[dlneubec]

I mostly agree with you for music. My current mains have a 10" sub in each and they dig very deep in a tapered transmission line and I usually don't use the 12" subs.


That said, I have found that there is some music that has a more content below 30-40 hz than typical and using the subs with that music gives you something I don't think you can get with any woofer that has an F3 in the mid 30's. It is as much feel as sound in that range.

 

[exojam]

That is why I need a new amp for my sub. It really seems to die around that frequency. Once I have one, I will try music again with my sub (since I am cutting off the speakers at 40).


Before these speakers I used to cut over at 80 and things seemed to OK.

 

[A9X-308]

I've been watching your build on the HTG forum and like it a lot. I love decent sized HE speakers, but personally am not convinced about OB even for mids.


Very striking and classy looking design.

 

[dlneubec]

A9X,


Thanks. I've heard enough open baffle to know I really enjoy the soundstage and open, uncolored midrange it can present, when done right and the mid is not overdriven at the low end.


I guess one could do a design exactly like this one with a small section of 8" dia. sonotube behind the mid, providing a sealed chamber.

 

[A9X-308]



Quote:
Originally Posted by dlneubec /forum/post/14764051


I guess one could do a design exactly like this one with a small section of 8" dia. sonotube behind the mid, providing a sealed chamber.

I'm planning on using a tapered section behind each mid, sort of a rectangular, MDF version of the tubes used in the B&W Nautilus shell shaped speaker, trying to control and absorb it that way.

 

[dlneubec]

The benefit of the 1/2" waveguide mount may have nobeen too clear from the graphs posted above, because they were taken under different conditoins. The graph for the flush was taken outside at 103inches and the 1/2" I showed was taken inside at 39.375". I did take one, however, for the 1/2" outside. Here is the on axis fo the two overlayed when taken under the same conditions, spl levels, etc., outside at 103". Sorry for the confusion. This shows a little more difference bewtween the two than what is apparent in the graphs above. At any rate, it made dealing with the rising top end of the HDS a moot point and what it shown is a simple 3 part xover in the simuation above.

 

[Mark Seaton]



Quote:
Originally Posted by penngray /forum/post/14763011


Why not cross over the TD12 at 700 or 800 Hz?

Along with the reasons already noted, there are significant benefits in the directivity and reduced lobing by crossing lower. Do a simple simulation of the midrange to determine what excursion is required for a given SPL, and then combine that with the response of the dipole mounting, and you will see what the midrange will or will not be capable of. It is certainly possible to cross the woofer much higher, but with that much distance between them and a capable midrange, such an effort might create as many problems as benefits.


Of course if you look at many big audiophile designs, this notion is commonly thrown to the wind, although they also tend to pay for it with resulting speakers which can be quite touchy to small placement or aiming changes. If you want to cross the very extended TD woofers up high, be sure to plan for it accordingly in the box design. This design intended to use the behavior of the dipole midrange over more of its range, and thus this isn't a concern, where the woofer close to the floor allows for some room to adjust for floor bounce.

 

[dlneubec]

Thanks, Shin, I value your opinion highly.

 

[dlneubec]

For those interested, here are some new and more accurate and comparable measurements of the Peerless HDS tweeter in a 1/2" waveguide mount (1/2" deep. 1/2" roundover) and a 3/4" waveguide (3/4" deep, 3/4" roundover) both show spl measurements on axis, 15, 30, and 45 degrees off axis (horizontally). These were taken at 1m, with a 5ms gated window, tweeter at about 80" above the floor (vaulted ceilings).


First 1/2" deep waveguide:

Next 3/4" deep waveguide:

 

[dlneubec]

Hi All,


I have been doing some testing with shallow waveguides for my BaSSlines project that I thought you all might be interested in. These are more thorough results than I have posted before. I created an insert into the baffle that would allow me to make multiple WG's and insert them into the same baffle, with same tweeter, same mic setup, position, etc. The tweeter is the Peerless HDS with the face plate removed. The tweeter is mounted by pressing it to the back of he WG cutout, held by a woof fixture. The measurements were all taken at 1 meter, with the mic 80" high, in the center of a room with vaulted ceilings probably 15' high at that point and with a 4ms gated window.


