New Build 2-way Driver selection advice sought.

[Technote]

I have been browsing the DiyAudio forums for a while which has helped me enormously to comprehend the vagaries of speaker design...thank you. This is my first foray into this realm for which I would welcome advice on driver selection. The caveat with my enclosure design is that the speakers are constrained by physical dimensions. It envisaged having a Mid Range driver with an external diameter between 140mm and 152mm paired with a suitable tweeter no more than 65mm outside diameter. I have utilised the various software products, particularly WinISD to devise a selection of drivers.

Tweeter Choices:
Tymphany Peerless NE25VTS-04 (SPL 91.26)
Dayton Audio ND25FA-4 (SPL 90)
Dayton Audio ND25TA-4 (SPL 91)
Scanspeak D3004/602000 (SPL 89.2)
Tymphany Peerless XT25SC90-04 (SPL 90.2)
Tang Band 25-1719S (SPL 90)
Dayton Audio ND28F-6 (SPL 88.4)

Mid Range: Closed box 4.235 Litres.
SB Acoustics SB15NRX2C30-4/Norex (SPL 89.5)
Dayton Audio DC130B-4 (SPL 92.1)
Tymphany NE149W-08 (SPL 87)

I am also trying to get to grips with crossover design which is self complicated with too many drivers...so I really need to whittle this list down to a few pairings. Your assistance is gratefully appreciated.

 

[GeoffMillar]

I think the DC130 and the XT25SC90 could make a nice speaker, but a sealed box would need to be around 8.5 litres (see link below), it uses a different tweeter but the same mid-woofer:

http://speakerdesignworks.com/TritrixMT_pg_1.html
Apparently, the XTSC90 'official' SPL is a little low. Impulse Audio (YouTube) tested it and found their samples to be around 93dB, so measurement in box would be essential for accurate XO modelling. The frd and zma files from Impulse Audio are still available from Dropbox (I think).

I've used both drivers, albeit in different projects, and really like their sound, especially for the money.

You have a wide spread of $ and quality in your list, have you a budget in mind?

Geoff

 

[454Casull]

Any reason you couldn’t find a design that already exists and meets your needs?

 

[Technote]

Any reason you couldn’t find a design that already exists and meets your needs?

I am an engineer and I am always looking for a new challenge. So when I started this project I decided I would develop the entire project from scratch. The best way to learn this stuff.

 

[Technote]

I think the DC130 and the XT25SC90 could make a nice speaker, but a sealed box would need to be around 8.5 litres (see link below), it uses a different tweeter but the same mid-woofer:

Geoff

Thank you, that is a very helpful article. The DC130 mentioned in the article is the "S" shielded version. I checked the parameters in WinISD and the recommended volume for the DC130B-4 was 4.2 litres. I appreciate there are a lot of variables that influence volume but I feel I have to start somewhere with a ballpark figure and then develop it further. There is capacity in the design to increase the volume.

I am not working on a fixed budget at the moment.

 

[GeoffMillar]

According to Dayton Audio, the specs for the shielded and unshielded are very similar; Fs for both is 51.8; Qts for both is 0.35; and VAS (equivalent volume) is 13.2 litres for the BS-4 and 12.3 litres for the B-4. Sd (cone area) is 93.3 for the shielded and 92.1 for the unshielded.

I don't use Win ISD but it would seem that the modelling should be very similar, given the specs, or does Win ISD have a tweak for shielded drivers?

I'm not aware of a project which uses the DC130 with that Vifa tweeter, but I've seen one with the DC130 and the Vifa BC25TG15, which is a slightly lower price but has a larger face-plate. I'm not familar with your other tweeter and mid options.

Geoff

 

[Sangram]

For small drivers like this, it's better to have a smaller (than larger) box, else it will unload quickly.

The SC90 likes to be crossed around 2.6k, any lower and it complains at high volumes. The peak dip combo in the middle of the passband is difficult to work with in crossover, and audible.

None of the small Dayton tweeters like to cross below 3.5k so be warned. Getting a 4.5-5" woofer to cross that high is a bit of a challenge. The Scanspeak + Vifa combo would the best from your selections, to my mind, but the crossover will require some thinking because of the resonances around 1.5k. I tend to want to notch the peak out and let the rest be handled in the rolloff, which indicates a possible XO around 2.5k. I still think the driver choices are a little bewildering, seeing as you've the $130 Illuminator tweeter as well as a $20 ND25.

