AudioCircle
Industry Circles => GR Research => Topic started by: aceinc on 12 Feb 2017, 12:26 am
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I am just into building the GR-Research OB W-Frame subs.
I have a question regarding two measurements;
16.30" The closest I can come up to in SAE is 16-5/16".
15.55" The closest I come up with on SAE is 15-9/16".
Are these approximations going to affect putting everything together?
Also my assumption is I will need to receive the drivers to get the hole pattern correct for the "bolt holes" and drill the holes before I start putting everything together. Correct?
On the same topic Because I can get to both sides of the drivers, I should be able to user bolts, washers and lock washers instead of "T" nuts, which I seem to screw up at least one on every sub I've built. Is this the best way of mounting the drivers? Or should I fight with T-Nuts, or something else?
How difficult is it to mount these drivers and bolt them into place once this unit is all together? Anything I need to look out for like making sure the bolt pattern doesn't put a bolt in the top & bottom middle?
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Here is the mechanical drawing for the woofers, you can get the bot/screw apcing from that if yo ulike or you can wait until you have the woofers
http://gr-research.com/pdf/12in%20mechanical%20drawings.pdf
I've never seen / heard of anyone striping one of the screws into .75" or 1' baffles. . I'm sure you can use bolts/ washers, nuts, & locktight if you want but not necessary IMHO. If you look at peter's last build thread, he uses a cool technique to harden and then tap the material to accept machine screws http://www.audiocircle.com/index.php?topic=139529.0 , can't reacll what page it was .
You can install the woofers after assembly..... if you add an additonal brace in the "V" (large unbraced area)of the "W", yo uhave to watch where you postion it to be sure an leave yourself enough room to get the woofer in
jay
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These drivers do not use T-nuts for mounting. They mount using 8 hex head screws which come with them.
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I assumed he was going to change the screws to bolts/washers/t-nuts ... .
And be aware, the screws ARE in the box with the woofers, if you don't see them reach up under the magnet. Many of the ones we've received have had the little screw bag ripped and that's where the screws migrate to
jay
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Yeah, those hex head screws hold really well. No reason to over complicate things.
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So the drivers come with hex head "wood screws" do I need to drill pilot holes for these screws?
More importantly what are the SAE dimensions I referenced? My tape measure doesn't have tenths of an inch.
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My circle jig is graduated in 1/16" increments so I either use the exact dimension specified if it comes out to 1/16" or any multiple of 1/16". If the specified dimension works out to be between two 1/16" increments, I use the 1/16" increment above the specified dimension.
Yes, pilot holes are needed. I use a Vicks bit. This is a centering bit designed for drilling pilot holes for hinges. Personally I wait until i have the drivers in hand. That way I know the holes will line up.
Mike
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The drawings for the W-Frame sub do not show dimensions showing the distance from the front edge & rear edge of the cabinet to the baffle. Does it matter? Should they be the same, different, can one part be against the edge?
Because of my plans I would like to put the two pieces of the baffles that attach to the top & bottom of the cabinet as close to the edge of the cabinet as possible like the drawing below
(http://www.audiocircle.com/image.php?id=157755)
. Is that a problem?
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No problem on your baffle layout either.
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OK, I have the wood for the inner cabinet all cut, the woofer holes cut, and dry fitted one of the cabinets.
The next step is to buy the kits. Once I have a driver I can finish drilling the pilot holes and start assembly.
My additions to the standard design will be to add a second layer of 3/4" MDF to the top, bottom and sides. These pieces will extend 3/4" past the front & back, allowing for a frame to hold a grill cloth.
The inner cabinet will be screwed and glued. I am thinking of using the 45 degree pieces I cut off the baffles to brace where the baffles meet the top & bottom if the drivers will allow it.
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Pictures? Build threads need pictures ...
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Soon... Right now all I have is a pile of cut wood.
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OK, I have the wood for the inner cabinet all cut, the woofer holes cut, and dry fitted one of the cabinets.
The next step is to buy the kits. Once I have a driver I can finish drilling the pilot holes and start assembly.
My additions to the standard design will be to add a second layer of 3/4" MDF to the top, bottom and sides. These pieces will extend 3/4" past the front & back, allowing for a frame to hold a grill cloth.
The inner cabinet will be screwed and glued. I am thinking of using the 45 degree pieces I cut off the baffles to brace where the baffles meet the top & bottom if the drivers will allow it.
The place you want to install a brace is in the middle (top to bottom) of the two side panels , at their front edges (at the left hand side in your diagram). That will tie the two panels together at their least supported area, greatly reducing their ability to flex and resonate. A single length of dowel or block of wood will leave enough clearance for the two woofers to pass by on their way to being mounted on their baffles.
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this is crude but....
if this is your "w" , yo want a cross brace where the arrow is
^
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As mentioned, it will run from side panel to side panel
Just be sure you leave enough room to get the lowerwoofer in and not interfere with the back of the upper woofer
jay
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Does the crude image below look like what y'all are talking about?
(http://www.audiocircle.com/image.php?id=157801)
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Does the crude image below look like what y'all are talking about?
(http://www.audiocircle.com/image.php?id=157801)
Yep, that's it.
Mike
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Does the crude image below look like what y'all are talking about?
(http://www.audiocircle.com/image.php?id=157801)
As Mike just said, that's the spot. You can even run the brace from the front edge of the side panels towards the back of the cavity, where the two baffles meet, for more bracing. But you must then insure that there is still enough clearance to be able to get the woofers passed the brace and onto the baffles. Either way, a brace eliminates the one advantage the H-frame has over the W---structural stiffness.
On the other hand, some people claim, as Danny has mentioned a few times, that the W affords a benefit of it's own over the H, that of a slight reduction is harmonic distortion. It has to do with the opposing force-cancellation created by the arrangement of the woofers on the 90 degree baffle relationship. Over my head, technically! It's a very small advantage, nothing too important to sound quality as far as I know.
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By doubling all four walls to 1-1/2" of MDF should offer a fair amount of rigidity and mass to the enclosure.
If one wanted to be pedantic about structure at the expense of increasing the height by 3/4" and some additional complexity, one could put a shelf through the center front to back. The drivers would need to move towards the top & bottom for clearance as well.
