[capace]

Ok, they may sound a little stupid.  I've built fostex enclosures for the 4.5" 127e, and have enjoyed the sound.

Now I want to do dual 4.5" 127e drivers in each enclosure. The basic question I have is am I'm going to have an phase issues?

I've been wraping my head around it.  Under other situations when using a tweeter and a woofer combo I would either have to time align the drivers if using a 1st order, or use a 2nd order cross over, in order for the sound waves to hit my ear at the same time.

Seeing that this time I would be using two identical(same spl range etc..) drivers, I'm guessing I would simply wire them in parallel(4ohm).

Is that correct? 

I mainly want to do it for the db boost I would get!

[planet10]

You do need to worry about HF combing...

dave

[chrisby]

bipole?

[capace]

I'm not looking to do a bipole. I just want the two drivers vertically placed on the enclosre. So a more traditional deisgn.

[nodiak]

Go for it, especially if you have the drivers already. Try the box laying on it's side too. I did it with 107's before I began worrying about phase/combing issues and enjoyed them.

[JohnR]

You could try rolling off one of the drivers to avoid potential HF combing issues - i.e. a "1.5 way"

[Russell Dawkins]

Unless you already have a box made, you are throwing away a slew of advantages by not going bipole.

One of the biggest bang-for-buck speakers of all time in the consumer world was made by EPI around 1974. It was a bipole with 4 1/2s in a small column about 7" x 7" x 36". It had openings around the base and sounded pretty good for less than $100 a pair, if I remember.

[capace]

Thanks for the info. I'm a little familiar with the benefits of a bipole(of course there are downsides as well), and will probably get into it later. Since I'm fairly new to speaker building concepts in general, I'm mainly interested in gaining a basic foundation on the vented and sealed boxes first. Once I feel comfortable will the those I'll try other designs.

I have several books mainly talking about sealed and vented

I'm using arta, basbox pro,xover, an m-audio sound card, and ecm 8000 to make my measurements and do tests.

It has been really fun!

[planet10]

Unless you already have a box made, you are throwing away a slew of advantages by not going bipole.

One of the biggest bang-for-buck speakers of all time in the consumer world was made by EPI around 1974. It was a bipole with 4 1/2s in a small column about 7" x 7" x 36". It had openings around the base and sounded pretty good for less than $100 a pair, if I remember.

EPI microTowers... a copyof was my 1st "serious" speaker project (& somehow they ended up back here)

dave

[chrisby]

Unless you already have a box made, you are throwing away a slew of advantages by not going bipole.

One of the biggest bang-for-buck speakers of all time in the consumer world was made by EPI around 1974. It was a bipole with 4 1/2s in a small column about 7" x 7" x 36". It had openings around the base and sounded pretty good for less than $100 a pair, if I remember.

ah, the basement on Yates St - if Ron had $10 for every time we played "listen to the music" on those little white towers and Marantz 1030 amp.... well, actually he probably did

Thanks for the info. I'm a little familiar with the benefits of a bipole(of course there are downsides as well), and will probably get into it later. Since I'm fairly new to speaker building concepts in general, I'm mainly interested in gaining a basic foundation on the vented and sealed boxes first. Once I feel comfortable will the those I'll try other designs.

I have several books mainly talking about sealed and vented

I'm using arta, basbox pro,xover, an m-audio sound card, and ecm 8000 to make my measurements and do tests.

It has been really fun!

So how exactly are you familiar with the benefits (and downsides) of bipole? IINM, there are relatively few commercial products on the market using this topology, and most that do include a lot of "conventional"  multi-driver thinking.(i.e. elaborate crossovers, targeting for flattest FR & all those other measurement icons)  If you're basing your opinion on experience with these types of systems in retail demonstrations, it might not be the bipole aspect that's impeding your excitement.

One of the most impressive and musically fun little speakers I can remember hearing at a show over 5years ago (VSAC2003) was the Omega Super 3 bipole (using at the time FE127E - no filters BSC, etc). 

[capace]

I agree bipole does have many merits, but like any speaker design there are always trade off's.

The best technology I think that kind of mixes many technoloiges is tektons new Open baffle hybrid technology. Only live 2 hours away from tekton designs shop, and have heard them on two different occasions. Really very amazing.
 
But since I'm fairly new to speaker design, I want to become familar with one technology and then move on to the next.  It's let complicated that way. At least for me.

[Russell Dawkins]

The Tekton is an intriguing design - I wonder if the pairs of drivers in each enclosure have to be identical, or if it makes any difference. I don't mean different left to right, of course, but if you had two different pairs of drivers, whether you could put the better-sounding pair in front and the inferior pair behind.

Maybe Dave D (planet 10) would have an opinion.

[JLM]

Mounting the 2nd driver on top of the cabinet firing up should help with combing and add ambience.

But another vote for bipole, especially with transmission line (TL) loading.  Unfortunately TL has gotten a bad rap for being difficult to build, but its not true (its no more difficult than adding internal bracing).  My first speaker cabinets were TL kits with two folds each.

