HI-VI D6.8 and SB 26STAC like a modula MT, ideas?

[Onestone]

Hello everyone!

I would like to build a kind of bookshelf 2way with a HI-VI D6.8 and a SB-acoustic SB 26STAC, both very nice drivers in my opinion. Has anyone an idea or hint on construction size and crossoverwork? Might be something like modulaMT?

[Onestone]

of course floor standing was OK too, developing a crossover is teasing me and I fear not getting the best results cause of few experience. Until now all my speakers run fully active by use of a DCX but I want it with crossover network this time.

I hope, someone can help!!!
I want to reuse the speaker from my old midhigh-cabinet on the picture:

[JonMarsh]

Will have to check the tweeter specs and get back to you. There's a different SB acoustics tweeter I'd recommend.

[Onestone]

I found this: http://techtalk.parts-express.com/sh...-Tweeter-Tests

[JonMarsh]

I just checked the specs- this is a new SB tweeter, which I hadn't seen before. I'm not really all that fond of the so called ring dome SB tweeters- the one I've had a preference for is the SB26STCN which I have a pair on hand, and has a somewhat higher Fs, though still fine for this kind of application with a roughly 1800 Hz crossover in LR3. It's less expensive than the STAC. 30 degree off axis is very good for both tweeters. That's something that's near and dear to me, as well as distortion performance.

Both are 4 ohm tweeters and sensitivity is quite similar, so a network adjusted for one will work for the other. I have data on the D6.8, haven used those in a couple of designs- in fact, the earliest Modula type design was based on the D6.8.

If you can be patient, within the next two weeks I can probably synthesize a crossover design for this combination. I'm upgrading the hard drive in my MBP17 which I do LspCAD and Fuzzmeaure on today, but also have a bunch of urgent work stuff this weekend to complete before Tuesday and an early customer visit, so I'm kind of tied up right now. I'll take a look at the LF alignment and make recommendations for that, too. The crossover should be slightly simpler than the Modula MT, as there is no need for a notch network to deal with the metal cone resonance.

[Onestone]

oh, that was very fine to get professional help , I am very glad to have found you here. Having the data I would build it. As I have running the SB in
my old mid high-combination I can say it is very nice sounding. I often prefer it against the AMT on the top (I sometimes change the us). The use of the DCX digital crossover is not the best choice for me cause I am more turning and switching and changing instead of listening.

[Onestone]

JonMarsh wrote, the HI-VI D6.8 already was used in an earlier MODULA MT. Is there somewhere to find the drawing of it? I tried to find something but had no success. In the meantime until knowing about the crossovernetwork I could start building the enclosure. Does anyone know about the preferred sizes?

[JonMarsh]

Preferred size is the same for all variations- this was based on an off the shelf Parts Express Dayton 0.75 cu ft cabinet- if you're in the USA or Europe or some other locations, you could use one of those, or copy it's construction to build your own.

http://www.parts-express.com/pe/showdetl.cfm?partnumber=302-732[


This is the original Modula MT thread for the "prime version" (it was an earlier speaker built for my daughter that used the HiVi D6.8. the latter is more expensive than the RS-180, and not quite as low distortion, particularly in the midrange).

https://www.htguide.com/forum/showthread.php?13154-RS180-Modula-MT-you-asked-for-it-you-got-it!&highlight=Modula

This is a picture of that "early version for my daughter. Not recommended to copy as is.

[Onestone]

yes, EUROPE it is....germany

Transport costs will be to high so it should be own construction probably. Why can't you recommend your daughters older construction? The SB-tweeter might be added at lower frequency cause of its low Fres!? Is the position of the offset-tweeter OK that way on your picture?

[JonMarsh]

Well, I was referring to the complete design as implemented back then. With the SB tweeter and a crossover derived from the current Modula MT, things should be nice.

Offset tweeter works well for some placements, sometimes not for others- I tend to recommend symmetrical these days as a result.

[JonMarsh]

This design rework will be coming up Sunday!

[Onestone]

fantastic, very curious on it thank you very much for all the support!!!

[JonMarsh]

The nitty gritty....

