Full range plus supertweeter in the nearfield: cap or real crossover?

[morbo]

Heatmiser, since we're using this driver for the exact same thing, want to compare designs? I'm going with a ~ 13L enclosure tuned to ~ 49hz with a 1.5" ID Flared port 4" long. External dimensions are 15"h x 6.5" w x 12"d". Material is 3/4" mdf. There is a shelf brace just under 1/2 up the enclosure.

I have covered the insides in a variety of foams, from egg crate 'acoustic' foam around the driver in the top of the cabinet (top, back, one side) to a closed cell denser foam on the lower side walls and bottom of the cabinet, to bits of carpet underpad in various other places. I kind of went crazy with this stuff

Just waiting to get my baffles cut, hopefully this week and then I'll assemble and report back.

Are you going to design-in any baffle step compensation? This is one thing I was a little unclear on, whether it was needed for nearfield listening on a desk, or on top of a TV for example. And if so how much? I just disregarded it in the end, but I still worry about it.

Also, has anyone thought of using these sealed? I have another one coming for a center channel, and am considering sealing that one.

[HeatMiser]

Morbo, I was thinking of cheating and buying a pair of the small Parts Express boxes (7 liters) and just leaving them sealed. That gets me an F3 at 80 Hz, and I already have a sub to fill in. Even if I do decide to build boxes, I am motivated to keep them small, and experience has shown that I don't mind at all a slight rise in the lower mids/upper bass like I should get in a box that size:



If I have integration problems I may add a port tuned to around 40, but WinISD tells me that will increase the rise to near 3 dB approaching 100 Hz. We'll see.

All I've done so far is stick one on a scrap of wood and fasten it to a particle board box I had laying around with a bead from a hot glue gun. It really did sound nice even like that, but like you I want to get the clearest possible idea of what the highs are doing and felt like I was missing that top octave.

My understanding is that baffle-step is not an issue for nearfield listening, so I'm not going to worry about it.

As to sealed boxes and center channels, well... I saw your post in the other thread about experimenting with these drivers in cardboard boxes, and I found your comments very encouraging. Looking at the WinISD plot, and with my limited understanding of where dialogue sits in the frequency range, I am inclined to think that one of these in a box like I am building might serve very well as a center channel. Bigger sealed boxes seem to not gain much extension, but flatten the slight rise the bigger you get. Depending on your room and seating arrangement you might really need a tweeter in that application though; not for the extended response, but to get some decent dispersion. My own home theater room is wide and shallow, so that will be an important issue to me. But I know even less about home theater than I do about speaker building in general, so more input is definitely required on all counts.

On another topic, were you able to order a single driver from CSS? It looks like their form still just accepts orders for pairs of drivers.

[morbo]

Morbo, I was thinking of cheating and buying a pair of the small Parts Express boxes (7 liters) and just leaving them sealed. That gets me an F3 at 80 Hz, and I already have a sub to fill in. Even if I do decide to build boxes, I am motivated to keep them small, and experience has shown that I don't mind at all a slight rise in the lower mids/upper bass like I should get in a box that size:

Yeah that is a very small rise, and the Qtc is still quite good. Worst case scenario you can always put in a variovent or other aperiodic loading, I find aperiodic bass very satisfying. I'll be interested to hear though, if the sealed bass was 'enough' for you. Especially for a widerange driver like this, I think you'd want the greater control a sealed design provides, unless the bass is miles ahead in a ported box.

The thing about using it for HT is it will be high-passed at 100hz anyway by the reciever... I think I am going to make the center sealed to start and see how it goes, since it would be rear ported anyway I can always add the port and not screw up the cosmetics that much.

All I've done so far is stick one on a scrap of wood and fasten it to a particle board box I had laying around with a bead from a hot glue gun. It really did sound nice even like that, but like you I want to get the clearest possible idea of what the highs are doing and felt like I was missing that top octave.

Well, thats one better than my cardboard boxes

a box like I am building might serve very well as a center channel. Bigger sealed boxes seem to not gain much extension, but flatten the slight rise the bigger you get.

Well, I'll shoot for a Qtc between .5 and .707, I'm used to around .75 I think and that is very nice to my ears. My boxes are already built, so I will just add things to take up volume if its too big.

Depending on your room and seating arrangement you might really need a tweeter in that application though; not for the extended response, but to get some decent dispersion. My own home theater room is wide and shallow, so that will be an important issue to me. But I know even less about home theater than I do about speaker building in general, so more input is definitely required on all counts.

