk more about what he does and will do and less about what someone else might be doing if he wants to gain my respect.

 

I'm not seeing any false claims in the advertising that others seem to see.

[alexclaber]

Originally posted by jeremy c:

I'm not seeing any false claims in the advertising that others seem to see.

To quote the BP ad:

 

"Introducing: AccuSwitch

 

4 to 8 Ohms Selectable Impedance Switch"

 

There's the false claim in the advertising - there is no change in impedance when you flick the switch - at least not one that happens in the audible frequency range!

 

So why are amps not blowing up when running two AccuGroove cabs in the 8 ohm setting (i.e. therefore in reality each cab is at 4 ohms and the total load is thus 2 ohms)? Because modern amps are pretty tolerant of impedances below their rated impedance and have effective protection against damage, and more importantly because any rig using two large AccuGroove cabs (i.e. Tri-210L, Whappo or Jr, BD sig) is going to be so damn efficient that the amp is going to be having a very easy time indeed, just cruising along putting out a fraction of its maximum power, therefore no issues with excessive current draw from the low impedance.

 

Jeremy, we all know AccuGroove make some of the best bass cabs ever, and I for one want them to continue advancing bass amplification technology and improving our collective live tone, but the AccuSwitch does not do what it claims.

 

If one of the longer established and less personal bass cab companies, particularly one like SWR or Eden that has been recently bought out, had been selling a cab that claimed to switch impedance and but then found by both BP magazine and a number of expert cab builder/designers to be selling a lie, I think we'd have seen an absolute uproar in the online bass world, and the decimation of their future business. As it is, AccuGroove's customers have been remarkably supportive despite the deception, which is testament to their otherwise excellent products and service.

 

I just hope AccuGroove got their sums wrong and honestly believed that the switch worked. Better to be naive than deceptive.

 

Alex

[getz out]

Jeremy,

 

In my person but not humble opinion, people like Andy Lewis and Jim Bergantino had three choices:

 

(1) Keep quiet

(2) Point out that their competitor is lying

(3) Put in a similar switch that really doesn't do anything.

 

If they did (1), they would be at a competitive disadvantage. Accugroove went to lengths to advertise this option.

 

If they did (2), the level the playing field. Seems like a good option.

 

(3) is an option if you don't mind lying.

 

What would you have done if it involved your livelihood?

 

Whether the deceptive advertising is due to dishonesty or neglect, it must be addressed by the manutfacturer, no?

[Gruuve]

Alex:

 

What exactly did BP mag say about the AccuSwitch? I don't recall seeing the review...

 

Dave

[g.]

J,

 

You seem to be missing what technical engineering type people including Jim and Andy have been saying. It's NOT about how good or bad Accugroove cabs themselves are - that has nothing to do with talk of the Accuswitch.

 

Also I think part of their impetus for speaking up is simply a return to the debate that first opened up when the Accuswitch was being touted on all forums and introduced to ad copy... and the rest comes from the difficulty any expert has to see bad science (that's actually not even that difficult to grasp) go unremarked. This kind of thing is basic physics and EE stuff, and no ALIEN SCIENCE yet has been known to circumvent it ; }

 

...I'm sure it bugs people who really know their stuff to see people thinking the laws of physics don't apply, or that many earlier debaters have not bothered to take earlier discussion and edumacate themselves about the principles enough to even be talking about it AGAIN from a clued-in perspective.

 

I mean, if science was so easily messed with, most people attempting to do something would all be tinkering with magic spell shortcuts and not bother with the work of education, learning theory, practice...

 

Jim has made some pretty good analogies for the non-technical like (I'm paraphrasing since I only skimmed): turning on a garden spigot and filling a bucket full in a given period - then emptying the bucket, then turning the spigot only HALF on and somehow filling the bucket in EXACTLY THE SAME TIME. Well, that's just not going to happen! (Unless you were aiming half of the stream elsewhere the first time, which would be wasting energy).

 

As I said a few posts above, regardless of the Accuswitch, Accugroove cabs themselves are an achievement. (I myself thought highly enough of the engineering/design to talk several ERB people into buying the first few to be ever sold [Greg Campbell got the earliest serial numbers])

[g.]

What exactly did BP mag say about the AccuSwitch? I don't recall seeing the review...

I didn't read it either, but those who did say that BP found that the Accuswitch impedance sweeps for either setting are identical.

[davio]

So that everybody's up to speed.

