ML Vista Crossover Bypass

[InterMechanico]

https://www.madisoundspeakerstore.com/mundorf-10-watt/mundorf-0.47-ohm-metal-oxide-film-resistors/

Here's a 0.47 Ohm 10W you could use. I would stick with something in the 0.47-0.5 Ohm range as the original. You can get away with a 10W power dissipation resistor here (like two 5W 1 Ohm in parallel), as 20W is a bit overkill.
(As I was just guessing before, I hope you have checked to make sure that is the actual resistance in series?)

Thanks Tosh. I haven't checked yet, but I definitely will do so before I make the change.

 

[InterMechanico]

OK! I have completely disassembled one of my Vistas. If anyone is curious about anything at all, now is the time to ask.

Tosh. I measured the resistance of the step-up transformer. Value is 0.8 ohms.
I've traced and tracked the printed circuits of the crossover, and I think the relevant resistors are (3) 20W1R0J 's (R5, R6, R7) wired in series from the black binding post before the balance of the coils and capacitors that make up the rest of the network. I'm drawing a diagram of the whole thing now. I'll post it when it's complete.

 

[InterMechanico]

Vista Crossover Diagram- Drawn by a Monkey (ME!)

Okie Doke, It's complete. Here it is:



I'll readily admit that I don't fully understand what I'm looking at. My guess is that I need (3) 20W1R0J resistors in series on the negative side to protect the amplifier. Given the Step-Up Transformers' resistance of .8 ohms, That would make 3.8 ohms total resistance in the circuit, close to a happy 4 ohms. It will fluctuate with frequency, but it wouldn't drop below something greater than 3 ohms.

I'm building different cabinets and using different woofers for this project.

Woofers will be ScanSpeak 23W4557-02.
Enclosures will be as follows:

Width Overall - 10.5 inches
Inside - 9 inches

Height Overall - 16 inches
Inside - 14.5 inches

Depth Overall (bottom) - 17.5 inches
Inside (bottom) - 16 inches

Depth Overall (top) - 14 inches
Inside (top) - 12.5 inches

It will be a sealed design. Total Volume will be +/- 1 Cubic Foot. Adjustments will be made to accommodate woofer volume and other components.

Preliminary Sketch:


I know you're as excited as I am.

 

[Tosh]

R1 (also 0.5 Ohm) is the one to leave in circuit with the step up transformer.

 

[InterMechanico]

R1 (also 0.5 Ohm) is the one to leave in circuit with the step up transformer.

Thank you, Tosh. I'll build the circuit that way. Very much appreciated!

 

[Tosh]

The ScanSpeak 23W4557-02 woofer you mentioned only has a sensitivity of 82dB (and that's with 2W, not 1W), so more than 6dB less than a more typical 10 inch mid-woofer. This means you will need at least 4 times as much power to push it to the same levels. 1000W into 4Ohms class D amp?

Here's some things to consider for your new cabinet:
-Ensure the panel height can be adjusted for rake and height so the middle of the panel is pointing to your ears.
-Think about a separate enclosure for the electrical stuff, so they are not pounded by the bass pressure inside the cabinet.
-Use a brace to tie the sides together, and also brace or stiffen the front baffle (preferably to the rear panel).
-Locate the woofer toward the top of the cabinet to reduce floor bass reinforcment and avoid the unsupported weakest middle part of the baffle.

 

[InterMechanico]

The ScanSpeak 23W4557-02 woofer you mentioned only has a sensitivity of 82dB (and that's with 2W, not 1W), so more than 6dB less than a more typical 10 inch mid-woofer. This means you will need at least 4 times as much power to push it to the same levels. 1000W into 4Ohms class D amp?

Here's some things to consider for your new cabinet:
-Ensure the panel height can be adjusted for rake and height so the middle of the panel is pointing to your ears.
-Think about a separate enclosure for the electrical stuff, so they are not pounded by the bass pressure inside the cabinet.
-Use a brace to tie the sides together, and also brace or stiffen the front baffle (preferably to the rear panel).
-Locate the woofer toward the top of the cabinet to reduce floor bass reinforcment and avoid the unsupported weakest middle part of the baffle.

