Upgrading SB29 to Illluminator Ring Radiators or get a better Mic?

[Tyson]

I've got a SEAS Nextel w18, their 6.5 inch driver as my midrange and 3 peerless 7 inch HDS Nomex woofers in a pair of narrow towers. I've tried the Peerless HDS tweeters and they were too dry and light sounding for my tastes. I've been using the SB Acoustics SB29 as a replacement and I like the warmer, smoother sound signature. But it's overall less transparent and measures worse than the HDS. I'm wondering if upgrading to the considerably more expensive AirCirc 6600 or the Illuminator Ring Radiators from ScanSpeak will give me the transparency and the sound signature I'm after.

I'm using a DEQX preamp/crossover so I'm very flexible with the crossover points, and I can use any crossover slope, up to 300db/octave, and it corrects for driver FR and also corrects for phase within each driver and across all drivers in the system.

*EDIT*

Hmm, doing a bit more research on my own, I realized that the mic I'm using (a Dayton) doesn't have a calibration file type that can be imported into my DEQX, so I now realize that I've been trying to measure my speakers with an uncalibrated mic.

Since I plan to keep making more DIY speakers in the future, I'm thinking that a better mic might be a good investment at this time. I'll be selling my modded DCX to fund it, so I can afford something nice. I'm looking at Earthworks QTC line. It seems like the QTC30 would be perfectly fine for speaker measurement since it measures out to 30khz and the mic comes calibrated from the factory. It also seems to have very good impulse response, something that's very important to me since the whole reason I bought the DEQX was to do time and phase correction.

Anyway, for around a grand or less, is this the best choice for a measurement mic?

[benchtester]

I've got a SEAS Nextel w18, their 6.5 inch driver as my midrange and 3 peerless 7 inch HDS Nomex woofers in a pair of narrow towers. I've tried the Peerless HDS tweeters and they were too dry and light sounding for my tastes. I've been using the SB Acoustics SB29 as a replacement and I like the warmer, smoother sound signature. But it's overall less transparent and measures worse than the HDS. I'm wondering if upgrading to the considerably more expensive AirCirc 6600 from ScanSpeak will give me the transparency and the sound signature I'm after.

I'm using a DEQX preamp/crossover so I'm very flexible with the crossover points, and I can use any crossover slope, up to 300db/octave, and it corrects for driver FR and also corrects for phase within each driver and across all drivers in the system.

I don't have experience with the SB29. However I briefly tried the AirCirc versus the (Scanspeak version) HDS. They both seemed very good to me, but the AirCirc seemed a little more clinical or edgy than the HDS. So I don't think you will find the warmth you want with the AirCircs.

[5th element]

Also bear in mind that the off axis performance of the SB29 is worse then the HDS and the AirCirc. This could help in giving you the smoother sound, as it's throwing less high frequency energy into the room and towards side walls etc.

[Tyson]

Hmm, could be. I wish the SB29 had a metal flange and rear chamber, then I'd probably not even be asking this, I'd simply stick w/the SB29. If it is the ring radiator nature of the SB29 that I like so much, I wonder if I should look at the 7000's ScanSpeaks instead....

I edited my title and first post to reflect the new info...

[Jed]

You can have Cross Spectrum Lab calibrate your Dayton mic for you.

[Tyson]

I bought it from Cross Spectrum, but the file type used cannot be imported in to the DEQX software. Plus, the Earthworks seems to have much better impulse response, which calibration doesn't seem to affect one way or the other. For time and phase measurements, this seems fairly important. If I was just doing FR measurements, I'd look at keeping it, but since I'm interested in FR, phase, and group delay, particularly in the high frequencies (where I seem to be the most sensitive to errors), I'm looking to replace it.

[Saurav]

Could be that all you need to do is change the extension on the file. Or change spaces to commas or vice versa. Or add a 'dummy' phase column.

Every calibration file I've seen has the same format: frequency, SPL, phase. I think the basic CSL calibration doesn't do phase, so that column may be missing. If the CSL file is missing phase, all you do is import it into Excel, add a column of 0s, then export it back out as a text file. It's possible that there's a bigger incompatibility, but that would be surprising.

Of course, a better mic is a better mic.

[Tyson]

Good advice! I imported my files into my spreadsheet program as space delimited and saved it as a .mic file, which is what DEQX requires. Then I opened the DEQX software and imported, and it didn't complain.

