Vifa RB2 kit meets mini transmission line

[GV#27]

A number of years ago I built these boxes in an atempt to replicate what PMC claimed as the worlds smallest transmission line speaker,the approx $1.5k model DB1 http://www.pmc-speakers.com/docs/147c7f79ded670_pmc.DB1i.pdf .They were able to achieve an effective line length of 5' within a compact 6"x11.4"x9" enclosure.As shown in the above link ( the pic under the heading ATL)you can see the line is created by 3 internal partitions and the channel is damped with foam.

For one reason or another I never completed the project but after seeing Madisounds Vifa Recession Buster 2 kit http://www.madisound.com/catalog/product_info.php?cPath=35_428&products_id=8525 I thought it would be perfectly suited for the project.

In fact the parameters of the 5" Vifa driver used by PMC(M13SG) are very similar to the ones of the Vifa M14 supplied with the kit.Therefore one can reasonably expect similar results as far as bass response are concerned. It will interesting to see if their claims of 50hz extension from this little box are realistic.

[GV#27]

Ooops this was supposed to be the second pic.I tried to get it as similar as possible to PMC's ATL .

[bikerboy]

Thanks for the idea. Any input will be a great help. I looked around and didnt see anything like that for box designs. I thought I might build a full range single driver speaker first but the RB was too hard to pass up on. Down to 50hz would be amazing!

[megasat16]

Ooops this was supposed to be the second pic.I tried to get it as similar as possible to PMC's ATL .

Wow! Open Baffled with Internal Wave Guide? :D

[GV#27]

the RB was too hard to pass up on.Yeah I wasn't letting that deal go by even though I don't really need another set of speakers.
Down to 50hz would be amazing!The vented box suggested by Madisound for the kit will get you near 50 hz ,but the box is bigger.However the quality of bass from a TL enclosure is reputed to be better damped and more detailed than that of a vented box.


Wow! Open Baffled with Internal Wave Guide? :DYep I should patent it.;)or maybe I will just glue the other side panel on.:D

[megasat16]

Yep I should patent it.;)or maybe I will just glue the other side panel on.:D

Yep! I thought it's a new design concept you are playing with. If it doesn't work well, you can always glue back the rear baffle and the side panel. :D

[davidfmartin]

Sweet! So are you planning on recessing the tweets?
How do they sound now?

We should start our own RB owners/builders thread :)

[TECHNOKID]

Thanks for sharing the info GV!

Cheers!
TK

[Face]

Very cool Fred!

[zingo]

Great project and great thinking.

[GV#27]

Sweet! So are you planning on recessing the tweets? I should and usually do but this time I'm not going to bother as I find it a PITA getting it right.

How do they sound now?I still have some assembly to do before the auditioning can begin.

[TECHNOKID]

I should and usually do but this time I'm not going to bother as I find it a PITA getting it right.
I still have some assembly to do before the auditioning can begin.Keep us posted! I was thinking about buying a couple kits, would be nice to know how they sound.

Cheers!
TK

[comfortablycurt]

Damn...that's a killer price. I've been wanting to play around with building my own speakers for a while now. I might have to pick up one of those kits sometime.

[GV#27]

Techno&Curt, you gents may not want to wait too long as Madisounds stock may run dry before you get in on the deal.You might shoot em an email to check.

[GV#27]

For those interested in such things,here is a good pic of the inards showing how they partition and damp their TL's. http://www.pmc-speakers.com/company/technology.php There's also a technical description with a just smig of marketing hype thrown in for good measure.:D

[Face]

I recently heard a pair of their OB1i's. They had a pretty good amount of low end for a small woofer.

[SCompRacer]

Kewl project. I'm a fan of TL bass.

[comfortablycurt]

Techno&Curt, you gents may not want to wait too long as Madisounds stock may run dry before you get in on the deal.You might shoot em an email to check.

I'd love to pick a kit up now...but my finances are tied up in a couple other soon to come upgrades right now. I'll just have to hope they still have them around afterwords, when I've got some extra coin.

If they don't...oh well. I'll figure something out one way or another.

[GV#27]

I have them dressed up in some maple veneer with stands to match.They will be getting several coats of lacquer and the top and bottom plates of the stands will be painted black.

