ZX Spectrum: HiVi M6A + BG Neo3 PDRW

[Iridium]

Thanks Paul. I'll be sure to post if I end up making them. I might buy a microphone for some measurements too.

Part of me is still thinking about making the swope 3 way tower because I like the look. The ability to use the knockdown cabinet is nice for the ZX spectrum though, and the neo3 should be interesting.

[Paul Carmody]

This speaker was designed to use the Neo3 PDRW with the back cup. My only concern is if manufacturer specifications have changed. It's been quite a long time since I've used one of those tweeters.

As for mounting, I think you'll be good whether you surface mount or flush mount. It's a speaker meant to be listened in the farfield, so I don't think you'd really be able to tell which is which from a normal listening position.

[Iridium]

I guess I thought I was picking this design out as something that was proven. Maybe not built often, but looked interesting.

Make sure the specifications for the drivers you just got line up with the old ones, otherwise there will be issues...
Take some pics

I'm coming up dry on anything to compare behind basic specs. I don't think there is anything different. There have been copies of these drivers and PE currently carries some of the copies. Those guys over on AudioCircle seem to have more insght.

1) Open baffle, the Neo3 PDR extends its frequency response a bit lower, but I still wouldn't use it much (if any) below 2 KHz.

2) I tried surface mounting and recessed mounting. The good news is, there's not much difference. The bad news is - the big thing here is the ragged FR of the Neo3 PDR itself. It's not smooth at all. The only time I thought this was a world class unit was when I used EQ on it via my MiniDSP. I'm currently using my Neo3 design with the MiniDSP and I love it. But I could never design a proper passive filter that was as neutral and transparent as I wanted to.

Here's the closest I could get to neutral back then.

http://www.htguide.com/forum/archive...p/t-26798.html

These are my current speakers.

http://techtalk.parts-express.com/fo...hybrid-speaker

I had stumbled on that thread when I was poking around. You say open baffle did you mean remove the back cup on the neo3? The ZX spectrum is not an open baffle design. I was hoping Paul or someone else who has built these would chime in about the back-cup.

Your meniscus mounting plates look good in the thread. The current ones on their site seem to show 8 thru holes though so I am confused by that.

[fjhuerta]

1) Open baffle, the Neo3 PDR extends its frequency response a bit lower, but I still wouldn't use it much (if any) below 2 KHz.

2) I tried surface mounting and recessed mounting. The good news is, there's not much difference. The bad news is - the big thing here is the ragged FR of the Neo3 PDR itself. It's not smooth at all. The only time I thought this was a world class unit was when I used EQ on it via my MiniDSP. I'm currently using my Neo3 design with the MiniDSP and I love it. But I could never design a proper passive filter that was as neutral and transparent as I wanted to.

Here's the closest I could get to neutral back then.

http://www.htguide.com/forum/archive...p/t-26798.html

These are my current speakers.

http://techtalk.parts-express.com/fo...hybrid-speaker

[buggers]

Make sure the specifications for the drivers you just got line up with the old ones, otherwise there will be issues...
Take some pics

[Iridium]

The BG Neo3 tweeter is available again and I picked up a pair of Neo3-PDRW (w/backup) to build a pair of these (PE ebay account for $86/ea vs $127 on normal PE). I've found a few different build threads, but still have some questions.

Was this designed with back-cup for the Neo3?

I imagine since its not an open baffle design it would have the back-cup on. Right now the PDR version is open back and PDRW has the back-cup, but I'm not sure if this used to be the case. I didn't find any pictures in build threads that shed light on it either. There are also the deep back-cup versions but it sounds like those were very rare on the PDR version. I could model and 3D print the deep back-cup if its advantageous. Saw someone mention it lowers Fs.

Neo3 Mounting

For mounting would there be any sonic effect if I use the rectangular meniscus mount? The BG mount doesn't really seem like waveguide, but maybe has an effect over the flat meniscus mount. I asked meniscus for a picture of how the tweeter mounts with their plate and I am waiting to hear back. With 8 holes it looks like it would just be fasteners through the front.

https://meniscusaudio.com/product/bg-neo-3-face-plate-s/

There is a picture in this thread showing the meniscus mount, but it only has 4 holes not 8... so still don't know how it works haha.

http://techtalk.parts-express.com/fo...atrix-reloaded

Paul's page mentions the BG faceplates coming in pairs (back then), but this is not the case anymore and the price is higher for a single than it used to be for the pair.

Paul's page: https://sites.google.com/site/undefi...rs/zx-spectrum

Build Threads

https://www.diyaudio.com/forums/mult...uild-pics.html
http://www.diyspeakerforum.com/viewtopic.php?t=480
http://techtalk.parts-express.com/fo...s-center-build

I found someone 3D printing faceplates and back-cups which I thought was interesting. Not something you'll get a smooth/attractive finish on without more finishing work.

https://www.audiocircle.com/index.php?topic=171314.0
https://www.audiocircle.com/index.php?topic=172523.100

[Mayhem13]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

Unibox models in .5cuft sealed very well....if to be used with a sub of course. The near perfect 2nd order acoustic combined with a second order active from an AVR to a sub would make for a nice 2.1.......very nice indeed!

