beginner questions for a vott system build

[JD.]

Hi, first post here. Trying to get my bearings on doing a Voice Of The Theatre project, as I acquire the components.

Couple questions about the acquisition --

• presume I can take along a multimeter when going to purchase horns or bass drivers; what ohm range am I looking for, to check 8 ohm or in 16 ohm drivers?
• additionally, in the case of a seller not having equipment on hand, can I just take along an old receiver, and run down the bass to test the hf drivers, or run down the treble to test the Lf ones --?-- just at very low volume, to confirm operation by ear?
• is there some simpler, safe way to check out prospective component purchases..?

Longer range-- trying to map out the project, and I'm thinking it may come to whatever the used market is offering, at least for the time it takes to put everything together. But let's assume I have cabinets, and can source a pair of altec HF drivers + horns, of the appropriate vintage, for vott use. While waiting for the exact-appropriate matching altec bass drivers, I'm wondering if I might find some generic bass speakers (or even wide range bass-capable ones)-- there seem to be many Jbl ones around these days-- to use as a placeholder while the hunt continues for the real-deal ones?

Seems like the Altec Hfs + Horns should come first, as they are the less common grouping out there on the market. (Also that it seems simpler to supplement that, with 5/8ooHz and down generic gear, than getting the bass drivers first and having all that 5/8oo-and-up --to try to supplement.)

I guess any of this implies having an adjustable crossover-- that would be part of the plan anyway. (And also implies the 'placeholder' bass drivers would be high sensitivity and suitable impedance)-- but given all that-- can a cheaper, more-available substitute work for the time it will take to source the right stuff...?
Thanks for replies.
JD

[JeffW]

The multimeter will tell you if the voice coil is decent, but not the condition of the diaphragm itself - buying old used stuff is a crapshoot. The DC resistance of the coil, assuming they are in decent shape, should be a little less than the rated impedance, maybe 5 to 6 ohms for an 8 ohm driver and 10 or 12 for a 16 ohm (just rough estimates here). Zero could mean the coil is open, or maybe the coil is fine and the lead is just undone, hard to tell in a compression driver without taking it apart. Really low DC resistance could mean the coil has fried and the windings have shorted together. Even if the resistance checks out, you still might end up with less than stellar drivers (shattered diaphragms, worn out or seized up suspensions), but you might also land some gems.

Maybe others will weigh in with their opinions on the rest of your quest.

[Earl K]

WOOFER Substitute :

A very reasonable stand-in for the Altec woofer would be the Eminence DeltaLite 2515 II ( 15" ).

It has good efficiency , sports a large VAS like typical legacy Altecs , has a lowish MMS like Altecs, & has a low enough EBP figure ( allowing decent bass response ) .

It's used by the DIYSG designers in the Fusion15 , which is noted for having good tone .

PORTABLE TEST Setup :


Your smartphone running a simple test tone app. like ( using pink noise, or white noise even distinct solo frequencies )

> plugged into a small portable ( & cheap ) amp like the :

Lepai LP-2020ti

> with it's output filtered through a 12uF capacitor ( for protection of the HF unit being tested )

> would certainly inform most about any audible problems in a compression driver .



PS 1; Make sure you buy 802's ( not the smaller magnet 806 driver ) unless you plan on adding a tweeter .

PS 2; Typically the DCR of an Altec HF driver is around 3/4 of what the label says .

[JD.]

Thanks for responses.
More questions....

• presume a good continuity test on hf driver but breakup or distortion on listening test would indicate good voice coil but issues with diaphragm.. thought I read somewhere that replacement diaphragms for the common altec/jbl drivers were still being made, or were made up until recently. If so, does that mean that a diaphragm issue isn't necessarily a dealbreaker?

• I've read in a few places about putting the capacitor on the hf drivers to deflect dc reaching the coil... is that across the +/- terminals or in line on plus or minus feed? Is the 12uf value going to be right for both 8 or 16 ohm drivers? (and does that just stay on there permanently? is there a consequence for sound? just asking since the whole effort with independent amps/drivers plus outboard crossover seems to be about removing any passive gear btwn power-amp and driver..)

• Also read somewhere that with transformer-coupled tube amp that dc is not an issue. So while the protection cap would be good for evaluating the horns with unknown or convenient amps, once you've got it in the (tube) system, you could remove the cap...?

Thanks again for responses

[Earl K]

Hi,

• Genuine replacement diaphragms are available on eBay from GPA ( click the pic for the link ).

- Don't buy anything else ( ie; Chinese knock-offs ) unless you like under-performing parts .

• The 12uF cap is put in series ( inline ) with the positive terminal of the HF driver .