(http://www.audiocircle.com/image.php?id=157810)
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That's an interesting idea Ace. I wonder if the full "shelf" brace would create a cavity resonance in each resulting chamber in the front of the W-frame. What's say, Danny?
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I'm sure Danny will have a better grip on the effects, but in my mind the size of each cavity would be small enough to have a resonant frequency above the range of the drivers.
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Uh maybe I am missing something but wont it be difficult to screw in the drivers? How would you get a tool in there to work?
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Don't make the brace any deeper than half of the depth of the V.
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Uh maybe I am missing something but wont it be difficult to screw in the drivers? How would you get a tool in there to work?
I used bolts and nuts in my W-frames, not screws. I don't trust MDF to hold under the weight of the woofer hanging almost upside down!
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Someone asked for pictures.
(http://www.audiocircle.com/image.php?id=158126)
Here are some of the pieces and a large woofer. Note the lines on the pieces I did that to make sure where everything went, and later used it for a screw pattern.
(http://www.audiocircle.com/image.php?id=158127)
Here is one inner cabinet put together with the paint I chose for the interior. A couple of things about the paint;
1) I chose the smooth as opposed to texture finish.
2) They couldn't make Black, so I got dark gray. I could probably have asked them to put more black tint in it, but it was Sunday at HD.
3) It is like painting with pudding.
4) It seems to fill well.
5) I have been painting with a brush, and then using a small roller to smooth it out.
(http://www.audiocircle.com/image.php?id=158128)
Here is the inside of the inner cabinet after one coat.
I messed up a few things on the other inner cabinet, and it needs some bondo work before painting. I'll post those later.
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Looks pretty good.
Ahhh Bondo and wood filler, what would we do without them :lol:
Mike
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I have the outer cabinets installed. Basically 3/4" MDF on top, bottom and sides.
I bought the wood, but decided against the center brace. My thought process was that with 1-1/2" of material on the sides of the cabinet there should be no resonance in the band pass. My very unscientific knuckle test seems to confirm this. Also when I only had the single side pieces, I wedged a piece of 1"x 4" in the area brace would go. When I did the knuckle rap test, it made no difference in the sound, which did seem like it would be in the band pass.
The next step is to get everything prepped for veneer. I will need to sand & fill a few areas to ensure everything is smooth.
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Today's questions are about veneering.
I have a 4'x8' sheet of red oak veneer (non paper back) and 25' of 7/8" iron on red oak banding.
Question 1, on this type cabinet does the banding go on 1st? My thought is yes, so that if the cabinet is dragged on carpet the banding doesn't snag and break off.
Question B, Should I try 45 degree corners on the banding, or butt joints?
Question 3, Does anyone live in South Florida that knows what they are doing and want some Fat Tire beer, in exchange for technical assistance?
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Well I did what I thought was best veneering wise. Mixed up a batch of stain that I likedpainted/rubbed in the stain, and shot it with a coat of satin polyurethane.
Maybe by next weekend, I will have the speakers mounted and everything all buttoned up.
Against Danny's recommendation, I will be mounting the amplifiers on the back of the cabinets. I have built "boxes" that has an open "back" (facing the driver) that will hang off two rails situated on the backs of the enclosures near the bottom.
The problem that was identified with mounting the amps to the cabinets is the vibration of the cabinet will interact with the amplifier. I also felt that blocking some of the air flow of the lower woofer would load the back of that woofer. However in this case aesthetics wins out over pure audiophile-ness. I will screw and not glue the rails, so if I change my mind I can remove the amp.
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Wiring finally
I am fittin' (as they down south) to install all the goodies in the cabinets. I realized that I haven't a clue how to wire everything up. Would someone point me to where I can finding the wiring diagram for a dual 12" A370 based W cabinet OB system.
Also any pointers on the best place to drill the hole for the wires to go through the baffle would be good as well.
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I "believe" the "W"and "H" frames (with drivers firing in opposite directions) will wire the same. Below is Danny's wiring for the "H" frame.
(http://www.audiocircle.com/image.php?id=147463)
Best,
Ed
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So if you want to make the drivers face the same way .....you only switch the driver wiring? or the driver and servo?
or what?
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So if you want to make the drivers face the same way .....you only switch the driver wiring? or the driver and servo?
or what?
Just a guess, but based on the wiring diagram, just the power leads, not the servo leads. My gut reaction is that switching the servo leads would cause some form of cancellation.
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If they face the same way then you have to flip the polarity on both the driver coils and sensing coils to common polarity.
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So in the drawing above, on the top driver only you would switch black & red on both sets of terminals, correct?
Or on the bottom driver only.
l like being wrong, it means I learned something. I am learning all the time.
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So in the drawing above, on the top driver only you would switch black & red on both sets of terminals, correct?
Only if you flip the top one around so that it too faces the other way.
Or on the bottom driver only.
l like being wrong, it means I learned something. I am learning all the time.
If you flip the bottom one then flip the polarity on it (both terminals).
Just make sure the driver coils are in parallel and the sensing coils are in series.
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Sorry, yes I was describing how to wire if the speakers were facing the same way.
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Easiest way to remember the wiring for these (H/W frames) is wire forward facing woofers in phase, rearward facing woofers out of phase. Driver coils are always in parallel, servo coils always in series
jay
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I have the drivers in one cabinet.
Two lessons learned (the hard way of course);
1) Drill the holes for the wires before painting.
2) Put the driver facing the bigger opening (the single opening) in before the driver facing one of the two smaller openings. This will make it easier to get to all of the screws.
A few questions;
What is the reasoning for facing the drivers in different directions in the "W" frame?
Is there a significant disadvantage to putting ball casters on these boxes? After putting the drivers in, these cabinets are darn heavy.
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They play the same either way you face them.
Careful of putting wheels on them. I know it makes them easy to roll around, but you really want them to not move when they are playing. The more solid the better.
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When you face the woofers all in one direction, a majority of th weight is on one side of the baffle and depending on the base you used, the offset can make the cabinet a bit more "tippy".
I have all the woofers facing forward in my slpped triples, the base is only extended by approx 2.75". If you push onthe cabinet, it tiltts easier towards the rear but it is not unstable. With duals in w-frames, I'd imagine it would be even less so, less weight and it's clsoer to the center of the cabinet.