All the WG's were created from mdf by boring a hole with a forstner bit, then rounding over the appropraite amount and then routing from the back for the palnned depth of either 1/2" deep or 3/4" deep in these cases. These are something just about any DIYer can build petty easily, which was the idea. There are a few tricks to doing this, most notably, when using a 3/4" rounvoer bit, you have to have a backer piece to you mdf baffle that you also bore a hole through. This backer piece is needed for the bearing of the deeper 3/4" roundover bit to ride on. All the bore through holes on these were adjusted so the final throat sizes are about 1-1/4" +- 1/32" at the final size.


Most of the plots show the waveguide perfomance at 0-15-30-45 and 60º of axis horizontally, so you can see the effect on axis and the directivity off axis. The first plot is the HDS with a standard flush mount. My goal with the waveguide is to get some boost at the low end so that when qualized out in the crossover you get the possible benefits of lowered distortion, slighly higher sensitivity, better off axis directivity and a counter to the typical rising responce of the HDS tweeter on axis, which might be fatiguing to some over time. Also included are some comparisons of the favorite WG results on axis with each other.

HDS mounted Flush: 0-15-30-45-60º

1/2" deep WG, 1/2" roundover: 0-15-30-45-60º

1/2" deep WG, 3/4" roundover: 0-15-30-45-60º

3/4" deep WG, 3/4" roundover: 0-15-30-45-60º

3/4" deep WG, 3/4" roundover, with 1/2" deep 45º chamfer after, sharp edges sanded round by hand: 0-15-30-45-60º

3/4" deep WG, 3/4" deep 45º chamfer, sharp edges sanded round by hand: 0-15-30-45-60º

Here are the flush mount (red), 1/2" deep/1/2" roundover(pink), 1/2" deep/3/4" roundover (blue) and 3/4" deep/3/4" roundover (black), all on axis.

My conclusion is: it depends on what you are looking for. The deeper wavegides have more boost, but all peak at about 4kHz on axis. The 1/2" deep waveguide, with 1/2" roundover has the flattest FR on axis from 4kHz and up on axis. The 1/2" deep/3/4" roundover WG and the 3/4" deep/3/4" roundover WG have the best off axis responce when you get out to 30º and beyond and the most directivity. I'm now leaning toward either the 1/2" deep/3/4" roundover of the 1/2" deep/1/2" roundover WG's from a raw response point of view. I will see how they look in the crossover design.


I hope these results will encoorage some of you to experiment with this concept. I think it has a lot of merit and is not at all hard to do with just a router and standard bits. It helps if you have a drill press and a router table as well.

 

[dlneubec]

Here are some preliminary crossover results:


These are measured results, taken at 6' with the speaker up on stands so the tweeter and mic is about 80" high. A 6ms gated window was used, so the woofer output looks low, which is due only to the window length. You should pretty much ignore the data below about 500-600hz. I'd have to combine a longer gated farfield measurement on the woofer, with a nearfield woofer and port measurment to give an accurate picture of the low end.


The actual crossover points for the woofer and mid are about 450hz, the mid to tweeter, about 2.8kHz. I used the 1/2" deep waveguide with 3/4" roundover for these measurments. The 1/2" deep/1/2" roundover would give a flatter response in the 4-10k area, but is not as good off axis in terms of directivity. I will measure with it as well, so I can make a comparison. I will also listen to both to compare them.


At this point the crossover indcludes a notch filter to suppress the 6md38's peak at 5kHz, but it is mildly implemented at this time. When it comes to listening and voicing, I will try it with more suppression of the peak and with the notch filter out completely, to see what my ears prefer. I like to start with a pretty flat FR and then adjust by ear. I did keep the tweeter a little hot to start out with so that at 15º off axis it is about flat (see graph 2). Impedance looks like a nominal 8ohm, with a low of about 6 ohms. I've chopped off the graphs in order to keep them as small as possible while still easily readable.


