Why don't you ask Steve?  I'm sure he'll give you the most direct and likely best answer.

Thank you for the response and information, That helps a lot.

I am aware of the Altec 416 driver.

I do have TWO, pairs of 15" drivers available to me:

First Pair: Eminence 15" Magnum LO drivers with the following published specs:

Fs: 37Hz
Qts: .45
Qms: 9.4
Qes: .48
Vas: 5.76 cu ft
Xmax: 7.9mm
Re: 4.9


Second set of 15" drivers, Eminence 15" NOS, not sure of the model, but measures T/S parameters are:

Fs: 27
Qts: .166
Qes: .169
Qms: 9.4
Vas 8.2 cu ft
Xmax .359"
Re: 7.6
94 db
200 watts
This driver has a usable FR to 800 Hz

Any opinion on the above drivers ?

The Altec may give additional mid band response to allow better intergration with the mid range horns I am building. Hope to use the bass bins up to 500 Hz, crossed to the mid horns

Tried to attached a few construction pics of the mid range horns I am building. usable frequency for the horns is 500 to 3,500 Hz
Not sure if the pictures were uploaded or not.....?  


Tom R

Thanks - Yes, the mid horn are taking some time to fabricate

Need to learn how to down size pictures......

That should have been the obvious choice as the Eminence Fs does not go low enough to get into the 20's

Just for my knowledge, are you not concerned about the very low Qts, and the drivers ability to reproduce the 1st octave in a large enclosure ? Or, is the horn such a good acoustic impedance matching device that a high Qts is not a concern ?

Please advise,
Tom in Lafayette

Mr Steve,
If I only use one driver per cabinet, should I decrease the size of the enclosure, or keep the same dimensions as the plans ?

Purchased your Imperial plans the other day, when I finish my mid range horns, I will start on the Imperials


Tom in Lafayette

I have read the Big Betsy Thread with interest. Your description of the speaker is enticing. The F15 has a FS of 49, so if used in the Imperial cabinet, it would not reach the lowest octave.

Would this make a good case for two different drivers in one cabinet?
The F15 and a 15” sub driver that could cover the lower frequencies?

Run the F15 at full range, with a simple high pass on the sub-woofer….something like that ?
A plate amp on the sub-woofer, cut off at 80 Hz to the F15 running full range on a separate amp?

Could they operate out of the same cabinet without issue?


Tom in Lafayette

Understood - Thanks

Tom

I am doing the same thing.  I have the f-15`s but nowhere to build until a month or two down the road.  We should start a thread on our experiences.  I took a look at the plans todat and they are for double drivers so some (UNCLEAR) adjustments will need to be done

FarmBoss,
Looking at the Decware drawings, I would propose substituting the center solid "B" style for a "A" style brace with the cut out for a driver. So that would mean you need to fabricate 3 of the "A"style, and 2 of the "B" style.

My best guess at the moment.......


Tom in Lafayette

Congrats on the Imperial build!  

Using the "A" style brace for the center is what we do when these are built for a single 15 inch driver, and then modify the front panel accordingly.

Quote:


Yes, this creates a joint with more surface area enhancing the strength of the glue joint.  

Waste is easy to deal with as you begin to complete the cabinet you can find so many places to add cleating and braces.  Just use the waste to further beef up the cabinet.



Steve

Tom, If you build one cabinet with the single driver, and one with the three way, and compare them to find which you want to go with; that would be an interesting comparison.

Brian

Ok I have a question on reading the plan.  It says part D x 2.
Does this mean the two seperate braces or does it mean make them double thick?

I am assuming we are still wourking with 3/4 stock.  The braces as shown on the left (front) diagram sjow two D braces but appear to be about triple the width of a 3/4 part.  
plan says 1 to 12 ratio.  That can't be right as it would equal nine inches wide.

So bottom line, what it the depth or maybe the width of part D?

Thanks

I worked all weekend and have almost fin8shed the first one.  As far as the brace D goes I have decided it is three 3/4 ply wide.  Now I am wondering about the optional brace E.  I think it should only be one 3/4`s wide but maybe 2?

