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uptime 25th June 2012 01:24 PM

T-TQWT inside book shelf speakers?
 
1 Attachment(s)
I find this concept highly unlikely in reality, but the thought has been oh so very intriguing to me for some time. Basically, is it possible to build a pair of self-powered active crossover 2 way bookshelf speakers with each having a built in tapped or TQWT sub?

After you have gotten your head around that, the next progression of thought is how would one accomplish such a thing and where would you put the folds, etc? The biggest challenge I think is what do you do with all the space taken up by folds, etc? I am leaning towards a folded or tapped tube of some sort.

I am going to build whatever we come up with on this thread so that everyone can learn from the experience. Here are a few thoughts to get the synapses firing and what I have come up with so far:

- Build a somewhat “normal” two way with a decent ribbon or even standard high quality tweeter and a nice sized 5” to 7” woofer. Ported? But maybe not. Maybe just a sealed version.
- Then put the outgoing part of the tapped or quarter wave tube coming out from under the two way and build the folds behind the two way.
- I would love to drive the tube using the biggest driver possible. Maybe an 8”? (Ha! He laughs out loud.)
- I have also considered doing this as a three way plus the sub and driving each side of the pair using something like a four channel Sure TK2050 board on each side.
- Not really worried about looks, but because of cost, it probably needs to be MDF.
- I am not into pretty per se, but they do need to sit on a bookshelf and/or desk.

I have attached a simple sketch if this doesn’t make sense. Sorry about the art work. The trick is where to put the sub driver. Tuning the thing would be a huge challenge in and of itself…

Is such a beast even possible? Which drivers would I use? Could I build a nice sounding system for under $300 - $400? I am okay with running all of the active componentry separate from the speaker and it isn’t part of the cost per se. Maybe mini-dsp or on a laptop. It pretty much has to be active because the delay of the sub is going to be a problem compared to the tweeter, etc. We will have to pay attention to group delay.

No way around it, these things are probably going to be heavy. I will also warn you that I am a bit partial to Tang Band, Hivi, Peerless and Scan Speak but because we are trying to build them on the cheap, Goldwood, GRS, Dayton, etc. will all need to be looked at. This is all about compromise. The overall music and design for this speaker should be contemporary music. Rock, Country, Jazz with a little bit of classical now and then. Whatever we come up with will not even be close to perfect, and that is kind of the point.

What can we build that will be “close enough” and “good enough”, but 10 times better than anything you could buy in a store?
Attachment 288969

picowallspeaker 25th June 2012 01:53 PM

The subwoofer part seems more a double-reflex to me .
You can learn from 2.1 multimedia brands such Logitech or Philips .
a 4" or 5" inside the box and a fullrange would guarantee much of the audio band
being reproduced without too much distortion , given the power ....which is in the 10-20W ballpark . Just make the lowpass filter double , instead of mixing the LF channels , and you have an active stereo box .
Or buy a Behringer 2031 A and use another acoustic load for the woofer ...so you'll have already the amplifiers , speakers and active filters and you can concentrate yourself in experimenting :)

bjorno 25th June 2012 05:52 PM

Quote:

Originally Posted by uptime (Post 3071789)
..I find this concept highly unlikely in reality, but the thought has been oh so very intriguing to me for some time. Basically, is it possible to build a pair of self-powered active crossover 2 way bookshelf speakers with each having a built in tapped or TQWT sub?[/FONT][/COLOR]

Hi uptime,

I have tested this approach in different combinations of 'piggy backing' T-TQWTs to smaller front oriented speakers using the same enclosure but internally partitioned resulting in IMO very good designs :D

Quote:

..After you have gotten your head around that, the next progression of thought is how would one accomplish such a thing and where would you put the folds, etc? The biggest challenge I think is what do you do with all the space taken up by folds, etc? I am leaning towards a folded or tapped tube of some sort...
Simple: First:Find suitable drivers allowing to be used in small enclosures.then apply your DIY skills...;)

Quote:

..Whatever we come up with will not even be close to perfect..
Why not?

b:)

planet10 25th June 2012 06:58 PM

To accomodate any line capable of bass in a "bookshelf" design, you are likely to need a deep & stout bookshelf.

dave

rvrazvan 25th June 2012 06:59 PM

Try, share, and then recive some appreciation.
If you fail...try again :D

uptime 26th June 2012 06:27 AM

Quote:

Originally Posted by bjorno (Post 3072060)
Hi uptime,

I have tested this approach in different combinations of 'piggy backing' T-TQWTs to smaller front oriented speakers using the same enclosure but internally partitioned resulting in IMO very good designs :D



Simple: First:Find suitable drivers allowing to be used in small enclosures.then apply your DIY skills...;)



Why not?

b:)

Thanks everyone for the ongoing encouragement! I must say that sometimes I think that the only reason I am helped so much is because people take pity on me and because I am just the comic relief for everyone. Kind of like "Guy" from the movie Galaxy Quest if you know what I mean.