I picked up some 8mm casters off ebay that I use in the shop for rolling cabinets around etc. Sometimes I'll use them in the room just for setting up but once I get stuff where I want it, it all gets spiked
Sort of goes against what I believe but at some point, I really want to try a pair of the Isostandsthe Corndog and a few others have talked about
jay
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My KEF 105.4s have the original MFR casters, and I appreciate them when moving them.
I have wood floors in the listening room, spikes are out. If I do ball casters I will put them in "cups" when I position them.
I have no base on the woofer cabinets (W frame), I did extend the outer cabinet by 3/4" front & back to handle a grill cloth, however.
BTW, I would post more pictures, but nobody even commented on my "large woofer" in the last pictures, so I assume no one cares.
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BTW, I would post more pictures, but nobody even commented on my "large woofer" in the last pictures, so I assume no one cares.
Not everyone that views the pictures make a comment. But a lot of people look and like to see build pics. So far 2,190 have viewed your thread.
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I've had a couple subwoofers (sub = smaller in this case, Basset hound & Basset/Begal mix) in my pics in the past.
It's always nice to see our supervisors, uhh furry friends in the shop. Unfortunately I quite frequently have to chase mine out because they are either right under my feet or between me and where I want to go (and with no inclination to move I might add).
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Ace, I doubt the lack of responses indicate a lack of caring...for sure that's not the case for me. I actually had to go back and see what the "big woofer" reference was!
Folks here (including me) like process photos. I like to think it helps to propel their own projects or perhaps spur imaginations.
Over the years, I've posted of many what I thought were clever comments on my build blogs that fell on deaf ears, or so it seemed. But I guess someone's looking in, as you've got a couple thousand views.
Remember that most of us here are introverted, basement-dwelling trolls!
Not all will get that reference, but it will be funny to some.
Oh, and nice dog.
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One question I have that I keep forgetting to ask is, "Has anyone else built the W frame version?"
I think I looked for a build thread earlier, but didn't find anything.
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One question I have that I keep forgetting to ask is, "Has anyone else built the W frame version?"
I think I looked for a build thread earlier, but didn't find anything.
Yes, a lot of people have.
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Is tinning the leads before putting them in the spring clips on the woofers the best approach to connecting the woofers?
If not what is the best way to connect the leads to the woofers?
Since I have chosen to mount the amplifier on the back of the cabinet (against sage advice) I notice that there is a close proximity between the magnet on the woofer and the torroidal transformer on the amplifier.
Will this be an issue?
If so what ameliorates this problem in traditional sealed cabinets?
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Is tinning the leads before putting them in the spring clips on the woofers the best approach to connecting the woofers?
If not what is the best way to connect the leads to the woofers?
Since I have chosen to mount the amplifier on the back of the cabinet (against sage advice) I notice that there is a close proximity between the magnet on the woofer and the torroidal transformer on the amplifier.
Will this be an issue?
If so what ameliorates this problem in traditional sealed cabinets?
I tin the leads of the wiring and slide them into the spring loaded clips on the woofers.
I don't know and can't say if or how much of a problem having the woofer magnet so close to the transformer will be. I try to avoid it.
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Our "woofer" likes to hang out in the shop as well, seems like it's a pretty common thing. She used to always sneak up behind me and lie just behind me feet.... not any more afte a few pileups she has learned that's not a good spot to lie :lol:
I had to look back too, sometimes we aren't really focused on the additonal things in a picture and totally miss them. what kind of b"big woofer' is that ?
jay
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It's a Gerbian Shepsky (German Shepherd/Siberian Husky mix).
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Well the good news I have built the amplifier boxes so they are detachable with 4 screws, so if it behaves badly I can detach them.
I should have these bad boys in my living room for testing before Monday. As I mentioned somewhere, initially I will stick a couple of KEF 101.2 bookshelf speakers on the top and tune the combination to play full range using speaker level in.
I haven't really looked at the one page documentation that came with the amps, but does it give a good definition of all the controls and how to use them?
My first step will be to use REW and a microphone to tune the woofer enclosures to the room, first one at a time, and then together to get the phase correct. Once that is complete I will connect the KEFs in parallel to the woofers and adjust the gain and crossover freq on the woofer to best match the KEFs.
The initial tuning will be done with line level in and actual "production" use will be speaker level in, will that cause any issues? If so, I could fire up and old Adcom GFA 555 II amp I have laying about and do everything using speaker level in. It will eventually be driven by Emotiva XPA-1 Gen 1 amps.
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Help
In one cabinet I have the amp in and everything wired up properly as far as I can tell. I have the volume tuned to Min.
If I switch the amp from off to "Auto" nothing happens even with a signal. If I move the switch to "On" I get a VERY LOUD sound. If I had to guess about 30 Hz almost sounds like a square wave. I have tried it twice turning the amp off within a second.
Is it possible to achieve this by wiring something wrong? Could I have the sensor coil wired incorrectly?
I have the other box ready to go in my garage, wired the same way. I'm afraid to try it.
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I had something similar happen awhile back and it turned out I had the servo coils wired incorrectly.
The servo coils are wired in series. If both drivers are hacing forward the positive (red) wire from the servo board (thinner wires attached to the little board that is attached to the main moard) is connected to the positive terminal of one driver. The negative terminal of that driver is connected to the positive terminal of the second driver. The negative terminal of the second driver is connected to the negative (black) wire of the amp's servo board.
Mike
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The drivers are facing in different directions.
The wiring looks like;
(http://www.audiocircle.com/image.php?id=160657)
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The red wire from the sensing coil should go to the first woofers positive unless it is facing the other direction.
The same goes for the driver coils.
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The drivers are facing in different directions.
The wiring looks like;
(http://www.audiocircle.com/image.php?id=160657)
How about the driver coils? The driver coils are in parallel. But the driver coil of the "reverse" woofer needs to be reversely connected. Please also show the driver coil side connection.
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I "believe" the "W"and "H" frames (with drivers firing in opposite directions) will wire the same. Below is Danny's wiring for the "H" frame.
(http://www.audiocircle.com/image.php?id=147463)
Best,
Ed
Danny, I was following this drawing, is it incorrect?
If you have a correct drawing for a W baffle with one speaker facing front and one facing back, can you point me to it, please.
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Danny, I was following this drawing, is it incorrect?
If you have a correct drawing for a W baffle with one speaker facing front and one facing back, can you point me to it, please.
