Port conversion

[Danzilla31]

... but if the slot port is big enough to overcome the efficacy issue?



RBH is limited by size to a degree and cost beyond all else. Needing a differently shaped cabinet gave me a shot at making a really inert cabinet which RBH can't do at this price point. I just wanted to change the port over because circles are more challenging than slots. Cutting lines is easier than making circles.

But watch what TLS does with his choices in an alignment based on those T/S parameters. If he reinvents this wheel, I'm building it. The other subs he designed for me are freakin' choice. I finally have the perfect placement for them. Even the girl has been won over by them in their current locations right beside the couch like end tables. We've had a variety of sub solutions for that room, including the RBH SEN 1010. Granted, each cabinet is just over 100 lbs. Whatever the reason ... nothing I've heard sounds like them.



It's not that important. I just wanted Mark to know that I wasn't likely to exceed the driver's power handling capabilities with the Rotel.



It has to be those trade offs Ryan and highfigh were talking about. There must be some sort of rules, if/then type things that make one or the other right in different applications. I haven't read all my books on speaker design yet ...



Primal scream
Who put sand in the Vaseline?

In general, talk of lube on the forum is codified to help members maintain relationships with real women.

That cabinet is getting heavy at 80 lbs without panels. If you look at it, it's 3 boxes shaped like a "U". The backs of the driver boxes add up to 16 more lbs. I can pop the panels from either side for now to cut holes, add bracing etc. The Formica-ed top and sides will get Cherry nosing with a front and back caps with some veneer if I ever dig it out of Eddie's garage.

My girl is about sick of it. Like she's good but I don't think she wants to know that TLS is actually Dr. Mark Carter and that he designs speakers when he's not saving Loons, you know? I was almost ready to tell her what TLS meant! Lucky for me, she had someplace else to be and saved me from regaling her with more of what she didn't want to know.

LMFAO Man every time I have friends or family that ask me about some audio project I'm doing or how'd I get that one room to sound so good they're eyes just glaze over about 30 seconds in. Too funny

 

[TLS Guy]

It was a pretty close call with the TDTOG thing looming. It took a little doing but I figured since you were asking it might behoove me to make that happen. I'll dig out the other driver for a comparison. Thanks.

Here's the other driver:

http://imgur.com/iuk9OUP

Pretty close, right? I figure their box was close to 3' cubed w/ that 3" wide fluted port of 6" length. I think their claimed F3 was 26 Hz. It seemed to be pretty heavily stuffed, not compressed but full.

It took like 20 tries before I was able to calibrate the leads and impedance. All set to 2 channel CD quality as suggested on PETT. I forgot most of what I knew when I tried using this thing before. My readings of a couple of pee-pee Infinity PS 10 sub drivers seemed so radically different that I couldn't be sure it wasn't operator error ... anyway, here we are again but this time I think I got it.

It wasn't all day spent on this but fo sho it was a good part of it. Thanks for the motivation. Now ... back to the cabinet.

The equivalent volume, Vas is missing. I absolutely have to have that number.

 

[Alex2507]

The equivalent volume, Vas is missing. I absolutely have to have that number.

1.748 cu ft

You know my brain hurts now.

I used a roll of blue tape (72 g) and got 1.59. Second try said add more weight so a roll of electrical tape (60 g) went in the middle of the blue tape for 132 g and 1.59 appeared again but after switching everything to 2 channel CD quality the number came back 1.748 twice so final answer: 1.748 cu ft. This is where I had trouble before ... past that too now ... probably.

The other driver was 1.6996 cu ft.

http://imgur.com/8CahAaW

http://imgur.com/1Dml6Yn

 

[Alex2507]

@TLS Guy

Using a 100g small steel weight one driver came in at 1.55 cu ft and the other at 1.62 cu ft.

Somewhere I read that the smaller the weight the better. I'm not sticking the weight down with blue tack ... I don't even think I have chewing gum. If I need to get some ... Parts Express? I read about rolls of tape being okay to use because of weight distribution and on my own thought to try the steel 100 g weight that came supplied with a small scale.

 

[TLS Guy]

@TLS Guy

Using a 100g small steel weight one driver came in at 1.55 cu ft and the other at 1.62 cu ft.

Somewhere I read that the smaller the weight the better. I'm not sticking the weight down with blue tack ... I don't even think I have chewing gum. If I need to get some ... Parts Express? I read about rolls of tape being okay to use because of weight distribution and on my own thought to try the steel 100 g weight that came supplied with a small scale.

Those numbers are close enough.

It seems you were wise to consider building a tunnel port. The port on the original box was inadequate.

