Xmas speaker project.

My B&W 309's finally started to surrender to 12 years of home theater use as did my Mission centre which blew both of the 4.5 inch woofers.

Money being a little tight this year and having 4 weeks off for the first time in years got me out in the shed. The design is a prototype, so I choose off the shelf componentry from Jaycar, including matching crossovers. As a means of testing I also have a very nice set of Kef Concord IV's.

After much deliberation and a great deal of time using the online design tools at DIY Audio & Video - FAQs, Tutorials, and Calculators for Speaker Boxes, Crossovers, Filters, Wiring and more, I finally settled on the design. Some of the cabinet design was inspired by the Kef KEF International - Showroom - Images
range. using a semi trapezoidal shape for dampening reflected sound waves in the enclosure. Much the same as you see when ripples in water disperse when contacting non uniform surfaces. These are to be sealed enclosures. I prefer the more accurate precision from this type of enclosure.

So we have Response 6.5 inch mid coupled with Response 8inch woofer and as I had a spare pair of Kef t33 tweeters, matched this to 1200/5000 three-way crossover.So a reasonably inexpensive setup, now all that was needed was the enclosures. The design worked out at an overall size of 1170 h X 260 w X 325 D for the enclosure. Constructed from 18 mdf with 4 mm recycled heart Rimu veneer, which I machined from 100 x 50 rough-sawn studs. This meant that the wood had good color & character including weather stain and nail holes.

Basic enclosure with divider and some of the internal bracing installed.
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Front view of finished internal case showing speaker position. These would be routed when veneer had been applied.

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Speaker holes cutout and ready for mounting. First layers of clear shellac applied. Three in total then lacquer finish.

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Finished units apart from grill which I haven't decided on the design of just yet. To be honest I really like the look of these as they are.

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And how do they sound? Well truth to tell I wasnt expecting too much as I didn't know a lot about the Response drivers, but I have to say they blow my old B & W's away and then some. The Kef's dont beat them either which was a surprise. Initial I felt the mid range was a little bright but after 20 or so hours of reasonably hard running in they are settling very nicely. I have them coupled to a Onkyo SR576 home theater amp.
The base is excellent and the mid nice a crisp with the tweeters topping out without shouting. The crossover I bought for these is recommended for these speakers and I'm glad I choose them as they seem a very good fit for the Response units. Frequency response is 30Hz to 22Khz. My sub has been retired, its entirely superfluous with the new speakers.
The movie Transformers - The Dark of the Moon has a lot of very low base sound during action sequences especially in the explosions and these bad boys make the floor jump big time, which makes for a very nice change.

My son works for Heathcotes ( think NZ version of Harvey Norman).
He feels that while not as refined as B&W's and the new Kefs, once they burn in more they will give then a run for the money. I'm upgrading the amp soon so the speakers will be going into the sound lounge and we will test them against some of the high end gear. Should be fun.

Total build cost approx $400.00 NZ give or take a dollar.
Now I know how the speaker enclosure performs, the next set will have either Seas or Morel drivers.

Hi Dust Mite... great job well done, couple of quick questions.
How did you address the group delay issue? From the photos it looks like you made your speaker plinth flat, causing all drivers to be roughly equidistant from the listener’s ear.
If you look at the attached photo of my Sonus Faber Cremona you will see the speaker is angled back to give the higher frequency delay.
I personally am not a big fan of this approach as it takes most if not all drivers off axis, but it is a compromise of the design.
You also mentioned that you decided against porting the cabinets, what did the drivers want?
Ok now the good news / bad new depending on how you view it. The speakers from Jaycar are generally of a fairly high quality, so paying more to step up to something like Seas or Morel is not necessarily going to give you a huge leap in sound quality.
The first set of speakers I built in the late 90’s were Jaycar driver, but at the same time they were also built by Vifa (used Polk Audio tweeters) so buying from Jaycar doesn’t necessarily mean you’re not getting a name brand quality.
And just like you I was blown away with the result. Not sure how you managed to build them on that budget though, as that seems awfully cheap for what you have.
I have been using Bass Box pro and X-over Pro for a very long time. While the interface is a bit 1980’s you can generally do a decent mock up on them.