• With any amp. ( tube or solid state ) once you have a passive crossover in place, the HF gets all the protection that it needs ( apart from it being over-driven ).

[JD.]

So it would appear that legitimate diaphragms can be had. Nice to know.

I'm still obviously just lining this up. Wonder if anyone has their fave 'how to' or overall project articles on this. Seems fairly elaborate at first, if you're planning the multi-amp and multi-outboard-crossover path.
A fair amount to ingest, it seems, when you're getting info only in bits and pieces.

Is there a preferred 'project' article or diy faq about Vott system build that I'm missing? Specifically outboard-xover type.

Thanks
JD

[Earl K]

This pdf VOTT overview (might) help ( though, it's simply one persons opinion as to what works best ).



alancohen (s) thread New Heathkit-AS101 Owner is worth reading .

As is his thread called ;
Bringing 828 Cabinets Up-To-Snuff

Pano's thread is a worthwhile read; My A7-500's - a Journey

[emilime75]

When I went out to purchase a CinemaArray system from a Craigslist seller who was moving and didn't have other equipment to test with, I did something similar to what was suggested by Earl K. I made a little test board using a scrap piece of plywood, an amp module and a MiniDSP that I had on hand. I screwed all the components to the plywood board, wired them up, and used my phone as a source. I setup the DSP ahead of time to output certain frequency ranges from each output, along with a full range output since these speakers did have a passive crossover. It was quick and easy to hook up and run the speakers through a test.

Since you're looking to test singular drivers, and not systems with passive crossovers, the simplest solution would be any passive crossover close to where the drivers need to be crossed, a cheap little amp, and your phone as a source. The crossover would provide the protection needed, and the amp could even be battery powered if you're meeting a seller outside of an area with AC power.

[JD.]

This pdf VOTT overview (might) help ( though, it's simply one persons opinion as to what works best ).
alancohen (s) thread New Heathkit-AS101 Owner is worth reading .
As is his thread called ;
Bringing 828 Cabinets Up-To-Snuff
Pano's thread is a worthwhile read; My A7-500's - a Journey

Thanks again Earl. Great source material there, especially the threaded project-journals.
J.

[JD.]

Since you're looking to test singular drivers, and not systems with passive crossovers, the simplest solution would be any passive crossover close to where the drivers need to be crossed, a cheap little amp, and your phone as a source. The crossover would provide the protection needed, and the amp could even be battery powered if you're meeting a seller outside of an area with AC power.

Thanks. With the addition of the 12uf protection cap on the plus line of the hf driver, it sounds like I could use any source + amp that is portable for evaluation.

Tell me-- with the protection-cap in place, would it work to take an old receiver, with which I could roll off either the highs via tone controls, for the bass driver test or the lows via tone controls for the horn test ...?
Seems a simple source + amp to take along, and I have an old 1o-watt receiver that would seem just right ....?

JD

[JD.]

Bigger picture:

Basically I'm just testing waters with a Vott setup. I have the full vintage driver system going already with Tannoy Golds in my full system-- though that's with standard passive tannoy crossovers in the speakers.

But like everything in audio : My space is almost big enough to allow another system for now-- and a super-minimalist mono high-efficiency system seems worth investigating. This would go into a workshop area and I thought that it might be intriguing to go ultra low wattage, super-simplified mono. It has always struck me as the most-purist way to do amplified sound.

By which I mean Source> Crossovers w. Level controls> Amps> single Altec vott, in simple two-way biamp configuration. I'd use my present 5-watt triode-wired-kt88 2-channel amp for highs + lows. I'd like to be driving the Altec drivers with nothing between amp and drivers. If this seems successful I think I might try an even lower-wattage pure triode-DHT build at some point, for something around 2 watts.

With the tannoys I've learned the importance of alnico drivers with tube amps, and having efficiency-friendly speakers to match the style of stripped-down SE amps-- and the Votts look right for that, done correctly. A trial-run setup, with workshop-suitable sources (an fm tuner and/or a computer source- both configured mono-- could both provide all-day program material without flipping records or changing discs) is the idea. Also hoping to find some deals out there due to most prospective users wanting matched pairs of speaker drivers... no such worries with mono.

[Earl K]

Tell me-- with the protection-cap in place, would it work to take an old receiver, with which I could roll off either the highs via tone controls, for the bass driver test or the lows via tone controls for the horn test ...?
Seems a simple source + amp to take along, and I have an old 1o-watt receiver that would seem just right ....?

Sure, any old portable receiver can help you test the components .

[JD.]

Sure, any old portable receiver can help you test the components .

Thanks for the help.