I have done you two models. The first is the one I would recommend. The second extends the bass to what was specified in rbh literature, but with loss of power output and efficiency. Above all cone excursion is greatly increased which will increase distortion. The optimal box model will be the most musical.

Speaker companies get forced to use those extended bass models by marketers to be able to join the lowest F3 wars. However it is really not a good idea to use alignments the give an f3 below driver Fs. I do not favor them at all. I have posted about this often. This is one more reason to design and build your own speakers and not to have to answer to marketing types.

Peter Walker never had a marketing department while he was managing director, and was angry anytime it was suggested. As soon as he handed over the reigns, the first thing that occurred was the creation of a marketing department. They promptly ran the show into the ground and Chinese ownership. A massive disaster for the audio world.

 

[Alex2507]

Peter Walker

I was gonna throw Quad out as a guess and I would have nailed it too:

Peter J. Walker 1916–2003

I am saddened to report that Peter James Walker, the founder of quintessential English audio company Quad, passed away on December 10, after a long illness. He was 87. Peter Walker had been married twice; both his wives had died before him. He is survived by a daughter, Victoria, and a son...

www.stereophile.com

I have done you two models. The first is the one I would recommend.

Okay. Twenty inches of port ... coming right up.

Gotta do some math.

Thank you.

 

[Pogre]

I'm actually impressed with how deep the less optimal design digs for 10" woofers. I get that introduces more distortion, but still better than I expected. Even the optimal design looks pretty good.

 

[Alex2507]

I'm actually impressed with how deep the less optimal design digs for 10" woofers. I get that introduces more distortion, but still better than I expected. Even the optimal design looks pretty good.

It's also almost twice the size. There's something to be said for small packages. Especially when the package is already mostly built. Even so, It's sawzall time for real.

 

[ryanosaur]

It's also almost twice the size. There's something to be said for small packages.

Dude. C’mon. Too easy.

 

[TLS Guy]

I'm actually impressed with how deep the less optimal design digs for 10" woofers. I get that introduces more distortion, but still better than I expected. Even the optimal design looks pretty good.

Th problem is though, if you have done this before, you know that the sub with the lower F3 will in fact sound a lot worse than the optimal design. The marketers bank on the consumer not being able to realize that the F3 is only one parameter among many. The smaller enclosure will have tighter, crisper and more accurate bass, and has a good chance of producing realistic drum sounds. The larger enclosure will have that nasty all to common gooey bass that lacks definition.

Remember driver size does not determine F3. Other parameters especially fs and Qts are crucial. I use a total of four 10" drivers, two per side. Fs is 20 Hz. Yet they produce good deep bass in their lines which can easily vibrate your internal organs. At the same time, the bass is highly realistic and starts and stops when it should. Yet, I actually have to curb the speakers a little below 30 Hz because of room gain.

An f3 of 20 Hz or below does not equal a good sub: not by a long shot.

Bottom line is don't fixate on f3.

 

[Alex2507]

I actually have to curb the speakers a little below 30 Hz because of room gain.

The sound of your other DIY sub design improved once I dug 'em out of the corners in a 2 channel set up, presumably reducing room gain. KEW pointed me in that direction. Now they're in the living room HT, turned down a few db shy of the mains to help them blend from across a room and to overcome the end table type nearfield placement by the couch. Lovin' that.

I had to scamper to buy back some space to allow for the slot. It's close. What a pain. Careful what you wish for, right? My condo dweller status and this sub's main role being music reproduction lend themselves to an F3 of 33 Hz being alright. It's worth noting that the external RBH amp that came with the SEN 1010 (all used) was blown and the DATSV2 shows a -60 degree phase angle at ~35 Hz with 35 Ohms at the drivers. I know it's blurry but that's what that graph is, a few posts back. I'm happy to let these drivers do what they can do well and if that's all north of 30 Hz, fine. I kind of have an idea of what a decent alignment sounds like in a solid cabinet and these are the drivers on hand ... so, nuthin' to it but to do it.

 

[Alex2507]

Why did I think this would be no problem?
Like how would a thought like that ever happen?

Port pieces are cut up. Sawzall action taking place. Need to assemble port and install next. I mean it seems simple but in the end there is soooooo much to do ... even figuring out the sizes of wood to cut for the vent took like thought. Adding fractions; good thing for grade 3.

 

[Alex2507]

There it is, the mouth of the beast. 33 Hz of terror.

http://imgur.com/RuRGFe7

Had some stair tread that got used due to the built in bull nose. 1" oak too so kinda kool.

It's upside down here.

http://imgur.com/W4S0QXz

Still upside down but the back. I'm using the bottom and back as port walls.

http://imgur.com/H8uO833

Here's the back, right side up.

http://imgur.com/jSelODS

This is the last time. Like the Depeche Mode tune says, "never again you swore, the time before".

http://imgur.com/9RszyLO

 

[Alex2507]

Since I got this woofer tester up and running I got to wondering about these two dual voice coil Rockford Fosgate subs I picked up for $250 along with a humungoid single channel car amp.