My daughter is asleep already, so I'll have to wait till the morning to re-run sweeps, but hopefully this at least addresses the FR issues.

[Bear]

I'm looking at Earthworks QTC line. It seems like the QTC30 would be perfectly fine for speaker measurement since it measures out to 30khz and the mic comes calibrated from the factory. It also seems to have very good impulse response, something that's very important to me since the whole reason I bought the DEQX was to do time and phase correction.

I have an M30, but I haven't really pushed it too hard. From my experience with Earthworks, all of their mics are calibrated during QA, but they just don't give you the calibration file without paying a few extra dollars (kind of irritating given the price, actually). In some cases, they will have "lost" (purged?) the calibration file, but for most recent stock, you don't have to send them the unit to get it "calibrated". :T

[gainphile]

Smooth = good off-axis response. So perhaps look for a 25mm tweeters. Better yet 19mm although you then sacrifice polar response matching with the woofers.

[DoubleTap]

It's rare to see subjective opinion questions. Until somebody figures out how to design a microphone with a human brain attached to the end, subjective opinions matter.

That said I agree with you somewhat about the SB29 vs HDS. And from the sound of what your tastes are, you won't care for the 6600 that much either. It's definately an in your face tweeter, not hard or edgy but very attention grabbing. It does it extremely well though, personally I really like the 6600 but it can be a bit of a shock first time you listen to one. The Scan Ring Radiators are more mellow, but still preserve the great dynamics and detail. I have a pair but can't see myself ever paying that $$$ again for another pair.

It sounds like you would LOVE any of the Seas Excel soft domes. They have IMO the most accurate presentation of anything out there, and are just so sweet and smooth. The T25CF-001 would be a great choice if you don't want to spend Millenium/Crescendo bucks ... unfortunately the T29CF-001 is no longer available. Based on your tastes I'd highly recommend the tried and true Vifa XT25's, you really can't go wrong with those if you want smooth and musical. Also the Morel MDT33 (or whatever it's called now), or the Supremo's would be fantastic choices. I've used my Supremo 1108's in 3 systems now and just love that tweeter, it does everything well.

Another I'm just getting started using but think might be a great option is the RS28F. It couldn't measure any better, and first impression is a great balance of smoothness and detail with great dynamics.

[Tyson]

Thanks DoubleTap, exactly the info I was hoping for!

[Jed]

I'd get the mic issue fixed before evaluating and replacing tweeters. At least then you'll know what you are hearing and why. I wouldn't give up on the HDS just yet. It's one of my favorite dome tweeters, and I find it much more open and transparent than the SB29, which I used in the Madisound RBR kit awhile ago. The XT25 and SB29 share more in their presentation than they differ IMO. That said, unless a tweeter is compared with the same transfer function, system, Fc, etc. it's really hard to know for sure what the absolute winner is, and then everyone will have a different opinion anyway. In the end... do what sounds best to you. :T

[Tyson]

Agreed Jed, it makes no sense to have a precision piece of equipment like the DEQX and then use a cheap, imprecise instrument like the Dayton to do all the measurements. Once the check arrives for my DCX, the Earthworks QTC40 is on the top of my shopping list.

[SpeakerGuy]

...might be a great option is the RS28F. It couldn't measure any better, and first impression is a great balance of smoothness and detail with great dynamics.

I see it's on sale currently, $40. Remember to click through the Parts Express add here on HTGuide...

[Tyson]

I went ahead and ordered both the RS28F and the SEAS 27TDFC. Someone bought my Peerless HDS tweeter and Nomex midwoofer, so I was able to get both tweeters to try out. I also ordered an Earthworks M23 mic, so I should be in for a bit of fun in the next week or so.

[Tyson]

Finally was able to get the time to drop in the RS28F, and luckily it was a straight drop in to the 27TDFC cutout. Holding it in my hand, it was obvious that the RS28F is built to a higher standard. But build quality does not always translate into sound quality.

In this case, the RS28F lives up to it's reputation as a great tweeter. I like it quite a bit better than the 27TDFC, which is impressive because the SEAS was one of the best tweeters I've heard. But the RS28F is even smoother and more relaxed and open sounding, with equal (or better) detail. Which is surprising because I felt that that mesh grill would negatively affect the sound. But, even straight out of the box, with no burn in, the new tweeter already sounds quite a bit better.