[Paul Carmody]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

I'm just trying to educate myself on the effects of different things, what makes a difference and what doesn't, how different changes affect different things, and so forth. From the little I know, I understand that putting these in a smaller box will result in less bass. I'm just curious whether the design would still "work" in other respects, or if it would cause problems.

What you will end up with by putting the woofer in a smaller box is less bass extension (obviously), but also you will get somewhat of a "bass hump" between 80-120 Hz (depending on the woofer). The larger the box, the flatter the bass response can be. I'll try to put a few models up later on if I get the chance.

You can sometimes get away with doing a given crossover in a different sized enclosure, but sometimes it might not sound right, if the designer voiced the bass to have a certain characteristic based on the box tuning.

[Filius]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

I don't have Excel, but thanks much anyway. As much as I would enjoy delving into the design aspects of speakers, I'm sure I will never get much beyond the dabbling phase. Well, maybe once my kids are done with college. ;)

[fastbike1]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

Gotcha'. Best way to get some info is to model some speakers. If you have Excel, go here:

http://audio.claub.net/software/jbabgy/jbagby.html.

If you try it and are confused about data entry, I'll send you a pdf version of one of the boxes I'm working so you can see how the specs get entered.

[Filius]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

Of course I know that if I build the design as designed, I will get the result the designer intended. Believe me, I have respect for proven designs, and for Paul as a designer.

I'm just trying to educate myself on the effects of different things, what makes a difference and what doesn't, how different changes affect different things, and so forth. From the little I know, I understand that putting these in a smaller box will result in less bass. I'm just curious whether the design would still "work" in other respects, or if it would cause problems.

[fastbike1]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

Sure, you can stick them in any cab you want. No guarantees on the results. It also won't be Paul's design.

Do yourself a favor and build the design as is. You have the choice of a modestly sized, ported tower or a smaller sealed version. You can see the F3 differences. Depending on your preferences you may be happy with the sealed design without a sub. You will be able to notice the 8 Hz difference in F3.

Thanks, Paul and Fastbike.

Just curious Paul, could I just stick the Spectrum's drivers and crossover into a 14L cabinet as is? Or would the XO need to be reworked somehow?

If I did that, would I be wishing I had a sub?

[Filius]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

Thanks, Paul and Fastbike.

Just curious Paul, could I just stick the Spectrum's drivers and crossover into a 14L cabinet as is? Or would the XO need to be reworked somehow?

If I did that, would I be wishing I had a sub?

[Paul Carmody]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

Since my parts are on back-order I have nothing better to do, so I googled the drivers for the Spectrum. I found the spec sheet for the M6a, which says 14L is the recommended box size. Whereas the Spectrum's box size is 30L. ( http://www.swanspeaker.com/product/htm/view.asp?id=78 )

I'm not suggesting that the Spectrum's box size is wrong, just asking for educational purposes. What does HiVi base its recommended box size on? And is there really that much flexibility in suitable box sizes for a given driver, so that you can make it twice as big and still get a good result?

Interesting question. HiVi's recommended box sizes and tunings are often quite good--for those looking to make a "normal-size" speaker from them with solid bass performance. A 14 Liter (~.5 cu ft) bookshelf speaker with that woofer would kick some serious a--. It might be a bit punchy for some tastes, but definitely competitive with bookshelves by Revel or B&W or Paradigm or whoever.

I went for a larger enclosure because I was trying to squeeze the most bass extension I could from the driver. Also, fastbike is right, I had the cabinet on-hand and I thought, "Why not?" ;)

If you were to try both sizes in Unibox or winISD or whatever, you will see the tradeoffs in bass extension and FR.

[fastbike1]

Re: ZX Spectrum: HiVi M6A + BG Neo3 PDRW

I'm sure Paul will give a more complete answer, but until then:
Don't know what HiVi bases recommendation on however it is likely a standard (simplified) model based on the tuning they quote. There is typically a lot of "flexibility" in box size depending on what you are trying to achieve.
Modeling software will easily show the difference in response for box size, tuning, alignment (i.e. sealed or vented, etc). In the case of the ZX spectrum I suspect the box size was chosen because its a "standard" cabinet that Paul has used in other designs. I think it was a "I wonder what" experiment that turned out well. You will also notice that Paul's tuning is quite a bit lower than the spec sheet.
Reasonable advice would be to ignore recommended box sizes and do your own modeling.

Since my parts are on back-order I have nothing better to do, so I googled the drivers for the Spectrum. I found the spec sheet for the M6a, which says 14L is the recommended box size. Whereas the Spectrum's box size is 30L. ( http://www.swanspeaker.com/product/htm/view.asp?id=78 )

I'm not suggesting that the Spectrum's box size is wrong, just asking for educational purposes. What does HiVi base its recommended box size on? And is there really that much flexibility in suitable box sizes for a given driver, so that you can make it twice as big and still get a good result?