Ported M8n MTM designs.....

[Paul H]

Thomas, thanks again for your patience and help. I'd simply follow your instructions to the letter, but my wiring configuration is different.

I'm wiring the crossovers and zobel onto a single board, which fits into the pedestal base of the speaker. As a result some of the junctions (aka terminal boards) shown on the schematic disappear - they aren't required for one continuous board. The connections are still the same electrically of course, but some of the input terminals (ie 1A..4B at the zobel) are replaced with straight wire-to-wire connections.

However, if the zobel terminal in the schematic is as follows:
(+) input (1B), (-) output(2B), (+) output(3B), (-) input(4B)

and 3B is directly connected to 4B, then calling it a "+" or a "-" connection at 3B/4B becomes a matter of semantics, doesn't it?

Paul

[ThomasW]

They can be common/shared attachment points in the circuit.

http://home.comcast.net/~audio-worx/zobelXO.jpg

theAudioWorx
Klone-Audio

[Paul H]

I've got one crossover finished, pedestal bases built for both speakers, bracing for both speakers cut out and I'm ready to start assembly of boxes. Now if some idiot hadn't suggested curved sides on the speaker boxes I'd be done in no time. Wait, I was the one who came up with curved sides ops:

Still waiting as fast as I can for the M8N's - I ordered them 3-4 weeks ago, and the delivery date keeps sliding so that no matter when you check they'll always be due in a month.

Paul

[ksudar]

I am also waiting for the M8N's... I can't imagine why they keep pushing back the arrival date when it's a new item. I'm about to just cancel the order and get the M8a's, which appear to be in stock. Maybe we should raise some hell over on the PE message board? :B

[ThomasW]

I talked with Bev in the PE wholesale dept. She stated that regardless of what the online order page indicates, the M8a's aren't available. They've been discontinued by Hi-Vi. And that PE simply hasn't updated their website to reflect the situation.

When I complained about the M8n situation, she said that it's was completely beyond their control. It's Hi-Vi that gives them a date, then keeps pushing it back and back.

[Stevepaul]

I have 4 M8n's and 2 SS9800 tweets for sale

Hey Guys,

I had plans on building the ARVO project dipoles, but unfortunately, the timing chain in my 2002 Alero snapped....which, in turn, allowed the pistons and valves to get nice and intimate with one another. The cylinder head didn't like the any of this and decided to crack....thus, my $1500 play money for the ARVO's just went to a new cylinder head replacement. :M

I am forced to sell the speakers that I have accumulated for this project.

I will sell the 4 M8n's for cost....$48.70/ea and I will pay for all shipping anywhere in the US. Not a great deal but at least you will get them and you won't have to pay shipping. Three of the woofers have never been pulled out of their packaging. One woofer was pulled out and viewed...never hooked up.

I also have 2 ScanSpeak 2904-9800 metal dome tweeters that I purchased from Paul Hilgeman over on the Madisound forum. He tested them and played them very little. I haven't tested or hooked them up. I will sell them for $280/pair and will pay for all shipping to anywhere in the US. If there are any problems with the woofers or tweeters, I will give your money back and pay for shipping back to my house.

I'm bumming about having to give this up...it'll take me another 8 months to save up the cash to build the ARVO's...but, I'll be back :T

Not sure what the forum rules are for selling items here....if there is an area on the forum where this is more appropriate...please let me know and I will go there.

Thanks
Steve

[ThomasW]

That's a bummer.............. ops:

You'll certainly have no problem selling the drivers.

I'll buy the tweeters. Email me with your address, etc, and I'll send out a check today.

Just to goof on PE, I 'ordered' 4-M8a via the PE website. I'm curious how long before they call and say they aren't available.

[ksudar]

Steve,

Are you willing to sell me just one pair of the M8N's? If so, I can send you the funds by paypal any time. I don't need all 4 as I'm doing the m8ta design.

-Karl

[JonMarsh]

Sorry to hear about your timing chain, Steve. I know the feeling, on a much smaller scale. My Z28 needs a new mass airflow sensor module, and that's going to cost me about $500 installed this week. :cry:

But those cars are a necessary part of our modern lifestyle, even though I use a train the last few years for commuting in the Bay area.

Good luck with the repairs.

~Jon

[Stevepaul]

Thomas...I have sent you an email at your audioworx address. I will send the tweeters to you as soon as I have the address you want me to send them to.

Karl.....I would really like to sell all 4 at the same time. If by Monday night, 5/3, nobody claims all 4, I will go ahead and piece them out 2 at a time. You are first in line.

This just bums me out......I've been talking about the ARVO dipoles to a speaker building buddy at work and he was saving a $70 bottle of single malt scotch for our initial listening session. I guess he'll just have to hang on to that bottle a little longer! :boozer:

I will still be hanging around the forum!