First, a reminder about the Modula MT thread- all of the original basics and cabinet details can be found there; I'm not going to repost that information- life is too short!

https://www.htguide.com/forum/showthread.php?13154-RS180-Modula-MT-you-asked-for-it-you-got-it!&highlight=Modula

The Cabinet info in PDF form is available from Parts express at this link:

http://www.parts-express.com/pdf/302-732s.pdf

You should be able to build it or something similar from the information in that PDF. You can simplify or modify construction details as you need- that's why it's called DIY. :W

The raw response of the HiVi D6.8 is shown below- measured in the actual cabinet, not infinite baffle. While the HiVi D6.8 has nice T/S parameters for yielding extended bass in a relatively small enclosure, I usually only use this driver in three way configurations because of the issues which occur in the upper midrange.



These show up as a big bump in the response around 1 kHz, and a main breakup mode around 3.4 kHz followed by a very steep drop off in response, as shown above. These characteristics require some extra care (i.e., more parts!) in the crossover to get things sorted out.

As I don't have your SB tweeter you're interested in, I used measured data for a Scanspeak tweeter that measures very similarly on an IB setup and with a similar impedance curve and Fs- that's the best I can do under the circumstances, and should be fine for getting this close. In this case, the SS tweeter was measured on this target cabinet.

The resulting design looks like this, modified from the standard Modula MT crossover:



Topologically, the biggest changes are removing the HF breakup notch filter used for the RS180 (in parallel with L4), and adding an LCR notch filter for the 1 kHz bump in the HiVi D6.8 (L5, C7, R7), and adding an LCR zobel conjugate network for the tweeter impedance control (R9, L6, C11), so that the higher Fs of this tweeter doesn't put a bump into the stop band of the tweeter.

The effect of these network compensations are shown in the transfer function plot:



and the resulting simulated SPL vs frequency response:



Last, for reference, a plot of the simulated impedance curve, which shouldn't be a problem for any reasonable amplifier.

[Onestone]

oh FANTASTIC !!!! Thank you very very much for all the work. As I still have several of these double flared ports somewhere in my stock I just ask how to measure the length. Is it just included the flared ends?
Again all my thanks for so much invest of time and thinking in this kind of combination. Even the trouble of the woofer mids this will be very good end-result. As the D6.8 remember me on the DYNAUDIO I had in my FISCHER&FISCHER stone (shale) made speaker enclosures when I was very young, your development will bring my mind "back to the routes" as the HI-VI optically and with the big diameter vc very close to the earlier DYNAUDIO woofers.
GOOD TO KNOW YOU, thx again and have a nice weekend and good starting new week. Greetings from germany!!!!

[JonMarsh]

oh FANTASTIC !!!! Thank you very very much for all the work. As I still have several of these double flared ports somewhere in my stock I just ask how to measure the length. Is it just included the flared ends?
Again all my thanks for so much invest of time and thinking in this kind of combination. Even the trouble of the woofer mids this will be very good end-result. As the D6.8 remember me on the DYNAUDIO I had in my FISCHER&FISCHER stone (shale) made speaker enclosures when I was very young, your development will bring my mind "back to the routes" as the HI-VI optically and with the big diameter vc very close to the earlier DYNAUDIO woofers.
GOOD TO KNOW YOU, thx again and have a nice weekend and good starting new week. Greetings from germany!!!!

Mit freundlichen gruessen vom California -

7-1/2" can include the flares- there's a limited amount of room to work with in the cabinet!

Yes, of all the nominal Dynaudio clones, the HiVi and the Jantzen are the only ones that measure decently with regards to non-linear distortion...

BTW, my day job is with Infineon Technologies, since 1985 when they were the semiconductor division of Germany. I visit Munchen several times a year on business. What part of Deutscheland are you from?

[Onestone]

I live near Dortmund. Ah Infenion.....a student colleague who made doctor grade is working for that company. I myself made a student pratise time at Infenion (former EUPEC ...AEG SIEMENS joint venture producing IGBT power semi conductor in Warstein-Belecke).!

I hope soon to start with your construction data. Thx again and have a good starting new week!!!

[Onestone]

the resistors are all to choose as 10W-type?

[JonMarsh]

the resistors are all to choose as 10W-type?

That will work fine. The LCR zobel inductors can have high resistance (but subtract internal resistance from series resistor value) to save money. The main inductors should be AWG 14.

[Onestone]

and a (last) question: the 1.6mH e.g. is no standard. is it best to connect two inductors in series or do you recommend unwinding a bigger one? This moment I have no L-measuring device...

[JonMarsh]

Use two 0.82 in series, or a 1.5 then. Probably better to use the 1.5, as the DCR of two 0.82 will be much higher, as inductance goes up with the square of the turns. Next standard value is too high. I have a coil winder and often construct inductors.