As far as the tweeter, this is the one application I know I won't miss it in. I've been playing with this cardboard center a lot lately, and I can walk around the room (also very wide and shallow) and even standing in the doorway, well to the right of the right speaker, and a few feet above the listening axis, the dialogue is pretty well locked to the screen. I don't know what to attribute this to, but needless to say I'm very pleased! Oddly enough I had a TB 871 in the exact same spot before, and did not sound as good off axis to me. Or on axis for that matter.

On another topic, were you able to order a single driver from CSS? It looks like their form still just accepts orders for pairs of drivers.

Yes, I was. You can email Bob at CSS and he will tell you how to fill out the form for one, you use the 'authorized discount' field and comments. I was actually going to have 2 'dual use' speakers, and just carry one downstairs for movie watching. But then I realized that I would probably want to add a tweeter to the nearfield speaker, and that in that case the driver should be as close to the top as possible to keep the center-center distance down when I add a tweeter on top, and finally that a driver on the far end of a center channel would look ridiculous. So I did order just the one driver, AND one of the 16ohm ones with different params and the truncated faceplate to boot. One wierd thing - the params on the CSS website for the 16ohm variant dont seem to 'add up' in my box modelling software - it tells me the values aren't right and wants to autocalculate them, which yields significantly different results for a few params and a noticeably different response. Not sure why that is, it didnt happen with the 8 ohm driver.

[HeatMiser]

My projected qtc is a little on the high side at around .85, but not too bad I think. I know I am compromising by cramming these drivers into too small a box, I hope I can gain a bit back with stuffing and careful sub placement/adjustment, it will be miles ahead of anything I've had on my computer desk for sure.

Your experience with just the single driver as a center is good news indeed, I haven't had a chance to play with it there myself just yet.

Just out of curiosity, do you have your eye on a tweeter yet? There don't seem to be many top-mounters to choose from (Hi-Vi, Morel), or I may be just looking in the wrong places. I'll be putting mine on the baffle but I'm just curious what you have found.

[morbo]

Well... I know RAW is using a Hivi SS1 tweeter, but I've never heard of anyone else using it or any reports on it. I assumed it was just to keep the system reasonably priced, since the woofer will be doing most of the work anyway. I was looking at something like a Vifa XT19, Seas 19TFF, 19TAF, Vifa 19TAD, LPG 25FA, or the little Audax gold domes. I suspect that since we'll be able to cross over a fair bit higher than normal (at least up to 4000k), we will have a wider range to choose from.

I have looked at top mounted tweeters, which seem nice, but AFAIK there are just the 2 main ones, Morel and Hivi, with the Morel being a bit expensive for me and the Hi-Vi somewhat unproven (no use reports I can find anyway). I suspect initially I will just try to use the TB 871, since I have it in a same-width enclosure, just to see how it would sound with a crossover. Then I'll order something else. I was thinking about the Vifa DX19, since it is very cheap around here, but then I saw some mesaurements Mark K did that make it look not so good.

[planet10]

Originally posted by morbo
... or the little Audax gold domes

For the application, that one could be the best of the lot... can you still get them?

dave

[morbo]

Dave - the little gold dome Audaxes (not the expensive HD3P oval dome) are on sale at Madisound and at Solen. Only thing is, there seems to be at least 2 variants;

1. TM010A7 30mm gold cone (from Solen)

2. TM010A39 Micro Series 10mm ion deposited gold dome ,very small (from Madisound)

I can't find any info, not even a response curve, much less feedback on either, and the audax website doesn't even list them

http://www.audax.fr/direct.html

[tiroth]

Originally posted by morbo
there are just the 2 main ones, Morel and Hivi, with the Morel being a bit expensive for me and the Hi-Vi somewhat unproven (no use reports I can find anyway).

I've been thinking about checking out the Hivi TN28, at ~$13 there is not much to lose. Check out the graphs on the page below. If reality is at all close, you'd expect that tweeter to sound pretty decent.

http://www.swanspeaker.com/product/htm/view.asp?id=123

[planet10]

Originally posted by morbo
the little gold dome Audaxes (not the expensive HD3P oval dome) are on sale at Madisound and at Solen. Only thing is, there seems to be at least 2 variants;

1. TM010A7 30mm gold cone (from Solen)

2. TM010A39 Micro Series 10mm ion deposited gold dome ,very small (from Madisound)

I can't find any info, not even a response curve, much less feedback on either, and the audax website doesn't even list them

I have a pr and depending on how you measure them they could be 10 mm (actual dome) or 30mm Iincluding surround.

Once the surround is added in, these are actually more of a cone with a really well done dome shaped integral dustcap & phase plug... i might have data somewhere.

dave

[morbo]

Wow, great to hear someone has used these! Any feedback/specs you can provide would be very helpful.