The drawing is correct.
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Here is the full picture.
(http://www.audiocircle.com/image.php?id=160665)
There appears to be a minor difference between as built vs diagram supplied by ebag4. To correct I believe I need to switch the "power leads" on both speakers. Correct?
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On the top woofer you have common polarity on the driver coils (red to red and black to black).
But you have flipped the sensing coils. The sensing coil on the top woofer should also be red to red.
And that's if the top woofer is facing forward.
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Are you saying that all I need to do is reverse the sensing leads on the forward facing driver, which is "Speaker 1" in the drawing?
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Are you saying that all I need to do is reverse the sensing leads on the forward facing driver, which is "Speaker 1" in the drawing?
No, on both drivers.
You have red to red on the top woofers driver coils and black to black. But on the sensing coils you have them flipped.
You need to wire red to red on the top woofers sensing coils too. Then wire black to the black of the lower woofer (it's flipped) and then red back to the black wire of the amp.
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Well I'm finished round one, the woofer cabinets.
Here are a few pictures. I am currently using the KEF 101/2s that are on top to test them. The speakers I am aiming to replace are in the background (B&W 802 Matrix), these are awesome sounding speakers in their own right.
Here is a couple of shots of one of the woofer cabinets, the cloth under the woofer cabinets is to protect from scratching until I get the feet built.
(http://www.audiocircle.com/image.php?id=160690)
(http://www.audiocircle.com/image.php?id=160692)
Here are the speakers as I am currently testing them, the towels are to keep the KEFs from sliding off, which one almost did playing some classical heavy on the Tymapnis.
(http://www.audiocircle.com/image.php?id=160700)
(http://www.audiocircle.com/image.php?id=160694)
Here is the test rig, an Emotiva UMC 1 for pre-amp, an Adcom GFA 555 II for power and a Yamaha DVD player.
(http://www.audiocircle.com/image.php?id=160704)
Now I need to finish the upper cabinets. These will be a an open baffle of my own design (I use the term "design" loosely) using 2 - 8" mid-woofers and a B&G Neo 8 clone for each one.
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BTW, the second cabinet I had wired correctly. The first cabinet I had wired the woofer power incorrectly as the wiring diagram I provided shows. I rewired the woofers in the first cabinet to match the wiring diagram provided by Ed and everything was wonderful.
That is one nasty noise you get when wired incorrectly.
Lesson learned, triple check your wiring before turning anything on.
When I received the amplifiers, all of the documentation included referenced "Sealed Enclosure." How can I tell if an amplifier is properly tweaked for open baffle?
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When I received the amplifiers, all of the documentation included referenced "Sealed Enclosure." How can I tell if an amplifier is properly tweaked for open baffle?
The quick guide that goes out with each amp is the same for all amps. The shelving circuit is added to all amps going out that are used with the open baffle drivers.
Send me a picture of the back of the amp and I can confirm the circuit has been added.
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Now I need to finish the upper cabinets. These will be a an open baffle of my own design (I use the term "design" loosely) using 2 - 8" mid-woofers and a B&G Neo 8 clone for each one.
That will require a fairly complex crossover and baffle design to make that work. Let me know if you need assistance with it.
Keep in mind that the height of the Neo 8 (or clone) is too tall to use as a stand alone tweeter. So it will have very limited vertical off axis. The highs will fall right out if you get just above or below on axis.
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The feedback connection does matter. If the polarity is incorrect, the negative feedback will become positive feedback.
Put a 20 ohm/5W or 10W resistor in-line in the driver coil can reduce the oscillation noise in case of incorrect wiring.
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Danny, it will take a bit of unscrewing to get one of the amplifiers off the cabinet.
I will try to get to it in the next day or so.
Another lesson learned;
Follow the instructions for pre-drilling the holes for the amplifier. I did not drill the holes deep enough and sheared the heads off 6 screws (I don't learn quickly). Also set the tension on your drill/screw gun to a low number (I finally set mine to 3) to protect against shearing heads off.
One thing I would like added to the "kit" for a dual driver system. Extra wire and 4 (2 each size) male spade connectors. I think about 2-3' of each gauge wire would be great. For me it would have made things neater.
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One thing I would like added to the "kit" for a dual driver system. Extra wire and 4 (2 each size) male spade connectors. I think about 2-3' of each gauge wire would be great. For me it would have made things neater.
When you place an order for this stuff by phone I ask if you'd like the four pole SpeakOn connectors with them. That's what we use for connecting them.
I take it that the placement of your amp at the back of the box was just for the picture? It needs to be away from the back of the woofer when playing.
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Danny, no I have the amp mounted just like you see it.
What artifacts should I look/listen for with the amplifiers mounted this way?
Are there any other problems I should know about?
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Danny, no I have the amp mounted just like you see it.
What artifacts should I look/listen for with the amplifiers mounted this way?
Are there any other problems I should know about?
You can't leave it there like that. You are blocking the rear output of the driver and changing the way the driver is loaded.
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Yes, I understand that restricting the air flow will change the loading of the driver. A couple of things;
I believe that even with the amplifier in its current position the open area that would allow air to escape is at least the surface area of the 12" driver. I will confirm that when I get home.
When playing the speakers as currently configured in my room, things sound pretty good.
I thought about moving the amplifier up so that it is centered vertically loading both drivers more or less equally.
For aesthetic reasons, I am not willing to have a separate amplifier box.
The difference between a mathematician and someone that is not;
The mathematician is put in a chair in a large empty room and a beautiful naked woman is placed on a bed at the other end of the room.
The psychologist explains, "You are to remain in your chair. Every five minutes, I will move your chair to a position halfway between its current location and the woman on the bed." The mathematician looks at the psychologist in disgust. "What? I'm not going to go through this. You know I'll never reach the bed!" And he gets up and storms out. The psychologist makes a note on his clipboard and ushers the engineer in.
He explains the situation, and the engineer's eyes light up and he starts drooling. The psychologist is a bit confused. "Don't you realize that you'll never reach her?"
The engineer smiles and replied, "Of course! But in less than half an hour, I'll be close enough for all practical purposes!"
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That's a funny analogy.
Seriously though, that is restricting way to much air. The lower woofer will act as if it is in a small vented box. So it will cause it to be loaded much differently than the other one and the sensing system needs for them to be the same so that it can make corrections that accurately effect both speakers.