Next up is lots of listening, which includes trying at least two different slot port lengths to determine what sounds best at the low end as well.

SPL with individual drivers shown (woofer not accurate below 600hz or so)

SPL on axis (black) and 15º off axis (blue)

Impedance/Impedance phase

 

[Looneybomber]

Wow, it's looking real good. Are you getting ready to start finishing the enclosure, or are you going to tweek it a bit more?

 

[dlneubec]

I'm in no hurry. I have developed a couple other crossover iterations that I want to mock up and listen to. They have the mid-tweet xover at about 2200Hz and 2400Hz. The one posted above is the highest crossover point I'm considering.


I will try to pick the one I like the best of the 3. Then I will probably rough out the second system in all mdf, mock up a second crossover and listen to the pair. I like to take 4-8 weeks to listen and tweak a crossover during the voicing portion of the design. After that, I will start thinking more seriously about doing the laminated hardwood and Lexan baffles, adding veneer, finish, etc.

 

[penngray]

I have the PHL1120 drivers now and more TD12S on order.


dlneubec, Should I match your Tweeter: Peerless HDS 810921 with them to build a second set?


The ribbon tweeter I have is great but I want to try some domes.


Also, could you build extra crossovers for me?

 

[dlneubec]

Penngray,


My passive crossover design would be exremely unlikely to work with your speaker. I'm using the TD12H, no the S, we have diffrent mids, and my design is for an open baffle midrange, which is different than a boxed speaker. Also , the baffle widths are probably all different and if you are putting yours in-wall, that's a serious change as well. All these elements are accomodated in a passive XO. Your speaker would no doubt require a complete redesign.

 

[penngray]



Quote:
Penngray,


My passive crossover design would be exremely unlikely to work with your speaker. I'm using the TD12H, no the S, we have diffrent mids, and my design is for an open baffle midrange, which is different than a boxed speaker. Also , the baffle widths are probably all different and if you are putting yours in-wall, that's a serious change as well. All these elements are accomodated in a passive XO. Your speaker would no doubt require a complete redesign.

This wasnt for my in-wall design....new speakers and I was considering your tweeter

but even then I didnt assume everything would be the same at all and I have all the values Im using. I just fear its going to take me forever to build some crossovers so I thought I could get someone else to help

 

[Nasty N8]

Ok maybe I have my equipment hooked up wrong or just the wrong program...What are you using to get those frequency curves? I tried REW and SATRTA and got crap graphs and could not get it to output pink noise or match SPL level? Any help?


Nate

 

[augerpro]

Dan uses Soundeasy. Measurements are done using an MLS signal, not pink noise or sweeps.

 

[dlneubec]

Here is an update to my progress. I now have a pair of prototypes with crossovers and I'm starting the "voicing" process on the design with the B&C mids. They are now in my living room to be used for both music and HT for tweaking purposes. This is the room they will eventually be in. I will still be looking at the Lambda mid as well.


Below are a few graphs illustrating where the design is at. It is using the 1/2" deep waveguide with a 1/2" roundover on the tweeter. The plot showing all three drivers is the on axis simulation in SoundEasy. SPL levels are not calibrated to real world levels. The single plot you see is the measured FR with a 5s gated window at about 8', so anything below 600hz or so is not accurate, in fact there is a bit of first relfection anamolies showing up in this plot. This is a plot at 15º off axis, which is the intended design axis, so they don't need to be toed in too much, if at all. Also included is a measured plot of the impedance/impedance phase.

 

[dlneubec]

It's been awhile since I posted an update in this forum, so I thought I would do so. Here are some updates photos. The baffles are laminated hardwood using Makore and Hickory. The box will be veneered with Makore Pomelle. It's starting to come together nicely.