If you're already looking at SB Acoustics, the best combo would be the Satori MW13P and the SB29RDNC small flange neo tweeter (there's also the Beryllium small flange, but that's 6x the price). Both the drivers are very easy to work with, no messy resonances, and the midband dip of the midwoofer is not noticeable in regular use. On paper the NRX/NBAC/CAC series is pretty close, but I prefer the midrange of the Satoris.

Anyway, these should work well with four components (plus whatever you do for matching levels). There's also the STCN (which performs worse) and your Illuminator tweeter (which should be a bit better, but more pricey). The hard cones do not have any midrange resonances, so there's that. You still have to notch out the ultrasonic peak, but that should be a simple resonance trap across the woofer inductor. With smaller speakers, my personal choice is to spend a bit more ton the midwoofer as it usually is doing most of the heavy lifting with the crossover further out of the vocal range.

Good luck with your journey!

 

[454Casull]

I am an engineer and I am always looking for a new challenge. So when I started this project I decided I would develop the entire project from scratch. The best way to learn this stuff.

Well, you're asking for help, so I figure you're just trying to find the right place on the spectrum in terms of how much challenge/assistance you want.

That said - what's your budget and listening distance? And, it will end up being a rather small bookshelf, so will you have the ability to use sub(s)? If so, just one, or a stereo sub setup (i.e. one underneath each bookshelf, or otherwise reasonably close)?

In any case, assuming a generous budget and a mid-field listening distance, I'll start with a suggestion of SS D2004/602000 and SB MW13TX. Top-class midrange, and bass is as good as you're going to get without moving up in size to the Purifi 6.5" woofer. As for the tweeter, while it is compact, it can play cleanly very low which will help avoid a severe dip in power response at the crossover frequency. Plus, it doesn't drop off in the treble off-axis as quickly as some other tweeters that can play low, which will broaden the listening window (but which might require a bit more room absorption to deaden the highs which might sound bright if left untreated). The D3004/600200 is a great choice as well, and has surprisingly good off-axis performance for being a larger dome.

https://hificompass.com/en/speakers/measurements/scan-speak/scanspeak-d2004/602000https://hificompass.com/en/speakers/measurements/satori/satori-mw13tx-8
Advanced tip: the Satori has a spike in 5th order HD at 1200 Hz owing to the 6 kHz on-axis breakup. While it's quite a narrow peak and overall not a big deal, that peak is still substantially higher than the HD5 distortion on either side. Different ways to mitigate it: 1) passive notch (LCR) filter paralleled with the driver, or 2) cover the driver with a thin layer of wool felt or melamine foam. If 2), you'll have to experiment with the thickness but 1/4" would be a good starting point; you want high absorption at 6 kHz and negligible within the woofer's passband.

 

[GeoffMillar]

Whatever drivers you choose, the crossover design is going to be your biggest challenge; and why it's been suggested that you possibly look at an existing project which uses your options. Listening habits etc are also important.

However, if you choose drivers for which measured in-cabinet frd and zma (frequency response and driver impedance) files are available, you could use those in free software such as Xsim and will have a much better chance of designing a crossover which could work.

That's why I suggested looking at, for example, the Impulse Audio Dropbox database: the web site presenter has been generous in making his files available, the link is in his video on his "Life S5" monitor speaker. The caveat is that your cabinet would need to have the same volume and baffle layout as used for his measurements, otherwise the zma and frd files won't be accurate. The S5 uses the SB Acoustics SB15pfc 5" mid woofer and I think the cabinet is too large for your purposes.

There are other sites which have made those sorts of files available, I'll post the links when/if I find them.

For example: http://www.rjbaudio.com/Audiofiles/Driver FRD files.html

Geoff

 

[454Casull]

Advanced tip: the Satori has a spike in 5th order HD at 1200 Hz owing to the 6 kHz on-axis breakup. While it's quite a narrow peak and overall not a big deal, that peak is still substantially higher than the HD5 distortion on either side. Different ways to mitigate it: 1) passive notch (LCR) filter paralleled with the driver, or

Too late to edit. I actually meant a parallel LCR filter in series with the driver:

https://www.diyaudio.com/community/threads/some-speaker-driver-measurements.317632/post-6440503

 

[Technote]

None of the small Dayton tweeters like to cross below 3.5k so be warned. Getting a 4.5-5" woofer to cross that high is a bit of a challenge. The Scanspeak + Vifa combo would the best from your selections, to my mind, but the crossover will require some thinking because of the resonances around 1.5k. I tend to want to notch the peak out and let the rest be handled in the rolloff, which indicates a possible XO around 2.5k. I still think the driver choices are a little bewildering, seeing as you've the $130 Illuminator tweeter as well as a $20 ND25.