I'm kicking myself for not taking the time to recess the tweeter as it would have looked much better.:(



I must say that PMC's variation of TL loading works as claimed.The bass is definately more extended than would be the same woofer in a sealed box.I could have gained a few extra hertz of extension had I built the recommended (bigger) ported box,but I think the TL would win on SQ grounds.In direct comparison with another DIY speaker also utilising a 5" woofer in a ported box,the TL's bass was very natural and articulate sounding aswell as controlled , whereas the ported unit while it dug abit deeper sounded somewhat bloated and ill defined incomparison.
Interestingly even though both woofers have similar excursion capabilities,I am able to push the TL's harder before the woofers start to unload.


I did not mount the crossovers in the enclosures so as to give me a number of options to expierment.Mounting the passive networks outboard will allow easy access for trying different caps/resistors in the hi pass section ,or removing it entirely when I want to run them biamped with an active crossover.

The 3rd pic shows both the stock passive network and the active unit.
The passive unit has 12db HP/ 6db LP slopes at 3k with a decent Bennic PP cap in the tweeter section,air core coils and cheap sand cast resistors.

The active unit is from a previous project but will get some minor mods for use with this driver pairing.It has 24 db slopes at 2k,baffle step compensation and will when modded add 60us of delay to the tweeter for time alignment.Preliminary listening show the active setup superior even without the mods having been done to it yet.:D

[megasat16]

Looks Very Nice With Maple Veneers and on the Custom Stands.

Are you making the grille also?

[GV#27]

Are you making the grille also?
What are grilles?:D


Nah I prefer to leave them nude.

[megasat16]

It's a negative for you lave them naked. I prefer you get these. They looks awesome! :D

[TECHNOKID]

I'd love to pick a kit up now...but my finances are tied up in a couple other soon to come upgrades right now. I'll just have to hope they still have them around afterwords, when I've got some extra coin.

If they don't...oh well. I'll figure something out one way or another.They are still available but a much healthier pricing (original pricing I guess?).



GV#27, they look beautifull! Job well done! I guess you made the stands too?

Enclosed like this they look quite a bit like my Athena... the stands look as good if not better then the VTI stands I am using for my Athena. Again, job well done! :cool:

[GV#27]

They are still available but a much healthier pricing (original pricing I guess?).You might be thinking of the Reference version that sells for $399.That kit has higher quality drivers and crossover components than the RB,RB2 but still a great bargain at the price.I believe the RB2 kits are now sold out.Maybe there will be an RB3?


.. they look beautiful! Job well done! I guess you made the stands too?Thanks ,and yes I built the stands aswell so they would match cosmetically and to get the speakers at the optimum height.

[bikerboy]

Nice work on the cabinets and stands. This will be the first pair of speaker cabinets I will make. I want to do a tl type also. I never liked ported speakers much so I was going to do a sealed box. Can you give us some dimensions or do you think something different would be better?

[ben62670]

.... I never liked ported speakers much so I was going to do a sealed box. Can you give us some dimensions or do you think something different would be better?


I like the range of ported speakers. They are easier to work with, and tunable, but after having PR's and sealed I have not had the urge to go back to ported designs. Sealed usually needs some boost down in the lower ranges which taxes the SPL output. Too many people shy away from PR's because they are very hard to model. After working with numerous custom speakers using all three styles with the same drivers, environment, and gear I have come to love PR's. Some people are under the impression that they actually boost bass in the lower regions, but this isn't really true. it helps the lower extension no more than a proper port. The big gains with a PR is that you lose next to no box volume, you have a larger radiating area, and no port noise. There is always trade offs. Sealed will hit harder and tighter than ported or PR's. Ported gains are deeper bass, and very easy to design with free programs, but again the SQ just isn't there.

Here are a few tips if you want to use PR's.

Try to build the box volume to approximately the size of what you would build with a ported setup. You can go with a smaller volume if you wish, but you will lose a bit of efficiency, affect the Q, and frequency extension in the lower regions. Deep bass with smaller ported boxes require ports that are way to long, and take up way too much internal box volume if you can even get them to fit.