Loaded this way, neither of them play the same.
And it will cause an uneven response.
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deleted
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For aesthetic reasons, I am not willing to have a separate amplifier box.
All this trouble to build this excellent dipole woofer system, and aesthetics are ruling/ruining the day???
Since you already have a separate amplifier box, I suggest to disconnect it and lay it on its back behind the woofers. It should not be visible that way and won't unduly effect the symmetrical operation of the woofer radiation.
This also has the benefit of not physically mounting the amplifier to the woofer enclosure. Long term, that might have some positive effect on the longevity of the amplifier by reducing vibrations.
Dave.
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I agree with Dave today.
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OK, when I have completed my feet, which should be shortly, I will move the amplifier up to the middle of the cabinet, that should make the loading be the same on both drivers.
Based on my calculations the cabinet with no obstructions has an opening of 286 square inches. The piston area of both drivers is 152 square inches. The amplifier box covers about 130 square inches. 286 - 130 = 156 square inches of "covered space." Based on my limited understanding if the amplifier is moved to the middle it should cause little if any loading on the woofers.
Another little note about the my build. I built the cabinet based on the design on your site as accurately as my limited woodworking skills allows. I then wrapped that cabinet in a second cabinet that extends beyond by 3/4" on the front & back. The amplifier braces are attached to the outside edge of the original cabinet with 3/4" (1x2) oak, so the box that the amplifier is in is actually 3/4" behind the rear opening of the original cabinet. The point I am making is that the calculations above are more conservative than the reality.
Irrespective of all of this, in its current configuration with the KEFs as mid/tweeters, I happily listened to all of my test recordings as well as some new fun stuff, and am pleased with the results.
The first thing I test with is a Sheffield Drum CD, then I play a cut off a Hybrid CD called "Alone Together" which is female vocal with acoustic bass to verify that the bass sound is well defined through various frequencies. Then I fire up 3 O'clock blues from the "Riding with the King" CD. For fun I played some CDs I picked up at a garage sale called "Classical Thunder I & II."
I will A/B them against the B&W 802s soon.
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Davey A few things;
I have a wife.
I do not consider myself an audiophile, but a person with an audio hobby, so aesthetics have a level of importance to me as well.
My hobby is full of trade offs, in this build for example I am using speaker level inputs for these cabinets and I am making feet that will not be attached to the cabinet so that if I decide to rotate the cabinet on its side, I can.
I will not be hammering these speakers often, so hopefully any cold solder joints will show themselves during my initial testing.
If I cannot keep the amplifiers mounted, then I made a costly mistake, because that is where they will stay, or I will sell them and recoup some of my loss.
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Based on my calculations the cabinet with no obstructions has an opening of 286 square inches. The piston area of both drivers is 152 square inches. The amplifier box covers about 130 square inches. 286 - 130 = 156 square inches of "covered space." Based on my limited understanding if the amplifier is moved to the middle it should cause little if any loading on the woofers.
Actually just extending the sides by an inch or so changes the loading on the drivers. Blocking that much of the back of the cabinet will change the loading on the drivers significantly.
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Danny, Were I closer I would bring them over so you could run tests on them. We could then see the impact that my foolishness has wrought.
Regarding the extra 3/4" in deciding the load it would present to the drivers, since it is also 3/4" out (from the center) I think it would act like a very short 45 degree horn. If that has an audible affect (on frequencies in the band pass), I would be very surprised.
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You can always look at it like this, if you like what you hear go for it. If at some point in the future you want to see what difference opening the back up makes, you can take the amps off and set them on the floor behind the cabinet for an experiment. This may be easier to accomplish when your wife is going to be away for the day. :green:
Then if you can't tell any difference, put the amps back on the cabinet. If you can tell a difference and like the sound better with the back of the cabinets open, then it may be time to look for a solution that will let you keep the backs open and be acceptable with your wife.
Mike
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Danny, Were I closer I would bring them over so you could run tests on them. We could then see the impact that my foolishness has wrought.
While it is playing try moving it away. You are blocking about a 1/3rd of the air space on the back side with the amp. And it is also effecting the output on the front side.
Regarding the extra 3/4" in deciding the load it would present to the drivers, since it is also 3/4" out (from the center) I think it would act like a very short 45 degree horn. If that has an audible affect (on frequencies in the band pass), I would be very surprised.
Try moving it away.
Just laying it flat on its back behind the woofers takes up very little floor space and would hardly be seen.
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If I cannot keep the amplifiers mounted, then I made a costly mistake, because that is where they will stay, or I will sell them and recoup some of my loss.
You're being given exceptional advice, and if you're not going to be receptive, then you should recoup your losses, and consider a more aesthetically pleasing option.
I'm not trying to give you a hard time, but I made a similar mistake when I built my W-frame. I made my own design changes, listened to Danny's advice, and to make a long story short -- I eventually bought a flat pack built to spec and it sounded much better. I also thought my wife would have an issue with the aesthetics, but once she sat down and listened to her favorite music, she was hooked and never had an issue from that point. In fact, she encouraged me to buy another OB sub! And I happily obliged.
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You're being given exceptional advice, and if you're not going to be receptive, then you should recoup your losses, and consider a more aesthetically pleasing option.
I'm not trying to hassle either but, IIRC, this was all discussed before you started this build. Many of us suggested that it was not a great idea to put the amp boxes onthe cabientss, you chose to to do so and tha's fine but it now is what it is.
I'd do what Mike suggested, go with it .... but, at least try and center the amps so that each driver is loaded the same, mkae the most of what you've got going. If at some point you chose to try it without the amps mounted, great .
The bottom line is everyone wants you to get the most out of your new subs , people are passionate !
jay
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As I previously mentioned, I like the way they sound as is, but I can see moving the amplifiers up.
Having said that, I did run sweeps using REW, and an uncalibrated microphone on one, then the other then both subs. Things looked fair, considering I was using an uncalibrated mic and it was an in room measurement. There was a low peak (30ish Hz) & a high peak (60ish Hz), I used the built in parametric EQ to tame the 60hz peak.