I actually wanted to ask you a number of questions regarding the different woofer options, if you don't mind. The enclosure information is great, Tosh. Thank you. I will keep all those things in mind. I'll post the rest of my queries tonight when I get home.

 

[beek]

Vista redesign

Just my 2 bits on the cabinet and My pet peeve, design the cabinet so that 2 or 3inches of the lower stat that fires into the front of the
original cabinet fires into free space, also have the slope tilt down instead of up to avoid diffraction..................

 

[Tosh]

I would go with two 8's or 10's (depending on how much bass you wanted) in each cabinet, mounted one on each side, back to back, for force cancellation in the cabinet. I wonder if the high xo point of Vista (450Hz) would allow that to sound OK vs front facing...

 

[InterMechanico]

Just my 2 bits on the cabinet and My pet peeve, design the cabinet so that 2 or 3inches of the lower stat that fires into the front of the
original cabinet fires into free space, also have the slope tilt down instead of up to avoid diffraction..................

I know what you mean, and I'm definitely going to try to drop the height of the cabinet to the level of the crossbar at the bottom of the panel. The issue is trying to design an aesthetically pleasing enclosure that's still large enough to accommodate the woofer (s). The dimensions posted above are the absolute minimum height allowable without altering the bracketry the attaches the panel to the woofer enclosure.

 

[InterMechanico]

Just my 2 bits on the cabinet and My pet peeve, design the cabinet so that 2 or 3inches of the lower stat that fires into the front of the
original cabinet fires into free space, also have the slope tilt down instead of up to avoid diffraction..................

I know what you mean, and I'm definitely going to try to drop the height of the cabinet to the level of the crossbar at the bottom of the panel. The issue is trying to design an aesthetically pleasing enclosure that's still large enough to accommodate the woofer (s). The dimensions posted above are the absolute minimum height allowable without altering the bracketry the attaches the panel to the woofer enclosure.

 

[InterMechanico]

I would go with two 8's or 10's (depending on how much bass you wanted) in each cabinet, mounted one on each side, back to back, for force cancellation in the cabinet. I wonder if the high xo point of Vista (450Hz) would allow that to sound OK vs front facing...

It's funny that you should ask about two woofers, because that is exactly the hair-brained scheme that I was going to bug you about. Here's the thing; after you mentioned that there is an issue with the efficiency of the 23W/4557 02, I got to thinking about different options. That driver was attractive to me because it would work so well in a 1 Cu.Ft sealed enclosure, which is ideal for the Vistas' 10.5 inch wide panel. However, I had not realized how much extra amplifier I would have to make available to make it work. Anyhow, the thought process then had me wondering about a smaller Summit configuration, whether it would be too complicated, or fairly easy to design. I will be powering the speaker with MiniDSP PWRIce-250 plate amps. I had originally intended to use one per speaker (2x 250 watt with DSP), but if I incorporate another woofer into the enclosure, I'll need another channel of amplification.

Question 1: Could 2 identical 8 ohm woofers be installed in a 1 cu.ft sealed enclosure, wired in parallel (one wired out of phase) to use the same amplifier channel and crossover point?

Question 2: If I intended to use three channels of amplification per speaker, would there be a Sonic Incentive (just made that up) to use different woofers and different crossover points to limit each woofer to 200 hz of bandwidth? Could they still be wired out of phase to make use of the same enclosure, or would they need to be isolated within the enclosure?

Question 3: How much negative impact would a smaller than ideal sealed enclosure have on sound quality?

Question 4: Regarding side mounted woofers. It hadn't occurred to me to mount them in that fashion. Can you elaborate on the benefits? One obvious advantage is the ability to use larger woofers without worrying about being right on the edge of the enclosure.

Question 5: Woofer recommendations. Given my very limited experience with this kind of project, any suggestions of specific woofers that may work for this project would be much appreciated. I have a woofer budget of roughly $1000.00, but audio being what it is, that number is somewhat flexible.

Note: Amplifiers will be mounted in separate enclosures. Panel power supply was still going to be installed within the woofer enclosure, but I could certainly mount it elsewhere if necessary.