I do try to add funny anecdotal stories to every post to keep people entertained now and then, and this post is no different, but I have no idea if this is even working...

A couple of housekeeping items. I had no idea about the behringers. I knew they had to be out there, but I didn't think that they would be relatively inexpensive. My only thing is that, well, they don't have enough blinken lights, knoben, or usb-ish function habben. :-) And besides, how would I ever learn anything?

Quote:

To accommodate any line capable of bass in a "bookshelf" design, you are likely to need a deep & stout bookshelf.
Ah...uh, hm. yeah. And probably not very many books on the shelf either. But that did get me thinking. What is heavier, MDF or pressed paper (as in books)? The other active speakers I recently put together were hung with cables in my office from the basement cross beams. Besides my goal is to eventually have a decent set of speakers in every room of the house. And then of course start over. So far I have taken care of the living room, family room, two bath rooms, and my office. All custom set ups and I learned significant lessons from each.

(sorry a little ADD moment follows...)

And besides, my brother helped a friend with his garage sale and he couldn't sell his big pile of adcom amplifiers. Some were missing channels, but most worked and he was trying to get $5-$15 dollars for them. Nobody would bite, so he just gave them all to my brother for helping him out. They are in the 5400 range if you are curious. My brother kept 2 of them and gave me four or five of them to play with. I have since fixed all of them. And that of course this doesn't include the many other amps that are feeling a little underappreciated right now and just want to be turned on and feel useful.

You know, some people would think that 6 channels, 2 subs, and 800 watts is over kill in a small bathroom. But the amps are just glad to be useful. And of course the teenagers love showering in the bathrooms with speakers. That's why I had to outfit theirs with speakers too. They kept using mine! I can always tell when I have done a good job, because that is the room the family tends to gravitate towards and hang out it.

Anyway, this is what I am thinking for parts, and I would like to order them by the end of the quarter (pun intended) so I can get the best deal, but try as I might, I haven't quite gotten hornresp figured out. I did a very long session over the weekend and figured out most of the different types of horns and how to tune them, but the T-TQWT's are still just a little out of my reach. Sigh...

- Highs - Vifa BC25SC55-04, HiVi RT1.3 Planar, or I already have 2 HiVi
TN28's that we could use.

- HiVi B4N 4", Tang Band W5-704D 5-1/4" Woofer if we decide on a four way. For some reason the W5 made a really good mid on my last build. But it makes a great woofer as well. I guess we could just do two of them in a 4 way config. :-)

- I own a 6.5 inch Tang Band I fixed that completely separated itself from the frame and did it so cleanly that all I had to do was line it up and glue it back down. Of course I am lucky that's all that happened. It's only a 15 watt speaker and it "accidently" got 400 watts at 60hz one day. I am amazed at that the thing survived the whole fiasco and how great it measures and sounds. I guess I could get a second one and save some money... I have also looked at some other items that are on sale, and it appears possible to actually get some okay 6-8" drivers for crazy prices like $8. But I just don't think that they have the right xmax or range that we are going to need. But I may be wrong.

And finally, the reason we are building these. I am currently debating between the Tang Band W6-1139SIF 6-1/2", Tang Band W8-740P 8" or Tang Band W5-1138SMF 5-1/4". Space is really the problem. I have modeled the larger ones, and I think we could make any of them work even though they were designed with completely different purposes from each other. Some of them would probably just be plain too big. I have also considered using the HiVi M8N 8" again, but I think the box would be waaayyy huge. I am also seriously considering the Peerless 830946 6-1/2".

All of these speakers are either on sale or just a good bargain for what we are getting. I don't know anything much about the Peerless, but it looks like it might be what we need for the price.

Or we could do something crazy and get a couple of cheaper drivers for each sub. That would be really interesting, but they would take up too much room and I think sticking a little more traditional is going to sound much better.

Anyway, all of these are priced in the $45 to $75 range and I would rather get some good drivers and use tweeters and mids I already have or that are not so expensive to really prove that the bookshelf T-TQWT idea and have others learn from what we learn.

Thoughts?

uptime 17th December 2012 02:01 PM

What I finally did
 
Just closing out this thread. What I finally ended up doing was building a so called "isobaric" sub combo 2-way speaker. Pretty much what the previous drawing was, but isobaric worked out much better given the constraints. Primary reasons:
  • Got a great price on a whole bunch of neodymium 5 inch subwoofers.
  • Isobaric allows for smaller boxes. In other words, with bookshelf speakers size AND efficiency are important.
  • The cost of the subwoofers was so low in comparison to the amount of labor, wood, time, etc.
  • I didn't like the group delay associated with T-TQWT (and if that doesn't start a new debate, I don't know what will.) ;)
For a good starter thread take a look at:

http://www.diyaudio.com/forums/subwo...barik-sub.html


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