DTQWT-12

[hometheaterdoc]

Rich,

I have at least a dozen sets of these here at the house:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=240-717

How high do they need to get the horn up off the floor?  These are 1.5" high without the cups....

I was going to post them for sale as I found a whole box full of brand new sets of these... I've used them for years on my custom subwoofers... really nice stuff....

[Carlman]

I highly recommend a permanently mounted, simple round foot with carpet gliders on the bottom.  
I would suggest you also find a place along the bottom of the speaker to additionally mount spikes with large knurled knobs that you could screw down into the carpet once you've decided on a location.  Then you can hear the difference in real time going from platform feet to spike feet... and have absolute control on all aspects of positioning.  I don't know why this isn't done as common practice...  

What would be really cool is big round feet with large knob-rings incorporated with gearing to make it super easy.  Spring loaded spikes would also work... or flip-down spikes that are hinged somehow... Anything so that once it's in place, going spikes isn't a big deal... Because positioning with spikes is a huge time suck.

-C

[richidoo]

Thanks for the suggestions guys!

I want it to slide on the carpet for easy placement and position experiments, be easily picked up on the hand truck, and it has to have a 2.25" tall gap all around the bottom to allow horn exhaust.  So it will be a bottom plate the same size as speaker sitting on the floor, with the speaker suspended above it with matching veneer plywood risers. Some absorption on top of the plate to kill midrange echos in the horn as would carpet.

Some really nice footers over at Herbies Audio labs...
http://herbiesaudiolab.net/spkrfeet.htm

[tmazz]

Parts Express black speaker spike .41 each when you by at least 4

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=249-727&FTR=249-727

Wow! This web page makes a big deal about offering free lifetime technical support for you spikes!  

Talk about giving people the sleeves out of you vest.  

BTW: Anybody running a VPI HW-19 series table - the rubber feet on the bottom of the table are mounted using 1/2 - 20 threads, so these should fit right in as a direct replacement. I thought that coupling the TT to the counter-top with spikes was a very worthwhile improvement and I paid a lot more than 41 cents for mine. (Warning - if you have a non-American built TT remember that it most likely uses metric threads and these may not work for you. Search under speaker spikes and they have other ones with metric threads.)

[richidoo]

I removed a lot of stuffing from the midrange driver last night and that opened up nicely. I think it is just right now. No obvious ringing but a little bit of thickness. Good as it's gonna get. Quite beautiful actually.

The bass sounds good, no ringing, but extension is less than before, and softer than the midrange. So I need to remove some from the bottom of the bass horn (again,) to allow the full length of the horn to work to extend the bass as deep as possible. With the bottom of the horn stuffed full, the sound can't get in there and the bass extension is lost. Leaving a center path to the bottom unstuffed extends the bass while controlling ringing pretty well.

I am realizing that this is a horn speaker, so there will be a sonorous, bigger than life character to it. It is a beautiful sound, but not perfectly accurate. Sounds is fattened when amplified by the rear horn. Trying to make it a clean hifi speaker ruins the magic. So now after hearing it as hifi speaker I am backing off the damping to allow it to sing more, even though the tone is wettened enough to annoy an audiophile. The alternative is too dry for a music lover. Like any speaker, there is a compromise point in the damping between not enough and too much. Getting that correct is really important with a horn, and with horns this big the slightest change is audible and can make or break the speaker. Another aspect of the tuning is that the stuffing not only controls the ringing, but also the SPL. Since this speaker has two horns, the ringing must be controlled in each for different frequency ranges, but also the level balance between Mid and Bass also has to be right. Right now the mid is at optimal tone, and bass tone is good, but extension is limited and SPL too soft. So less stuffing will increase SPL and extension but the sound will become rounder and tonally less perfect, but more beautiful.

But it is soo much better now than the first listen, after half dozen changes to stuffing. One thing is good, my back doesn't hurt anymore from lifting these things, so I guess I needed some more back strength.

I want to weigh these speakers.  I have a bathroom floor scale, but I can't lift the speaker and place it gently on the scale.  Can I weigh the front edge while the rear edge is held up level to the front with some wood blocks, then do the same for the rear edge, then add the two weights together?

[BobM]

As the bass extends and opens up you will probably have to adjust the midrange and maybe the tweeter again. I've found that adding bass somehow always seems to make the top end more pleasurable and exciting too.

Dry sound is not enjoyable to my ears either. Music needs life and drama and dynamics, even at low volumes. It's all relative, but too much leads to fatigue. A balancing act for sure - I'm sure you'll keep tweaking for some time to come. And don't be surprised if the finishing changes the sound somewhat also.

DIY projects like this never seem to be completely finished, since you know the intimate details of the speaker and can make minute adjustments and tweaks and hear the changes that each makes. It's all fun, but just don't think that you'll ever be "done".