Thanks Guys!

 

[Tosh]

You are going to need to develop a bass philosophy of your own. Look at what Siegfied Linkwitz does in the bass. Short version (in order of perfection): Dipole or Sealed. Maybe you like Sanders, then maybe TL bass? But it sounds like a cabinet in the 1 cu ft range is your goal? Then maybe an isobaric type cabinet suits you better? (Two woofers, half the cabinet volume, see pic)

These days my own bass dreams revolve around some convergent evolution (and pricing) in 12 inch woofer offerings from Madisound:
https://www.madisoundspeakerstore.c.../peerless-835017-xxls-12-aluminum-cone-4-ohm/
or
https://www.madisoundspeakerstore.c...s/scanspeak-discovery-30w/4558t-12-subwoofer/

The Peerless has a tiny edge in Le, but it's very close between them otherwise!

Two per side, in either dipole or sealed. 4 serious 12 inch woofers for ~$250 each. That's how I'd spend your $1000.

 

[InterMechanico]

Thanks Tosh. I was tempted to go with the two 12s per speaker, but I think that's a little bit much for my little Vistas. You suggested I use my imagination, so I'm working on a multi-angled enclosure that maintains the style of the ML Hybrids, and also provides enough volume for my selected drivers (still humming AND hawing). The design will incorporate a front firing 8" woofer covering 150-400 hz. and a rear firing 10"subwoofer handling everything lower. The enclosure will be split with both compartments sealed. I've ordered a 4' x 8' sheet of 1.25" MDF, and I'll need another amplifier module as well. I'll post a clear drawing when it's complete. The driver short list is:

a) Seas L26roy04 (rear firing) https://www.madisoundspeakerstore.com/approx-10-subwoofers/seas-l26roy-10-subwoofer-d1001-04-4-ohm/ and Seas W22EX001 (front firing) https://www.madisoundspeakerstore.com/approx-8-woofers/seas-excel-w22ex-001-e0022-8-magnesium-cone-woofer/

b) Dayton Audio RSS265HF-8 10" (rear) http://www.parts-express.com/dayton-audio-rss265hf-8-10-reference-hf-subwoofer-8-ohm--295-442 and Dayton Audio RS225-8 8" (http://www.parts-express.com/dayton-audio-rs225-8-8-reference-woofer--295-356

Honestly, I'll most likely go with the SEAS units because they fit my design just right.

I will have to finish the enclosures at some point, and I'm 95% set on this color:
http://www.bing.com/images/search?q=bugatti+light+blue&go=Submit+Query&qs=ds&form=QBIR#view=detail&id=1C00A48E91AB1A6322D8A2CF2DBA26A8DE58F728&selectedIndex=15

 

[Tosh]

Pretty ambitious as what you've described is essentially a 'mini active Prodigy'! But no sense using a 10 inch car sub if you don't need to? Big bass comes from big drivers...

I was tempted to see what that Seas W22EX001 (also used in Orion) with that size panel (9.3 x 40 inches) might look like (behind is SL3). As much as I like cobalt blue, it's too much visual pop for my somber taste.

I'm going to continue selling just one type of driver below ~350-400Hz (check your panel's FR?) and I'll try to show a concept of the two 12 in woofers in an isobaric so you understand that it's not "a little bit much for my little Vistas."
Does it need to meet a certain WAF? What are your goals and constraints?

 

[InterMechanico]

Pretty ambitious as what you've described is essentially a 'mini active Prodigy'! But no sense using a 10 inch car sub if you don't need to? Big bass comes from big drivers...

I was tempted to see what that Seas W22EX001 (also used in Orion) with that size panel (9.3 x 40 inches) might look like (behind is SL3). As much as I like cobalt blue, it's too much visual pop for my somber taste.

I'm going to continue selling just one type of driver below ~350-400Hz (check your panel's FR?) and I'll try to show a concept of the two 12 in woofers in an isobaric so you understand that it's not "a little bit much for my little Vistas."
Does it need to meet a certain WAF? What are your goals and constraints?