The one thing I have not seen in this discussion is a quantitative or qualitative definition of what I could expect to see or hear by making the changes I made. If someone were to say, "By loading one of the woofers you will see a peak at 40hz." or "By changing the cabinet adding 3/4" of an inch the bass will sound muddy.", it would make understanding the issues/concerns easier. Without this sort of input, how am I supposed to assess whether the changes I have made make a noticeable difference? Wiring them wrong sure made a difference :duh:
When I was young and went to church, I was a PITA to my Sunday School teachers, cause I would challenge everything. "Why can't we go to the movies? They show movies on TV." "Who created God?" :icon_twisted:
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Heck for all I know, my changes may have improved everything, and everyone else should jump on the bandwagon. :lol:
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Mine are laying on the floor behind my cabinets and you can't even see them.
(http://i576.photobucket.com/albums/ss207/corndog642/2017%20Mancave/D2454E06-EA0E-43F1-AEAA-CD28D4A36768_zpsmdbtkumv.jpg)
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Part of my reasoning is functionality, I move my speakers testing and playing with stuff regularly. Having a separate box means more stuff I need to move, keep track of cables, etc.
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Corndog, I bet you have the rumble filter turned on when playing albums.
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Here's a silly question - since you already have the amp boxes built, and you'll be placing some sort of satellites on the top of the woofer box, why not just stand the amps up on the woofer box and let them act as backstops for the satellites. That should cause far less sonic "damage".
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Initially I had the amps up against the inner side of the sub cabinet so I could have easy access to the controls. It took a bit of experimenting to get them to sound right. Once I got that all figured out I didn't need to access them anymore so I laid them down and moved them behind the sub. I would think screwing them onto the back would be more of a PITA.
When it comes to Danny's designs he figures most of it out so all you need to do is build a cabinet to his specs, finish it however you like and enjoy. Others have tried to improve on his stuff but only end up compromising the sound quality. I've seen many other speaker designers do it differently (and cut lots of corners to make them cheaper) but Danny is all about providing the best sound for the money.
I do have the rumble filter on.
I suppose I should also add that I'm not married but I do have a very understanding girlfriend.
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Bob, I am building an open baffle "enclosure" for the mids & tweets. I have thought about mounting the amp back there as well.
Of course I have the same poorly defined problem there of changing the loading on one of the midbass speakers. I say "poorly defined problem," because I haven't heard what kind of issues doing this will cause from a sonic point of view.
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Corndog (Rob?), I am not trying to improve on Danny's design from a sound point of view. I look at it as tweaking it to fit in my lifestyle.
Some (many?) people buy/build Danny's design to get incredible audio at a liveable price point. They are looking to get the best sound they possibly can. If I get 90-95% of that great sound, but I have something that meets my lifestyle and has my personal touches, that is why I am into this "hobby."
If I challenge people to think, "What actually will happen if I mount the amplifier on the back of the cabinet?" Instead of just saying "Everyone says it is bad it must be bad.", is that a bad thing?
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Corndog (Rob?), I am not trying to improve on Danny's design from a sound point of view. I look at it as tweaking it to fit in my lifestyle.
Some (many?) people buy/build Danny's design to get incredible audio at a liveable price point. They are looking to get the best sound they possibly can. If I get 90-95% of that great sound, but I have something that meets my lifestyle and has my personal touches, that is why I am into this "hobby."
If I challenge people to think, "What actually will happen if I mount the amplifier on the back of the cabinet?" Instead of just saying "Everyone says it is bad it must be bad.", is that a bad thing?
Well, they are "open baffle" by design. Perhaps you would've been better off choosing a sealed sub which you can still build with those drivers and amps.
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Nothing I am doing is changing them from open baffle. I am restricting the airflow some from one side, I don't see what all the hubbub is about. You'd think I was personally kicking someone's dog.
I already have a 15" Rythmik Audio sealed servo sub I built years ago. As well as a pair of sealed 10" subs, non-servo.
I also built a Danley Sound Labs TH-Spud clone once just to see what it would sound like, It was impressive, you wouldn't believe how much bass you can get out of two 8" speakers.
I think tonight I will try some hip hop or dub step, just for fun. I recently picked up a country hip hop CD (Jawga Boyz) for free at a garage sale, maybe I'll give that a spin to test the bass;
https://www.youtube.com/watch?v=ADC_6XFvIxk
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It's your stuff. Do what you want with it. I'm sure you realize by now that the designer has tested extensively to find the optimum enclosure. You vary from that as you need to fit your parameters and live with the results.
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If I challenge people to think, "What actually will happen if I mount the amplifier on the back of the cabinet?" Instead of just saying "Everyone says it is bad it must be bad.", is that a bad thing?
Yes.
Don't try to convince us that what you're doing is OK. It makes no sense at all to spend all of that time and money, presumably to get the best sound possible, then screw up the sound by being incredibly obstinate with such a minor issue as placement of amps behind the speakers where no one will see them.
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One of the big issues with open baffle is having enough distance between the driver and front wall (reflection point behind the driver) to achieve at least a 6ms delay between the direct radiated and reflected waves reaching your ears. If there is enough separation, the reflected wave adds an expansive aspect to the sound. The closer the speakers are to the front wall the smaller and more constrained the soundstage will become. If they are close enough so the delay will be too short for the brain to perceive the waves as two separate sounds the music will start becoming muddy and smeared.
This goes for all open baffle arrangements, mids and tweeter as well as bass. So blocking the back of the cabinets could have the same result as placing them too close to the wall. Only listening to both configurations will answer the question for you.
Mike
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Early, it is my money and my time. I am not trying to convince anyone to do anything my way. I am interested as I stated earlier in what artifacts or anomalies I can expect by deviating from the norm. If I know what I might expect, I will look & listen for them.
But if all I see is folks saying this shouldn't be done because it may cause premature amp failure, or the loading of the drivers will cause some indeterminate audible anomaly, why should I not do what I want? The worst that could happen is I find why putting the amps on the back is a bad move. I then share that information, and idiots like me in the future will have concrete ideas as to what to expect should they try this. The best I can hope for is that it has little or no impact, and then it gives options to folks that read my posts.
Mike, I may be way off base here but at the wave lengths that we are talking about when dealing with < 100 Hz, having something that close blocking part of the opening would have little impact.