[richidoo]

Great points Bob! Thanks. I agree with all of it, unfortunately!  The benefit of commercial equipment for me is that the fear of fucking it up prevents tinkering! But even that I think has it's limits, once a DIYer, always a DIyer. I think I know enough now to be a danger to myself.  I am already thinking how I can mod some commercial speakers that I want to buy but don't even own yet! Sick!  Why buy speakers that need mods? 

Well, I hope I am close the finish line with the first stage of stuffing. I've covered the full range from loose to tight sound, and back and forth with the Mid vs bass interactions, so I am learning how much to take out and put in to affect the desired change. In the beginning it was just a crapshoot, steep learning curve, and sore back. It still takes a good hour to change the stuffing. You are right, opening up the bass will change the mid too. But the problem I had with mid ringing was up in the 800-1200 area. Certainly the woofers do play up that high also, but I don't have any of that midrange ringing now, so hopefully it will stay gone as I remove stuff only from the low freq part of the bass horn. In the beginning I did hear the midrange going over into the bass horn and ringing in there, a terrible cardboard box type coloring. The bass horn needs a little bit of stuffing all the way up to the top for that reason, to keep the mid from ringing up there.

I've been listening to the mids for 24 hours and this is the first time since startup that I have not heard anything I wanted to change with the mid sound. Open but not too colored, just a tad round as expected.  The designer mentioned in his OB11 design article that the OB design might be even better than his beloved DTQWT boxes for the less color and snappier 15" OB bass, I can see how that would be true. Eventually I'll build that OB11 also.

Tuning the speakers with Sol's i60 has been a great tool. It does not color anything and has plenty of extra power and bass grip. Switching to the 300Bs adds the tube charm which hides a lot of flaws. Better to tune it with a clean amp then enjoy an optimized speaker with the sexy amp later. I have enjoyed a lot of music with the i60s on these speakers too, especially when they are stuffed on the loose side.

[richidoo]

At the g2g, somebody connected the speaker wire bananas to the speakers in the normal way, speaker wires to bass posts and the bass posts are jumpered to the mid posts. I usually put speaker wire ground on bass and signal to the mid posts and jumper back to the other. This sounded better on my previous speakers. After the meet I noticed how nice the speakers sounded. Today I noticed the wires were normal, so I put them back to my weird way. Tonight listening to some great vocal tracks that Shane brought to the meet I started noticing that the mids were too soft (again.) Depressed that the nice sound of the previous couple days had been a cruel trick, I started thinking about pulling out stuffing, etc, to bring mids forward more. Then I remembered I'd moved the jumpers. So I just put them backto the normal way and the midrange came into balance. I think is it because the rear bass drivers play up very high and are more sensitive than the front drivers. So connecting SCs  to bass terminals reduced resistance and increased voltage to the bass drivers and brought out the mids.

Could also be that the tweeter is still a little too hot.  I think the treble sounds pretty good now, but worth trying another notch down. It was really too loud at the beginning of the g2g so I took it down .5ohms on Shane's advice and with his help. After the mod, he thought it could use still more attenuation.

I think I will try soldering jumpers internally at the crossovers to eliminate the external jumpers which don't really fit well on these cheapo Dayton style posts that came with the kit.  The inner post that must fit inside the spade is too fat to accept the spade. So I am clamping it as best I can, but it's not right. Jumpering at the crossover will eliminate that, until I can get some WBT posts.

[tmazz]

.... The inner post that must fit inside the spade is too fat to accept the spade. So I am clamping it as best I can, but it's not right.

I always keep a few sets of Monster X-terminators laying around for just such a situation.



The spades get tightened down on the x-terminator and then locked in with a set screw and the banana itself has a center pin which when screwed in spreads the blades of the banana insuring a tight connection. In addition to making nice adapters for binding posts that will not accommodate certain spades, they are also very handy at G2Gs because the make moving SC from amp to amp a very quick and simple job.

[stereofool]

At the g2g, somebody connected the speaker wire bananas to the speakers in the normal way, speaker wires to bass posts

GUILTY 

[richidoo]

Thanks Tom, those would work nicely!

[Face]

Lose the PE posts and brass(cheap) nanners.  If these are keepers, they deserve a pair of Cardas posts. 

[richidoo]

You're absolutely right Face. I'm not sure they are keepers yet, hence the internal jumpers to bypass the cheap posts. I think I'll put the main input off of the PE posts too.

[stereofool]

As I mentioned Sat...put your crossover 'outboard' and it would be much easier to tweak  !

Easy for me to say...I don't have to do all of that work  !

[richidoo]

Converting to externals would be mighty pricey - to do it right, and I don't have any intention of using an active crossover on these. It's not too hard to work on the crossovers inside the big horn. I could always remove them easy enough, just two screws each.