If you're already looking at SB Acoustics, the best combo would be the Satori MW13P and the SB29RDNC...

I initially populated the crossover design products using the Dayton tweeters and I was; to be honest; quite overwhelmed...it was not a good place to start crossover design. The driver choice is limited by physical size...a consequence of the enclosure design plus it gives me some options for mounting a selection of drivers when I get around to building this.

Your idea of using the Satori MW13P and SB29RDNC is a good suggestion and could work...would require some tweaks to the enclosure design but doable. Thank you.

 

[Technote]

Well, you're asking for help, so I figure you're just trying to find the right place on the spectrum in terms of how much challenge/assistance you want.

I have been working on this project since mid-November and mainly thanks to the extent of knowledge on the diyAudio forums I have managed to progress the design to the point of designing the crossover. There is no substitute for experience and knowledge gained from many years of study and work in this field...which I don't have; the reason why I now need to reach out to the experts before my mind melts with frustration.

Having worked with WinISP and Hornresp programs, familiarizing myself with the theory and practical application of speaker design from the many online resources I decided to tackle the crossover. So again working through the options with VituixCAD and Xsim I realised that my own lack of knowledge in this field was compromising progress.

 

[AllenB]

You'll see Sangram was going through frequencies as this seems to be where you are.

Normally a crossover begins with acoustic design, but if you've already chosen drivers and put them in a box for whatever reason then try this next step of analysing the appropriate ranges where they can be crossed. If you don't end up with a frequency conflict then you can define the choice and move to the next step.

 

[Technote]

You'll see Sangram was going through frequencies as this seems to be where you are.

That's exactly right...I am currently working with the various driver suggestions kindly offered by the contributors. I have only selected drivers that will work within the specified volume and meet the physical dimensional criteria. My initial problem was to find a matching pair that would realise a workable crossover.

This certainly would be a lot easier if I was able to share the box design but I can't do that in a public forum...at least not yet.

 

[PeteMcK]

"managed to progress the design to the point of designing the crossover" - yet you're asking for driver choices? Does not compute...

 

[abstract]

"managed to progress the design to the point of designing the crossover" - yet you're asking for driver choices? Does not compute...

Well no, but it's also understandable that sometimes people "don't know what they don't know".
For instance predicting what you will like the sound of more. I've been surprised before, thinking I would prefer X, when I actually preferred Y once I was able to hear it. Net wisdom might say "cross the sub no higher than 150Hz", but then your ears say "actually, that 3.5" wide-band is clearly struggling below 500Hz and the sub is still going strong". Similar experiences may apply here.

 

[stv]

I have only selected drivers that will work within the specified volume

the main question will be whether you have an additional subwoofer (you mention "midrange" not "midwoofer" in your post) or you want the speaker to have some decent bass. if the speaker needs to have some bass your may need to narrow your selection down to midbass drivers with low FS, low VAS and not too low QTS (for closed box) to "work" in the specified volume. if you have a subwoofer and you cross it over above 150 Hz you are much less restricted. you may also consider using a (big) high-pass cap in series with the woofer. this can have similar effect as a bass reflex port.

 

[Technote]

"managed to progress the design to the point of designing the crossover" - yet you're asking for driver choices? Does not compute...

Perhaps I should clarify that comment. For me, this is a learning process from enclosure design which establishes key parameters, to a selection of suitable drivers using WinISD and Hornresp then progressing to familiarising myself with crossover design. It is within the crossover environment that I realised incompatibilities with driver choices...thus the need to reach out for expert advice. This is new to me and therefore I need to understand how each program on the journey works and what I can expect to extrapolate that will enable me to progress to the next stage.

 

[Technote]

the main question will be whether you have an additional subwoofer (you mention "midrange" not "midwoofer" in your post) or you want the speaker to have some decent bass. if the speaker needs to have some bass your may need to narrow your selection down to midbass drivers with low FS, low VAS and not too low QTS (for closed box) to "work" in the specified volume. if you have a subwoofer and you cross it over above 150 Hz you are much less restricted. you may also consider using a (big) high-pass cap in series with the woofer. this can have similar effect as a bass reflex port.

Thank you this is very good advice.

 

[454Casull]

Thank you this is very good advice.

Re-quoting myself:

That said - what's your budget and listening distance? And, it will end up being a rather small bookshelf, so will you have the ability to use sub(s)? If so, just one, or a stereo sub setup (i.e. one underneath each bookshelf, or otherwise reasonably close)?