Best Regards,
Steve

[ksudar]

Steve,

I'll make things easy for you and just take all 4 of the M8N's - I may build another enclosure to test the mtm version as well. Let me know where to send payment. :B

-Karl

[Stevepaul]

Karl,

I sent you an email to your personal email account. Please read that and either call me this weekend or we can email on Monday, 5/3. My home computer is down and I won't be able to check email until Monday when I get back into the office. ops:

Best Regards,
Steve Paul

[Ten 99]

sorta off topic...

Jon,

Your last name sticks out to me as though I've seen it somewhere other than here and other audio forums.

Did you used to be on the F-body mailing lists years back or any of the forums for such?

That MAF sensor shouldn't cost you that much. And labor is nothing on these. Just a few screws that attach the hose clamps on either side, and a weatherpack connector to unplug and replug. We're talking 5 minutes tops.

Chris

[Paul H]

Way back when in this thead ....

So we're pretty close to dead on using 1" of centerline offset..

I just found the original pdf for the M8a, it's 215mm in diameter vs the M8n which is 222mm in diameter. So we'll need to compensate for that difference. This should only impact the offset placement of the tweeter.

But lets wait on finalizing the MTM driver spacing until Jon and I can sit down with a baffle diffraction program and rerun the system. This should have no impact on you starting to build the boxes. The holes for the drivers are usually cut after the box has been assembled.

Did you guys ever have a chance to look at this?


I've got the "wire-frame" built of the speaker boxes and will be applying layers of bendable plywood to the curved sides by the weekend. I should be posting some pics soon.

Paul

[ksudar]

As has been ask and answered numerous times in threads dealing with the M8a. The M8n is an exact electrical replacement for the M8a. The only difference is that the M8n has a larger cutout hole and larger diameter frame. The cones are identical, so any differences are a function of the photograph.

Thomas,

I just received my M8n's from Steve Paul (thanks again Steve!) , and the cones are clearly a bronze color, definitely not yellow like the pictures of the M8a that I've seen. Perhaps your test drivers were from an older batch before they switched the cone color, but I thought I'd mention it here in case anyone else was wondering.

[ThomasW]

Ours aren't exactly yellow, they're sort of a tan-gold. Color variation aren't surprising with anodized cones. Certainly won't have any impact on performance.

[Ten 99]

I wish they were charcoal or black, more like the TC 12" subs that you guys are trying. I know that it's only a color, and doesn't affect the way they sound, but that color that Hi-Vi uses certainly doesn't do much for wife appeal. ops:

I know that you can use a grille to cover them up, but I'd rather go sans grille, and just have some drivers that didn't stand out like a glowing ember. Oh well, minor complaint.

I don't guess anyone knows a way to die that cone a different color without having to totally take the driver apart and rebuild it. That would just be insane, and not worth it. Wasn't sure if you could just take some sort of a Rit die or the like, and whipe it over the cone surface or not. I once read an article on anodizing, and if I remember correctly, there is a sealer coat that is put on after the anodizing, so between the two, it's probably got a really smooth finish with little or no success getting anything into the pores.

[ThomasW]

Nope can't dye metal since it isn't porus.

Metal can be be plated (similar to anodizing), it can also be powder coated or painted. Painting and powder coating will change the Fs so not a good idea.....

If you're brave you could try coloring it with a black Sharpie. It would be quite difficult to get an even coat.

Another option would be to try what's called Birchwood Casey Aluminum Black. I have no idea what happens if the surface is anodized. Be extremely careful not to get any on the surround!

BTW the TC2+ cones are painted.....

[Paul H]

Photos of work in progress

I thought I'd try to post a photo of one of the speakers and the crossover with a 'bazillion' caps.

It's a pretty slow process. Like most of you out there I have a few little things cutting into my speaker building time - work, family, home






Paul

[Al Garay]

Nice work Paul. No need to feel guilty. Work and family and outdoor time in Spring time are important.

I am amazed by the number of components on the crossover. I can see how the cost of the crossover can exceed the drivers.

[JonMarsh]

Looks like you're coming along well!

I understant the time constraints- I'm fighting the same issues with finishing the current version of the Arvo Parts- plan on ordering the rest of the crossover components this weekend, after I figure out what I don't have and need.

That's been competing with an amplifier design project for "cpu cycles".

And work has been a terror the last two years- this month is the first I haven't been travelling three or four weeks in the month.

Keep up the good work, and keep us posted.

~Jon

[DeanP]

I have a question...why would a person use a bazillion capacitors when you can buy two 68s to make up the 136?(in the tweeter xo)
Did I miss something, as the cost of two is way less than multi small ones...
Dean

[ThomasW]

Madisound has 10uf GE caps that are $0.90US when purchased in lots of 100+ pieces

So possibly only for US builders, the out of pocket cost for building the large value caps from clusters of Madisound's GE 10uf caps, is approx 1/2 the cost of buying the larger value caps from Solen.