[rjbond3rd]

If you are primarily after an  increase in efficiency, you might consider whether the FE126E meets your needs (93db vs. 91db).

[TerryO]

I'm also in the BiPole camp as this solves so many problems in a simple, elegant manner, that it seems foolish to entertain any other topography.

Russell has hit the nail on the head I think, a lot of people believe that conventional MTM box speakers are the way to go, why else would there be so many of them? They certainly solve one problem (lobing) but create others that are just as undesirable and require a high order crossover to actually sound any good at all.

If you install both of your drivers in front, then you either need to actually use a tweeter, crossed over fairly low (a requirement for MTMs, IMHO) which sacrifices the advantages of the small fullrange drivers, or you must use a 1.5 approach, rolling off the 2nd driver at the Baffle Step Frequency with an inductor to avoiding comb filtering.

One last suggestion, build a "test mule" cabinet out of scrap (or even cardboard) with two openings in front and one in the back and try it both ways for yourself by blocking the unused opening. The  cabinet's design would have to account for, and incorporate, two drivers for the bass, which is necessary in either case.

Best Regards,
TerryO

[planet10]

Maybe Dave D (planet 10) would have an opinion.

I have, but a non-disclosure keeps me from saying anything, good or bad. I have a pair here.

dave

[Taterworks]

Doubling up on the 4.5" drivers isn't quite the same as listening to a floor-to-ceiling line array.

In a line array, comb-filtering exists throughout the range of possible vertical listening heights, because you hear driver groups that are appreciably further from you than the driver that you are coplanar with. That added distance from your ear to each of the non-coplanar drivers creates the combing effect in the frequency response.

With only a pair of drivers, however, you can achieve relatively comb-free frequency response if your head is in a horizontal plane that is equidistant from the acoustic centers of the two drivers. The further apart you space the drivers in your enclosure, the more difference you will notice at different listening heights.

If you're fine with the fact that you'll narrow the vertical 'sweet spot' considerably at high frequencies by using two drivers instead of one, then go right ahead. In fact, this can be an important means of reducing room interaction.

Use three or more drivers, though, and all bets are off.

[TerryO]

Doubling up on the 4.5" drivers isn't quite the same as listening to a floor-to-ceiling line array.

In a line array, comb-filtering exists throughout the range of possible vertical listening heights, because you hear driver groups that are appreciably further from you than the driver that you are coplanar with. That added distance from your ear to each of the non-coplanar drivers creates the combing effect in the frequency response.

With only a pair of drivers, however, you can achieve relatively comb-free frequency response if your head is in a horizontal plane that is equidistant from the acoustic centers of the two drivers. The further apart you space the drivers in your enclosure, the more difference you will notice at different listening heights.

If you're fine with the fact that you'll narrow the vertical 'sweet spot' considerably at high frequencies by using two drivers instead of one, then go right ahead. In fact, this can be an important means of reducing room interaction.

Use three or more drivers, though, and all bets are off.

You can certainly hear a two driver comb filter. The fact that you intend to sit exactly in one spot without moving doesn't mean that it doesn't exist. If fact a three driver array would probably be better as the center driver could be at ear level and the other two would have one above and the other below ear level, giving you additional SPLs.

BTW: With you ear equidistant between the two drivers means that above about 4kHz or so, you are in the null of the comb filter and you "may," or "probably will" notice a rolled-off treble.

I've constructed a line array that has...are you ready for this...12 drivers and zero (0) comb filtering at the listening position!

Best Regards,
TerryO

[chrisby]

Doubling up on the 4.5" drivers isn't quite the same as listening to a floor-to-ceiling line array.

In a line array, comb-filtering exists throughout the range of possible vertical listening heights, because you hear driver groups that are appreciably further from you than the driver that you are coplanar with. That added distance from your ear to each of the non-coplanar drivers creates the combing effect in the frequency response.

With only a pair of drivers, however, you can achieve relatively comb-free frequency response if your head is in a horizontal plane that is equidistant from the acoustic centers of the two drivers. The further apart you space the drivers in your enclosure, the more difference you will notice at different listening heights.

If you're fine with the fact that you'll narrow the vertical 'sweet spot' considerably at high frequencies by using two drivers instead of one, then go right ahead. In fact, this can be an important means of reducing room interaction.

Use three or more drivers, though, and all bets are off.

You can certainly hear a two driver comb filter. The fact that you intend to sit exactly in one spot without moving doesn't mean that it doesn't exist. If fact a three driver array would probably be better as the center driver could be at ear level and the other two would have one above and the other below ear level, giving you additional SPLs.

BTW: With you ear equidistant between the two drivers means that above about 4kHz or so, you are in the null of the comb filter and you "may," or "probably will" notice a rolled-off treble.

I've constructed a line array that has...are you ready for this...12 drivers and zero (0) comb filtering at the listening position!

Best Regards,
TerryO

that was the curved array, n'est-ce pas, mon ami?

[TerryO]

Monsewer Chrisby asks,

that was the curved array, n'est-ce pas, mon ami?

That is correct, but you already knew that

Old Reservoir,
TerryO