Sometime real soon I will pull the amps off, which I need to do to move them up to the middle anyway. When I do I will run an REW analysis with them off. I will then put the amps in the middle, and run the same analysis. Will this make everyone happy? Beware I am using the USB microphone from the Emotiva XMC-1 because my notebook does not have a microphone in jack. If someone has a calibration file for that microphone I would love to have it. I will be taking the measurements from my listening position about 12-13' from the speakers and will do 0-200 hz.
If anyone is in SE Florida and wants to join in the fun, PM me.
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Danny, if you want to pop in with your test equipment, I would be happy to put you and your family up at my bungalow.
While this offer is genuine, I doubt that you will take me up on it, but if you have some tests you would like for me to do, let me know, and if I can do them I will try.
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Okay, I am going to respond to these statements.
The one thing I have not seen in this discussion is a quantitative or qualitative definition of what I could expect to see or hear by making the changes I made.
I haven't heard what kind of issues doing this will cause from a sonic point of view.
I am interested as I stated earlier in what artifacts or anomalies I can expect by deviating from the norm. If I know what I might expect, I will look & listen for them.
The only way anyone can answer this is to replicate what you have done and then measure and test it to give you the objective results. This isn't possible.
You are going to have to be the one to determine the effect. And that is only going to happen when you take the time to make comparisons yourself.
Mike, I may be way off base here but at the wave lengths that we are talking about when dealing with < 100 Hz, having something that close blocking part of the opening would have little impact.
No, you are blocking about 3/4's of the area behind the woofer. It will not have "little impact". That is significant.
Nothing I am doing is changing them from open baffle. I am restricting the airflow some from one side, I don't see what all the hubbub is about.
No you are changing them from being a true open baffle to semi open baffle/semi vented box design.
You are changing radiation patterns, driver loading, how the servo system sees and controls the drivers, linearity of output, box pressures, output levels, etc.
Sometime real soon I will pull the amps off, which I need to do to move them up to the middle anyway. When I do I will run an REW analysis with them off. I will then put the amps in the middle, and run the same analysis. Will this make everyone happy?
I think there are a lot of good people here doing their best to try to help you so that you will be happy.
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Danny, I am willing to test with my limited test equipment the effect of having the amplifier in the middle of the two woofers to visually see the changes. I am willing to provide the results to the group, and I will do so.
Do you have anything that you would like me to test that I can easily accomplish?
I am willing to acquire additional equipment (within reason), if you are willing to guide me through the use of the new equipment.
In my career, I have been successful partly because I do not accept "...because that's the way it is..." types of answers. Since I am trying to do something that no one else has tried, I am willing to take the responsibility to determine what effect it has. All I ask is that people are open minded and try to help, not closed minded and shut down discussion.
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You don't need a bunch of test equipment. You don't need to try and measure the frequency response either. That won't even allow you to really determine the differences of various combinations.
Measuring the frequency response in the room tells you an average of on axis response, first reflections, second reflections, third reflections, fourth reflections.... and at one given point in space. And all of that will change if you move your mic one way or another.
It will be further compounded when you try to measure both speakers playing at the same time. When measuring a room response you never measure the output of both speakers at the same time.
All you need to do aceinc, is listen. Listen to it anyway you want. And listen to it with the amp away from the back of the woofers. Go with what sounds best to you.
And the good folks here are not close minded or trying to shut down the discussion. Some of these guys are expert level hobbyist. And I am a professional in this field. We know that it will have an significant impact.
I can run an impedance sweep with and without the amp in place and it will clearly show a significant difference. And the impedance sweep is made with very low level signals. The woofer will barely move and the impedance curve will still show a significant difference in how the driver is loaded. Just imagine what the difference would be when playing it hard.
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Our nearly universal advice is: Listen to the designer!
...or just do you own thing. Seriously, hope it works for you. The servo bass system is amazingly good, probably even when not well implemented.
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Why limit your measurements to the woofer? You should also measure the effect of hanging the amps a few inches in front of the tweeters and midrange.
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I'd like to help out this discussion in a more pictorial manner:
(http://www.audiocircle.com/image.php?id=160805)
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Danny, have you done the impedance test that you indicate, or some facsimile, blocking a little less than 1/2 the back of a W enclosure? Were the results significant? Is this a test I can easily perform?
If the difference is small wouldn't the servo feature ameliorate that difference?
I was under the impression that one of the features of the servo was to compensate for fluctuating impedance changes due to voice coil heat changes.
If I need to test in a pseudo anechoic environment, I have a field that I can use where the nearest building would be 100-150' away. Or I could test nearfield, with a short window to eliminate reflections.
Having said all of that I have listened with the amps in the bottom position, and the sound is pleasant. I have listened to some Miles Davis acoustic bass, Eric Clapton-BB King Electric Bass, Sheffield Drum Corp various drums, and Symphonic music, heavy on the Tymapnis, and everything sounds as I think it should. I will also listen with the amps removed. I will ask a few others to listen as well so my personal bias does not impact what is a subjective test.
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Early, why the antipathy?
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Because you aren't the first Guy to refuse to listen to universal advice.
Seriously, why are you proposing these measures? If you want to keep the amps where they are, do it. Just live with the effects, which you have been told will be measurable. But if for aesthetic reasons you want to keep it as is, it is entirely your decision. Or go take your measurements and report back to us. We will be eagerly awaiting your results :wink:
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Danny, have you done the impedance test that you indicate, or some facsimile, blocking a little less than 1/2 the back of a W enclosure? Were the results significant? Is this a test I can easily perform?
Yes, I have made many similar measurements. You will not be able to run an impedance sweep unless you have a specific measurement system that allows it.
Just changing the insulation or damping material can have a notable effect in a boxed speaker (minor compared to what you are doing).
What you are doing is the equivalent of me designing a ported cabinet for you that requires a 3" diameter port that is 24" long for proper tuning, and then you deciding that 24" is just too long and you shorten it to 1". Then reason that the difference will have little impact.
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I will run impedance sweeps on one of the cabinets with both woofers in parallel, with & without the amplifier centered.
BTW, I purchased the No-Rez, but have not installed it. Is there something that shows where/how to install it?
What affect will the no-rez have on the sound? or if you prefer, what is its purpose?
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BTW, I purchased the No-Rez, but have not installed it. Is there something that shows where/how to install it?
What affect will the no-rez have on the sound? or if you prefer, what is its purpose?
The No Rez should be applied to each wall of the cabinet and staying about an inch off of the baffle so that it is not right up on the drivers.