The previous owner had one sub with the voice coils in series so that's how I ran the test but I don't know if the voice coils get run in parallel or maybe even individually. I was wondering if these are good for anything.

http://imgur.com/lzkhjpY

http://imgur.com/eLKzVGW

 

[TLS Guy]

Since I got this woofer tester up and running I got to wondering about these two dual voice coil Rockford Fosgate subs I picked up for $250 along with a humungoid single channel car amp.

The previous owner had one sub with the voice coils in series so that's how I ran the test but I don't know if the voice coils get run in parallel or maybe even individually. I was wondering if these are good for anything.

http://imgur.com/lzkhjpY

http://imgur.com/eLKzVGW

Those parameters are ideal for a horn loaded sub! It is a very low Qts driver. Although Fs is below 20, with reflex loading the low end I suspect will drop off lower than you might expect. That is why drivers like that are ideal for horns, as horn loading pulls up the early droop in the low end. It looks to me as if that driver is probably designed for instrument, theater or cinema applications.

 

[johnkmatthew90]

Following

 

[Alex2507]

Those parameters are ideal for a horn loaded sub! It is a very low Qts driver. Although Fs is below 20, with reflex loading the low end I suspect will drop off lower than you might expect. That is why drivers like that are ideal for horns, as horn loading pulls up the early droop in the low end. It looks to me as if that driver is probably designed for instrument, theater or cinema applications.

Did you mean the low end would drop off at a higher frequency?

So measuring the woofer with the voice coils wired in series is correct? Once I figure out a better way to store the files produced by the woofer tester I'll do one voice coil at a clip and check to see how the driver behaves with the coils wired in parallel. I might have to re-read the section on subs in the book I did understand just to get a basic grip on the options presented by these truly beastly drivers.

The story is that these drivers were a Rockford Fosgate prototype for car audio SPL competitions. The manufacturer notified the previous owner that they could handle watts measuring in the thousands. I had thought about the big Crown amp for these.

When I look at the 15" driver with the stacked magnets compared to the RBH 10", I'm actually more impressed that the little 10" can do anything meaningful, I mean it's tiny!

http://imgur.com/oFvIh3U

 

[highfigh]

@TLS Guy

Using a 100g small steel weight one driver came in at 1.55 cu ft and the other at 1.62 cu ft.

Somewhere I read that the smaller the weight the better. I'm not sticking the weight down with blue tack ... I don't even think I have chewing gum. If I need to get some ... Parts Express? I read about rolls of tape being okay to use because of weight distribution and on my own thought to try the steel 100 g weight that came supplied with a small scale.

The info for the WT3 I have showed that clay (like the kind used to seal gaps- any Ace Hardware should have it) should be used as the weight- it's not affected by magnets and it sticks to the cone well enough but won't damage it when removed. I would say the steel weight would skew the test because it's close enough to the magnet that it would be pulled downward.

 

[TLS Guy]

Did you mean the low end would drop off at a higher frequency?

So measuring the woofer with the voice coils wired in series is correct? Once I figure out a better way to store the files produced by the woofer tester I'll do one voice coil at a clip and check to see how the driver behaves with the coils wired in parallel. I might have to re-read the section on subs in the book I did understand just to get a basic grip on the options presented by these truly beastly drivers.

The story is that these drivers were a Rockford Fosgate prototype for car audio SPL competitions. The manufacturer notified the previous owner that they could handle watts measuring in the thousands. I had thought about the big Crown amp for these.

When I look at the 15" driver with the stacked magnets compared to the RBH 10", I'm actually more impressed that the little 10" can do anything meaningful, I mean it's tiny!

http://imgur.com/oFvIh3U

That would make sense. It is a "brute force" driver. So it is for sealed application with a very high F3 and equalized with humungous amounts of power. It would still be a good driver for a horn though I think.

 

[Alex2507]

The info for the WT3 I have showed that clay (like the kind used to seal gaps- any Ace Hardware should have it)

I'll get that and run the tests again. Thanks.

So it is for sealed application with a very high F3 and equalized with humungous amounts of power

But 2 drivers in one box means 1/4 of the power, right?

I'm going to ask you to help me figure out what to do with them, even if it's only for car audio, after I figure out a few things and get highfigh's clay recommendation to test against what I've done so far.

Rob (anunaki) pointed out that they might be one-note wonders.

I gotta go mess with routers and I gotta say, that's my least favorite tool. Anything spinning at 30,000 RPM is just wrong.