Centre Speaker using Alpair 10 and some limitations

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I am building a set of L/R and centre speakers for my parents. They didn't have a large budget, so I was keen on building them something decent. I thought I could also veneer it to match their furniture.

I ordered 3 Alpair 10s and was planning on building three Classic GR Mar-ken 10.2s. After further conversions with my parents my Mum was very keen on putting the speaker into the AV component of their TV cabinet. The problem I now have is that the height of the AV component is only 200mm, and the width of the Alpair is 160mm (138mm for the back of the driver).

I modified the mar-ken design so the cabinet was 190 (h) x 350 (w) x 200 (l). Using 18mm MDF, this leaves only 7.5mm each side of the driver from the side panel. Could this be an issue? Anyone have ideas of what I could do?
 
frugal-phile™
Joined 2001
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Without checking anything else, the vent is too narrow by 2 material thicknesses.

Here is the "official" skinny as possible version:
http://p10hifi.net/tlinespeakers/FAL/downloads/SSP-Mar-Ken10g2-190611.pdf

If you need to maintain the 190 width, you will need to increase vent height to maintain vent cross-section -- or shorten the vent by the appropriate amount. If you are using 18mm material then vent height needs to go to 18.5mm.

The proximity of the walls will likely be heard as a honkiness or cupped sound in vocals.

dave
 
An alpair 7 would be the closest timbre match to A10.2 mains. CGR goes from 13 litre to 9 litre. I may have a 10 litre A10.2 box (i do have one that size for A12)

dave

I have a Alp7 (1st Gen) in one of Dave's wide stretched centre cabinets - it certainly works very well. Since most HT rigs will XO the center above 80Hz, I think its reduced LF capability compared to the 10.2 is moot, and AFAIC the 7.3 does things in the critical vocal band with more refinement, inner/low level detail and depth than the larger drivers.

Of course in a really large home theater with 3 rows of seating, popcorn machines and wet bars, the smaller FR drivers might not suffice, but in a more modest venue (under 400ft^2) the 10.2 & 7.3 combo & A6M for surrounds would be very nice.
 
frugal-phile™
Joined 2001
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Dave, thank you for your help. i would be interested in the 10l box.

I looked in my drawings... i have a 10 litre sealed box... Q isbutterworth and F3 is on the order of 80 Hz, almost perfect for a centre channel. I would be hesitant to make the front any smaller than it currently is.

One could get 6 mm by moving to 15mm, or with added bracing get 12mm by using 12mm panels.

dave
 

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Dave do you have a link for the speaker wires you like to use?



CAT5 network cable - teflon insulation aka "Plenum" - brand doesn't matter - strip outer jacket and untwist - just be careful with stripping the insulation, as it's tempered more stiffly than conventional "audio" wire to retain an engineered set of twists in each pair, and is easy to nick

for internal wiring of FR systems we use a single strand of the AWG 24 solid per polarity

this product has been a mainstay of frugalicious DIY geeks for well over a decade, and some folks take the time to braid monster sized cabling for higher powered systems - I tried that once and for my systems, the trouble wasn't worth it.

if you wanna get really tweaky, there are a few folks offering cryo-treated
 
I got the 12mm plywood cut up at Mr Plywood for the centre speaker.

I am now just trying to work out how to use the Jasper 200 jig with my new Triton router. I am new to plunge routers, so I spent about an hour going through the basics to find that I was missing a 1/4" router bit.. and the hardware store closed at 4.30pm and I arrived at 4.32pm :-(
 
Jasper jig

When you get your 1/4 bit be carefull to tighten it in the collet enough. You don't want it moving on you when doing multiple passes to create you rebated hole. Go slow because those bits are fragile. They are very loud as well so use hearing protection. You can use a bigger bit but you have to do the math and set the jig smaller the compensate for the fatter bit. Do a sample first.

That cat5 cable thing is fascinating. I have a ton of that lying around. For a longer run do you use multiple strands of the cable per polarity? I would love to hear technical information as to why these cable sound better than the typical multistrand. Is there a dedicated thread out there regarding cat5 as speaker cable?
 
That cat5 cable thing is fascinating. I have a ton of that lying around. For a longer run do you use multiple strands of the cable per polarity? I would love to hear technical information as to why these cable sound better than the typical multistrand. Is there a dedicated thread out there regarding cat5 as speaker cable?

There are hundreds of threads about CAT5 as speaker cables and interconnects. In summery, within reason, cables are cables. Use a cable calculator to determine what size (wire guage) cable you need. Two strands of CAT5 (one in each direction) is 24ga, four is ~21ga, all eight is ~17ga. Two CAT5 cables is ~14ga.

Or, go to Wally World and get a 3-wire 16ga extention cord in the color of your choice. I ground the green wire at the amp end for no real reason other than it might provide a minisule amount of RF shielding.

Bob
 
When you get your 1/4 bit be carefull to tighten it in the collet enough. You don't want it moving on you when doing multiple passes to create you rebated hole. Go slow because those bits are fragile. They are very loud as well so use hearing protection. You can use a bigger bit but you have to do the math and set the jig smaller the compensate for the fatter bit. Do a sample first.

That cat5 cable thing is fascinating. I have a ton of that lying around. For a longer run do you use multiple strands of the cable per polarity? I would love to hear technical information as to why these cable sound better than the typical multistrand. Is there a dedicated thread out there regarding cat5 as speaker cable?

Ryan, yes as Bob notes there are probably yottabytes dedicated to discussing the whole cable thing - to no final conclusion, but if you have tons of CAT5 lying around, in less time than it takes to find and read the first 10 pages thereof, you could simply try some out and hear for yourself.

I'd start with isolating a single of the 4 jacketed pairs and go from there.
 
frugal-phile™
Joined 2001
Paid Member
That cat5 cable thing is fascinating. I have a ton of that lying around. For a longer run do you use multiple strands of the cable per polarity? I would love to hear technical information as to why these cable sound better than the typical multistrand. Is there a dedicated thread out there regarding cat5 as speaker cable?

I personally feel that there are real differences between cable, but the technical arguments are in dispute (ie Dr Malcolm Hawksford vrs those that say he makes some errouneous assumptions). The field is full of snake oil mixed in with a smattering of sincerity. What works best is very system dependent (at least partially due to changes in the amplifier induced by the cable/speaker interaction)

So i just stay out of the minefield debates, and stick with CAT5 because it undisputedly has great bang for the buck (hiding behind my frugal-phile(tm) title).

I have been exposed to many an informal cable comparison, i was in retai at a leading hifi shop in the early days of the cable wars. We have done listening tests that have led us to single strands, better than more (in our systems)

dave
 
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