I don`t know if this is the first Imperial with the F-15 driver ever made?  I have it hooked up to a Fischer console in my workshop.  The Fischer is 20 watts.  At first I was a little underwelmed.  It sounded a bit bright and shouty.  It was also lying on it's side.
Something really cool happened after 3 hours or so.  I put on Santana and turned the volume up pretty good.  The sound changed and it was quite remarkable.  This speaker hooked up to that old amp really rocked.  I have not heard the low notes like this on any home system.  I have had a few subs and this 8s nothing like those.  The bass and kick drums sounded real and loud but not at all muddy or thick.  THESE ARE REALLY GREAT SPEAKERS! I can only imagine how great two of them will sound on my ZMA systerm.  This is on a stereo I paid $98 for.  Incredible

FarmBoss,
Having a look at the drawings and optional brace "E", you will need two pieces at 3/4" thick, I believe the "E" braces are mated to the forward edge of the side panels, as you look at the front of the speaker cabinet.  The double of the forward edge thickness will help stiffen the large side panels.

At least that is what I see.....

I need to get my F15's up and running so they will be broke in when I get the Imperial cabinets built......


Tom in Lafayette

A wonderful report! That sounds like really excellent sound.

Brian

I have a few questions:

Any pictures of your set up ?  I am being challenged by the 1000kb picture limit I will see what I can do

I assume to Pendragons are a Tecton speakers? Yes mine have caps upgraded.  I have nothing but praise for these

How was the bass with just the F15’s, any idea of how low the reach ?Bass is awesome very musical.  I had no idea how much music I was missing.  I am afraid I do not have a good test record to measure but I can not imagine anything missing.  I only added the Pendragons because I had them and my room is somewhat challenging.  

I hope this shows how difficult this space is

I like that the ceiling is tall, I like that the space is well lit.

Brian

Hello SteveB,
Wow - You got some bass there !

What drivers are you using, crossover points?

Do you hear any bass drop off or difference between the standard bass cabinet and the smaller split cabinet ?

Are you happy with the Imperial build ?


Tom in Lafayette

https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1563222472

I really like them but I may make some changes. The driver boards are not removable. They are not perfect but they are well worth having

Additional photos and a response plot,  bass unit not not included







Tom R

I think both the F15 and Fast-15 Lii-Song drivers would sound incredible in these cabinets. And the F18 would also be fully realized.

Something for audiophiles who build these cabinets for their medium sized listening rooms, is that we typically flip them upside down with the horn mouth on the floor and then run the full-range driver of our choice.  We make the baffle removable and run everything from 10 inch to 18 inch drivers in the same horn with no modifications.

And halving the Imperials is a very good option for more modest size rooms.  We were able to cover the sub bass for a typical sized dance floor with a single 12 inch driver in a half-imperial, so certainly a pair of those in most listening rooms would be borderline overkill in bass output.  But you could run any size driver in those that you want up to 15 inch.  As a full-range speaker flipped upside-down it lends itself to the 10 inch full-range drivers and can work equally well with the 8 inch or really even smaller if the Qts of the smaller drivers isn't too low and even if it is, you will still get bass out  of it that shouldn't happen.  Just limited power handling whereas the larger drivers that couple better with the horn gain amazing power handling from the impedance of the horn.  This is why it is possible to fill a large space like these pictures show and keep up with 2 inch compression drivers which are 110dB or so efficient with a single 15 inch driver!  

As much fun as we had with these using serious high power solid state, the real fun began when we shifted to tube amps, the largest being 120 watts. But even a 2 watt amp with the right drivers, like the Lii Audio would get loud enough to just start to fill this large space.   So having 20 watts or 40 or 60 can be a lot of fun.

I can't wait to show Paul these pictures.  He turned me on to the Jensen Imperial 1957 Speaker Plans book from his grandpa and it was he and I who build many of these cabinets and installed them in nightclubs and bars in the area and fully explored what was possible to get to happen in this cabinet.  He works at here as one of the senior amplifier techs and will enjoy it.

Steve