Other than lower cost, another benefit is that those cluster caps have EXTREMELY low ESR..........

Downside is the time and labor involved in their construction, combined with the HUGE physical size of the completed caps.

[Paul H]

The Madisound caps for the speakers I'm doing (2 main and a centre) worked out to $150Can cheaper total than Solen et al.

Also, the assembly looks more onerous than it actually is - good thing!

Paul

[DeanP]

The Madisound caps for the speakers I'm doing (2 main and a centre) worked out to $150Can cheaper total than Solen et al.

Is that after shipping costs? I know Solen only charges you actual Canada Post shipping costs,no handling costs whatsoever. :T
I'll definitely do clusters of some sort,but I thought my electronic skills were really baaad when I saw those massive clusters!

[ThomasW]

Paul's obviously done the math, given that he built his months ago. I imagine he has the exact costs available.

Regarding building the clusters, it's just a matter of hot gluing the caps together ,then soldering the ends of each side to a piece of tinned wire.

It is TON of work, and the clusters are HUGE. But they create an outstanding caps.

[Paul H]

Dean,

My order for 150 of these caps cost $135US, plus $26.55 shipping charge from madisound, shipped via US postal service at my request. I also paid 15% HST (on assessed value of approx. $180Can) and $5Can customs clearing charge.

Actual USPS cost for a box of this size and weight is about half the shipping charge noted above.

Note that customs clearing charges through most of the courier companies is substantially more (ie $30-40, ymmv) which is why I go USPS when I can.

Paul

[Paul H]

From PE's web page for M8N's:

In Stock? No, due 8/1/2004

Surely they must be joking ...

Anyone got a drop-in replacement for M8Ns ? :cry:

Paul

[Daryl Furkalo]

Well the Hi-Vi M8a is no longer called the Discontinued Hi-Vi M8a? I heard Andrew's M8's, got the itch, and have been waiting for them to be in stock as well.

[ThomasW]

I just got off the phone with Swan. They recently shipped 2 dozen M8ns to PE.

It may be that the reason they (PE) bumped out the date is because they sold out the 24pcs. So people that had the drivers backordered may get them.

I just called PE and said HEY! what's going on? Unfortunately I spoke to a voice mail box. So I'll let people know when I hear back from PE.

Also contrary to what PE has said the M8a aren't discontinued, and Swan have some in stock. They (Swan) have a retail price of $125.50. Now that's a bit high. So if people are interested I can probably create a wholesale account with Swan and get the drivers at lower pricing. I'd just sell them for what they cost me + shipping.

I'll post new info as I get it.

[Paul H]

I managed to talk to a real live person at PE just now who advised me that my order for 6 of these M8N's shipped out to me yesterday.

They do not have any in stock now, but if you had them on backorder they may have been sent to you already.

Waiting (optimistically now) as fast as I can,

Paul

[Paul H]

Near the beginning of this thread a length of 12" was suggested for the 4" port for tuning at 25 Hz.

My unibox model is giving me 9 1/4", and the precision port instructions indicate 9 3/8" (10 3/8" assembled length with flares). Should I use the 9"+ or am I missing something?

Thanks,

Paul

[JonMarsh]

Paul,

No reason not to go with whatever Unibox is telling you, but what's your "net" enclosure volume? This is the volume after subtracting for the drivers, port, crossover. This is what you would be using in Unibox calcs. Where I mentioned 4" and 12" long early in the thread was in regards to the M8ta, IIRC, base volume of the box before subtracting was ~68 liters. The M8ta has a box/port tuning of 22 Hz; this requires a longer port. But for a lot of typical program, and to get more port reinforcement in the 40-50 Hz area, moving the tuning up may be preferable. And the port is even longer (35 cm). As long as you've accounted for the net volume in your Unibox plan, go with what it suggests- you're doing an MTM anyway, right?

Regards,

Jon

[Paul H]

Jon,

I am doing an MTM, with a net volume of 125 litres, calculated in detail based on box areas and volumes from autocad and deductions for all drivers, framing, bracing, and port.

The crossover is outside the speaker. I've built a 5" high base for the speakers and the crossover sits inside it. This allows access to the crossover without taking apart the 'sound box', and I can access the L-pads simply by tipping the speakers slightly.

I haven't decided on exact tuning yet, but it will likely be 24 Hz based on what I see now from Unibox. Any lower than that and as you inferred the 30-60 Hz range starts dropping dramatically. I'll use Unibox/Precision Port's numbers for port length - they match very closely,

Paul

[JonMarsh]

Is your Unibox model using lined or stuffed cabinet? I recommend having stuffing behind the drivers, but not stuffing the whole enclosure.