So you have your box built and the PR is installed. Now run some test frequencies in the range you are going to use the sub, and more than double the high frequency. Say you are going to set your XO cut off to 80hz. You will want to test your response up to around 150(you may want to go higher depending on what kind of response you get(resonate frequencies rear their ugly heads sometimes pretty high)). So you have a chart that goes from say 15hz to around 250hz. Get a calibration chart that shows the actual DB's for the particular SPL meter you are using. SVS has that info on their website for some of the more popular meters. My rat shack SPL meter is down about 6db at 20hz IIRC. What you want to do is add more weight to the PR if the lows are not putting out the levels you want them to. Also when adding weight it helps bring down the peaks from room gain, and driver resonance that are in the higher ranges.
Another awesome thing about using a PR is you get to tune the bass for the environment you are in(room gains and nulls are a bitch). You can test the response from where you sit if you like, but I have found that using the standard 1 meter from the driver setup is best(thats how the rest of the speaker is designed, and it just sounds more natural). I used to look at the speakers +_3db factory chart like nearly 99% of people do:o If you move the speakers around then your room gain, and nulls change. The manufactures specs don't really tell the truth in your listening area. You can pop the driver out and add or remove weight as needed. Another real nice thing about PRs if you are using mid drivers like Polk does you don't need to add more amplifacation for the subs, and the output is very linier the rest of the speaker. Very efficient:)

[Face]

http://www.aespeakers.com/PRFAQ.php

http://web.archive.org/web/20010128132400/lambdacoustics.com/library/whitepapers/diyprdesign.htm

[ben62670]

I like the first link(bookmarked). Also I like to tune to the room:) The calculation may get you close, but after a little measuring TBE(trial by error) works very well.
Thanks Bro.
Ben

[GV#27]

Nice work on the cabinets and stands. Thanks BB
This will be the first pair of speaker cabinets I will make. I want to do a tl type also. I never liked ported speakers much so I was going to do a sealed box. Can you give us some dimensions or do you think something different would be better?

If you plan to eventually mate them to a sub then going sealed would be the easiest but for stand alone use I think the TL is a great option.I can draw a diagram and PM it to you if you are interested.

As for the PR they are great for subwoofers and bigger systems but we are talking about a 5" woofer in a mini monitor form factor and a first time build so IMO not practical.If bass extension is the priority then just build the ported option.Adjusting port lengths will give you the same tunability as a PR but you will have the very desirable benifit of being able to predict the resulting response with free software like WinISD.


BikerB if I can be of any assistance just ask.


Hey Ben long time no talky how are things?Is that Burr Brown DAC I sent you still singing sweetly?

[ShinAce]

I feel like there's some good port bashing going on without proper defense.

A ported box will have a 'Q' sort of like a sealed box, but it is changed by going with different box alignments. Box volume, box losses, and tuning frequency affect the 'Q' of the overall design.

You can't just build the smallest ported box possible, adjust the port until the response is nearly flat and call it a day.

[bikerboy]

Hi Fred,
I want to use these speakers for the computer or garage or as backups when I rebuild the xovers on my sda-2a speakers. I doubt that I will use the RB2 with a sub so I think your TL idea looks best for my use. I would greatly appreciate a diagram so I can get the TL cabinet built correctly. Do you use contact cement to stick the veneer to the box? I read some use elmers glue and iron it together. This will be the first veneer work I have done so it will be fun. Thanks, BB

[ShinAce]

Can we get a pic of the back of the assembled box? Or am I just being greedy?

[ben62670]

... As for the PR they are great for subwoofers and bigger systems but we are talking about a 5" woofer in a mini monitor form factor and a first time build so IMO not practical.If bass extension is the priority then just build the ported option.Adjusting port lengths will give you the same tunability as a PR but you will have the very desirable benifit of being able to predict the resulting response with free software like WinISD

Hey Ben long time no talky how are things?Is that Burr Brown DAC I sent you still singing sweetly?

Hey Fred. I have been out of touch lately. The last 2 months have been pretty messed up. I am almost caught up, but I am headed back to CT for another week. This time with my girls. The DAC is doing great. There is an occasional pop even with the signal locked, but the sound is better than my GDA-700. Jerry picked up that cheap DAC you recommended. We haven't ditched the wall wart yet. I my be picking one up myself. I want to do an integrate amp with the DAC built in for the bed room. Also I am thinking about some in the wall SDA's. The only component you will see is just the Integrated amp:) The transport will be my media server via RF remote.