It has certainly morphed into something bigger than I had first intended. Mini Prodigy? Maybe, if it all works out.
As you know, the original plan was to just go active with the panel and woofer using MiniDSP ICEPWR 250 plate amps. I have yet to complete the panel conversion to active because I'm waiting on some resistors from Solen.ca.

The original x-over frequency of the vista is 450 hz. I'm going to TRY and go much lower. The vantage has the same panel and is crossed over at 400 hz. The FR of the step up transformer is 250-20000 hz. I wont get near 250, but maybe 350ish... I won't know until I try and measure the results.

The reason for the woofer re-design is simply a desire to keep the otherwise un-touched Vista woofer cabinet assemblies complete and functional. The original cabinet is not suitable for upgrading IMO. With the stock 8 inch woofer covering such a wide range, it just doesn't satisfy me. I have been looking to upgrade it in some manner for over a year. Anyhow, as long as we're building a new enclosure, why don't we just build the very best we can, right? One important requirement for me is to not have a front firing woofer that is wider than the panel frame (10.5 inches). I thought about the side firing design you had mentioned, but I worry about sound localization being a problem. While the Isobaric will undoubtedly produce a fantastic bottom end, I run into width behind the panel or localization problems given the range to 350-400 hz. My initial solution to both problems is to use a high quality 8" forward firing woofer that fits well behind the panel frame , and have it cover the frequency range between the lowest panel frequency possible and the frequency at which point localization stops being an issue (something like 180hz?). That's where the rear firing 10 inch Seas Submawoofer comes into play. It is very comfortable in a sealed enclosure of .6 cu.ft, which is exactly what I have room for behind the panel (not including the portion for the forward woofer). The x-over points will be adjustable, of course. I could put a 12" inch in its' place, and I could make a little more room in there. It's a definite possibility. I will be taking a closer look at options as the enclosures begin to take shape.

I will briefly describe the enclosure that I've come up with. It continues to evolve.

-Depth @ base: 17.5"
-Height :16" (to panel bottom (crossbar))
-Width @ front: 11.5"
@ rear: 15.5"
-angle of front baffle: Back at top 1"
- rear baffle: towards front of speaker 2.5"

I don't have any drawing programs on my laptop, so I will post a sketch:



This post may be a little Bo-Jang and hard to follow, for which I do apologize. I've ben at work for 14 hours and need to sleep for a few.

 

[InterMechanico]

WAF is not an issue. We're all good there

 

[InterMechanico]

Pretty ambitious as what you've described is essentially a 'mini active Prodigy'! But no sense using a 10 inch car sub if you don't need to? Big bass comes from big drivers...

You mention that the L26ROY is a car sub. What is the identifier or physical difference (other than funny symbols and names)?

 

[|Tch0rT|]

You mention that the L26ROY is a car sub. What is the identifier or physical difference (other than funny symbols and names)?

Usually car subs have a high resonant frequency (Fs) like ~30hz because cabin gain boosts the low end. That L26ROY looks like it would work well in either a car or home, especially for music (FS is decently low at 22hz, it would roll off the low end for the ultra low frequencies that the HT guys like). Though I wouldn't suggest building the subs into your towers. The best place for you sub isn't necessarily the best place for your towers and vice versa.

 

[InterMechanico]

Though I wouldn't suggest building the subs into your towers. The best place for you sub isn't necessarily the best place for your towers and vice versa.

Thank you for your insight. Regarding the inclusion of the Subwoofer into new woofer cabinet, the goal is to build a more comprehensive botton end to the Vista, rather than gain earth-shattering bass. I want to end up with a complete and clean spectrum from 35 hz (or so) to the crossover point for the panel (yet to be determined), to produce those frequencies at less than 100 db, and include all of that into the enclosure that the panel is mounted to. Everything will be DSP controlled, so I will be able to fine tune the end result. The enclosure will also be substantially heavier than the original, and I may experiment with some form of mass loading if enclosure vibration is excessive.


Edit: When I say that each enclosure will be substantially heavier than the originals, I now know that I mean roughly 75 lbs each. Anyone ever tried to pick up a sheet of 1.25 inch MDF? 154 lbs