Group delay isn't something that's audibly easily detected. Most proponents suggest 20 to 30 ms isn't going to be heard, and that the room acoustics will in all likelihood change any perceived phase or timing issues anyway.
To date I haven't heard anything in the new system to suggest that's its a problem. If I was still using my 12inch sub I would have to set the phase shift and delay according to room acoustics and how it sounds. I'm not entirely sure my hearing is that accurate anyway. Ii may have been 30 years ago, but even then this wasnt really an issue in commercial speaker building and I remember having listened to some absolutely superb gear. It seems the its likely to be more problematic in a system the relies on a sub to drive lower order base frequencies.

The woofers I bought can be used for ported or non ported enclosures. I simply prefer the more (to me at least) precise out put in the lower frequencies from a sealed cabinet. To get similar precision for a ported enclosure isn't of course impossible just a order of magnitude more difficult to get an accurate setup.

However the result seems to be a nicely balanced sounding speaker and that's all I can ask without the benefit of an audio lab.
Cheers
Ralph.

I guess the question comes down as to whether you are prepared to gamble what you could potentially gain against what you could lose. You could gamble on the ports and get it wrong and produce even less low frequency response, than a sealed enclosure.

I tend to agree if you don’t have the right audio equipment to measure properly; the sealed cabinet is by far the safer approach to go, provided the driver will support a sealed enclosure properly, some larger drivers won’t.

I have often wondered if it is worth trading group delay for being off axis. To me I would say I can more audibly pick the driver drop off from being off axis that I can notice any group delay, but having said that there are those that are far more knowledgeable than I that still opt to tilt the speakers backwards.

Don’t know if you have looked at my build thread but I am looking to set the tweeter back from the mid woofer and then set both back from the woofers. I figure I can kill two birds with one stone doing it that way. Anyway great job and I look forward to your next build.

Just curious are the 6 1/2" & the 8" in seperate cavities?

Hi Scratcher.

Yes the Mid & Woofer both have their own enclosures.
The mid isnt sealed as its a multi purpose woofer/midrange.

I also agree with you re group delay, I'm never sure how good a ported enclosure will be. My B&W's were nice (ported) but I always felt that they sounded a little muddle down low. I dont mind giving up a little bit of low provided the clarity is improved.
Having good testing equipment would be nice, however I do have a fairly accurate "ear" so anything really ugly I will notice. To date they seem to be behaving well.

I’m with you on soggy base, it sounds terrible. There is a science in itself just trying to get the ports right, one which a lot of people don’t give the appropriate respect.

Quite often speaker designers are willing to trade speaker excursion / x-max for smaller diameter ports, which in turn allow shorter port lengths, but at what cost? If you have good ears you will have no doubt heard the port noise generated by a wrongly sized port.

But poor base response is not always the fault of the port; the amp can be just as much to blame. An undersized / poor quality amp that doesn’t handle low frequencies well can have the best of speakers behaving badly.

I noticed an appreciable difference when I went from a multi-channel analogue amp to some Class D digital amps (granted there was an appreciable price difference too).

Here a little trick for you if you decide to build the next lot with ports… At the port entrances (inside the speaker) place a very light dampening material over the inlet.

The toes out of the missus stocking or extremely light foam will do nicely. The slight obstruction slows the air down entering the port, reducing unwanted port noise. But don’t make it so heavy that it restricts any flow, just the lightest of light.

Sealed speakers have their place as the compression created in the rear chamber helps keep the base tight by proving a slight spring for the driver cone to return, but it does provide a marginally compromised sound.

If you get the ports just right you will get the optimal sound. Best example I can think of is valve springs on a high performance engine, too little and you will get valve bounce, too much and you wear the lobes off the cam, wear the rocker gear excessively & waste HP.

Or better yet a dual exhaust. Many years ago a mate of mine built himself a custom stainless duel 3” exhaust for his 308 powered Statesman, it took a week for the exhaust gases to get out. Great if you are building a dyno queen and looking for ultimate power, but bad idea for a heavy vehicle that needs torque to move.

Flip side of the coin would be if he went for a duel 1.5” system. The copious back pressure would help with torque, but it would be panting for breathe at the top end. Speakers are not so different to this.

Finding that sweet spot where nothing is wasted can be tricky, sometimes it is good to experiment a little with some PVC added to the end of the port, like the slide on a trombone to get the right balance.