With a low tuning, like the M8ta, the response is matched to the roll off in the room gain kicking in with proper placement, the net room response is pretty flat (hopefully!). In practice this usually works quite well.

I never tune for flat response from the enclosure anechoic, becuase this will produce a "heavy" in room response unless it's an usually large room that's unusually absorbtive.

Generally I've found the Unibox models to agree quite closely with the measured response; if you have any way to measure the impedance curve, you can check for the impedance minima corresponding to the tuning null.

Regards,

Jon

[Paul H]

Jon,

The back and side walls will be lined with 3/8" foam, and after I've got everything assembled and running I'll experiment with some stuffing behind the drivers only.

My unibox curve looks like the attached at 22 Hz:



Below 23 Hz the precision port instructions for port length calculations do not match unibox port lengths - should I use unibox lengths plus 1" to allow for the flare, or should I make an adjustment at all for flare?



Paul

[JonMarsh]

An extra in or two is easy to trim. If you're using the calc setup for flared ports as in Unibox, I've just cut them to the exact length, end of flare to end of flare. This seems to always get right on the money; it did with all the versions of the original M8.

If you have some additional box damping, your curve will probalby look more like mine, which works well in room; helps keep it from being a skosh heavy in the 50 Hz area. Of course, if you LIKE it a skosh "rubenesque" in the 40-50 Hz area (as some other people who's moniker inlcudes a T and a W do ), then don't worry. But my experience is that the mids are not clean and focussed enough without having the stuffing.

Besides polyester batting used for quilts and blankets, (which is great in the midrange) I've had good luck with Owens Miraflex; you can sometimes find it at big box stores, and it's not itchy to handle; gives better bass damping than the polyester material.

Regards,

Jon

[Paul H]

Thanks again Jon.

I've finished both crossovers. The cabinets are done except the 2 front layers, which are bevelled and cut to size but will only get installed after I get the M8N's (I want the drivers in my hands before I do the cutouts), likely later this week. The end is in sight!

For anyone considering building speakers this size (125L or 4.5 cubic feet interior net volume) with 1 1/2" thick walls, be warned that these are Heavy - moving and tilting them becomes a real chore in the last stages of assembly.

Paul

[DeanP]

YeeHa!!

I just noticed at Solen.ca(effective Feb 04) on their "News" page that they are carrying Hi Vi products again!
The M8a is only $79.60 CAN and $61.23 US...
Here I go now. :B

[ThomasW]

Dean,

Thanks..... that's GREAT news............. :T

[JonMarsh]

For anyone considering building speakers this size (125L or 4.5 cubic feet interior net volume) with 1 1/2" thick walls, be warned that these are Heavy - moving and tilting them becomes a real chore in the last stages of assembly.

Paul

Uh huh. Moving around my 68 liter M8ta's is no walk in the park, either; I shudder to think what your's are like, Paul.

Glad to hear you're making such good progress.

BTW, where's the pics? :W

~Jon

[Dennis H]

Wow! I wonder if they are actually stocking everything they list - basically the whole HiVi lineup - and if they will ship them to the US? They even have the elusive M12 listed for US$138. :righton:

http://www.solen.ca/pdf/hivusd.pdf

[JonMarsh]

Well, all very good questions- though as far as I know, Solen will ship anything to the US of A.

Ah, could it be, an example of M12 actually available in the wild?

I'm looking at the TC2+ which I have as an alternative for the RD50 system; the cone behavior seems pretty good up to 800Hz+ which means a 500-600 Hz crossover may be doable. The M12 looks to be impeccable to 1 kHz, but it only has about 1/2 the Xmax. For a four driver Array, the M12 might be better, as two in series should net an 8 ohm load with 93 dB senstivity, and another two in series in parllel would up the output- with some passive EQ in the network, the sensitivity might work out fine with the RD50, but there's really only one way to know for sure. Four TC2+ will give up at least 3 dB in sensitivity, but would play louder in the bottm end. The spider and surround design in the TC2+ is excellent; the M12 is an unkonwn at this point.

Still, all very interesting.

[Paul H]

BTW, where's the pics? :W

~Jon

Some pics here.












I did some baffle step modelling and came up with horizontal offsets of 3/4" to 7/8" from centreline for the woofers and about 2 5/8" the other way for the tweeter. This is very close to Thomas' suggestions way back in this thread, and will be likely adjusted very slightly to suit physical layout on the baffle. Also as Thomas suggested way earlier in this thread, I'm planning to use 11 1/2" vertical center-center distance for the woofers, with the tweet centred vertically in between.

I still need the woofers to cut the holes in the baffle - not here yet - but somewhere in North America there's a box with 6 M8N's on the inside and my name on the outside.

Paul

[JonMarsh]

Very nice work, Paul!

I can't hardly wait to see them finished! It looks like you may even top Tibor's construction and finishing job, and that's saying a lot!

Best regards,

Jon