apollo c51 s7 modification to add 077 tweeters and new crossover

[sidney8151]

I picked up a pair of apollo c51 s7 speakers last week. They have nice cabinets, so the cabinets stay. I will replace the surrounds on the LE15A's myself. I presume some of the crossover components are worn out, or at least slightly out of compliance. I have a pair of 077 uhf tweeters like for the L300, and I see that there is a revamped/reworked crossover design by Nelson Pass for the L300. I think the 077 tweeters would fit in best in separate boxes on top of the apollo enclosures. This project is just an idea, I do have the unused 077 tweeters, so that makes it a good idea.

basics
Would the apollo c51 benefit from building a stand for it to bring the horns up to ear level? ...or is there some floor bass resonance factor that makes the original design superior? I do live in an apartment and have always kept speakers up on milk crates to avoid projecting sound through the floor. I saw a thread here where concrete flat ?pavers they called them, were used. Suggestions as to height and reducing sound going downstairs, please.

the crossover
Does the Nelson Pass crossover look like a good design? Does the fact that my woofers are different, or that my enclosure volume is different, contraindicate the use of the Nelson Pass crossover? The L300 uses 136A woofers and I have LE15A's.
reference: http://www.firstwatt.com/pdf/art_l300.pdf

woofers
The LE15A's that I have are part of the most expensive apollo c51 package, the s7 package, ...yet I am hearing there are some much preferred woofers. I'll do some reading on "favorite/preferred woofers", but I think the LE15A's will be fine.

surrounds
Are the surrounds from Rick Cobb better than those from Orange County Speaker Repair, now Speaker Repair Pros?

So that's where I'm at on this project. Will soon order surrounds, and maybe build a wooden stand, maybe with double sides and sand in between, to firm it up. PS I love the transverse/sideways projection of sound by these speakers

sidney in Chandler AZ

[Mannermusic]

Basically, the L300 (4333) is a more "modern" version of the S7. It was done by chief engineer Greg Timbers in earlier times. If you want to do it, you gotta do the whole package - it all works as a system. Tons of lab work involved. Re the enclosure, you would have to re-tune for the new woofers. Also, the L300 uses a longer horn - HL92 - that, I assume, won't fit as designed (too long). You could probably squeeze the 077 onto the std baffle but I like your thot re putting it on top. So, the whole thing turns into an engineering exercise of sorts - it's not a bolt-in. Will have to sort things out, solder up the crossovers. Depends what you have in mind / skills, tools, time. Also, there is a complete thread in here done by a fellow who went through much the same exercise - selling LE15A's, etc. It worked out well, likes the result. Maybe he will see this post and chime in. If I see the thread I'll post it here. Good luck - others will add their thots. MM

[Earl K]

I like the size of those C-51's.

I'd first determine the volume of the enclosure before making assumptions that any JBL 15" woofer will work properly in it .

It looks a bit small .

If it's smaller than 4 cu' then I would try the le14a in it ( using an adapter board ) .

Since I prefer horns that I can look down the throat of, ( if mine ) I would also see if there's a way to retrofit ( non-destructively ) a small bi-radial ( perhaps by removing the knock-out plate that the current conical is a-fixed to ) .

I'm thinking something like this Eminence or Pi Speakers H290 ( B or C ) BiRadial as a starting point ( the 2 models are seen below ).





Just a bit of "Blue-Skying" for you.

[sidney8151]

I've been searching and reading here for over a man day now, and thank you all for the excellent reference material. It seems the woofer in my Apollos was used in about all the highest quality speakers at one time. I'm interested in the L300 only in regards to discussion of the crossover. The LE15A's will not be sold. Now I see the horn in the L300 is different. And the more I read, the more I think that these Apollos should be kept as designed. I doubt if there's any reason to discuss the Nelson Pass crossover. If I was to add the 077's on top I would add a high pass filter for them, and I'm probably months from considering doing that.

So crossovers and woofers are set. That leaves raising the cabinets off the floor (I'll do a trial with milk crates), and surrounds as my primary concerns. Of course any comments are greatly appreciated.

sidney

[Mannermusic]

I've been searching and reading here for over a man day now, and thank you all for the excellent reference material. It seems the woofer in my Apollos was used in about all the highest quality speakers at one time. I'm interested in the L300 only in regards to discussion of the crossover. The LE15A's will not be sold. Now I see the horn in the L300 is different. And the more I read, the more I think that these Apollos should be kept as designed. I doubt if there's any reason to discuss the Nelson Pass crossover. If I was to add the 077's on top I would add a high pass filter for them, and I'm probably months from considering doing that.

So crossovers and woofers are set. That leaves raising the cabinets off the floor (I'll do a trial with milk crates), and surrounds as my primary concerns. Of course any comments are greatly appreciated.

sidney

Glad we could help - let us know how it works out. Those are gorgeous, keeping them original has a special value in that condition.