 

Taken from Bass Player Magazine November 2005 Soundroom pgs. 48-51:

 

THE SWITCH

 

Perhapse our test AccuGrooves' most notable feature is the "AccuSwitch," which purports to change the cabinets' nominal impedance from 4[Ohms] to 8[Ohms] with the flick of a switch. Though one would expect this to dramatically impact volume and tone, AccuGroove says "it changes the impedance from 8[Ohms] to 4[Ohms] while always maintaining the output of a 4[Ohm] load." The benefits of such flexibility for maximizing power and combining multi-speaker systems with amps that don't perform well below a 4[Ohm] load.

 

When I used the cabinets with a variety of heads, some of which are not recommended for sub-4[Ohm] operation, the AccuSwitch had no effect on tone or volume. The amps' response didn't seem to change with regard to switch positions. Flicking the switch had no discernable impact, even with the particularly load-sensitive amps. Using amps that aren't endorsed for sub-4[Ohm] use in a sub-4[Ohm] condition usually just makes them run hot--most will still function, it's just not a good long-term practice. The AccuGroove cabinets never triggered the load-sensitive amps' protective circuitry, but neither did conventional cabinets combined for a sub-4[Ohm] load.

 

An impedance plot satisfied my growing curiosity about the AccuSwitch. It measures a cabinet's impedance across the frequency spectrum and is the most accurate means of guaging total speaker load. It revealed no real difference between the 4[Ohm] and 8[Ohm] settings (there is a minute shift in the subsonic region, around 4-5Hz). According to the plot, the test AccuGrooves are 4[Ohm] cabinets, regardless of switch position. The cabinets' DC (direct current) resistance changes as the switch is flipped, but this isn't integral to audio, as speakers don't receive DC signal under normal conditions. Audio is an AC (alternating current) signal and thus minimally impacted by the AccuSwitch circuitry. An internal hunt revealed the circuit to be a stealthily epoxied black plastic box with infinite DC resistance and 1,410[micro]F of capacitors, suggesting it contained numerous capacitors wired in parallel. Benefits of the box include blocking harmful DC (capacitors don't let DC through) and filtering out ultra-low frequencies to help prevent cone crease, but it does not change the cabinet's impedance. [AccuGroove responds: "The AccuSwitch was designed to not change the sound when you flip the switch. Hundreds of our cabinets with the AccuSwitch have been in use on nearly every continent for almost two years. With every brand and model of amp on the market there have been no problems or complaints from players using at least one AccuSwitch-equipped cabinet in a multiple-cabinet system who could not use multiple cabinets before. We feel that Bass Player's results were inconlusive as the amps used in the test would not shut off with a 2[Ohm] load. Our satisfied customers are proof positive of the validity of our AccuSwitch's functionality."]

Sorry for the "[Ohms]" and "[micro]"...the board wouldn't translate the symbols so I had to make due.

[Bobby LowTones]

I didn't read the article but I presume we should

read [micro]F instead of [pico]F. Wasn't the symbol

a small stylized "u"?

[davio]

Doh!!! I knew something wasn't quite right. Problem remedied.

[Gruuve]

This really isn't looking so good for Mark and Accugroove. Sounds like BP's opinion is that the AccuSwitch is up there with health magnets and such, eh? Thanks for posting that article Davio...

 

Dave

[a boy named sue]

[AccuGroove responds: "The AccuSwitch was designed to not change the sound when you flip the switch. Hundreds of our cabinets with the AccuSwitch have been in use on nearly every continent for almost two years. With every brand and model of amp on the market there have been no problems or complaints from players using at least one AccuSwitch-equipped cabinet in a multiple-cabinet system who could not use multiple cabinets before. We feel that Bass Player's results were inconlusive as the amps used in the test would not shut off with a 2[Ohm] load. Our satisfied customers are proof positive of the validity of our AccuSwitch's functionality."]

 

If the the amps checked the impedance at DC to provide shut-off protection then the AccuSwitch would do exactly what it is designed for. However, the detailed sales literature (not necessarily the headline) should reflect how it works and why bypassing the protection circuits (if that is what is happening) is an OK thing to do, IMHO.

[g.]

Could you clarify/restate what you just said?

[getz out]

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[jeremy c]

I just got out my trusty Velleman multi-meter and ran tests on my AccuGroove 210L cab.

 

With the AccuSwitch in the 4 ohm position the meter said.....4 ohms.

 

With the switch in the 8 ohm position the meter said.....8 ohms.

 

The cabinet sounds the same at either switch position.

 

Did I miss something here?