As for the passive comments
Sorry guys about the confusion/high jack. The comments were just general comments about PRs and were not directed twords this project here:o

I was chatting with Fred in CA about doing some boards. I need to get in touch with him again too. We'll talk in a few weeks about that(I'll have a board for you to stuff). It is another piece in the puzzle on that multi tasking pre I have been working on and off for over a year. These tube head Polkies have really taught me a lot as of late. The biggest thing I have learned about tubes is the incredable sound stage that good tubes can pull off that I have never seen via SS or in passive pre's.

Take care.
Ben

[GV#27]

(Sorry this is a Reply to post #30,didnt see the second page.)

Sure if you are trying to achieve one of the alignments like B4,QB3 etc. then you are stuck with a specific box volume and port tuning for that alignment.However with modeling software you are not held fast to a specific alignment and can by trial and error within the software find a usable non standard box volume and tuning that can give satisfactory results.
As you are suggesting though box size/tuning relationship is very important and I have heard a few ported designs that exhibited reasonably tight and tuneful sounding bass though my preference is with sealed especially as you approach the 40hz and below range.

[GV#27]

I would greatly appreciate a diagram so I can get the TL cabinet built correctly. It may take a few days to get the drawing done but certainly will provide you one.
Do you use contact cement to stick the veneer to the box? I read some use elmers glue and iron it together. This will be the first veneer work I have done so it will be fun. Thanks, BBI use the wood glue iron on method as its much more forgiving than contact cement.I apply the glue to the back of the veneer and the box using a smalll paint roller.I recommend using paperbacked veneer to help avoid it from slitting.Also having a router with a veneer trimming bit will be a big plus.I think I posted pic's previously of thre procees,I will try to find them.

[GV#27]

Can we get a pic of the back of the assembled box? Or am I just being greedy?No pic but the line opening is at the very top of the rear and measures 4.5" wide by 1.5" high.Basically the back panel will be cut short to leave the opening at the top.The final panels are not finished or installed yet,I'm just using a removable panel for the time being.


btw I'm looking for a source of decent and affordable(not Cardas,WBT:D) binding posts that are long enough to mount through a 3/4" panel.

[Face]

http://soniccraft.com/products/connections/bindingpost/vampire_bp15hex.htm

[GV#27]

I have been out of touch lately. Same here don't read or post much anymore,excepting the last 2 days.
There is an occasional pop even with the signal lockedMine was doing that aswell if I get it operational again(I stole the analog PS) I will try to find a remedy.
Jerry picked up that cheap DAC you recommended.Oh yeah I forgot about him getting that one,how's the build and sound quality as is?
The biggest thing I have learned about tubes is the incredable sound stage that good tubes can pull off that I have never seen via SS or in passive pre's.Oh oh,you have been brainwashed and seduced by those deceptive euphonic tube colorations.:eek::p

[ben62670]

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=091-1245&scqty=4

I have these. Very cheap yet solid. The solder tab makes it a breeze to solder, and remove. I have used similar ones to the ones face has posted, but you can't remove the wire without unsoldering them.


Oh yeah I forgot about that one,how's the build and sound quality as is?

I haven't spent any time with it, but the SQ is very good. I trust Jerry's ears. We both have very similar taste, and both agree on subtile differences. My car has been dead for almost a month. I am rebuilding the whole top end. The heads will be done tommrrow(decked, and valves recut). So I will be able to get my ears on again.


Oh oh,you have been brainwashed and seduced by those deceptive euphonic tube colorations

Those dirty rats! Seriously until late all the tube gear I have heard was either washed out sounding, or more brittle than those crappy Adcom's I love so much. Before tubes were good with only certain types of music. I never thought in my wildest dreams that tubes could handle anything thrown at them. Imade a thread a while back that tubes were like bandaids. A bunch of people got their panties in a bunch without even reading what I wrote. I have a bunch of CD's that I used to love before I started getting into some real decent gear. On the newer gear the system magnified the faults. Then I had some hands on with some real nice tube pre's and amps. Those bandaid tubes really healed up some really crappy compressed sounding recordings, and still brought out excellent dynamics. Symbols just have such a live sound to them. Sound stage is so much better. I wish you were closer. Anytime you are in the area I will pick you up. What ever it takes. If I had the money I would fly you down here. I don't have gear of that caliber yet, but I have some real good friends nearby that do.
Take care.
Ben

[GV#27]

http://soniccraft.com/products/connections/bindingpost/vampire_bp15hex.htmThanks Mike those look real nice.

[GV#27]

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=091-1245&scqty=4

Thanks those look good aswell.