It does have a very notable effect on the sound as well. The side panels are under a significant amount of pressure when the woofers are playing hard. This is especially true for the W frame version as there is a large un-braced panel on the front side. The pressure can excite and resonate those panels. The No Rez damps out the resonances. The result is a tighter and cleaner bottom end.
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What's the harm in just trying it with the amps on the floor behind the speakers, and then with them mounted? Yes, testing would be ideal, but seems like you could get a pretty good subjective sense of the difference with a relatively easy experiment on your own. And since you're a hobbyist, why not give it a try? You're clearly curious.
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Genjamon, I will try it, but I prefer empirical objective information, as I believe that we and by we I mean first & foremost me, are heavily influenced by biases, prejudices and other psychological baggage we carry around.
So I think I have the means to do some impedance sweeps, as well as listening. If I knew how to use REW better, I could probably get some useful data from there as well.
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I got around to doing the impedance sweeps this morning. I used "Woofer Tester 3" which I had received a few years back but had never opened. I fired up an old note book running Windows XP and has a CD drive to install the software. I calibrated the leads then calibrated using the supplied resistor.
Here are the first two plots;
The upper driver with the amp in the lowest position.
(http://www.audiocircle.com/image.php?id=161039)
The lower driver with the amp in the lowest position.
(http://www.audiocircle.com/image.php?id=161040)
I don't see much difference. What should I be looking for?
Or, how should I improve my testing?
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You're not going to see big differences doing small-signal impedance sweeps with a simple tool like that.
Although I do see a noticeable difference in those plots, you'd need to re-scale and zoom the view for a much better look at the area of interest. (Near the 200Hz range is the area of interest.)
Regardless, this is all irrelevant. You've already said the amplifier is mounted in that location and that's where it's going to stay. Case closed.
Dave.
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I said I was unwilling to remove it from the back of the cabinet. I am willing to center it in the back of the cabinet.
I am also willing to run tests to determine the effect having it in different places on the back of the cabinet, and off of the cabinet, publishing them here in case someone else wants to do what I want to do.
So Davey, how should I improve my tests to provide useful data?
What of significance do you see in the plots I posted?
Keep in mind I do not have the impedance plots from the drivers in free air so there is no way of knowing what they tested like in a controlled environment and the differences could be manufacturing differences.
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Per Davey's suggestion here are the plots zoomed and limited to 200 hz.
Upper driver with Amp on bottom.
(http://www.audiocircle.com/image.php?id=161046)
Lower driver with amp on bottom;
(http://www.audiocircle.com/image.php?id=161048)
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If you want to know what the effect is of the box then measure it with it in place then measure it with it removed.
As Davey said, you're not going to see big differences doing small-signal impedance sweeps. If you see any difference in a low level measurement like this though then it would suggest that the differences at high levels will be significantly more.
And again, to really know what the differences are then just listen to it with the amp as you have it and then with it out of the way.
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Danny, I do not trust my ears to that level of granularity. Having said that I do like what I hear.
I guess what I'm saying is, I am of the camp that says "If it can't be measured, it can't be heard." I will be the first to admit that my measuring skills ain't great, but I am willing to learn.
In running REW (I now have a calibration file for my microphone) I see very specific differences between the frequency response of the two cabinets, which for the moment I attribute to placement. One cabinet has solid wall beside it (about 30") and an opening into another room behind it, the other has a solid wall behind it (about 30"), and an opening to a hallway on the side.
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Danny, I do not trust my ears to that level of granularity. Having said that I do like what I hear.
But this hobby is all about what we hear. How can you say that you don't trust your ears?
I still say listen both ways. If you don't hear any difference then it doesn't make any difference. Why even waste time speculating the difference? Until you listen you'll never know.
I guess what I'm saying is, I am of the camp that says "If it can't be measured, it can't be heard." I will be the first to admit that my measuring skills ain't great, but I am willing to learn.
There is a lot of very easy to hear differences that can't be easily measured.
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At the end of last weekend, I hooked things up so I could A/B my B&Ws against the Woofer cabinets I built with a pair of KEF 101/2s providing the mid-highs.
While I like the sound of the OB woofer/KEF combination, it was time to see how they compared.
I was disappointed.everything sounded wrong, they sounded muddy, even the bass sounded poor in comparison to the B&Ws. I was pretty bummed out. I played with various integration settings on the bass cabinets and got them to sound a little better, but they couldn't compare to the B&Ws.
So during the week, I worked with a purpose, but a sense of doubt, on the OB mid/tweeter section to go along with the OB woofer section. I only built one because it is completely seat of the pants;
- Pick drivers that looked good to my novice eye.
- Make a cabinet that had as much to do with the wood available as any coherent design.
- Decided on a simple 6 db crossover mainly to protect the tweeter.
I stained but did not polyurethane the cabinets, and got the drivers installed this morning.
With trepidation I hooked it all up using wire nuts to temporarily connect the wires, cap & coil. I disconnected the right input channel to my test power amp and fired it up. I did some test sweeps with REW at about a meter, and it looked OK, a bit of a trough at 600 hz, otherwise it looked OK, so I switched over to my CD player. Played my Sheffield Drum CD, and listened. It sounded rather good. I listened some more and it sounded a bit bright, but it sounded great to me.
So I hooked one B&W up so I could A/B them. Now it was the B&W's turn to compare poorly. The B&W still sounds phenomenal, but the new speaker sounds better. I listened to my various test music A/B-ing them along the way. I am sure the new speaker could be tweaked a bit, perhaps a high pass capacitor at 80-100 hz to reduce the load on the mid woofer. It might be a bit bright, but the REW plot doesn't show that.
So now I am stoked to get the second mid/tweeter cabinet built.
This mid/tweeter cabinet has nothing in it from GR-Research which is why I haven't described what I did in detail. I do not want to step over any lines of decency, since Danny is kind enough to share his time and knowledge here.
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I ordered binding posts, and an L-Pad for each cabinet today. While ordering stuff, I ordered a "calibrated" microphone to do better testing.
I also have the second cabinet assembled, waiting for glue to dry and then I will finish sand & stain it. Hopefully by Thursday I will have the second cabinet ready for testing.
Since schlepping these cabinets to central Texas isn't happening anytime soon, does anyone know someone in the south Florida area that can help with Xover design?