[GV#27]

I'm posting this to show BB a detailed pic of the real DB1's inards vs my clone shown in post #2 http://www.positive-feedback.com/Issue45/rmaf2009.htm. scroll down to pic# 9.It clearly shows the foam lining and partition locations.

[GV#27]

Here are 3 more pics of the finished clone with laquer applied,and showing xover and foam placement.

[ben62670]

Very nice as usual. Hows the sound? You run them active yet, or just passive?

[GV#27]

Very nice as usual. Hows the sound? You run them active yet, or just passive?Thanks .Yes I have tried them active and not surprisingly I prefered them that way,abit more dynamic and bigger sounding partly due to more baffle step compensation being added.The steeper slope and lower xover point of the active also improves the midband smoothness.Either way they image like crazy because of the narrow baffle width.The tweeter is a sweety ,it never turns hard or brittle sounding be it with the active or passive network,surprising considering it's cost.

[ben62670]

I'm looking to do a small set of speakers for the bedroom. Something I can drive with a gainclone. I was thinking about doing a full range Fostex driver and a small tube amp, but I just can't bring myself to do it. Imaging is key, and super low bass or very high levels aren't. Again nice work.

[Face]

Nice job Fred!

[GV#27]

Thanks Mike.


Ben,you might look at one of Zaph's designs with his new 5" driver.The Vifa RB2 kits are no longer available though you might be able to piece it together separatley,Madisound sells the tweet and I've seen the woofer on ebay.

[TECHNOKID]

Two thumbs up for your finalized project GV :cool:

Cheers!
TK

[proirklad]

A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.

[GV#27]

A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.Really,thats deep.:D



Oh and Thanks TK.

[vc69]

Yeah man, really nice looking job. I totally admire your craftsmanship.

[abes99]

Hi all tl lovers,cong for the nice job.
in my young days i build a tl from atkinson miniline,i still miss the sound and also miss the plannoone seem to know it.
could you send me dimension please
many thanks
if someboby can get hold of the mini line it would be great
blessing
abes

[zingo]

Sadly, the good gent who built that pair of speakers is no longer active on this forum.

[ShinAce]

Not to mention that woofer is likely sold out!

Abe: If you're asking about the atkinson miniline, you should start a new thread to avoid confusion.

[Face]

Sadly, the good gent who built that pair of speakers is no longer active on this forum.
He's back under another user name.

[FTGV]

Sadly, the good gent who built that pair of speakers is no longer active on this forum. I snuck back in when the mods weren't looking.:D

[zingo]

Sweet

[bikerboy]

Its only been 2 years but I am making headway on the RB2 TL design that Fred was so nice to share. I am going to screw the sides on so I can play with the stuffing if needed. I need to glue the front baffle on and bolt it up. I made the back so the x over is protected in the back panel.

[FTGV]

And I thought I took a long time to finish projects.:smile:Lookin good so far.

[bikerboy]

I glued the front baffles on and screwed the side on so I can change the stuffing if needed. I made the back so the crossover is recessed and protected. I listened to them for a while in the mancave and found the lack of bass noticable. I moved them into the garage and placed them in the corners. Now they sound great, nice bass and the tweeter is smooth. They sound much better than the frankenspeakers I used before. They need some hours before I can be critical but I like what I hear so far. Thanks to Fred, as I would never tried to make a folded TL cabinet. Maybe some nice wood veneer or crossover upgrades in the future but I doubt it as they are in the garage for now.

[FTGV]

Very nice neat work,some veneer and they should look awesome.I don't see any foam on the panel directly behind the drivers,I assume you added it later?If you scroll down to pic#9 in this link to can see how the original has 2 layers.http://www.positive-feedback.com/Issue45/rmaf2009.htm

I'm using mine in a secondary basement system driven by a vintage Yammy integrated.Having had some more seat time listening my initial enthusiasm has waned somewhat.While the bass is deeper than one can expect from a similarily sized sealed box I do notice it does impart a noticable boxy character to the bass notes in some music.As well because the crossover is deficient in the baffle step compensation dept. I find as you did it sounds more balanced with some boundary reinforcement.

All and all not bad for a $60 pair speakers(excluding wood and sweat equity) as these Vifa drivers are quite good IMO.In fact I think they are capable of alot more if one was to invest some time and effort into a complete crossover redesign.Somthing thats on my to do list.